Lee wants a new trimaran design...

[Woxbox]

Re: Lee wants a new trimaran design...

What's been said, plus it looks like the two bodies are squeezed in there pretty snuggly. What happens when elbows fly to trim the sheets quickly?

On the performance side, if you lengthen the hull only, you'll get a noticeably better top speed out of the boat than if you make it both longer and wider. Plus, having the bodies sitting out to windward for stability.... There are reasons your suggested arrangement isn't done.

On the other hand, if comfort is favored over performance and you really want first and foremost the feel of sitting behind a dashboard in a wind-powered runabout, why not go for it. But if so, give the sailors some elbow room and approach the project with a realistic view of what performance can be expected. It could be a fun boat.

Iceboats have been configured as side-by-side tandems, but of course there are all sorts of other factors that come into that.

[Lee.007]

Re: Lee wants a new trimaran design...

Todd and Dave,
Thanks for the advice!

Since I have attracted Todd's attention, I was thinking of about a 85 Square foot mainsail, bermuda rigged, and maybe add a jib. What would you think the max sail area I could safely use would be, Todd? I would like to keep the mast height 22 feet or less. I plan to get sailrite to design and cut me a sail, then I sew it together. I also plan to make the mast a birdsmouth out of SPF lumber from local lumber yards, same for the boom. And I am kind of intrigued by the idea of a bowsprit.

I was tipping over into the idea of putting solid "wingnets" made out of laminated cedar boards, about 3/4" thick, on the akas to sit on, with a back supporting "handrail" wrapping around. Making a U shaped seat with the bend of the U crossing the main hull where the seat normally would be. And y'all are right, those two models I got are average sized 6 foot tall men. It is a tight fit. Some of the tight fit look comes from the fact that the models have their legs spread quite a bit. In fact, if you look closely, the outboard leg is actually sticking through the hull panel.

So I was trying to do something I could build fairly quickly, before I build a Sea Clipper 20. And yeah, I know there are maintenance concerns for the wood look, but the risk is worth the benefit for me. You know, the more I play with stretching the Drifter, it is starting to look just like a Sea Clipper 20!! I don't think the Sea Clipper is as light as the Drifter though. So, I think what I will do is like Dave said, stretch the length to give me a little more buoyancy, put some cedar wingnets on the akas, pin the akas so they pivot in for trailering like the Sea Clipper, keep the demountable function with some heavy duty wingnuts so I can cartop if I have to, and keep the pedals in the floor of the cock pit so I can sit down inside on a cold day to get out of the wind if I am sailing alone, but also add a tiller and extension for when I need to hike out in high winds. How is that for a crazy run on sentence? So I would end up with a longer hull, making it a little faster, and longer amas providing more buoyancy so I can step off a dock into the boat with out the ama(and me) sinking. That gives me displacement and seating for maybe 2 and half people. And, when I build a Sea Clipper 20, I will have enough seats for all the butts in the family if I take all my boats out at the same time. We could go marauding around the lake like a pirate fleet!

[Todd Bradshaw]

Re: Lee wants a new trimaran design...

I'd need to know a lot more about the boat to venture a guess about how much sail area would work well. Even so, it would just be a gut feeling. I like to leave those questions to folks who are real boat designers, and they would likely also want to know a lot more about all three hulls before any conclusions could be drawn. On a tri, I think the design and volume of the amas is going to be a critical factor. Stuff or bury one and nothing good usually comes of it.

I really dislike jibs with unstayed masts. It's nearly impossible to get good and consistent jibsail shape when the jib luff's tension and subsequent draft are constantly changing due to changes in mainsail sheet tension. Bad jib shape usually contributes heavily to bad mainsail shape. It's difficult enough to figure out the right luff shape for a Bermuda mainsail on an unstayed mast that has some bend, but it is certainly possible, like on a Laser. Adding a jib with no wires supporting the mast really complicates the situation and lowers the chances that it will work well.

[Lee.007]

Re: Lee wants a new trimaran design...

I really dislike jibs with unstayed masts......Adding a jib with no wires supporting the mast really complicates the situation and lowers the chances that it will work well.

So if you read on my "Newbie needs help" blog, I went out on New Years Day when we had some nice weather and heavy heavy winds. I tried a jib for the first time. I don't have any stays on my mast. I just ran a line from the mast head down to the bow. HORRIBLE experience. The jib shape looked like a balloon or a bad spinnaker. The interaction between the Main and the jib was not cool. Oh, and it didn't help that the winds were a steady 15 miles an hour, gusting to 20+mph. Yeah, I buried the amas a few times, and you are right, nothing good comes from a buried ama. Slows me down, kills my steering and sail setting for my course. If I am not thinking quickly and reacting, I can get capsized really quick. I ended up jumping in the lake and taking all that mess loose from the mast. I do plan on using stays on my next boat.

[Lee.007]

Re: Lee wants a new trimaran design...

Oh, and for the next boat sail area guess, picture a drifter 16 stretched out to 19 feet, amas stretched out proportionately. I haven't figured up the ama dimensions yet. But they are 7 1/2" wide, I will probably increase the width a little when I stretch the length. I am thinking maybe 10" wide, and about 12 to 13 feet long, and set about 5 to 6 feet out from the center line of the main hull, 10 to 12 feet total beam. Any guesses for or suggestions for Sail area?

[Todd Bradshaw]

Re: Lee wants a new trimaran design...

That's still really a question for a boat designer, not a sailmaker. The size and volume of your amas is going to be a serious factor in determining how much heeling force the boat can stand up to, so before designing the rig, you really need to design the hull package that it will sit on. That hull really doesn't thrill me though, whether stretched or not. In a package in that size range you can do so much more. On one end of the spectrum would be something light like some of Gary's outriggers, done as a tri if desired. At the other end would be something roomier (though certainly heavier and more complex) like our old Farrier trimaran, which could seat up to six people comfortably in the open cockpit. The reasonably narrow main hull flared out, well above the water where that part never got wet, and all that cockpit room, plus the wingnets was wonderful for a boat under 20' long.

[Lee.007]

Re: Lee wants a new trimaran design...

Hmmm. Flared hull. I never thought of that. Excellent idea. That's why I am a Soldier and not a Naval Architect. I can see how a narrow hull can be fast, with the flared portion providing a lot of living space. Almost like cheating. We always say, "if you aint cheatin', you and try'in. But if you get caught, you aint' try'in hard enough!"

Does anybody know of a home-buildable design that has the flared hull?

[NeilMB]

Re: Lee wants a new trimaran design...

Does anybody know of a home-buildable design that has the flared hull?

Besides the Seaclipper 20 you mean? Richard Woods’s Strike series from 15-20 feet have the same sort of widened cockpit on a slender hull. So does the W17.

One of the things that I haven’t been able to figure out just from looking at plans is how slender hulls with wooden seats supported on the akas compare to the more complete cockpits of the seaclipper/farrier/strike/w17.

Gary Dierkings picture earlier in the thread seems to illustrate the former, with sideways seating but not a full cockpit.

[Todd Bradshaw]

Re: Lee wants a new trimaran design...

This is a photo of the main hull of a Farrier tri like our boat being restored with the amas and other stuff removed. You can see the flare. It does wonders for cockpit space.

tramp-trimaran-15.jpg

[JimD]

Re: Lee wants a new trimaran design...

And generally speaking, there are good reasons why the main hull of tris have narrow as possible waterline beams. Probably would hurt the performance and comfort to have a flat bottom 18 footer fat enough in the middle for two people to sit side by side.

Edited to add: I see others have mentioned the need for a narrow waterline beam. Somehow I did not see those comments when I posted. As for flared hull plans, most of the small simple day boats have dory style widely flared single chine or a double chine, apart from the Strike. If it were me I would have no problem designing a 'hiking flare' myself, if a more enclosed, sheltered platform to hike onto - in practice the place where you sit and sail from - were what I wanted, keeping the hull as narrow as possible at the waterline, acting as more of a foot well than where you actually sit.

[Lee.007]

Re: Lee wants a new trimaran design...

This is starting to sound like a lot more work than I want. I could design up a flared drifter. But, I aint no Naval Architect, and I learned the hard way from designing my kayak - free boat designing software from the internet aint all its cracked up to be. Especially when I don't know how much rocker is enough or too much, how much volume to give me bouyancy is enough, etc. So I will stick to a design that someone else has already proved will float, and actually sail and tack easily. My kayak with the sailrig tacks like trying to turn an oil tanker around. If I don't give it some paddle, I will almost always end up in irons, no matter how slow or fast I turn the rudder. It will turn fast, but it just won't go through the eye of the wind very easily at all. I don't think I have enough rocker. Anyway, I think I will just build a drifter, maybe stretch it but keep the same beam, add some "wing nets" made out of cedar which could be alternate seating while sailing, and the wife can sit on the wing nets, in front or behind in the hull. I want to do this to get another boat quickly. Oh, and Yes, I still plan on building a Sea Clipper 20.

[Todd Bradshaw]

Re: Lee wants a new trimaran design...

It is not at all unusual for it to take an entire season of sailing to learn to reliably tack a trimaran, but that is one place that a jib helps. You leave it cleated on what will soon be the "wrong" side and let the backwinding jib help to push the bow over onto the new tack. As mentioned before though, a jib really needs shrouds or backstays (or both) to maintain decent shape and keep the luff tight.

[tri-guy]

Re: Lee wants a new trimaran design...

The Seaclipper 20 sounds like a good choice. I'm not crazy about those akas, but as a builder of a Marples CC23 I can highly recommend the quality of the design work and plans for anything John has done.

[JimD]

Re: Lee wants a new trimaran design...

This is starting to sound like a lot more work than I want. I could design up a flared drifter. But, I aint no Naval Architect, and I learned the hard way from designing my kayak - free boat designing software from the internet aint all its cracked up to be. Especially when I don't know how much rocker is enough or too much, how much volume to give me bouyancy is enough, etc. So I will stick to a design that someone else has already proved will float, and actually sail and tack easily. My kayak with the sailrig tacks like trying to turn an oil tanker around. If I don't give it some paddle, I will almost always end up in irons, no matter how slow or fast I turn the rudder. It will turn fast, but it just won't go through the eye of the wind very easily at all. I don't think I have enough rocker. Anyway, I think I will just build a drifter, maybe stretch it but keep the same beam, add some "wing nets" made out of cedar which could be alternate seating while sailing, and the wife can sit on the wing nets, in front or behind in the hull. I want to do this to get another boat quickly. Oh, and Yes, I still plan on building a Sea Clipper 20.

I agree, just build a drifter. for something to park your butt on over the side a simple plank to sit on would do.

[Gary Dierking]

Re: Lee wants a new trimaran design...

What makes trimarans fast. Read the PDF here: https://drive.google.com/file/d/0Bx_...uyBIyGIgxqq9Jw