Is There An Alternative Balsa Sealer To Dope?

[iflylilplanes]

DOPE, The last time I purchased a can of dope I paid $15AU for 1lt, (I put the empty can out, and it still had the price tag on it), I called my LHS for price and availability $40AU for 1lt, and it gets more expensive the less you buy, I looked around via the web and found that my LHS was the cheapest in the city.

I asked this question on RCG, is there a cheaper alternative to dope? I only need to seal balsa, no tissue, no covering of any sort, just balsa needs to be sealed ready for painting.

This thread is a copy of a post in another thread (a build log) asking here as well to reach more members.

Your suggestions will be considered.

Many Thanks,

Dave

[Jim]

Hi Dave

Instead of dope I use water based varnish from the local DIY shed. Some people mix talcum powder in with dope to make sanding sealer so I'm sure you could do the same with water based varnish.

Personally I would cover the balsa in 34 micron laminating film then paint over that, much lighter as the grain is sealed by the film and paint can be put over the film after roughing up with Scotchbrite.

[iflylilplanes]

I am going to try Doculam soon on a resto of an Aeroflyte Invader, going to use it on the wings and tailplane with tissue and paint, but, the Coachman is wood only, no open structures. I've always been wary of water based paints and glues on sheet balsa (bad experience once), the Coachman is dead straight at this stage of the build, so I don't want to induce warps now.

I'm going to spend some time in the paint section this weekend and read the cans, I'm sure there will be some product that will do the job.

I have managed to find dope for full size a little cheaper, about $36AU a litre, but it comes in 4lt cans at $125.00 + GST (don't need that much)

Anyway, I'll keep looking for advice online and do research myself.

Thanks,

Dave

[bluejets]

You might want to give a primer filler spray pack a try. (automotive)

We use it to seal and prime timber patterns for casting.

If you apply very light coats from a good distance away it should work ok without too much weight.

One to make the prickles stand up and one to seal.

It is very easy to sand and it comes up ultra smooth.

[Wayne_H]

G'day Dave,

Similar to Jim's suggestion - I have had very good results with cheap water based ceiling paint brushed on. Look for the type that is advertised as not requiring a primer. The cheaper no-name brands tend to work best, probably because they are more filler than pigment . To keep the weight down, sand it off with wet 'n dry (used wet to keep the dust down) until the grain starts to come through, repeat with a second coat & touch up a third time where you may have been a little too exuberant . Works surprisingly well and for stuff-all extra weight.

[Andyh]

Always used Banana oil prior to sanding in the days before foam and heatshrink film.

[iflylilplanes]

Always wondered what banana oil was, is it derived from bananas, or is it called banana oil because of it's colour. Never seen it for sale in any hobby shop.

[Shaun]

From memory banana oil was a type of virtually non shrinking dope made with isoamyl acetate as a solvent. It would craze if used over regular dope and was useful on lightweight structures.

Water based floor varnish works to seal balsa but it isn't fuel proof. I've used coloured vinyl matt Valspar emulsion paint with Matt water based floor varnish over on my WW1 models covered in solartex. Polyurethane was used around the nose area to fuel proof where any petrol would go..

Shaun.

[DX-SFX]

Always wondered what banana oil was, is it derived from bananas, or is it called banana oil because of it's colour. Never seen it for sale in any hobby shop.

It was called Banana Oil because it smelt like bananas but is nothing to do with them. You can add it to dope to control the amount of shrinkage and it also makes the doped surface more flexible. Microfilm used for those gossamer thin indoor model aircraft is a mixture of dope and banana oil poured onto the surface of water where it dries as an ultra thin film. It goes on like polyurethane varnish but it's acetone based. It's a bit archaic given the choice of modern paints to be had.