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Old 04-10-2008, 21:15   #1
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Boom Vang

Is there any set measurement that applies to the installation of a Boom Vang? What is the proper angle of the measurement of installation between the mast fitting and the boom attachment supposed to be?
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Old 04-10-2008, 21:21   #2
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30 degrees from the boom.

Go here.......... Boom Vang
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Old 04-10-2008, 21:22   #3
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30 to 45 degrees is recommended.

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Old 04-10-2008, 21:53   #4
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Originally Posted by Ex-Calif View Post
30 to 45 degrees is recommended.

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Just a note:
The greater the angle the stronger the mast attachment needs to be. More upward force with a greater angle and less leverage to the boom.
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Old 06-10-2008, 00:40   #5
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Here's a Word document I found on the web that does the trig for you.
The parts I tried to do myself I got the same answers they did. There is a part that most cruisers aren't worried about that I'm not sure they got correct. I'm not sure that all their conclusions about mast bend are correct. They say that as you move the attachment point on the boom closer to the mast, the vang becomes less effective, tension in the line increases, (all correct to this point), and therefore mast bend increases. Well they show earlier that the horizontal load component is unchanging as you move the attachment point on the boom. If the amount that the boom is pushing forward on the mast is not changing, and the lever arm (boom meeting mast to vang mast attachment distance) doesn't change, it seems to me that amount the mast bends doesn't change.

http://www.imcansw.org/Martin%20Grose%20vang1.doc

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Old 06-10-2008, 08:31   #6
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OK, now here is the question. Is the 30-45 degrees the measurement of the angle from the attachment point on the boom to the mast angle or is it the angle from the mast to the attachment point on the boom? Is this measurement from the boom down to the base of the mast or up from the base of the mast to the attachment point on the boom?
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Old 06-10-2008, 09:22   #7
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OK, now here is the question. Is the 30-45 degrees the measurement of the angle from the attachment point on the boom to the mast angle or is it the angle from the mast to the attachment point on the boom? Is this measurement from the boom down to the base of the mast or up from the base of the mast to the attachment point on the boom?

It's the angle at the boom. This was answered by Delmarrey in the title of the #2 post and in the link he posted.

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Old 06-10-2008, 10:10   #8
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Thanks. I just wanted to make sure before I start drilling the new fitting. Better to ask than say "oops" after getting it done.
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Old 06-10-2008, 12:30   #9
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Consider the force and breakage issues with a vang for cruising. A good squall with it down tight and watch for schrapnel! Broken boom possible too. In a gust without it, the sail lifts to release the power. When you are reefing and forget to release the vang while in the turmoil of reefing in gusty wind (and you will) you will risk sail or boom damage as well as possible injury. Great as a preventer for reaching in light air though if you make it attachable to your toe rail... You probably know all this already, just seems like a Vang on a Liberty 458 is a little like headers on a school bus.... do you need that extra 2%? No slight intended though. Cruised with a couple who had one of those beautiful boats. Very nice and high quality.
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Old 06-10-2008, 18:45   #10
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It should look something like this................. The dark line being 45º. That's the boom brake.
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