Firstborne: 8m light cruiser
Hey Proanauts!
I’ve been working on the design of a beach / camper-cruiser for the last few weeks, and thought it might be time to share. 😉
Design brief:
The intended use is to carry me and my brother (we are both >190cm tall and ~90-95kg each) plus camping gear on an extended trip through the islands of the Wadden Sea in the Netherlands, Germany and Denmark and possibly further, next summer. Edit: A nice to have, is if the boat is capable of taking two guests and their stuff along for the ride as well. The boat must also be very well suited to single-handing, ideally it should be possible to conduct all actions necessary for shunting and trimming, without ever having to leave the hiking seat between the akas.
The Wadden Sea means shallow water, strong currents, and 10-25 Knots of wind at nearly all times. I don’t know know how rough it gets out there, or how realistic it would be to be out there in a boat like this (if anyone has any experience in that regard, please share!), but I think it’s going to be a case of choosing our battles intelligently, and knowing on which days not to go out there. Before I take it anywhere near the sea, I plan to do some very extensive testing on lakes, and then take it slowly from there. If the Wadden Sea proves to be too rough / dangerous for a boat like this, the fallback plan is the Archipelago Sea in Finland, which has less wind and less current, but is perhaps even more beautiful, has just as shallow waters at parts, and has the additional hurdle that the whole thing, just like the rest of the country, is made of rocks. xD
Edit: It must be possible to disassemble the entire boat into pieces small enough for transport on a small trailer. The exact trailer dimensions are not fixed yet, nothing longer than 4500mm (rig & akas excluded) is a rough guideline for the moment.
Current status:
While my CAD model is still not done, I figured I’d post what I have so far, which is a nearly complete but unrigged vaka. I’m looking to start construction about 2-3 weeks from now, if I manage to get everything done and organized by then (which is still A LOT, so we’ll see how that turns out). It already being rather late in the season, I really have to start soon though before it gets too cold to work with epoxy in the workshop. If push comes to shove I can always postpone things like ama design indefinitely, so I at least get the vaka built before it gets too cold.
Why a trapeze-shaped flat-bottom chine hull?
I opted for a flat-bottomed chined hull (but with a fair bit of rocker) because I wanted to save labor and because I didn’t want to take the risk of designing a multi-chine hull only to find out that the plywood won’t bend to the shape I want. I’ve found a compromise between draft, deadrise angle, and bottom panel width that I’m relatively happy with, even if it’s perhaps a bit on the drafty side. If someone has any arguments as to why this hull might misbehave terribly, or have poor performance, fire away!
Vaka Stats:—Edit: Dimensions outdated!
WL: 6500mm
LOA: ~6600mm (the bow stem will get a nice foam-glass piece glued onto it)
Beam (WL): 365mm
Beam (bottom): 200mm
Beam (gunwale): 550mm
Freeboard (@300kg Displacement): 350mm
Draft (@300kg Displacement): 300mm
Approx. mass unrigged: 65kg (that’s a bit heavy in my opinion)
Scantlings: 4mm plywood sides and deck, 8mm plywood bottom (all glassed on the outside), 200mm timber for bulkheads (with 4mm plywood to seal the bulkhead), aka support beams, and maststep.
Note: What is currently not shown, is that that vaka is actually made of 3 sections: 1m + 4.5m + 1m due to stowage and transport considerations. The three sections will be bolted together with 4 removable bolts that pass through epoxied (but not glassed?) 20mm timber-reinforced bulkheads.
Missing vaka features:
- Steering oar supports and brackets
- stowage compartment hatches
- access holes in the foredeck
Approx Ama Stats:
LOA: ~4000-5000mm
Max displacement: >0.2m^3
Overall design: Rounded, but more or less flat-bottomed with wave-piercing bows (think AC45)
Boards: Either dual asymmetric daggerboards, or a single 2-way-foil board (either way there will be crush-blocks mounted inside the trunks (as opposed to on the board itself like Russell Brown has done) to allow deploying the boards only partially but still have the protection of the crush blocks.
Construction: Strip-planked?
Safety Ama
I’ll definitely have a safety ama. I haven’t put much though into it yet, but it’ll be kept light and as simple as possible from a fabrication standpoint.
Approx. Aka stats:
CL-CL (Vaka - Ama centerline distance): 2600mm
Arced 80mm x 80mm box-beam construction, top and bottom aka panels 18mm Plywood (3x6mm layers laminated) each, side panel 6mm plywood. The akas will be bolted to the vaka and ama.
Rig:
Dierking-style crab-claw (with pivoting bungie-supported mast) for very fast shunting, simple overall layout, and plenty of options to depower the rig with brailing lines and mast canting.
Yard & boom: ~6500mm
Approx sail area: 10-13m^2
Steering:
Dual steering neutrally-buoyant oars in oarlocks fitted with hiking poles, and retrieving lines run along the akas (just like all other lines)—and yes, that will be a bit of work to design it so it works nicely 😉 —Edit: There have been a lot of comments about steering oars not being suitable to a boat this large anymore. Perhaps you’re right. I may have to opt for kickup rudders or rudderboards after all…
Long post, but here are the goodies! I would really love to have some feedback on the design from you guys before I start building! I’ll post more CAD images as I go along.
Cheers!
Marco
And one more pic from the top…
—One thing I’m still really not happy with at the moment is the daggerboard situation. At the moment I’ve resigned to putting them into the ama, but I don’t like that. Since it’s the vaka that you are generating the windward lift for I think the foil generating that lift should be in the vaka; the ama should just do whatever the vaka tells it to do, even if that means going sideways because of some wave passing under the boat or whatever; having boards in the ama creates a weird situation there.
I’ll have a look if there is actually enough space in the vaka to use it meaningfully, (e.g. adding suitable floorboards so that you can lie in the vaka to catch some sleep while the other guy is sailing), if there is not enough space for that, then I might as well butcher the insides of the vaka and put the daggerboard trunk(s) right in the middle of the vaka next to the maststep, there’s plenty of room for stowage in the bows after all…
Two comments.
If you’re using a crab claw its handy to have a separate spare smaller rig, crab claws don’y reef worth a damn (but they do brail and depower nicely).
Best of luck with the steering oar(s) I had good results on smaller proas much less so on the 6.9M one, boat was much better with rudders.
Third comment; go for it, I really miss P52 and look forward to its successor when I can get back to building. Shallow water and high winds are pretty common around here also.
cheers,
Skip
Quick edit 4th comment; unless your 20mm particle board is way different from we have here in the states, it has NO place being in a boat, fine for molds left on shore but a disaster on the water.
Thanks for the feedback!
What’s your take on the vaka geometry, you think a sawed-off deep-v like that will perform and handle ok, or is it hard/impossible to say?
Particleboard: The chief reasons I wanted to use particleboard are that it’s cheap, homogeneous, and very stiff; which is what you want from a bulkhead. I also wanted to save myself the labor of having to make framed plywood bulkheads. I do have a suspicion that the 200mm particleboard bulkheads are adding a lot to the weight of the boat though.
What makes you say that particleboard is such a disaster on a boat, and what would you suggest as an alternative? I really don’t have a clue here, so I’m very curious! 😊
Particleboard is stable (resistant to warp), but it is way less stiff than an equivalent thickness of wood along the grain. It is also fairly heavy, so it has a poor strength to weight ratio. If particleboard gets damp, it swells and eventually turns into soggy wood chip, so if you want to use it your waterproofing methods will need to be impeccable. Even if you sandwich it between two thick layers of glassfibre and epoxy, in my experience wood still manages somehow to get damp. If you were to choose the worst possible boat building material, particleboard would probably be it.
Thanks for the explanation!
If you were to choose the worst possible boat building material, particleboard would probably be it.
xD
Edit: I think then I’ll just do the same as what Gary Dierking did for his Wa’apa, where the vaka also comes apart into 3 sections for easier transport: just use 4mm plywood bulkheads, each supported on one side by 2 19x50mm solid wood planks, through which the bolts are run to connect the two hull sections. That should be light, easy to make, and strong and stiff enough that I don’t have to worry about losing my entire bow section even while underway in a seaway. 😛
Manik,
Some comments:
I have sailed in the Dutch Waddedzee (Oost Vlieland / Borkum / Langeoog) and I imagine the Danish Wadden Sea would be similar, it certainly looks like it on Google Earth. You are right, they are shallow and very tidal. Not withstanding the normally strong winds, there will still be lots of times, particularly early and late in the day when there will be little wind and lots of tide, and there will be times when you need to go up narrow channels to get to a port (or restaurant) and shunting may not be feasible or too much hassle. So you will need a good auxilliary engine. Big waves should not be a problem, but there will be steep chop in strong wind against tide situations.So you will get wet. You might also consider how you carry bicycles if you want to explore inland and the North Sea side, although sometimes you can borrow them from a harbour cafe.
Bulkhead framing for your simple shaped hull should not be too onerous, especially if you are thinking of building a safety ama as well. You could always get bulkeads CNC cut out of your plywood (including lightening holes) and just glue them together.to get the required strength and stiffness.
Why a safety ama? A pod or heavily flared out topsides to leeward gives you much more usable space and is easier to build..
Rob
What’s your take on the vaka geometry, you think a sawed-off deep-v like that will perform and handle ok, or is it hard/impossible to say?
My take is you should be fine, there’s enough hulls roughly similar to yours to make some broad generalizations
(may or may not be correct) 😉
What comes to mind
Fairly smooth riding, reasonably weatherly without foils, easily overloaded.
Skip
I’m really glad to hear from someone who’s actually been out there! I’d kind of hoped that I could go without an outboard motor (if we get becalmed and the 3 knot tide is trying to haul us out onto the open sea, just use an anchor), but now that I think this through a bit, especially with the channel & port situation, you may be quite right in that having an outboard is a necessity. There’s no way you can paddle against a 2-3 knot tide; only being able to reach ports at or near high tide, would definitely be an inconvenience. The 30cm draft would ensure that we have at least a bit more space to maneuver (except at low tide), but with only a partially deployed board, even with a rapid shunting rig and some extra maneuvering space, short tacking up a channel could get pretty tedious, or turn out to be impossible.—Not to mention there’s other traffic around.
Where the safety ama is concerned: The entire boat has to be disassemble-able and transportable on / in a large car. That’s been one of the key drivers of the dimensions of this boat since the beginning (I should have mentioned that in the design brief! 😊 ). Having a large pod or lots of hull flare on one side, could make transporting the central 4.5m vaka-section on a car-roof quite problematic, unless it’s detachable and/or disassemble and transportable inside the car.
That said, the point you made about carrying bikes along is a very good one. Originally I’d intended to build a somewhat larger boat, and it would easily have had space for 2 bikes in some sort of large watertight bags on the leeward deck, but I more or less discarded that idea without giving it any further thought when I made the boat smaller. Maybe there is some good solution for the leeward side which would actually allow it, even on a boat of this size. I don’t really see why not, other than the additional weight perhaps, though I could make the bottom panel slightly wider, or increase the overall dimensions of the boat slightly to compensate.
The limiting factors are that no components may be over 6.5m long, the car roof only takes 80kgs, and everything else has to fit inside the car with one or two of the rear seats folded down. Transporting 2 bikes in addition to the aforementioned boat with the car, seems like a pretty unrealistic proposition. Maybe the trailer is unavoidable in that case, but I’ll look into it.
Manik,
I know the Waddenzee is a nature lovers area (in every sense of the word) but unless you are planning to cruise as naturalists, sleep under the stars and eat out for all meals, maybe you should do a pretty detailed inventory of all the kit you will / might need and the weight / mass of it all. You might find that you don’t have enough load carrying or storage capacity for 2 big men. Plus your bikes. Plus any friendly Dutch / Danish girls you might meet along the way.
And that goes for the car as well…..
Rob
Rob, you really hit the nail on the head. Today after deciding that taking bikes along would be a nice extra, I decided to redo my mass estimate in some detail, and realized I was just completely off the mark before. Had I had the time in the last few months to read the “Sweet Rhode Island Red”-Thread, I would have known that much earlier. After revising the estimate and then iterating the size of the boat upwards until everything lined up, I ended up at 550kg displacement instead of the previously assumed 300kg. That’s what you get for doing a very sloppy initial mass estimate! I really should know better, but I guess I just let complacency get the better of me there.
I played with the hull model quite a bit today as a result. With the LOA up at 8m, and slight increases in beam, the width of the bottom panel, and draft, I’ve now gotten it up to 0.54m^3 volume @350mm draft, 0.66 @ 400mm, and 0.72 @420mm draft (allows for 550kg base estimate (includes bikes) + 170kg for two charming guests, their stuff, and some extras). The numbers for wetted surface area are ok, overloading to 130% increases wetted surface by 20%, which will make the boat maybe 5-10% slower—a non-issue. Having only 280mm freeboard in that condition, as opposed to the normal 350mm, could make for a bit of a wet ride though.
Do you guys have any ideas on how you could transport two bikes in a boat like this? And where and how could I best provide dry seating for 2-4 people? In the vaka, between the akas, or perhaps on a raised lee deck?
Edit: I just realized I still haven’t incorporated the weight of the outboard, which is probably a necessity, into the mass budget. :((
Do you guys have any ideas on how you could transport two bikes in a boat like this?
Start off by choosing Bromptons: http://www.brompton.co.uk/
Regards
Robert Biegler
Do you guys have any ideas on how you could transport two bikes in a boat like this?
Start off by choosing Bromptons: http://www.brompton.co.uk/
Regards
Robert Biegler
Or learn to unicycle, much smaller and great at improving balance
Tink
I don’t know Bromptons, but I would have suggested folding bikes as well. As long as you have enough basket volume (or rucksacks) to carry provisions back to the boat.
I probably have missed it, but have you allowed for the displacement of the ama in all of this? The design of the ama and its storage potential should be developed at the same time as part of the overall design??
Another thing you might consider is to make some form of long detachable storage “coffin” (or sled / barge) spanning across the akas to windward. Using it as a backrest and with a fold down solid bench seat (both sides?) it should give a little protection from the wind and spray. When you are daysailing or returning back to the same spot, you can leave it behind locked up. Bikes and all. No one is likely to run off with it across the sand dunes, especially in Holland. You also have a table or bench seat whilst camping on shore. It would be easier and faster to load and unload than lots of separate bits of kit and the overall design of the proa won’t be compromised as much by storage issues and end up looking like a junk barge.
Sometimes maybe you could even tow it, like a tender. It might prove faster and more manageable that way, especially in light weather.
I think I’ve figured out a solution for the bike and deck-space issue: a lee pod which is ~4000x1200x250mm large, enough to stow two normal non-folding bikes end to end on their sides (with pedals and steering bar removed). Said pod, with a flat top, also provides a huge amount of deck space ontop, enough for 4 people to comfortably sleep on in good weather. The deck will get a plywood sidewall, and towards the bows a nice half-circle arced panel as well, to act as spray guards, basically a Russell-Brown style lee pod, but open at the top to enjoy that sunshine!
I also decided to increase freeboard by another 140mm today. The total vaka height is now a pretty colossal 840mm, providing nearly 500mm of freeboard in the normal condition, and about 420mm in the “overloaded” 4-person condition. The weight increase for the extra freeboard is rather moderate (about 25kgs), and to compensate for it I just increased the beam, and width of the bottom panel, slightly.
With the vaka so tall now, I’m also thinking about adding a sealed floor above the waterline (with some access ports obviously) for a couple of reasons:
(1) Sitting on the lee deck or the akas would be a lot more comfortable if you can have your feet on the floor of the vaka
(2) That floor would also add lots of sealed flotation volume in case of capsize
(3) The floor would easily be high enough to add drains which are above the waterline, to the central vaka section. I would consider that a large plus if you’re out in a good chop for a while
Stowage volume is an interesting question. I think the stowage lockers forward of the akas (where those nearly square openings in the pictures are) are bound to be pretty roomy by now, but combining the idea of foredeck stowage lockers with Rob’s idea of having a removable cargo pod on the akas, allows you to use your cargo as dynamic ballast, instead of having to rely on the (extra) weight of seawater. On windy days / during windy times you put your stuff in the cargo pod, and on not-so-windy days you put it in the foredeck lockers. Plus you get a backrest, ‘table’ when you are onshore, and convenient way to get all your stuff to shore in one batch, all at once. That’s a phenomenal all-in-one fix. 😉
@Rob: could you make a rough sketch or something about what you meant concerning the seats? I didn’t quite understand what you meant.
I’ll try to get CAD models done for the akas, ama, and lee pod structure sometime soon to visualize all this and get some more detailed mass numbers. At the moment I just have my plate a bit full with some other stuff unfortunately. :(
Basically this vaka is just a scaled up and slightly tweaked version of the old one (I haven’t updated the fordeck hatch ports and wave fence yet, that gives some idea of the relative scale). As it stands the vaka is at:
L_WL = 8000mm
B_max = 850mm
B_WL = 530mm
Draft (@580kg) = 350mm
Draft (@780kg) = 420mm
And one last thing, thank you so much for all your feedback guys! Getting a second opinion from people who know what they are talking about is truly enormously helpful, and I really couldn’t do it, at least not nearly as well, without you guys! 😊 Thanks so much!
Hello Manik,
Greetings from Wilhelmshaven!
I live and sail where you want to sail. My Homewaters are the Eastern Friesian Islands. Iam a boatbuilder and amateur designer. Perhaps we can communicate private and help each other.
My thoughts about proa design are quite similar to yours. Perhaps you look at my thread: Kea 5.4, Backpackers Cruising Boat http://proafile.com/forums/viewthread/60/ to get an impression of what I have in mind. I have also bigger versions and different-, more modern stylings of “Kea” in my computer. If you are interested in spoiling your thread a little, I can post some images here.
My comments:
Bycicles:
All of the frisian Islands have narrow streets coverd with tar. To explore them, a long skateboard with 8cm wheels will do. On most of the islands cars are not allowed, so skatboarding is save. Sometimes, when the wind ist at the right angle and strength, I use a matress-kite to sail this skateboard to town.
Trailering:
What you have in mind cannot be transported on the roof of a car. You will have to mount a hook to your car and use a trailer.
Three Part Vaka:
I think this is a good idea to save storage space at home. Engeneering is easy!
Steering:
Oars will simply not do it. A boat of this kind must have a pair of Hobie Cat Rudders or another kind of “normal” rudder.
Material:
Do not choose particle boards or other cheap materials for boatbuilding. If you need help for material choice (cheap and reasonable boatbuilding-quality), send me a PN. I have succesfully done some low budged projects and can tell you what will work and where you can get it in northern Germany.
Design:
You have two possibilities: Either you raise the freeboard to a normal proportion ( ~1/10 of length) or you make your Vaka watertight like a beachcat. Otherwise you will end up sailing a submarine. In the waddensea normally the waves a small and the area is very sheltered, but you will face short high waves between the islands. And you cannot avoid this areas if you want to get from one Island to the next..
Some dry storage and bunk is more than “nice to have” in our region. Its not funny living in a wet tent.
Auxillary Power:
For a boat like yours you need an outboard motor of 4 PS minimum.Its a important safety factor with the locally strong currents.
Ok, thats it for now.
Iam looking forward to your answer
Grretings from the North Sea Coast, Michel