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Old 28-10-2008, 11:45   #1
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Question Filling screw holes in mast.

I'm rebuilding/repainting my mast and there are a number of holes which will no longer be needed. Most of these are tapped #10 holes from a try-sail track which will no longer work due to a new mainsail track. Once filled, the mast will be primed and awlgriped. Any opinions on:

  1. Fill holes with epoxy
  2. Fill holes with threaded aluminum rod and sand flat.
  3. Have holes welded closed and grind flat.
#1 is easiest but I'm leaning toward number 2 which shouldn't be too time consuming.
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Old 28-10-2008, 12:44   #2
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Why not countersink slightly and Loctite some oval head screws in there? They're not unattractive and would be available if you needed to attach something later.
I wouldn't weld anything for fear it would make the metal brittle.
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Old 28-10-2008, 15:34   #3
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if you are not going to use them again they should really be welded. this is so there will be no stress risers/fatigue/cracking from them. but this only works right if there is good penetration in the weld.
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Old 28-10-2008, 15:45   #4
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Originally Posted by mike d. View Post
if you are not going to use them again they should really be welded. this is so there will be no stress risers/fatigue/cracking from them. but this only works right if there is good penetration in the weld.
How does he (practically) relieve the heat-induced stress of welding aluminum?
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Old 28-10-2008, 15:49   #5
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Stick a pop rivet in the pukas and tell anyone who asks, and they won't, they are for some super secret sailing equipment. Really, with pop rivets in the holes, they will look like they have some use and will literally disappear from your notice. You could flare the holes and fill them but that's a lot of work for no real return. Sticking some threaded material into the holes probably won't work as the paint will crack around them eventually.

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Old 28-10-2008, 15:57   #6
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I removed a furling boom and was left with many small holes. I used stainless rivets for every hole. As Peter O said they are virtually invisible and if anything look like they are there for a reason.
I would not weld on the mast if you can avoid it.
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Old 28-10-2008, 16:23   #7
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I would think that anything stainless is just begging for future paint failure.
I agree with Gord that welding would cause more problems than it would solve.
aluminum rivets would work, but how is that better than threaded aluminum rod which would be invisible?
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Old 28-10-2008, 16:27   #8
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If it's a long string of closely knit trysail track holes it could distort the mast from welding. Welding aluminum actually softens the metal... takes the heat treat away and returns it to soft condition. Under stress the cracking usually occurs at the heat affected zone between the soft and hard metal. IF the holes are away from other mast openings or high stress areas it's probably not an issue. The pop rivets may cause corrosion on your new paint job. I guess I would opt for filler. maybe a little flaring of the holes with a counter sink... but not much.
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Old 28-10-2008, 18:23   #9
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Plan and simple "Rivets" it's a nice finish!
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Old 28-10-2008, 18:59   #10
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If using rivets and wanting a flush finish, I'd use countersunk rivets, and use aluminum instead of SS to lessen the chance of corrosion with the aluminum mast. Dipping each rivet in 3M 4200 would help also as the alloy of the rivet would be different than that of the mast.

The rivets below would be a perfect fit for a #10 screw hole.
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Old 28-10-2008, 19:19   #11
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You guys have more experiance then I do...But I just redid my mast last winter...Im sure it was the first time ever for my boat...all my screws were SS a couple had to be hit with a hand impact to break lose but none anywhere on the masts or booms ( Ketch ) were so badly corroded that they needed re taped..we used lanacote and 3M 101 to re-bed everything and everything is stainless...personally I dont see the big deal every one makes it out to be

Personally Id go with installing the stainless screws beaded correctly and call it good...I agree with others that any filling will flex and crack anyway...I would not weld them either for reasons also mentioned...I have welded enough aluminum to know there is a time and place for it and mid span on a mast is not it.

PS: How come I can not see the picture posted above ?
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Old 28-10-2008, 19:26   #12
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Can you see this one:

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Old 28-10-2008, 19:30   #13
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Roger that...thanks
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Old 28-10-2008, 23:29   #14
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As a Machinist and someone who has worked with alum. for the better part of the past 40 years I would state that there would only be a couple reasons, at all, to mess with the old holes.

1) For cosmetic reasons, and then I'd go with the rivets mentioned above in ajman's post.

2) To keep the rain or saltwater out. By putting anything in the holes doesn't strengthen it at all. And welding, absolutely not with that many holes!!!!!

Why anyone would suggest SS rivets, I can't find the reasoning behind that? SS would be for strength and on aluminum the mast would give out first damaging the mast. With SS rivets, on thin alum., one should use back-up washers.

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Old 29-10-2008, 04:07   #15
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I just did this when repainting both booms. The prevailing practice in my neighborhood (W coast of Florida) is to bevel out the hole somewhat and then apply a mix of epoxy and low-density filler (microballoons, etc.), then sand fair. It's dirt cheap, offers no corrosion issues, very easy to execute for any skill level.

Beveling out the hole gives a 'land' the epoxy/filler mix can hang onto. I'd stay away from MarineTex as it's too hard and therefore harder to sand fair without dimpling the surrounding aluminum surface. To minimize clean up/fairing, I placed small strips of blue tape on all 4 sides of each hole. After kicking, pulling off the tape reveals a tiny fairing job to be completed.

Welding? Goodness, no. Rivets? That was my interim fix until I could repaint, when I wanted an easy but invisible fix. Stainless fastener heads in an aluminum spar? No thank you.

Jack
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