Getting in tune
Posted: Tue Nov 02, 2010 3:06 pm
When I was on the coast, I was not pleased with Windward's performance to, um, windward. While there I eased the forestay turnbuckle a couple of turns and noticed a significant difference. I still wasn't pointing the way I wanted to, though. In addition, the new 130 has a slightly flat cut, so it needed some more headstay sag to provide good power in mild conditions, and when slugging into chop.
When I raised the mast last weekend I decided to increase mast rake by easing the headstay tension, effectively lengthening it. Dangling a wrench from the main halyard, I think I ended up with about 5" of rake, measured to where the gooseneck is mounted on the mast. This was probably 1/2" longer on the forestay than I'd been using, and I think equates to a little less than 1 degree of rake.
I then centered the mast laterally using the cap shrouds and left the lowers loose but roughly even. Using a Loos "B" gauge, I adjusted the caps to about 27 on the gauge, roughly 15% of the 3/16" shroud's breaking strength. I had to adjust the spreader angle once to get them to bisect the shroud's angle.
I tensioned the forward lowers to get about an inch of forward prebend at the spreaders, and tweaked enough to remove a slight bow to starboard. I tensioned the aft lowers until they provided some slight resistance, then brought the forward lowers to about 22 on the Loos gauge. Still had about an inch of prebend.
I adjusted the backstay until it read about 0 on the Loos, quite a bit looser than I'd had it in the past. I then cranked down the backstay adjuster. There's no scale for 5/32 wire on the B gauge, but max tension was around 25 on the gauge. At that point I eased, recranked, then adjusted the aft lowers to limit the mast bend to between 2 and 2.5". I eased the backstay adjuster again, then had to retension the caps from 25 to 27. Also retensioned the forward lowers a bit.
Got her rigged, then went sailing. The day's great 15-20 kt breeze had of course dropped to 0 - 10, sometimes a bit higher, gusting maybe 15, and shifty. Notice I said SHIFTY, not with two Ts.
She was like a different boat, the one I remembered somewhere in the past before a couple of rounds of mast and rigging repair. Despite funky breeze, I immediately noticed that she was pointing better, with more authority, and tacking through around 90 degrees. The helm was much improved, too -- I could tie it off and she tracked like a slot car. By playing the backstay adjuster I found I could really tune both the power of the jib and the fullness of the main. I was comfortably making 4.8 - 5.7 kt upwind, and the apparent wind was certainly no higher than 10 - 15 (need to get that anemometer hooked up).
My big concern was that I'd be rounding up frequently with the additional rake. There wasn't enough breeze to be a decent test, but I had no such problem in the 14-18 kt (true) gusts. When things were on the blustery side I yanked the adjuster down, tensioned the vang, cunningham and outhaul some and dropped the traveler slightly. Also eased the jib tweaker, effectively moving the lead aft. She felt wonderful!
I'm looking forward to bigger breezes and lengthier testing (for science, of course -- someone has to do these things), but my conclusion is that even if you think you have your boat dialed in, it's well worth the time to play with the tuning a bit. Once you have settings that work, absolutely be sure the write them down, along with any notes you make during sea trials. I'd be pleased with the results so far even if they cost money. The fact that they were free is gravy.
When I raised the mast last weekend I decided to increase mast rake by easing the headstay tension, effectively lengthening it. Dangling a wrench from the main halyard, I think I ended up with about 5" of rake, measured to where the gooseneck is mounted on the mast. This was probably 1/2" longer on the forestay than I'd been using, and I think equates to a little less than 1 degree of rake.
I then centered the mast laterally using the cap shrouds and left the lowers loose but roughly even. Using a Loos "B" gauge, I adjusted the caps to about 27 on the gauge, roughly 15% of the 3/16" shroud's breaking strength. I had to adjust the spreader angle once to get them to bisect the shroud's angle.
I tensioned the forward lowers to get about an inch of forward prebend at the spreaders, and tweaked enough to remove a slight bow to starboard. I tensioned the aft lowers until they provided some slight resistance, then brought the forward lowers to about 22 on the Loos gauge. Still had about an inch of prebend.
I adjusted the backstay until it read about 0 on the Loos, quite a bit looser than I'd had it in the past. I then cranked down the backstay adjuster. There's no scale for 5/32 wire on the B gauge, but max tension was around 25 on the gauge. At that point I eased, recranked, then adjusted the aft lowers to limit the mast bend to between 2 and 2.5". I eased the backstay adjuster again, then had to retension the caps from 25 to 27. Also retensioned the forward lowers a bit.
Got her rigged, then went sailing. The day's great 15-20 kt breeze had of course dropped to 0 - 10, sometimes a bit higher, gusting maybe 15, and shifty. Notice I said SHIFTY, not with two Ts.
She was like a different boat, the one I remembered somewhere in the past before a couple of rounds of mast and rigging repair. Despite funky breeze, I immediately noticed that she was pointing better, with more authority, and tacking through around 90 degrees. The helm was much improved, too -- I could tie it off and she tracked like a slot car. By playing the backstay adjuster I found I could really tune both the power of the jib and the fullness of the main. I was comfortably making 4.8 - 5.7 kt upwind, and the apparent wind was certainly no higher than 10 - 15 (need to get that anemometer hooked up).
My big concern was that I'd be rounding up frequently with the additional rake. There wasn't enough breeze to be a decent test, but I had no such problem in the 14-18 kt (true) gusts. When things were on the blustery side I yanked the adjuster down, tensioned the vang, cunningham and outhaul some and dropped the traveler slightly. Also eased the jib tweaker, effectively moving the lead aft. She felt wonderful!
I'm looking forward to bigger breezes and lengthier testing (for science, of course -- someone has to do these things), but my conclusion is that even if you think you have your boat dialed in, it's well worth the time to play with the tuning a bit. Once you have settings that work, absolutely be sure the write them down, along with any notes you make during sea trials. I'd be pleased with the results so far even if they cost money. The fact that they were free is gravy.