If an airplane calls for a 1.2 ci glow 4-cycle, is it time to seriously consider going to a gas engine? Thanx. Jim

Only if your willing to continue to 12-14.00 bucks a gallon for glow fuel instead of 2.00bucks a gal.

Jim,
In that size engine/plane class, it really depends on the type of plane the 1.20 is for and the type of performance you want. If it's for a cub or decathalon or lightly loaded plane you can get away with a small gasser but if it's an aerobat, you run the chance of having a heavily loaded plane that may not perform as expected.

marty

Afterburner,

That's not necessarily so, as there are several aerobatic planes available in the 68-75" wingspan category that can easily handle a small gasser.

My Goldberg Extra which spans 68", flies very well and has retained all of its original good flying habits with a Zenoah G23 engine which replaced the original ST G90 engine.

Though very aerobatic, it certaintly is not 3D capable, but then it was never designed for that type of flying.

Karolh,
I think you should consider yourself pretty lucky. You added almost a pound and a half of weight(assuming it is an unmodified G-23) to an airplane that is probably in the 9 to 11 pound range I'm assuming from the wingspan? For it to have retained it's good flying characteristics is suprising. Do you have to come in a little hotter than with the .90? I have a G-90 in a WM Midget Mustang. Although it runs reliably it is not a powerhouse in it's class. That was my first and last ST engine. Glad to hear you had success with that combo but I think in that size plane your positive results are in the minority.

marty

kf6gub, FWIW, I have a Taurus 2.6 42cc in a H9 232 with a 73"w/s. Can't wait till spring unless it gets real warm and that don't look promising.

You should stay with glow in that size plane unless as previously stated it is a plane with a big wing that is very forgiving, I have seen the H9 73 inch Cap with a gasser and it was a Brick. It will not last as long as it would if it was glow pwered. Why? Because it will be severly over weight and any errors on landing will end in a destroyed airplane.

Joe

I have to agree with Jim Brannon.

From both as an observer, and one who has installed a heavy engine on a smaller plane. Landing a plane with a high wing loading can be interesting. It will need to have a faster glide speed, will require a longer landing roll out, and will have a very abrupt stall when you pull the nose up to flair and slow down to land. There will be little room for error. In flight it will have the tendency of snapping out of a less than perfect loop at the top and bottom unless the loop is made with a much larger diameter. The same thing will happen in tighter turns.

I can't with any authority say where the break point should be between the glow and gas powered planes, it depends a lot on the type of plane. In aerobatic planes, I personally think the 80" wingspan area is where it should be. A smaller plane will handle it to be certain, but with how much weight above and beyond what the plane should be at, but with what negative impacts to the flight qualities.

If you have to add a lot of nose weight to balance out a plane with the recommended size glow engine, then a gasser may work out. If you are needing to add tail weight to balance, then the gasser should be out of the question.

Well guys, maybe to you it is a brick but to me and some of the fellows that have flown this plane we are all satisified with its perfromance so was the guy that bought my last.
Different strokes for different folks.

My first foray:

A 73" Creek Sukhoi SU-31, full detailed cockpit, 3.25 " Sullivan ali hub wheels (look great but heavy)

An MVVS 1.60 Gas with bisson muffler 18x8 bambula prop

1400 MAH sub c cell ignition pack (i could loose some weight here)

AUW - 13.8 pounds (it's heavy)

It flies remarkably well. No unlimited vertical, or hover capability, but plenty of power for sports aerobatics.

Very friendly stall chracteristics

I fly for a few mornings for a few cents worth of pump gas

I'd say go for it, and don't believe the nay-sayers, unless 3-D is your bag, when glow is the answer.

As you can see, there are plenty of opinions here, none of them wrong, all just based on personal experience. Mine has been very favourable and I will be trying a 35 cc MVVS gas in the 72" CMP Yak-54 I just picked up - they need the nose weight.

fiery

again for what its worth, I'm flying a SIG Su 31 with a 3.2 in it and an Aeropro Cap 231ex with a 3.7 and they all fly very well including 3D, all gas burners(Taurus)
My opinion

With the ST G90 powering my model at 9 lbs. the performance sucked and the plane was quite a floater.

Powered by the G23 with an all up dry weight of 10.5 lbs and a wing loading up from its original 24.4 to 28.6, performance is good with absolutely no bad habits and it still is a *****cat to land.