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Thread: Inflatable Proa

  1. #36
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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    Don’t want to break copyright law too much but look what I found in AYRS Design for fast sailing

    Texts talk about foils canted and not canted but do not give any accurate details or if anyone has ever build one
    Sorry Tink - I skimmed over this one and I now realise it's the most stimulating of the lot. Firstly those akas as shown don't reach across the boat so the ama might stay in the water as the boat heels away from it - reminiscent of the adze-board with the wind over the ama towards the vaka - but they do extend far enough to heel onto the ama if the wind is the other way. Interesting - maybe it could become a safety feature...

    I'm not sure this was entirely intentional - the vaka end is called a pivot not the pivot+hinge/universal joint (or simple strap) needed for a panto adze.

    Even with a more normal constrained aka, the author is still right in implying it could actually work as either Pacific or Atlantic mode, and with delightful insouciance omits to say that the the foil angles would have to reversed to tack from one to the other (I think).

    Now there's a challenge - a genuine tacking proa that's just as stable on both - but it has to be somebody else's problem (SEP) because I will try to avoid it - that way madness lies. I think this mirror-image foil method has been tried on trimarans - it may be what the Bruce foil Wiki was alluding to.

    I forgot to refer earlier to accounts of an annoying problem with Bruce foils - it's described as their tendency to jump right out of the water in a surprise wave (ferry wake) or a really sudden gust - triggering a capsize (the original version where the foil is mounted beneath the windward hull of a cat looks safer now).

    A hinged board (vector or adze) never comes out of the water because it swings down on its hinge during a heel - no matter how sudden (until the windward hull rises higher than the board's arm length to windward, and by then it's probably all over anyway one way or the other - the wave or gust has gone or hopefully there's been time to loose the sail before the gust becomes a squall).
    Last edited by Saedilla; 04-01-2018 at 04:02 AM.

  2. #37
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    Default Re: Inflatable Proa

    Quote Originally Posted by Saedilla View Post

    A hinged board (vector or adze) never comes out of the water because it swings down on its hinge during a heel - no matter how sudden (until the windward hull rises higher than the board's arm length to windward, and by then it's probably all over anyway one way or the other - the wave or gust has gone or hopefully there's been time to loose the sail before the gust becomes a squall).
    Have to say this now has be perplexed, if the hinged board (vector or adze) ant therefore aka bad ama are not effected by heel I am not sure why you need or want to shunt like a proa. The only reason I can think you would go down the proa route is to use the ama / aka - outrigger for additional stability

  3. #38
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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    Have to say this now has be perplexed, if the hinged board (vector or adze) .... not effected by heel I am not sure why you need or want to shunt like a proa. The only reason I can think you would go down the proa route is to use the ama / aka - outrigger for additional stability
    You're right that I'm not using the weight of the ama to resist heel. Though wierdly (for a Pacific Proa) I am using its buoyancy - it works as insurance against the adze board being pulled under while opposing the heel - it's a small risk since the adze stays vertical with no downforce until the boat heels, I suspect that when heel happens the adze is self-regulating because it's also pulling to windward all the time - and that should stop it going right under - but there's no point in skimping on the buoyancy. I know the damn thing works well at 2, 3 or 4 knots, but I don't want any surprises as I improve its performance.

    My diagram in post #13 shows an Adze board is affected by heel, but the adze only resists heel (like a Bruce foil) when the hull lifts (I'm not sure if this applies to the Vector too), then the sideforce resisting leeway becomes downforce resisting heel. The kayak is so easily heeled that having normal cantilever akas would have the board on the ama popping out of the water every 5 minutes, and without that board in the water I can't sail at all - there is no other lateral resistance to movement, and as I said in post #34, an inflatable kayak (or at least a cheap one) actually "prefers" to go sideways anyway.

    The shunting proa fits my bill because I only need one nest of gear fitted to one side, and an inflatable with a board one one side is like a balloon on a stick - it's a big fight to get the wood to stay to lee - I've tried to turn that to my advantage by "going Pacific".

    I've had a stab at a forces diagram.

    I wasn't kidding about showing the kayak as a potato-cloud - it works for me by stopping my knee-jerk assumption that a kayak shape has a preferred direction.

    Drawing this has given me a headache so I will state the caveats here (and include them later):
    I am assuming a nearly-wingsail (envelope), with the CofE bang on the mast in light airs. I'm assuming doing without feathering by using solid 'sheets' - OR adding a tailplane to make a glider rig with no sheets at all.
    I have tried to show the CofE moving with the bellying of the sail, I don't know whether to add a little movement forward on a reach (it depends on how wing-like the sail behaves).

    I'm only 60% happy with it so please feel free to criticise even the smallest errors.
    proa sailing 1 cloud-potato.jpg

    BTW. I looked online for an image to use, but some of the potatoes were watermarked (madness) - this is actually a cloud cut out of my photo of a yacon - we ate all the potatoes yesterday...
    Last edited by Saedilla; 04-01-2018 at 08:30 AM.

  4. #39
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    Had an idea, if you put a ‘stiff’ hinge in the middle of the AMA and have adjustable angles to the splat (you could just tape shims to the upright) you can have different angles of incident or each foil and therefore will be able to control the CLR position.

    The hardest part getting the CE CLR balance is downwind.

    I would still argue, from a position of experience, that a proa is not the minimal may and certainly not the easiest way to get your canoe to sail.

    This is how someone has rigged an inflatable to sail,


    And this is how I did it, there are inflatable floats on the end of the AKAs






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  5. #40
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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    Had an idea, if you put a ‘stiff’ hinge in the middle of the AMA and have adjustable angles to the splat (you could just tape shims to the upright) you can have different angles of incident or each foil and therefore will be able to control the CLR position.

    The hardest part getting the CE CLR balance is downwind.

    I would still argue, from a position of experience, that a proa is not the minimal may and certainly not the easiest way to get your canoe to sail.
    The panto akas give a lot of CLR control - I think my last diagram hints that it can give enough to cover the shifting CofE from different points of sail (for some reason it is an attachment to post #38 rather than appearing in the post) - I could double it's movement with longer akas raked further back if necessary and still maintain the 2' gap needed for paddling.

    The hinged ama would work, but I would need strong stops to prevent jack-knifing and damaging the spats. If I need extra control I will try it but it introduces too many variables to go straight for it.

    I'm not bothered about running downwind - on a windsurfer I always took it as an opportunity for a rest, with the sail covering the length of the board and me lying on it - as long as feathering is an option it's good enough for me. With all the changes this year I won't be racing anybody - if ever - my lack of interest in racing is the main reason I can't use the clubs on the local lakes - they are all obsessed with it - I'd never succeed in becoming a member in good standing with that bunch, and they'd never let my piece of junk on their domain otherwise...

    I have to make the proa a minimalist solution - with an economy flight in the critical path I have no choice. I can add complexity (like the A-frames and gunwales) only if they can be built from really basic local materials - basically an unwanted pallet - and they can be.

    I'm going to have to photoshop an image of my last try to convince you - it did work work, and it would have worked twice as well with a mast - if I'd had just two more days.

    Temporarily AFK - I'll continue ASAP.

  6. #41
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    Default Re: Inflatable Proa

    Quote Originally Posted by Saedilla View Post
    The panto akas give a lot of CLR control - I think my last diagram hints that it can give enough to cover the shifting CofE from different points of sail (for some reason it is an attachment to post #38 rather than appearing in the post) - I could double it's movement with longer akas raked further back if necessary and still maintain the 2' gap needed for paddling.

    The hinged ama would work, but I would need strong stops to prevent jack-knifing and damaging the spats. If I need extra control I will try it but it introduces too many variables to go straight for it.

    I'm not bothered about running downwind - on a windsurfer I always took it as an opportunity for a rest, with the sail covering the length of the board and me lying on it - as long as feathering is an option it's good enough for me. With all the changes this year I won't be racing anybody - if ever - my lack of interest in racing is the main reason I can't use the clubs on the local lakes - they are all obsessed with it - I'd never succeed in becoming a member in good standing with that bunch, and they'd never let my piece of junk on their domain otherwise...

    I have to make the proa a minimalist solution - with an economy flight in the critical path I have no choice. I can add complexity (like the A-frames and gunwales) only if they can be built from really basic local materials - basically an unwanted pallet - and they can be.

    I'm going to have to photoshop an image of my last try to convince you - it did work work, and it would have worked twice as well with a mast - if I'd had just two more days.

    Temporarily AFK - I'll continue ASAP.
    You don’t need to convince me anything, I 120% get the compulsion to developer a proa, I was obsessed with proas for almost 30 years.

    I still like to race and was lucky that my club let me sail the proas on the lake but only when it was only being used for casual sailing which accounted to about 15 days a year

    The thing I love about my sailing canoe is that I just drop in the local river and sail freely so I get where you are coming from

  7. #42
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    Default Re: Inflatable Proa

    I wasn't obsessed with proas until I experienced the following:

    When I built a tacking rig in what I call the 'battleship' approach I had a mast on the centreline and conventionally placed about 1/3 of the way from the bow - the boat was trimmed conventionally by swinging the boards down on the lee side - mark II had almost 4 sqft of 5mm ply in the water as leeboard and fin, and I could swing them back, forwards, everywhere and it was still skittish wherever I put them, I also had a decent sized rudder. As soon as I changed course the whole kayak would do it's damnedest to get to lee of the leeboards - it could do it in two seconds flat. You wouldn't get this problem with a normal canoe (you might with a slalom kayak).

    I put the boards down both sides and it only steadied a bit - despite 8 sqft of ply in the water. I left the windward boards down and lifted the leeboards and the handling improved on every point of sail with only 4 sqft in water, but the heel lifted the windward boards enough to make the crabbing (very stable crabbing) quite noticeable - I think the boards were bending too - so they were 'climbing' out of the water.

    The 3rd year I Just had the adze board as shown in the diagram in post #13 - just 2 sqft - nothing else in the water apart from my big smooth soggy balloon of a kayak - but because the adze was stiffer (set lengthways) and always fully immersed (thanks to the hinge) it did better - much better - than the 8 sqft version above. Much more stable on any point of sail, and much less crabbing.

    I'm pretty sure that with 4 sqft in the water it would only be limited by the size of the sail (which I also plan to double after the first test by doubling the number of masts because the gap between would be "paddle friendly").

    By doubling both I should add speed - making the 4 sqft behave more like 6 or 8. Problem solved - I hope...

    Posting on this forum has made a big difference - all the discussions confirmed my gut feel and threw in lots of new ideas - it also made me focus better on the problems so - eg. I could see the panto ama would be promising and it turns out to be widely tried and tested.

    I always thought the adze board was OK - simply taking half of Bernard Smith's idea of a windward foil and using it with a twist.

    I would say Edmond Bruce also took half of Bernard Smith's idea and with it he made something that's arguably more useful. My half is just a slightly different half - but it is what I need for my specific crazy proa problem.

    So I've decided to go for a panto 2-adze-board on one ama, with a non-moving mast - I don't expect any major problems with that - I can make the fancy bits like the spats before I go - if I'm strapped for baggage weight I can just take the triangular sides and make the spat boxes when I get there. The A-frames, gunwales and akas could be planks from an abandoned pallet - 4' is the limit on those but that's plenty as the boat is only 10' long.

    Using the battleship approach with leeboard and fin both sides is like trying to break into a castle through the front door - but using the hinged adze board is like having the key to the postern gate.

    The 'soft envelope' sails will be an experiment I'm looking forward to.

    At the moment I'm thinking about how to make self-setting 'glider rig' sails from what's thrown away... I haven't told my wife I might need to fit 2 pieces of 3' x 18" x 1/2" twinwall polycarbonate into my luggage just in case...

    I've seen a sail that is a bit like a gibbons but it's a paper dart/hang glider shape that flips horizontally over the mast to shunt (or tack) - nice and easy to convert to self-set - the closest I could find is this, but it's pretty clear it's begging to be a glider.
    Sail - horizontal flip.JPG
    - but it leaves the mast exposed to drag, whereas the soft envelope doesn't - decisions, decisions...
    Last edited by Saedilla; 04-01-2018 at 05:52 PM.

  8. #43
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    A very interesting account of what happened with your tacker and I can see why your immersed foil is appealing.

    The leeboard on my sailing canoe works fine, I would say it has a total area of about 6sq ft and probably about 4 in the water. It is an old international canoe centre board so is foil shaped. A 5mm flat plate isn’t really going to provide good lift and likely to still out.

    As there are numerous people would have sailed canoes with simple leeboard set ups I would imagine the 5mm flat plate was the cause of you problem



    That said this setup clearly works with a very simple and small board

    https://youtu.be/yuQ2rkrI_Po
    https://www.sailboatstogo.com/catalog/CANOE_RIG

    Lots so variants and ideas on their website

    Your low aspect ratio adze board obviously grip the water better like Hobie cat hulls etc


    I am in no way suggest this as a direction, though it might interest you. The canoetri only uses the ama for lateral resistance and ignoring it is a tri hydrodynamically if is probable similar your setup

    https://youtu.be/7B4nprGPFm0
    http://www.canoetri.com/canoetri.html#p1




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  9. #44
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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    The canoetri only uses the ama for lateral resistance and ignoring it is a tri hydrodynamically if is probable similar your setup
    The lift-stall diagram is great - very significant - interpreting it another way, it means that a flat plate has to be much bigger to get the same lift at smaller angles of attack so it can stay away from the stall area - that's why my first instinct on the 'mark I' leeboard & fin was to double their size. Fortunately flat plates are also twice as easy to take on an aircraft.

    It would be nice to have the performance of a proper aerofoil, but proper aerofoils are not reversible, and on a proa they would have to be flipped somehow - there's no way I'm going to attempt that - the obvious way would be to have effectively a "hydrodynamic model glider*" mounted on the hinged outrigger with a smooth bearing so it could yaw 180 deg between shunts (* this would look very similar to the lifting foils mounted beneath those incredible foiling surfboards).

    It would look amazing - like 50s bonnet-ornament - If I made one I would hang it in the bedroom between outings.

    Nevertheless your suggestion could be a game changer by considering curved plate aerofoils - the big advantage is the increase in stiffness (so I could increase aspect ratio - though it would be a lot less convenient), and the increase in lift is significant (see URL below) - certainly enough to offset the very low aspect ratio of my most convenient board shape for an adze-ama - that's 2'x1' set 'landscape'.

    The data is here:
    https://ac.els-cdn.com/S187770581734...f5af4ee2d04a3b

    They shows lift coefficients @ 6 deg of 1.4 for 10% curve and 1.9 @ 6 deg for 15% - unfortunately stall isn't shown but the 10% is almost straight; the fall-off of the 15% is just creeping in at 6 deg, no sign of the fall-off at 4-5 deg shown by the flat plate.

    Looks like a goer! I will look at filling the inside of the curve, because I remember that only the earliest aircraft had few problems from underside camber eg. WW1 aircraft at speeds around 90mph. For the sake of visitors from the internet I'll elaborate - unfortunately stuff under water is very different - the density change is 1000x (most of the forces follow that), the sound barrier at sea is 4.4x faster at 2912 knots - so I imagine the underside camber problems will start between 20kt and 0.01kt - after balancing the effects I would guess around 1 knot?

    It's still very scary. I'll try and take some thin tough vinyl sheet with me, and glue it over the whole curved board - the reduction in skin drag alone would be worth it. It's a pity there's no such thing as a PET bottle 12" tall and ~15" in diameter - if it was spot-on I could use it to hold the curve (I know you're thinking 8 litre water bottles - but the ridges spoil them).

    I can't find any performance data for a circle segment aerofoil - I can't believe it won't be somewhere between a flat and curved plate, with probably less drag, so I'll try it anyway.

    Thanks.

  10. #45
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    An Ogival section is reversible (no flipping required) and ideal for a proa. I built mine with RWC core and carbon but easy to do from two thin sheets and a central web. Loads of info here

    http://www.basiliscus.com/ProaSectio...oaSections.htm






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  11. #46
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    Default Re: Inflatable Proa

    There was a foil considered better than an ogive section for a shunting proa -- at least one proa specialist feels that the leading edge of the ogive can "take over" and not work too great, although I am not sure at what speed that might pertain to; my info source said this about a large pretty-fast proa). I am trying to think of the guy's name -- he was a true technician, I believe a professional aerodynamicist, and used to post at the old yahoo proafile forum. The suction side looked like the ogive but the pressure side had a shallower curve. -- Wade

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    Default Re: Inflatable Proa

    I think you are taking about the series 3 proa foils from Thomas E Speer, referenced above and also here

    http://www.basiliscus.com/ProaSections/ProaIndex.html

  13. #48
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    Default Re: Inflatable Proa

    Quote Originally Posted by wtarzia View Post
    There was a foil considered better than an ogive section for a shunting proa -- at least one proa specialist feels that the leading edge of the ogive can "take over" and not work too great, although I am not sure at what speed that might pertain to; my info source said this about a large pretty-fast proa). I am trying to think of the guy's name -- he was a true technician, I believe a professional aerodynamicist, and used to post at the old yahoo proafile forum. The suction side looked like the ogive but the pressure side had a shallower curve. -- Wade
    That's great Tink - it's nice to see I'm not yet away with the fairies - presumably my googling came up blank because I was calling it circle segment instead of ogive - I wouldn't have guessed that in a million years (as an arch it's halfway between an arc and a V, or rather two arcs as a V).

    I will be going for a very rough compromise when I make one but it sounds like my knee-jerk impulse to make the edges sharp was misguided. Thanks Wtarzia - forewarned is forearmed so it's easy to move away. There's no way I can follow any of the shapes perfectly, but I will certainly put a slight convex camber on the underside if I can.

    I'm relying on my eyes - trained by teenage aero- and catamaran modelling - if it looks good it will probably fly, if it looks bad it probably won't - the hard part is stopping the exceptions creeping past in the dark.

    I have simplified my panto amas by thinking of the delights of metal shim plates from beercans and I've modified my boat plan as below.
    I've also photographed some pens to show the A-frames and gunwales don't create an Escher nightmare - sorry the photo should have been from the other side to match the diagram.
    Proa A-frame gunwales + adze.jpg
    Proa A-frame & gunwales - no Escher.jpg

  14. #49
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    Default Re: Inflatable Proa

    Quote Originally Posted by wtarzia View Post
    There was a foil considered better than an ogive section for a shunting proa -- at least one proa specialist feels that the leading edge of the ogive can "take over" and not work too great, although I am not sure at what speed that might pertain to; my info source said this about a large pretty-fast proa). I am trying to think of the guy's name -- he was a true technician, I believe a professional aerodynamicist, and used to post at the old yahoo proafile forum. The suction side looked like the ogive but the pressure side had a shallower curve. -- Wade
    --- I have been driving myself crazy for the last HOUR trying to remember and find the foil section I was talking about. Success, at last. Tom Speer was the designer, and here is his article: http://www.basiliscus.com/ProaSectio...oaSections.pdf --Wade

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    Default Re: Inflatable Proa

    Saedilla,
    I have only skimmed most of your thread but wanted to comment on proas.
    I've made several skin-on-frame proas between 16' and 22' and experimented with four line kites on them with huge success, especially in rudderless steering using Barber-haulers from the aft quarters.
    I'm now building a stabilized monohull using the same principles.
    The cool thing about a kiting proa is flying the kite off the ama...

  16. #51
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    Default Re: Inflatable Proa

    Quote Originally Posted by Tom Christie View Post
    Saedilla,
    I have only skimmed most of your thread but wanted to comment on proas.
    I've made several skin-on-frame proas between 16' and 22' and experimented with four line kites on them with huge success, especially in rudderless steering using Barber-haulers from the aft quarters.
    I'm now building a stabilized monohull using the same principles.
    The cool thing about a kiting proa is flying the kite off the ama...
    Hi Tom,

    Does flying the kite off the ama mean using both sail and kite? - it's almost Mad Max stuff!

    I sympathise with skimming this thread - it has got convoluted, and I have to take 90% of the blame for that, it's almost my signature and I wish it wasn't.

    Of course I love the sound of my own text - it's like having a child (apparently) you love them even when they're c**p. So it was just too tempting to copy this aside out of a mountain of my earlier ramblings.

    Having said that, the Kite Scooter almost makes me want to abandon my hard-earned proa progress so far and start copying that instead - using 5mm ply and bits of old pallet... Clarkey and Woxbox are right on the money - it would almost certainly be much lighter than a proa.

    What makes it even more interesting (to me) is that I tried kites at one point and found that an ordinary landlubber cheapo £20-40 power kite can be made to survive dunking in the sea AND make line-only takeoffs from its surface, as long as about 1/3 of the cells are filled with very light bladders (those thin rustly plastic bags are good - PolyP?).

    The main thing that put me off was the need to use or make a proper kite harness - I found kites almost impossible to fly even one-handed without one - you'd need to sail with both hands free the whole time (I always needed to paddle into the perfect orientation then snatch up the lines - and fail). However if you've got a spare crew member with nothing better to do while you paddle, then even without a harness they can still power, trim or even steer the boat - and if you're already sailing it they could add a lot of speed (though I never got that far).

    I'd be really interested if someone could make a working kite scooter from junk and say, a manageable 3sqm kite - getting 5 knots would be ample - all my ambitions start with making the same speed as hard paddling, ideally while sitting back and enjoying a nice dark beer. I will only start trying to get the knots into double figures after I've achieved this!

    A friend of mine is trying kitesails on an old Hobie cat in the Netherlands - I'm waiting to see how he gets on - it's not great sailing weather right now.

    Regards.

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    Default Re: Inflatable Proa

    big kites can be super dangerous...

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    Default Re: Inflatable Proa

    Quote Originally Posted by Saedilla View Post
    Hi Tom,

    Does flying the kite off the ama mean using both sail and kite? - it's almost Mad Max stuff!

    I sympathise with skimming this thread - it has got convoluted, and I have to take 90% of the blame for that, it's almost my signature and I wish it wasn't.

    Of course I love the sound of my own text - it's like having a child (apparently) you love them even when they're c**p. So it was just too tempting to copy this aside out of a mountain of my earlier ramblings.
    Having said that, the Kite Scooter almost makes me want to abandon my hard-earned proa progress so far and start copying that instead - using 5mm ply and bits of old pallet... Clarkey and Woxbox are right on the money - it would almost certainly be much lighter than a proa.

    What makes it even more interesting (to me) is that I tried kites at one point and found that an ordinary landlubber cheapo £20-40 power kite can be made to survive dunking in the sea AND make line-only takeoffs from its surface, as long as about 1/3 of the cells are filled with very light bladders (those thin rustly plastic bags are good - PolyP?).

    The main thing that put me off was the need to use or make a proper kite harness - I found kites almost impossible to fly even one-handed without one - you'd need to sail with both hands free the whole time (I always needed to paddle into the perfect orientation then snatch up the lines - and fail). However if you've got a spare crew member with nothing better to do while you paddle, then even without a harness they can still power, trim or even steer the boat - and if you're already sailing it they could add a lot of speed (though I never got that far).

    I'd be really interested if someone could make a working kite scooter from junk and say, a manageable 3sqm kite - getting 5 knots would be ample - all my ambitions start with making the same speed as hard paddling, ideally while sitting back and enjoying a nice dark beer. I will only start trying to get the knots into double figures after I've achieved this!

    A friend of mine is trying kitesails on an old Hobie cat in the Netherlands - I'm waiting to see how he gets on - it's not great sailing weather right now.

    Regards.
    No, just a kite, no traditional sail.
    What I meant by "off the ama" was attaching the kite to the ama.

    I used 2x3's for the gunwales, 2x2's for the chines and 1/4" ply for the two bulkheads.
    Pallet wrap for the "skin" ( at $15CAN per 1500 foot roll ) it would make about three boats each.
    I was able to sea-trial a design, tear it down, rebuild a new design, or feature, and wrap it again.
    One needs to have plenty of experience with kites before attempting this however, otherwise, you may end up making comments like "kites can be super dangerous".
    Crossing the street can be super dangerous if you don't do it properly.
    Shunting makes for safer turns as the kite never needs to travel over-head.
    Very similar to what you see in that old black and white photo of Peter Lynn earlier in your thread.

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    Default Re: Inflatable Proa

    Quote Originally Posted by Tom Christie View Post
    No, just a kite, no traditional sail.
    What I meant by "off the ama" was attaching the kite to the ama.

    I used 2x3's for the gunwales, 2x2's for the chines and 1/4" ply for the two bulkheads.
    Pallet wrap for the "skin" ( at $15CAN per 1500 foot roll ) it would make about three boats each.
    I was able to sea-trial a design, tear it down, rebuild a new design, or feature, and wrap it again.
    One needs to have plenty of experience with kites before attempting this however, otherwise, you may end up making comments like "kites can be super dangerous".
    Crossing the street can be super dangerous if you don't do it properly.
    Shunting makes for safer turns as the kite never needs to travel over-head.
    Very similar to what you see in that old black and white photo of Peter Lynn earlier in your thread.
    Great ! I see now that we are talking minimalism!

    It's a brilliant way to make a hull - I did something similar many years ago when I made a cat from canes and agricultural polythene (it's much better stabilised against UV than builders' stuff). I started out by strengthening the hulls with a papier mache skin, but I stupidly tried to make my gloss-paint sealant go too far and water got in the last section I painted - so all the soggy paper had to come off and the polythene had to go on. The cane structure/armature was very light and absurdly flimsy - it was only held together with twists of fence wire & would have collapsed if a child sat on it - but once it was wrapped and in the water it was remarkably durable and surprisingly low drag (it was a bit lumpy but the lumps were smooth curves in the cane stringers).

    That raises a point - on a tacking or paddling hull it's easy to get a low-drag skin from PE sheet by making all the darts/pleats with all the folds pointing aft.

    My cane cat was basically 2 very long narrow coracles - and exactly the same way I used to make very light, fast model boats when I was a kid - with one key difference - I used doped tissue on the models so it shrank to fit.

    That's why I'm beginning to see the brilliance of using pallet-wrap for a proa - you mean the heat-shrink type? (not the luggage-wrap stuff). Is it thick enough to wrinkle less - with careful use of a hair dryer? Do you use more than one layer? Does that need a releasing agent to stop the last smoothest layer sticking to the previous one?

    It could be a game-changing technique, and if you wanted some UV resistance you could shrink-wrap over a pleated polythene hull (at least that would mean it could fail gracefully).

    I would fudge around my lack of skill by using brown packing tape over the pleats of the inner PE hull and over any wrinkles going the wrong way in the outer one - at least for testing.

    Brown tape's remarkably reliable provided it's covering an impermeable, mostly smooth surface (ordinary clear tape is useless - the mere shadow of a glass of water is enough to make it come off).

    Brown tape shrugs off 2 weeks of daily 2-3 hour dunkings in seawater - I use it to hold the two halves of my holiday boogie board together (no annoying baggage surcharges for something so very slightly oversize). UV resistance of the tape glue is nearly zero, but it still takes a few months to weaken - that just makes it easier to get the tape off before the next trip.

    The special clear waterproof tape for PC roofing has advantages - it's expensive, but worth it for boat building - the cheap stuff is especially annoying because it leaves everything sticky - though that might be tolerable on an inner permanent PE skin with shrink-wrap over it.

    Regards.

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    Default Re: Inflatable Proa

    Quote Originally Posted by Daniel Noyes View Post
    big kites can be super dangerous...
    --- And they can be very problematic in launching and re-launching from a wet-place (inflatable leading edges critical here). How are they for going to windward? Kites do get up into the better air of course, but do they let a good hull make as a good a course as a good sail does? (Not a critique, just curious about ideas; I have heard both sides of that argument, which has left me confused). -- Wade

  21. #56
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    Default Re: Inflatable Proa

    Quote Originally Posted by Saedilla View Post
    Great ! I see now that we are talking minimalism!

    It's a brilliant way to make a hull - I did something similar many years ago when I made a cat from canes and agricultural polythene (it's much better stabilised against UV than builders' stuff). I started out by strengthening the hulls with a papier mache skin, but I stupidly tried to make my gloss-paint sealant go too far and water got in the last section I painted - so all the soggy paper had to come off and the polythene had to go on. The cane structure/armature was very light and absurdly flimsy - it was only held together with twists of fence wire & would have collapsed if a child sat on it - but once it was wrapped and in the water it was remarkably durable and surprisingly low drag (it was a bit lumpy but the lumps were smooth curves in the cane stringers).

    That raises a point - on a tacking or paddling hull it's easy to get a low-drag skin from PE sheet by making all the darts/pleats with all the folds pointing aft.

    My cane cat was basically 2 very long narrow coracles - and exactly the same way I used to make very light, fast model boats when I was a kid - with one key difference - I used doped tissue on the models so it shrank to fit.

    That's why I'm beginning to see the brilliance of using pallet-wrap for a proa - you mean the heat-shrink type? (not the luggage-wrap stuff). Is it thick enough to wrinkle less - with careful use of a hair dryer? Do you use more than one layer? Does that need a releasing agent to stop the last smoothest layer sticking to the previous one?

    It could be a game-changing technique, and if you wanted some UV resistance you could shrink-wrap over a pleated polythene hull (at least that would mean it could fail gracefully).

    I would fudge around my lack of skill by using brown packing tape over the pleats of the inner PE hull and over any wrinkles going the wrong way in the outer one - at least for testing.

    Brown tape's remarkably reliable provided it's covering an impermeable, mostly smooth surface (ordinary clear tape is useless - the mere shadow of a glass of water is enough to make it come off).

    Brown tape shrugs off 2 weeks of daily 2-3 hour dunkings in seawater - I use it to hold the two halves of my holiday boogie board together (no annoying baggage surcharges for something so very slightly oversize). UV resistance of the tape glue is nearly zero, but it still takes a few months to weaken - that just makes it easier to get the tape off before the next trip.

    The special clear waterproof tape for PC roofing has advantages - it's expensive, but worth it for boat building - the cheap stuff is especially annoying because it leaves everything sticky - though that might be tolerable on an inner permanent PE skin with shrink-wrap over it.

    Regards.
    No, not shrink wrap, pallet wrap.
    Like stretch-and-seal from the kitchen but not food grade and a lot less expensive.

    500 feet on a 20 foot boat, yes, there's some overlap.
    On the race boat, we used all 1500 feet, so it was over 20 layers thick.
    We developed quite the technique, wrapping bow to stern with about 2" spacing ( there's 6 layers ),
    then horizontal wraps ( another 2 layers ),
    then wrapping stern to bow with one inch spacing ( 12 more layers ).
    I couldn't push my thumb through it!
    Some leaked up to about a cup over an hour but others leaked less than an ounce over three hours.
    No tape.
    The boat weighed about 45 pounds and supported three paddlers as a sit-on-top.
    We won the race with only two paddling.
    The third was a stand-up roll technician.
    She flew the tiny ama with the aid of a 3' hydrofoil set to ~9 degree angle of attack.

    Following the race I experimented with the kite to develop a stabilized monohull prototype.
    It's made out of polystyrene foam and fiber-epoxy and will have a big kite.

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    Default Re: Inflatable Proa

    This sounds awesome, any pictures? Blog? 250m of wrap cost about a beer and a half in the UK

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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    This sounds awesome, any pictures? Blog? 250m of wrap cost about a beer and a half in the UK
    No blog.
    I had lots of pictures but lost them in a computer crash.
    This video shows the race but turn the volume down as Jason gets rather excited with the screaming while taping.
    You can see the foil around 9:50, pretty flexible mount.
    Gotta love 1/4" ply!

    https://www.youtube.com/watch?v=MJuwvxli5eI

    Not bad for $70US ( including paddles ), three hours build time, no power tools allowed.
    Fun

    This was the proa I did the proof of concept work on with the kite, solo.
    Stabilized monohull building now, no photos.
    Last edited by Tom Christie; 04-03-2018 at 01:11 PM.

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    Default Re: Inflatable Proa

    Quote Originally Posted by Tom Christie View Post
    No blog.
    I had lots of pictures but lost them in a computer crash.
    This video shows the race but turn the volume down as Jason gets rather excited with the screaming while taping.
    You can see the foil around 9:50, pretty flexible mount.
    Gotta love 1/4" ply!

    https://www.youtube.com/watch?v=MJuwvxli5eI

    Not bad for $70US ( including paddles ), three hours build time, no power tools allowed.
    Fun

    This was the proa I did the proof of concept work on with the kite, solo.
    Stabilized monohull building now, no photos.
    That is fantastic, congratulations on winning the race.

    That is is an inspirational way to build a development boat, I will be most certainly giving it a go.
    I want to build new outriggers for my sailing canoe and I will start experimenting with those. But have lots of ideas for craft to build after that.

    I also see no reason why it could not be used over a from core.


    Are there any techniques for the joints of the wrap, your craft looks incredibly smooth

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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    That is fantastic, congratulations on winning the race.

    That is is an inspirational way to build a development boat, I will be most certainly giving it a go.
    I want to build new outriggers for my sailing canoe and I will start experimenting with those. But have lots of ideas for craft to build after that.

    I also see no reason why it could not be used over a from core.


    Are there any techniques for the joints of the wrap, your craft looks incredibly smooth
    Thanks Tink, very kind of you.

    The wrap is done in one piece.
    Only apply moderate pressure ( tension actually ) or the cumulative stress will overly deform, and even damage, the frame.
    Use a block plane to smooth and round the edges first and be sure nothing is poking out of course.
    And there is no abrasion resistance, hence the fluffy purple pillow at the race start on the beach.
    We simply tied the pallet wrap to the frame to start and rolled it up on a foot of 2x2 and screwed it down on top of the bow to finish.
    Three people is the way to go.
    Two to pass the roll over and under and one to lift the frame up at each end when you get to the saw horses.
    By starting at the bow, a necking effect shapes the lines for a cleaner entry and smaller bow wave.
    It also gives the stern a fuller shape if just one bulkhead is used.
    By finishing stern to bow, a fish scale effect stops water scooping.
    Use self tapping wood screws on the frame for easy disassembly.
    Don't use too many, the wrap ends up holding the thing together.

    When transitioning from vertical wraps to horizontal ( and back ), just fold the wrap under like wrapping a birthday present.
    Kind of hard to explain but intuitive once you get going.

    I don't see any point in using it over foam.
    Be sure and use closed cell foam regardless.

    Cheers!

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    Default Re: Inflatable Proa

    Saedilla,

    Sorry to have hijacked your thread.

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    Default Re: Inflatable Proa

    Tom, that's really considerate - but anything you start is what it becomes - it has to live within the consensus - a lively debate is all - what matters is the greatest good (or happiness depending on your favourite philosopher).

    Incidentally my recent silence is more to do with the weather - over here we have had almost unremitting rain for the last two weeks - it's so bad it's actually become unseasonable - even for England!, and this thread has been the only thing keeping me sane - so I've enjoyed every word & pixel you and everyone else has contributed - but yesterday afternoon was my first chance to make a start on all my outdoor jobs, and today was also too precious to miss.

    Of course I'm aware that my assumptions about your techniques and their design brief were premature - it's not my first time for that - but I am still a newcomer to proas - my year of familiarity is really only 3 weeks in the sun last autumn.

    Your technique is inspirational in it's approach to your design brief, and that stopped me thinking that not all proas are bi-directional.

    I risk sounding like sour grapes, but a smooth heat-shrink plastic skin over pleated polythene would have real benefits for a shunting proa if the design brief was for a whole summer's sailing - you could cut the heat-shrink off as the next season starts or just put another layer on.Apparently it's about 10 x 1 metres for £1 - though I'd estimate wasting 30 to 50 metres (the price of a pint in Central London) - before developing the skills required!

    However I know how long it takes to make a cane-stringer hull (the one thing I don't have in Greece is good clean, uniform timber longer than 4 feet), and my inflatable kayak gets me on the water quicker, since I still enjoy paddling, and I now I know how to play to the 'strengths' of the craft, so the additional kit to turn it into a sailing proa is only slightly more than what it would take to convert a normal canoe. Incidentally the hinged adze-board would work on both and simplifies everything.

    But I still have lots of sail design problems - I will be begging everyone's patience for some time yet.

    Thanks and Regards.

  28. #63
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    Default Re: Inflatable Proa

    Dreary weather has returned - so I'm back with issues about self-setting sails - I would call them a glider rig, but neither brings up even a fraction of the designs I know are out there, so presumably I've got the name wrong? (again).

    The Aerorig works - it's basically a very soft canard - or a half one (incidentally my meal tonight is the same but a lot crispier - with pancakes & hoisin).

    There must be a ketch version that is more similar to the glider rig I mean - much simpler to make (someone said that a canard can be low drag or self-stable but never both).

    Anyway while I'm waiting for the correct terminology...

    Moving away from Aerorig - there are many advantages to a glider rig - but they are normally associated with wing sails (the "Harbor Wing" is the only one I could find. If it really needs those biplane elevators - sometimes double biplane - then I'm starting to worry about hunting problems...).

    Anyway I'm very keen on not needing sheets while I set the panto ama, and possibly losing the plot while also trying to trim a bit it by moving my weight.

    As usual I'm trying to find an easy build somewhere between Aerorig & "Harbor Wing", with a soft-envelope sail ie. somewhere between sail and wing - again.
    I have done some diagrams that seem to show that a ∆ on a mast through the CofE is easier to "glider" than the same sail turned 30deg like ◄.

    I wasn't expecting that - I have listed a few good and bad aspects of each - the worst one being that two 6' sails set on two masts 6' apart will clash if they are oriented ◄.

    I'm assuming full 360 freedom is a safety feature and the tacks of two ◄ could clash if they lost their feathering during a major wind shift (or my stupidity).
    Proa glider sails.jpg

    The only advantage of 2x B (◄) is if it's OK for them to clash very rarely (because it's shunting) - and that would mean an identical sail shape would be OK with up to 3' behind the mast and up to 6' in front ie. up to twice the area (& no extra clashes but possibly worse ones).

    Does anyone have experience of "glider rigs"? Do they tend to hunt a lot?

    I can see there will be big compromises on 'elevator' angles of attack with a soft sail having a different angles of attack at every point - not to mention the wash-out then wash-in effects.

    Would the CofE shift forwards and cause an imbalance when reaching - even though the angle to the apparent wind is held constant on every point of sail?

    I would like to try this hang-glider-with-tailplane as a free-air glider but I suspect getting it to fly level would involve adding stuff that would bust the validity of the test. I've lost faith in scale models too.

    Regards.

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    Default Re: Inflatable Proa


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    Default Re: Inflatable Proa

    A friend of mine builds custom inflatable boat tubes. His company could fabricate a roll-up ama to your dimensions. (They build a stock paddle cat with 12-inch tubes.)

    On arrival, you could get bamboo, etc. for a mast and spars.

    http://www.jpwinc.com
    We're merely mammals. Let's misbehave! —Cole Porter

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    Default

    Quote Originally Posted by Saedilla View Post
    Dreary weather has returned - so I'm back with issues about self-setting sails - I would call them a glider rig, but neither brings up even a fraction of the designs I know are out there, so presumably I've got the name wrong? (again).



    The Aerorig works - it's basically a very soft canard - or a half one (incidentally my meal tonight is the same but a lot crispier - with pancakes & hoisin).



    There must be a ketch version that is more similar to the glider rig I mean - much simpler to make (someone said that a canard can be low drag or self-stable but never both).



    Anyway while I'm waiting for the correct terminology...



    Moving away from Aerorig - there are many advantages to a glider rig - but they are normally associated with wing sails (the "Harbor Wing" is the only one I could find. If it really needs those biplane elevators - sometimes double biplane - then I'm starting to worry about hunting problems...).



    Anyway I'm very keen on not needing sheets while I set the panto ama, and possibly losing the plot while also trying to trim a bit it by moving my weight.



    As usual I'm trying to find an easy build somewhere between Aerorig & "Harbor Wing", with a soft-envelope sail ie. somewhere between sail and wing - again.

    I have done some diagrams that seem to show that a ∆ on a mast through the CofE is easier to "glider" than the same sail turned 30deg like ◄.



    I wasn't expecting that - I have listed a few good and bad aspects of each - the worst one being that two 6' sails set on two masts 6' apart will clash if they are oriented ◄.



    I'm assuming full 360 freedom is a safety feature and the tacks of two ◄ could clash if they lost their feathering during a major wind shift (or my stupidity).

    Proa glider sails.jpg



    The only advantage of 2x B (◄) is if it's OK for them to clash very rarely (because it's shunting) - and that would mean an identical sail shape would be OK with up to 3' behind the mast and up to 6' in front ie. up to twice the area (& no extra clashes but possibly worse ones).



    Does anyone have experience of "glider rigs"? Do they tend to hunt a lot?



    I can see there will be big compromises on 'elevator' angles of attack with a soft sail having a different angles of attack at every point - not to mention the wash-out then wash-in effects.



    Would the CofE shift forwards and cause an imbalance when reaching - even though the angle to the apparent wind is held constant on every point of sail?



    I would like to try this hang-glider-with-tailplane as a free-air glider but I suspect getting it to fly level would involve adding stuff that would bust the validity of the test. I've lost faith in scale models too.



    Regards.
    As a rig for apron where the centre of effort doesn’t move too far your design has potential.

    I do think that there may be too much sail forward of the mast and this may give control issues. The real centre of effort is actually forward of the geometric centre of the area, but for a sail like yours I would not like to say how much. If however you make the elevator further back it would give you more control. I have only ever seen this type of rig where the elevator was very much further behind the sail and on a very stable platform. The also usually have a counter weigh forward to weight balance the rig and get the rig very low rotational friction

    https://youtu.be/PuxpTenBi3Q

    https://www.proaforum.com/forum/viewtopic.php?f=9&t=39





    It might get in the way of paddling but what about the yard at 45 degrees with the elevator mounted on an extension to the yard (poor sketch sorry)




    https://tinkboats.wordpress.com
    http://proasail.blogspot.co.uk
    What I get up to
    https://youtu.be/X9NZEyvpb_Y Streaker dinghy
    https://youtu.be/oni-3rJzxqQ Sail Canoe
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    Last edited by tink; 04-09-2018 at 03:04 AM.

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    Default Re: Inflatable Proa

    One other thought, you will need to ensure structure wise the elevator turns the whole rig not just the one it is connected to

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    Default Re: Inflatable Proa

    Quote Originally Posted by Gary Dierking View Post
    --- I forgot about that design! You can almost envision a version that might get on an airliner. --Wade

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    Default Re: Inflatable Proa

    Quote Originally Posted by wtarzia View Post
    --- I forgot about that design! You can almost envision a version that might get on an airliner. --Wade
    That made me think about a really minimal build...

    My kayak is pretty good value for money at £99 five summers ago - and it has survived use and abuse on 8 flights and 12 weeks of vigorous paddling and sailing (sort-of) - but it's plain PVC material doesn't feel right - it's crazily stretchy.

    I can't stop thinking that a stronger lighter material wouldn't be significantly more expensive (though the cutting and assembly might be double). The benefits of a coated nylon fabric would be something like half the weight for a stiffer hull - and that that would improve again because it could take more pressure.

    Then I thought - why not go for an inflated cylinder with a plank along the top as a narrow vaka with narrower planks either side to cradle the cylinder straight. Either lee or windward boards would work with this and perform hydrodynamically like a classic vaka with its steep V section.

    Then I could add a smaller similar plank-and-cylinder ama with a panto adze board hanging to windward of that.

    It loses the simplicity of the kayak strapped to lee of the sail - because it's stability has to be replaced with two hulls - but it would be a lot less baggage weight to carry.

    Be back later...

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    Default Re: Inflatable Proa

    My mate has a Gumotex Polava and it is awesome, he takes it down places that makes my ply canoe complain with strange creaks and needing a paint job. That said you could replace yours another six times for the price of it. The more expensive canoes are a lot heavier and because of the pressure have a very big pump which may be an issue flying.

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