Dear Johanses,

I am wondering what are your thoughts regarding sail / hull balance?  - The lug sail will move the CoE of the sail back towards the stern, how is this balanced? 
Is the rudder acting as a centreboard?
I had a 16’ V hulled proa, the hull CoE was a long way towards the bow, which required a lot of movement of the sail (a windsurfer rig) to the bow.  Do you find the flat bottomed section keeps the hul CoE more central?

I think your ideas are definately worth putting into a sailable boat. (I am pondering designs at 24’ (3 sheets of ply) as probably the minium size that is a crusier and not a beach-boat.  Any smaller and the effect of crew weight is too significant). For a smaller proa the flat bottom concept is quite acceptable, it will pound a lot more than a deeper hull, but at that size will be pretty wet in anycase.  Whether you will get away without a centreboard I doubt.  Perhaps in a moderate wind and flattish sea,  definately not in a choppy sea as the board needs to get into undisturbed water.

It has been done on a catamaran.  Have a look at Pete Hill’s Oryx,  it is a KD860.  He has yet to post how she goes to windward.

Mark

I am wondering what are your thoughts regarding sail / hull balance?  - The lug sail will move the CoE of the sail back towards the stern, how is this balanced?

I have learned that a hard-chine sharpie hull is very tolerant of CoE-variations. The 90 degree shines on both sides of the hull act to stabilize the hull, so one can view the hull as a very low aspect foil. It might not be the worlds most efficient one, but its very directionally stable. I have never needed a centerboard or any kind of additional foil. The rudder ads to the lateral resistance and is very important to the directional stability. Its very efficient in controlling the direction of the hull.

Do you find the flat bottomed section keeps the hul CoE more central?

Yes. But the rudder helps in that regard to.

Whether you will get away without a centerboard I doubt

I have sailed my model in quite rough waves and its no problem. I don’t think its a problem. It has to be heavier than what is considered sane on a multihull, but because of the wide flat bottom its quite fast anyway. I dont think a 37 feet advanced sharpie proa could compete with Jzerro when it comes to raw speed or beauty, but based on my experience it would not hesitate to sail one in quite rough weather. The seems to be very predictable and stable.

I think an Advanced Sharpie Proa is very comparable with Matt Laydens Paradox and Little Cruiser.

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Johannes.

Johannes,
A while back I contacted Richard Woods about the Gypsy catamaran.  Normally built with a dory shaped hull and a low aspect keel, but could have a round section hull and dagger boards.  His comment was that a dagger board (with dory hull) would make more diference to the round section (with low aspect keel), due to the deeper penetration into undisturbed water.  So my comment was largely drawing on his (great) experience.  Though with my Hirrondelle, which has dagger boards and goes well in smooth water, I always felt she could do with deeper boards in choppy conditions (Hirondelle - recently sold - next boat is a proa!).
Consider being stuck in a bay with an onshore gale, the seas will be awfull and every advantage to windward will be required (assuming there is no big deisel engine down below).
Mark

Based on my experience with very low aspect “foils” - my different hulls, i think they are more able to beat to windward in terrible conditions than high-aspect foils (daggerboards and fin-keels). High-aspect foils stall much more easily than low-aspect, and when the waves toss the boat around the daggerboard/keel will not be able to establish a flow long enough to actually do any good, whereas the low-aspect hull with very long chines will always have a large portion of the hull beneath the surface and will act as a lifting foil. Maybe not very good, but it will take enormous amounts of disturbances before it will lose its lifting power.

My advanced sharpie has a lot of lateral area, so its very stable. It will resist being moved to windward even when laying still. A fin-keeled boat is very easy to move sideways as long as it is laying still.

This is based on my experience with my models. Its very important that the chines have a very sharp angle. If they are rounded as little as half inch radius they gradually loose their ability to create lift.

Johannes.

Good point, as you slow to a stop, the fin can be pushed sideways more readily than a low aspect keel,  though that is probably because the low aspect keel has a much greater area. 

(at the other end of the scale (and probably of no relevance,) I recall from windsurfing at speed, when, on occasions, the foil completely stalled, the tail of the board spun down wind, but the speed did not diminish, rather alarming!)

Mark

And now I am doing it for real and build my proa. Drive savely, keep your job but start building.

Today i placed the three plywood pieces that will be the bottom part of my proa. I think i can safely say that when my girlfriend sees this she will not be enthusiastic about it! I have to crawl under the plywood and over my outrigger laying benethe it to get to my livingroom. This would turn our ralationship into WW3.

I have to find a suitable space before i start building the Vaka. Today im only trying to get a feeling for the size and avaliable space.

Johannes.

Yesssss Johannes go for it! Good feeling, isn’t it?
Alexander

Today i started a new advanced sharpie proa based on my experience with my asymmetrical monoproa. It will have the same rocker in the bottom as the lee-side. The windward side will have about 10% more rocker.

Because of my monoproa i started thinking a lot about asymmetry and any possible advantages it can give.
I can´t stop my curiosity, i want to learn as much as possible. I really like the asymmetry-concept.
I hope i can sail it before lake Mjörn freezes over.

Johannes.

This is how far i got today. More tomorrow.

Its going to have a chinerunner along one third of its length. I added the chinerunner as a way of damping unwanted motion and hopefully to act as a hydrodynamic “fence”, like the angled tip on some airplanes wings. I hope it will ad to the lift of the asymmetric hull without having to use to much asymmetry.

Johannes.

I have been reading through everything i could find about the Triloboats again. I feel that i easily get caught in the downward spiral of ever increasing complexities. Sometimes one have to back up a couple of steps and review ones goals, strengths and weaknesses. I don’t think i will build a true Triloboat, even if that is probably the fastest and cheapest boat there is to build. Im interested in trying out some ways to get the advanced sharpie proa even more simple and cheap, and i think the Triloboat has a lot to offer. There has been sailing barges and scows for as long as we have had saws cutting planks. There are remnants from early 17 century of flat bottom scows and sharpies, and many of them crossed open oceans with enormous loads of different kinds. The New Zealand scows and Thames river barges are probably the most recognized types. The Thames river Barges

From Wikipedia:

The barges also traded much further afield, to the north of England, the South Coast and even to continental European ports. Cargoes varied enormously: bricks, mud, hay, rubbish, sand, coal and grain, for example. Due to the efficiency of a Thames barge’s gear, a crew of only two sufficed for most voyages, although by today’s standards it would have been hard physical work at times.

I think that if one drops the requirements of always trying to make the proa faster, lighter and more speed-oriented and start looking at ways to create a cheap cruising-proa. The proa has a lot of advantages that no other water-craft has. The much larger and longer main hull (vaka) creats a very easy motion, as there is no “fight” of forces like on a catamaran or trimaran. It can be a lot cheaper than a tri or catamaran due to the very low loads on crossbeams and only one true hull. The outrigger is more of a floating keel, and should be kept slender and light. The very wide beam make the proa have an enormous mass inertia for sideways rolling, and creates a very big platform to live on.

Based on the above thoughts i came to the conclusion that i have to try a simple barge-proa based on the Triloboat-concept. I have no idea what will become of this, but i hope there is knowledge and experience to gain at the end of this wild cross-breed-test.

I tried to imagine what the pros and cons of this kind of proa would be, and this is what i came up with:

+ Load carrying capacity.
+ Rational use of plywood.
+ Great resistance to pitching and hobby-horsing due to high prismatic coefficient a very big flat part of the bottom.
+ Shallow draught.
+ Extremely easy to build.
+ Lots of usable space for a given size.
+ Enormous resistance to pitch-pooling.

-  Excessive pounding. (Very weight-dependent)
- Could become hard to handle due to the large lifting force of the ends of the hull. Waves will always lift the hull ends, and the rudder and sails will become overpowered by this.
- The hull will have more windage.
- Everyone will hate the looks of it. Its as far away from Jzerro as one can come and still be able to call it a proa.

Johannes.

Johannes, have you seen info about Mary and Her Lamb? A historic scow proa!
http://www.thecheappages.com/proa/commodore.html#Mary & Lamb

Thanks for the link to the Mary and Lamb.

I have seen it before, and i think its a very interesting Proa. Its very far from the classic Pacific proa in many ways. More of a scow/barge-proa. A very westernized proa.

My little model will have rounded soft ends, as you can see in the picture. I was thinking about using flat straight lines all over, but i think the bent plywood ads much stiffness to the hull. Its easier to bend the plywood than adding stringers and stuff for added stiffness.

Johannes.

Quick and dirty

This is a great inspiration for me. I think complexity and “tradition” is real enemies to low budget cruising.

Johannes.

Hi Johannes
I agree with nearly everything you write. I also think sharpies could be very good proas, simply to build, that means cheap and they do NOT have to be ugly. If you look at Egret you will find her very elegant. And there are or were many more beautiful boats built as sharpies if you have a look at Reuel Parker’s or Howard I.Chapelle’s books. I also think that there is too much search for speed when we talk about proas. As proas are fast by the way they are we could concentrate to search for ways to build them as inexpensive cruising boats and they would still be fast.
My criteria to build Nixe are:
- she must be able to sail in low winds
- she has to have little draft
- she has to have a long waterline
- I don’t need a lot of room
- she has to be inexpensive in building and maintenance
So that is a proa more than any other type of boat.

Building in plywood is a fast way to get a boat. I was choosing the stresform system because I am fascinated by the way it works and can make pleasing forms just by the way it works. A sharpie styled proa has many advantages: less draft, easier to build because you can precut the bulkheads and fit the side panels later, in the extreme after finishing the whole interior. That saves a lot of time and energy.
So I think, sharpies can be very good and beautiful proas.
Alexander

I am having a high gravity day.. The plywood cracks, the glue lets go when i am sanding the chines. Things just don’t go well. It will probably be my worst model so far, but i´m hell-bent on getting it into the water one way or the other.

Johannes.