super cheap, simple, dirty: kayak > trimaran

Discussion in 'Multihulls' started by tpchuckles, Jul 27, 2022.

  1. tpchuckles
    Joined: Sep 2021
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    tpchuckles New Member

    Some background: I'm a grad student (low budget), I've been sailing for 17(?) years on a sunfish I got for free, moved to the east "coast" (3 hours from the shore, but some wide rivers a bit closer), and bought a hobie 16.

    I dislike how much setup is required (get on the road at 8, get to the beach at 10:30, then spend an hour setting up, in the hot virginia sun and humidity). I dislike towing a trailer. I dislike needing to take a buddy along because I can't get the mast up on my own. I dislike the launch requirements (without (expensive) beach wheels, I'm stuck looking for public boat launches that aren't too far up a creek, or launches on the precise face of the shore for wind directions on a given day).

    So I got to thinking, maybe this isn't the boat for me, so what is? I want to go fast AF, which is why I bought the hobie 16. I loved the ease of setup of the sunfish (easy enough for one person to drop in the relatively-short lateen-style mast and raise the sail), but then you need another crazy ******* to join you if you want to go out in a storm to find some speed. I hated riding my old boss's laser because of how unstable it was (at least in comparison to my sunfish).

    The proposition:
    A cheap craigslist kayak, plus some DIY outriggers, and whatever mast/boom/sail/spars/whatever assembly I can buy for cheap. disassemble-able. car-top-able.

    My questions:
    ~ Fastest is going to be "just the kayak in the water", so ideally, if you're good with balance (weight distribution, steering, trim), you could sail on the kayak hull alone, and the outriggers are just to "catch" you if you mess up. so I should have the outriggers angled upwards by some amount (how much?). [diagram]
    ~ Since the center of effort is mid-sail, it's attempting to pitch you forwards (a bit), so you need to pay attention to the weight/buoyancy distribution fore/aft. (does the location of the outriggers matter?) [diagram]
    ~ For the beam, I basically just ought to figure out my sail's center of effort (vertically) and for a moment balance, right? (Fx*H=Fg*(W/2))
    ~ For strength of the outrigger supports, I can ballpark consider the "starting to capsize" case, of a fully-upright boat, lateral force on the mast such that 100% of the vertical force is on one pontoon (plus some safety multiplier)? [diagram]
    ~ to construct the hulls, I was thinking just plywood, stitch and glue, with epoxy. must it have glass? and any recommendations on length?
    ~ I assume rigidity of the frame matters, so I was thinking "telescoping" tubes (large diameter metal tube fixed "permanently" across the kayak hull, smaller diameter tubes fixed "permanently" to each hull, small slides into large, with holes drilled or something and a pin dropped in to secure it) would give the "bang for the buck", rigidity vs ease of assembly? I'm curious others' feedback in this area too. ~ I'd also be happy to hear other suggestions on assemblability (ideally I could lift every component off the top of my car, by myself, carry it to the shore, assemble it there, with no bolts or other fancy fasteners (liable to get dropped in the sand or water, or tools liable to get lost)).
    ~ Any advice on materials would be appreciated. I have a mechE background, not necessarily chemistry. I suppose aluminum would be ideal, but would galvanized steel be okay in the salt? (it's heavier, but galvanized steel tubes, of the size and wall thickness i need, are a heck of a lot cheaper than aluminum).

    Cheers, y'all! - tp
     
  2. Scuff
    Joined: Nov 2016
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    Scuff Senior Member

    Are you opposed to using beach cat hulls as the aka's and building a main hull instead? Richard Woods has a couple designs using that approach. Lot's of beach cats laying around. The H16 hulls may not be useable.
    You could build all of it .. my second build was a seaclipper 16 designed by John Marples. It uses the H14 mast, boom, sails. Very satisfied with the performance. John's plans are very detailed and he provides excellent support.
    Checkout Small Trimaran Design | Home Page https://smalltridesign.com/index.html lots of info there
     
  3. tpchuckles
    Joined: Sep 2021
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    tpchuckles New Member

    not opposed. but what's key is that the hulls are easily liftable on top of my car on my own (Jeep wrangler, already on the tall side). I'vd taken off the H16 hulls to do bottom work and they're still not the lightest / maneuverable.

    well, lots of questionable structural integrity? or is that stuff not a concern here anyway, because the frame is likely going to be the "weakest link"?

    thanks for the recs, i'll take a look at those too.
     
  4. Scuff
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    Scuff Senior Member

    I'd look to use a trailer rather than car top that would make the setup alot faster. I bought a H14 turbo with trailer/mast/sails. Modified the trailer to accept the main hull and swing out aka's. The big ***** is getting the mast up the rest is all of 15 minutes.
    How fast do you want to go?
     
  5. tpchuckles
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    tpchuckles New Member

    that's one of my main issues with the 16. I'm not particularly big, so the "just seat the base of the mast, then lift" strategy doesn't work, and it's sketchy as hell. I rigged up a gin pole out of a 2x4, ropes supporting it laterally going to the front corners of the trapoline, carabiner attaches the forestay, and then rope down to the winch on the trailer. still sketchy, but a loooot less so. but it also means you must raise the mast with the boat on the trailer.


    is that stuff on this forum? I'm interested in how you made them swing out, while maintaining strength and rigidity.

    as hell! ;)
    jokes aside, "as fast as i can, given the constraints"
    (raising the mast (me, on my own, lifting the mast/sail, unsketchily). able to transport easily (i'm not totally against trailers, but it's one more thing to deal with parking/storage for. it's more annoying how wide the H16 is). ease of launching (able to beach launch without wheels, on my own)).
     
  6. oldmulti
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    oldmulti Senior Member

  7. Robert Biegler
    Joined: Jun 2017
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    Robert Biegler Junior Member

    That will be faster than a kayak with added sail alone, but still slower than a Hobie 16, and possibly slower than a Sunfish. A kayak's hull shape is optimised for lower speeds. Also, you will need to be careful about how you contain the loads imposed by the rig, board and rudder, seeing that the hull is not designed to accept those. Perhaps the safety margins will be enough, at least in the short term. This could give you the portability, but probably not the speed. To get the speed, you would need a better hull and foils, something like the Hydrovisions Raptor 16 (). I used to have one of those. I never sailed it alongside a beach cat. With the small sail, I expect it would be slower than a Hobie 16, but I am also confident it would be faster than the conversion you propose.

    You might take inspiration from a small, light beach cat of old design, with added foil: Multihull Structure Thoughts https://www.boatdesign.net/threads/multihull-structure-thoughts.62361/page-182#post-931984 That turns it into a lower cost version of Fulcrum Speedworks' UFO: https://fulcrumspeedworks.com/UFO/ If you can find a boat that makes a suitable platform, and you have a skills to build a foil and T-foil rudder, that should be the fastest you can go on a boat, at a modest budget, and without needing a workshop area large enough to build whole hulls. If you insist on a boat, that is. Windsurfing, wingsurfing (), or kitesurfing would give you even better portability, and if you don't insist on racing competitively, you can buy second hand. In fact, that is likely to give you the most speed and portability for money.

    If you are committed to a kayak or canoe, I am currently building a rig and foil arrangement that should contain all the loads from sail and foils in a frame, and the hull only has to deal with buoyancy and drag: https://www.ayrs.org/phpbb/viewtopic.php?f=19&p=4371#p4371 Given that the hull I have available is a canoe, and the sail a 5 square metre lug sail, speed will be modest, but it should meet your portability requirements. The concept could be faster with a better hull and sail, but costs would rise. Also check out the Open Canoe Sailing Group for more orthodox designs: Open Canoe Sailing Group | Sailing Adventures http://www.ocsg.org.uk/

    Bernard Smith's Monomaran III (http://www.oocities.org/aerohydro/designframeset.htm) also contained all the sailing loads in a frame, with the canoe hull only providing buoyancy, and it achieved far higher speeds than I expect from my hinged Bruce foiler. Monomaran III was limited by the unsuitable hull shape of the canoe, which just sucked itself down into the water at 20 knots. Neither Bernard Smith's book "Sailloons and Fliptackers", nor the summary on the web page to which I linked mention how controllable the boat is when you slow down in tight quarters, or when you set it up or take it down on a windy beach, or whether you can sail off a beach. I can think of a few situations in which a sail that can't be sheeted out but only controlled by steering the foils might develop a lot more power than is safe. Ned Snead's Delta, which you can see if you scroll down a bit at https://www.oocities.org/aerohydro/othercrafttext1.htm, is clearly inspired by Monomaran III. From the fact that the windward hull is lifting out, you can infer that the rig is not quite inclined enough or far enough to lee to cancel all heeling, and I read that shortly after this picture was taken, Delta capsized in spectacular fashion and broke up.

    I think this here is slower, but less likely to have fatal quirks: Revolving Catamaran https://www.revolvingcatamaran.com/

    On the whole, if you can get a windsurfer or kite and board for as much as you can get for the Hobie and trailer, that should give you the greatest speed and portability for the least bother, and probably less money than a low-tech derivative of the UFO.

    If you want to experiment, I have a few more suggestions.

    Ingo Voegler's kite boat concept is very ingenious: https://www.youtube.com/user/ingovoegler You would still need the kite, the foil attachment and boat might not be any cheaper than a board, and it is likely slower. But if you need your water and wind sport to be less athletic than kitesurfing, this looks good.

    Bruce Martin's WindFly Rig is equally ingenious, yet totally different: https://www.windflyrig.com/

    Some of Didier Costes' Exoplane series of designs are rather minimalist. He described them in AYRS Catalyst #5: https://www.ayrs.org/catalyst/Catalyst_N05_Jul_2001.pdf Perhaps you can find inspiration there.

    There is what Hagedoorn called ultimate sailing, which is suspending the sailor between a wing in the air and a foil in the water, put into practice over 50 years after the original concept: https://www.youtube.com/watch?v=sXpPyWx7JoQ) I have an alternative design for the foil that should be easier to build than Stephane Rousson's OwlOne Seaglider (http://www.seaglider.fr/Seaglider/Owlone_Products.html). I even have an extremely crude prototype (very nearly Fred Flintstone crude), but I am not a kitesurfer, and I currently lack a boat suitable for testing, so the foil just hangs in my living room until I either find a way to test it, or give up and cut it up. Such a foil could also be used to both steer and keep upright a canoe, if you shunt it like a proa. If you want to go that way, I can explain the design, and you can try that.
     
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  8. Will Gilmore
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    Will Gilmore Senior Member

  9. tpchuckles
    Joined: Sep 2021
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    tpchuckles New Member

    holy cow! every part of this is brilliant! they demo it as being deployable on water, but looks like that folding mechanism would probably be moderately beach-assemblable too (drop in the "axle" pins once you carry each hull from car to beach?).


    wow, a wealth of knowledge here. i'll have to check out each of these. thank you.

    how do you suppose the style of kayak would affect it's speed? the specific kayak i was looking at was a (older, longer) white water kayak, which won't track as easily (who cares, you need a daggerboard anyway), but seems like it ought to plane quite easily?

    your comments on "frame needs to support all loads" is also interesting, and i think opens the door to the possibility of mounting the mast mid-aka? then you can go away with one ama, and you have a sort of weird ******* child cat with a different hull on either side, but hey, the "single outrigger" boats sort of almost have that anyway?


    cool idea, except the price point. that's pretty far from "super cheap". ;-)

    maybe someday when i'm a millionaire. :p
     
  10. Robert Biegler
    Joined: Jun 2017
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    Robert Biegler Junior Member

    I would need to see a picture, especially of the stern. However, most white water kayaks are not designed to plane. I think people sometimes use surf kayaks for white water, though, if there are standing waves large enough to surf. Something like this:
    [​IMG]
    It wouldn't carry much weight, and might be suitable for a small monomaran, not a trimaran.

    Sure. The Raptor 16's predecessor, the Slatts 22, had that feature.

    Another design that might hit your price point is a double Bruce foiler. If you don't go for the high aspect ratio foils of Hydroptere that you would need if you want to fly, but stick to modest aspect ratio just to stay upright, you could build the foils with two skins of thin plywood, or glass over wire-cut foam. You would end up with something like the Foiler 21 (designed by Gerald Holtom, if I remember correctly):
    [​IMG]
    Being North American, you might find a square stern canoe like this, which has a hull shape not a million miles from Foiler 21:
    [​IMG]
    They are meant to take an outboard, and you would want a canoe with a stern wide enough to plane. You would still need to reinforce it to take the loads from the rig, especially if you don't contain, within the rig, the loads from just maintaining sail shape. Do you have any way of measuring the load on your Hobie's forward beam? If so, compare the load with the boat just sitting there with the load once you tighten the jib halyard and sheet in the main. I suspect that is similar to the load from flying the hull without sail loads, which you could measure by having a few friends pulling a rope attached to one trapeze wire, while you stand in the trapeze on the opposite side. So if you can control sail shape with a wishbone boom, or by using the downhaul of a standing lug, that is a lot of load that doesn't need to go into the hull, and which might break a canoe. The transverse loads would go into the beams. You would still need structure that deals with wind forces pitching the rig forward.

    It occurred to me that I forgot to describe what may be the ultimate in reducing the cost of structural loads. The cost of carrying a structural load depends on the load path. The engineers here will correct me if I am wrong, but I think carrying loads in torsion and bending is the most expensive in some combination of weight and money, both of which you need to keep low. Compression is a bit cheaper, but cheapest of all is tension. So if you can mediate between heeling and righting moments with some string, that is both light and cheap. Behold the Swedish Speed Sailing Challenge's paravane boat:

    Both leeway resistance and righting moment is provided by a paravane or hapa. I think the design is Paul Ashford's anchor dog, described in AYRS booklet 114, Ultimate Sailing. That also contains a reprint of Hagedoorn's 1971 article introducing the idea of ultimate sailing, flying suspended between a kite and a paravane. Costs you about two beers: Booklets – Amateur Yacht Research Society https://www.ayrs.org/booklets/ (Disclosure: I have been a member of the Amateur Yacht Research Society for many years and recently joined the committee.) If I find out how to upload pictures from my hard drive, I can show you some pictures of Ashford anchor dogs that I used.

    The speedsailing boat only needs to sail one way, which is not practical for someone who can't afford a chase boat. I found that having a paravane each side is a nuisance. But if you have a paravane that can shunt, like a proa, then you need only one on the windward side, if your boat can also be a proa. A lug schooner canoe stabilised and steered (from on the wind to a reach; below that you need a rudder) by a shunting paravane would let you connect underwater foil and rig with just string. That should be the ultimate in structural efficiency.

    With a canoe hull, I expect it would be good for 8 - 12 knots, so not the speed you are hoping for, but second hand canoes can be cheap, two aluminium tubes should be good enough for the masts, and the paravane does not have to be high-tech, either. Duckworks has lug sails at prices I now find reasonable, though I would have thought otherwise when I was a grad student. I think there are guides to making lug sails from polytarp. Junk rigs have low enough loads that they can be made from cheap materials, and simple enough shapes that they can be made even by me. And a split junk should still have decent performance.

    As for the paravane, I built a shunting version of Ashford's anchor dog in 1999. Rousson's OwlOne paravane is a shunting version of a design by Didier Costes. If you are interested, I can explain how their design principles differ. Alexander Sahlin has a shunting paravane, but the video doesn't show its shape, so I can't comment on the design:

    If you are interested in the idea, I can try to upload some pictures and put together an explanation, or perhaps make a pdf.

    I might end up trying this myself. I have no car, and the hinged Bruce foil frame and rig probably will end up adding 50 kg to the weight of the canoe that will serve as a hull. That is a bit heavy to tow to the water by bicycle for a few hours of sailing, and especially up the hill again after. Adding maybe 15 kg of rig and paravane is another matter. So if I don't get permission to keep a boat in the harbour, there might be a paravane canoe in my life in a year or two.
     
    Last edited: Jul 29, 2022
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  11. rnlock
    Joined: Aug 2016
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    rnlock Senior Member

    I have no idea if this is any good:
    Drop-in Outriggers for Canoes & Kayaks Plans PDF https://duckworks.com/drop-in-outriggers-for-canoes-kayaks-plans/
    or this:
    Kayak & Canoe Sailing Rig: Ultra-Light, Easy to Assemble and Launch! https://www.clcboats.com/shop/boats/boat-plans/kayak-plans/clc-sailrig-kayak-canoe-sailing-rig.html

    I suspect these will be relatively slow, but if you want to go fast, your kayak should probably be relatively strong.

    For something really off the wall:
    https://www.storerboatplans.com/foils/sailing-hydrofoils/foiling-sailboats-homebuilt-no-hiking-out/
    If you put it on a classic moth, as above, the whole thing would probably be pretty light. Assuming you're light enough for a Moth. Classic Moth plans here: Earwigoagin: Classic Moth plans http://earwigoagin.blogspot.com/2010/03/classic-moth-plans.html
     
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