sorry for the dumb question, but what, if any differnce is there in mounting a gas engine. I use tri-stock, fiberglass, and fuel proof the firewall, is there any thing else that should be done or looked at? thinking about putting a dle30 on a GP PT17 stearman

Nothing any different really. The fasteners are larger, and you typically do not have to buy a separate engine mount. Stand offs can be easily and economically made at home out of wood dowel. Most of the ARF airframes are plenty strong enough to handle the appropriate sized gas engine if the kit was originally intended for a gasser. The Stearman should be able to handle the mounting of a 30, no problem.

The question would only have been dumb had it not been asked.

Maybe one other thing though, gassers can vibrate a bit more than glow engines to I'd suggest using thread-locker on the bolts.
I also use fender washers on both sides of the firewall to better distribute any vibration load

Here is great article... penned by T.O.M... on making your own custom standoffs using dowels. It is the perfect How-to

[link=http://www.rcaer.com/pages/files/Aerovate - Engine Mounting with Wood Dowels.pdf]Engine Mounting with Wood Standoffs[/link]

Cheers
Henry

thanks guys, hopefully this will be my first gas, and I've seen so many different ways as compared to glow

Fasten it on where it don't tear off

I was having the same question, but hadn't asked yet. I really like this method and will, without question, use it to mount my first gasser to my ESM P-51B. Thanks for the link!

I know you only asked about mounting the engine but are you aware that gas requires a different fuel tubing and rubber tank stopper than nitro? There is no "pressure" tap on the exhaust but the carbs are pumped so it is not needed. You still need to vent the gas tank so it does not create a vacume in the tank.

yea, thanks, been doing research, read the sticky and it is a little vague on mounting to me, but have seen so many different ways that I was getting confused, and like Kentucky Colonel, think i like the wood dowel method link posted by Piston

With a uncowled engine, center it on the thrust line is often good enough

If cowled like an Extra or Edge, you have to use the method with the dowel

Remember when you set up the fuel tank to loop the vent line all the way to the back of tank so gas doesn't siphon out when you point the plane down, flying or not flying. Sorry but i don't have a pic to explain this.

ooook, thats something I wasn't aware of, I'll try researching that some more, thanks