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Old 23-03-2010, 07:38   #1
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Boom Vang Attachment Advice?

Hello all! Looking for opinions/advice about the mast attachment point of a block and tackle type vang. My research came up with three different ways to do it; 1) a tang slid into the sail track and secured with screws or welded, 2) a reinforced bail just like on the boom, or 3) a deck mounted padeye just behind the mast. Functionally I like the bail on the mast, but dont like the added holes at the base. The track tang seems the easiest, but not sure if it's the strongest. On my boat, a deck mounted padeye would be a pain to properly install a backing plate for, so I'm kinda leaning away from that one. Is there an alternate that I missed? What do you find is the best method? Thanx!
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Old 24-03-2010, 15:24   #2
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Holes in the mast isn't a problem as long as you put something in them, like a fastener. The mast is in compression.

cheers,
Nick.
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Old 24-03-2010, 18:31   #3
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Holes in the mast isn't a problem as long as you put something in them, like a fastener. The mast is in compression.

cheers,
Nick.
Very true, if I go that route I plan to install bearing plates too. I just hate the thought of finding a crack between the pivot bolt hole to one of the other holes already there for the wiring/antenna exits, which are pretty close to the same plane as where the pivot bolt would go.........
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Old 24-03-2010, 20:41   #4
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G'Day Second wind,

Is the mast keel or deck stepped? Changes some of the loading factors at the deck level...

Jim
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Old 24-03-2010, 20:47   #5
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G'Day Second wind,

Is the mast keel or deck stepped? Changes some of the loading factors at the deck level...

Jim
Deck stepped mast, 4.75 x 8 section, oval shaped. I've been trying to find the exact spar maker, but haven't had luck there yet. I think Irwin used their own spar design, but not sure on that point.
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Old 24-03-2010, 20:58   #6
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2nd wind,

With a deck stepped mast there is little bending force just above the step. The primary loads, as Nick said, are compressive. I wouldn't worry too much about adding the bail there, especially if you attach it with several smaller screws on each side rather than one larger through bolt. I believe that this will spread the loads out over a larger area in the mast section, and reduce the chances of cracks developing. It would be a good idea to set things up so that there is no torque applied to the bail...just a straight pull from the vang tackle.

Cheers,

Jim and Ann s/v Insatiable II lying Church Point, NSW, Oz
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Old 24-03-2010, 21:13   #7
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A bail is a better idea than a fitting on the mast track. Why do I know? I used a u-bolt thru the mast track on my previous boat, a 1971 Irwin 32 (aft cockpit). The mast split open on a hard reach. Chesapeake Rigging in Annapolis, who backed up and welded the split, said the mast probably split at the original manufacturing weld.
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Old 24-03-2010, 21:18   #8
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Thanks Guys!

Appreciate the info very much! My thoughts were a bail with a 3/8 thru bolt / bearing plates though, as I thought it would keep the loads more in line with the pull when the lower block moved around the mast on different points of sail, would a fixed bail be better?
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Old 24-03-2010, 21:25   #9
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A bail is a better idea than a fitting on the mast track. Why do I know? I used a u-bolt thru the mast track on my previous boat, a 1971 Irwin 32 (aft cockpit). The mast split open on a hard reach. Chesapeake Rigging in Annapolis, who backed up and welded the split, said the mast probably split at the original manufacturing weld.
Ouch! It seemed to me also that the tang might not be as strong unless it was welded in place, plus it would have more leverage for possible damage on a hard reach / ddw than if the lower block could travel around the mast some. Might not be an issue for some mast sections, not sure how the Irwin masts compare to others for strength though.............
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Old 24-03-2010, 21:38   #10
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OK, I just remembered the new arrangement on my Irwin 32. Chesapeake Rigging also made a tadpole shaped plate, with an eye in the 'tail', the tail being bent out of plane, so that the plate could be between the mast base and the deck step (and bolted down with the step). The eye was the new vang attachment point, with no stress on the mast.

You'd have to pay for the mast to be picked up, and have to length the standing rigging, but this arrangement is overkill on strength.
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Old 24-03-2010, 21:51   #11
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OK, I just remembered the new arrangement on my Irwin 32. Chesapeake Rigging also made a tadpole shaped plate, with an eye in the 'tail', the tail being bent out of plane, so that the plate could be between the mast base and the deck step (and bolted down with the step). The eye was the new vang attachment point, with no stress on the mast.

You'd have to pay for the mast to be picked up, and have to length the standing rigging, but this arrangement is overkill on strength.
Wish I could do that, I'd absolutely love to have a step plate organizer, but on the 32.5 center cockpit the mast step is in a recess on the forward cabin slope which doesn't allow room around the back of the mast for a plate.
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Old 24-03-2010, 23:24   #12
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Okay, I'm doing this out of memory so it would be wise to check it but the rule is something like to keep a distance 3 times the biggest hole diameter between two holes. So if you have two 3/8" holes close together, the minimum spacing between them must be 9/8" better known as 1-1/8". Between 1" and 3/8" holes there should be a distance of 3" etc.

I have another idea: if you use a block & tackle vang, you can also put two pad eyes on the sides of the mast and splice a Spectra loop around the mast and through the pad eyes. If you use a single braid like Amsteel Blue from Samson, the splice is done in a couple of minutes.

cheers,
Nick.
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Old 25-03-2010, 03:37   #13
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I have another idea: if you use a block & tackle vang, you can also put two pad eyes on the sides of the mast and splice a Spectra loop around the mast and through the pad eyes. If you use a single braid like Amsteel Blue from Samson, the splice is done in a couple of minutes.

cheers,
Nick.
Good one, Nick! I think that I like that plan best

Jim
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Old 25-03-2010, 05:21   #14
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Nick beat me too it. If your your load was perpendicular to the attachment point such as a main sheet, you would not even need the pad-eyes.
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Old 25-03-2010, 07:41   #15
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Nick, that's an awesome idea! I was just about to order some 3/16 Amsteel Blue to redo the lifelines, I guess I'll hafta add a few feet of 3/8 for the bail. Thanx again!
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