Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

pusher vee tail design suggestions

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Old 01-16-2005, 05:07 AM
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SmokeyT/A77
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Default pusher vee tail design suggestions

HI,

Do you guys have any suggestions for this design? I will be using an OS 46FX with port timing mods and pipe(w/ hook shaped header to locate inside fuselage). I am guessing an APC 10x8P or 10x7P would be best. It has a 40" span, airfoil of 15" root length (.08 thickness @ .4 back from LE). I will also use mech retracts.

I based it on the Bobcat, with the exception of using vee tail or inverted. I think the inverted vee would be neat, and also help keep the rear end more stiff

I would like to use a glassed/foam fuselage, and foam/balsa/glass wings.

Also, what should I do about cooling the engine? I wanted to cowl it in w/ a scoop (for aero) but it looks ugly that way. How much would leaving it out in the open hurt performance? I would realy like to impliment slotted or fowler flaps, but this might prevent me from making the wings removable.

What do you guys think? What kink of top speed do you think it should have?

Any and all advice/criticism welcome! This seems like the best place to come for help.

Thanks
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Old 01-16-2005, 07:43 PM
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Default RE: pusher vee tail design suggestions

They are all very handsome planes! I say build the one that you think will be the easiest to work around in the pits, and will stand up [best] to the rigors of flight and landings. Hopefully you size the airframe so that a 9x8 or 9x9 works best, you won't get a .46 to turn a 10" prop well enough to call it a speed plane.
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Old 01-17-2005, 03:31 PM
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Default RE: pusher vee tail design suggestions

Are there any pros/cons to each tail configuration? I am leaning towarts the inverted V (fig 2A above) because i believe it would make the tail stronger by joining the two booms, and also because it seems it would have better roll coupling. Has anyone seen this tail configuration before? I personally have not. Is there a reason for this?

Should i give it a go?

thanks
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Old 01-18-2005, 12:32 AM
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Default RE: pusher vee tail design suggestions

Aerosonde makes a UAV that has your type of tail configuration...here's a gallery that has a few snapshots of that plane plus other UAVs: [link=http://www.cloudcaptech.com/gallery.htm]UAV gallery[/link]

Carl
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Old 01-18-2005, 10:38 AM
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Default RE: pusher vee tail design suggestions

Looks similar to something I worked up a number of years ago. Although mine was not a V

Infact, someone else noted a pusher design like this not long ago, and I took that opportunity to dust off my old cad files. Its now on the "list" of to-build stuff sometime in the next year or so.

Configuartion lends itself to some interesting combinations. Mine was more a twin boom with a stab across. Id imagine a V-arrangement would work ok... if you can get the structure to work properly.

I am going to utilize a side cylinder mounted engine, and the turbo-jett muffler slung underneath. I sized the plane for the SJ-46. Avoided the pipe/exhaust return flow problem typical with the pusher by using the in-cowl muffler. Plus I still have the tuned exhaust. Trying to keep this an all-wood plane (possible kit) - but the temptation to put a glass center pod on it is hard to resist.

Bob
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Old 01-18-2005, 02:04 PM
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Default RE: pusher vee tail design suggestions

I think i will try the inverted v tail, just to be different!

Any suggestions on the tuned pipe? I am considering the Macs 7.5(.40-.45) or 8.5(.40-.50), but i would like to find some dimensions first and run the numbers in one of those tuned pipe calculators. As for port timing, i found a site that suggested 125 deg. intake, ~180 exhaust, and 215 for the transfer port. Have not measured the stock port timing yet, but i will probably work my way up to these numbers in increments and see what happens. Can I get 18k+ out of my 46FX safely? Is the rod strong enough?

Thanks for all your input!
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Old 01-18-2005, 03:13 PM
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Default RE: pusher vee tail design suggestions

You an get a bit more out of the engine by tweeking the ports, but not that much more. The carb bore is not there to support the mass flow. I'm not sure if the rod will hold to continous 18K + rpm, but it should. The stock bearings would definately need to be replaced.

Also, if you push up the timing, you will tend to give up any reliable midrange or idle. Its a bit of a trade-off

If you want those rpms, use the 6.5cc pipe. It has better flow properties, is lighter and a bit shorter. I would imagine 18K would be possible, with the mods and full pipe, on something along the lines of 9x7 or 8.8x8.75

If you want some simplicity, the jett-stream SS-40 muffler is tuned for the 17K - 19K power band. Just bolt it in place and prop to keep in the rpm band.

Should be a fun project.
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