Thanks guys, that helps to clear up the fog a bit. Getting close to the point of being able to put together a model, then do the sanity check of running the numbers and seeing if the dimensions and layups come out close to what's commonly used in practice. Then make a few bits and break them, of course. <img src="http://www.catsailor.com/forums/images/graemlins/tongue.gif" alt="" />

Looking, while writing this, at a picture of Hilfiger's X40 doing a stuff/pirouette at the iShares Cup...the thing appears to have landed without damage; somebody certainly seems to have done the math[s] right!

Or over engineered <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

Or overbuilt <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

Slosail,
Hope you proceed with your design and don't worry too much about certainty of loading. I have spent a whole career managing submarine design for the US Navy. Our submarines are arguably the most over analized, over calculated, and overdesigned vessels in the ocean and still .... we use rules of thumb for everything from wave slap to corrosion allowances. Not as scientific as you might think. All the big yacht design firms do the same thing.
To design my trimaran, I looked at structural loads at the maximum righting moment and applied what I considered reasonable factors of safety for the rig and the boat structure. Although not too often, parts I have designed break when sailing because they may not have been quite strong enough. If nothing you design ever breaks, you are too conservative and will pay the penalty in poor boat performance. Of course dosen't apply to the structural integrity of the entire vessel - that must be reliable.

Kevin

Thanks for the note. I've been in mechanical engineering for many years, and the interplay between calculations, rules of thumb, and experience isn't something new. However, because of safety concerns and the, um, rich cultural heritage of sailing, it seems that boat design involves a few less calculations and a bit more working from experience than, say, land vehicle design. Not that this isn't appropriate...If someone's going to sail with, say, family members then better to add a few pounds than have the thing go all Groupama offshore.

Then there's the experience of doing a bunch of calculations, saying to oneself "I could easily build that at half the weight", then finding out that there's a really good reason for the extra weight. ("Oh, people don't want the keel to buckle the first time they hit a sandbar...")

Anyway, I'll certainly proceed with a design...might even work up the nerve to build it. <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />

Sorry I'm late here. There is one thing that worries me a little bit with the expanded polystyrene building foam. Check how well the glas or carbon is adhering to it, I had some bad experienses of delamination with this kind of foam.

expanding foam is a definate no-no. Lacks shear strength (I've tested it) and soaks up water.

There are updates on Kjell's website, he finished applying the foam.

http://www.trinardo.com/y.a.t-yetanothertrinadobuilding2

Have two Blade F16 hulls that I don't know what to do with, would it be possible to do the same?

*gaaaahhh* Certainly you can hear my screams all the way to Finland?? <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

Yep, but they are too heavy (26 kg) to build a competitive F16 cat and there is not and will not be a F16 class in Finland in the near future.

Carbon mast, foils, ruddersystem and careful selection of sails and blocks.. 23kgs is the target weight I think and if the hulls are 6kgs overweight in total that is no big deal. I would be happy to sail with a platform 6kgs overweight. Let me know if you want to get rid of those hulls and I'll be happy to discuss solutions with you.

Sorry for hijacking the thread, I'll go away now.

Yep, but as I already have an alu spar of 18 kg sold for the Blade it's too much adding 3kg to everything does make a real fat one...
If I build a tri I can get down the weight of the rest <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Ah, I see. Well, I it was worth a shot. Keep me in mind if you want to get rid of the package..

Gents,

I apologize for butting in, but, the Cat hulls you mention are exactly what I'm hoping to utilize on a homemade Tri.

What's anyone seen, or heard of as far as utilizing existing Cat. parts, or even any form of Mono hull for the center as part of a decent Tri? Thanks

Mark

I think there are people around on this forum that are capable and would be interested to knock down the plans for a modern centralhull for a resonable fee...
Im interesting in building a small tri and and would be ready to paerticipate in the above mentioned fee

There are some good stock small trimaran designs around. I think both Chris White and John Marples offer them.
If you wanted to make something from recycled beachcat hulls and something (??) for the main hull, what are the major aspects you need to cover to ensure you get something sailable when finished? My short list would be:
1. Is there enough righting moment available for the rig?
2. Is there enough lateral aera for it to go to windward? (at least 12% of sail area)
3. Is there enough rudder to provide seerage? (at least 4% of sail area)
4. Does the center of effort of sails (centroid of both sails together) lead the center of lateral resistance (cenrtoid of rudder/boards together) by at least 8%? This ensures balance under sail.
5. Will the boat float on her intended lines? Need to check fore/aft bouyancy distribution.
6. It the platform strong and stiff enough to resist normal sailing loads? Look at what works for other designers and follow their lead.

This is my list of the top six. Did I forget anything?

Kevin

Lots of interesting tech. questions for a newbie, but that's good!

One of the best pictures of a "homebuilt tri" I've found so far is the 'Trinado', which uses Tornado hulls.

Based on the comments here, and the Trinado's builders comments about a bit too little righting moment, would a smaller main hull not be the answer? What particulars would be involved in choosing a preexisting hull for a good match if there is one? I'm aware that all this reference to salvaged parts "on the cheap" may read as sort of pathetic, but the upgrade to a quality boat (read: tamer, drier) of 20-25' from my WindRider Rave without over a $20K investment is most realistic.

Next question to me would be what's the best, (reasonable $$) option for a good folding assembly?

Mark

To answer your last question I think that the Astus telescopic system meets best up to your specs. http://www.exaqua.co.uk/
I don't by that say that it's the best, but I'ts simple and cheap to make.

Ignoring any rigid dollar amounts for total project cost, and instead planning on a boat that could be trailered to a ramp and set up solo quickly, are the specific hull connectors going to be the most critical item to an easy set up? And, are they something one can shop for?

I know my 'Rave's tube mount Ama's with it's bolts, stays,tensioning lines,tramp lines,etc. take some time to put together.

Are the fold out Ama parts that(Farrier?) has on their web site the only ones of that type for aftermarket available?

I believe from fleeting memory they were $10-$15K for all the associated pieces. Sound about right? $@&##@$$$!!

To me, being able to pull up, and sail away quickly would define a usable (and likable) boat. That's probably worth paying for. But only so much.

Bottom line: A quick set up boat would perhaps be #1 criteria for choosing a "trailerable" Tri to me.

Ideas?

Mark Iverson