Help with space-frame 12

[alk]

I was wondering if anybody could help shed some light on the space-frame arrangement on 3219 - a baggy trouser.






I don't understand the function (or name!) of the highlighted tensioner cables. They attach at the mast step, and terminate at the space frame, next to the shrouds. Are they simply to add tension to the rig? If so - could anyone give me any advice as to how they are actually tensioned? The 'cigar' shaped thingy has a hole in it, whilst two threaded bolts attach to either side. Thanks

[johnk]

As I understand it, the wire from the bottom of the shrouds to the mast foot is to transfer the vertical load in the shroud to the bottom of the mast so that the mast compression balances the shroud tension. The space frame deals with the horizontal forces. I would expect that (hidden in the forward buoyancy tank) there is also a wire from the forestay foot to the mast foot to do a similar job. The end result is that most of the rigging loads do not go through the hull shell.

The cigar shaped "thingy" with threaded bolts is a turnbuckle. The threaded bolts have opposite handed threads. Rotating the barrel (using a rod through the hole in the middle of the barrel) while not rotating the bolts will lengthen or shorten the wire. You need the lock nuts to stop the turnbuckle coming undone.

When the jib is hoisted and the shrouds are tensioned you want the load on the hull shell to be small. I am not sure exactly how this is measured.

[alk]

Thanks for your help, makes a lot of sense now. No (obvious) wire from forestay foot to mast foot when I was patching up the forward buoyancy tank, but I shall investigate!

[angus]

Hi I have 3231 Mr Bill which has a similar arrangement, if not the exact same. Yes the wire are basically there to stop the mast going through the floor of the hull. They should be tight. There is not one going forwards.
When I got Mr. Bill the wires were slack and a crack had occurred under the mast. The wires have been tightened up and crack repaired and there has been no further trouble. The wires are easily tightened up by rotating the cigar shaped bottle screw I believe it is called.
I don't know how tight they should be I tightened them up till they made a decent twang, which the original owner of Mr Bill said was about right. I am not sure if it would be possible to overtighten them without going to considerable effort.

[alk]

Cheers Angus, that's a lot of help.