I have design a model with an aim to try a technique, which is new to me. Iím sure someone somewhere has invented something similar already, but I havenít come across just exactly the same approach. My aim was to design a model compatible with FAI S3/S6 class dimension requirement and with weight below 10 grams excluding recovery.
In the beginning of last season I built such model using a kind of tracing paper. The overall design was simple enough, dimensions were correct and model flew very well.
However, I did not managed to get its weight below 10 grams. Also, despite the paper good quality and a coat of light varnish the body sucks moisture from the air limiting conditions the model can be flown.
A member of our club who also flies in FAI competitions showed me a body made of laminating pouches. I understood that the building technique is quite elaborate and requires a proper mandrel and long thermal treatment. Both were not available to me, so I devised a simpler method.
The body and, in absence of better alternative, the nose cove are made of two layer laminate. The outer layer is a half of 150 micron laminating pouch (so, it is 75 micron thick). The inner layer is aluminised mylar. Iíve tried 15 and 5 micron mylar. Both types work very well, although laminate with 5 micron film is a bit too soft in my opinion. 75 micron laminating pouch film & 15 micron mylar have area density of 102g/m^2.
Both sheets are wrapped around BT-60 body tube with a 3mm seam. The laminate is temporally fixed along the seam with masking type. After that I used an ordinary domestic iron to iron gradually the pouch to the mylar layer starting from the seam. The same technique is used to form the nose cone and the tail transition. I do not have access to 10mm motors used by FAI chaps , so the model is design for 13mm A-class motors. Larger motor tube may add a little bit of weight, but not much.
Length of the model Ė 510mm
Max body diameter Ė 41.6 mm (BT-60)
The total empty model weight without a recovery baffle and a parachute/strummer - 9 grams.
This is a very brief description to give you an idea. I would appreciate your comments and questions.