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Author Topic: Using finishing epoxy for the first time  (Read 1381 times)

clockworks

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Re: Using finishing epoxy for the first time
« Reply #25 on: May 23, 2019, 11:49:37 AM »

The 35gsm cloth turned up this morning, so I've just done one of the hull sides. Much easier to work with than the 17gsm.  I'll do the other side tomorrow, but leave the curved bottom until the spraymount gets here.
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mrzippy

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Re: Using finishing epoxy for the first time
« Reply #26 on: May 23, 2019, 02:05:02 PM »

Hi Tug Fanatic,
Yes have used all the West permutations over the years and in my opinion its the best of the bunch -
dries rock hard and crystal clear, ideal if you want a glass like surface over natural timber decks etc,
just very expensive for the small amounts modellers require.

I use Easy Composites EL2 Epoxy Laminating Resin and AT3 slow setting hardener -
now states between 90 -115 minutes working times.

https://www.easycomposites.co.uk/#!/resin-gel-silicone-adhesive/epoxy-resin/EL2-epoxy-laminating-resin.html

Hi Colin, unfortunately thinks I'll be sticking to what I know works in the future,
great shame it was highly recommended by aeromodelling friends who swear by it,
plus since recently contracting a rare blood cancer (Polycythemia Vera Rubra)
I now have allergic reactions to epoxy fumes resulting in blisters and swelling around my eyes,
I hoped the water based would be the answer to this problem.

My concerns are how many coats of the stuff do you need to apply in the first instance
to fill only the tiniest weave of the lightest glass cloth on the planet,
and its long term strength etc.
Many of my boats are now approaching 30 years old and look as good as the day they were built surface finish wise,
I put this down to the stability of the epoxy/glass foundation under the paint,
I find it hard to believe that a water based product will do the same job long term.
regards Paul




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Colin Bishop

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Re: Using finishing epoxy for the first time
« Reply #27 on: May 23, 2019, 02:35:18 PM »

In ye olden dayes my hulls, and those of others were planking in balsa and then 'plated' with gumstrip paper using a weak solution of Cascamite instead of water and sealed with a couple of coats of shellac before painting. Totally green, durable and organic! Easy to rub down and a lovely finish.

Nothing like beetle juice really.

Colin
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Tug Fanatic

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Re: Using finishing epoxy for the first time
« Reply #28 on: May 23, 2019, 04:06:34 PM »

In ye olden dayes my hulls, and those of others were planking in balsa and then 'plated' with gumstrip paper using a weak solution of Cascamite instead of water and sealed with a couple of coats of shellac before painting. Totally green, durable and organic! Easy to rub down and a lovely finish.

Nothing like beetle juice really.

Colin
I had not heard of that one but I wonder why gummed paper rather than just heavy brown wrapping paper.

Over recent years I have been amazed at the variety of hull coverings used which have included tights, garden fleece, dressmaking fabic etc and the glues which have included both pond waterproofer and indoor polyurethane varnish.

By the time I am not sure about the uv, & other, stability of the alternative materials and have doubts about some of the glues I will not be trying any of them.


There are times when trying to save a few quid makes little sense to me.
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Colin Bishop

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Re: Using finishing epoxy for the first time
« Reply #29 on: May 23, 2019, 04:38:09 PM »

Quote
I had not heard of that one but I wonder why gummed paper rather than just heavy brown wrapping paper.

Making a gummed paper hull over a mould pre dated GRP moulding. The gumstrip is of course sticky backed and requires water to activate it. When it dries it shrinks slightly giving a very smooth surface and as long as what you are sticking it to is smooth then that is what you get on the outside, no awkward ridges that have to be sanded down as with resin on cloth. I just used to add a bit of Cascamite to the water mix on the belt and braces principle.

One other advantage of this method is that it also lends itself to simulating plating. My Granada below had 5 years hard use on the MPBA regatta circuit in the 1980s and is still in one piece although long retired now.

Colin

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DaveM

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Re: Using finishing epoxy for the first time
« Reply #30 on: May 23, 2019, 04:55:42 PM »

"...no awkward ridges that have to be sanded down as with resin on cloth"
Admiral
You ain't doin' it right, m'duck.
DaveM


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Colin Bishop

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Re: Using finishing epoxy for the first time
« Reply #31 on: May 23, 2019, 05:13:39 PM »

And nor are most of us Dave, we don't have your years and years and years and etc. practice. Resin of either the polyester or epoxy variety has never endeared itself to me.

Just tested my Huntsman on the bench for Mayhem and the motor extracted itself from the mount as the vibration had loosened the securing screws. Now replaced with Loctite and all other screws, nuts etc. checked for tightness.

Colin
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clockworks

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Re: Using finishing epoxy for the first time
« Reply #32 on: May 24, 2019, 07:28:16 PM »

Spray mount arrived this morning, so I did the hull bottom. So much easier than laying the glass over epoxy!


The hardest part was cutting the glass cloth. The stuff is so slippery that I'm finding it next to impossible to get anything close to a straight edge. Just as well I left a few inches spare on all sides.
Oh, and I kept catching the cloth on the rough skin on my fingers. Reckon I need to start using hand cream, or wear disposable gloves when handling cloth.
Got a couple of small ripples where I wasn't thorough enough with the squeegee credit card.


I'll sand off the excess tomorrow, and give the whole thing a second (thinned) coat to fill the weave, then sand it back a little before glueing the deck in place.


Does thinning with IPA affect the curing time?
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JimG

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Re: Using finishing epoxy for the first time
« Reply #33 on: May 24, 2019, 08:03:37 PM »

I find cutting lightweight glass cloth is easier using a scalpel. Lay it out on a flat surface and use a metal ruler to cut against. You need to use a bit of pressure to cut it cleanly and a fresh blade is best as they will blunt relatively quickly.
Jim
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DaveM

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Re: Using finishing epoxy for the first time
« Reply #34 on: May 24, 2019, 10:53:05 PM »

Does thinning with IPA affect the curing time?
I can't answer that because I've always used it thinned. It's usually ready to be feathered around the edges after three or four hours at room temperature, though.
As regards cutting the stuff I concluded that a decent pair of dressmaking scissors is the best method, so I bought Liz a new pair and nicked her old ones! I can also sympathise with the catching of the weave with rough skin. Been there and done it. I now rub my hands with 400 grit silicarb paper before handling the stuff. Hand cream would almost certainly infect the resin.
DaveM
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clockworks

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Re: Using finishing epoxy for the first time
« Reply #35 on: May 24, 2019, 11:33:39 PM »

I think I need to sort out a larger work surface for cutting and building. Main problem is trying to cut a partially folded sheet of cloth. Probably find it easier if it was opened out and laid flat.


I meant to say working time rather than curing time. It was just starting to thicken as I was finishing, so I hope thinning won't reduce working time.
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clockworks

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Re: Using finishing epoxy for the first time
« Reply #36 on: May 25, 2019, 03:42:25 PM »

Second coat of finishing epoxy applied this morning. I thinned it with IPA this time, which made brushing a lot easier. It did seem to extend the working time quite substantially, as well as the curing time. I will definitely have to leave it to cure overnight.


I'm wondering what to do next - sand it down then prime and fill, dust on a guide coat first, or just prime it as is before sanding?
I'm planning to use Halfords car paints, and Holts Cataloy knifing putty to fill any imperfections.
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DaveM

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Re: Using finishing epoxy for the first time
« Reply #37 on: May 25, 2019, 05:36:36 PM »

Leaving it overnight is never a bad option. Like I said somewhere else, the two biggest enemies of a decent finish are dust and impatience.
I simply sand it again (240 silicarb, followed by 320); dust off well; use a tack-rag, and then apply Halfraud's yellow high-build primer/undercoat. Don't forget the 'sniff test' to check that the stuff has set. Works every time for me.

DaveM
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clockworks

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Re: Using finishing epoxy for the first time
« Reply #38 on: May 25, 2019, 06:47:52 PM »

I'll pick up some yellow primer, could save a lot of time over using knifing putty.
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