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Kite-powered proa (boat) collaboration/comments Answered

Added 5/26/07: Please read the comments below to see how the project is evolving. Design specs, goals, etc, have been modified after discussion.

Hi Folks,

For several years I've been wanting to build a kite powered proa. A proa is a kind of boat with a narrow hull and a smaller outrigger. These Instructables are about building a proa with a traditional sail:

https://www.instructables.com/id/ERIIBDCCOTEPUCHZ1K/?ALLSTEPS
https://www.instructables.com/id/EZN8M3OCWZEV2Z7IR5/?ALLSTEPS

These are kite-powered proa-like vehicles for land and ice:

https://www.instructables.com/id/EPKZ5O80HQEQZJI20F/?ALLSTEPS
https://www.instructables.com/id/EPWWSYZNWIEV2ZKLCH/?ALLSTEPS

Goals for the project:

1. Make at least one good boat.

2. Publish a good Instructable.

3. Work with interesting people.

I am definitely going ahead with #1 & #2. #3... anyone interested?

The Boat:

Generally it should be appealing/attainable by as wide a range of budgets and circumstances and skill levels as possible.

a. It should be fun to mess around with starting in about 6 or 7 mph of wind (3 m/s).

b. A beach boat, not an overnighter. Should be able to carry one or two people, a paddle, personal flotation device and maybe a sandwich and a water bottle.

c. Storable in a typical apartment (maybe even a dorm room?). I'm thinking a 2-part bolt-together hull like Wade Tarzia's above. Two halves, each under 8 feet long so they can be stored on end, maybe used as bookshelves as suggested by TimAnderson. What is a typical ceiling height? Mine is about 91"

d. Possible to build on a restricted budget ($200? is that possible? $400?). I'm budgeting about $500 but as a cheapskate packrat scrounger type I am hoping not to spend it all. Should also avoid necessitating rare and expensive tools.

e. It should be possible to make a "good looking" version if the builder chooses.... sort of financially and chronologically(?) scalable. Someone might want to build something as quickly and cheaply as possible, and another person might want to spend all summer working on the fine details and finish. The boat should be worth building in either case.

f. Should be able to take a passenger (is that possible if we rely on weight-shifting for steering?), but be sailable single-handed.

g. Possibly be adaptable to a traditional sail? Would this be hard? This is something I don't need for myself, but I bet someone will ask that question as soon as we publish it. If someone doesn't already have a kite, is it easier to build a kite, or a sail and associated mods to the boat?

h. Probably plywood stitch-and-glue construction main hull, but maybe carved from a couple of Styrofoam billets with a plywood stringer and/or deck? Leaning towards all plywood. If we fiberglass the whole boat can we use 1/4" interior luaun at $9 per 4x8 sheet? Is that more practical and cost effective than something like occume at $60 per sheet with glass on just the keel and joints? We'd need 3 sheets. Need to do some calculations on this.

i. Usable in flat water, chop and small waves (and bigger waves?). Mine will be used mostly at an ocean beach.

j. Steerable by weight-shifting, i.e. moving towards the front or back of the boat. No rudders or daggerboards. Maybe paddle-assisted steering when carrying a passenger/helmsman?

The Instructable:

a. Should be a good read, even for folks who won't undertake the project.

b. Doubles as an Instructable on how to collaborate to make a great project and a great Instructable.

c. Represents everyone involved in the project in some way.

d. Gives the potential builder a rough "how to sail it" as well?

e. Presents the reader with several options for materials and/or construction.

f. All the regular "what makes a good Instructable" things.

The Interesting People:

a. Everyone is interesting in some way or another, right?

b. Some people like to do research on the web.

c. Some people have built boats.

d. Some people some know about wood, or glue, or paint, or kites, or sails, or writing, or...

e. Maybe someone will build the boat concurrently so we'll have pictures of two or more versions at various stages when we publish the Instructable.

Let me be the first to sign up :) I have been using kites to get around fields, beaches, frozen lakes and the ocean for 10+ years. I make my own kite boards and have made my own kites (I use commercial kites now but still love my homemade plywood boards). I've done a fair amount of web research on proas and plywood boats (and some on tarp boats, canvas covered canoes, surfboards, etc.) but I have never built a boat. I experimented with a busted up, rudderless old hobie 14 for a while, but my homemade foot-steerable rudders broke almost instantly, and shortly after that I had to abandon the boat because I moved to a place where it couldn't be stored. It was enough to get me interested.

I'm pretty confident I could build a usable boat as a solo project but I want to see how much better it could be as a collaboration, or at least having a few folks commenting on my ideas.

I have a small assortment of cheap power tools. I've used epoxy and fiberglass a few times and I have some on hand.

I have permission from my lovely bride-to-be to use part of the kitchen, part of the time, as my workshop (that's true love). I also have a small are outside where I can work but I can't leave anything there.

The pictures are my initial hull ideas. For each hull one pic shows the hull from 3 angles and the other shows how the side pieces would fit on two sheets of plywood. A third sheet would be needed for the deck and a fourth (of thicker stuff, I would guess?) for the frames, bulkheads, etc. I'll attach the files for the hulls too. You can get the freeware to view and edit them at www.carlsondesign.com.

The simple V hull would mean less cutting and joining. The other one looks better (in my opinion) and can float more weight with the same amount of plywood.

Could instead go with a flat bottom like Wade's.

Let me know what you think.

Thanks!

Discussions

hi there, I am currently studying at Portsmouth university, for my dissertation i am designing and building a kite boat that can use a old windsurf board as the hulls. It is in similar design to www.lynnkitesailing.co.nz . i would be interested in talking to you about what your doing and likewise help you out if i can. please email me at rage_against_mrclean@hotmail.com thank you and good luck Nicholas Harvey

Here's what the first third of the hull looks like so far. Red frames in the third pic are corrugated plastic, placed there temporarily. I think I'm going to cut the frames down from 3 to 2 on the end sections and 3 in the middle section. There will be a deck for additional stiffness and strength. Any comments on that plan?

part1bottom.jpgpart1side.jpglookingin.jpg

Looks great! The sections seem short -- is this a three-piece design? I missed some discussion, I think, after I cleared out my cookies and the Instructables robot stopped sending me notices of new posts. I like that V-bottom, something I am considering for my 19-foot proa. As far as sections go, I am not the judge. I generally build things too heavily. However, I guess I would leave this as it is in the third photo. The hull will be light enough as is, so don't remove any more bulkheads, which are important in the strength of a thin hull. The gunwales will take a beating, and also help with strength, so consider using a strap of quarter-inch thick oak for gunwales (available in the moulding section of comemricial home improvement places).

Yes 3 sections. I am using 5' x 5' panels. I thought about joining them into (2) 7.5' panels, but it seemed sort of redundant... all that extra gluing, glassing and sawing. I'd probably rather have a 2-part boat, but I think I'll keep it assembled on top of my truck for most of the summer so the extra bolting-together time doesn't bother me too much. I have enough 3/8" for 3 frames per section, so I'll take your advice and go with that. Oak for gunwales sounds good, too. Must say I'm very happy with the bottom shape. It looks very boat-like. Very satisfying to see the form come together while twist-tying. I think it will look better in my living room in the winter than the two-panel design I was originally considering, too. Maybe I'll rig up those deck hatches so that I can mount speaker cones in them for off-season use, heh. Speaking of missing discussions... off topic, sort of, but have you found a way to receive notifications for comments on Instructables and forum topics that you didn't create yourself? In other words, do you have a way of being notified when someone posts something to this topic but not in direct response to one of your comments? I put in a request for that capability but I still kind of wonder if there's an existing feature hiding somewhere.

OK, 3 sections can be good -- more manageable if you travel with your proa --airplane cargo-hold friendly, I mean. Also, the proa's biggest strain will occur in the middle section, so for that you have a one-piece module to distribute the stress better (at least I think that is what will happen). I have an enduring fantasy of bringing a 3 or 4-sectional proa to cruise around the Blasket Islands in Ireland, which I visited once by tourist boat -- fantastically rugged and beautiful terrain, and islands you can sleep on with few problems. Not sure what I did to get automated messages, and what I did to lose them for a while.

Brief update: Frames are cut. Made from 3/8" baltic birch. Frames for the section ends temporarily hot-glued into pairs and planed to the same dimensions. Considering what to use for gasket material between sections. Maybe craft foam? Foam board with the paper stripped off? Thin pink or blue styrofoam? Some kind of weatherstripping? A couple of beads of Great Stuff or sIlicone caulk on one side? Some kind of automotive gasket-in-a-tube?

framesstack.jpgframesstaircut2.jpgframes5.jpg

On my take-apart dinghy I used 1/4" stainless bolts with fender washers and chunks of old bicycle tube as gaskets, which worked well for a while but eventually started to leak. Wetsuit material sounds like it would work better, but what would work better still would be to not drill any holes and instead attach the 2 pieces with stainless draw latches below the waterline. I'll be trying it out this summer and will let you know. If it works I'll put recessed pockets in the hull to reduce drag.

Sorry for delay. I cannot reply to Instructables from my home computer and had to get to office; don't know why this is. Any way, I used NO gasket between my sections. I built "wells" so that the water could leak through bolt holes up to the waterline (so the well-bulkheads are taller than my waterline). In fact, I rarely had more than a couple of inches of water in the wells since the wood swelled around the bolts and sealed off. But I used "real wood", and playwood will not swell like that. Gary Dierking (you have seen his Wa'Apa design I guess) uses wet-suit foam washers on both ends of the bolts, whioch works fine, he reports. If you cannot get wetsuit foam (and my old scuba suit has just about disappeared over the years from scavenging it for foam ;-) you could try sleeping-pad foam from a camp store. You might also try a bead of flexible stuff around the edge of each bulkhead (silicone or polysulfide boating sealant) but I do not know how evenly it would compress once you tighten the bolts (try a test section?)

I think I have a couple of old wetsuits around, mostly unmolested thus far. That sounds like a good option. I've been to Dierking's site, but I don't remember seeing a split hull design... I'll have to make a visit there tonight, and one to your site. I suppose if I made wells small enough I wouldn't have to worry about this, but one reason I wanted to go with a sort of sealed hull was that I won't have hands free for bailing. Also thinking that my waterline might be pretty close to the gunwales if I take a passenger.

Reply to myself ;-) I really did mean "plywood" and not "playwood" but the error makes an interesting subconscious slip, perhaps! Also, note that my wells were rather large to be used as wet storage for anchor and line, or even to keep canteen cool. Also, I could put a paddling seat on top of one of the wells: no wasted space! But the wells can indeed be made very small, just large enough to get your hand/wrench in to tighten the module bolts. Also, you can fill a large well with foam flotation, and then you have option to make well a wet storage and a support for a paddling seat, etc. Look at a top-down photo of my old proa in the "proa comparison" photo, which I think I posted at wtarzia(dot)com on the photos page. I say 'think' because I had some trouble updating my site and I now have to check if the changes went through. I can just e-mail the photo though if you send private e-mail address to wtarzia at nvcc dot commnet dot edu.

Wow, that would be a dream... sounds like the perfect mission for a folding skin-on-frame proa! Next Instructable :)

Looking good! I like the hull shape, nothing too radical so should work well. I'd definatly go with at least some deck, it will increase torsional stiffness, the lack of which can be a problem in lightly built, narrow hulls. Perhaps you could deck over the bow sections and leave the centre section open for foot-room. Beefier gunwhales in non-decked areas will help stiffness a bit.

Here's my rudder control idea. This of course means the boat has to tack or gybe instead of shunting. Pilot would sit on the platform or in a long sling seat next to the hull. If it turns out that the pilot can sit on the same side of the hull on both tacks then the hardpoint could be offset or control bar could be angled for comfort. The hardpoint could be a simple hook. The rope could be a length of webbing with a ladderlock adjuster like we use on kite bars. Concerns: Bar will be able to move side to side somewhat. Will this cause problems? How will the bar be elevated off the deck? Controls seem too coarse... small foot movements, large rudder response. Could the control lines be moved inboard on the foot bar and not interfere with seating? Possibly run through tubes on deck between platform slats? No, that would make setup too complicated. Maybe just go between closely-spaced slats without a tube.

rudder.jpg

My only worry here is, if this is going to be a tacking proa, that short ama might trip the boat on the ama-to-leeward tack.

Hm, good point. That drawing was not really to scale but your comment makes me wonder what I should do with the ama... when I was considering the two part hull I thought I'd make my ama the same length as the hull halves, but now my 3 sections are just under 5 feet each. I could go with the original 7.5' ama, or try to get away with a 5' one, or make it a two-part 10 footer. I wouldn't dare go as short as 5' for the akas, so I'm going to have some parts longer than the hull sections anyways. I'll think this over. Do you think it's worth going to 10 feet?

If it will be a tacking outrigger, I would think you want the forward part of the ama to reach to the front of the main hull. This helps prevent tripping, which could result in a capsize or even a pitch-pole (!) I suppose, if the boat is light. You can still have a short ama; just move its attachment points back. Also, you might want the ama shape to be fuller in the fore part (look at Gary Dierking's ama on his Ulua outrigger).

I think the boat will be pretty light! I haven't filleted and taped the insides yet, and of course it will gain some from the full fiberglass sheathing, but right now it's a featherweight :) I wired and gap-filled the center section this weekend and finally got to line up all three pieces. Very gratifying! I'm still not 100% sure what to do about the ama. I think I might get a sheet of 2" styrofoam and make one 6" high x 8" wide x 8' long with a thin plywood stringer. I want to try to keep the akas on the center section and the ama symmetrical if possible, just to keep the configuration options as flexible as possible after completion. I want to test it as a shunting boat before I go ahead with the rudder plan, just in case, tho I'm not too hopeful. What are your thoughts on a flat-bottom ama with scooped ends... something that could act as a planing hull at higher speeds?

I have yet to try a foam ama, but I am going to try one sooner or later. My latest ama was like building a whole second boat, and I am hoping that a foam ama would take way less time (of course, I've been wrong about such things before ;-) If you are not going to shunt like a true proa, I would consider again an ama as on Gary Dierking's Ulua. But if you think you might experiment later with a shunting proa, then you are right -- keep options open with a symmetrical ama. Just make sure it won't be pulled under. You kite people often get into those high-horsepower kites, which would overwhelm an ama that would otherwise be perfect for a shunting Pacific proa. ;-) How big is your kite?

I have a bunch, various sizes. My most powerful is a 13.5 square meter C-Quad, and my smallest is a 1.4 m buggying foil. But I think the kites I'll use most often for the boat will be an 8.5 meter C Quad, an 18 m Phantom, and maybe a 13 m Scorpion. The 8.5 is the most powerful of those three. Much flatter, and they also used a different scheme to measure them (projected area while flying rather than flat area when laid out on the ground). I still wonder if there's some practical way I can rig up a steering paddle instead of a rudder and switch it from end to end while keeping the kite under control. The kite can be steered one handed, and the Phantom and Scorpion are pretty stable even with hands off the control bar for a short time. Hmmmm.... Do you use a paddle to steer yours? Do you have some kind of oarlocks, or do you just rest it against the gunwale?

What size would you recommend for me to get to practise with but still perhaps large enough to attach to a boat for down-wind or reaching in a good breeze? I ask because I am writing an SF novel featuring kiteships (see the 3 chapter sample on the press release page at kiteship.com -- Dave has been a big help with the techno details) and I ought to fly a practise kite just to get a handle (no pun) on the basic mechanics of it. But if possible, I would like to try it small-time on my outrigger. Perhaps I am asking the impossible, but I have to try ;-) As far as steering, you are on your own there, I haven't a clue as to how to make that work if you insist on clipping your body in to a large kite ;-) For my own steering, I just shifted my body weight. I freaked out the sailboat guys on the ramp. "Where's your rudder?" they often asked. I'd reply, to have some fun, "Why add weight to the boat with a rudder? Just move your body, since you already have to bring that with you," and then I'd push off and go sailing. You can borrow that reply if you want. But seriously, I needed a paddle for downwind sailing, because the outrigger and crabclaw rig conspire to turn the boat, with large forces, and you need a paddle for aft and quartering winds. I just kept a canoe paddle on board for that (kayak paddle also for paddling, steering paddle as back-up to that). The longer the better, though. I used the paddle to double as a lee-platform to sit on (handle wedged under gunwale) and lift ama out of water during light winds (reduce resistance of ama). My new outrigger will begin as a tacking outrigger, and I will try an Indonesian-style side steering oar as shown on Tim's website on the Lepalepa link, etc.

Do you want to make a kite or buy one? The classic cheap homebuild starter kite is a Nasa Parawing, a.k.a NPW5. Aerohydro mentions one in his land proa instructable, I think. Very easy to build, relative to your other options. They pack down very small and have decent steering and good power-for-size. I would think a 3.5 or 4 meter one would be a good starting size. A search for NPW5 or NPW would get you to the right places for more info. However, for not a whole lot more money than the cost of building one, you could probably find an OK used 4-line-with-handles buggy kite or a pump-up kiteboarding kite that would far outperform it in terms of efficient beam reach and upwind travel when connected to a boat/buggy/skis/whatever. There's a lot of information and free software on the net for making foils and you could probably find most of what you need to build an inflatable leading edge kite right here at instructables. For an inflatable-leading-edge kiteboarding kite, I would say something like 11 m would be good, roughly. For a four-line foil with two separate handles, something in the 4-5 m range would be good for starters. I think one of those kites in 8-10 mph would move the boat around a bit without being crazy. You'll want something bigger eventually, if you become really interested. A decent 2 m trainer would give you a rough feel for the mechanics. If you build, you'll want to find some 1/2 oz spinnaker nylon or the like. A light poly tarp MIGHT work for the NPW5 in a good wind, but I don't think it would work for much else. Also avoid the sewing shop nylon. Kitemaking fabric should be almost like paper - crinkly with no stretch on any axis. Let me know if you want to go that route and I'll find my old cheap fabric links for you. If you're ever in Portland, Maine, on a nice day you'd be welcome to try any of my kites. It is a lot easier if there's someone around to show you the basics :) Maybe you can write off the trip as a business expense :) I'll take a look at the book sample soon, I hope! I'll revisit Tim's site too. Always nice to have an excuse to go there.

Well, on second thought, you could rig dual rudders, perhaps just in front of each aka attachment point. The tillers would have a "neutral lock position," so that when the forward one is locked, it is acting as a leeboard and the rear one is used for steering. On a clever day you could add a transverse part to the tiller so that you might steer with a foot when the kite needs your attention. (I often steer my dory with a leg over the tiller when I need jib and main sheet in hand). But you can always keep both rudders locked on a straight course and just slide your bum to trim, with hands on the kite bar. Dual rudders seem to be a common solution to proas nowadays, for those insisting on rudders (see Rob Denny's commercial Harigami Proa (also called "harry proa") designs). I am in fact thinking of solving my rudder and leeboard issue with two Balinese-style side-rudder-paddle thingies, so that if I decide to go back to shunting proa, I am all set (also, I need only design once and build twice; am so tired of designing and building, want to get in water!)

Hm, that's an interesting idea. The Peter Lynn Kitecat uses opposing rudders. I'll meditate upon this :) Maybe try to do some sketches. Ideas are beginning to form.

Oh, forgot to respond to your actual question: and the answer is....I am out of my depth at this point. Intuitively I say, do not go shorter than 7.5 feet. I think 10 feet would be good too, perhaps better. But now the ideas of skin friction drag vs wave making drag come into play. At different speeds, the hull length (wave making drag, function of length of wave created, or the "hole" the boat digs for itself in the water and at some point cannot climb out of unless it is a planing boat) or the skin friction (skin drag, total skin area exposed to water) switch places in importance but I forget the arguments. I think at typical small boat speeds, skin friction predominates. But then, an outrigger has those other variables (such as enough buoyancy to keep the ama above water on the ama-to-lee tack). I feel sure Tim Anderson could answer this question better since he has the tech background and has played with a lot of outriggers.

Forgot to mention that the length adjusters are in there so that the pilot isn't forced to sit in a position that doesn't work well... it couldn't be adjusted on the fly, but it would allow us to find the best spot to sit and make changes for different conditions.

Thanks! I'm planning on a full deck with no footwells. I'm presuming that weight shift steering won't work, or at least planning for that contingency, and my rudder control scheme requires that my feet be up on the deck. I'll post a sketch of that idea soon. I think I'll glue stringers to the deck or have a rigid platform on the akas that extends across the center section. I glassed the external seams on the first section today and hope to do the inside this afternoon.

I started cutting and dry-fitting pieces of the main hull this weekend. So far so good... pretty exciting to see some of the pieces wired together and forming a nice hull section. I'm not sure how to align the bulkheads/frames for each sections well enough that there are no funky bends where the sections meet. I might eyeball it or maybe I'll prop the sections up so everything's aligned correctly and use a plumb line to mark the final placement of the bulkheads. At this point there is extra wood on the connecting ends of the sections that will be trimmed off after the bulkheads are glued in.

I have alighment issues myself. Partly, I blame my thick glasses -- I cannot see anything straight except for a tiny 'sweet spot' in the center of my lenses, so I have to double check everything with a steel straight-edge. Even then I still make mistakes when I forget my 'handicap'. My new V-ama has a very slight curve on its 'keel' that I discovered after the glue set! (I could exploit that on a proa, not not on a tacking outrigger as well. Probably I will not notice difference). So if you wear glasses, triple check! ;-)

If you look closely at the first photo, it looks like the end is slightly twisted. I'll have to check that. Definitely didn't notice it up close. So maybe in addition to wearing our glasses (only need mine for reading fine print so far) and checking it on the straight edge, we should make a note to step back every once in a while and look at the big picture :)

Yes, absolutely, step back! That is always when I see these things.

Sounds like a great project! I'll be following along. You do set up some tough parameters -- a 'do everything boat -- but that's OK as a goal. The end product will instruct about tradeoffs necessary, but it seems good to let the instruction happen rather than limit yourself with imagined limitations. Does that make sense? For starters, I think a round-bottomed hull is best. If you want the boat to do a lot, I think you need to start with the maximum efficency hull: max-buoyancy/strength for minimum skin friction, etc. Flat is faster to build, is all. I applaud any design meant to store in a dorm room! I wish I had that ambition when I a young feller in college. Build a mock-up of the hull profile in cardboard or a "wire and duct tape" mock-up, etc., and make sure you can store it and move it around its intended home, though. If you are an engieering cool-dude I guess you can do that in CAD or something, but realizing the mockup in living terms wouldn't be bad. Two-piece design, yes. Now, shall it hinge in the middle or be in totally separate parts? Separate parts can be used as aforesaid storage thingie. But are you really going to empty it our and use it when you suddenly see that paddling/sailing might possible on a warm December day? Think 'global warming.' Sailing might be done any time now ;-) So decide if using it as storage niche is feasible. If not, and if you build it very light (skin-on-frame?) then hinging it would speed up your set up time a little. But....perhaps harder to transport as a unified bundle? -- who knows how it might be carried? Like suitcase, a backpack, behind a bike, with buddy.... the drawbacks of hinging it become evident now. I'm not an expert, but I do recall all my many mistakes and "I wish hads" and so on. But "light and round" I'll stick with. I'm in the middle of my second proa (flat bottomed again) for trailering but I keep thinking about yet a third that would hinge and be very light to stuff in my new Ford Focus hatchback somehow for short sessions. (Really, I guess I just want a boat for each day of the week...)

Thanks for the comments! Glad to have you along at least as an observer and I hope as a continuing contributor now and then as well. I follow you on the round bottom, but it seems like a lot more work... I made small (about 20") model of the V hull and it looks pretty good. I'll post a pic soon. But the large wetted surface area does make me think more about rounding off the bottom. I'm not a sailor. I know that round is faster, but I don't know if it's a lot faster or just a little faster. What do you think? I want to try to avoid rudders, daggerboards, etc, if possible. Can a round bottom boat track well enough to weight-steer and not use a daggerboard? I wouldn't rule out a boat with one, just would like to avoid it both for simplicity and practicality for beach launches and shallow water. I just saw some photos on the web of a kayak that was skinned in Dacron sail material. I also just yesterday went to an art show at which one of the exhibitors had a more traditional western sailboat skinned in Dacron. I've got a few rolls of that around from the days when I thought I wanted to make inflatable kiteboarding kites (later decided I didn't want anything that had to be pumped up). I think I have enough to do a whole hull. But designing and executing a frame to stretch it over sounds tough. It would be very light though. The 17 foot kayak weighed something like 27 pounds. I'm not sure how flexible the fabric would be once it was coated with polyurethane (or whatever I'd have to coat it with) but wouldn't it be great if it was car-trunkable instead of car-toppable? I'll have to do some research on that. The Dacron sailboat was really pretty. I'm not going to have the opportunity to test how it fits in a dorm room - those days are gone for me too. But I would love to think that some college students might want to try building it. Full size mock up... hm... I'll have to keep an eye out for a few refrigerator boxes :) Hinge, interesting idea. Maybe a hooked hinge that engages an oval pin in a way that it can't come off when the boat is "deployed" but can be unhinged easily at a certain angle. Or possibly just a regular hinge and take the pin out when necessary. Working through the tradeoffs will definitely be a major part of the project. I'll post the results of my Dacron research as soon as they're in.

Dacron is available in heat-shrink form. That's what the boats I saw were covered with. The Dacron I have is the normal kind, I guess. I played with a piece tacked to a yardstick. Ironed it at gradually increasing temps 'til it melted. No shrinkage. Everything I've found on the net so far about Dacron-skinned hulls talks about the heat shrink kind, but I think I'll keep the stuff I have in mind as an option for something... maybe use it on the outside of a plywood hull instead of buying fiberglass. Or maybe sew it to close tolerance and nail or staple it to a frame.

Ballistic nylon is also used, coated with something (polyester?). Go find a recent-ish Wooden Boat article (about 6 months ago?) where the author builts a ~19 foot cruising boat fort two and cruises it down the inside of Baja. The article convinced me that nylon is a good choice.

Cheaper, yes, and the Irish build those tarred-canvas curraghs, which work well. Ballistic nylon would resist tearing better than cotton canvas, I think.

Yeah, canvas is/was a popular covering for canoes as well. I'm with you on the nylon... tough stuff. I'll check prices and post back soon. Do you recall if the nylon was pre-coated? Like backpack material usually is? Or did the builder coat the nylon after it was on the boat?

I do not remember the nylon being precoated. I believe it was a two-part polyester (I could be wrong, will try to find that issue of WB tonight). In any event, if you buy canvas, be sure to wash it thoroughly first, because sometimes canvas is treated with presevrative stuff that prevents the coating from sticking to it well.

Yostwerks has a vast gallery of skin on frame kayaks. There are a lot of boats based on the same few plans but with all kinds of variations. Different skin and frame materials, folding or permanent, even a couple of inflatables that you'd never know were inflatables. A lot folks on that site seem to favor pvc/vinyl coated polyester called coverlight or shelter-rite. Looks like it's about $20-25/yd. This is the section on skinning. They just use glue, no sewing, except on boats that need a zipper on the deck for disassembly.

One supplier charges ~$20 per yard for ballistic nylon (the yard is 36" by 60"). So about 120 dollars for a 16 foot proa hull?

I found some 1050 denier ballistic for $15/yd here.... seems do-able. Plywood skin would be about the same price, just for the plywood, not counting the epoxy, filler & tape. 1/4" marine fir is $40/4'x8' sheet. We'd need two sheets for the sides plus one for the deck (if we use a full deck), plus a half sheet or so for the frames/bulkheads. A gallon of epoxy would be about $50, or about $15 for polyester resin. 4" wide fiberglass tape is $25/50 yd. roll, 1.7 gallons of cabosil filler is $22. If we decided to sheathe the whole thing in 6 oz glass cloth that would be another $36 for the fiberglass (might need another gallon of resin, too). Then there would be twist ties, nails, cable ties or whatever.

So, about $300-350 for the vaka sans fittings from fir, epoxy and glass.

If we wanted build a disposable/experimental version we could do it from 1/4" luaun @ $9/sheet, polyester resin @ $15/gal, $25 worth of tape, $25 of fillet filler (or use sawdust for free?), skip the sheathing, grand total about $100.

Any ideas about what we could use for the frame of a skin-on-frame boat? The kayaks I've seen on the web seem to use aluminum tubing or cedar or ash. I wonder how the average builder would get the materials.

That's the big question! You need clear stuff if you go with wood. Cedar is light, ash is tough but heavy. I have NO idea what it costs to buy that.

I just sent an email to one of the local "good wood" dealers that sells ash. Asked what it would cost to have ash stripped to 1/8" thick x 1 or 1.5" wide. In Maine a lot of baskets are made of ash. The icefishermen around here carry packbaskets like this made of ash strips. Maybe I should get in touch with a packbasket factory. The rim around the top looks just about right, don't you think? Abenakis traditionally made strips for the baskets by pounding on a board cut on the radius of the log until the wood separated along its growth rings. But those would be too thin, I think.

Thanks for the invite. I'm very interested in helping out with the kite boat. I just got into kiting a year ago, but I've got a good amount of fiberglass and boat building experience. I'll send you a message with some contact info.

Excellent! Thanks for the reply. I just revised my hull design last night with a more vertical stem so I can mount a rudder. I think I'm giving up on the whole weight steering idea and make it a tacking proa instead of shunting. I'll try to post some screenshots from the hull design program tonight or tomorrow. Have you ever done any stitch and glue boat building? I have most of the supplies for it now, at least enough to get started. I'm comfortable working with epoxy and fiberglass and I think I can handle it, but it will be a learning experience for sure :)

Most of the work that I have done has been with fiberglass and foamcore. I've repaired my grandmothers sailboat transom, that boat was constructed with the stitch/glue method. Thats pretty much the extent of my experience with stick and glue. Never built a boat from scatch with that method or anything like that.

Cool, I think that will be pretty helpful. I haven't been around boats that much except my dad's power boat which is a whole different kettle. Are you around Portland these days? Here's the new main hull design... let me know what you think.

proa4.jpg

ya im in portland for summer break. shoot me an email if you ever wanna work on this boat or w/e

It's just under 15 feet long and 15 inches wide.

I picked up 4 sheets of 5' x 5' x 1/8" 3-ply baltic birch this weekend at $15/sheet, plus some pine for the stems, some zip ties, and some collodial silica epoxy additive for filleting putty. So it looks like this version will be stitch and glue, but I still like the skin on frame idea for a future incarnation.