el cheapo IRC racer

[JLP]

hi all, this is my first thread on this forum, so let me introduce myself: i work in the marine industry (carbon masts), and i (try to) design sailboats as a hobby. my newest project is designing a competitive IRC racer with the following design brief:
-length around 30'
-cheap
-amateur built where possible, i am considering a plywood chined hull

i have look at succesful IRC boats (JPK960 here in France, Ker 32 in the UK) and made up the following preliminary specs:
-LOA around 9m
-BOA = 3 to 3.2m
-IRC measured displacement = around 2500kg (yeah, heavy, i know)
-sailing displacement = around 3000kg
-upwind sail area = around 55m2

the rest is still uncertain, like keel type, number of rudders, etc.

any thoughts/ideas/comments ?

[yokebutt]

Jlp,

Have a look at Van der Stadts Black Soo hull design from the mid-sixties, don't know how they rate under IRC though. I'm not sold on solid plywood hulls, consider thin plywood or glass skins over balsa-core instead, it wouldn't cost that much more.

For the keel I'd go with a welded sheet-metal blade and a cast lead bulb, maybe not super-optimum, but you can pour some of the lead in the bottom of the blade to reduce the wetted surface.

Finally, for the rudder I'd find a suitable one from a production boat and modify it to fit, I don't think you'll need more than one on a ten foot wide boat.

Yoke.

[JLP]

thanks for the info. I had a look at "Black Soo" and it certainly looks like a boat straight out of the sixties ! i couldn't find the displacement, but one article mentioned "ULDB" and with a beam of 6'8'', it is not the same type of boat.

concerning the keel, your comment confirms my initial feeling, but I think the IRC rule penalises keel bulbs. apparently the best rating/performance compromise is a fin keel built in two parts, the bottom one being lead. I guess this would be a good case for trial certificates.

concerning the rudder(s), I guess a 10' beam would be the limit when you start looking at double rudders on a 30' yacht.

any more comments ?