1/32 balsa covering

[mark1993]

I tried something different this time on my series 400 Spitfire. I covered the plane with balsa and then with tissue paper. i was not happy with the result because the balsa would become bent out of shape and would not fit properly to the plane. If some one could give me a brief rundown on how to cover with balsa or how they do it. It would be greatly appreciated. Thanks

Mark1993

[John G. Jedinak]

Mark...........Hmmmmm. Thinking you wet the tissue to shrink it after applying to the balsa. If this was the case, likely the moisture affected the balsa...only a guess..........luck, JGJ

[kittyfritters]

Covering with balsa...get all the people in this forum together and they could probably write a book on the subject.

The two basic techiques for fuselages are fill-in and planking with a several variations on how each technique is used. Wings are usually covered with sheet. Which technique you use and how thick the wood is depends on whether the model is static or flying, and if flying, how it is powered. Wood covered models are generally more durable. With really careful workmanship, rubber powered models of about 24 inch span or larger can be successfully completely covered with wood. On smaller models you usually use a little fill-in around the nose and other areas where reinforcement for handling is useful.

Whatever technique you use to apply the wood, you have to seal the wood before applying tissue or silkspan over it, because you will either shrink the tissue or apply it wet to get proper smoothness. If you don't seal it first, any sheet covering, especially anything as thin as 1/32 sheet, will warp.

For a flying model you need a light weight sanding sealer such as talcum powder mixed into 50/50 nitrate dope and thinner. This sands to a glassy smoothness. For an static or engine powered model you can use an lacquer based auto body primer filler (Dupont CS131 Grey, if memory serves. Check with your local auto paint supplier.) These fill well, build up with very few coats and sand easily. That's the secret behind the finish on museum models. With any sanding sealer, be sure to wear a good particle mask when sanding.

Howard

[mark1993]

Ok thanks so much i couldnt understand why the wood was warping but now i understand. Also with finishing techniques thank you for all your help. Mark1993

[kittyfritters]

Mark,

That auto body primer/surfacer is Dupont 131S. It usually comes in gray. but used to be available in white and a kind of rust red color. I haven't bought any in a while.

Get the planking or sheeting as tightly jointed as you can. Use lightweight spackling compound (DAP Fast'N Final is good. Same thing as Plastic Balsa at 1/3 the price.) to fill in any holes or imperfections that are too small to fill with balsa. Sand smooth. Put on a coat of really thinned dope, let dry and sand to remove any standing fuzz. Apply the tissue or silkspan. After the tissue is dry apply as many coats of the primer/sealer , sanding between coats, as you need to remove any small imperfections, then apply your color. For a static model, using the auto body primer, I have sometimes been able to dispense with the tissue entirely if I got the underlying wood tight enough. On a flying model the tissue will add more strength and resist cracking besides providing a smooth surface for paint.

A neat trick, when doing a sheeted model of an airplane that had some fabric surfaces is to glue down some heavy thread to the wood surface to represent stringers or ribs before covering with tissue or silkspan. I've done this on display models the needed to withstand repeated moving and handling. It looks amazingly realistic (easy to get scale stringer spacing or rib count) and for a display model is much more durable than stick and tissue construction.

Hope this helps,


Howard

[kittyfritters]

OOPS! left something out. My last post should read:

Get the planking or sheeting as tightly jointed as you can. Use lightweight spackling compound (DAP Fast'N Final is good. Same thing as Plastic Balsa at 1/3 the price.) to fill in any holes or imperfections that are too small to fill with balsa. Sand smooth. Put on a coat of really thinned dope, let dry and sand to remove any standing fuzz. Put on a couple of coats of dope sanding sealer sanding smooth after each coat. Apply the tissue or silkspan. After the tissue is dry apply as many coats of the primer/sealer , sanding between coats, as you need to remove any small imperfections, then apply your color. For a static model, using the auto body primer, I have sometimes been able to dispense with the tissue entirely if I got the underlying wood tight enough. On a flying model the tissue will add more strength and resist cracking besides providing a smooth surface for paint.

Sorry about that.

By the way, some guys have put on a coat of really thinned dope to make the fuzz stand up (sort of shaving cream for balsa) and after sanding applied a coat of nearly full strength dope to waterproof, then used a few coats of talcum powder mixed in very thin Elmer's glue as sanding sealer. I've never tried this, but if you keep the Elmer's thin enough to be sandable when dry it should work.

Howard

[mark1993]

Thanks so much with your help it is greatly appreciated. I will hopefully soon post pictures. Thanks,

Mark