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Old Aug 30, 2014, 07:27 AM
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SayCheeze's Avatar
United States, TN, Martin
Joined Apr 2013
757 Posts
Question
Do I have to give up

speed if I start to use gas over nitro? I've been told that if I go to gas, I'll have more or less, more torque, which will seem like loosing speed.

I have a tower hobbies .61 on my Tower Hobbies UpRoar, a ST90 on my profile plane, and a ST75 on my Ultra Stick. I'm thinking of going to gas on one of them.

Educate me on GAS -vs- Nitro... I know I'll gain flying time by doing so, but what will I give up in trade?
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Old Aug 30, 2014, 08:38 AM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
Joined Jul 2011
4,005 Posts
I can't give you an answer on gas vs glow as I don't own any gas engines.


What I can tell you is you are fast moving from "beginner" to "expert" In the mean time it sounds like you are having a ton of fun. The engine forum might have the answer you are looking for.

Ken
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Old Aug 30, 2014, 01:52 PM
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United States, TN, Martin
Joined Apr 2013
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Thanks Ken. I'll take a peek at it... Sometime's those other forums just jump over my head... I think we have 1 or 2 at the most here that are flying gas. One plane max that is. One of my bud's has put together a new "Revolver" that he's running, and breaking in GAS on.

He really likes the plane overall. Engine is still new though, and hasn't quite got broken in yet.
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Old Aug 30, 2014, 03:12 PM
Complete RC Idiot Savant
The Netherlands
Joined Nov 2009
2,751 Posts
No such thing as a "Diesel HP", a "Gas HP" or a "Nitro HP". Also no difference between an 4-stroke HP and a 2-stroke HP.

They are all the same unit of power, and as such, with the same take-off weight you should get the same performance out of the same amount of power.

Differences might be that a 1HP gasser is a bit heavier than a 1 HP Nitro burner, which might cost a bit of flight performance.
And they might peak out at different RPM's which might cause the need for a different prop.

There might be other differences of technical nature, such as Gassers needing a tighter mixture control, THUS different carb designs, Gassers tend to run hotter so in case of cowling, you might want to consider that.

But power output is power output, regardless of the nature of the powerplant....

Brgds, Bert
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Old Aug 30, 2014, 03:34 PM
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United States, TN, Martin
Joined Apr 2013
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Thanks B....

Another reason for the GAS over Nitro... I'm entertaining the thought of FPV with my UltraStick. It's a very very stable platform to use for FPV I think. It's like a powered glider due to the wing coverage. Right now it has a ST75 on it.

So I need to start reading up on FPV gear that I might consider using as well, as throwing a GAS Motor on her for extended flight time.
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Old Aug 30, 2014, 06:00 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
Joined Jul 2011
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Quote:
Originally Posted by SayCheeze View Post
Thanks B....

Another reason for the GAS over Nitro... I'm entertaining the thought of FPV with my UltraStick. It's a very very stable platform to use for FPV I think. It's like a powered glider due to the wing coverage. Right now it has a ST75 on it.

So I need to start reading up on FPV gear that I might consider using as well, as throwing a GAS Motor on her for extended flight time.
Hold on thar Nelly..... I think this might be a good time to burn the credit cards and shred the check book IMO electric might make a better platform for FPV due to the almost lack of vibration. On the other hand if a good vibration isolated camera is available it may be a moot point.

Ken
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Old Aug 30, 2014, 10:41 PM
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United States, WA, Port Angeles
Joined Dec 2009
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cheeze my man, "NO"

ok I explane, yes you give up RPM's with a gasser, ok you gain torque, so then you put on a prop with a lil higher pitch too make up for loss of RPM's and walla you are going the same speed!

but wait, here's the catch, you are burning less fuel, that is easily more obtianable for leeser moola!

an EVO 15 might work in that Ultra!
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Old Aug 31, 2014, 06:54 AM
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United States, TX, Leander
Joined Sep 2003
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I've done some 1:1 comparisons on a couple of air frames with 4-stroke glow and gas, 15cc and 20cc. I found the performance to be about the same. The main difference was the weight. My rascal 110 flys with a saito 1.20 on it. I swapped it out for a rcgf 20cc, the same as a 1.20ci. Performance was the same. I did the same on an old H9 mustang. Went from a OS .91 FS to a Evo 15cc, and again had the same performance. The difference on both was some added weight. With a saito 120 on the Rascal 110 I can throttle back and thermal that plane, also knife edge from one end of the runway to the other. I could no longer do either with a gas engine. On the mustang, it was balanced perfect and landed light, weight was less than 9 lbs. With the evo, it shouldn't have added that much more weight, if any, since I used an ibec (ignition battery eliminator circuit). The ibec powers the ignition module directly from the receiver battery saving the weight of a second battery. Yet I still had to add a little over an ounce to the tail to balance it. I didn't weigh it but also noticed it landed much heavier than I was used to.

I went back to the 120 on the Rascal and will be doing the same on the mustang a little later. The evo 15cc is a great little engine, just didn't work out for the mustang. I broke it in on a GP .60 sized ugly stick and had great performance on that one. So it will go in another plane later on.

Unless you go with a 2 cylinder gasser, you will get more vibration.
Edwin
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Old Sep 07, 2014, 06:29 AM
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Tucson
Joined Nov 2009
976 Posts
I agree with Edwin on the (about) equivalence of the small gas engines and the 4-stroke nitro engines. (But gas engines have a pumping carburetor, so are MUCH easier to tune).

I think that only your 90 size plane would be a decent conversion to gas, because gas engines are heavy, and I don't like putting them on small (< 90 size) planes. A 20cc DLE would be about the same power as the 90 nitro 2-stroke.

I don't think that you are flying speed planes. If you got 8,000 rpms out of a DLE 20cc, and used an 8 inch bite prop, then your engine is making turns for 60 mph. Is that fast enough? (8000 * (8/12)) * 60 / 5280)

If that's not fast enough, then a 10 inch bite prop will make turns for (8000 * [10/12] * 60 / 5280) 75 mph. A 12 inch bite prop will make turns for 90 mph. Just make sure to reduce the diameter of the prop, as you increase the bite.

Most of these stick planes and aerobatic planes will fly quite nicely at 40 mph, so you should have enough speed to fly them on a gas engine.
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