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Old 27-09-2007, 05:14   #16
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Another option for the leave on boom cover would be awning rail. It accepts a welted finish and would attach to the boom with screws or rivets. If you put the fasteners up they wouldnt show. Theres a lot to mainsail trim that hasnt been discussed. I was amazed when reading the book The Best of SAIL Trim at the intricate methods of shaping the luff and the adjustment of the camber and cord for different wind conditions. If your mainsail builder is available he (they)would give the best advice on how going loose footed would affect this particular sail.
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Old 27-09-2007, 07:40   #17
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Another good tip...maybe I better take my main into my sailmaker and ask before I decide to commit to the on-boom sail cover...

Thanks again everyone!
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Old 27-09-2007, 10:21   #18
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Yes a shelf foot, like a loose foot, is good for light air upwind, light to moderate air reaching, and most downwind work. Of course that needs to be qualified further by the type of boat, sea state, skill of the helmsperson, etc. (I was trying to keep my previous post short and simple).
The point is that an attached mainsail foot with no shelf adversely affects the sail shape. Ease the outhaul and the cord depth along the foot stays at 0%. Going from 0% to the desired depth (in the realm of 10% to 15%) cord depth makes for a very inefficient sail. A shelf foot and a loose foot both solve this, allowing for a smooth and consistent cord depth.
Forsailbyowner describes attaching a preventer (not a vang) to the boom in big seas. The loose foot had nothing to do with the boom failure. A preventer should be attached close to where the clew is attached; or when reefed, where the leech reef is at the boom.
Let me stress again, the attached mid foot of a mainsail does not offset or cancel downward forces exerted mid boom (by a preventer or vang or mid boom sheeting). In a former life, I was a sailmaker/designer for 10 years. I have extensive experience testing sailcloth (most notably for the A3, winner of the 1992 Americas Cup) and making numerous sails for extreme conditions (various around the world races/cruises). To help illuminate this point further, look at the orientation of yarns in 3DL or other “string sails”. Yarns run clew to head, clew to tack, etc. but nothing significant (substrate material only) is oriented mid foot perpendicular to the boom. The cloth is relatively weak and stretchy. Furthermore, if we go back to the point that you want the chord depth along the foot to be somewhat consistent and smooth going up the sail (although depth percentage does increase), the sail depth along the foot means no upward force offsetting the mid boom downward forces, boom deflection, etc.
Lastly, after batten pocket tears, the most common mainsail tears I saw were mid sail between the luff and leech reef points. If the reef diamonds (many different names for them) are mistakenly tied to the boom, the line or sail tie can load up and the sail rips (or short of that distorts the sailcloth). Again this shows that even a little loading perpendicular to the boom, on the sailcloth bias, causes problems for the sail, while doing for the forces exerted on the boom.
Hopefully this helps clarify.
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Old 27-09-2007, 10:57   #19
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Geez...what great comments...
svTOTEM, I agree, the shelf on my main has about 6-7" of depth, and under normal outhaul tension that area of the sail has ZERO downward tension to the boom.

I called the sailmaker here in Dallas (I know a sailmaker in inland TX of all places?..don't go there) that made my main a little while ago and he agreed that loose footing it is fine, and even preferred to more easily adjust the outhaul.

He said when he does this he typically reinforces the clew a little, and adds a heavier duty car just ahead of the clew..all points mentioned in the various posts here.

He thought rough cost would be (without seeing it for other repairs) would be $150, so that's not bad.
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Old 27-09-2007, 11:06   #20
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Your sailmaker is spot on. Price seems fine. It'll be interesting to hear back on what you think after it's done.
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Old 27-09-2007, 12:19   #21
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Totem,

Not to argue the point but the following is kind of what I was indicating. If a boat was designed with the mainsheet attached to the end of the boom and the boom was made lightly then any force hauling down near the center without any counteracting force might be an issue. There must be some counter force from the foot of the main. I can feel it when I try to pull down on it with my hands. It might not be a great deal but there is some.

The below is from Moonchaser:
"I made a big mistake one time of putting a vang on a hunter with in mast furling that we were chartering, We were sailing downwind in large rolling seas and the helm was difficult. I put a vang (?preventer?)about 3/4 of the way back towards the outhaul and did okay, but when the next watch took over, after a few hard gybes the boom bent in a most unappealing fashion. Learned my lesson from now Ill attach it back by the outhaul on loose footed boats."

Kind Regards,
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Old 27-09-2007, 13:09   #22
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JohnL,
I hear what you’re saying, but maintain the sail does not provide any significant force to offset the downward forces mentioned. The boom bent because it was shock loaded. I've experience one and seen many broken booms that had attached mainsail foot. The overloaded vang in a big seaway, poorly placed preventer under crash jib loading, poor design, manufacturing defects, poor maintenance, bad setup of reef blocks on the boom, etc. cause boom failures.
Whether I convince you or not, please consider the point with respect to the rest of the boom sail control system and the occasional extreme loading. When metal thing break under load, bad things can happen fast. I was helping to tune up a Whitbread 60 off Southampton England some years back. The boat we were sparing against suddenly stopped and flurry of activity started. Turns out the spin sheet trimmer had the sheet wrapped around his wrist. The turning block broke and instantly took off his hand. Fortunately, do to quick action they did reattach it.
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Old 27-09-2007, 13:12   #23
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Go loose footed!

You may want one of those cords sewn in the foot so that you can put a little tension on it to keep it from fluttering.
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Old 28-09-2007, 00:28   #24
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Quote:
Originally Posted by jzk View Post
Go loose footed!

You may want one of those cords sewn in the foot so that you can put a little tension on it to keep it from fluttering.
Agreed on a cunningham in the foot and the roach, and it does act a bit like a shelf and helps with catching down wind. Adjusted just right it's like half a spinnaker. I attempt to adjust it so the air spills over into the genoa, wing-in-wing.................._/)
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Old 28-09-2007, 00:38   #25
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BTW to avoid accidental jibs, buy a boom brake. One of the best investments I ever made. I counted 4 times, the last time out, it saved me from a potential ERROR The heck with preventers!

An accidental jib CAN take down a whole rig under the right conditions. Let alone the bodily harm it can do.
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Old 28-09-2007, 00:43   #26
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Aloha Totem,
Thanks for sharing your experiences and knowledge. I'll builde my boom tougher than most. I'll take your word for the sail having insignificant effect to counter act the mid boom sheeting but it kind of defies my logic.
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Old 28-09-2007, 00:58   #27
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Hi Guys,
The benefits of a track / car at boom end can be replicated with a strong webbing strap covered both sides with velcro.
Wound round the boom but inside the clew cringle, it serves the same purpose allowing the sail to to adjusted fore and aft but reducing lateral movement.
Suggest it might be an easier solution?
JOHN
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Old 29-09-2007, 09:30   #28
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JohnL - Cheers!

delmarry - I have no direct experience with a boom brake, but the idea of it makes a lot of sense. Reducing the extreme shock loads of heavy air dead downwind situations is a good thing.

swagman - I've sailed on a few boats that had the mainsail clew setup you describe. It seemed work work nicely. Of course you do have to keep an eye on chafe. I also like the idea of attaching the upper mainsheet block to the boom with webbing. With this you can have the block setup 12" or more below the boom. This reduces the mainsheet length (12" x 5 part purchase = 5' shorter mainsheet). Depending on the hight of your boom/block you do have to mind you head a little more.
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Old 01-10-2007, 16:33   #29
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FYI

Got some pict's this weekend in the pouring rain. Soooo, here is how mine is set up.
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Old 02-10-2007, 05:08   #30
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H delmarrey,

Thanks much for the pictures! I see you have a block sewn into the clew, very smart...eliminates the need for a block attached to the clew, thus reduces hardware flopping around that can possibly get caught up when reducing load on the outhaul.

And to everyone that offered comments, thanks!!

I think I have all the information I need to go discuss with my sail loft...

I will admit I'm a little nervous to go cutting into my mainsail to cut the shelf off, but after hearing all your comments, I'm armed with everything I need to know.

Thanks again!!
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