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Dec 22, 2012, 07:48 PM
what goes up, must come down..
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A quick guide to epoxy fibreglassing


fwiw use a fibreglassing consolidating roller, like the one in the attached pic, an ally/alloy, they make life so much easier and you can roll out the excess resin with ease so not only will the end result be lighter, but it will actually be stronger
Weight WILL increase very quickly if too much resin is used, f'glass does get heavy if you aren't conscious of the fact
that said, this SSS can actually do with a bit more weight up fwd

i'm certainly not about to try and tell anyone how to suck eggs lol but here's a quick basic way to epoxy fibreglass, pretty much the same principal for repairing a boat...
~first give the epo foam you wish to f'glass a light sanding. this is important for two reasons... most epo finishes these days have a smooth wax like finish- epoxy wont stick to that at all, and you do want it to stick, you dont want the foam structure underneath to be able to move around so unless you are wrapping the foam but rather just repairing a spot, Polix is correct, it will peel off eventually. Also it will help the resin bind to the foam by having a mechanical key with the resultant scratching from the sanding. Sand until all the shine has been removed.
~then, preferably with the lightest epoxy fibreglassing cloth you can get, cut out the cloth to exact size patches for the work you wish to do, and when they are all cut out, number them with a marking pen so you know which order & where they need to be applied to the airframe
One layer will protect the frame quite remarkably, but doesnt do much for structural strength
Two layers will give you roughly triple the strength
eg if I wanted to strengthen the the wing root/fuse join area of a plane, I'd do at least 2 layers, first one say 10mm wide strip, 2nd layer say 20mm wide, different widths so when you're finished you dont have a f'glass "step" 2 layers high, rather it will smooth off, requiring very little sanding, if at all.
~find a small sheet of scrap plywood or whatever, this will be your "wet-out" board
Mix your resin, then with a disposable brush, brush some epoxy liberally accross the wetout board, not thick, but just covered. Lay your trimmed f'glass cloth onto the resin wet board. Use your consolidated roller to roll accross the cloth, what you are trying to achieve here is to have the cloth soak up the resin that you brushed onto the board, all you need is for the cloth weave to fill, NOT be saturated, this is where you save soooo much epoxy and reduce excess resin. As soon as you cant see any dry areas on the cloth weave, it is ready.
Leave the cloth on the board for a minute.
~very lightly brush some resin directly onto the area you will be laying the soaked cloth. I do mean lightly, all you are trying to achieve here is to fill the sanding scratches and lightly coat the area in epoxy to simply allow the epoxy to mechanically bind to the epo foam. Wipe off any runs or drips.
~Gently peel the soaked cloth off the board, lay on the wetted epo area on your plane, roll out with the roller. Again, all you need is the cloth weave to be only just filled, no excess epoxy whatsoever, you'd be surprised the small amount of resin required to do a proper smooth finish. If there are any dry areas visible on the cloth, simply drip a little on the dry spot and roll out again.
Once you get the hang of it, there should be no runs, cloth evenly resin rolled to the edges so there is almost nothing to sand, no furry egdes. The less sanding you have to do later, the less chances of damaging the epo by accidentally sanding off the edge of the hardened f'glass and sanding a groove into the epo- that peeves me lol

If sourcing a roller is too difficult, you can [I]dab[I] the cloth with a brush instead, but there is no way you'll have any where near the same degree of control of the resin, try the roller once and you'll never look back

Use latex disposable gloves, unless you enjoy sticky fingers
If you get epoxy on your skin, preferably let it dry, the peel off later. If you need girly clean hands, try scrubbing with an abrasive hand cleaner. There are solvents that will remove epoxy quickly from your skin eg eoxy thinners etc, but I prefer to avoid this because it will thin some epoxy resin enough to enter your skin/blood stream. Not dangerous, but not good for you either. Some boat builders I personally know have developed sever allergy to epoxy because of complacency, but that was from years of dealing specifically with epoxy.

Practise with resin, and you will be limited by only your imagination as to what you can do with it. Things like epoxy doesnt like sticking to shiny plastic, so for eg, if you want to make an air scoop, without sanding, f'glass over the corner of an ice cream contaner od bottom of a plastic coke bottle, dremmel cut out the shape you need and voila! you have a f'glass scoop. Better yet, if you use the [I]inside[I] of something like an ice cream container, then the outside of your air scoop will be very smooth, you've used the ice cream contaner as a mold
And I'd suggest a couple of practice runs on scrap foam, you'll pick it up quickly.

Paint brushes used are disposable, dispose of thoughtfully.
The roller, I generally just let the epoxy go hard on the roller (coz I'm lazy to clean lol), then later pull the roller off the handle, clean out the roller grooves with a wire wheel on an electric grinder, done in a minute or so

Oh, the roller pic is the best one, they are about 10mm diameter, but the direction of the grooves in the pic is best. You can get rollers where the grooves go the length of the roller, they are called splatter rollers, for good reason...

Anyhoo, thought I'd share some knowledge for those who may or may not be interested.
Personally I'll be epoxy glassing over the fuse wing mount bridge, with an inch or two either end of the bridge (the bit that Chris had tear out), then continuing down the sides of the fuse (fore & aft of the wings) to wrap around the fuselage, and since I've gone that far I will continue along the underside of the nose for landing protection.

I'll post this on my RCG blog, if you need a hand please ask there so we dont clutter/derail this excellent SSS thread

Hope this helps someone
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Dec 22, 2012, 08:00 PM
Spearheading an Alliance
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glassing info


AH,

Just wanted to say thanks for posting this. Great info! I look forward to seeing photos of your fiber glass reinforcements on the SSS.

BG
Dec 23, 2012, 02:45 AM
what goes up, must come down..
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Originally Posted by BravoGolf
AH,

Just wanted to say thanks for posting this. Great info! I look forward to seeing photos of your fiber glass reinforcements on the SSS.

BG
my pleasure mate, when I do get to fibreglassing I'll post a pic or 2, although when I glass I generally go hell for leather to get it done, kinda forget to take pics lol
Jan 03, 2013, 04:57 PM
Crashaffinity on youtube
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btw, thanks for your tips, i had to glass my hexa copter arm after it snapped, used your tips to get a much better and much stronger fix
Jan 04, 2013, 07:19 AM
what goes up, must come down..
AussieHoppy's Avatar
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Quote:
Originally Posted by polix
btw, thanks for your tips, i had to glass my hexa copter arm after it snapped, used your tips to get a much better and much stronger fix
it is amazing what you can do with f'glass, limited only by your imagination, glad it has been of use for you

something I should have mentioned in my above blurb, is that epoxy is safe for epo, eps, etc but always do a test patch before commiting to a polyester f'glassing job.

Also there are chopped strand mat (CSM) and cloth that are specific to poly resin or epoxy resin.
For example, a poly suitable CSM has a binder that holds all the CSM together, then when wet out with a catalized batch of poly resin the CSM binder disolves and literally becomes limp, which is great for being able to conform around corners and radius edges.
But, if you use epoxy resin on the poly friendly CSM the binder wont release, so you have to work quite hard to have the CSM to conform to shape on the product being fibreglass.

Oh, a little tip... if an insect or paint brush hair lands on your shiny, wet f'glass job, dont try and pick it out... let it cure, the sand the blemish off, you'd never know anything was there


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