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Old 13-01-2021, 14:42   #16
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

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Originally Posted by freshalaska View Post
Won’t a dust mask take care of protecting your lungs?
Lungs?

If a grain or two of the cutting dust touches my skin I have an anaphylactic reaction. And I’m bed ridden for days. I can also die from this.

Do I need to put all this in my signature again? I suppose I will.
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Old 13-01-2021, 14:47   #17
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

I have used FRP 1/4 and 3/8th sheets as a backing plate, a bit less expensive than G-10 I believe. Hard as a rock. I used a sawzall with a metal blade to cut it. I was able to cut round holes with a regular hole saw for the thru-hulls. https://www.mcmaster.com/fiberglass/...rs-and-strips/
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Old 13-01-2021, 14:57   #18
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

I used this blade to cut curved parts: https://www.amazon.com/Bosch-T141HM1...s%2C223&sr=1-7

And a Diablo 10Ē 60-teeth crosscut blade for straight cuts, marking that blade for fiberglass only as it dulls too much for clean cuts in wood.
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Old 13-01-2021, 15:03   #19
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

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I used this blade to cut curved parts: https://www.amazon.com/Bosch-T141HM1...s%2C223&sr=1-7

And a Diablo 10Ē 60-teeth crosscut blade for straight cuts, marking that blade for fiberglass only as it dulls too much for clean cuts in wood.
Yes. I use similar for my fiberglass cuts

Although I got a perfect straight cut with a sawzall (!!!) when slicing one of my 3Ē box beams.

Plan was to make a rough cut and hit it with the grinder because it was fast.

As it turned out, I didnít need to grind. Ha ha.

But on this sheet Iíll be using the jigsaw.
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Epoxy can kill me like a kid smelling peanuts across the lunch room. Even the freshly machined dust from cured epoxy. Please donít suggest using it.
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Old 13-01-2021, 15:13   #20
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

These carbide tipped blades cut really well. This is 3/4Ē thick fiberglass that I laid up myself using woven roving and 1708.
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Old 13-01-2021, 15:15   #21
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

After primer and topcoat it looks like this
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Old 13-01-2021, 17:00   #22
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

Nice job Jedi.

Looks great.

Cheers.
Paul.
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Old 13-01-2021, 18:52   #23
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

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These carbide tipped blades cut really well. This is 3/4Ē thick fiberglass that I laid up myself using woven roving and 1708.
I pray to have even half this finish fiberglass skill when I make my toilet bowl.

Yes, Iím making my own toilet bowl for a composting (desiccating) toilet. Ha ha

Very precise and perfect work, Jedi.
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Old 13-01-2021, 19:34   #24
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

We use a lot of G10, FRP and GPO3 at work for just the type of parts, we use a diamond blade in the table saw and they last for months, we also use a diamond blade on a dedicated bandsaw and that thing is amazing. Each material has its uses but G10 a much better product than the others, it has a much higher fiber content and of course epoxy resin. It would be nice if someone made an equivalent product with VE resin but with your reaction to epoxy it might be worthwhile to layup your own.
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Old 14-01-2021, 04:22   #25
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

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Thereís a thing about epoxy Iíve discovered through all of this. When you machine it, even if cured for 5 years, it breaks the bonds and releases part of the polymer. Enough amines are released to give me an anaphylactic reaction.

Think kids dying from sniffing peanuts on a plane or in a cafeteria.

Thatís basically where Iím at.

The dust produces from cutting this is deadly.

Cutting the deck of my boat and stuff can be done very carefully with a hepa vacuum and help.

In this case, polyester is a no brainer.

Whenever I can find someone to do my chainplates and bow tube, Iíve found a good workaround. If they do polyester as a top coat to an epoxy project, it seals it off from the atmosphere and entombs it so I can come back on the boat. Otherwise, I have to leave for 6 months, minimum.

Itís serious stuff
When you say "Polyester as a topcoat" do you mean switching from epoxy to polyester during the lamination while the epoxy is still wet, and having an outside layer of cloth with poly? Have you researched this? I'd love to have it in my bag of tricks if it works ( I'm scoping a project where it would be extremely useful to be able to do this if it's feasible). Or is it a matter of letting the epoxy cure and then sloshing polyester resin over the peel-plied surface?
Any data on adhesion for either scenario?
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Old 14-01-2021, 04:45   #26
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

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When you say "Polyester as a topcoat" do you mean switching from epoxy to polyester during the lamination while the epoxy is still wet, and having an outside layer of cloth with poly? Have you researched this? I'd love to have it in my bag of tricks if it works ( I'm scoping a project where it would be extremely useful to be able to do this if it's feasible). Or is it a matter of letting the epoxy cure and then sloshing polyester resin over the peel-plied surface?
Any data on adhesion for either scenario?
Epoxy doesn’t need air to cure, as you know. So it can be mostly cured when the last bit of polyester goes on.

I don’t think I’d purposefully go wet on wet with polyester over epoxy, however.

I also wouldn’t use it structurally.

Think of it as paint. That’s really all it is in my case. You’re painting on a resin to hide something that’s below. It’s not a structural layer. No glass involved, just a top coat.

I’ve had it done it over partially kicked epoxy.

My previous help sealed off some epoxy work they did this way and I was able to get back on the boat because of it.
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Old 14-01-2021, 09:28   #27
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

plywood epoxied all 'round.
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Old 14-01-2021, 09:34   #28
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

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Originally Posted by sagablu View Post
I have used FRP 1/4 and 3/8th sheets as a backing plate, a bit less expensive than G-10 I believe. Hard as a rock. I used a sawzall with a metal blade to cut it. I was able to cut round holes with a regular hole saw for the thru-hulls. https://www.mcmaster.com/fiberglass/...rs-and-strips/
I've used this same material from McMaster for topping and backing plates, tough on saw blades and more than strong enough for backing plates.

G10 is nice stuff, total overkill for backing plates.
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Old 14-01-2021, 10:19   #29
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

For under deck backing plates for stanchions, etc. I have had good luck with HDPE, cutting board material. I use 1/4" or 1/2". I have even used it on deck, but it eventually breaks down from UV.
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Old 14-01-2021, 11:03   #30
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Re: Backing Plates and doublers- Aluminum or Fiberglass?

Structural FRP is the material of choice without question IMO. Main reason, no corrosion from dissimilar metals. SS bolts through AL will eventually cause problems unless you go through the PITA if isolation bushings. Tefgel does not last forever.

@George DuBose: HDPE will creep and should not be used for backing plates since you lose your pre-load.. it is also very flexible and would need to be extremely thick to spread loads adequately, which exacerbates the creep issue. You don't want creeps on your boat
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