Just getting started in this wonderful hobby, I don't know how to convert from glow.40,.60,.90 etc.to gas cc.As you seee I'm green.
Thanks

I'm sure someone will come along here with a mathmatic formula, but the way I always figure it out is to remember that a .60 cu in engine equals 10 cc. So a .90 would be a 15 cc, a .30 would be a 5 cc, etc.

Thanks very much. Imprinted for sure.

[link=http://www.convertunits.com/from/cu+inch/to/cc]ci to cc conversion[/link]

this is an online converter... type in 0.90 in cu tab or 0.60 or whatever and hit convert... we also use CC in SA...

There are many other factors at play when going from Glow to Gas...

I've found that to obtain similiar performance as a 1.00 - 1.20 glow engine I need to go up to a 26cc gas engine.

The Gas engine is heavier and requires an ignition pack. This adds to the plane's weight and increases the power requirements.

On a power per displacement basis, glow does better than gas, but gas is much cheap to run... so you normally have to increase the displacement to get power equivalence when moving to gas.

You also must adjust prop sizes and pitches accordingly too.

Lots of information here and lots of great people to help you.
Don't' forget about altitude for engine efficiency if you live up in the sky like I do! I did, but I got reminded quickly.
And welcome!
Keep your wallet handy!

Agreed. A .91 size model will work with a 26cc gas engine if you can shoe-horn it in. Gas engines weigh a lot more than glow per Hp of output . . . but there comes a point it works out. If you're flying a magneto that adds weight for the flywheel and magnet/sensor, and the alternative is electroinc ignition which eliminates the flywheel and magneto but adds the weight of another 4.8v battery pack (in addition to the receiver pack, that is). But the gas carbs have their own internal fuel pump and that solves some fuel feed issues. Right around 8 or 9 pounds of model (without engine) gas comes into its own.

Gas engines turn larger props but slower. The noise is less, or at least in a lower register so it sounds better.

gas also is much more fuel efficient so you can fly with less fuel for the same duration. This largely offsets the alleged increase take off weight.

the higher weight of a gas engine is important to consider when balancing the aircraft but take off weight is what determines performance.

Gas is also less dense than Methanol; specific gravity of 0.745 average vs 0.79 average.

so compare weights, check how much fuel volume you need and you'll see take off weight difference is negligable compared to the amount of thrust available.

If you are building for gas you can also move the firewall back an inch or so if the model was designed for glow. Remember that a pound or two heavier engine up front can mean a handfull of ounces needed in the tail to balance the model. You set the C.O.G. dry so a fuel weight savings won't help you there.

Among ARFs the models with servos at the tail are just the cat's arse for gas choices.

masth formual coming up.

2.54^3= 16.387

therefore a 0.6 size or 0.6 cubic inch engine is a 0.6 x 16.387 = 9.83 cc engine in metric or 10cc for the mathematically challenged

Of course like with automotive engines the capacity is rounded up.

ah but you are missing a trick. You could move the tank aft, behind the neutral point and then you would balance with a full tank.

However, I did say that it doesnot help with balancing the aircraft, I said AUW on full tanks are closer together for the same flight time, since fuel is a considerable weight at take off.

When building an ARF for gas all these factors need to be considered. Its not just a simple matter of unbolting one engine and fitting another.


the other major thing to consider is the power delivery of gas vs methanol glow engines. Gas pretty runs at stoichiometic fuel air ratio so the throttle response tends to flatten out as the throttle is opened. with glow its more linear till WOT.
I think this is the main reason wh pilots tends to opt for a bigger gas engines than glow, especially when converting from glow to gas.

Well gentlemen I never expercted the response I received from so many people, thank you. But like any newbie I have another question. I bought an old P-51D Mustang with an advertised O.S. Max 0.45 engine the only marking I can see is OS/4BK it also has not been run for a number of years. Any ideas or suggestions.

   Okay guys one last question,

       Can you bind more than one Tx to a Rx.

    Thanks Dave

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No.

Ken

Why would you want too?

Thanks Ken, I don't  need to I just want to know if it's possible. Maybe to borrow a friend's plane
for a while.
  Thanks Dave

Yes (with Futaba, anyway). You have to turn on the Tx, then the Rx and press the "bind" button on the Rx for two seconds and release. Then cycle the receiver off and back on to make sure it truly is linked. But, until relinked it is "married" to just that one transmitter. One at a time.

You would want to because some of us have multiple models and multiple transmitters. I have duplicates on several of my planes in case I get somewhere and one Tx craps out for whatever reason - dropped, theft, switch breaks, etc.