mast placement

[matt connolly]

Hello all,

Im looking to re-rig my tangaroa mk4 with a crab claw,ketch set up. Can any body tell me where to place the main mast? If any of the crab claw guru's are up for it,any other dimensions would be great,boom and spar length etc. Cheers.

[Galway Bay]

Matt I love this kind of experimentation. Beware I am not paying for any of it !!

Really this is a very big question. It seems to mean very different things to different people. It seems to cover a multitude of shapes from long thin near horizontal ethnic sails almost to low aspect leg-of-mutton.

Some parameters are needed so I considered the following -

Sail area = 400 [same as now].  Sail sizes 250+ 150. Sail shape triangular with approx. equal yard / boom  meeting at between 60 and 45 deg. at base of mast. Yard close to vertical when hoisted.

 First off I sketched a main of 250 mounted on beam #1 and immediately it is obvious that it extends all the way back 17 / 18 ft so the only place you can put a mizzen is on beam # 4.

So you seem to have no choice [ except in a major re build ] main mast is on beam #1 and mizzen on beam #4. The challenge really then is to produce a balanced rig working with these constraints. I did a quick sketch with equal sided yards  / booms meeting at 60 deg.  A quick balance calculation showed too much sail aft which would result in heavy weather helm. However adding a jib forward of 80 sq ft. balanced this pretty good and looks good too.

Fooling around with sketch #2 I added some height to the rig by making the yards 15% longer than the booms and meeting at 45 which gave better clearance for tacking the main. I kept the Jib.  This produced quite a good looking and balanced rig with stability comparable to the JWD version. It also looks very like the "Tama Moana" but that is nobody's fault.

I will try to post a sketch when I am less busy.

Be warned this is a paper boat / rig and comments from sailors with experience should be given due weight.

[matt connolly]

Thanks Galway,I honestly don't have a clue about how to balance a rig so this is valuable information. I have only researched the few wharrams I can find on line,and Hans klarr's ontong java and they are all quite different as far as crab claws go I guess and there isn't much technical data. I can get hold of a laminated oregan mast at a good price which is currently about 35 ft long,so I'm thinking I'll cut it down,although I'm not sure whether to have the forward spar meet the top of the mast as in say wakatiatea,or have it extend past,like a tama. It'll be sail dimensions and balance that may dictate some of that.. As far as other materials go,I do have access to much big species of bamboo so am hoping to utilize that in the rig as it's pretty much free! Thanks again,look forwards to your drawings.