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Pacific Proa MADNESS is for sale.

The seller says: This boat is a coastal cruiser capable of speeds in excess of 20kts and effortlessly matches or exceeds wind speed in most conditions. MADNESS was professionally built by Chesapeake Light Craft (CLC) and Sea Island Boatworks under the designer John Harris’s supervision. Completed and painted with Awlgrip in 2011. This is the prototype and Hull #1 for CLC’s line of Pacific Proa kits.

The seller says: MADNESS is capable of amazing speeds yet provides a comfortable smooth ride in most conditions. Operation is simple and easy to learn, I’m new to sailing and have no problem single-handing the boat.

The seller states: a custom Forte carbon mast was added in 2022, and new Evolution main and head sail(s) were added in 2024. Interior is painted only and larger than apparent from outside, however internal space is tight. There is bunk space for 3, and a space for a chemical head.

The boat is currently in the water and ready to sail in Norfolk, VA, or to be loaded on its custom trailer for transport. All accessories are included in the purchase, to include:

Custom trailer with components allowing launch and recovery from standard boat ramp, strong running Yamaha 4HP outboard motor, new Evolution main and head sail and original storm sail, spinnaker, and jib, anchor w/ chain and Rhode, covers for cockpit, motor, main & head sail, spray skirts, lifejackets, dock lines and fenders, etc.

LOA: 31’
Beam: 14’ keel to keel
Beam overall: 20’ assembled
Weight: 1400 lbs fully assembled

Follow the links for more information:
CLC Boats
YouTube, YouTube and more YouTube.

It’s been almost a month since QB (Questing Beast) and I ventured out on this year’s Texas 200; now that I’ve caught up with some of the other things in life it’s time to say something about the adventure from a proa perspective, I’d already written something for the Texas 200 website.

First off we only made the first 68 miles of the planned 153 miles. No fault of QB’s it was strictly operator error. First I tried to turn to port at about 5 mph with a clump of sea grass on the rudder which I thought I had shed and popped the cassette and rudder out of socket and cross ways across the stern of the boat. The only damage was to the carbon fiber pushrod which was bent over the gunwale.  The cassette/rudder assembly popped back into place easily and there was no apparent damage other than the pushrod. I was leery of using the rudder with the damaged pushrod and started sailing using the AD scull to steer which led to my second mistake.  While getting a feel for how the boat handled using the scull to steer I failed to realize we had entered the land cut and was shortly in the shoals on the lee side of the channel in a freshening breeze. I decided to spend the night there and leave at first light to catch up with the fleet.

The second day while we were slowly catching up the sails ahead of us we were caught by a wind shift that put us once again in the lee shoals of the land cut in a freshening breeze where we spent the rest of the day and night. After that it was a case of continuing to Corpus Christi and meeting family a day late at Snoopy’s restaurant to return to everyday life.

Along the way QB weathered a popup thunderstorm the first day that capsized a couple of boats and drove some others ashore. The only issue there was the drogue I first deployed and the anchor afterwards both held the boat at about 45 degrees to the wave trains rather than closer to head on. In both cases lines were fastened to a horn cleat on the side of the cabin within reach of the cockpit. Some sort of bridle arrangement is probably going to be required.

Before that in the snail race up the Laguna Madre in very light ghosting conditions before the storm we were a “fast snail” and overtook two boats in a ten mile stretch while none of the sails behind us seemed to be gaining.

The second day through the land cut and across Baffin Bay we started with full sail and took in one reef once in Baffin Bay and then another an hour or so later. Later in the afternoon once whitecaps were showing regularly we took in two more reefs and sailed on at 7-8 mph. The maximum speed the gps recorded was 9.1 mph which is slow in one respect but I was being very conservative on a first time out in open water.

General impression is that QB is definitely fulfilling its design requirements as a comfortable quick camp cruiser. It’s certainly comfortable, a silicone gel seat pad is a significant element in overall long term comfort for an 80+ year old butt. A lot of time was spent with weight as far to leeward as possible sitting on the seat pad on the food box to minimize wetted surface.

The to-do list is fairly short and is in the queue behind the list my wife patiently accumulated while I spent so much time getting the boat ready. First and foremost is just more sailing time to learn how the boat handles and to optimize the sail rigging. The side planks on the aluminum tube beams need to be either redone or replaced, they need to be stiffer and stronger. Planks were made from available material while I was waiting for backordered foam and were a minimalist approach ~ 3# each. New reinforced reef ratchet assemblies need to be made, one failed a week before the 200 and reefing was done through tied grommets at each batten location. The winch handle clipped into the end of boom worked well to reel in the sail.

I’ll probably switch to a cable system for rudder control rather than pushrod. Not because one pushrod was broken but there’s a conflict between the tiller arm and a cleat for the shock cord that helps hold the AD scull in place. I’d like to have a lighter AD scull with a slightly more flexible blade but probably not bad enough to actually make one. The existing scull works really well I can easily scull QB at 2 mph for an extended time and might be able to improve on that with practice.
The one problem with the scull that I hadn’t anticipated in the scull is worthless in shoal water. Works great in two and a half to three feet of water, very problematical in shallower water.

There’s a pinhole leak in the float, takes in about an eighth of an inch (3mm) a day not sure how I’m going to find and fix it, probably fill the float partially up and go from there.

Trailering cover need to have 3/16” shock cord rim switched to 1/4” the front edge starts to lift at about 60-70 mph on the highway. No rush on this one we are two miles or six minutes from our usual ramp. Trailer light needs to be replaced also when one screw holding angle bracket holding the light sheared off and shook light to pieces.

That’s it for now, it was a great trip, bucket list item for an old man. Now it’s just a matter of something to piddle with for a while.

Cheers,
Skip

A review of traditional Pacific canoes is followed by a report on the modern revival of canoe building in Oceania. This is followed by a thorough presentation of the various proa options available to modern inventors, such as rig types, hull shapes, leeway prevention, stability, seaworthiness and rudders.

The Modern Proas section includes 16 entries, including new interviews with such proa luminaries as Russell Brown, John C. Harris, Rob Denney and many more. There is the welcome inclusion of proa efforts from around the world, including France, Germany, Australia and Oceania, and the Caribbean.

This is followed by a chapter on proas in the racing scene of the 1970’s and ’80’s, including the famous CHEERS by Richard C. Newick. And finally, some modern speed record proas such as Vestas Sailrocket 2.

While by no means exhaustive, The Proa covers a good deal of the territory of an admittedly large and growing field of interest. Available at Amazon.

Low-res images notwithstanding, we see a copy (more or less), of a traditional Pacific proa such as the Fijian ndrua or Samoan alia. However the streamlined “pod” shape of the akas (cross beams) certainly are not. Is this indeed a proa and not some agricultural implement common to the region that we are anthroproamorphizing? See what I did there?

Does anyone have more info on this strange, proa-like google image? I am extremely tempted to go investigate, since I am no doubt the nearest proanut to Yelm.

Much thanks to Fulgencio G. for the submission!

X marks the spot.

Much thanks to Henrik Richter-Alten for the submission.

At 0:45 we get a few seconds of an unnamed cruising proa. It appears to be an Atlantic type, sloop rigged. Does anyone have any more info on the mystery vessel?

Much thanks to Othmar K. for the submission.

Update 2/22/24: Paul’s sleuthing has accomplished both the name and the owner of the mystery proa. This was the 47’ Orca, designed and built by Michel Fortin, 23, for the singlehanded trans-Atlantic race, but was not completed in time. I’ve included the newspaper stories in the gallery above. My apologies for the poor formatting. Much thanks to Paul D. for solving the riddle!

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QB Design and Construction Report

By Skip Johnson

QB aka “Questing Beast” from T H White’s The Once and Future King. Questing Beast is a nigh on perfect name to describe the fool’s errand I’ve traveled for some time now.  Unfortunately the phrase doesn’t roll off the tongue smoothly so QB it is. Parenthetically a version of the phrase worked perfectly for my attempt decades ago to build a sub ten pound sit on top, stick and frame with clear winter window shrink film skin. Leastie Beastie was a twelve pound unique marvel until the UV rather quickly destroyed the skin.

QB is a 21’ proa schooner with cambered panel staysails and end mounted rudders. Construction is foam and glass, foam is primarily ½ inch, 5 PCF (pounds per cubic foot) Gpet foam (10 sheets) with one sheet of 12mm Corecell M80 for bottom panels and some scraps of 12mm Corecell M200 bought from fallguy over at Boatdesign.net. Fiberglass is primarily 9 oz tooling cloth with 12 oz biaxial taping and some 22 oz unidirectional tape spot reinforcement. The 9 oz tooling cloth was a mistake; I should have used 12 oz biaxial throughout. The tooling cloth worked fine when vacuum bagged but contact wet out usually required some remediation no matter how careful I was. And the stuff was terrible for shedding where cloth was cut. Virtually all fiberglass work was topped off with a layer of peel ply.

Design weight light is 320 lb which now seems possible, hull weighed 170 lb prior to painting, float is also slightly under the estimated weight but still needs some remediation and fairing.

Other random notes about the boat. Float is based on a Speer P30012 section stretched to about a 7.5% section. Rudders are straight P30012 section. Sliding beams are 3” x 1/8” wall 6061 aluminum tube sliding in HDPE bushings. Masts are sectional step tapered aluminum flagpoles 3” diameter base, 2” diameter cap. Sails are 4 oz Dacron with a leading edge luff of seat belt webbing. Battens are 3/8” c.f. tubing. Auxiliary power is an A.D. style scull with fiberglass blade and aluminum tubing shaft. A number of bits; navigation lights, ball and socket set for scull and ratchet mechanisms for roll up sail reefing are 3D printed pieces.

The Construction Process

See photos above

1. A 1:12 size model in corrugated cardboard. Illustration board, the old gold standard isn’t readily available here in the hills of Oklahoma.
2. Surprisingly the model weighed in matching the design displacement. The mannequin however was seriously underweight hence the bolt style pfd. Not really visible in the photo is a chunk of XPS foam on the lee side of hull with the same scale volume as a 9” diameter 60” long inflatable beach roller/fender.
3. Layout table under construction. Three H.C. door panels 36"x 80” with a supporting lightweight framework. Table weighs around 100 lb and is easy to set at different heights depending on needs of an old man that tries to avoid much bending over.
4. Assembly. Hull sides are 24” wide panels 20’ long. Bottom plank is a parabolic curve with an exponent of 5. Sheer is a more rational 3. The prismatic coefficient is 0.76. The split piece of lightweight pvc pipe was trough to wet out ½” unidirectional tape along gunnels held in place by wood strip covered with packing tape.
5. Bulkheads, berth flats and ring frames installed. Trammeling from several different points hull seems to be symmetrical within an 1/8” or so.
6. Hull has been flipped over and the bottom glassed, lapped over the bottom to just over the waterline for an 18 oz bottom. While still upside down the bottom was coated with a thick graphite/epoxy bottom coat.
7. Assembly continues. Hull now in a cradle with rollers so boat can be moved around a bit. The 2x4 frame on leeward side makes it easy to tilt the boat over for easier access to inside and the underside of seating pod.
8. Shunting day. Until now it’s been advantageous to work with weather pod towards the right side of shop. Eventually the boat will need to go on the trailer with weather pod to the other side (passenger’s side of vehicle). Power boat has been pulled out and move was easy on roller equipped cradle.
9. Back in the shop.
10. Boat is now off the rollered cradle and sitting on 2 2x4’s at about where the sliding beams will be, boat rolled over on side for better access to interior and underside of seating pod.
11. Interior is painted Gripper primer and polyurethane porch enamel. Horizontal surfaces get an extra coat with non slip additive.
12. Current state, deck with a coat of primer.

Main Hull Construction Sequence - Part 2

See photos above.

• Side/seat joints filled, glassed, rounded, glassed.
• Centre section bulkheads extended upwards to support a foredeck which is needed to support each mast.
• Seat back panels modeled with a skeleton structure of plastic conduit pipe.
• Panels made of 25mm foam and glassed.
• Panels laid on seats and lashed together with cable ties and hot glue.
• Joints filled, glassed, rounded and glassed.
• Foredeck foam cambered while it only has the lower layer of glass.
• Gunwale foam applied with hot glue, edge set as it went on.
• Rudder shaft boxes formed of foam and glassed in.
• Leeboard mounting reinforcements foam and glass.
• Leeboard construction has outer skins plus shear webs and foam within, plus hard filler round the bolt.
• Flat leeward side with foam on top.
• Internal shear webs over foam strips.
• Glass and filler.
• Final glass and flow coat.
• Install with cheek plate.
• The float hull was a half scale version of the main hull, and I did it first. Closing the deck panel on to the open hull is tricky as you cannot access the internal joint. I made 25mm square section strips of light rigid foam, rounded one corner and laid strips of wet glass over two faces of the strips. This messy structure was clamped to the inside of the top of the side panels by many bits of sliced plastic pipe. When it set it made a shelf on which to glue the top deck, and then round and glass the outer surface.
• This is the GRP bracket which connects with the float hull, showing a trial fitting before the decks went on. The central bulkheads and reinforcing can be seen.
• The float looks less boxy when sanded and flow coated.
• The noses were much the same construction and the attachment bolts were glassed in. Each nose has an inspection hatch and a drain plug, as any supposedly watertight compartment must have. They have the extreme ends as 75mm of solid foam with a thin coat of glass, as a sacrificial bumper.

The leeboard has quite high stresses, with the central bolt in tension and the water force pushing the board against a plastic strip fastened to the chine. To lift the float hull plus 100kg of ballast water plus the crew sitting in the ww side of the main hull, the board needs to be generating about 3kN of force, about 300kg. This means there will be about a ton of tension in the bolt which needs to be dissipated through the panels.

It seems to work, because in a gust I have lifted the float without breaking anything.

Tricast 5 has a very smooth surface which allows a pretty good finish as long as roving or cloth are laid on chopped strand mat while still wet. If CSM is laminated and allowed to set, the finish is rough.

I bought a full face mask (JSP Powercap Active) with an integral fan, battery and filter as I was making a lot of toxic dust. I have no connection to the company but it was light, effortless to wear, good field of vision, no condensation and very reassuring in a dusty environment. It was expensive at £340 but worthwhile.

Summary

I do think the radiused joints open up possibilities to people used to plywood construction.

When I was young, plywood boats used to have chine logs and stringers held in shape by elaborate temporary or permanent frames. Builders went to great pains to get clear long pieces of timber to make these but in fact, all they were were glue chocks. At the time this was much lighter than traditional clinker or carvel. It took several inventive steps to get to true monocoque with stitch and glue, such as the Mirror dinghy.

Schacht designs are very attractive because the designer has paid attention to the aesthetics. Sheer, rocker and flare do make an attractive boat. My boat offends the eye in a number of ways apart from being a proa, but I was persuaded that Rob Denney has correctly worked out that rocker, flare and sheer are not in fact productive in a long thin sealed hull.

Sheer and flare keep an open hull dry but if sealed, one can accept the ends submerging as long as they re-emerge. The straight profile makes it pretty easy to form the shape. It also damps out pitch, making the sails more efficient and the motion easier.

I’d say anything which can be made of plywood could also be made of foam/glass without the maintenance problem, with a clean smooth interior and integral buoyancy. The sealed tank ventilation/rot problem in ply boats is also solved. The downside is the materials are less pleasant to work with, and need precautions.

Even if all its compartments were flooded, SGIAN GHLAS would always have over 500kg of buoyancy from roughly 10 sq m of 15mm foam and 15 sq m of 25mm foam. Even if it is upside down it will float!

24’ Proa Construction Details

By Topher Dawson

Urethane foam core (Tricast 5) or other cores, with glass and polyester resin, makes for a strong, stiff and light panel. Nomex, carbon and epoxy would be stronger, stiffer and lighter but this boat does not need all that and the cost is eye watering.

This boat is made of flat or slightly curved panels with radiused joints. Harryproas are too, but using vacuum infusion and more expensive materials they achieve a better strength to weight ratio. My view is that if a hollowed out tree trunk can make a fast proa, we do not need carbon or epoxy.

Structurally the hulls of this boat are monocoque, with all the strength, stiffness and impact resistance coming from the panels. There are no keels, frames or stringers. The joints are radiused full strength joints, with the same cored construction as the panels. The large radii smooth the flow a bit and are less draggy than sharp corners.

The panels allow a simple hull shape to be set up without moulds, using just temporary braces and hot glue. It’s quite a lot like traditional boat building except you can make your planks any size, stiffness and strength. In fact any plywood design could be made this way, and it would not biodegrade. It opens possibilities for one-off construction which conventional GRP moulding does not.

Sequence of construction for the main hull

See photos above.

• Make a flat table 24ft x 2ft out of MDF and coat it with a sacrificial film.
• Lay out three panels of 25mm foam 8ft by 2ft and hot glue them together with butt joints.
• Using a flexible batten of plastic conduit pipe, draw the tapering curves at each end and cut. Photo 1
• Glass the top surface with 400gsm chopped strand mat and 400gsm woven roving. Photo 2
• Lay this panel to one side (with glass only on one side it is floppy and weak).
• Make two side panels the same way.
• Make two pairs of bulkheads the same way. Drill bolt holes with big holes in the foam filled with hard filler to take bolt compression. (The noses will come off by bolting these together). Photo 3
• Hot glue and brace the bulkheads with 3mm packers between each pair so a saw can get between them. Photo 4
• Set up the sides vertical and straight. The bottom edges of the sides are raised off the table 25mm with scrap foam so only the extreme edges of the sides and bottom touch. Temporary bulkhead amidships to keep the max beam.
• Spot glue with hot glue and brace upright. Photo 5
• Make radiused filler and glass joints on all inside corners.
• Now the hull is stiff enough to cut the noses off between the bulkheads. Noses stored for later. Photo 6
• Main hull is now turned over and the external corners I.e. chines, rounded and glassed. Photo 7
• Bulkhead/side and bulkhead/bottom joints are also rounded and glassed. This means that the glass of both inner and outer skins rounds the corner of the side/bulkhead or bottom/ bulkhead and is gripped by the bolts holding the two bulkheads together. Photos 8, 9, 10, 11
• Hull turned right way up and the seat panels are now made and hot glued in place. Photo 12

Part 2 coming soon.

At first glance I thought it was the second silliest proa design I’d ever seen! Like someone had accidentally beached their dory on the back of a small submarine or a Narwhal? However, Topher Dawson is perfectly serious about his new proa, and as I studied the odd craft and read his reasoning for it, I found myself nodding along. Mr. Dawson’s take on the “western” Pacific proa is original, creative and thought provoking. I hope you enjoy hearing about it as much as I did. -Editor

24ft Proa Design Considerations

By Topher Dawson

Proas have always fascinated me, because they represent a completely separate concept of how to make a sailing boat from anything we have in the west. Readers of this site will know what a proa is, but I want to examine the design choices open to us.

The Micronesian proa is a long, thin, fairly heavy canoe made from a dugout log with or without additional planks or strakes. It gets its stability from the weight of a single outrigged log or hull which is flexibly mounted to windward. The rig is fairly small by western racing standards, and the craft gets its speed from being very easily driven. The load is carried in the main hull although crew sometimes hike out to windward. The stresses in the connecting structure are fairly low, and can be taken by the timber and natural fibre lashings.

A western designer is likely to depart from this concept but needs to know why. Some designers have perhaps gone too far and in the process lost some of the best features of the proa. I will refer back to the traditional proa later.

After many years and proa models I decided to really make one, and settled on the biggest proa daysailor I could reasonably load on a trailer.

Using polyester roofing resin for cheapness and urethane foam as a core has turned out a pretty light (250kg without ballast or crew) and a very strong and stiff boat. The proa concept works without getting manic about lightness.

To get the trailing length down to about 18ft I made the noses come off. They stow within the middle part of the hull and are fairly easy to lift. They bolt on with 4 x10mm stainless bolts embedded in the nose bulkhead which come through holes in the middle hull section bulkhead.

The main hull is 24ft long and 2ft wide at the waterline, so 12:1 length to beam. At this narrow ratio it does not seem to matter much what the cross section is, so I opted for a flat bottom and vertical sides with heavily radiused chines. Rob Denney’s Harryproas do this and don’t seem to suffer. It allows the bottom to be heavily made on its bottom surface, to withstand the ground, and the top surface, to make a durable floor without extra structure. As with Harryproas there is nearly no rocker, just about 80mm in the last meter of the ends.

Proa crews in Micronesia sit in the main hull bailing furiously or on the deck structure. This may be OK in Micronesia but not here in Scotland where hypothermia would set in fairly quickly. I’ve also found a flat deck multihull pretty uncomfortable as I’ve never mastered squatting.

So the plan needed a comfortable and sheltered place for sitting. Using the center section of the canoe hull as a foot well, I drew a flat seat extending outwards and sloping slightly downwards from the top of the hull side, and then a sloping seat back rising up. Extended to the ends of the cockpit this forms a double ended dory type hull with a forwards flaring “bow” at each end. It looks nice, throws the spray outwards, and keeps me warm and sheltered.

Submarines steaming along on the surface have their noses under water with a transition to dry decks about a third of the way aft. I figured I did not mind the noses, which are sealed boxes, having water over their decks sometimes, as long as the cockpit remained dry.

Proas tend to have a nose down attitude due to the rig thrust being high up. In this boat the crew weight aft will help but I wanted a lot of spare buoyancy in the noses to prevent nose dives. They displace about 450 kg each fully immersed, which is about the loaded displacement of the whole boat. Empty, the proa floats with about 100mm draft in the main hull, and if the 100kg ballast water is in the outrigger it draws about 125mm. When laden with two crew the main hull draws about 150mm but could carry a lot more.

I did not want torsion forces in the deck beams so they meet at a point above the outrigger. They meet the open center section of the boat at its end bulkheads so in fact they protect it against torsion.

A GRP bracket is bolted to the outrigger junction which has two strong cheeks going down into pockets inside the hull skins of the outrigger. This area of the outrigger hull is heavily reinforced with bulkheads and glass. There is a 50mm diameter heavy wall stainless tube axle which passes through hull sides and cheeks, allowing the hull to pitch freely. If this starts to scare me by trying to nose dive in waves I will add soft rubber blocks as limit stops. Effectively this is what traditional proas achieve with bendy ends to deck beams.

So far it has worked well, with the float hull conforming well to waves without jarring the rest of the boat.

The masts, deck beams and rudder shaft are all aluminum scaffold tubes, 48.3mm diameter, 4.47mm wall. They are of an alloy which rests salt water and is forgiving of surface abrasion unlike thinner wall tube.

The masts cannot on their own withstand the bending moment needed to lift the outrigger with 100kg of water, so there are single Dyneema stays to windward for each mast.

The rig is simple, small and low, being two identical lug sails of 100 sq ft each, recut from a single heavy mainsail. They each have two sheets, one to a block at the end of the nose and one to a block amidships. Each has a two part tackle, so there is a lot of loose rope in the boat. They set well as long as the luff is sufficiently tensioned.

The rudders are a complex issue as many proa builders have discovered. Traditionally, proas are steered by a helmsman with a large bladed steering paddle. He (I have never seen a picture of a woman steering a sailing proa) sits right aft and jams the shaft of the paddle against the lee side of the hull. Thus he can generate the force needed to counter the weather helm. He is in a welter of spray which is not really practical in Scotland.

There seem to me to be three rudder choices available. One is to mount the rudders as trim tabs on the aft edge of a daggerboard in a case, like Brown and Newick. This does work but the idea of bashing the leading board at speed on a rock with its vulnerable rudder blade, or jamming the aft one in its case or breaking the case, worries me. Another is to use two rudders in the water all the time like Harryproas. This either means rotating both rudders 180 degrees at each shunt, or accepting that leading and trailing edges will swap and working out how to stop the leading rudder flipping over as its axis will be aft of the center of pressure. The third is to do what the Micronesians do and raise the rudder out of the water at one end, and lower a rudder at the other end. This gets the leading rudder out of danger and allows the rudder design to be optimized for one way flow. I also made the choice to keep all the foils outside the hull, so there are no cases to leak or break. All three foils can be retracted above the level of the hull bottom so the boat can sit flat on a beach. All three foils kick up without damage if they strike an object.

In this boat the rudders are large cored glass/foam blades laminated on to aluminum tube shafts. The rudder section is asymmetric with a flat surface on the leeward side and balanced with about 25% of the area forward of the shaft centerline. In this way they can develop a windward force without too much tiller load.

Every time we shunt, one rudder has to come up and the other has to go down. The shafts enter the cockpit through a hole at seat level. When deployed they are at 45 degrees to the vertical, with the top ends passing through the tiller and extending up another foot or so. This end is then lashed aft to keep the bottom end pulled forward into a GRP hook at the waterline. The hook holds a plastic bush which the shaft turns in, with another bush at deck level.

When raised, a lanyard attached to the aft top corner of the blade hoists the blade up and forwards, till the shaft lies along the seat edge and the blade is stowed close to the cockpit nose.

The design choices for proa leeway prevention are either use the hull shape like the traditional proa, use two foils, I.e. two rudders or dagger boards containing rudders, or three foils i.e. two rudders and a centerboard or leeboard.

I don’t want the hull to be developing lift to windward, as it would be an inefficient foil. Ideally I would like it to go straight without leeway as this would incur the lowest drag. To do this the leeboard needs to develop enough lift at zero angle of attack. Speer’s P3 section can develop a lift coefficient of about 0.5 at zero AoA but I don’t know what my sharp edged version is managing.

My 1/8 scale model showed that the three foil solution with the forward rudder retracted could be made to work. The leeboard can rotate fore and aft around its bolt 180 degrees, from fully retracted in one direction to fully retracted in the other. It is actuated by two four part purchases hauling on Dyneema lines wrapped around the upper edge of the board, one in each direction. The tackle line is endless and runs inside the cockpit where it can be grabbed at any point.

The leeboard is also inclined with its tip to windward at about 25 degrees. The purpose of this is to make it lose its grip on the water if the angle of heel should ever reach 45 degrees, i.e. halfway to a real capsize. At this point in a capsize the cockpit side would be immersed and buoyant, and there is a chance that the boat could recover or at least give me time to release sheets.

Traditional proas have a weather helm problem. The main hull is shaped to be more convex on the windward side and flatter on the leeward side, thus making a better shape to generate lift to windward. But the center of lateral resistance will be well forward of midships and the only way to keep the weather helm within bounds is to mount the oceanic lateen rig right forward, with the mast tilted forward. This works well but needs a skilled crew to detach the whole rig from the bow and walk it aft to the new bow at every shunt, tipping the mast over at the same time.

To windward the proa can be made to balance for long periods without steering input, but on a reach and downwind the weather helm needs constant force on the steering paddle.

Like most western sailors I draw the line at carrying the rig to and fro, and have opted for two masts fixed at equal distances from midships. As the sail centers of effort must be slightly aft of their mast to weathercock safely, this means the overall rig center of effort must be slightly aft of midships. Model experiments showed that with the leeboard vertical, the boat needed about 5 degrees of rudder to go to windward, and it steered itself. 5 degrees is optimal for a good lift/drag performance and as the blades are pretty balanced the tiller load is light.

Off the wind, the weather helm builds up, but can be balanced out by raking the leeboard aft. The boat seems to be pretty good at self-steering but not on a broad reach or running downwind.

The leeboard gets flow in both directions so it is an approximation to a Speer P3 section but with sharp edges. I accepted early stall in return for not having a draggy blunt trailing edge. Early stall can be experienced in low winds when starting from rest after a shunt. The boat falls away from the wind as the board loses lift. But it fairly soon recovers as the speed increases.

SGIAN GHLAS Specifications

LOA = 7.5m/24ft
Length without bow noses = 5.5m
Length of ama (float) = 3.75m
Main hull WL beam = 600mm/2ft
BOA = 5m
Draft empty main hull = 100mm
Draft main hull with 2 crew = 150mm
Draft empty ama hull (30kg + 20kg crossbeams) = 70mm
Draft loaded ama with 100kg ballast water = 150mm (50% displacement)
Sail Area 18.5 sq m/200 sq ft
Weight (estimated from draft) = 280kg/617lb without ballast or crew

Video

Sgian Ghlas light wind sail
Sgian Ghlas sailing at Toberonochy

Coming up next: Building the Grey Knife

Length: 38’/11.6m
Beam: 18’/5.5m
Displacement: 5512 lb./2500 kg
Launched: 1984
Overall condition: Excellent and ready to go.
Notable voyages: Chilean Patagonia, Chiloe Island, Fjords several times.
Electronics: Chartplotter Raymarine, GPS, Wind, etc.
Solar Panel
Danforth Anchor 40lb.
Includes trailer
Asking: $42,000 US.

See Sailboat Listings for more info.

RB proas don’t come up very often, so if you want to follow Ryan Finn around the Horn, now’s your chance.

But first, Rob’s disclaimer: “I am no aerodynamicist and have no access to CFD or XFoil or model/empirical testing. It is mostly gut feel and intuition. A classic situation of a little knowledge being dangerous!”

Biplane Aircraft

There are any number of wind tunnel studies which demonstrate that a monoplane is more efficient than a biplane for the same overall wing area. Principally because of less pressure differential between the two adjacent wing surfaces and because a monoplane has only two wing tip drag losses with each half wing fuselage end-plated. Whereas a biplane has four wing tip drag losses and only each half of the lower wing (ie only half the overall wing area) fuselage end-plated.

Biplane basics

The same studies also show that there is unequal lift distribution between biplane wings of equal area. The upper wing produces somewhat more, whist the lower wing produces significantly less, despite having fuselage endplates.

We all can see this effect on the water as well, two similar or one design boats sailing close to each other upwind, the leeward one (upper wing) always has the advantage on the windward boat (lower wing). How much depends on the distance between the two and the relative (stagger) angle between them. If the leeward boat is too far aft of abeam, there is no effect, actually slower because of the disturbed and deflected wind shadow of the windward boat. Too far forward of the windward boat, and the effect disappears.

At the end of the biplane era, aircraft designers optimized this by making the top wing larger and the lower wing as small as possible, minimizing its lift loss whilst still providing lift benefit to the larger upper wing. These planes were called sesquiplanes, and were recognized as being the fastest/most efficient of the time. There are other modifying factors, some are explained later.

Left: Nieuport Delage NiD 44 Right: Nieuport-Delage NiD 52

Differences Between Sails and Aircraft Wings

But perhaps a pair of yacht sails interacting together behave differently? Each sail is not identical in size, plan form or chord characteristics, the angle and distance between them usually varies, some converge to almost touching at the heads and most importantly, because they operate vertically, they experience different airflow strength and direction top to bottom along their length, whereas in aviation, they operate horizontally in pretty much constant airflow strength and direction for their entire length. Most sailing rigs have a significant amount of twist along their length (ie height), you don’t see any twist in aircraft rigs. And perhaps because of all this, there are some, who should know, like North Sails, say that two sails, working in combination will produce more lift than the same two sails completely separately.

“If the jib and main are working as seperate elements and not as one wing, that again reduces the efficiency and increases the drag of the whole package.”

— Julian Bethwaite, 1 February 2023. Post 898

Certainly, two sails generally have more luff length and therefore greater “beneficial” drive for the same area than a monoplane/una rig. If a jib sheds its head vortex into the upper mainsail, then there is ultimately only one tip vortex for the two sail combination. Plus directing additional air towards the upper mainsail, which operates in freer, stronger and steadier airflow.

Biplane Rig Types

All two-sailed rigs are biplanes, but with differing characteristics depending on the stagger or relationship to each other, the distance between them, their sail area distribution and profile.

Upwind, Sloop rigs have a large (positive) stagger angle. Fore and aft schooner rigs have the largest positive stagger angle but the narrowest gap, with an adverse effect on lift due to shadowing on the aft sail. Perhaps, because of this, it is a large negative stagger angle? Again, on the water, you would never choose to sail close behind another boat.

Sloop rigs, are also mostly sesqui rigs, in that their sail areas aren’t equal in distribution or profile. But they have it the wrong way round, the jib (upper wing) being smaller than the mainsail (lower wing).

The angles of attack upwind (AoA) on a sloop rig are fairly fixed, the (smaller) foresail being ~10-15 degrees from boat centreline, with the (larger) mainsail being ~0-5 degrees.  With a biplane rig, the respective AoA’s are not so interdependent. On Sidecar, (light wind- medium wind) the jib is ~15-10 degrees and the mainsail is ~10-15 degrees. So the larger sail benefits from a more favourable sheeting angle for the same apparent wind angle, as well as the gain of being the “upper wing”.

Sidecar’s rig has virtually no stagger, a wide gap, and is a true sesqui, that is, it has a larger leeward (upper wing) mainsail and a smaller windward (lower wing) jib and therefore should derive greater beneficial interaction. On a sloop rig, the smaller jib is usually end-plated, on Sidecar it is the larger mainsail which perhaps could further increase any theoretical gain.

As these rigs come off the wind, the stagger angle reduces, until the stagger is sufficiently negative for there to be lift loss due to shadowing. A fore and aft schooner rig improves lift initially (due to reducing aft sail shadowing) and then loses lift again later. Sidecar’s rig loses sesqui benefit soonest, due to less stagger, but unlike the others, there comes a point, where, sufficiently off the wind, the rig regains positive stagger (ie when at least the upper leech of the jib is to leeward of the mainsail) and behaves like a sloop rig upwind. All side by side biplane schooner rigs have this similar characteristic.

Sidecar’s area distribution and profile of windward jib and leeward mainsail couldn’t possibly be optimal on first try. I can now see how to also end plate the windward jib. The area distribution and stagger between the two sails could be improved. There still is a lot still to play around with because I am dealing with two entirely different sails, with variable positioning, not identical ones on masts fixed side by side.

It really needs a methodical study, using CFD or Xfoil on many options, but that is beyond my pay grade and ability.

Notes

Any sloop or conventional schooner rig on a multihull with sufficient weather shroud angle can be “adapted” to a biplane rig when conditions suit. Use or borrow an old jib of appropriate geometry, and tack it somewhere near the front cross beam, sheeted somehow off the aft cross beam.  More sail area for very little increase in heeling moment, and possibly some biplane/sesqui effect, especially on long legs. Cumbersome to tack and gybe though.

As an aside, another interesting possibility is an overlapping schooner rig. The conventional schooner rig isn’t particularly efficient upwind, for the reasons given earlier, but if there was sufficient overlap between the two (because you can on a proa) perhaps you can make the two mainsails interact in a more beneficial way? You would also get some pitching benefit, because the two masts would be more central, and out of the ends. But you would still have a proa shunting problem in that when shortening sail, you would have to shorten both, otherwise you would be hoisting one and shortening the other with each shunt.”

And finally, tongue in cheek, roll this recent experimental jet plane through 90 degrees, and you almost have two mirrored Sidecar rigs:

Links

Sesquiplanes
Boeing Truss-Braced Wing
North Sails Blue Paper: How Sails Work
Biplane and Triplane Wing Lift and Efficiency

Designed and built by Tony Bigras in 2008, the 16’ pocket yacht carried Tony on an epic 6000 mile cruise down the Pacific coast of Mexico, Central America and the Caribbean. Read the captain’s log here: Travels with Miss Cindy.

Miss Cindy features a very cool rig: a biplane lug. The rig is similar to that on Paradox, with roller-reefing lugsails in a biplane configuration.

Built of stitch and glue marine plywood, epoxy and fiberglass, the build is well documented in the Construction Log.

She was extensively repaired, renovated and upgraded in 2022. Wind vane self steering was added.

Update 4/1/23: Price drop from $5000 to $3500!

Update 5/27/23: Miss Cindy is sold.

Comparative Analysis

Most sailors regard proas as weird and freakish, and a few, the most wonderful thing in sailing. Proas have a mythical fantasy status, but they are just another form of multihull with their own particular advantages, disadvantages and compromises. Most modern proas tend to be updated copies of the traditional types or incorporate features that are far from the norm, so most of the multihull community can’t or won’t relate to them.

And then there has been the totally self defeating debate about which proa type is ‘best’ to add to the general bemusement of the wider sailing community.

It has always been hard to compare how proas relate in terms of performance to other multihulls, because there has been virtually no close up sailing interaction. Proas need to be sailed or raced extensively against the other multihulls and evolve just like other multihulls have, before they can be understood and find an accepted place in multihull society.

So how else to compare different proas with each other and other multihulls without sailing against each other or preparing complex, costly, detailed VPP analysis when there are so many aspects upon which there is little or no performance data on proas, and especially their rigs?

Base Speed

The multihull racing community decided a long time ago that there was no real way of differentiating between the different multihull types, so multihull handicap ratings are largely based on the three fundamental properties of all sailing craft, ie: Effective sailing length, sail area and displacement.

Sidecar’s unmeasured/predicted Offshore Multihull Rule (OMR) rating, single handed is likely to be around 0.861 white sails only, few would understand what that meant relatively speaking, apart from a few keen OMR racers, and even then they only know and can easily compare OMR’s with downwind sails included.

Base Speed is more easily relatable to the wider sailing community.

MOCRA, OMR and Texel rating systems all use fairly similar formulae based on these measured factors to derive an average or “Base Speed”, which is then converted into a time correction factor.

A spread sheet can be set up, inputting the three factors, and calculate the Base Speed and any other ratio you may be interested in, such as Displacement/Length and Sail Area/ Displ or Bruce Number.

Likely top speed will be double Base Speed, and Base Speed also approximates likely top speed upwind in flat water.

Indicative table above based on single handed crew where possible. Best to use white sails only, downwind sails will distort the Base Speed. Try to compare like for like and beware designer optimism and sales talk. If possible get (measured) data on other multihulls from rating websites.

Playing around with these basic parameters on any given boat can also be instructive.

Overlays

For those with CAD drafting ability, another tool is to use images of yachts or aspects you are interested in, rescaled to suit, inserted under your design or a trace of another design for comparison. Areas and centers of effort and lateral resistance can also be added.

If you overlay one design over another properly, to scale, you can compare headroom, freeboard, amas and rigs. Interesting to see for example that the the general rocker lines for Jester, Madness, Seacart 30, many Farrier tris and Sidecar are remarkably similar in character, especially the front half. All arrived at independently without reference to one another. Compare Sidecar’s ama with that of a Seacart 30, and then remember that the Seacart 30 has two of them, and you begin to understand that the weight efficiency of proas is also huge windage and drag efficiency as well, which doesn’t show up in the numbers.

If you have CAD, you can trace a poly line, around any shape or profile of interest which can give areas and girths. Real numbers rather than a visual guess. If you convert those (closed) polylines into “regions” (in AutoCad) you can get the centroid of those traces, which gives you the ability to calculate moments for comparison.

When I was looking into balance problems on Sidecar, it is the underwater hull, appendage and sail area traced profiles which allowed me to quantify the differences between various designs and recognize the trends and outliers.

The same goes for centers of effort for rigs, you can compare the differences between these and the hull appendage CLR’s to see how balanced they are.

Overlays are what you make of them. I use them a lot, mostly out of curiosity…. Again, it is nice to see how Sidecar, or any proa design fits into the multihull world.

For example, if you look at the outline of Sidecar on the Seacart 30:

• Seacart 30, vacuum bagged, autoclaved carbon composite has a Base Speed of ~ 13.0 knots white sails only single handed.
• Sidecar (31) carvel plank timber, home built has a Base Speed of ~ 11.4 knots white sails only single handed.

Could you sail a Seacart 30 single-handed off docks, off moorings or anchor as easily as Sidecar? Not likely. Space and livability down below? Sidecar wins hands down. 88% of the Base Speed for a tiny fraction of the initial build cost.

And then there is this:

Hulls

As it happens they are also both around the same overall weight in rating trim. Vacuum bag and autoclave a Sidecar in carbon composite and you have two choices:

A) Save the weight, say 300 kg, and keep everything else the same: Base Speed: 12.3 knots.

B) Keep it the same weight and rig, make the main hull longer, bearing in mind that Sidecar’s bare finished 31 ft timber vaka also weighs around 300 kilos. 12.3m LWL gets you the same Base Speed of 13.0 knots. Or play the numbers outlined above, adding length and/or more sail area, for whatever combination feels best for your purposes.

Rigs

To achieve its ~ 13 knot Base Speed, the Seacart 30 needs 60% more sail area on a 60% taller and 3 times heavier mast than for Sidecar to achieve its ~ 11.4 knot Base Speed. The difference in mast weight alone is the rough equivalent of 17 house bricks attached mid mast. You know where most of the money is in a sail boat? Spend the cash difference to make Sidecar longer again with more sail?

It is much easier to see and understand these kinds of things when you look at overlays. Enjoy overlaying and playing the numbers to find out.

Base Speed is further explained here.

All images courtesy and copyright Robert Zabukovec.

Much thanks to Robert for the submission, I’m sure you will be as fascinated as I am!

INTRODUCTION

I first became aware of proas as a teenager through my father, who was fascinated by the J.S. Taylor flights of fancy in the sixties. I have been a dinghy, keelboat and offshore racer for over 60 years.  I built some of my own racing dinghies. Not sure why, but I started doodling proas in the early nineties. I also doodled all kinds of monohull boats and entered yacht design competitions occasionally, even got an honourable mention in the RORC competition for the Whitbread 30 yacht.

I decided to go mad for the Yachting World 2000 yacht design competition and drew up a proa (see photo above), incorporating many of my (naive) thoughts at the time. The overall concept has evolved ever since.

When I retired, I was looking around to buy a suitable second hand yacht. Nothing was sufficiently interesting for a good enough price, and certain in the knowledge that whatever I bought, I would also spend a lot of money upgrading, and still not be happy. So I thought why not build a proa?

SIDECAR DESIGN PARAMETERS

• Fast single handed daysailer to minimize overnight passage making.
• Fast shunting. Navigating King George Sound (Tasmania, AU) usually requires 5-6 short tacks in gusty, shifty conditions. Sometimes in both directions because the wind can swing 180 degrees during the course of the day.
• Overnight/short stay accommodation for 2-3 people.
• Flat bottomed for dynamic lift and ease of construction.
• Reversible rudders for faster shunting. Preferably liftable.
• Electric auxiliary. I am no mechanic and hate noisy smelly gas outboards which decide not to work when you really need them.
• Beachable and preferably containerable.
• No netting or trampolines. Minimal bow work.
• Contemporary aesthetics and rig, not a Polynesian copy. Aerodynamic to minimize air drag.

And… my wife hates boats which heel and wanted to be comfortable whilst she reads a book, preferably down below with a good view outside and communication with me on deck.

STATISTICS

Length vaka: 9.50m LOA
Length ama: 6.25m LOA

Draft boards up: 300mm
Draft boards down: 900mm

Beam: 5.57m BOA
Beam Bc/c: 4.50m

Displacement light: 1060kg
Displ vaka: 720kg static
Displ ama: 240kg static
Displ crew + consumables: 100kg

Sail area main: 29 m2 fully battened
Jib: 11.4 m2 fully battened
Light staysail: 16 m2 on furler

Ratios
34.07 Displ/Length
39.86 SA/Displ
0.53 Cp vaka
0.53 Cp ama
14.42:1 L/B vaka
16.07: 1 L/B ama

Base Speed: 11.4 knots average. White sails only

RIG

Dyneema stayed rig. Carbon spars. Circular section 92mm OD mast. 110x80 elliptical section booms. 70mm OD tapered sprit. All 3mm WT. Sails hanked to luff stays. No heavy expensive mast tracks and batten cars. Fixed strut vang to mainsail. No heavy expensive jib tracks and cars.

FOILS

2 x reversible through hull cassette balanced rudders, NACA 0010 section.
HM carbon shafts, tiller steering.
No centerboard, chine runner on lee side of vaka.

AUXILIARY

Reversible 160 lb thrust 48 volt Pelican electric trolling motor in cockpit.
Power: 2 x 60 amp 48 volt lithium batteries in ama. 30 kg total.
Charger: 2 x 145 watt Solbian PV panels on cabin roof.

CONSTRUCTION

190x12 Paulownia carvel planking, edge glued with PU glue. Double planked vaka bottom. Inner layer laid longitudinally, outer layer cross planked. Ama mostly cross planked.

Paulownia is a very light pale colored and quick growing wood originating from China. It has a weight of 260-280 kg /m3, so around 80% of the weight and strength of Western red Cedar, around a third of the cost and slightly softer and also rot resistant. It is plantation grown in Australia and many other parts of the world, and can be harvested and re harvested every 8-10 years. Tasmanian Oak was used in areas of high local stress, where loads could not be sufficiently dissipated.

There was a lot of spiling, and some curved areas could only be done by routing out half depth U channels at spacings to suit, spiled,  then filled and faired with epoxy bog prior to glassing.

Exterior epoxy sheathed in 450gm/m2 glass, double layer on vaka bottom to chines. All timber sealed in epoxy, WEST style.

Bulkheads and permanent frames CNC cut laminated Paulownia panels. Bunk tops and other structural pieces CNC cut 6mm Okoume plywood. Temporary frames 19mm CNC cut MDF.

The build took just over three years, with the vaka being built under the back verandah, and the ama and the wing aka built in the shed. It was a leisurely pace, and i also lost time during the winters due to temperatures too low for epoxy work.

The three pieces were them assembled on the back lawn, then rigged and finished off prior to trundling it across the lawn and launching it into a small inlet off King George Sound, July 2017.

SAILING

Sidecar is very responsive, it accelerates (and decelerates) remarkably quickly. It is sensitive to trim and weight placement. It rewards good helming and trim, and equally punished poor handling. The boat has 2 reversible rudders, and either or both can be used, depending on conditions and speed. Generally, I steer with the aft rudder, leaving the forward rudder to feather and find its own way through the water at more than 4 knots boat speed. At speeds less than that, it is better to use the forward rudder, with the aft rudder locked off and used as a centreboard. When I need to do big, fast directional changes, and to crab sideways up to a dock or mooring line, I use both.

It is happiest and fastest going upwind. There is little speed gain off the wind, unless the boat is over canvassed upwind.

Top speeds so far, in mostly fair conditions no more than around 15 knots gusting 20: Upwind: 12.7 knots, reaching: 16.3 knots, DDW: 13.6 knots. White sails and single handed.

Shunting sequence involves dumping both sails simultaneously (I don’t bear away at all), pushing both helms down so that they will flip by themselves correctly and then sheeting in the mainsail to beam reach position, the boat will literally stop dead and spin towards the new wind without using any rudder at all. The jib is quickly sheeted in to near close hauled, then the rudders are straightened up and used to control the rate of round up when sheeting in the mainsail. Pull the mainsail in too fast, and the rudders can’t cope. A lot to do with one pair of hands, but pretty quick in lighter conditions where the boat doesn’t round up too quickly and the sheets can be hauled in faster. In heavier air, the boat can respond too quickly if you get it wrong, so more care is needed to avoid stuff ups. With extra pairs of hands, the whole process would be much more simultaneous, controlled and faster again.

Sidecar flies the ama at 9 -10 knots boat speed at around 3 degrees of heel, and the helm becomes noticeably lighter when it does. A wonderful sensation, but you need to constantly trim the mainsail and feather into the gusts and bear away again in the lulls to keep the ama skimming. I have yet to let the boat heel much more than 15 degrees. I have gone beyond that when gear has broken on the boom and very recently, the boom broke itself, and gone to 30-45 degrees, but thankfully the boat seems to stop there, probably a combination of leeward buoyancy shift, auto dumping of the jib and shadowing of the mainsail itself.

It is also very dry, most spray flies off to leeward, thanks to the curved forward topsides and the wing aka. There is no bidet style flushing up through netting strung between more conventional aka beams, and working on the wing aka with a jib or anchor is far drier and much more solid and stable than bouncing on netting or balancing on a narrow foredeck. It provides easier access on and off the boat also for anyone who is not agile or confident enough to bounce across netting. It is also great for storage.  Anchors, mooring lines and warps, fenders, brushes, boat hooks etc are all stored in the wing aka locker well out to windward, but still within easy reach of the cockpit. And finally, because it is an inverted wing, there is the possible benefit of some down force RM when it blows.

EVOLUTION

Sidecar started life with 2 lifting windward side hung rudders and a two way asymmetric canting centerboard. Canted to windward, it provides earlier ama uplift and height to windward. It could lift the ama at around 7.5 knots, 1.5 knots sooner than otherwise. Canted to leeward, it provides more RM and height to windward. But the forces were so great, it took 3 iterations of hinges before it was strong enough, and despite 24:1 plus ratios, the associated controls still weren’t man enough and cumbersome. I also had concerns that the canted centerboard in its full retracted state could still catch waves in heavy conditions down wind, so I eventually took it all off, with no regrets. I also reckoned to be losing around a knot of boat speed with the centerboard deployed, so it was hard to see how VMG was significantly improved, if at all.

But the biggest original problem was one of helm balance and weight.  The rudders were fairly closely spaced which facilitated the tiller steering arrangements. Despite being the same proportions and spacing as the (in)famous proa Bucket List, even with the centerboard down, the rudders were working hard with poor response and always on the point of stall.

Without the centerboard (during board mod/repair times) the boat was uncontrollable upwind. Making the rudders bigger, deeper didn’t really work, it just made the rudder loads much larger. Adding a skeg under each bow (image below left) didn’t work either. It was great for sailing in a dead straight line, but much worse response times and hugely increased rudder loads because of it.

Left: bow skeg. Right: chine runner.

I then put in bow trunk cases to take either bow board cassettes or two way rudder cassettes. I made bow boards first and kept the larger rudders. Raising the front bow board provided the necessary balance and gave an immediate improvement in handling and performance. But it was 3 foils doing the job of 2 and now having to raise one board and drop the other on every shunt, taking more time, something I wanted to avoid from the outset.

Sidecar also has a chine runner (image above right) on the leeward side of the vaka. I was aware of their reported success on Matt Layden designed mini cruisers, and having experienced the dramatic effect of simple wooden skegs, I thought nothing to lose, easy to put on, easy to cut off. As it happens, I believe they are very effective and can recommend them to anyone wanting a simple effective solution especially if your hull is flat bottomed and provided you fall within the Layden parameters.

Sidecar now has reversible cassette rudders nearly double the distance apart of the original rudders, and have the same effective size plus some end plating benefit from the flat bottom. Rig has stayed largely unchanged. I now carry a bridle attachment for the windward jib hoist, which eliminates the catenary action of leech tension on the weather shroud and the slight CE shift aft.

All sails are hoisted and sheeted on 2:1 purchases which means that everything can be done by hand, without winching, which is faster despite the extra rope length involved. The winches are used for snubbing and making off, and when I need to use a handle, it is time to reef.  I have a 12:1 cunningham and an 18:1 foot/ leech outhaul.

The original motor was a Rick Willoughby one off special, worked, but proved to be impractical to deploy and store and was underpowered. The 160lb thrust trolling motor I have now, didn’t exist when the boat was built. I had to make a custom clamp to allow the motor to work at 90 degrees to the normal clamp orientation. It cruises at 3-3.5 knots with a top speed of 5.5 knots in flat water.

Sidecar is sensitive to trim, because it is so light and narrow. It I stand on the vaka bow it drops 7– 8 cm. It seems to sail best with slight aft trim and ama nose up. With my wife on board, when short tacking, she goes below to make room in the cockpit, and she shifts from one end of the saloon to the other with each tack in heavier breezes. Similarly, sitting to leeward and raising the ama as much as you can, improves speed and balance.

BI PLANE RIG

Without doubt, the rig that gives the best all round performance balance and handling on most yachts, whilst keeping rig height, heeling moment and weight down is the sloop rig.

Proas are no exception. On a proa however, sloop rigs have a significant disadvantage when it comes to shunting/ tacking, in that the foresail needs to be furled or taken down, swung over or carried to the other end of the boat and hoisted or unfurled again, with a lot of time lost each time. Or duplicate the headsail (all of them!) at the other end of the boat so that you furl one jib and unfurl the other simultaneously with interlinked furlers. Time loss is minimised, but there is duplication of foresails, furlers and sheets which is significant extra cost, weight and aero drag.

By setting the foresail out to windward and making the rig “Biplane” you avoid these issues and put the weight of the fully battened jib and all its controls in the best possible place on a proa. In the middle, and well out to windward. Being fully battened, it can remain on the boom, out of the way, saving set up and stow time. It also means less flogging with better setting and longevity.

Other advantages of the windward jib, apart from ease of shunting compared to a sloop rig and helping to keep the bow down during the manoeuvre, are that you are in the shade more often, it hang sets in light weather and it has a very low heeling arm. Running deep down wind, there is no shadowing, and the jib is more stable and controllable than goosewinging and can be used to deflect air at a better angle towards the mainsail. When a proa heels into double figures,, the power from the jib is automatically reduced due to heavily canted angle of the weather shroud, which is a lot more in proas, because the weather shroud angle is much larger compared to other multihulls due to the mast being well to leeward.

There are other theoretical advantages for bi plane rigs, but that explanation is for another time.

The BIG downside of a windward jib is that it is always behind you, so it is hard to check and maintain trim, which seems to change more than with a sloop rig. It can be luffing quietly, without you being aware.

Sidecar was also set up with larger light weather sails, flying off sprit which is housed in the jib boom. It has had limited success, improving speed in light and sloppy conditions, but at the expense of pointing. I am still working on that one. I get the feeling that it probably has a detrimental effect on the mainsail and extra sail would be best set off the bow, when doing long legs and time lost shunting isn’t significant in the scheme of things. I have shunted with all three sails flying.

The “mainsail” on Sidecar is actually a balanced jib on a luff stay. The balanced area is maximised when compared to an aero or balestrom rig, and by giving it a large square head and a straight vertical leach, the balance area of the sail can be further increased, all of which means that the CE of the sail aft of centre is minimised and high level sail area (in stronger, freer and less disturbed wind) is maximised.  Care has to be taken to ensure that when reefed, as the CE moves forward, it doesn’t become over balanced as can be the case with many aero rigs. There is an additional safety margin with sidecar’s mainsail in that when reefed, and the head well away from the masthead, there is a fair amount of catenary action, with the leach pulling back the head and luffstay like a bowstring, giving the residual sail more rake and less CE shift forward.

Some say that a sail-less mast causes more performance loss through drag than one with a sail attached despite the performance loss caused by mast induced turbulence along the mainsail luff. They may be right, but the weight and cost savings are enough for me.

IMPROVEMENTS

Sidecar is still prototype, with still lots to learn, tidy up and experiment with, especially the rig and chine runners/foils.

Sidecar 2 if built today based on the original criteria, would have spray step chines forward, to further minimise spray, increase forward reserve volume, and make the forward bunks a little wider.

I would make a bigger root chord on the wing aka, to increase cockpit size and storage and deck space with improve stiffness outboard. The larger cockpit, especially longer would make more room for others and increase trim options. It otherwise works perfectly single handed. Everything is close by.

It would have a larger balanced windward jib end plated to the wing and a slightly smaller balanced mainsail still end plated to the cabin top. Sidecar’s jib is currently 40% of the mainsail area. I would look to increase it to around 50%. This should improve helm balance, and reduce heeling moment for the same sail area. It might also improve the biplane effect, certainly at lower wind speeds.

I would add an extra halyard to leeward, so that either LW jibs or code Zero spinnakers (not furled) can be hauled out to the bows on an endless tackline, sheeted off the main boom and end for ended for long distance sailing with little shunting. Faster and easier to balance/self steer.

The ama would be deeper, the same depth as the vaka for more lateral resistance in lighter going, with slightly more displacement and more reserve volume above the waterline, but still the same length. Currently the ama is 30% of vaka displacement.  I would look to increase that to around 35%.

I might also add a chine runner to further increase lateral resistance whilst the ama is in the water. When motoring at slow speeds in wind, there is a noticeable difference in side drift between wind coming from leeward as opposed to ( designed for) windward side, because the vaka chine runner is only on the leeward side. So I might add a windward one to one or both hulls as well.

I also did a comparative analysis of a number of multihulls and proas and found that proas like Jester and Madness, (and I would guess Jzerro as well) have a lateral resistance area/ sail area ratio (working rudder excluded) of around 12%. Sidecar is 8.5% and Bucket List and the Seacart 30 tri is around 7%. I would be aiming at around 10% next time, with more coming from the hulls, especially vaka. Comparatively, Hull LRA/ SA’s respectively above are around 10%, 7% and 5.5 %.

I don’t need it currently, but should I decide that I want to improve VMG, a pivoting 2-way asymmetric centerboard can be hung off the leeward topsides. The extra area gives more CLR and when raked, better helm balance. The centerboard is already made by cutting down and modifying the original.

LINKS

Sailing Anarchy thread: Dear Mr Sidecar
Youtube: Sidecar: A Modern Pacific Proa

Note: All images courtesy and copyright Robert Zabukovec.