left seat

I have a Carl Goldberg Tiger 60 which I built from a kit. It has a 70 inch wing span and currently has an OS 61ax engine for power. It flies well but I feel it is a tad under powered and likes a fair bit of glow fuel. I'd like to swap out the engine for a gasser as this fuel is cheaper and much easier to get. I've been looking at a NGH 17cc gas engine but my concern is that its rated hp is less than the OS 61. As I've noticed there's not many gas engines out there in this size. Any ideas about any gas engines that might work with this size plane?

mgnostic

Pretty much any of the 17-20 CC engines will make .60 size power. I don't know that it will give you that much more of a perception of power but yeah, your gas miliage should be better. A couple of things to be mindful of are balance and prop clearance. A 17cc engine is going to want to spin a larger prop and the Tiger was designed such that it probably was never expected to swing more than a 12 or 13 inch prop and a 17cc gasser is going to want more prop than that. The 17cc is going to be a physically larger engine and that brings up two issues. 1. will it fit in the hole? and 2. how is it going to impact the balance of the airplane? It is often difficult to answer questions like this because one doesn't know what the original poster is up for. Since you built the airplane you will have a better idea of what you are getting into but it is still hard to know what level of advice to give.

FishBreath

Having just converted a 60 sized plane to an Evolution 15cc there are some things you need to think about.
1 Your going to have to find room for the ignition and it's battery.
2 The landing gear is going to have to be lengthened for prop clearance.
3 I placed my tank under the CG so the balance doesn't change as the fuel is consumed.
4 Things are going to get snug in the engine compartment but should work. My engine has a side mounted carb and exhaust which keeps the engine closer to the firewall.
5 place everything in their place and check the CG before mounting anything. This can save you a lot of work.
I only have one flight as of yesterday but I'm liking the gas conversion.
Purchase a small fire extinguisher and keep it with you when flying.
Be safe and I hope your conversion works well for you.

LLRCFlyer

The two previous posts are accurate concerning the conversion issues to gas from glow. A suitable gas engine setup will normally be heavier. A rule of thumb for gassers is to use the same displacement gas engine as the displacement recommended for a four cycle glow engine. It will be pretty close... i.e. a .60 2-cycle glow (10cc) = .90 4-cycle glow (15cc) = 15cc 2-cycle gas engine. A 15 cc 2-cycle gas engine should swing a 15-6 prop with authority. I have a Sig Four Star 60 (8.5 pounds) that was intended for a .60 2-cycle glow or a .90 glow four stroke. It flew very well with a Hobby King 15cc two stroke gas engine until the carburetor quit working after 17 hours of flight time and I can't get replacement parts. So I am in the process of replacing it with a RCGF Stinger 15RE. The Stinger turned the same APC 15x6 prop about 800 rpm faster on the test stand than the old Hobby King engine did. It should pull the 8.5 pound Four Star 60 vertical pretty well. The Stinger 15RE weighs 1.69 pounds, is rated at 2.4 HP, and is rated for prop sizes 13x6, 14x6, 13x8, 15x8, 15x6. The Stinger 20RE produces 2.8 HP and only weighs .06 pounds more, but it turns larger props (15x8, 16x6, 16x8, 17x6) at lower rpm The Stinger 15RE has a much higher redline of 15,000 rpm and power peaks a little above 9000 rpm. On the test stand my Stinger 15RE turned an APC 15x6 prop 9020 rpm sustained and peaked at 9190 rpm. The APC 15x6 prop tables show 11.2# thrust @ 9000 rpm. I would suggest the 15cc size in order to be able to use faster turning smaller diameter props for ground clearance... more nearly what a glow engine would do. I suspect it would do well on your Carl Goldberg Tiger 60 turning a 13x8 prop.