Fiberglass

[DENNIS KARGOL]

I ‘m not happy with the job I do when fiber-glassing the firewall on to the fuselage. I’m aware of the balloon method.( never tried it yet) Is there a good way of making this process any easier and looking good and smooth?

[Dean McGinnes]

First, use a slow curing resin. One that lets you have at least 2 hours working time. Longer is even better.That means, you have maybe an hour to work in real time. An overnight cure is best.

Fill the T-nuts with vaseline. I use a small syringe to ensure it gets in all the screw threads.

I precut all my cloth. It looks like a plus sign when I am fastening a square or rectangular firewall to a similar front end. The center of the plus is of course, the same size as the firewall.

A round firewall gets a round patch about 1/2 to 3/4 inch extra radius. When the patch is first applied to the face of the firewall, I cut slits all around the edge so it will fold back without wrinkling.

Multiple layers of thin cloth is better than one of thick stuff. I use .75 oz. for nearly everything. Two layers on 1/2A’s, twice that for A/B, 6 for B/C gas models.

Now here is the very important part of all this. Cut the cloth such that the weave is at a 45 detree angle to the sides of the firewall. Cloth cut on a bias will be very easy to stick down over any and all compound curves.

Paint on a thin layer of resin for the first layer of cloth, and get it all stuck down with a stiff bristle brush used mostly in a dabbing or poking motion. Put the next layer on with no additional resin. Get it stuck down all around with the stiff brush. Add no resin unless it is impossible to get a portion of the cloth stuck down and then only where needed.

Use a pad of several thicknesses of paper towels to absorb any excess resin. It adds no strength and only adds weight.

I haven’t used the balloon as yet, but if you elect to, this is where you would inflate it and push it over the end of the fuselage.

When all is cured, I cut out the engine mount holes with a miniature hole cutter made of the appropriate sized brass tubing.

[Glenn Schneider]

What I found useful, lay out the fiberglass on a sheet of wax paper, get all the lines in the weave straight then give it a coat of dope and let it dry thoroughly. Now the glass is a little stiff and very manageable, wont fray as before. Cut it to size with a scissors and crease it where it is to go around sharp corners. Glue it down first with thin cya then give it a coat of epoxy or resin. Works for me. Thermals, Glenn

[DENNIS KARGOL]

I want to thank you for your help and advice. I really appreciate it. Sounds like tips that would work. I’ll give them a try. Thanks again.

[Anonymous]

Hey Glenn,
Great tip on the fiberglass.Did it the way you said …worked great. 😀
Thanks,
Denny

[JLorbiecki]

One thing that also helps is the use of 3m 77 SprayMount spray adhesive. Spray the glass or the structure and then press it in place. Push the epoxy through the glass and you are done. The 3M adhesive does not effect the epoxy…Or, I have also just used thin CA to glue the glass down. Very quick when everyting is already glued down…

Another trick is to use thinner glass (maybe 3/4 or 1 oz) and use two layers.

Also, it sometimes is easier to apply the fiberglass if you apply it at a 45 degree angle. The fibers will tend to “bend the corner” easier…

[Author]

Posts