I think this has been covered here in another post, as I believe this helps absorb some of the load on the deck from the halyard blocks attached to the deck around the mast.

I thought its use was to keep the deck from rising due the hull being squeezed from the sides while sailing. As it is noticed that the shrouds on the lee side are loose. This is due to the fact that the hull is squeezed from the sides and it causes the deck to rise.

Ben,
Both Steve and Haro are correct. The turnbuckle should be hand-tightened when the hull is at rest, in the water, with no tension on any of the halyards. The C36 has a keel-stepped mast (duh!), and when the halyards are tightened, they pull the deck upwards due to the blocks at the partners. Not good. The turnbuckle keeps the deck in place, relative to the mast. The turnbuckle (and two U-bolts) are actually very important pieces of rigging, and should not be forgotten when stepping the mast.

You are lucky you didn't ask this question on April 1st.

[QUOTE=LCBrandt;12548]You are lucky you didn't ask this question on April 1st.[/QUOTE]
Absolutely. Otherwise, some wise guy would have 'splained that the brace actually [I]suspends[/I] the mast from the deck so that it doesn't punch a hole through the hull and cause your boat to sink...
But of course its not April 1st so I won't say that!

My boat had been run with the turnbuckle too loose. This did allow the deck to rise and that allowed the port bulkhead to rotate inboard about half an inch at the top. Besides compromising the strength of the boat this has brought the trim on the inboard edge of the bulkhead into contact with the mast and it squeaks horribly.

My surveyor said next time I haul out I should set the boat down on her keel on the hard and loosen everything including chainplates, allow the hull to settle out, knock the bulkhead back into place, then refasten the chainplates, then tighten the rig including the turnbuckle.

We don't have a turnbuckle. When were they introduced?

Rob,
As far as I know, they have always been on the C36. But.....because the mast is not installed until it reaches the dealership (another duh!), the eye strap has to be slid into the groove in the mast as the mast is being stepped, and then bolted in place. Not all dealers are created equal. With the excitement of a 600+ lb mast hanging from a crane, it's easy to forget the eye strap. When that happens, the rigger often pockets the eye strap and turnbuckle, and nobody is the wiser. One year that happened to me, and I insisted that the yard get the crane out again, and lift the mast so I could slide the eye strap into the groove.

Something like Channel Islander, not as bad as Tom's: When they restepped our mast back in '03 after getting new standing rigging and our ProFurl LCI32, they just hand tightened the turnbuckle.

I only have wooden mast wedges and when we started sailing there were these horrible screeching sounds coming from the partners.

I traced it down to that turnbuckle and started tightening it until the sounds disappeared. Except for the BIG work of replacing the entire standing rigging, YOU as the skipper, are the best person to be able to adjust things. Most yards simply won't take your boat out sailing after their work is done, now, will they? :)

Thanks Tom & Stu - it seems our turning blocks are fixed to the mast itself, so exert no upward pull on the cabin top. :confused:

Do you think that's likely to be the case?

I believe they have my turnbuckle to tight. We the boat was surveyed and on the hard all the doors opened and closed without a hitch. Now, the Vberth door and the door between the Vberth and bathroom won't open inthe case of the bathroom or close for the cabin door. Can i just loosen the turnbuckle till the doors work or will this effect the standing rigging? What else am I potentially missing?