Hello,
I have recently purchased a Chris foss WOT 4 classic. I am about a quarter way through the build and have a few questions. Will a 9oz tank be big enough for an OS 40LA and will t give me much time in the air,or should I fit an 110z SLEC tank?
Also,how will i cut the grp cowl?i cant imagine a scissors or coping saw doing it any good.

Any suggestions?

Thanks in advance,
Hakko

While I am not familiar with the kit, I believe I can answer your questions.

A 9 0z tank should be plenty for a 40 LA. I would say you should reasonably expect flight times of 15 (or more) minutes flying normally (1/2 - 2/3 throttle).

FIRST, Put tape over the area to be cut to prevent chipping of the gel coat.

For the cowl, a Dremel with a cut off wheel is probably the way to go for mating to the fuselage. For any additional holes, make sure you tape the area to be cut, then drill it out in stages - 1/16", 3/32" and so on. GRP is nice stuff, but the gel coat is very brittle.

If the cylinder head/muffler needs to protrude from the cowl, I suggest a series of SMALL holes spaced closely together (perhaps 3/32" dia. holes ) just inside the diameter you want. Then cut the area between the holes by going over it multiple times with a #11 blade. Finish up with 220 to smooth everything and then 400 and 600 to remove any scratches the 220 may have left.

Hope this is of some help.