Small Tri's under 20', any mention of foils is banned..

There was a gathering of plans and ideas and much discussion on introducing the Micro-multihull here in Auckland (I sent you a copy of the publication, Richard, since you introduced the idea in MI - seems a long time ago). These were 25-26 foot multis and the display of designs at Richmond Yacht Club by established and have-a-go Kiwi designers was varied and interesting (there were even a couple of proas).
We had the altered (cuddy added) Tennant Demon Tricycle parked outside (see photograph). And that boat was 23x16 foot and looked very modern and impressive. And that is about as small a trimaran for two people you can go, imho - so a 20 foot version would be very tight, really a single hander - or if it had interior room, would be fat, ugly and slow.
The Micro class never got going here but the Tennant GBEs (as Greg pointed out) became healthy in numbers (meaning by Auckland standards).
What I'm saying is go longer and lighter but keep the rig lower, like your 20 foot design; well, maybe a little taller. A longer hull is not going to cost much more than a fat, shorter one and the performance difference between the two types ... is large.

 

oooohh Gary, it sounds sooo.....never mind I'm out for the night.....keep it up kiwis...

 

Under 20 really seems like solo cruiser territory unless aka tents are used. The main hull then gets to carry stores and the windage is kept down for sailing.

 

Plans for the Scarab 650 are $100 until the 1st March.

http://www.teamscarab.com.au/index.html

 

That would be a easier build than the Patterson and give you the double bunk.

 

Wow! those are some impressive trimarans! They have a good bit of space for such a small, fast boat. I like the beach-cat rigs they basically put on them. Cheap, easy to come by and plenty of power.

I especially like the Scarab 18 and the Scarab 650.

 

Cavalier
What are you thinking would be easier?

 

The Stitch and glue panel construction of the Scarab in ply would be a easier build versus the strip planking of the Patterson. Strip planking as such isn't hard but it has a lot more glue joints, fairing and filling needed. All those things add up to more epoxy, work and weight. On the harder to build scale I think a glued lapstrake version of the Scarab would look great, save a few ounces and cut down on spray.

 

Gary is right in his post about the length issue, there is really no reason to get to get hung up on a couple feet unless you have storage constraints and are building for a existing garage etc....

 

The Patterson 21 is a very neat and clever design, (this image copied from Doug's posting on the other thread) - but it is at the lowest length limit for a reasonably fast yet small trimaran with some accommodation. Makes the Tennant 23 look very mean by comparison. But the Patterson main hull looks very buoyant for its length, even noting the stepped cross section with narrower WL ... and therefore it is going to bounce in waves. What is its L/B ratio? I'm guessing around 6-7 to 1. Could be wrong. Compare that with the skinny Demon Tricycle - and guess which one goes through the water with less bounce and fuss. I stick to my earlier longer hull preference: 20 feet is too short and even the P21 is ... 21 feet.
PS: Did a little more hunting, see main hull; I take back main hull beam ratios, the P21 is finer than my earlier incorrect guessing.

 

Just going by this one photo

Is there a bunk in the aft cabin? If so that would imply the tiller was at least 6ft long. Quite excessive on a 21ft boat (any boat actually) So making sharp turns and tacking must be challenging, that's a lot of helm movement, too much for some keen racing sailors

When racing a F24/27 the crew go the full distance between the beams. Right forward coming out of a tack to raise the transom, to right aft when sailing fast offwind

At this size cedar strip will be heavy. But a double chine hull has a lot of glass joints to make and the second chine panel is very narrow so of limited benefit

Richard Woods

 

The Patterson bow bulb would increase the prismatic coefficient and speed potential. I wonder if the shape could be pulled off with the Farrier female half mold set up for foam.

It would be fun to get a bunch of these boats together for a round the buoys comparison like the old One of a Kind regattas.

I do like the functional aspect of your windscreen Richard, makes a difference in this part of the world.

 

P21

Cav, where did you see a bow bulb?

 

Bulb is too strong a word but it does have a fuller almost chin feature if the posted lines are accurate.

 

You can see the bows flare out at and under the waterline while above they get finer, nice for cutting through the waves.