HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Feb 09, 2013, 04:34 AM
Jim in the Desert
cloud_9's Avatar
United States, NM, Las Cruces
Joined Aug 2007
1,263 Posts
Discussion
Size at which gas becomes practical

I have flown electric, a little, and want to move to big planes, and planes that sound good (the nitro club trainer I'm training on is more fun than electrics). I plan on slow sport flying, no racing, 3D, or pattern etc.

After some reading, seems like bigger + IC = gas, but only for big planes where the extra weight is not a problem. However, I am really fuzzy on HOW big.

How big a sport plane do you need to build so that gas is a better choice than nitro? Would a 110" wingspan Cub, SIG Four Star (correction: sorry, I found out the 125 FS has 81" wingspan), or SIG Rascal, be suitable for gas? Or are they still in the "nitro is better" size?

Thanks.
cloud_9 is offline Find More Posts by cloud_9
RCG Plus Member
Last edited by cloud_9; Feb 09, 2013 at 12:46 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 09, 2013, 06:32 AM
Registered User
earlwb's Avatar
USA, TX, Grapevine
Joined Dec 2008
13,174 Posts
The minimum size has been clouded somewhat at present. We now have working 9cc and 10cc gasoline spark ignition engines that work with the .40 to .50 glow engine sized airplanes. Before then it was 15cc and 17cc gas engines that work in .60 size glow engine powered airplanes.

But it still depends on your preferences though, glow engines are still good to use, as are gas engines and electrics too.
earlwb is online now Find More Posts by earlwb
RCG Plus Member
Latest blog entry: My new Gaui X5 Rc Helicopter
Reply With Quote
Old Feb 09, 2013, 07:13 AM
Registered User
gene6029's Avatar
Wilson NC 27896
Joined Apr 2009
762 Posts
I think alot depends on how much you fly. Gasoline is close to $4.00 (plus oil)a gallon around here right now & glow fuel is approx $15 a gallon. So if you fly 10 gallons a year, you may want to go the gas rout. Alot of the guys are flying that new evolution 10cc gas motor in smaller models & it has me thinking of trying one myself. They are easy starting & so far from what i've seen problem free. I like the sound also. There is a good selection today of gas motors for just about every type & size model out there. We have guys flying 50cc size airplanes on electric too at our field. The sound of a gas motor still does it for me though...Gene
gene6029 is offline Find More Posts by gene6029
Reply With Quote
Old Feb 09, 2013, 08:39 AM
Jim in the Desert
cloud_9's Avatar
United States, NM, Las Cruces
Joined Aug 2007
1,263 Posts
Quote:
Originally Posted by gene6029 View Post
I think alot depends on how much you fly. Gasoline is close to $4.00 (plus oil)a gallon around here right now & glow fuel is approx $15 a gallon. So if you fly 10 gallons a year, you may want to go the gas rout. Alot of the guys are flying that new evolution 10cc gas motor in smaller models & it has me thinking of trying one myself. They are easy starting & so far from what i've seen problem free. I like the sound also. There is a good selection today of gas motors for just about every type & size model out there. We have guys flying 50cc size airplanes on electric too at our field. The sound of a gas motor still does it for me though...Gene
Thanks guys. Gene, my thinking from the reading I've done is that you have an extra battery with gas that adds weight. Also gas has less power per displacement, or per engine weight, so you have to put in a heavier motor for the same power.

Thus, the extra weight is going to be a problem unless you are into a big plane. You examples of small gas motors makes me thing my impressions may not be right?

Jim
cloud_9 is offline Find More Posts by cloud_9
RCG Plus Member
Latest blog entry: Drill Sizes
Reply With Quote
Old Feb 09, 2013, 08:46 AM
Illegitimi non carborundum
grosbeak's Avatar
Canada, ON, Ottawa
Joined Mar 2011
1,281 Posts
Quote:
Originally Posted by cloud_9 View Post
Thanks guys. Gene, my thinking from the reading I've done is that you have an extra battery with gas that adds weight. Also gas has less power per displacement, or per engine weight, so you have to put in a heavier motor for the same power.

Thus, the extra weight is going to be a problem unless you are into a big plane. You examples of small gas motors makes me thing my impressions may not be right?

Jim
If I understand correctly, a battery elimination circuit (BEC) will allow you to power the receiver and ignition off a single battery.
grosbeak is online now Find More Posts by grosbeak
Reply With Quote
Old Feb 09, 2013, 09:05 AM
Registered User
United States, SD
Joined Aug 2010
1,069 Posts
So to answer your question. A Sig Rascal 110 (or similar) would be fantastic with a gasser in it.
Kyler1 is offline Find More Posts by Kyler1
Reply With Quote
Old Feb 09, 2013, 09:14 AM
Registered User
gene6029's Avatar
Wilson NC 27896
Joined Apr 2009
762 Posts
I just looked up the total weight of my OS 55AX & its 18.52oz.( with muffler) I looked up the total weight of the Evolution 10cc gas motor & its listed as 22oz. ( muffler & ignition ) included. I guess the weight of a 2 cell battery for the ignition should be factored in. So its seems you are correct with the extra weight. On the few models i have seen flying so far, ( models in the 56"-60" ws ) it doesnt seem to have hurt them much. I build & fly Vintage models & these small gas motors look attractive to me because it allows me more flxability in being able to finish them with out haveing to fuel proof them. Most of the radio gear back then was heavier too, so the extra few ounces of weight for me is negligable since our new radio gear weighs less. I dont own one yet, but im eyeing up one of those 10cc motors for my next vintage model....Gene
gene6029 is offline Find More Posts by gene6029
Reply With Quote
Old Feb 09, 2013, 09:57 AM
Registered User
Jacksonville Fla.
Joined Mar 2007
2,216 Posts
I have been flying gas now for about 4 years...bigger aiaplanes true...but I just don't see me ever going back to glow unless it's to teach
jetmech05 is offline Find More Posts by jetmech05
Reply With Quote
Old Feb 09, 2013, 10:53 AM
Registered User
United States, WI, Slinger
Joined Mar 2006
545 Posts
Quote:
Originally Posted by grosbeak View Post
If I understand correctly, a battery elimination circuit (BEC) will allow you to power the receiver and ignition off a single battery.
It's generally not recommended because of possible interference problems.


Mike
MikeCr is offline Find More Posts by MikeCr
Reply With Quote
Old Feb 09, 2013, 12:48 PM
Jim in the Desert
cloud_9's Avatar
United States, NM, Las Cruces
Joined Aug 2007
1,263 Posts
Quote:
Originally Posted by gene6029 View Post
I just looked up the total weight of my OS 55AX & its 18.52oz.( with muffler) I looked up the total weight of the Evolution 10cc gas motor & its listed as 22oz. ( muffler & ignition ) included. I guess the weight of a 2 cell battery for the ignition should be factored in. So its seems you are correct with the extra weight. On the few models i have seen flying so far, ( models in the 56"-60" ws ) it doesnt seem to have hurt them much. I build & fly Vintage models & these small gas motors look attractive to me because it allows me more flxability in being able to finish them with out haveing to fuel proof them. Most of the radio gear back then was heavier too, so the extra few ounces of weight for me is negligable since our new radio gear weighs less. I dont own one yet, but im eyeing up one of those 10cc motors for my next vintage model....Gene
Thanks Gene. Well, my motivation is cost of fuel, but even more, flying time. Apparently the nitro motors go through a lot more fuel than the gas ones. So that is a weight factor in the other direction. I need to hear them myself but reading suggests the gas motors sound more like gas motors

Jim
cloud_9 is offline Find More Posts by cloud_9
RCG Plus Member
Latest blog entry: Drill Sizes
Reply With Quote
Old Feb 09, 2013, 12:49 PM
Jim in the Desert
cloud_9's Avatar
United States, NM, Las Cruces
Joined Aug 2007
1,263 Posts
Quote:
Originally Posted by jetmech05 View Post
I have been flying gas now for about 4 years...bigger aiaplanes true...but I just don't see me ever going back to glow unless it's to teach
Why?
cloud_9 is offline Find More Posts by cloud_9
RCG Plus Member
Latest blog entry: Drill Sizes
Reply With Quote
Old Feb 09, 2013, 12:49 PM
Jim in the Desert
cloud_9's Avatar
United States, NM, Las Cruces
Joined Aug 2007
1,263 Posts
Quote:
Originally Posted by MikeCr View Post
It's generally not recommended because of possible interference problems.


Mike
Mike, do you know how much extra weight comes with the extra battery and ignition system for the gassers? Does that include a coil?

Thanks...
cloud_9 is offline Find More Posts by cloud_9
RCG Plus Member
Latest blog entry: Drill Sizes
Reply With Quote
Old Feb 09, 2013, 01:41 PM
Registered User
gene6029's Avatar
Wilson NC 27896
Joined Apr 2009
762 Posts
Jim, a 2 cell Li-ion pack that i use for all my ignitions on all my gassers weighs an additional 3 oz. That said, The 10cc gas motor i referred to in my post at 22oz should include the extra 3 oz for the ignition battery. Thats the motor, muffler,ignition, and battery. You should also put the ignition on its own switch so add that in. Roughly 25 oz vs 18.5 oz for the 55AX glow motor.....Gene
gene6029 is offline Find More Posts by gene6029
Reply With Quote
Old Feb 09, 2013, 02:04 PM
Registered User
United States, WI, Slinger
Joined Mar 2006
545 Posts
Quote:
Originally Posted by cloud_9 View Post
Why?
I don't want to answer for jet but for me it's simple. Glow sucks! Seriously though for me, glow had it's time and place and now it's done. I am now back to exclusively electric, having sold my 1/3 scale Spacewalker last fall. Liked the airplane and the gas engine on it but for right now it's just too big of an airplane to haul around and store. If I did go back to a really big airplane it would be gas. I'm building a Sig Astro Hog, it will be electric but I was seriously considering the new Evolution 60 gasser.

To answer the question of ignition battery, it doesn't have to add much weight. On my Spacewalker I was using a 4 cell NiCd 1400mAH pack for the ignition which would last all afternoon. You could get by with a smaller pack and/or different chemistry and save even more weight.

As far as fuel cost between gas and glow goes, there's more to it than the cost of the fuel. A gas engine does use much less fuel per flight than a glow engine. My Spacewalker with a 50cc gas engine would fly for half an hour on 20oz. of fuel. A glow engine of the same power would have used twice as much fuel for half the flight time.


Mike
MikeCr is offline Find More Posts by MikeCr
Reply With Quote
Old Feb 09, 2013, 08:07 PM
Registered User
Jacksonville Fla.
Joined Mar 2007
2,216 Posts
Gas is cheaper, cleaner, and to me more power...when's the last time you have seen a glow stand on its tail and climb until power is pulled off.
jetmech05 is offline Find More Posts by jetmech05
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion which gas engine for the Hanger9 Twist60? Coldfinger 3D / Fun Fly Fuel Planes 3 Jan 22, 2013 06:06 PM
Found (WTB) 550 class size heli for practice (FBL only) Paypal ready! Boomkidd Aircraft - Electric - Helis (FS/W) 1 Jan 14, 2013 10:53 PM
Sold Three 41cc Gas Engines for sale at one price !!! $150 takes all three ! shooboy Aircraft - Fuel - Engines and Accessories (FS/W) 0 Jan 04, 2013 05:34 PM
A bad practice that should be nipped before becoming popular! WJ Birmingham Batteries and Chargers 17 Aug 28, 2005 12:38 PM