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Engine for 1/4 Midget Mustang?

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Old 02-14-2007, 12:35 PM
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mmattockx
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Default Engine for 1/4 Midget Mustang?

I have the short kit for Eureka Aircraft's 1/4 Midget Mustang racer:

http://www.eurekaaircraft.com/airplanes/mustang.htm

I was planning on using a TT 36Pro for power, but now that I have had a good look at the kit, it seems very small for that engine. It is listed for 15-25 engines and the TT36 is the same weight as most 25's, so am I worrying for nothing or is there a better choice that will suit the airframe better? I have to buy an engine for this one, so I can make other choices at this time.

Thanks,
Mark
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Old 02-14-2007, 03:25 PM
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rmenke
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Default RE: Engine for 1/4 Midget Mustang?

Matt:

The tt 36 with a nelson or jett pipe will be ok for sport flying which is apparently what you are up to. If you want a very sweet sport engine that will crank when you want and also idle with the best, spend the money and buy a Jett 35. Mine is still getting better each year after 4 seasons of club raceing. Took the guys 4 years to come up with something to beat this little wonder, and then only by one point for the year, and the math was little strange. ENJOY
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Old 02-14-2007, 07:54 PM
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Default RE: Engine for 1/4 Midget Mustang?

I thought that was a Midget Mustang. Its a little P-51 right? Wait until the kit arrives and size it up from their?
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Old 02-14-2007, 09:02 PM
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Default RE: Engine for 1/4 Midget Mustang?

I thought that was a Midget Mustang. Its a little P-51 right?
Sometimes it's hard to tell if people are kidding or ..............not.

The midget racer designed for Goodyear racing in 1947 by David Long (an engineer for Piper aircraft), sometimes know as the Long Midget Mustang. The design is still available as a homebuilt.

But what he has is a Mustang model originally designed for 1/4 midget racing.

Not yet confusing enough yet.
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Old 02-14-2007, 11:26 PM
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Default RE: Engine for 1/4 Midget Mustang?


ORIGINAL: Cyclic Hardover

I thought that was a Midget Mustang. Its a little P-51 right? Wait until the kit arrives and size it up from their?
Yes, it is a P-51 Mustang for 1/4 Midget racing. I got the kit and that is what has me wondering. I was planning on the TT36 until I sized up the plane. It is pretty small, not much bigger than the Wild Hare LR-1. My concern is mostly balancing, since the engine has a throttle and I know how to use the left stick (it has more than two positions??!). Any thoughts on a smaller, lighter 25 that would better suit this airframe? Otherwise, I will just put the 36 in and deal with the balancing issues...

Thanks,
Mark
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Old 02-14-2007, 11:50 PM
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Default RE: Engine for 1/4 Midget Mustang?

The engines that originally went into those models weighed about 6 oz. Maybe you could find a .21 which is also very light, but very powerful like the car engines. At any rate, if you get a good rev'n engine in it, it will go pretty fast. With a Nelson .15 they would go in around 130.
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Old 02-15-2007, 12:00 AM
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Default RE: Engine for 1/4 Midget Mustang?


ORIGINAL: HighPlains

The engines that originally went into those models weighed about 6 oz. Maybe you could find a .21 which is also very light, but very powerful like the car engines. At any rate, if you get a good rev'n engine in it, it will go pretty fast. With a Nelson .15 they would go in around 130.
That's what I was afraid of... I will have to look at moving the firewall back a bit to help with the balance and the battery in the tail as far back as it will go.

Anything much over 100mph will seem wild with this tiny airframe. Should be a hoot!


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Old 02-15-2007, 12:20 AM
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Default RE: Engine for 1/4 Midget Mustang?

How about the OS .15CVA. I have one and thats a healthy little booger
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Old 02-15-2007, 12:40 AM
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Default RE: Engine for 1/4 Midget Mustang?

If I remember correctly, the Mexicans used to fly them (1/4 midget) in the Mexico City area with racing .40's (way back in the 70's or 80's). They were above 7500 feet, so they need slightly more power. However their setups must have been ballistic. An X-40 weighs 12 oz., so a TT .36 is in that range. I don't know if it rev's well, but I have seen the OS .32 on a 7" diameter prop and it sounded good.
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Old 02-15-2007, 09:52 AM
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Default RE: Engine for 1/4 Midget Mustang?

According to Bob Brassell (Jett Engineering), the TT36Pro will turn an APC 8x7 in the neighborhood of 16-17,000rpm on the ground and then unloads another 1200-1500rpm in the air using a Jett Thrust muffler. On such a small plane that should be pretty crazy...

I fly at 4150ft, so I have some of the same alitiude problems, just not as bad. I will take a harder look at the plans and lay some components on it to eyeball everything before I commit to an engine choice.

Thanks for the help,
Mark
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Old 02-15-2007, 01:43 PM
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Default RE: Engine for 1/4 Midget Mustang?

You should be able to run a smaller diameter prop, QM 15's ran on 7" (when props were stock) and smaller later.

Moving the engine back would help with the balance. You can also remove the leading edge sweep or move the wing forward.

Since you live at a higher altitude, you might want to consider increasing the size of the wing for more area. Something around 350 to 400, to compesate for the extra weight. Also increase the tail the same percentage. If you run a larger diameter prop, it requires a larger vertical area to maintain stability. Racing airplanes are usually designed with small props in mind.
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Old 02-15-2007, 02:39 PM
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Default RE: Engine for 1/4 Midget Mustang?

Wing changes will be a PITA because it has a foam core wing. I will look the plans over and just expect to move the firewall back and generally work at keeping it from getting nose heavy with all the construction I do.

I will look at maybe cutting down a Q500 or other APC racing prop to keep the pitch up and diameter down around 7".


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Old 02-15-2007, 03:43 PM
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Default RE: Engine for 1/4 Midget Mustang?

Big wingtips. Really big wingtips!
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Old 02-15-2007, 04:30 PM
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Default RE: Engine for 1/4 Midget Mustang?


ORIGINAL: HighPlains

Big wingtips. Really big wingtips!
LMAO!

I can actually do this somewhat, maybe an extra 1"-1.5" each side with some balsa. That is a significant increase in span for a 40" span model...As a bonus it should take high g turns better this way, too.


Thanks,
Mark
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Old 02-16-2007, 02:11 PM
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Default RE: Engine for 1/4 Midget Mustang?


ORIGINAL: HighPlains

Big wingtips. Really big wingtips!
That was what we did when a few of us played with turning QM15 planes into QM40 planes.

Btw... for any of the older QM15 planes, and good 25-35 size engine will work great. Quite a few planes flying like that that I know of.

Do not go larger than the "OS 32" size engines though... weight will be impossible to offset.

Bob
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Old 02-16-2007, 05:09 PM
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Default RE: Engine for 1/4 Midget Mustang?

Hi!
We used to race 1/4 midget pylon in the seventies and eighties over ere in Sweden. First we used .15 engines like Rossi and COX conquests, later in the eighties we went to .21 engines like K&B .21, OS .21FSR and Rossi .21 with pipes.
A good .15 engine like a Nelson or a slighly more powerfull .21 engine swinging 7x5 APC props at around 25000 rpm will make your P-51 Mustang fly at around 200km/h.
Do not.. I repeat. Do not try to fly the airplane with a heavy .36 engine! It will destroy the good flying abilities of the model.
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