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Old 10-27-2019, 08:48 PM
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Smallest gas plane? looks like 73/74"

Am I wrong or does it seem like 73" is the smallest Gas plane out there? i am wondering why no one makes a smaller plane that can do gas. maybe a 65" or something. I am not sure what the smallest gas engine you can buy is? I think maybe a 15cc? wouldn't that be good for a 60ish sized plane?


maybe there is something i am missing, maybe the weight of the motor wouldn't work on a smaller plane or maybe the plane couldn't be built strong enough to take the vibrations from a gas engine, however with all the carbon now days seems it could be done.


I just think it be cool to have a smaller gas plane. I had kinda looked for a chart on say you had a Os 91 in a glow what size gas would equal that.. I have couple 40 sized glow planes it be great to convert gas one day, but again not sure them being older would hold up with a gas engine.
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Old 10-27-2019, 08:57 PM
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You kinda guessed it, the power to weight ratio becomes not great in the smaller sizes. The 10-15cc gas engines are a replacement for the 60 size glow, but they just dont make the power of the glow, have extra ignition, and vibration.
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Old 10-27-2019, 09:41 PM
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I have a Phoenix Models Edge 540. I think the wing span is 65” or 67” something like that. It has a 20cc DLE in it. Yes it was originally a glow airplane. The DLE fits nicely though. I think this is about as small as your ever going to get for a gasser.
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Old 10-28-2019, 07:42 AM
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20cc planes are about as small as you want to go when getting your feet wet with gas. Yes there are 15's out there, and they run good, but if you look they're nearly as heavy as the 20's. At that point you might just as well go with the 20 as long as you can get prop clearance. The 20's like 16 and 17" props.

For limited 3D and great sport flying, Phoenix and Seagull both have planes that work really well with 20's up front. For 3D, Pilot RC is the plan. They have a series that weigh about 7.5 lbs all up, making them state of the art. Nobody else even close.
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Old 10-28-2019, 07:47 AM
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I had a mustang with an 8cc gasser
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Old 10-28-2019, 09:40 AM
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As mentioned above, its a power to weight thing. Small gas sport and scale planes have been around forever (go to a scale contest and look at all the warbirds and Balsa USA biplanes flying on G38s and G26s) but for aerobatics gas is not really competitive at small sizes.


In addition to things mentioned above I have seen people take profile deisgns like the Mojo 65 and shoehorn DLE20s onboard. But the result was a bit heavy and underpowered compared to the glow equivalent that ran a Saito 125 back when those where popular.




To be honest, I find it amazing we have such good 35cc planes now. 15 years ago 50cc was the smallest viable entry point and it cost $2500+ to outfit one (2005 dollars) well and it still wouldn't fly as well as the bigger 35%ers....
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Old 10-28-2019, 09:49 AM
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One of the main limiting factors is the ignition box. Its about the same size for a 10cc gasser as it is for a 100+ cc. Trying to find a place to shoehorn it into a small model is a pain in the rear end!

Glo and electric power is still king of the smaller airframes.
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Old 10-28-2019, 12:11 PM
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I agree (glow and elec. plan). I spent a lot of time over the course of 3-4 seasons trying to get a 10cc engine running well enough where I could 3D it. I had the baby Evo's about as dialed in as possible, and doing real well with 13x6 props (very similar to a .55ax). Even had a couple of 5 lb planes that did REALLY well, but just not quite enough. Most that didn't know me thought I was running glow. A baby gasser that's running right sounds just like a glow engine, turning about the same rpms. These were spectacular sport planes, just not enough control over their mid range to allow the control required for 3D. Bottom line was close, but no cigar!

I may revisit when/if they start producing 10cc engines again, with a new idea when it comes to fuel calibration. That's the absolute biggest issue with getting them right. There's so little fuel being metered, nobody has it right yet.
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Old 10-28-2019, 05:53 PM
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Thanks guys, I did hear about a new possible 70" Plane coming that might be able to go Gas with like a 20cc. I will be looking out for more info on that one.

I am just loving this gas stuff so much even tho ive had a lil engine issues. still nice to fill up and fly for 8-10 mins and not even have to think about landing if you don't want to yet.. my electrics i love them but those 4-5 min flights really suck..
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Old 10-28-2019, 06:47 PM
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I have the 70in T-clips with a Saito FG-14 and pulls it around nicely...
slower acceleration but more torque
Regards,
Patricio
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Old 11-07-2019, 03:55 PM
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I resurrecting an old Astro Hog and trying to install the new RCGF 15cc hoping for the best. LOL It been a real challenge for me to make a decision on each step of the operation since it been years for me at building. It would have been a lot easier to build from a new kit. Yes the motor seems to be heavy but I'm hoping the big wing will handle it. I built a deck above the servos (under, when upright) and hoping to use the battery to help balance it.


The future remains to be seen....


sherm
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Old 11-07-2019, 04:10 PM
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If your building, Mojo 60 or 65. I'm currently building a Mojo 60 with DLE 20 power. I believe the span on the 60 is 59 inches?
The other problem with gassers smaller then 20cc besides power to weight is many use bushings on the con rod like glow engines so they need a ton of oil like glow engines. If you can't put a 20 on it, go with glow or (Gulp) e power. (God forgive me for saying that)
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Old 11-07-2019, 04:28 PM
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RCGF has a 15cc that works pretty good, using very similar construction as their 20's. Below that though, you run into carb fuel calibration issues. As in they don't run or behave nearly as well as their 20cc+ bigger cousins. Some day, when they get that issue fixed with a new carb idea, those will be a blast to play with. Until then, I would advise anyone getting their feet wet to go 20cc minimum (15cc RCGF being the lone exception).
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Old 11-07-2019, 07:47 PM
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https://www.motionrc.com/collections...-stroke-engine
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Old 11-07-2019, 09:12 PM
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Quote:
Originally Posted by DCash View Post

It's interesting Motion has taken these on. Hope they're able to support them properly.

With this in the list of specs though:
"Machined Solid phosphor bronze conrod"
I'll be passing.....
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