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Old 01-02-2013, 15:16   #1
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Welding near Fiberglass?

I have a welder who is going to weld a bow roller to the stem plate of my boat. My question is how much do I have to worry about doing damage to fiberglass that is underneath the stem plate. The glass adjacent to it is a decent distance away. I'm more worried about the heat buildup during the weld and a risk of starting a fire or damaging the integrity of the fiberglass. The thickness of the stainless steel plate is about a half inch thick. I know I could pull the stem plate off and have it welded away from the boat but this is a much easier option if it is safe. Thanks!
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Old 01-02-2013, 15:29   #2
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Re: Welding near Fiberglass?

It really depends on the quality of the welder and his/her equipment as to what kind of job you are going to get. I have seen welders blow a hole through the material being welded or do a serious warp job by overheating ... either of which would seriously damage your fiberglass.

Just pull it off and get it done.
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Old 01-02-2013, 15:41   #3
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Re: Welding near Fiberglass?

are you saying the stemhead assy in the pic is stainless...? Looks like aluminum... anyway, I assume you want to weld that small roller on the plate somewhere. WOW.. half inch plate..... really? That will soak up the heat pretty well, In fact, your welder will need to weld very hot or the weld will look good, but have no penetration into the 1/2 plate. Burn the glass? Hard to say really, can you put a garden sprayer below decks spraying water on the fiberglass? If so, I might be tempted to go for it. Otherwise not. It could ruin the caulking either way and force you to eventually remove the fitting for that....
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Old 01-02-2013, 16:04   #4
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Re: Welding near Fiberglass?

Stainless stick electrodes would do that job better then MIG with dissimilar thicknesses imo. If the fibreglass was in direct contact with underside of the plate where the welding is being done I'd either remove the stem for welding or just bolt the roller on. OTOH if its a distance away, cooling with water in the appropriate places while welding (e.g. using wet rags) will stop the heat transferring to the glass. Fortunately, stainless steel is a poor conductor of heat (relatively speaking) so this is a practical solution as the "red" heat won't radiate too far from the welding area.

Of course, make sure the stem is actually stainless - the half inch thickness sounds a bit suss - (do a scratch test if not sure), because if it's aluminium......
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Old 01-02-2013, 16:14   #5
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Re: Welding near Fiberglass?

Sparks, grinding are all potentially damaging. The glass will handle a little more than what your skin can, NOT MUCH!
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Old 01-02-2013, 16:19   #6
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Re: Welding near Fiberglass?

Remove it, I have done welding and am pretty sure this will be too much heat for the fiberglass. I do not see anyway to do this without damaging the glass.
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Old 01-02-2013, 16:21   #7
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Re: Welding near Fiberglass?

Wow, I didn't think of the aluminum possibility. It's a 1978 Tartan 30 and after doing a little looking I'm pretty sure it is aluminum. I guess I'll just drill through the plate and through bolt it?
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Old 01-02-2013, 16:24   #8
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Re: Welding near Fiberglass?

Thanks for the advice and catching that. Much appreciated
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Old 01-02-2013, 16:25   #9
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Re: Welding near Fiberglass?

Put on a large backing plate and it will be plenty strong!
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Old 01-02-2013, 18:19   #10
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Re: Welding near Fiberglass?

I agree, the bow plate looks like aluminum, so bolting is an option. No welding, if you aren't going to remove the piece, the welding will damage your glass.
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Old 01-02-2013, 18:26   #11
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Re: Welding near Fiberglass?

You've found a different solution but you can always (except with steel) weld an inch, squirt it with a hose, weld another inch, hose again, etc. We did that with compressed air on thin sheet metal often to prevent warping. It sucks when your whole door goes CLUNK and pops in 3" because you warped the metal.
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