Rob:
    The suggestion that a complex shape such as the two panels of the hull side, and the bottom on the KD 860 could be infused flat and folded at the seams is patently absurd.  The only time this can be done is when the finished seam angle will be a straight line.  In this case, both of these seams is a compound curve, and therefore these structures can be built one of two ways.  Either as 3 separate panels joined at the seams later, or in a mold that begins with the desired shape.

    Neither method is truly simple, but I personally would prefer to put the labor into the mold.   Below is an image of a hull side from Pete  Hill's Oryx, which is the shape I prefer due to the "wing" or knuckle, which adds interior volume, and a sense of more interior space, and the possibility of putting the ports high enough to provide useful side view from on the bridge deck.  In this case they were obviously placed so the person in the galley could see out.    It of course has the additional advantage of greater reserve buoyancy in a knockdown situation.   This boat is 10M.    Next to it is a rendering of the stock KD 860 hull.  Quite obviously neither of these hull forms could simply be infused and folded as was suggested in a previous post.  The compound curve of the seam is easily visible in the rendering.  On the right is a Tiki 38 hull under construction.

    I must admit that I'm completely unfamiliar with modern MDF.   To me it is particle board, which is stiff and inflexible, and is often used as floor underlayment in cheap construction because of it's rigidity.   I will have to make a trip to the lumber yard and have a looksee.    Also on my agenda is to investigate the cost and availability of Highload 100 and Formular XPS 1000......... The list is getting longer.     Obviously I'm going to have to do some small "intelligent infusion" projects in simple and complex molds............My canoe trimaran project is an ideal place to experiment, as I need to build amas for it.

                                                   

    I'm not sure if a catamaran is a symmetrical proa, or a proa is an assymetric catamaran  ;-)      My 30' criteria is pretty well locked in stone.  It may not ride as nicely as a 40 footer, but will probably ride at least as well as a 40' double ender such as a proa.   It's well established that the distribution of the displacement, combined with the optimal rocker, and a transom stern damp out most of the hobbyhorsing.   Note in the rendering, that this hull is built specifically to these criteria.  In comparison, the Wharram Tiki 38 hull is more or less symmetrical with a canoe bow and stern.  I would suspect that the KD 860 would have a better motion than the larger Wharram, as well as having a shallower draft, and a generally better shape for living in.   The Wharram has a LOT of bilge. area below the sole, the KD 860, almost none, and this is a bit of a liability, as the bilge is where heavy stuff should be stored, as you said.   I'm not tall.... not much over 1.65M, and looking at this suggests raising the cabin sole to create useable bilge space, sacrificing some unneeded head space.   I mentioned this previously.    We are on the same page as far as weight distribution.


    An interesting thought about asymmetry, is that as I mentioned before, I see no fundamental reason why sails could not be reversible........... Imagine designing a boat so that the sail was in one hull, and operated within an arc of perhaps only 120 deg, from slightly outboard to across the deck.  The challenge would be the sheeting, and the location of the camber, which does not appear to be as big a deal as one might think.   I'm of course talking about the Aerojunk split rig again.     Of course you could fly the sail inboard or outboard...... maybe you want sun shade, or sun on the solar panels ;-)



    You make a good and valid point(s) about beaching keels.  My concern is concentrated point loads on the hull bottom, which on the flat bottom I'm talking about could be an issue...........  Getting tires hauled under the hulls on a catamaran could be considerably more challenge than on a monohull.... The bridge deck kind of gets in the way ;-)


    There are some simple sheet release systems that are extremely reliable.   The simplest tension based release uses a cam cleat mounted so that it tilts under tension such that the sheet simply lifts out of the top of the cleat. There have been a number of commercially made angle based releases, at least one of which has a very good reputation, but availability is a problem.   I'm interested in your version...... are there photos somewhere?   As a single hander, I consider some sort of auto sheet release important.   Being there to release the sheets in person is best, but.................... Let's be realistic ;-)


                                                                                                                                                    H.W.


On 05/27/2018 09:11 PM, Rob Denney harryproa@gmail.com [harryproa] wrote:

 

Interesting discussion.  Thanks for keeping it civil.  A few comments/corrections

|    The problem that keeps cropping up for me is payload.

​Payload on a cat or tri adds to righting moment, which means increased beam and rig strength.  The harryproa approach is to design for a given righting moment, then put anything extra in the lee hull where it will slow the boat down (the same as it will on a cat or tri) but not require any structural changes.  On small boats with relatively large payloads (eg live aboards for independant owners) the difference will be noticable.  It is lighter and safer to get rm from width than from weight.

I don't know this is true. I assert that it is cheaper to build in foam and glass, assuming Intelligent Infusion. One still has to glass both sides of the plywood or the foam. Infused glass and foam takes much less epoxy, and that is the most expensive item. No throw away frames or jig to build or align, just a flat table and sawhorses. Certainly work saved counts for something.

​While it is possible to build from flat panels and fold them https://www.youtube.com/watch?v=DfhdRfBTt8o Intelligent Infusion uses a simple mdf box ​mould. See the bottom of http://harryproa.com/?p=424

|A proa will not fulfill my criteria for the same reason a trimaran won't,

​A proa may not fulfill your requirements (it does, except for the one that says you want a 9m cat), but it will be for different reasons to a tri.  Tris are not only ​more payload sensitive (see above), but almost a third of them is doing nothing at any given time.  The payload available from eliminating this third is larger than that from switching from ply to foam.

Asymmetry doesn't bother me, in fact I'm attracted to it.   However it really doesn't work to put the mast in one hull of a cat.   ​I don't see why not, assuming there are no headsails with sheet leads to leeward of the hull.  The original Elementarry had a deck sweeping boom which was fixed to the mast.  We never caught a wave, but when the hull was flown far enough, it would hit the water and could not be eased, resulting in a capsize.  The solution is a wishbone boom high enough off the deck to not hit crew's heads and to give visibility underneath.   The weight of the rig is relatively low.  It is not necessary to live in the opposite hull, just store some heavier items there.  Anchors are the obvious ones, and a decent fall for the chain and warp into the depth of the hull rather than the bridgedeck is a bonus.  Batteries and tools will usually make up the rest of the weight balance.  ​ Did I read rob uses pvc pipe?​​ ​   ​ I like the one seam, as it would be covered by the 6" sacrificial wood beaching keel I envision.   Not all beaches are sandy and rock free.​ I am a tyres for fenders fan as they are cheap, can double as sea anchors/drogues or towing springs, provide something to sit on on rocky beaches and something to bounce on on surf beaches.  If the hulls are shallow and rockerless tieing them underneath is quick and easy.    Beaching keels need to be very strong  (perhaps impossibly) to ​handle​  the boat being washed sideways in a grounding.   ​They make scrubbing more of a chore, slow the boat (more wetted surface) and increase the draft to the point that sitting on a surf beach in water shallow enough to have little destructive power may not be feasible.  They also increase the likelihood of tripping in large beam seas.    | What I see as the most realistic build system is to build a three dimensional mold of an entire hull side on it's side on the floor or a table using temporary formers, stringers, and flat sheet material with a suitable gloss surface, the intersecting corners being radiused, and sanded smooth, as well as the joints, and any fasteners. The entire thing coated with a mold release, and the layers of the sandwich added and infused ........... no small undertaking.  The knuckle.... thanks, that was the word that I was looking for..... and half the bottom, more or less lock in the contour.   | Each mold would make two hull sides, and the formers would be reversed to make the other mold.  The bottom could be made in halves as part of the two hull sides, or made flat, and added later, resulting in two full length seams instead of one.   ​Pretty much how it is done, but there are a lot of labour savings you have missed.  ​ |     The second alternative of course is to just build 3 long flat panels for each side of each hull, plus the bottom and have full length seams.  A far simpler method, but far more finishing labor.... at least 6 seams in each hull, plus the seams for attaching the coach roof bridge deck, and bridge deck cabin, etc........... |"idiotic infusion"??? ​Yes.  ;-) Yep. I think I might prefer the inherent dumping of a gust by the mast proper, via flexing. Or a greater righting moment. But an automatic sheet release makes sense, but I don't know how they work. Or how expensive or durable they are. Do y ​ou? T he latest iteration of our wand released sheet is near free, ​near idiot proof, ​has little to go wrong,  works at a preset angle of heel or pitch and works even if the sheet is jammed on the winch or wrapped around the crew's ankle.  ​ ​

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