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Mast rake
Posted: Mon Apr 26, 2004 6:36 pm
by GARY WEEKLY

While washing my boat yesterday i happened to notice my mast was not setting down all the way on the deck plate it,s tilted slightly back.
Can some kind sailor check theres and see if it is leaning back and not setting flush on the deck plate? I have CDI furling and don,t know if this is off or what?

Posted: Mon Apr 26, 2004 7:48 pm
by Dimitri-2000X-Tampa
My 26X is like that too, apparently by design to induce some weather helm (boat rounding up in heavy wind/heel) for safety reasons. I have my turnbuckle cranked in all the way to reduce it some, but if you want to get the mast nearer to vertical, I've read of people here who have had to shorten the forestay.
I'm curious of those who have shortened the forestay...is the boat clearly faster? Can you back that up with any racing of stock 26X'es?
Posted: Tue Apr 27, 2004 11:12 am
by dclark
Dimitri-2000X-Tampa wrote:My 26X is like that too, apparently by design to induce some weather helm (boat rounding up in heavy wind/heel) for safety reasons. I have my turnbuckle cranked in all the way to reduce it some, but if you want to get the mast nearer to vertical, I've read of people here who have had to shorten the forestay.
I'm curious of those who have shortened the forestay...is the boat clearly faster? Can you back that up with any racing of stock 26X'es?
I've wondered the same thing and I've got my turnbuckle as tight as it will go (and the backstay in the last hole). I was all ready to reduce the rake some, but then I heard a few things like guest said. The last thing I want to do is something that will make it point worse! I wasn't going to cut the cable, I was going to make a new hole in the mast about 2" above the old one and move the tangs up. I guess I could try it and go back if I don't like it. Either way I'm planning to split the backstay and I'll need to do that first.
Posted: Tue Apr 27, 2004 12:45 pm
by craiglaforce
The backstay has nothing to do with mast rake. If you want the mast to tip forward for less rake you generally loosen the upper shrouds and then tighten the forestay. They form a triangular pyramid at approx the same elevation. The backstay is to induce bend.
The boat is fastest and points best when it has a little bit of weather helm.
If it rounds up into the 15-20 mph wind gusts out of control then there is too much rake and everything will improve if the rig is brought into better balance.
I'm pretty sure 6 inches of rake is way excessive, but it depends on what sails you have. a large Genoa vs a working jib makes a significant difference in sailplan center of effort.
I have about 2 inches of rake with a working jib and the steering does not pull my arm very much even when heeling with 20 mph+ wind speeds.
You just want enough weather helm so that if you fell overboard, the boat would gradually end up pointed into the wind. This also supposedly also gives you a little upwind lift with the underwater foils.
Posted: Tue Apr 27, 2004 1:18 pm
by Mark Prouty
How do you measure rake?
Posted: Tue Apr 27, 2004 2:29 pm
by craiglaforce
I just stand off to the side about 40 feet away and eyeball it.
I suppose you could hang a weight from the main layard or something, but then the boat is moving around if in the water or the boat is not level maybe if on the trailer. Really the main objective is to get the almost balanced feel on the helm with just a little pull to weather in gusts.
The fancy racer types measure steering wheel movement from dead center and put a mark on it at about 5 degree rudder deflection and go sailing. if they need more than 5 degrees of helm, they tend to make changes to correct it, either on the water sail trim changes or back at the dock rigging changes.
I bought a videotape a several years ago called "Trim for Speed" by the guys at North Sails and it was pretty instructive to see all the crap they do to their boat to make it go a little faster. Hydrualic jacks on the backstay and running rigging with so much load on it the boat seems to be screaming in pain every time they make an adjustment. Even they seemed to still be learning and this is their life's work!
Posted: Tue Apr 27, 2004 3:04 pm
by Mark Prouty
I have a piece of plywood from the previous owner with a slight angle in it. He said that it was for mast angle. He must have used it to measure rake.

Posted: Tue Apr 27, 2004 7:14 pm
by Dimitri-2000X-Tampa
craiglaforce wrote:You just want enough weather helm so that if you fell overboard, the boat would gradually end up pointed into the wind.
My boat would have the autopilot on and would just keep on trucking to Cancun. I'll bet two charged batteries would run that autopilot for days.
Seriously though, I have been out in 20-30 knot conditions this spring and the boat did not round up. But I was also pretty heavily reefed as the family doesn't like a lot of heel.