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Thread: Inflatable Proa

  1. #1
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    Question Inflatable Proa

    Hi everybody - this is my first post.

    I was going to add to the "outrigger & proa thread" but I know some forums discourage late additions to dormant threads, and I'm probably well off-axis on their latest stuff anyway...

    I'm not a sailing expert - or any kind of expert for that matter. "Jack of all trades" might be insulted if he thought I was competing.

    Anyway, I've turned my cheapo inflatable kayak into a minimalist sailing proa that just about works, but I have some ideas to improve it. I joined this forum to get some opinions and suggestions.

    Basically I want (need?) to sail on holiday (renting isn't an option), so I must make any complex parts of the rig fit in standard weight hold luggage, and the bulky basic stuff needs to be made when I get there - from scavenged items and minor stuff you can always buy.

    My first try was a pretty unstable rig but I think I know why and I think I've found a more promising approach.

    I've read about most of the ways it's been done before (but not on this forum). This might be unrealistic - but I mostly understand what I haven't forgotten - if I remember rightly.

    I can just outline my current plans, or add in the last tested version - how is it done here?

    Or is it OK to summarise from the beginning? - in about 40 lines?

    Regards.

  2. #2
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    Default Re: Inflatable Proa

    Posting photos is easy now.

    Take the pic and upload it to your computer.

    Click on the square "insert image" icon at the top of the reply box.

    Select "From Computer".

    Now click on "Select Files".

    That will give you a box where you can find your photos that are on your computer.

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    Click on "Upload File(s)" and wait until it is uploaded.

    Click on "Post Quick Reply". The photo won't actually show full size until you post the reply.

    Save these instructions for further use. Once you've done it a few of times it will become intuitive.


    Welcome to the forum. Beware the Bilge!

  3. #3
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    Default Re: Inflatable Proa

    I have built and tested three proa concepts using two different platforms and for many years was obsessed with proas. From the OP your requirement is a boat you can take on holiday by plane so, in theory, as the proa gives you the maximum boat for the minimum stuff it has potential.

    Some pictures would be a great help, if the above doesn’t work I use Tapatalk which is very easy.

    I presume this is to be singlehanded which was also my requirement.

    From my experience and observations via the net of others.

    Weight steering, my first proa, not successful as I had an asymmetric main hull (vaka) which puts the CLR far forward which is not good. Look at YouTube videos of Proud Mary which weight steered successfully - not me

    Counter rotating rudders, some engineering challenges but basically moves the effective CLR by varying the lift from the front and back rudder. Look up Mi6 proa and this https://youtu.be/0UypTfjDFSc. (This is not my work)
    My second proa used this and worked OK, my rudders where mounted on the side of the vaka and dragged in the water. Designed a system with the rudders under the vaka which I quite liked but never built.

    My third concept had no rudders but a single leeboard which could easily be moved fore and aft to control CLR and was schooner rigged. Steeering was a combination of the board position and the relative settings of the sail. My boat used polytarp sails and these started to limit what I could do with him (proas are male). If I was to build a proa this would be the direction I would go down https://youtu.be/eW078PPgJak

    Good luck and welcome, but I warn you designing and building proas is a dirty addiction and even sailing friends will thing you are bonkers.

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    Default Re: Inflatable Proa

    Sounds like a fun challenge. The fact that your requirements are both clear and stringent should move the discussion along very directly.

    My two cents: There's no more compact sailing rig than a kiteboard kite. I haven't experimented with one on a boat, but others have with varying degrees of success. Besides packing up into a very small package, there's near zero heeling force applied to the boat. Just wonder if that's in the mix of thinking. Good luck whichever way you go with the boat.
    -Dave

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    Default Re: Inflatable Proa

    Following the kite rig suggestion here is a compact sailing concept which may give some ideas?


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    One I designed earlier, I had the idea of making my own tubes which is not as impossible as it sounds - according to the net anyway

    http://proasail.blogspot.co.uk




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  7. #7
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    Default Re: Inflatable Proa

    I thought briefly about this once. I had in mind getting one-half of an inflatable catamaran (such as from NRS) and then finding a smaller inflatable ama. (had this fantasy to flying it to Ireland and sailing out to the Blasket Islands to camp a few days). The inflatable catamaran half would have been too much, though -- didn't need all that volume.

    The Watertribe Organization for a while was selling inflatable amas because so many expedition racers wanted to convert their canoes and kayaks to sailing trimarans, and there was some dismay that the commercial offerings tended to be those tiny teardrop things that are certainty functional but in others sometimes without the wanted volume. Watertribe offered a basic 14 foot version and a more shapely and voluminous 16 foot version. These were produced by "Jack's Plastic Welding" which makes white water rafts though not sold from that businesses's website. (They advertise, if I recall correctly, the ability to do custom work; I have not recently seen them marketing amas for sailing canoes though; perhaps they have retained the designs commissioned by Steve Isaacs of Watertribe and can build them to order?). I used two of the 16 footers to convert my single-outrigger to a trimaran for the Everglades Challenge, and they got a real test when I encountered a squall after I had lost a rudder; they worked beautifully (~400 pounds flotation each, weight = ~ 20 pounds; pretty rugged skin).

    In a past Texas 200 raid event Kellen Hatch flew his version of an inflatable trimaran in and sailed the 200 mile camp-cruise course successfully. I have seen a photo of it somewhere -- I believe it had an inflatable kayak hull with two commercial outrigger inflatable floats -- I believe, a pair of those common teardrop versions, but I do not trust memory. )

    Finally, you might look into these modular break-down solid plastic amas (two pieces, with a third center piece to extend length if wanted) that might hybridize with an inflatable kayak. They break down to pretty short pieces but I am uncertain if they are in accord with maximum baggage lengths on the airlines. Packaraft, or something like that? Cataraft? The website Smalltrimarans.com had a article about them late last year or so.

    To add some "wooden boat" content, I add that I have done lots of napkin sketches of wooden boat concepts that might break down to something an airline would agree to carry for me with extra expenses paid, of course. (think of it as a proa version of John Harris' break-down 10 foot "Expedition Dinghy" which he may by now be selling kits for at his Chesapeake Light Craft). I am no longer sure of the baggage rules, but back then I recalled they had rules to let you bring a suitably packaged surfboard or windsurfer/kitesurfer; I used those dimensions to envision a light-glass-over-thin-plywood outrigger canoe or outrigger surfboard. One version used a surfboard planform with space and screw-out deck ports to stow sail, sectional mast, and paddle, though I was unsure of how thick I would be allowed to make this package before the airline could claim that it wasn't a surfboard any more. :-) In any event it would have been a cold and wet boat, and I'd have to pack a dry suit to go with it. (Christopher MacKay (McKay?) is right now testing a plywood, long and very skinny and minimalist tacking proa -- its long main hull breaks down into three bolt-together pieces with a minimalist ama. It looks very transportable but perhaps not airline-able. It is pretty light and fast. I know this through Facebook but perhaps you can search for him on internet. His videos may be on Youtube.)

    By the way, I can think of nobody who has posted to the proa and outrigger thread who would have objected to you starting a new thread there. That thread was envisioned as a way to collect all posts on that generic subject for easy reference, though several people have started their own threads, perhaps in fear of being lost in the thousands of posts the P-and-O thread has collected. Nor would anybody object to your amateur or newbie status -- on the contrary, we would have welcomed your contribution with interest, praise, and advice. There were only a few bonafide experts posting there (and they were nice enough), and most of the rest, like me, started sometimes with very limited workspaces and skills to try to figure something out for the hell of it; you are our people :-) -- Carry on! -- Wade
    Last edited by wtarzia; 03-25-2018 at 04:42 PM.

  8. #8
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    Default Re: Inflatable Proa

    Thanks for all your replies, especially for the kindness shown towards someone like myself who will (given the chance) always try to do things backwards just for the hell of it. One of the things that made me hesitate to post was the risk of speaking up in front of an audience largely composed of people who know 100x as much about the subject - I've had to do it a few times in my life but it still scares the waste products out of me... Thanks Wtarzia.

    I copied the wrong rigs at first, so progress really only started when I began following Bernard Smith's approach - I read his book at 15 or 16 and it still inspires awe that he was able to outflank so many engineering problems to produce something that's simpler and arguably better. Never forgetting the Pacific Islanders who inspire me just as much - they probably did even better - by getting almost as much performance out of considerably less resources - not to mention the key triumph of producing a proper versatile working craft in the process.

    Both these styles plus my own tests make me feel that keeping the "wood in water" to windward is the way forward for light inflatables.

    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 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!

    I will describe my current rig in my next post (just a few minutes), but first I want to clear something up - I googled Saedilla and found that some people might have this as a given name. That's not me - I'm not an identity thief.

    I chose it because a guy I used to work with grumbled (several times) that I was "ALL IDEAS and no work" - but the whole thing is too long to be a userid - even though it is a fairer description.

    Thanks and Regards.

  9. #9
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    Default Re: Inflatable Proa

    I'll try to explain where this started and where I've got to.

    I have been spending 3 out of the last 4 summer holidays (3-weeks each) in Greece, building and trying out different rigs (made from mostly scavenged materials) to sail my Sevylor Riviera inflatable. I don't have anywhere to sail it the rest of the year round. It would have been easier to source materials in the Canaries, but the North Atlantic is a lot less forgiving than the Med in Summer!

    I'm a nesh warm climate sailor - I've windsurfed and sailed Hobie Cats (rarely) on all my holidays since I was 25 (until my knees started objecting to contorted water-starts in force 3 or 4), hardly ever sailed in the UK.

    If I could drive a truck from my house to the sea it would be great but I can't (no licence and certainly no truck) - and anyway it would be cold and tidal (or worse, a grubby estuary) and it would still be the North Atlantic or somewhere just as tricky.

    Progress in brief: I started by trying to duplicate what I call the "battleship" approach (widely sold as a kit) - various kinds, but they basically build a rigid catamaran framework out of Alu tube, add boards and rig and graft it over the inflatable - effectively a full set of sails, masts, booms, leeboards and rudders.

    My first try was something similar made from some 5mm ply I took with me, 2 "found" wooden pallets, some shelf brackets and a couple of Alu mop handles. Strong 10+ foot canes for booms/crabclaws are pretty much a "commons" resource where I go. I took a small sail 6x6 feet - I wanted to achieve good rig balance before trying for speed.

    It did work, but it was very skittish - even when I doubled the board and fin areas. The problem was that it needed double the areas again to get stability, before it could get to a speed where you don't need that much wood in water. Normally you'd get to this speed by bearing away, but with my small sail that took more sailing room than I had - I needed to get close to the wind ASAP.

    I found the rig was much more stable and manageable with just the windward wood in water, though it lifted out with heeling so crabbing was worse.

    I get the feeling that sailing with leeboards on an inflatable is as difficult as taking a balloon on a stick and trying to juggle the stick to stay to lee of the balloon... The inflatable has no keel, no chines and not even the ridges you'd get from lashing trees together for a raft.

    I know that people have made it work but I always want to outflank engineering problems, not throw money at them.

    I resolved to develop the windward-board idea - using a proa rig so everything could stay on one side.

    I wanted to try for simplicity by adding a long windward board to work like a keelboard, but straight 6' planks are impossible to scavenge where I sail (and buying means ordering in advance). I made a model at home, but heeling lifted the board out, and every gust made the front of the board dig in so it luffed every few yards. It's embarrassing to admit that I didn't realise how different a normal fully submerged keel is. Adding weight aft worked a bit but made it so slow nothing was gained. A lot of this was scale effect - the inertia of the boat & sailor is the main thing lost by a scale model - it goes with the cube of the scale...

    Even so I was put off. An outrigger proa was clearly a better place to start.

    Next holiday I considered emulating a flying proa using a shorter keelboard version of the design above as a wa/vaka and just adding an outrigger to it, but that would still need a good plank, so for simplicity decided to test the kayak without the keel - I just put a small centreboard on a short ama, and just 2' from the kayak.

    Flying this kind of ama would have been disastrous so I only fixed the aka to the windward side - that's nothing like rigid - more like a hinge.

    Since this is basically a dagger across the end of an arm I decided that the best name was "Adze Board". If the sail heels the kayak it lifts the aka - that makes it slope down to the water - it changes the angle of the adze boards to oppose the heel.

    In doing this I was sort-of emulating Bernard Smith's AeroHydrofoil.

    It worked better than anything else I've tried - despite having less board area than even the lee board and fin on the very first rig.

    Because I was running out of holiday and wasn't sure where the CofR was, I made my sail as a short crabclaw with a cross beam I could hold and use as a windsurfer sail. This meant I couldn't get it very near to the windward pontoon so the luffing moment was massive - it needed to move almost the full length of the board on each shunt.

    Sorry I have no photos of this last and most successful rig - it was intended as nothing more than proof of concept, I will try and photoshop one in (my draughtsmanship isn't up to isometrics). I have some photos of my first try - but it's best forgotten because it was less successful than the kit it copied.

    I'm sure a lateen on a central mast over the windward pontoon would be much better balanced, but I'd like to try a more balanced 2 mast rig (to allow paddle-friendly access on both sides) which should further reduce the need to trim the boards. I will try 2 adze boards on the ama for more directional stability. I have a trim method in mind for moving the 2 adze ama so I can let the sails stay put, cope with the luffing moment and still steer without a rudder (I'll probably need to make a diagram tomorrow).

    Regards.

    PS. More things I have learned on the way:

    1) Shelf brackets can't be used in mid-air - unless you ensure there's 1"x2" wood the whole length of both sides so all the screw holes are used.

    2) Copper coins are cheaper and corrode less than galvanized "penny washers" but you need a fresh drill bit.
    Last edited by Saedilla; 03-25-2018 at 07:04 PM.

  10. #10
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    Default Re: Inflatable Proa

    Have you or anyone else had much success with Bernard Smith's ideas, outside of using them to charge down a one way speed course?

    When I was a kid Frank Bethwaite was spending years trying to get Smith-inspired craft to work in front of our house. If I recall correctly, he found that the wind structure was too complex to allow the concept to work correctly, and he then moved to spend ages investigating the variability of real winds. That convinced him that the Smith style was inherently unworkable so he created the HSP trimaran with its fairly conventional rig, which was great fun but took too long to rig.

    Obviously SailRocket proved that if you spend years and huge amounts of money the concept will work in an ideal situation, but from what one can see on the web the Smith concepts may fall into the same bag as simple wingsails - something that is fine in theory but rarely in practise.

    On the upside, the developments in drop-stitched inflatable SUP and windsurfing boards are exciting from several angles. There are also developments in compact rigs that fit into a bag. Could these be the basis for future proas?


  11. #11
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    Back in the late 70/80s Dave Culp developed kite powered proas, I can’t find close up pictures but this is one of his early ones and shows the idea. You could it sideways in your inflatable canoe and build a simple leeward outrigger. Somewhere in the structure a board. Steering would just be moving the kite attachment point for and aft. If you use a harness that would just be a case of moving yourself.

    Have you tried using modelling balloons as bladders for your cheapo kites.




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    Default Re: Inflatable Proa


  13. #13
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    Default Re: Inflatable Proa

    I've made a diagram of the adze board outrigger - it is amazingly small and surprisingly effective - made from a piece of 2' by 1' 5mm marine ply aka attached to a 4 foot 4x2" timber just above the waterline on the hull (bolted into the skirt locks that are like the slotted holes on the back of a picture frame) and at the other end is the tiny ama of 2x2" pine with another 2'x1' ply board set lengthways.
    AdzeBoard.jpg
    I told you I'm lousy at isometrics...

    I haven't shown how the timber fixed to the hull is braced to stop it pulling off or tearing the PVC - but at low speeds a couple of ropes to the other side are enough.

    If the fixing to the hull wasn't so near the waterline the whole thing would tend to dive under at speed, but whatever the angle of the aka, the ama and adze board need to be vertical at rest.

    It is definitely self setting (I've tried to show how the forces fight a heel) - so a massive ama isn't needed to keep it on the surface, because the "hingeing" means the rest of the boat/rig simply can't push it down - but that's no reason to skimp on buoyancy.

    The kayak cost me £99, the ply cost me about £2, the stainless bolts and screws I used cost about £5 for what I took in luggage (and I only used a quarter at most) the pine was all scavenged (as was the sail originally - from a tent), the canes for the crabclaw were free, the mast I used on earlier versions was a 4 euro Alu mop handle, & I simplified the tack of the crabclaw by taking an Alu "V" with me made from pipe I found in a skip - that's the kind of budget I'm aiming at.

    I come from the North West of Britain - we have a reputation for being careful with money but not actually mean - it's good form to be generous with what you've got, and the less you waste the more you have to be generous with. I'm saying nothing about neighbouring areas up there...

    Talking about being generous and the woodenboat policy of not misusing this forum: I don't actually think the adze board variation is patentable - and if it was I'd want to do a Tim Berners-Lee.

    In the UK this post would be enough to stop anyone patenting it (unless it already is), but there's something different about the US system that I don't understand - something about commercial production being as important as original ideas. On the other hand Freeware software seems to be able to protect free ideas for the common good - can anyone suggest a website that explains how it's done in very, very simple language that I might understand?

    Regards.

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    Looks good, I’m sure there is lots of tinkering to do but should get you afloat.
    Re patent I would safely say there is plenty of prior art which would stop someone patenting your idea. The Amateur Yacht Research Society did stuff similar to this many years ago and it is essentially a Bruce foil which was developed about the same time.


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    Default Re: Inflatable Proa

    Hi Tink - thanks for that - I hope there's a lot of prior art and I'd be surprised if such a simple tweak to a windward board had escaped notice.

    The picture looks familiar - I think I'd seen something similar before and I'm confused because that looks like a lee hydrofoil. I looked it up on Wiki and found it says the Bruce foil can be used either to lee as a hydrofoil or to windward to counter heel.

    It may be usable as a pair but one on its own must be a hydrofoil leeboard surely? What's to stop it pulling the boat over when used to windward?

    I'm also surprised if the text is suggesting that boards both sides can lift one side and pull the other - surely you'd only do that much trimming for a speed run? Without verrry careful re-trimming after a tack you'd certainly avoid that issue and simply go for what it would look like - a standard hydroplane rig with both sides lifting - unfortunately there are no pictures and I can't find any to see the spray pattern.

    Bernard Smith showed a similarly steep down-and-inboard angle on his windward foil but it was only on the lower part, the upper part had the opposite angle so it could stop the lower part pulling too deep. There may have been other designs I don't remember.

    Regards.

    PS. I've found something virtually identical to the adze board - its called the Vector foil - it also comes up under "Garadgast" - and it is hinged to an ama. I will attach the image to my next post.
    Last edited by Saedilla; 03-26-2018 at 04:18 PM.

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    Default Re: Inflatable Proa

    Quote Originally Posted by Saedilla View Post
    Hi Tink - thanks for that - I hope there's a lot of prior art and I'd be surprised if such a simple tweak to a windward board had escaped notice.

    The picture looks familiar - I think I'd seen something similar before and I'm confused because that looks like a lee hydrofoil. I looked it up on Wiki and found it says the Bruce foil can be used either to lee as a hydrofoil or to windward to counter heel.

    It may be usable as a pair but one on its own must be a hydrofoil leeboard surely? What's to stop it pulling the boat over when used to windward?

    I'm also surprised if the text is suggesting that boards both sides can lift one side and pull the other - surely you'd only do that much trimming for a speed run? Without verrry careful re-trimming after a tack you'd certainly avoid that issue and simply go for what it would look like - a standard hydroplane rig with both sides lifting - unfortunately there are no pictures and I can't find any to see the spray pattern.

    Bernard Smith showed a similarly steep down-and-inboard angle on his windward foil but it was only on the lower part, the upper part had the opposite angle so it could stop the lower part pulling too deep. There may have been other designs I don't remember.

    Regards.

    PS. I've found something virtually identical to the adze board - its called the Vector foil - it also comes up under "Garadgast" - and it is hinged to an ama. I will attach the image to my next post.
    They do produce negative lift which is how they work to windward, braver sailors than me. The only Bruce foil I saw in action was on a semi production trimaran.
    The vector foil goes a bit further in that in that it is free to rotate so no effected by heel.
    It is well worth building little models and towing them. I am talking 20cm long very simple, scrap wood and I used old credit cards for foils - use the bath, pond or best a running river - you get strange looks but consider it training for when you launch you proa.

    got to go but will post some more thoughts tonight.

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    I have been thinking about what I would o given your design reqirements.
    If i was determined to keep the Proa idea I would use a gibbons rig, just because it is simple, slight compromise on area though.


    In reality though I would go for a tacking proa with a little bench (no more than a bar) on the non outrigger side. I figure you can build a frame that has everything as a structure. I think this will give you the simpliest sailing form the minimum materials. It also won’t matter if you get back winded which can be a real pain for a shunting proa.




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    Default Re: Inflatable Proa

    As Tink said: "In reality though I would go for a tacking proa with a little bench (no more than a bar) on the non outrigger side. I figure you can build a frame that has everything as a structure. I think this will give you the simpliest sailing form the minimum materials. It also won't matter if you get back winded which can be a real pain for a shunting proa."

    --- Some impressions for a comparision:

    With an ama that held up my body weight plus a little more, I could usually sail with ama-to-lee by sitting comfortably in the cockpit, as if the boat were a trimaran, so I never opted for sitting accomodations on the side opposite to ama.

    But with ama to windward, I had to sit on the side seat, period. I have tried sailing in the cockpit with wind over ama in very light wind, and that was OK until the smallest gust (say 5 knots) lifted that 80 pound ama and knocked us down very quickly (and I do not have a powerful rig). -- Wade

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    Default Re: Inflatable Proa

    Thanks everyone, but I'm sticking with my inflatable kayak approach, at least until I've exhausted all the options.

    Especially since Plan B would be a kitescooter from junk with a bladder-stiffened power kite - I think this would be a perfect match for absolutely any inflatable boat - even a big lilo - and be smaller and lighter than anything that isn't helium-filled (the aforesaid kite-bodge would be a hell of a lot lighter - even without helium - than a proper marine kite).

    It's time to move from my promising but limited adze-board trials in the Med to my plans & ideas for the next steps (in bite-sized chunks) where I'm as close to being out of my depth as I ever want to be. Testing all this stuff would be great fun but if I can get some experienced comment to avoid the pitfalls then I will have even more fun, and sooner, and without annoying my wife as much:

    First chunk (of many): I mentioned going for a rig that is balanced as close to the mast as possible - a Genoa + Bermuda rig can do this but is too difficult to shunt (I can't use my simple 'appropriate technology' approach to make a rotating deck for it in any reasonable timescale).

    A crabclaw or lateen is better, but it's still bit tricky to shunt if you are ducking it around (or even over) the shortest possible mast (which may still need stays). It also needs a little more area aft of the mast to stop it "hunting".

    I want to try splitting both booms around where the mast sits (literally along the grain if they are bamboo), so the mast goes through them, and then making a sail pocket which fits around the whole shebang so it has no mast drag, looks like a lateen wingsail, and isn't a wingsail but turns & shunts like a wingsail. It should also be possible (by letting some air in) to achieve an interesting aerofoil shape - weird but still better than an upright cylinder.

    I'm sure someone will have already done this?

    I'm considering making it so the CofE is bang on the mast and using something like a casement window stay instead of a sheet of rope - to eliminate hunting - the downside is no feathering - though I could carry a windsock drogue for emergencies.

    How crazy is all this? It fits my brief and the extra sylnylon weighs nothing (and anyway I've yet to go anywhere in the world you can't buy tarp).

    Thanks again.
    Last edited by Saedilla; 03-29-2018 at 08:59 AM.

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    Default Re: Inflatable Proa

    I've been looking through the thread to find stuff I've promised or failed to respond to:

    a) I owe Tink an apology for not acknowledging the suggestion of modelling balloons for stiffening/floating power kites - I tried to buy ordinary long balloons in the resort, but it is just too small (and not enough kids - thankfully).

    I will definitely take some with me next time - I also need to take a monster bin bag to stow the bladdered kite, though I have a few ideas for plugs or valves to deflate instead. Ideally they should include straws for re-inflation so the emptied balloons can be left in situ (I used strings - dental floss - led through the trailing edge of the kite to get the bladders where I wanted them - don't want to re-do all that between sessions).

    b) I failed to fulfil my promise to explain my CofR-shifting plans - but I find I don't need to - what I was going to call a parallelogram system is already well-known as a pantograph outrigger (oh yes it is... ). Given a choice between CofR-shifting and a leaning mast for CofE-shift...I choose the pantograph.

    Always assuming it works - it normally requires two very strong axles on the ama. I'm going to try a simpler hinge 2/3 of the way down the aka (since the very strong right-angle between ama/board and aka is much easier to do as a fixed unit). This provides only 2/3 of the CofE-shift for a given angle or aka-length - it remains to see if I need to increase either.

    I propose to fit what I can only think of as two spats (streamlined) on the ama which encloses all the rotation while providing the essential stiffness - diagram below (apologies for inconsistent labelling - by top of box I mean underside of cover, by bottom of box I mean upper surface of baseboard).Proa aka-ama hinge spat.jpg
    Last edited by Saedilla; 03-29-2018 at 01:32 PM.

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    Default Re: Inflatable Proa

    The double ended inflatable lee hull will work if you can have a carbon mast inserted (stepped)` through the bladder as a free-standing rig. Body weight suspended` to w/ward on a trapeze (sailboard style) works for stability, if you include an inflatable ama strapped to your butt and tied to the trapeze harness as well.
    Legs serve as the connecting booms ( the Kiato, in correct reference terminology), when your feet are strapped to the leeward inflatable, which serves as a substitute for the waka part of the waka ama combination.

    Lateral area underwater board needs to be combined with a rudder blade, and can swing from end to end along with the sail's wishbone boom when shunting.
    Last edited by Lugalong; 03-29-2018 at 03:40 PM.

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    Default Re: Inflatable Proa

    Quote Originally Posted by Lugalong View Post
    The double ended inflatable lee hull will work if you can have a carbon mast inserted (stepped) through the bladder as a free-standing rig.
    Thanks for proposing a minimum-kit solution, very interesting - but I'm also looking for a bit of comfort and harmony (incidentally the Japanese meaning of "Wa").

    I did consider using two crossbeams (or Alu tubes) under the "pontoons", through two single layers of PVC either side and and over the floor to make a straight connection between the two sides of the kayak - in order to add stiffness and stop the side being torn off when pulled to windward by the adze board - this would have avoided having beams right across the cockpit.

    But I'd never consider pushing anything through the inflatable parts - especially when I can step a mast just 5-11" to lee by running it down the inside of the windward pontoon. and stepping it to a simple plywood "deck" in the cockpit.

    However, instead I decided that putting 3-4' A-frames over both bow and stern would be just as strong and leave the cockpit clearer (they will be joined into one strong perimeter by two gunwale beams - and these provide a good stepping place for a 'midships mast - though I intend to to move onto a two-mast rig after testing because the gap between two masts is so much more "paddle friendly" on a kayak) Diagram below:Proa A-frame gunwales.jpg

    I can see the advantages of using my body to replace as many parts of the structure as possible (I did spend a lot of time windsurfing - I may have even achieved mediocrity - a first for me as I've never been good at sport for its own sake) - but though there may be a good happy medium between windsurfing and what we might call "dinghy sailing" (to be un-specific) I'm looking to get much closer to the dinghy than the windsurfer.

    When I get fed up with the joys of light wind sailing I may start looking at the speed angle - at the moment I'd be happy even ghosting in a well-designed craft.

    Thanks.
    Last edited by Saedilla; 03-29-2018 at 07:00 PM.

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    Default

    Very interested to see how the pantograph AMA / AKAs work out for you. I have drawn lots of sketches of such a system myself and also of a fixed AMA but a foil on a pantograph in the area between VAKA, AMA and AKAs.

    I would go for two free standing masts from the get go, I think they will give you a lot of control. On TP03 I would move the leeboard to position (it moved fore and aft so in your case equivalent to moving the AMA) cleat the forward sail and then steer with the aft sail.

    I would set the masts up so they can rotated 360 degrees, when (and it is when not if) you get backwinded being able to sail steer is very useful

    I have plugged on here before a free CAD package called ONSHAPE, it is easy to use, web based but your designs are in the public domain. I think it will really help you design the boats and resolve a lot of issues before building.

    Here are a few of my designs




    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
    https://youtu.be/eW078PPgJak Proa

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    Default Re: Inflatable Proa

    Quote Originally Posted by Saedilla View Post
    b) I failed to fulfil my promise to explain my CofR-shifting plans - but I find I don't need to - what I was going to call a parallelogram system is already well-known as a pantograph outrigger (oh yes it is... ). Given a choice between CofR-shifting and a leaning mast for CofE-shift...I choose the pantograph.
    I fully agree shifting CLR is a good way to go for a proa, it is best married with a rig where the CE movement is minimal: Balanced Lug, Wingsail, Aerorig

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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    I fully agree shifting CLR is a good way to go for a proa, it is best married with a rig where the CE movement is minimal: Balanced Lug, Wingsail, Aerorig
    Thanks Tink - I'm always glad to find the accepted names of stuff, (language must represent the most greatest consensual accord of all time) - so what I called a rotating deck earlier is an Aerorig. I used one on my 'windward keel board' model earlier but I can't face the challenge of a full-size one...

    The mention of balanced lug sails make me think - they are effectively truncated lateens, but they are quite common in the UK, and I've seen quite a few ordinary gaffsails with yards attached to the mast by a metal ring (can't find the technical term) instead of gaff jaws & parrel - effectively a pierced yard (no name again).

    Obviously a balanced lug with a pierced yard can't dip, but has anyone pierced both yard and boom then 'sleeved' the mast - best done very loosely or even more so by extending the mast pocket all the way to the leach, or even further by wrapping the sail entirely round boom yard and mast (makes more sense for a yard&boom lateen) to make an envelope sail but softer than 'Soft Cell'? (envelope is a better name for what I called a pocket sail earlier in this thread). In a hothouse of sailing eccentricity like the UK I can't imagine it not being tried! So does the 'softer envelope' sail have an earlier name, and if so how well did it perform?

    This is fun! I'm finally starting to tie my disparate scraps of sailing knowledge into a proper 3D mesh (albeit with yawning voids).

    Thanks.

    PS. nearly forgot to say how cool the CAD rendered designs look - I particularly like the y (feoh rune?) shaped mast on the proa - apart from easy shunting by moving the CofE forward, can it be used to get the CofE vertically over the CofR on any point of sail?
    Last edited by Saedilla; 03-30-2018 at 06:23 AM.

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    Default Re: Inflatable Proa

    Quote Originally Posted by Saedilla View Post
    Thanks Tink - I'm always glad to find the accepted names of stuff, (language must represent the most greatest consensual accord of all time) - so what I called a rotating deck earlier is an Aerorig. I used one on my 'windward keel board' model earlier but I can't face the challenge of a full-size one...

    The mention of balanced lug sails make me think - they are effectively truncated lateens, but they are quite common in the UK, and I've seen quite a few ordinary gaffsails with yards attached to the mast by a metal ring (can't find the technical term) instead of gaff jaws & parrel - effectively a pierced yard (no name again).

    Obviously a balanced lug with a pierced yard can't dip, but has anyone pierced both yard and boom then 'sleeved' the mast - best done very loosely or even more so by extending the mast pocket all the way to the leach, or even further by wrapping the sail entirely round boom yard and mast (makes more sense for a yard&boom lateen) to make an envelope sail but softer than 'Soft Cell'? (envelope is a better name for what I called a pocket sail earlier in this thread). In a hothouse of sailing eccentricity like the UK I can't imagine it not being tried! So does the 'softer envelope' sail have an earlier name, and if so how well did it perform?

    This is fun! I'm finally starting to tie my disparate scraps of sailing knowledge into a proper 3D mesh (albeit with yawning voids).

    Thanks.

    PS. nearly forgot to say how cool the CAD rendered designs look - I particularly like the y (feoh rune?) shaped mast on the proa - apart from easy shunting by moving the CofE forward, can it be used to get the CofE vertically over the CofR on any point of sail?
    There have been many attempts create a sold wing sail which is essentially a pocketed balanced lug sail. There will be a lot more of this sort of stuff with the next America’s cup going this way.

    My Y rig is designed to control the position of the CE independently of the angle of incidence of the sail - this would allow the steering to be achieved by rotating the mast.

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    Default Re: Inflatable Proa

    Quote Originally Posted by Lugalong View Post
    The double ended inflatable lee hull will work if you can have a carbon mast inserted (stepped)` through the bladder as a free-standing rig. Body weight suspended` to w/ward on a trapeze (sailboard style) works for stability, if you include an inflatable ama strapped to your butt and tied to the trapeze harness as well.
    Legs serve as the connecting booms ( the Kiato, in correct reference terminology), when your feet are strapped to the leeward inflatable, which serves as a substitute for the waka part of the waka ama combination.

    Lateral area underwater board needs to be combined with a rudder blade, and can swing from end to end along with the sail's wishbone boom when shunting.
    Talking of bare-butt minimum kit (this is very much an aside comment) I did once consider connecting a kitesail to a cable (faired) through the water surface to a hydrodynamic version of a kitesail - something like a model glider around 1/32 the span of the kite (to get 1/1000 the area - reflecting the density difference between air and water).

    The cable could pull just about anything that could float - a swimmer, a swimmer on a lilo (air mattress), whatever.

    I thrashed my brain close to death with it, but decided a computerised fly-by-wire hydroplane would actually be easier to design and make than an incredibly finicky appropriate analogue technology version - the nearest comparable system I can think of would be the pendulum-linked control surfaces used in the 1960s to make true scale models fly themselves despite the square-cube law (or "s-q curse" as some modellers called it). They were never very successful.

    On the other hand I thought that the gramophone tone arm was a similarly complex force-balancing problem - until a better engineer than me invented the "well tempered arm" https://www.stereophile.com/tonearms/485well/index.html

    Ho Hum...

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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    There have been many attempts create a sold wing sail which is essentially a pocketed balanced lug sail. There will be a lot more of this sort of stuff with the next Americaís cup going this way.

    My Y rig is designed to control the position of the CE independently of the angle of incidence of the sail - this would allow the steering to be achieved by rotating the mast.
    The 'softer envelope' would be a lot easier to dismantle or furl & ship than a wing sail*. I looking forward to finding out how manageable it is all-round - compared to a simple yard&boom lateen, hopefully this autumn when I try it.

    *The "Soft Cell" sail http://sailinganarchy.com/2014/07/23/soft-cell/ (video https://www.youtube.com/watch?v=a8UC...ture=autoshare) looks easy to collapse but I wouldn't want to dismantle and rebuild it for anything except a long winter break - and that's assuming all those battens are sleeved.

    Soft Cell does show there are valuable midway points between traditional sails and extreme wings - Soft Cell is very much at the high performance end, the 'softer envelope' idea is just aiming at an easier life! It's still possible that adding a few battens to 'softer envelope' would improve the aerofoil enough to really pay off.

    Your Y rig looks great - have you tried it yet? It looks like it would feather very nicely, but if the arms ever got in the way of the sail it would be a very small tweak to lose the upper arm and make the lower one stronger to step a stiffer mast - though I suppose it would probably end up heavier.

    Hold on - am I missing the point - is there a sheet on the sail or is the angle set only by the mast?

    Regards.

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    Default Re: Inflatable Proa

    I have to say a soft wing sail is a whole development in its own right, there has been much discussion here about how bad the bad tack is with a balanced lug and many people say they can’t tell the difference from what I remember.

    Have you seen the inflatable wing sail, http://inflatedwingsails.com/en/concept/. I think inflating has to have legs - transformed kite sailing, inflatable stand up paddle boards are awesome, there is also an inflatable windsurf mast sail combo https://i-rig.com/en-gb/. Obviously they are used for tents also and you can buy spare bladders relatively cheaply which has interesting possibilities for home bulilders 390cm for £20

    https://www.winfieldsoutdoors.co.uk/vango-airbeam-airspeed-replacement-tube-390-x-13cm/?gclid=CjwKCAjwwPfVBRBiEiwAdkM0HSWdadYrohgi7Khrf4M YUeVyY_mDOsokBiUiGHX-6JKM9LqysKhNXBoCjAcQAvD_BwE#fo_c=2257&fo_k=d280d3b b150e8fab3f166ca26ddf94c5&fo_s=gplauk


    You can even buy your own valves cheaply if you reliably manufacture the tubes


    Yes there is a separate sheet for the sail so the mast controls CE and he eve steers, the sail is completely independent. This is a very old lugsail model https://youtu.be/JyE0FsI_GAQ

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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    I have to say a soft wing sail is a whole development in its own right, there has been much discussion here about how bad the bad tack is with a balanced lug and many people say they canít tell the difference from what I remember.https://youtu.be/JyE0FsI_GAQ
    I've also heard lateen and lugsail sailors say the bad tack is hardly noticeable but I think this comes down to 3 things.

    1) If it handles OK and you lose a knot ot two how are you ever going to know (without GPS)?
    2) It's a different tack with a different wave pattern - so even if you know your speed how the hell can you be sure what the speed should be?
    3) Most of the drag comes from the mast anyway - have you seen that diagram showing drag from a mast next to the same drag from an aerofoil? The aerofoil is surprisingly large and tubby, at least 3x the width of the mast and apparently everything is included, skin drag, the lot.

    I can't find it so I've done a mock-up from memory (possibly a mockery). I think it was in proa-stuff somewhere, I think it was before I was looking at wingsails.
    mast & foil - same drag-.jpg
    Some would say laziness is involved - but since I think point 3) is the most important, that would mean that these guys are just being realistic...

    One of the nicest thing (for me) about a proa/riwuit etc. mast leaning/canted fore or aft is that the cross section becomes oval - and the yard of a lateen/lug must be a longer ellipse approaching an aerofoil.

    http://smalltridesign.com/masts/rig-mast_options.html contains a table of roughly estimated boat-vs-wind speeds for some rigs - worth a look.

    They have:
    A) mast + sail at 0.85
    B) rotating mast (elliptical) at 1.0
    C) rotating wing mast at 1.1
    D) luff pocket at 1.3
    E) double sail rotating mast at 1.6 - an envelope. Halleluja!
    F) AC45 wing sail at 2.4

    The only thing about this that really worries me is that I'm taking the 'soft envelope' back in time to a rougher technology - to a place where it never caught on... despite good people who could see all the benefits and did good work.

    However my best hope is that my objectives are probably different:

    Easy, quick build from easily sourced, disposably-cheap materials, easier sailing when it's done. Easy dismantling would be good and seems achievable. I'd even tolerate a slightly worse perfomance but it seems unlikely. Better performance would be great but it's a lot further down the list.

    Obviously inflating can give you a perfect aerofoil to achieve that 1.6 or more, but I'd like to spend a few minutes on the beach to see if a little leakage through the luff would do any good - like a powersail.

    As to making an inflatable into a stiff spar - it's too high-tech, high cost for me - definitely not a disposable asset like my lowly kayak - and when that does go west I'm hoping to be able to use the rest of the kit to sail something even simpler - maybe even a rubber ring (or maybe two)!

    The test model in the Proa Sail video was great - my kind of analogue - it makes it easy to see how the 3D render would work, and with any sail - I can now see how it moves everything safely to lee away from the cockpit. I saw some other Proa Sail videos with leeboards moving far enough to counter such a CofE move to lee.

    I get the impression that everyone designing proas is familiar with this problem, though my problem is that the adze-board IS my CofR - there's no keel or anything else biting briny, and even putting my mast(s) on the windward edge of the hull and using sails halfway to wingsails still means the luffing moment to the CofE acts over the gap between hull and adze-board - at least 2 feet, though the water drag from the kayak is acting against this on a 2' longer moment.

    I still can't grasp what sort of distance I need to move the panto-ama aft to counter the luffing moment - bearing in mind that lying in the kayak (to reduce drag by smoothing the hull) is just going to make it luff up more... I find myself praying the kayak never planes and spoils a nice reach!

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    Default Re: Inflatable Proa

    Quote Originally Posted by Saedilla View Post

    I get the impression that everyone designing proas is familiar with this problem, though my problem is that the adze-board IS my CofR - there's no keel or anything else biting briny, and even putting my mast(s) on the windward edge of the hull and using sails halfway to wingsails still means the luffing moment to the CofE acts over the gap between hull and adze-board - at least 2 feet, though the water drag from the kayak is acting against this on a 2' longer moment.
    could you post a sketch of the plan view of the this, too many words for my visual brain

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    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





    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
    https://youtu.be/eW078PPgJak Proa

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    Default Re: Inflatable Proa


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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    could you post a sketch of the plan view of the this, too many words for my visual brain
    Will do - I'm going to try to avoid drawing the boat in a force diagram because just looking at its shape will convince most sailors that the kayak shape has some kind of preferred direction of movement - it doesn't - in fact if one person is sitting it in it the whole thing becomes a big shallow V with the bow and stern almost out of the water - in this configuration it 'wants' to go sideways, and it takes a substantial skeg to stop it. In fact the Sevylor skeg is only big enough to make the kayak behave well with two paddlers - otherwise it needs something DIY twice as big (that would cost 1/4 the price).

    In the diagram I will draw a blob for the boat - maybe a cloud or a photo of a potato - to stop it confusing the issue!

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    Default Re: Inflatable Proa

    Quote Originally Posted by tink View Post
    It's a close match to my design - especially as the Vaka has no keel - except these are Atlantic proas relying on a voluminous buoyant ama to lee - the canted boards are lifting the ama so it can be smaller - but the sheeting and freeing forces are still very useful - I will add them into my diagram.

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