Hairspray Trick Addendum

If you are reading more about using hairspray to pre-wet rc models before they are glasses...

This works great with balsa models. It seems to be a pretty reproducible effect on wood because the wood absorbs some of the hairspray. The wood keeps the spray wetter so it does not dry out as fast. Fast forward to a foam model. Foam does not absorb any liquid, relatively speaking. Raw hairspray dries really quickly. This is a problem, we have found in many wrecked sets of cloth that if the hairspray polymerizes past a certain (not discussed in this article) point, the epoxy will not wet the surface.

What it does do is bunch up the glass when you spread the resin. Pretty quickly you can see that something is wrong because it just does not behave. You cannot straighten out the new wrinkles fast enough to get in front of it. The weight of the resin does not hold down the old wrinkles,and you make a mess. If this starts happening, we just yank off the damaged glass and toss it. Yeah, it seems wrong at the time, but we have no idea how to clean it. Always looking for hints on that one.

After the glass is tossed, we roller the wet surface of the model to spread the remnant epoxy. That is just to help fill in a pockets or spread any runs. It just air-dries after that, just leave it. When it is dry, remeasure your glass and do it again.

All in all, the hairspray trick rocks, on wooden models. Not so good on foamies.

Remember try to do your epoxy work in warm or hot conditions at the lowest allowable humidities. Yesterday, a thunderstorm snuck up on us and we had a very energetic pot of Loctite 60min epoxy. It fumed and melted several  plastic cups and unbound the wax on a paper coffee cup in the span of 1min. Finally, it melted several plastic shopping bags while we ran cold water over it.

Basic chemistry class says, take the heat away from exothermic (heat generating) reactions to slow or reduce them. Live with a chemist and you know these things.

Practical Composites: Fiberglass Over Wood

We are putting together some good pieces for everyone see how we are doing it. The big tip that we can tell everyone is hair spray. It is too funny to think of either of us ever sing hairspray. One has been bald for half of his life, and I have never been a big coiffure kind of guy.

The pictures that I am including are of a model that is 57" (143cm) x 6" (15cm)  wide and 4" (10cm) tall.

                       

The glass sued is standard s-glass, 2oz per yd glass from Aircraft Spruce . Our experience shows for fuselages, two plies is more than enough for fuselages. Make sure that your plies are pig enough to cover all of the piece and hang over about an inch (2-3cm). More than that makes it hard to support the piece, the fabric keeps pulling away from the edge  or it gets tangled.

Apply the hairspray liberally to wet the surface of the cloth, then use a foam roller to spread the spray and wet all of the glass. It takes a few minutes to work the whole surface. When it dries, it will feel more like paper than silk.

Having learned the hard way. You can let these dry for 15min or so, until they are not tacky to touch. However, do NOT let them dry for lunch and a trip to the hobby shop. The hair spray dries too much and coats the glass so that the resin does not stick. That is bad, it will just wreck your finish and everything will look all orange peel or like bubble city.

I hope this helps with your projects.