Hi, After having lots of covering blister up in a hot car it occurred to me that perforating all the ribs etc. in a built-up balsa wing would allow the air inside to escape. So now I do that and it seems to reduce the blistering a great deal.

Say what?

Ummm.. so you say that you vented the wing to allow air to flow through?

Did I get that right?

CGr.

Hi,

A pin hole in each bay (underside near the TE) is normal when covering with any of the films to allow the eapanded air to escape and stop it lifting of the freshly covered area, the holes are almost invisible. When I have a newly built/covered model I put it in my van in the hot sun for a few hours and then re-shrink the film. It seems to keep the film tight for years after this process.

Cheers,

Colin

Well, of all the plane that I own and fly, I've never pierced anything to allow air flow... other than if I have a cowl over the engine.

CGr.

As the atmospheric temperature or pressure varies, the air trapped inside the wing (for example) expands or contracts. Instead of having the covering balloon out and separate from the wood I give it a route to escape (or come in). This way the covering doesn't have to get pierced everywhere.

Well, at 200 feet AGL, I don't think it matters much.

CGr.

I found out a long time ago to always have the wing vented so that no one area can build up pressure for any reason. When I build a wing, I always have a fair sized hole in each rib (often used to route aileron cables) as well as a vent between the spar webbing and the forward area of the wing. If not, even the heat of the covering iron can cause enough expansion in any cavity to force the covering to separate from the rib/spar surface.