On curing, the outer sandwich is slid off the mylar tube. The acetate layers are now both inside and outside the glass tube and have to be removed. The resulting glass boom has a single opening with a 3/8" overlap which is glued with CA. Instead of acetate film, mylar may be used, but I find the finish using acetate is far superior. This system has been used on everything from 1/2A pylon racers to 15 foot cross country Thermal soarers. This method is equally applicable to rolling 1/2" diam. ballast tubes. I have never seen anyone else use this method.
The acetate I use is 3 thou clear in a 36" roll which was purchased from a drafting supply company. Regular drafting mylar works just as well, but is expensive to purchase. If you know anyone in the drafting game, I'm sure you can get off-cuts for free. Even 6" wide strips will do a fuselage 1.75" diameter. Old discarded drawings will work too. The mat finish on the mylar will wash off wi acetone giving a clear glossy surface, but this is not really necessary if the fuselage is to be painted. The acetate sheet does not need any release wax is the resin will not adhere to it. Most of the mylar I have used will also separate without waxing, but occasionally I get some that will not release. Do some tests before using it. I normally use coloured pigment in the glass layup and the boom does not need painting except for a little touch up on the seam. The finish is usually better than I can achieve by painting anyway."
1. Tail boom of 15 foot Overlander XC model circa 1985
2 and 3. Mandrel and boom Spinifex 100 ( ply fuselage Spinifex 100 plans Sept 86 RC Modeler)
4 and 5. Fuselage boom and mandrel for 3M Prospector
5 and 7. Fuselage boom and mandrel 2 metre Prospector
The two on right are flat bottomed, rounded top FG mandrels from my earlier Spinifex versions. Just to show that the system works with different shape formers.
From Top to Bottom
Plug and fuselage boom and mandrel of 3 metre Prospector
Fuselage and mandrel of 2 metre Prospector. Note old geology map mylar.
Wing bolts go through fuselage to blind nuts in wing.
Fuselage and mandrel 60" slope racer
Fuselage 60" HLG weight 35 gm
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