|    You are operating on the premise that we are comparing a short ply hull with a long ultra light weight composite one. 

You are putting words in my mouth.
My point is a longer hull can be lighter, and a shorter hull can be heavier.. You have not shown an error in that thought, nor recognized the truth of it.

| A longer hull inherently has more material in it if it is to have useful volume.

If these are your premise, than they are yours. They are not everyone's. There are many proas that have very fine lee hulls that have very useful internal volumes. If you cannot imagine a use for this volume , that's fine, others already have.

| The most efficient layout structurally and in terms of surface for usable volume is the most compact.

A harryproa is less compact and more efficient, lighter and has a more voluminous interior. You should question your premise.

| The finness ratio necessary for a multihull of any kind to be efficient generally dictates that the forward end at least if not the aft end also are of limited value other than displacement and storage of light weight items.

'Generally' does not apply to the specific. And we are talking specific boats, and at least one of these boats violates this generality for great profit.

|     The idea that a 40' proa will be equivalent of less in weight, cost, and time to build than a 30 foot cat, both boats having equal usable internal volume is in my opinion unrealistic.

How do we go from opinion to knowing? All it takes is facts and thinking. Perhaps you are right. Perhaps a 40' foot will not work. How about a 50'?

Or better yet, have a conversation with Rob. I mean you have been rather kind to detail your SOR, in rather detailed fashion. He might be able to whip something up.

|Materials and weight tend to increase with the cube of the length on a boat.

Only if you assume similar compact structure. Check your premise.

|  The estimate of a 25% savings in weight between plywood and foam sandwich without compromising structural integrity seems to approach reality IF the boat is designed specifically to get the max weight savings by utilizing the material to the best advantage.

Perhaps. I can't speak to it, as I do not have the facts at my disposal. I can speak to the fact that, for any given payload, Robs designs beat that 25% estimate all the time.

| The fact remains that I simply do not want a 40' boat as a single hander, or as a builder.

Then I retract everything I have said. I cannot and will not persuade you into any given thing. Especially one you have now declared you do not want..

I thought we were discussing the criteria, parameters, and ideas, of boat design selection and having fun doing it. It seems you thought I was badgering you into something you do not want. No harm, no fowl. I'll stop now.

| I'm somewhat open minded, but the fact remains that the boat I want to build is a 30' cat, and I do not see anybody swaying me on this in the foreseeable future.

You are truly blessed if you know what you want. Congratulations!

|     The idea of doing a flat development and merely folding flexible corners may be feasible in some situations, but it clearly is not in this case.

What is clear to you is not clear to me. As I said, I may be getting this wrong. I do often.

| Anybody with the most basic sense of geometry can see this. The stuff of fantasy.

I cannot speak to other peoples sense and fantasy. I have enough trouble with my own. But here is a source for my thoughts.

http://harryproa.com/?p=726

"The ww hull was originally to be built in moulds, but is now a very tricky, owner (Steinar) designed flat panel build, although looking at it, you would never know."

Take a look at the pics. That's how I want to build a boat. Having loki help me with seems legit.

| 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.   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.

Well build how you like and feel comfortable. Obviously I prefer the geometrically nonsensical technique.

|     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........... 

I cannot speak to either technique. I know this Intelligent Infusion seems pretty great to me. Perhaps another reader will be along to advise.

|"idiotic infusion"???
|
|    Speaking of "flat development", developing a hull shape and formers that is compatible with flat sheet construction, is an interesting challenge.    I've always had great respect for people who design smooth shapes in three dimensions, and that respect is much greater than it was just a few days ago ;-)

Well, if you map the curve of the delta in your thinking, it seems to point to some premise shattering.

Rob and Steiner are the guys for making flat sheets into boats.

|     Your arguments for the Harry Proa are falling on deaf ears ;-)

You misunderstand. I was not arguing for you to build a harry proa. I was asking you to explain why, using your criteria, a harryproa does not fit your needs better. You were kind enough to answer. Thank you.

Perhaps a subtle difference to you. A huge one to me.

And, I ask these questions because I do not know why a harryproa does not fit my needs better. Perhaps you have thought of something I missed. But it appears not.

I do not much care what I build. My restrictions are strictly practical not unquestionable.

|    As far as carrying sail outboard, a reach beam reach is about the only point of sail where the main portion of the sail would be carried outboard.
|
| In ideal sailing conditions there is no chance of a wave catching a wave, but conditions are often less than ideal.   I would want to be able to shunt if I had a rig like Robs Aero Rig, or the junk. rig I'm planning to use, on a single mast in one hull so that I could sail with the long end of the boom over the boat.  

If anyone is reading this who has any direct knowledge, or feels if they can speak to the topic, can you address it?

Let me think this through. If a sail is full, it must be to the lee of the mast, right? (Ignoring DDW sail as a parachute situations.)

If, on a harryproa the mast is in the lee hull and the sail is to the lee of the mast, the sail is over the water for most points of sail, right?

Afaik, on a harryproa, if the sail is over the boat, your lee hull is to windward, which is obvious derp. I mean with the schooner rig or una rig. The balestrom/Aero rig are a different thing. Even then, the aft half of the rig is over water all the time, I think.

Perhaps the split rig junk (on a harryproa) is more like the Aerorig/Balestrom, in that the fore sail is over the boat and the aft is over the water?

| I will have a low aspect ratio rig & relatively short mast, which means that the sail will be fairly square, and the boom long.... about as long as I can get away with and still be able to sheet with a decent angle.    My idea is to sheet through a traveling block from the two outboard aft corners of the boat.   As there is no need for down pressure as on a Bermuda rig, this can all be fairly light, and travel from one corner to the other via a line rather than a track.

Ah. Interesting. Why not a taller mast? And a better aspect ratio?

|     I've been toying with the idea of completely reversing the sail.  As the mast on a junk rig is not the leading edge of the sail, and in
|fact on the Aerojunk is not involved at all, I don't see a lot of reason why the head sail needs to the the smaller portion.    Sheeting loads would be double if sheeted to the short ends of the battens, but that's not a bad thing and still far less than on a bermuda rig where there is zero balance area, and tension is needed to shape the sail.

Tom Speers on boatdesign.net has some posts on split rig wig sails. I don't know how relevant they are to a split rig junk, but take a look. He suggests the balance point should be around 20-40 of the total cord length. I imagine you would want the mast forward of the balance point, but I know nothing.

|  It might look a bit strange to have a backward sail,

You are building a split rig junk sail, and you are worried about how it looks? Looks are not the parameter to optimize, IMHO.

| but realistically if one looks at a masthead Bermuda rigged boat, in many cases the head sail is larger than the main.   The wind doesn't care.  The important thing is that the camber is distributed ideally for max efficiency.    One big advantage in doing this is that a tension based automatic sheet release could be used so that if one was napping below, and was hit by a sudden violent gust, the sheet would go free in stead of the boat being knocked down.

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 you?