Diamond wire tension :: Catamaran Sailboats at TheBeachcats.com

Diamond wire tension

rpiper138

Rank: Mate

Registered: Jul 17, 2006

Last visit: Apr 13, 2010

Posts: 194
Posted: Apr 09, 2009 - 02:17 PM

I have been researching diamond wire and spreader setup for over a year and am still a little baffled. There is a lot of information about setting up a boat for skipper and crew, but very little for uni setups. Does anyone have any insight about spreader rake and diamond tension for a carbon sparred uni (Nacra 5.5) with average weight skipper (180 lbs). The newest setup info that I have (Nacra 5.8) goes into detail, but combined crew weights are obviously higher than having just one fat guy on the wire.

I appears that I need less tension and/or more spreader rake to depower the rig. Is this correct?
MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: Apr 06, 2024

Posts: 7088
Posted: Apr 09, 2009 - 04:03 PM

Let me preface this with... I know nothing about carbon/uni rigs... but in general....

the rake (and diamond tension to a degree) is more about creating a curve in the mast (pre-bend) to conform with the curve cut in your luff... you want it close to matched with minimal downhaul...

If matched.. by inducing heavy downhaul you will spill off air and depower when needed.

This effect will not slow you down from 30knots to 10 knots.. it is a micro-adjustment.

Of course you want/need tension in your diamonds (as well) to counter twist... sidebend... and screaming reaches...

You could do a search on catsailor.com's forum as this has been covered many times in different forums.

edited by: andrewscott, Apr 09, 2009 - 04:05 PM
rpiper138

Rank: Mate

Registered: Jul 17, 2006

Last visit: Apr 13, 2010

Posts: 194
Posted: Apr 10, 2009 - 04:04 PM

I'll see if I can find any new ideas Andrew. I'm not really looking for a lot of pre-bend, just need to get a general idea of how stiff the rig should be (both side to side and fore-aft). I think that heavier crews can run stiffer setups as they don't require the mast to bend and remove power from the rig.

Last time I was out we had 20+ knots and I was looking for anything that would depower the sail. I increased downhaul, dropped the traveler down 10 to 15 inches, took the mast rotation back to about 40 degrees. The mast was raked way back and I still had trouble keeping the boat upright.