Tensioning frac rig with swept back spreaders

[mikehoyt]

HI. Have Hinterhoeller Niagara 26
I purchased a Loos tension guage and it stated for 3/16 wire to tension shrouds to 600lbs.

On my boat I thought this a bit excessive but tried. Seems to now move well upwind in windy conditions and waves. Seems slower than before downwind esp in lighter winds.

Am planning to ease the outer shrouds 1/2 turn on turnbuckles.

Comments?

[Bob Pingel]

Tension depend on lots of variables.

Talking tensions in general, you want to tension longer wires more than shorter ones, because long wires stretch more than short ones -- more specifically, as a starting point, on shorter wires you want 10-12% break strength, and on longer ones you want 12-15%. 3/16" has a BSD of 4400#, so if you cranked everything to 600# you likely have some OK, and some too tight, but maybe not.

The whole idea is to keep the mast upright and in column under various conditions. You have a complex set of members in tension and compression, and you can't tune that system with a simple "crank it XX pounds" statement.

You really need Brion's tuning video, it will get you going, and then you'll likely need to post some specific questions about your rig.

Bob

[mikehoyt]

Thanks Bob

I realize the rig cannot be cranked XX pounds from a book. My plan was to tune while sailing and use the tension meter to obtain the number that worked best in each vcase as a starting poiint for each season. My crew decided to start with the 600 lbs that was stated in the directions that came with the guage.

My real question was more about how this would affect the windward and downwind performance. The boat is fractionally rigged, has one set of outer shrouds that pass thru swept back spreaders and one set of inner shrouds. The mast is deck stepped.

Is it normal for a highly tensioned rig to perform well upwind in windy conditions and waves but be slower downwind due to this tensioning - esp in light airs? ... or is this just my imagination?

Thanks

Mike

[mgpedersen]

Originally Posted by mikehoyt

My real question was more about how this would affect the windward and downwind performance. The boat is fractionally rigged, has one set of outer shrouds that pass thru swept back spreaders and one set of inner shrouds. The mast is deck stepped.

Is it normal for a highly tensioned rig to perform well upwind in windy conditions and waves but be slower downwind due to this tensioning - esp in light airs? ... or is this just my imagination?

Thanks

Mike

I think generally that's true. When I used to race J/24's with similar rigs, we adjusted the shroud tension all the time, even between races. Looser tension in the light stuff, more in the heavy. And yes, I also think the higher tension is slower downwind. We generally tried to slack off the backstay as much as possible since you aren't supposed to adjust the standing rigging while racing. It might not be the tension per se that causes the slows, but the rake of the mast. If you can get the top of the mast further forward, I think you'll be faster.

Matt

[Brion Toss]

Hello,
I believe you are seeing two things at work here: too much overall tension for downwind/light air work; and improper relative tension, with all wires at the same tension, regardless of the length, or the actual relative load.
The first issue is about fore-and-aft mast shape, and it is easy enough to address, usually just a matter or slacking or tightening the backstay and/or runners. The second issue is a matter of tuning, and it can address the much more complex problems of lateral mast shape.
Fair leads,
Brion Toss