Kite-powered proa (boat) collaboration/comments

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:


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


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.


Picture of Kite-powered proa (boat) collaboration/comments
sort by: active | newest | oldest
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
flywoodkb (author) 9 years ago
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?
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).
flywoodkb (author)  Wade Tarzia9 years ago
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.
flywoodkb (author)  Wade Tarzia9 years ago
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?
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?)
flywoodkb (author)  Wade Tarzia9 years ago
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.
flywoodkb (author)  Wade Tarzia9 years ago
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.
flywoodkb (author)  Leon Close9 years ago
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.
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.
flywoodkb (author)  Wade Tarzia9 years ago
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).
flywoodkb (author)  Wade Tarzia9 years ago
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?
flywoodkb (author)  Wade Tarzia9 years ago
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.
flywoodkb (author)  Wade Tarzia9 years ago
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!)
flywoodkb (author)  Wade Tarzia9 years ago
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.
flywoodkb (author)  flywoodkb9 years ago
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.
flywoodkb (author)  Leon Close9 years ago
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.
flywoodkb (author) 9 years ago
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! ;-)
flywoodkb (author)  Wade Tarzia9 years ago
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.
Wade Tarzia9 years ago
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...)
flywoodkb (author)  Wade Tarzia9 years ago
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.
flywoodkb (author)  flywoodkb9 years ago
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.
flywoodkb (author)  Wade Tarzia9 years ago
Check these two Instructables about coating canvas with liquid latex. Could be a useful technique/material. I bet cotton canvas painter's drop cloths would be a lot cheaper than ballistic nylon.



Cheaper, yes, and the Irish build those tarred-canvas curraghs, which work well. Ballistic nylon would resist tearing better than cotton canvas, I think.
flywoodkb (author)  Wade Tarzia9 years ago
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.
flywoodkb (author)  Wade Tarzia9 years ago
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?
flywoodkb (author)  Wade Tarzia9 years ago
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.
flywoodkb (author)  Wade Tarzia9 years ago
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.
tylerars249 years ago
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.
flywoodkb (author)  tylerars249 years ago
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.
flywoodkb (author)  tylerars249 years ago
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.
ya im in portland for summer break. shoot me an email if you ever wanna work on this boat or w/e
flywoodkb (author)  flywoodkb9 years ago
It's just under 15 feet long and 15 inches wide.
flywoodkb (author) 9 years ago
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.
flywoodkb (author) 9 years ago
Made a new model this weekend. This is 1:8 scale of a 15' hull with chines. I put a few more details on this one. The seating slats are under the akas and support each other with lashings. The akas are lashed to the vaka. I also tested it in the tub. Maybe not the best testing grounds but it was useful. The boat seems to track pretty well, which is nice, but regardless of how I moved the weight and tow point on the boat I couldn't make it turn well. When both the weight and towpoint were far back, the stern dragged around to "windward". Other than that, it pretty much just went straight. The crud on the side of the hull is leftover plastic and hot glue... I skinned it with plastic but peeled it off for the photos. I taped on a rudder made of aluminum flashing and the boat was much better... turned well in both directions. I think I'll do yet another redesign with a more vertical stem so I can attach a rudder and go with a jibing, foot steered boat if I need to... and based on my bathtub tests bet I will need to.
Wade Tarzia9 years ago
OK, I see now. I must have read too quickly -- you are going to have your hands full with the kite, and want to just shift your butt along the hull to weight-steer. A V-hull is probably good for that in the one sense: it will track quite well. My proa is a square-bottom, rockerless hull, and it tracks very well too. A narrow hull will sink pretty well (my draft is 8 or 9 inches, single crew, ~12 inch bottom width, 22 inch max beam, and a very heavy construction DF planls, marine ply, heavy scantlings all around, the typical first-time boat builder mistakes ;-). The boat tracks as if it is on autopilot, and I have sailed an hour straight just gripping the sheet and sliding my butt 6 inches back and forth to trim steering. Of course, a V-hull will track even better, but will it track too well? I have no experience with kites so I don't know what they need for sailing course control. Is extreme powerful tracking the best? Does the kite to wild things sometimes that requires fast hull response? It will be very different from a kite board, the opposite I should think. Try to get Tim Anderson's comments as he has traditional proa, kite-boarding, and kite-sailing-boat experience.
flywoodkb (author)  Wade Tarzia9 years ago
If the wind is light but gusty it can be nice to have quick steering to veer breifly to windward and give the kite a sort of a momentary wind boost if it starts to fall out of the sky. Beyond that, i.e. if the wind is steady or gusty but fairly strong, you can pretty much park it in the sky and just ride.

I wonder how taking off from the beach (and shunting for that matter) work with slow steering. In a buggy (three-wheeled beach cart with foot steering) or on a kiteboard you tend to take off pointing a bit down wind and cut to a crosswind or upwind course before you gain too much speed. Maybe with a displacement hull that's not such an issue.

There's not a whole lot of sheeting control in a kite. There is a bit of power adjustment but I don't think as much as a sail. My guess would be that as long as we were shunting and not tacking or gibing that fast steering would not be as important as tracking. Maybe someone who uses both can help us here.

I sent Tim an invitation to comment here. I've been looking at the photos from his New Zealand trip here. Great stuff. I love his other travel logs, too.
If Dave Culp is on Instructables, you might ask him too (but I don't think he is; I can ask for his ideas and permission to copy them in here). He is one of the owner/organizers of a commericial and sporting kite-sailing corporation and has over 2 decades of kite sailing experience. (See www.kiteship.com)
flywoodkb (author)  Wade Tarzia9 years ago
I've emailed Dave a few times... long time ago. As I recall, he's the one that talked me into getting the old Hobie (wish I still had that thing, especially after watching that video radiorental linked to). He had some great stories.
I asked Dave about tracking vs. less-tracking (round hull vs. V-hull), and he seemed to think that it is a matter of taste: some people like fast-response kite-hulls, others like good-tracking hulls, and all hulls can be made to turn well anyway, especially if they have rocker, and you can put a lot of rocker into a deep-V hull.
flywoodkb (author)  Wade Tarzia9 years ago
I found Dave's old dcss.org site last night and there are some photos of his 3 kite proas ( ...or 3 of his kite proas?) . His are set up with a kite connector on the ama, and the boat is sailed with the ama on the leeward side. I couldn't tell if there were rudders, but it didn't look like it. I sent an email to ask him about the specifics of his boat, and also to see if he'd be willing to take a look at the proposed hulls in the original post above.
I think he favors foot steering.
flywoodkb (author)  Wade Tarzia9 years ago
Hm... did he build his boats to just go one way, basically? The photos show no place to attach a rudder to the leading end that I can see.
I don't know, I've lost track. He's built an awful lot of boats over the years, and I don't know if he used that method or has come to that conclusion after trying many methods. I know nothing of kite-sailing (though I better learn soon, since am writing an SF novel about it ;-) but unless you are steadily cruising in fairly open water (no need to maneuver around other boats) I wonder how doable the body-weight-shifting steering method will be? It is worth a try though because you can add a rudder if need be (the joy of building your own stuff: experiment!).
flywoodkb (author)  Wade Tarzia9 years ago
That's what I'm thinking. Build now, modify later :) I 'm itchy to get building. We've had the forum topic up for a long enough time that probably anyone who'd comment has commented. I haven't heard back from Dave Culp (maybe he doesn't check his dcss mail anymore?) . I think this weekend I'll start finalizing decisions for the main hull at least... maybe go buy some wood too. Steering is my biggest concern at this point. I'm not worried about the whether it's a top performer speed-wise but really awful steering would take all the fun out of it. I've been thinking that foot-controlled rudders might be the way to go, but it would be much easier to implement them on a catamaran than a proa. I think I might use baltic birch plywood. It's not an exterior glue, but I've used it for kiteboards for years in the 9mm 7 ply... they last about 3 years with just a layer of epoxy on them (no glass). It comes in 5' x 5' sheets, 3mm, 6mm & thicker. 6mm is $18/sheet, 3mm is $14. I would probably trust the 3mm birch more than 6mm lauan. I like the skin on frame idea, but for a prototype that might or might not work, I think I'll go with cheap plywood.
Leon Close9 years ago
Thanks for the invitation to contribute. I don't have a huge amount of spare time at the moment but I'll be following any progress. I agree with most of what has been said so far, particularly the need to attach the kite lines to the leeward gunwhale or lower. An attachment point on the fore/aft centreline would be simple but I have visions of the craft being pulled broadside downwind due to weather helm. I think you may be underestimating the value of effective steering. I have sailed a proa very similar to Wade's and while weight shift certainly works, I doubt it is responsive enough to meet the demands of kite power. Weight shift steering is often supplemented with a hand held steering blade, but with a kite, your hands are full. My main advice would be to make use of those who have gone before you. Skin on frame hulls have been refined for a variety of purposes and one would lend itself to construction in a limited space. I'm sure kite powered proas have been done by Dave Culp and others and I would not underestimate the value of that wisdom.
flywoodkb (author)  Leon Close9 years ago
Thanks, glad to have you following along. See my reply to Wade about the gunwale attachment. A plain old hook in the center would certainly be easier to implement, but if the pilot needs to be able to move his weight around the pulleys and ropes would still be needed (right?). I'm worried that I'm underestimating the need for responsive steering, too. I really feel like I need to get something in the water and give the weight -steering thing a try. Dave Culp once suggested to me that I try kitepowering a canoe with a paddle clamped to the side as a centerboard/daggerboard/whateveritscalledboard. I think my father still has a canoe. I'll see if I can give that a whirl. Wade just reposted some info from Dave Culp below as well, but maybe I should send him screenshots of the V hull design and see what he thinks about the specifics. So, another vote for skin on frame, eh? I do like the sound of it.
radiorental9 years ago
Another thought. The further you are from the waterline the more you will work to propel the boat. When I was powering the outrigger I first sat up in a seat, after getting lofted a couple of times I sat right down in the hull and was expending -no- effort what so ever, it was a little surreal frankly. Boat was powering along as before. I figured it had something to do with lowering the 'center of gravity' or whatever the correct term is here. I've got a gut feeling you'll hit some issues with your current seating arrangement. I personally would look at an attachment point near the bow, a four line pulley of some description with a QR. Then you can focus on placing your weight correctly without adversely affecting this 'center of gravity'
When you are sitting up holding the kite, aren't you creating a moment arm, and thus it is harder work on the human (who becomes 'the human lever')? Why can't the line be attached to a slide on the gunwale, and you control the rope's COE from that ideally low position?
flywoodkb (author)  Wade Tarzia9 years ago
I think it would be possible, but complicated.

Take a look at this photo. The rider pulls the left end of the bar to make the kite turn counter clockwise, right to spin it clockwise. The bar also slides (on the center line) toward the rider to increase power and is let out to decrease power. Travel is about a foot. The clump of webbing on the center line near the top of the pic is another power adjuster. At the bottom of the center line is a loop that hooks into a steel hook on the rider's harness. The rider is constantly sliding the bar on the center line to adjust power, and constantly steering the kite by pulling just one end of the bar or the other. The strap is used less often. Somewhere in the system is a safety release that, when activated, disconnects the bar from the harness, throwing slack into 3 of the lines and leaving the kite flapping on the 4th line with no power.

Sliding the bar in and out is probably not *as* critical on a boat but one would definitely need to be able to pull the bar ends for kite steering.

I think for the shuttle-on-a-rail idea, we'd need to have some kind of slotted or channel-shaped metal bar screwed down to the gunwale, then make the shuttle, which would need to have at least a couple of bearings in it to make it roll smoothly under high pressure. The shuttle would have to be (in my mind at least) a bar about 18" long with a pulley on each end and a hook or clip in the middle. The shuttle would need to be restricted from twisting by being hooked to the rail in two spots. The kitebar would attach to the shuttle by hooking the regular kitebar harness loop to the shuttle hook. A rope would run through each pulley to the kitebar ends. The kite would be steered by pulling the ropes. Using this mechanism the pilot could sit anywhere on the boat and still have control of the kite. A quick release shackle would have to be incorporated somewhere in the system and a leash/ripcord would be attached to the pilot to release the shackle and detach the kitebar from the shuttle if the pilot went overboard (not sure how this would work with the ropes/pulleys arrangement. Seems like there's too much potential for tangles to prevent a full release).

The problems with this system are: complicated and expensive; could be difficult to attach the kitebar to the shuttle after the kite is launched; if the rider goes overboard he has no kite to help him get back to the boat; if a kite steering mistake is made, the boat could easily be turned over, rather than just lifting the pilot out of the boat; the pilot would have to be sure not to drop the ropes!; ...etc.?

Can anyone think of another way to do a gunwale attachment?

Wearing a seat harness, sitting on the deck, the kite's tow point would be about 10 or 12 inches above the deck. If we sling the seat/platform/trampoline under the amas, it would be even lower. My hunch is that the small difference in moment arm (small relative to a sail, anyhow) wouldn't be the major reason to attach to gunwale. I'm more worried about the placement of the center of effort (or whatever it's called) on the bow/stearn axis.... whether the boat is being pulled by the nose, the feet or the waist :)
flywoodkb (author)  radiorental9 years ago
Maybe I could put a curve in the akas that would lower the seating slats to below the deck of the boat on the windward side... or somehow make the seat height adjustable, like a kite buggy webbing seat, so I can hang my butt over the windward side. The attached pulley idea probably wouldn't work in this case, since the boat doesn't really have a bow and a stearn. Maybe a rail could be built that the pulley assembly would ride on to get from end to end when shunting, but it seems complicated. It sounds like it might be a good idea to build the hull without permanently attaching the deck (maybe just screw it down) and with a hasty aka/ama arrangement just to test how (or if) the boat's going to steer before I put much finish work into it, then if it seems feasible, finish it off. I suppose if it doesn't work out I can use my vaka halves as the fronts of catamaran hulls :) Or just give in and put a sail on it :)
Or suspend the seat under the akas to keep butt low and to windward?
When I say center of gravity I'm talking about the static center + variable offset from kite force.
radiorental9 years ago
I wont be able to help with this project, I've got a trimaran kiteboat project in the skunkworks at home, similar to the peter lynn but with two small outriggers and an old pintail surfboard for the center.

However I have flown a kite in an Hawaiian outrigger which is very similar to the setup you suggest.

Some points to note. Kiter sits forward, DO NOT harness in to boat or to boat.
The majority of labour is in steering surprisingly. We were steering in the traditional fashion, might be different with a rudder.. but its a lot of work.

Like so

You probably want to lash your iakos directly to the amas, I would avoid the extra struts you put in to your prototype. Composite up your iakos and put an s-bend in them to reach down to the waterline. The hull should lean slightly to the ama side anyway.
You should consider making room for a 'monkey' (third person to bail water and trim ballast). While I had no problem driving a four man in 10mph winds, with the ama windward... I can easily see how you need ballast out on the ama if you're clipping along.

I also agree with Radio about lashing the akas: very flexible and strong, and can be faster than bolting with a good set-up. My akas on first proa fit into a T arrangement on one side of main hull (vaka) and lashed on the other side, ending in the standard boating cleat. This is way faster than bolting the way I had it. The T also helps fater set up because you are just jamming the aka in there, locating it for lashing. The T also takes lateral stress if ama is to leeward.
flywoodkb (author)  Wade Tarzia9 years ago
I have something in mind for lashing the akas to the vaka. I'll try to whip up a sketch or model tonight and post it here. I think I can picture the T arrangement. Were the akas tubular?
No, the akas were crude relatively knot-free (emphasis on 'relatively') DF 2x4s planed vaguely ovalish (emphasis on the 'ish'). They lasted, and perhaps I was only lucky that they did. The T was just a heavy bolt captured by a T nut (inside the watertight compartment) with an oak piece 'crossing' the T (with wide washer under bolthead). Worked well. I cut an open-ended slot in the 2x4 akas. I think you can see it in one of the photos in my proa Instructable.
flywoodkb (author)  Wade Tarzia9 years ago
Ah... ok, I understand now. I printed out patterns for another model tonight but I'm probably not going to have time to put it together 'til Wednesday or Thursday. I hope to make this one a little more detailed and incorporate some of the ideas we've been talking about.
flywoodkb (author)  radiorental9 years ago
Thanks, great info, and very inspirational video and photo.

Laminated outrigger arms sound fairly do-able and they would look better too.

I'm probably going to sail single-handed most of the time, but I will see if I can design the hull so that it works with one but can also sail with 3 if necessary. Seems like a tough design challenge.

Here's another fun kitesailing video:

All these are "turn around at the end of a run" types... gibing instead of shunting.

Good luck with your trimaran, hope we'll see some pics (at least) when it's done!
I should look at your project: Tim gave me a "flat" 12 foot kayak before he moved to CA (one for running rapids and doing stunts, I guess: it seems meant to kneel inside rather than sit), and I had just that very idea, a trimaran or tacking outrigger with foam/glass amas like Gary Dierking's designs. I was wondering if the akas would be too low on this very very flat kayak hull, thus be constantly interfering with the waves. (a little off this topic, sorry).
flywoodkb (author) 9 years ago
Here are some photos of a hastily constructed model of the V hull option. Hull material is foamboard/foamcore with the paper stripped off. Deck and akas (outrigger arms) are chopsticks. Put together with hot glue. Hull panels are scaled down from the Hull program in the original post, everything else was eyeballed.
This has pretty traditional length ratios (the 50% rule for proas, etc.) so you are well within established designs. A polish man on our Yahoo proafile group sails something like this quite successfully with crabclaw sail. You might consider having a foot well. I find a foot well enhances safety, or at least the feeling of safety, when you can get your legs down in the hull. Also more comfortable if you are out longer than 2 hours (but then, younger bodies do better in all sorts of shapes ;-) and perhaps for kite sailing this would not do?)
flywoodkb (author)  Wade Tarzia9 years ago
I was kind of hoping to avoid a footwell for the sake of simplicity, but then I remembered I'd have to get "inside" the hull somehow, at least near the middle, to bolt the thing together. .... or... revisiting the hidden hinge idea, maybe lashing-together points on the deck would work? Makes me think... presuming that the kite is harnessed to me rather than to the boat, I'll need to have my feet over the leeward side to keep my weight over the vaka. There shouldn't be much heeling force, since the lateral force is all being applied just a foot or so over the deck. I think I'll have to hang my akas a bit more over the leeward side and put some kind of footbar across the ends.
You can have a "safety ama" on the lee side. These are used in official Hawaiian OC canoe races. They are technical "single outriggers" but they had so many accidents I guess that they mandated the safety ama. This ama tends to be a little smaller than the main ama and is not meant to be immersed unless the canoe has, essentially, capsized. The safety ama hopefully prevents full campsize, but is never dragging in the water under normal sailing conditions. Seems like a good idea. If you want to avoid foot wells, but still need access, you could just make hatch-covers for your access holes. Or buy those Beckson screw-in covers (pretty cheap); they range from 4 to 8 (or even 12??) inch hole diameters. I use them. 4-inch kind will let you get your hand in well enough. Is being latched to your kite the usual way? Makes me cringe ;-) I picture a capsize and the kite dragging you away from your boat. Or you getting wrapped in the line and the boat, like a drowned rat in a ball of string ;-0
flywoodkb (author)  Wade Tarzia9 years ago
Heh, yes kite attached to body is normal, at least for buggies and boards. There's a loop on the kite control bar that sits in a hook at the fliers waist. It freaked me out for a while when I first started using a harness back in the days before safety releases. Now there's a sort of a ripcord that releases the kite from the hook and lets it "flag out" on one line. It flutters down to the water at that point. There's also another thingy you can pull to release that last line, and a hook knife in a pocket on the harness. It's actually possible to sail upwind (just barely) using just your body and a kite. When kiteboarders are separated from their boards, they can still retrieve them. I think in the video radiorental referenced above they have the kite attached to the boat. If the boat ever "got loose" it would be hard to swim fast enough to get back to it. :) Hatch covers sound great, I'll look 'em up tonight.
flywoodkb (author)  flywoodkb9 years ago
4" screw-in deck hatch covers (or whatever they're called) are under $9 each at Hamilton Marine.
ewilhelm9 years ago
flywoodkb (author)  ewilhelm9 years ago
Oh yeah, I saw that... looks like a whole lot of fun. Wish there was a video to go with that. Will it sail again?