|Topic Review (Newest First)|
|10-16-2007 06:20 PM|
|10-16-2007 05:33 PM|
Yes; tenuki there are MANY ways to trim the boat in different wind conditions, and some boats may go faster or point higher with a bubble in the main. I am going to point something out on the SF Sailing.com trim guide:
I did not read all of the links you posted; but the one on the Shields class boat also is showing some backwind of the main mostly so that the boat can point higher (pulling the jib in to where it is almost parallel with the main). I think what they are trying to show is that if you don't do this you won't point high enough. It looks like the main is huge for that boat and a bit of power loss due to backwinding is less critical than pointing.
A -slight- bubble or lightness at the luff is optimal in moderate winds. If it is more than 12" wide or so I think you are giving up some power. It's ALL about having a balanced helm; the rudder is a giant brake pedal if it is turned sideways to the water flow. I was just trying to point out that triming the sails to a correct shape is first and then adjusting things so the weather helm is minimized will give you the best overall performance.
|10-16-2007 04:03 PM|
one last post on this topic. lol.
I was racing as railmeat with blt2ski last weekend in FWB and when we started beating on the last leg I couldn't believe how far he had the mainsheet traveler moved to windward in high winds. what?!?! was he crazy? But I didn't know his boat so I kept my mouth shut, but it bothered me. Until.... we gained all our way on the competition in that leg ( we had lost a fair bit on the first let, a downwind run struggling with an unfamiliar asym ) (came in fifth although I think we were close to last rounding the second mark). His boat loved it, he was outpointing everybody. If I had been trimming things we would have gone slower and pointed lower. His boat is totally different than mine and he knows his boat.
|10-16-2007 03:50 PM|
This got me to thinking why these 'wrong' things bother some people so much. Tell tales being trimmed deliberately to break half the time, deliberate backwinding, etc. I think they have this idea of a particular 'shape' being 'right' and aren't listening to the boat with their other senses and thinking about why. The 'visual/shape' school of sail trim is wrong in so many cases. Read through any of the North Sail's one design class trim hints and they are rife with 'strange' settings. Look at this one... North Sails J24 guide It has things like the following..
"so in light air we slide the draft back by sailing with 1/2-inch scallops between each luff hank. These wrinkles look pretty ugly, but they allow the draft to move aft to 44 percent, the proper position for light air. As the breeze builds, halyard tension should be slowly tightened until the wrinkles disappear in 12 knots true and up (usually when whitecaps just appear on the water). "
That would drive some people crazy, but it's faster...
"In up to 13 knots, the top batten points as much as seven degrees to windward of parallel with the boom, and the telltale on the top batten is stalled as much as 50 percent of the time- but the boat doesn't seem to slow down: it just points higher!"
again, some of the people I know would have apocalyptic fits.
I think this summarized it nicely.
"The Key to successful J/24 racing is not the memorization of this information, but the understanding of it. Why is mast rake so important? Why does a particular deck layout work, and will it work for your crew? Why do we sail with wrinkles in the luff of the Genoa in light air? You can only go so far by copying others without understanding why the technique is fast."
I'm as inexperienced and clueless as the next guy, but I can tell you this with assurance, the knotmeter is the final arbiter (+ pointing angle and the tiller). and only two things will get you fast, 1) trying to understanding why instead of following 'rules' or 'visual ideals', and 2) experimentation, sometimes crazy experimentation to find _your_ boat's particular sweet spots.
Sorry about the multiple posts, I just have this argument with a friend of mine all the time and I'm taking my frustration out on you guys. lol.
|10-16-2007 02:14 PM|
|tenuki||This one, a North Sails - Sheilds class trim guide even has a picture of a backwinded main and states 'no bubble? more jib sheet!'.|
|10-16-2007 01:21 PM|
J29 class website trim tips.
Moore 24 class tuning guide
SF Sailing racing trim guide
North Sail's Main/Genoa interaction guide
If you still don't believe me (
|10-16-2007 06:59 AM|
Originally Posted by tenuki View Post
|10-14-2007 12:02 AM|
As has been mentioned it is important to know your boat, as every boat performs differently. My favorite activity is playing with crazy sail trim ideas and the knotmeter. That is how I found my boat likes the main with a bit of backwind above 10 knots. It freaks one of my friends out, who trims totally on sail shape. Despite having lost the bet before, he still insists it's trimmed wrong, and then loses the bet once again. lol. the backwind looks like someone is standing at the mast gently punching the luff. It drives him crazy, but after 10 knots it makes at least a .2 knot difference.
Know _your_ boat. Experiment every time you are out.
btw Jim, when I bought my boat the mast had a bend to port, that really screwed up the sailing characteristics. I had to replace the standing rigging right anyway so I didn't worry about rig tune then, but man oh man, the difference after the rigger got done with it. It was like a totally different boat, amazing what difference rig tune makes.
(rigger = Chris Tutmark, highly recommend him. He is well loved by the J24 racers here in Seattle, so he knows my size boat well)
|10-12-2007 12:45 PM|
My point wasn't so much the boom angle change. That was a gross error. My point was more the two "little" changes I made (the leach of the genny and the mild tensioning of the mainsails foot) each resulting in a fairly significant change in boat speed--easily seen on the knotmeter.
If we weren't racing, I would've eased the genoa's leach and messed with its traveler and sheet to see if I couldn't duplicate the improvement there, instead. I suspect, however, that trimming that leach line probably resulted in closing the leach and powering the genny up a bit more efficiently than I could've achieved by other means.
|10-12-2007 12:17 PM|
Are you SURE that your sail is blown; or are you just having difficulty getting it sheeted down tight (not enough purchase) for close-hauled pointing? When you trim the main in it pulls both laterally and vertically. The vertical pull is what gets the sail flat but it takes a huge amount of force to crank it down. If you can't trim it in while going up wind you will need to luff the sails and then sheet it in or sheet it down tight while tacking. The boom should be parallel to the centerline of the boat if possible; of course the draft of the sail would be controlled by use of both the mainsheet and traveler.
If our main is not trimmed properly, there is too much lee helm and our pointing ability is bad (at windspeeds ~15kts and above). Once the main is properly trimmed we make hull speed with a much more balanced helm, but the boat will heel to about 25-30 deg. Sails are both relatively new.
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