Backing Plates and doublers- Aluminum or Fiberglass?

[Chotu]

Originally Posted by freshalaska

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.

[sagablu]

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/

[s/v Jedi]

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

And a Diablo 10” 60-teeth crosscut blade for straight cuts, marking that blade for fiberglass only as it dulls too much for clean cuts in wood.

[Chotu]

Originally Posted by s/v Jedi

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

And a Diablo 10” 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 3” box beams.

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

As it turned out, I didn’t need to grind. Ha ha.

But on this sheet I’ll be using the jigsaw.

[s/v Jedi]

These carbide tipped blades cut really well. This is 3/4” thick fiberglass that I laid up myself using woven roving and 1708.

[s/v Jedi]

After primer and topcoat it looks like this

[GRIT]

Nice job Jedi.

Looks great.

Cheers.
Paul.

[Chotu]

Originally Posted by s/v Jedi

These carbide tipped blades cut really well. This is 3/4” 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, I’m making my own toilet bowl for a composting (desiccating) toilet. Ha ha

Very precise and perfect work, Jedi.

[clockwork orange]

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.

[Benz]

Originally Posted by Chotu

There’s a thing about epoxy I’ve 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.

That’s basically where I’m 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, I’ve 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.

It’s 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?

[Chotu]

Originally Posted by Benz

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.

[Ken Pole]

plywood epoxied all 'round.

[guyrj33]

Originally Posted by sagablu

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.

[George DuBose]

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.

[zstine]

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