tasesq

Hi All,

Well I have bitten the bullet and am trying to learn fibreglassing (for a Sig Senior).

I have made up a test piece with all the types of surfaces of the model (compound curves, window cutouts, hinge holes, balsa filler etc).

I mixed about 2.6grams of resin for this piece (about 14x6cm in size) and it seemed to be just enough.

I poured it on, and spread it out with a key card from the hilton! I than used an acid brush to work in the edges/curves/cutouts etc.

I then squeegied it with the card (the cloth moved somewhat, but i managed to get it back ok).

I was not sure how much to squeegie? As i squeegied it, you could see parts of the cloth 'catching' and lifting the going white. I had to just squeegie gently, and try to get some resin off the surface, but not lift the cloth. Squeeging, but not dragging the cloth. This was quite hard!

I then rolled a toilet roll over a couple of times.

Now the surface is not shiny (well it is, but is a dull kind of shiny compared to the resin in the cloth inside the window cutout, where i couldn't squeegie, which looks 'wet'. the rest looks 'dry'), and i can see the weave of the cloth clearly if i tilt my head to the side in the light (the pictures are hard to show this).

Have a done all this ok? I have bought a spray can of grey primer/filler from the auto store.

How long do i need to wait before sanding? (it is about 28C and 75% humidity here - will get down to 20 overnight)

What grade paper do i lightly sand with before priming?

Once primed, what grade do i block sand with?

Sorry for the painfully slow description! Thanks

Tired Old Man

My Feedback: (1)

Looks like you did things just about right. For fear of removing too much during the squeege process you likely left a little too much but that's ok. If it looks wet then there is still too much resin on and under the cloth. The reason for the squeegee process is to prevent the glass from "floating" on a layer of resin over the base material. Looking like it's almost dry is good. Wet is bad.

As for sanding, wait for a couple of days or until the surface feels hard. You can trim off any excess glass with a sharp single edge razor blade when the resin cures to a "rubbery" stage. When sandng you do not want to cut the weave of the glass with the sandpaper. 320-400 paper is as course as I would go. I would fill the weave with a light primer in several coats, sanded between, to get that smooth finish prior to the color coat.

tasesq

Thanks SilverSurfer,

I have made up another two trial pieces yesterday - i don't think i left the first one for enough time to cure. The second two I did last night, and tonight i sanded them lightly with 180grit to get off the edge cloth, and then did a couple of coats of primer.

I'll let you know how they come out tom!

Ed Smith

Just going by the pictures it looks as if you have used a rather heavy cloth. The max weight of cloth to use for your purpose would be 3/4oz cloth. Your cloth may be that, It just looks a little heavier to me.

Ed S

daven

My Feedback: (1)

I was thinking the same thing Ed. The glass looks very thick in the pictures.

This may be a dumb question, but are you trying to fiberglass over an open structure?

I've never liked the toilet paper method, I use those plastic bondo scrapers you can buy at most auto repair stores. I take the wider scrapers and cut them down around 1 1/2" - 2" wide, which is much easier to work with. These scrapers have more flex to them, and a tapered edge that helps limit the snagging you were getting with the credit type card.

dreadnaut

My Feedback: (5)

I use old decks of playing cards to squegee with. The hotel key is about as stiff as a credit card, and that may accout for the pulling.

tasesq

Hi guys,

Thanks for the replies.

I was using 3/4oz cloth. The hole in the trial piece above was a test for me, as i have some holes (baggage door, window cutouts etc) on the model so i wanted to see how to go about glassing with a big square hole. I was able to just cut away the cloth in the hole with a knife after a few hours.

I made two extra trial pieces and I had a bit better luck with those. I squeegied (still with the hotel card) but did it a little lighter.

This time i let it all dry for longer and sprayed primer. The problem this time was similar in that it took about 5 coats to get rid of the weave showing through the primer. With help of paul from www.airfieldmodels.com, i realised that i probably was not using the correct primer and/or did not apply enough resin. I think that the primer did not have enough substance to fill the weave of the cloth. Paul reccommended i let the first coat of resin go off, then apply a light second coat. I will try that next time.

The primer was from Repco here in Australia. It said "Primer/filler" but not "high build".

What brand of primer do people here in Aus use? I will be painting (eventually) with white paint.

Thanks!

tasesq

Here's how one of the trial pieces came out after the 5 coats of primer / sanding. It was nice and smooth.

The primer added about 0.2 grams on a piece this small (not much) but i can't do 5 coats with sanding on an entire aeroplane. It will take months. Hopefully I can find a primer that only needs two coats with two sands and/or one coat and one sand after a second coat of resin.

batchelc

My Feedback: (7)

if your using an ester resin (polyester/vyinalester) Goto the local auto paint store and ask for filler-primer. One coat should work, but go easy since it's heavy. If you're using epoxy you can mix a thin slurry of microbaloons and epoxy and put it on thin as it is also heavy. You can also leave the cloth a bit resin rich and use some wax paper while its drying to give you a nice even coat. Although this is hard to do without vacuum bagging it. There is no real quick, easy, lightweight method.

Rudeboy

I once had a nasty case of pinholes when trying to paint a wing that I had covered in japanese tissue (or whatever you call it over there). In a moment of desperation I went to the automotive filler-primer... but instead of spraying it on, I brushed it on to get those pinholes filled. Don't do that, and do what the previous poster said: "go easy on the stuff!" It took me several days (and a truckload of sandpaper) to get that thing sanded down again. That filler-primer stuff is hard as nails when completely cured!

If you use light cloth on a well prepared surface (this is important), you should need very little filler. A couple of base coats with a sanding in between should do it. When sanding the "filling coats" you should cut it back until you reach the glass. Before you start your finish however, you have to make sure the glass is completely covered, or else you will be in pinhole-hell...

Tired Old Man

My Feedback: (1)

A little trick for trimming all the 'glass over runs and loose, frayed fibers. Wait until the resin and glass have gone off and attained that stage where everything is just beyond rubbery but not yet hard. Use a sharp single edge razor blade to trim off the unwanted stuff at that time. Keep a paper towel wet with acetone so you can wipe the semi set stuff off the blade and always have a good edge on the blade.

saramos

The primer I use for filling weave is Duplicolor High Build primer. It takes about 3 coats to get a good finish. I wet sand between coats with 360 grit. The sanding goes quick. I recommend a coat a day. If I get impatient, I do a coat in the morning, sand in the evening, do another coat at night and repeat the next day. When filling the weave, I also find and fill any other imperfections. For stuff that's just a bit much for primer, I use spot body putty. For anything much larger, I'll use epoxy/phenolic microballoons. When all is filled, I give a final coat of sandable (not high build) primer. Let dry well, and one last sanding. I'm then ready to add surface details, panel lines, rivets, inspection covers...

Paul Johnson has a ton of excellent info on his website.

Scott

billekens

Hi Saramos,
In your last posting you mentioned that Paul Jonson had excellent info on his website. Would you have the URL of his website?
Thanks

j.duncker

My Feedback: (2)

Since you arr experimenting, get a foam paint roller, the smaller the better. I use a 50mm [2 in ] wide one. I find this much easier to use than the credit card.

You avoid dragging the cloth and and can control the application of the resin by moving it to dry areas.

I find I need a second coat after rubbing down the first and still get some pinholes.