The original Scale Combat class aloowed the use of a .15 if the full scale airplane used an inline engine, and you were allowed a .19 if it was a radial engined plane. The big gripe back then was that the planes were far too small - a 1/12 Mustang had little over 200 sq. in. Phil Cartier was telling me that some locals were thinking about using the Ta-52 which had a decent wingspan. I guess someone wised up to the fact that Fleet Air Arm fighters like the Fulmar were significantly larger than land-based fighters, so I started seeing pictures of these in magazines, and Mr. Clean on the CL Stunt forum mentioned that torpedo planes were also allowed (hence 500 sq. in. Avengers). I guess the lightweight .15 won't be of as much use these days, since the modified rules allow bigger engines for use, and airplanes are larger, too.

I must admit, I've never seen a Magnum .15, but comparing weights on the Just Engines web site for the ASP and on the Hobby Shack (Hobby People these days?) web site makes me think they're different engines. The ASP is small - looks like a .12 in size. Put it next to my old Super Tigre X.15s, they're tiny. The place to get info is the Just Engines web site. Nice thing about Just Engines - they'll let you order the engine with different mufflers, without the carb, etc. etc. and adjust the price accordingly.

I've used bladders for a long time (since the mid 70s) so I'd naturally want to use them. Yeah, they can burst, but if you use the right stuff, it doesn't happen very often, and not at all if you replace them periodically. The materials aren't hard to get - CL Combat suppliers have everything needed, including the syringes and fittings. To avoid blown bladders, use the "Fast Combat" sized tubing - 1/4" i.d., 1/16" wall, preferrably Phil Cartier's Yellowjacket tubing or similar. Avoid the thin walled stuff people use for 1/2-A Combat. If you don't want to worry about the inside of your bladder compartment getting soaked with fuel, enclose the bladder in a balloon - if the bladder bursts, the balloon contains the fuel. A remote needle works great - the usual advice is to find the RC needle valve assemblies for the OS Max .10FSR, since these have very fine threads. In my case, I drill and tap the intake stack on the engine for a DuBro fuel nipple and the fuel goes from the remote needle to that. It is also possible to put the fuel intake elsewhere on the crankcase (some people put the nipple on the backplate), but it makes the engine a lot more prone to flooding. I think the CL Combat column one of the recent Model Aviations was about bladder tanks.

Incidentally, bladders do tend to run rich the last 15 seconds or so of the engine run. Usually not much of a problem. One thing to avoid is "false pressure" - if your bladder compartment is too small, forcing too much fuel in the bladder results in higher than normal pressure, which leads to a lean run after some fuel is used.