ORIGINAL: lgodin-RCU
1. A G38 was clearly outside the manufacturers reccomended engine range. The excuse was it doesnt put out as much power as a glow 1.8. Well, a glow 1.8 doesnt have the mass and vibration of a G38, therefore the firewall absolutely needed more support than was given. I would never <ever> put a gas engine on an unpinned firewall - EVER! Even JimRoss admitted as much.
A g38 is NOT out of range for the Sig 300XS, sig recommends the FPE 2.4 ( 40cc ) engine for this plane and shows the engine being installed in the instruction manual. The g38 (38cc ) may be a few oz more in weight, but the FPE 2.4 makes 10 more lbs of thrust!
FYI: he called sig before the install of the g38 and they gave him the go ahead!
I read that post too. My only input is - think about the airplane. The printed recommendation is up to 1.8FS. We're talking about a 73.5" wingspan! While I realize the website shows an FPE 2.4, and the SIG folks said go for it, lets use a little common sense. The airplane was designed for glow - period dot - the addition of a gas engine requires a lot of modification, in this case pinning the firewall as a minimum. Think about it, Jim had epoxied triangle stock to it - even he realized he was on the ragged edge! SIG's addition of aluminum to the firewall is a clear indicator they hadnt thought it out well before the recommendation of a 40cc gasser IMO this is the one place SIG really goofed - I'd like to talk to the engineer that made the initial rec to go ahead and strap on 3lbs of vibrating mass to an unpinned/unreenforced firewall. If you think a 1.8 FS can stress the firewall as much as a 40cc gas you're fooling yourself. I stand by what I posted and we can agree to disagree.