Stay measurements

[seawolf]

In preperation of re-rigging my 1962 Columbia 29, I went up to the masthead with my tape and had a friend take measurements below. If I can trust his measurements to be accurate, this is what we came up with pin at masthead and spreader tangs to pin at chainplates.
Port upper: 34' 1 and 3/4"
Stbd uppper 34" 2 and 3/4"

Port Lower 18' 6 and 5/8"
Sbtd Lower 18' 7 and 7/8"

It seems to me if the port upper and the port lower are both approximately an inch shorter, ther would have to be a bit of an S shape in the top part of the mast if it were perfectly centered on the boat.
Should I worry about this, if the mast seems straight enough? Or get another pair of glasses.
Any ideas welcome.
Bob

[seawolf]

I forgot to mention, the rig seems to be in tune and visually the mast looks straight.
Bob

[Ian McColgin]

It would be interesting to have the straight line mast head to chainplate measurements to know if the truck is truely centered amidships. You can get this by bobbing a halyard assuming a calm day and assuming that your sensitivity to the pressure you put on the halyard is good or that you hang the lead from your lead line on the halyard end to give a consistent halyard stretch.

But a little asymetry in the boat's construction is also not impossible.

G'luck

Ian

[seawolf]

Can this be done with a halyard sheave that is off center to the masthead.
I have two masthead sheaves, and they are at each side of center.
Thanks

[Brian Duff]

its ok if the sheaves are off center a bit (such as double sheaves). To eliminate the possiblity of pulling the halyard harder on one side than the other, we tie the tail of the halyard to the shackle, and attach a steel measuring tape, then hoist to masthead and set up tight tight. The steel wont stretch, so your measures will be really accurate.

check that the mast step/ partners is centered between the rails of the boat, and that the chainplates are equdistant from the mast. if that is the case, split the difference of the measurements of the existing rigging port and starboard, then make the new rigging at the new numbers.

This is 'how its done'

[seawolf]

That sounds good. I will give it a try and see what I come up with.
Dividing the difference is good advise.
Just one more question regarding measurements.
Since I will be using the old wire as a template, can I omit any working elasticity value of the new wire and just make sure my new turnbuckles are at mid adjustment when making my final measurement against the old wire?
I believe any constructional stretch for the lengths mentioned above would not be a worry.
7/32" 1x19 SS longest length, backstay at 38' 1 3/4"
Thanks again to all for your kind advse.
Bob