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Old 21-01-2012, 10:55   #1
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Epoxy or Polyester Question

I need to take care of a soft deck core under the bow pulpit mounting flanges. I will be cutting the deck and core using a hole saw, then refilling the hole and touching up with a little paint before re-mounting the pulpit.
1. Epoxy or Polyester?
2. Should I use chopped glass or something else as a filler?
3. Can I fill the hole completely in one shot, or should I layer it in a few steps?
Thanks for any advice.
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Old 21-01-2012, 11:03   #2
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Re: Epoxy or Polyester question

It doesn't matter, IMO which you use to fill the hole. But in reglassing to the deck, if what is there now is polyester, your good to go. But if you don't know then epoxy is your best choice. Epoxy will adhere to anything but some other fiberglass resins are not compatible. Epoxy is also stronger. Chuck
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Old 21-01-2012, 11:06   #3
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Re: Epoxy or Polyester question

Definitely epoxy for its strength, predictability and ease of use. It would not hurt to put some glass fibers in there although it would not increase the strength all that much. The rigidity and strength will come from the epoxy surrounding and bonding to the existing fiberglass
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Old 21-01-2012, 11:30   #4
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Re: Epoxy or Polyester Question

For these sorts of small jobs, I prefer epoxy. If anything because it is easier to dispense.

If this areas is going to be under stress as it is a pulpit base, I would definitely use chopped fiber AND silica thickener. The fiber will help resist fracturing from the stress.

Also, dont skimp any the backing plate for the flanges. Helps distribute the load.
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Old 21-01-2012, 11:36   #5
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Re: Epoxy or Polyester Question

Epoxy it is...but...can I fill the holes in one shot?
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Old 21-01-2012, 11:44   #6
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Re: Epoxy or Polyester Question

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Epoxy it is...but...can I fill the holes in one shot?
How big of a hole (thickness and diameter) are we talking? I would say up to an inch thick, 2-3 inches diameter can be done in one shot. Use the slow hardener.

Also, first prime the pepared hole/surface with unthickened epoxy, especially the surfaces of the good core, then fill for best results.
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Old 21-01-2012, 11:44   #7
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Re: Epoxy or Polyester Question

Depends on how big the hole is. If you are layering cloth, mat, roving then it is usually best not to do more than 5 layers at a time. Using chopped mat and filler you should be able to do the whole thing in one shot and then to fair it before painting once it is hardened.
kind regards,
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Old 21-01-2012, 11:45   #8
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Re: Epoxy or Polyester Question

Epoxy bonds better! And that's what you want for repair jobs. It just takes longer to cure and it has to be covered from UV's eventually.

If you use a marine ply for the core you may be able to get it all in one shot. BUT epoxy shrinks when it cures so I wouldn't advise it for such a small area.
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Old 21-01-2012, 11:48   #9
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Re: Epoxy or Polyester Question

You say this is for the pulpit. If you are coming at it from the top, I would not cut a hole bigger than the pad for the pulpit. Cutting a bigger hole will compromise the support. Even if there is laminate opposite the core.

Edit: Otherwise you will need to feather in some glass fabric over the top as SkiprJohn says.
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Old 21-01-2012, 12:12   #10
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Re: Epoxy or Polyester Question

Yes I will be coming from the top. The holes will be about 3/4" deep and about 2 1/2" dia. Basically the size of the pulpit footprint. I was thinking of cutting the core back about 1/2" all around.
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Old 21-01-2012, 12:18   #11
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Re: Epoxy or Polyester Question

Also you'll want to scarf back the top so to lay in layers for a stronger joint.


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Old 21-01-2012, 12:27   #12
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Re: Epoxy or Polyester Question

I would consider a more proffesional repair here. The reason your core is wet and rotten there is because the bow pulpit gets constantly abused and has enough lever arm to really apply a lot of pressure to the flange/pad, causing the bedding to fail. The manufacterer should have done a solid block-out in way of these pads, ie solid glass in way of the thru-bolts instead of core. All deck hardware should be done this way, but many manufacterers don't do it, although it's much more common in newer boats. If you just hole saw the top skin off and fill it with thickened epoxy, as some have recommended, you will end up with a failure of the repair at the seam between the epoxy and the original outer skin, because there is no load transference. You will be thru bolting through a big chunk of brittle epoxy filler which is only attached to the bottom skin over any area. I would moisture meter it to determine the extent of water penetration for sure, remove the pulpit so it's out of the way, remove the upper skin over the area of moisture penetration (almost certain to be larger than a holesaw's worth), remove the wet core, replace the core with either solid glass flat stock or coosa board, then back grind the top skin and laminate a nice fiberglass repair to match. If you don't glass the outer skin it WILL fail. A flat stock plate is best for this, it will make a repair that's overstrong, which is what you want if you are going to thrubolt your pulpit to it. If you bump a dock or other boat with your pulpit and it's bolted to the boat by a big chunk of epoxy, it's gonna break right off. Not to mention the constant abuse it will get in normal use. Not a good place to half-ass a repair. Nowhere is, really, IMHO. Oh, and never fill anything an inch thick in one pass with epoxy, the exotherm will cause all kinds of problems, even with slow hardener. It could crack, and any air bubbles in it will suddenly expand to many times their original size because of the heat.
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Old 21-01-2012, 12:47   #13
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Re: Epoxy or Polyester Question

Quote:
Originally Posted by minaret View Post
I would consider a more proffesional repair here. The reason your core is wet and rotten there is because the bow pulpit gets constantly abused and has enough lever arm to really apply a lot of pressure to the flange/pad, causing the bedding to fail. The manufacterer should have done a solid block-out in way of these pads, ie solid glass in way of the thru-bolts instead of core. All deck hardware should be done this way, but many manufacterers don't do it, although it's much more common in newer boats. If you just hole saw the top skin off and fill it with thickened epoxy, as some have recommended, you will end up with a failure of the repair at the seam between the epoxy and the original outer skin, because there is no load transference. You will be thru bolting through a big chunk of brittle epoxy filler which is only attached to the bottom skin over any area. I would moisture meter it to determine the extent of water penetration for sure, remove the pulpit so it's out of the way, remove the upper skin over the area of moisture penetration (almost certain to be larger than a holesaw's worth), remove the wet core, replace the core with either solid glass flat stock or coosa board, then back grind the top skin and laminate a nice fiberglass repair to match. If you don't glass the outer skin it WILL fail. A flat stock plate is best for this, it will make a repair that's overstrong, which is what you want if you are going to thrubolt your pulpit to it. If you bump a dock or other boat with your pulpit and it's bolted to the boat by a big chunk of epoxy, it's gonna break right off. Not to mention the constant abuse it will get in normal use. Not a good place to half-ass a repair. Nowhere is, really, IMHO. Oh, and never fill anything an inch thick in one pass with epoxy, the exotherm will cause all kinds of problems, even with slow hardener. It could crack, and any air bubbles in it will suddenly expand to many times their original size because of the heat.
I agree totally, you may be making it worse than just leaving the wet core in there. No way to get at it from the bottom? although harder, I would think if you can get the screws and stuff off you can get in there with something to cut it open.....
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Old 21-01-2012, 12:53   #14
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Re: Epoxy or Polyester Question

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I agree totally, you may be making it worse than just leaving the wet core in there. No way to get at it from the bottom? although harder, I would think if you can get the screws and stuff off you can get in there with something to cut it open.....
In this case, that may be great advice. If you can get to the underside from , say, the chain locker, then the whole repair could be much easier. It sucks to crawl in a hole and then work overhead with resin running into your armpit, but depending on circumstances it may be worth enduring the misery. Pulpit pads are usually pretty far forward and right outboard, in a hard to reach corner. Definitely worth checking though.
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Old 21-01-2012, 13:15   #15
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Re: Epoxy or Polyester Question

One thing too is towards the edges of a deck on a lot of boats the core may run out and be only partially cored, the rest solid glass. Under my stanchions it's half n half.
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