When those that are in the no build a boat to a one design rule like a solo what dimensions do they tweak to the max or min to optimise performance.

Are all boats different or  is it the same basic tweaks that are always made?

Ian

Don't some of classes have a rule which states that if you build using the tolerances to opermise speed then the boat will not measure?

There was a chap at a contender open meeting early this year who wanted to build a contender that would carry weight better. Not sure how that worked out though.

generally people try to minimse waterline beam and wetted surface. whilst keeping the lines nice and straight.

lots of compromises and things to weigh up. and you can never have the best hull for every condiotion

The Fireball (designer Peter Milne) was a fairly relaxed design in the sixties to allow for some home building tolerance.  However in the late eighties (I beleive) the Aussies realised that there was a LOT of room for manouvre in the forward sections and designed a wider-bow boat called Missile which whupped the ass of anything else in the windy stuff at sea in waves.  I think that this was then refined by Delange in a boat called Crocodile JD which then formed the mould of the all-conquering Winder design that has been dominant for the last 10 years.

Basically by exploiting the bow section tolerance the boat was made much more bouyant and far less prone to going through waves rather than over them.  It's not that noticable until you park an old (narrow) and new (wide) bow boat next to each other where it becomes very clear.  However although fantastic at sea, the wide boats are technically slower on inland waters and feel a bit "slappy" in chop.  But you have SO much more confidence in them when the chips are down in a blow!

Any real Fireball experts please feel free to correct me on the order the boats were produced above!

Well I can think of 2 classes where 'near the limit' dimensions are relevant not because they are faster alround but the difference in performance is significant because the plane at a lower speed.

When the Hornet class started having glass or cold-mouded wooden boats they tweaked the shape at the bow to increase volume and flatten it a bit and this maked it plane earlier - this was the Revolution (or Revvo) design.

There was also an Albacore builder (Kingsfield) who build some boats which were either very close to the tolerance or even outside it but there were so many build before they measured them that they got a special dispensation from the assoc to race. These boats also plane earlier and are very difficult to get hold of as the owners mostly keep hold of them!

Back in the late 70s Scorpions were moving towards less rocker both in the keel and in the chines.  I suspect this made them inclined to plane earlier and possibly faster, however they seemed less able to carry wieght.  I've a feeling they where slightly less vee'd at the transom.

Recently I sailed the 59er this like the 29er and the 49er has a very narrow waterline under the mast and fine entry.  These boats move from non-planing to planing with hardly any transition and when planing slice along very cleanly.  They don't seem to be going as fast as they are.  Yet they aren't too unstable because they are quite flat towards the stern.

I'm really impressed with the hulls but feel they don't tolerate heel very well - but thats correct for proper racing boat design.  If you look at older designs the maximum waterline width is further forward but they can be sailed on their ear.

I conclude that if you have an old design boat with some tolerances it should be built with fine front sections, as little rocker as possible and flat around the stern.  The only thing to watch is that you are not heavy and you are very mobile in the fore and aft direction, you keep the boat flat and you don't sail in light winds.

I sail a 4000 which is not very flat at the stern and not very stabile.  I wonder if the designer (Phil Morrison) reads this forum and if now, in retrospect would make the rear a little flatter?  I would have thought so.

JimC, I sure you're right about that.  Just a bit more important to keep the weight well forward in the light stuff.

I notice the 800 is quite capable of being beaten boat for boat by the 4000 when it gets really light.  They have flatter sterns but unfortunately they also collect water in the cockpit.  However having sailed one I know its the small centreboard that really kills it.  The 4000 has quite a big board for its size.

Mind you this is all academic since both boats are dogs at these low wind speeds and really the best place to be is in the bar.

I really don't want to knock Cherubs but when I sailed on it was really poor in the lulls, slow and lots of leeway.  However a little puff got the crew out on the wire and it was fantastic, naturally it was faster but the real impression it made with me was that suddenly it pointed very well.

It was a similar problem to sailing an asymmetric downwind in gusty conditions.  If you get a gust you can sail deep and fast but in the lulls you might have to put a couple of extra gybes in.  The Cherub was like that upwind, sometime you were struggling to lay the mark and then you get a gust and you overstand!

Definitely optimised for wind.

There was also an Albacore builder (Kingsfield) who build some boats which were either very close to the tolerance or even outside it but there were so many build before they measured them that they got a special dispensation from the assoc to race. These boats also plane earlier and are very difficult to get hold of as the owners mostly keep hold of them!

Matt Allot of the kingsfield albacores didnt measure and had to be modified to measure, they are fast planing boats but still not as quick allround as the old woof design which is allot better all round and still the bench mark for the rest of the albacore fleet here and ovver the pond.kings fields are only hard to get hold of because there wasnt many made.  They do still come up for sale, but there is always very very few albacores available forsale.

I also seem to remeber when i owned a solo, the association inspecting speed boats through complaint's from other solo sailers about how the distributed the weight of there frp boats, this was proved incorrect but it makes you wonder, how far these builders push to the limits.