mast head jumper arrangements

[Tim Stewart]

Can anyone tell me how to tune a mast head 'jumper stay' arrangement standing rigging, and where in the sequence of rig tuning do you tension the 'jumper stays' (first / last etc).

Usually the struts are angled forward so I would have thought that if you tensioned the 'jumper stay' wires, then you would put negitive bend into the top of the mast.

On a Westerly 33 Ketch mizzen mast, there doesen't seem to be a backstay counteracting the induced negative bend of the 'jumper stays'.

Can anybody advice with the tuning on this yacht.

Thanks

Tim

[Brion Toss]

Hello,
I usually tune the jumpers first if the mast is on the ground, and hope that the negative bend that results will convert to an appropriate positive bend after the rig is stepped.
If the rig is already in the boat, jumpers also need to be tuned first, after slacking everything else. They are quite a lot of work either way, usually requiring an extra trip or two aloft, but there you are.
With no backstay to oppose them, I would think there would at least be runners. I'm not familiar with the boat; would you post pictures?
Fair leads,
Brion Toss

[csilva]

Originally Posted by Brion Toss

Hello,
I usually tune the jumpers first if the mast is on the ground, and hope that the negative bend that results will convert to an appropriate positive bend after the rig is stepped.
If the rig is already in the boat, jumpers also need to be tuned first, after slacking everything else. They are quite a lot of work either way, usually requiring an extra trip or two aloft, but there you are.
With no backstay to oppose them, I would think there would at least be runners. I'm not familiar with the boat; would you post pictures?
Fair leads,
Brion Toss

Since the negative bend will depend on the tension you put on the jumpers, is there any way to determine how much tension should be given before stepping the masT'

Thanks,

[Brian Duff]

I have always tuned jumpers to limit mast bend, such that with a straight mast there is often no load on the jumpers, or light pre tension.

The setting on them depends on the shape of the sail you are controlling - but maybe I over complicate the matter?


Brion is right, there must be backstays of some sort, or very swept 'cap' shrouds, to keep the whole kit from tumbling forward....