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

That's probably a good way to look at it with the 8.5m's success. I wouldn't go so far as requiring a porta potty though, considering my experience with the Class 40 guys finding the most weight effective place to put theirs and never ever using it as a toilet. But some accommodations and protection sounds smart. Maybe a good place to start would be basic Series Mini Transat stuff. Limit length, beam, freeboard of main hull, mast height above water, bowsprit length and most importantly build materials. Everyone loves the prototypes in concept, but the series class has more participation, they're cheaper to build, and hold their value a lot better than protos.

 

But a 20 foot tri or cat, let's be honest; they are too small for family cruising ... and such a design compromise is near useless if you want to have a cruiser/racer craft. Okay for 2 people with maybe a small shelter/cuddy - but that orients it towards a race boat.
6 metre multihulls? - they are just tiny spidery things besides, say, a Mini-Transat 6.5m ... the multi to the mono is such that there is no comparison.
Take a look at the Everglades Challenge designs; the multihulls are geared to race with accommodation being minimal to doesn't exist, (Smyth's solo tri) whereas the monos from 17 to 22 feet carry 2 people in what looks like reasonable comfort, yet still provide excellent performance - thinking of the cat ketches here.
Otherwise you have to go bigger, like the Kiwi 8.5's and the like, if you want both worlds - but they are much larger craft, in all directions, including expense.

 

Certainly from this threads posters, it would seem there is a real split of types, one direction the pure racer pitted against the 20ft cats but with a bit more creature comforts such as a lunch and beer locker ( small Cuddy ) with no expectations to beat the cats.

The other type like the Patterson design where accommodation is everything but windage and wide hull beam will make them a relatively slow bus.

So how can we make a 20 foot Tri better. My belief is that with largish Amas, good central hull form, and a bit of thinking in regards to the rig they will make fun comfort racers for 2 with the option of a 1 +2 nippers for pretty fast and cool fun day sailing.

That small Cuddy will allow the boat to enter races the cats can't enter at a cost of probably half of its big brothers at pace that's not going to hold up racing events.

So ideas then on how to make these potential fun Tri's even more fun.

Here we go then, with its long central hull I think the rig has to be one of the best areas of development. I think we are too focused on main, jib, screecher. What about main, working jib, jib and then assy spinnaker. Ie 3 sail upwind, 3 sail downwind, rig CE is low down with all the benefits of smooth air flow over the relatively small but high aspect ratio sails on a relatively stable platform.

 

if a boat like this is to have a cabin - what is the minimum cabin size that would suffice

 

Team Scarab offerings seem to have a nice blend of features on the cabin end of the spectrum.

Wayne, 3 sail upwind has more potential aero drag and harder trimming.

RE the Patterson....do you have data to support the slow bus comment or is this an assumption?

 

The Patterson design, is it a slow bus, that was an assumption and if someone likes to bring race data foward then I'll continue to assume. I was told once by a very good glider designer, if it doesn't look right then it generally isn't. The Patterson design does look like it has a very wide beam and has a lot of windage, but as always I'm open to persuasion.

I beg to differ on the 3 sail, everything in the books says that a single Uni sail is better than a jib and main and with very skilled sailors I would probably agree. Certainly at my level of sail setting though, setting the jib is a very valuable aid in getting a smooth air flow over the main, this in turn seems to allow the less skilled sailor a much better chance of getting the main sail right. Certainly in my case I feel the boat is much faster over a 2 hour period with a blade jib than without.

I still wonder about the benefit of the lower CE of a 3 sail arrangement as well, it also brings other constructional benefits such as lighter masts and less stress on the stays with better stay angles.

 

Disclaimer: I'm working on another project, and have no skin in this game, but I like the conversation.

Hi Gary, I wasn't suggesting a Mini Transat style multihull, I was simply suggesting, were there to be box rule for a 20' trimaran, you could use some of their very simple parameters to define the box, because it seems to work well in the series class. I guess I didn't make that clear. As for cruising, I agree. The class in my head would be best used as daysailer for camping when not racing. Unlike a mini, 24-48 hours on a 20' trimaran would be fairly extreme for most people.

So, what rule would produce the most active 20' trimaran class, a bunch of Scissors zipping around, something with a cockpit and cuddy cabin or something in between?

Edit: I see that question has been addressed above.

 

Re a 20 foot class, have a look at http://www.boatdesign.net/forums/multihulls/t20-new-development-class-39874-7.html

 

I would agree with Cav, any theoretical benefit from a cutter rig would be lost by sail handling and trimming. The more sails the harder to get them all right.

Even if you had a self tacking inner jib you'd struggle short tacking getting the outer one round the inner forestay. When racing to windward with screechers we usually roll them up as we tack as we've found that is quicker. Destroys the myth that "multihulls only tack if you back the jib"

You'd also have a lot of rope in the cockpit and I assume racing with only 2 on board, you'd both need to know what you were doing!

Having said that, I have occasionally close reached with jib and screecher set, but it isn't often you get a course like that (the RtheI being one)

RW

 

For me the attraction of a trimaran (in this size) is the availability of cheap used beach cats for amas and sail rigging. Since the result is not an all out racer I think more in terms of light cruising. With some sacrifice of creature comfort a small tri is a great cruiser. By that I mean it is great luxury compared to backpacking. Obviously monohulls carry greater weight and volume at this length, but they are slower, induce seasickness, and lack 'floor space'. What I envision in this size is great soft accommodation. A great dodger and tent setup makes all the difference.

 

So am I missing something? I looked at the 8.5 website (and my information is only from that site). I see the class was started 11 years ago. The fleet size seems to vary between 5 and 11 of which at least half are GBE or F boats, ie boats not designed for the class

So what makes it successful? Obviously not numbers of boats built to the rules. It doesn't appear to attract existing boats either (I believe there were 300 GBE's built in NZ)

In comparison the Micro class had 15-20 boats racing for many years

How many boats have actually been built specifically to the rule and then raced in 8.5 events? It seems it may be 4?

Richard Woods

 

Nope. It's probably me just going on what I've heard. Your numbers could be spot on.

 

Richard I think you maybe are looking specifically at the Auckland race results ? its not such a big multihull centre. Gary Baignet will know more and I guess we await his input on that one. Certainly I was under the impression that it was regarded as good racing class and offered differing boats a method of getting together. :?:

 

Or spot off . I wrote the introduction on the website so I suppose I should address this.
Re. The Gbe; Malcolm supposedly sold around 300 sets of plans worldwide. For numbers in NZ maybe a couple of dozen each of glass production and wooden home builds, A number of which have sold overseas.
By my count 9 boats have been specifically designed and built to the rule in Nz. I think maybe 25 or so boats of all types have been measured. One of these has been taken overseas by its owner. Other designs by Tony Grainger and Nathan Stanton have yet to be (and may never be )built. The farrier designed F85 SR. has had one example complted overseas.
It is interesting that when micro multis were very popular in Europe the Gbe was also enjoying its biggest success here.

I don't think it is valid to compare micros with the 8.5 today. micros were successful in Europe where a large population spread over several countries was able to support a number of production multihulls that fitted the class. In NZ a LOT of people sail, but the percentage of them that own and sail multis bigger than a beach cat has always been relatively small. The only racer/cruiser type multi built in any numbers was the Gbe. Which appears to have met the market requirement for boats in that size range.

In a similar fashion at the moment I think there are enough purpose built 8.5s and GBEs that have been modified and updated, in Auckland, to satisfy the needs of those with the time and coin to race them seriously. The 8.5 rule, while not resulting in large numbers (by international standards) of new boats being built, has resulted in a number GBEs being resurrected and updated and gives people who want to build to their own ideas an envelope to aim for so they can race against boats that are not too dissimilar. In that sense and given the number of people here who might actually have means and inclination own one of them probably wouldn't reach 3 figures, I think the rule has been successful in the NZ context.

Its a long weekend here and it's time to go sailing.

 

Thank you for the update and clarification

Enjoy your sailing

RW