David Tyler wrote:
Peter Manning wrote:Could one of our experts please give me some advice on positioning the mast on Malliemac.
When I stepped the mast a few months ago it had a forward rake of 2 deg. as designed. However for some reason or other and probably due to the way I made the partners, I find that when the mast is located in the centre at the top of the partners the front edge of the mast touches the bottom front edge of the partners. I can move the foot plate aft thus placing the mast more equally throughout the height of the partners (about 9") but this increased the rake of the mast to just under 6 deg.
I feel I should move the mast so it does not touch the partners but I don't know what impact this would have. My sail is very similar to David Tylers's second sail before he converted to swing wing. It has bendy battens and camber in the lower three panels. The yard is close to vertical when hauled up.
Please can someone offer guidance to help me decide what to do.
Peter,
Assuming that the partners are now all nicely coated and painted, I would leave them alone. Ideally, the hole would be conical and concentric with the mast at its designed rake of 2 degrees, but if it isn't, then you'll have to make a set of wedges that differ in angle around the circumference of the mast - the forward wedge will have to be at quite a steep angle, it seems, with the thickness at its bottom decreasing to zero. But what is the situation on the aft side? If the hole through the partners is such that angle at the forward side is very steep, does the angle at the aft side decrease to such a small amount that the wedge would jam - or does it even go negative, so that the wedge would drop straight through? If that is the case, then you'd have to think again about remaking the hole in the partners.
Your alternative, since you have a bolt-down mast heel, is certainly to think about moving it aft a bit. If you do, of course, you will have to put a thin wedge underneath it to keep it perpendicular to the mast. To decide whether it's a good thing to move it back is another matter, and I have to try to think back and remember how the helm balance was with that shape of sail. If it's anything like it is with my current sail, and I don't see why it shouldn't be, you could use a degree more rake, perhaps a degree and a half, but you certainly don't want six degrees.
Thank you to both David's for your comments and advice. At present the mast sits in the partners with wedges and the hold down ring in place. The front wedges are at a steep angle but not right as they don't touch the mast and partners over their full length which I assume they should do. The aft wedges are still tapered but much less so than the forward ones. They also don't touch the mast and partners along their whole length. There is no negative taper and I expect to be able to remove the existing wedges fairly easily.
I intend to re-make all the wedges whatever else I decide to do.
The hole is conical and built perpendicular to the forward slope of the deck as shown on the building plans. However, the copy of DT's drawing which I think showed the construction of the partners was very feint and I ignored it. I suspect this error may have arisen because I did not follow this drawing or realise it's importance.
I want to move the front edge of the mast away from contact with the bottom front edge of the partners and if I move the foot plate back a little I can achieve this although the mast will not fit concentrically in the cone and therefore each of the new wedges will have to be a different shape.
Moving the footplate back to increase the rake to 3.5 deg seems the best remedy especially as I now have all but two of the bolts removed and these last two are loosened.
I agree I will have to make a thin wedge to sit under the footplate which I shall do.
I read in PJR that the mast rake could be up to 10 deg but I assume from your comments that increasing the rake too much will increase any weatherhelm which would be undesirable.
I wish i had done what David Thatcher did and make a mock up the mast from the foot to just above the deck and build the partners to suit.