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

Defining speed

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Old 12-27-2005, 12:32 AM
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MishaParem
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Default Defining speed

What charecteristics of a plane's design makes it FAST? My mental picture of a plane I wish to build for speed consists of short swept back wings 40-60 inch wingspan from tip to tip. The length of this plane will be about 18 - 30 inches from tip of spinner to end of fuselage. The tail will have a V-tail constructon with swept-back fins. I'm aiming for control and speed. I'm thinking of using .36-.46 TT for the plane. I'll make the wing rather tthin with a foam core (I'll use that cheap high expansion foam from Home Depot) with balsa sheeting in the first third of the wing. I think that should work out fine. Any opinions?
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Old 12-27-2005, 12:42 AM
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Flyboy Dave
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Default RE: Defining speed

....something along these lines ?
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Old 12-27-2005, 01:16 AM
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Default RE: Defining speed

Right plane wrong size. Reduce size by 20%, add webra 36 with tuned muffler, time the exhaust to match muffler and rip.
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Old 12-27-2005, 09:04 AM
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Default RE: Defining speed

Or maybe this.....
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Old 12-27-2005, 09:21 AM
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Default RE: Defining speed

No, no. No green. This is better, gotta change the number though.
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Old 12-27-2005, 11:20 AM
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Default RE: Defining speed

Misha:

Notice the race plane pictures have little or no back sweep in them, and generally some of the best in the world! If you wnt to experiment with design, start with a developed wing such as the Q-500, or any of the formula or FAI. Someone in your club has a good Q-500 wing laying around that they should part with for little or 0.For a 36 TT, cut the wing down to 40", for the 46 keep it at 50"-52" standard lingth. Measure the moments from a Q-500 and keep yours close and a little wider for ease of installation. The Q-500 wing on a sport model works out well, on normal rates will loop, snap, etc. My little one hoversto the crowds delight after a race. Your tirtle decks do not have to be solid balsa planked, open framework for this area is strong and light. Look at a GP super sportster as a good example. You want your fuse to be as drag free as possible, spinner to cowell in motor, sleek to the tail. Consider wing fillets. Every little thing to reduce drag adds up to superior speed. ENJOY
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Old 12-27-2005, 01:41 PM
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MishaParem
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Default RE: Defining speed

hmm ok... I was just wondering does the length of the plane efffect it much? I was actually thinking about something like a Qt-500 with swept-back wings and shorter fuselage. In military aviation the planes with swept back wings were usually a bit (or quite a bit) faster than the others then delta wings came along and beat the swept back wings. I haven't done much research about wings I just associate them with planes which use them so I'm wondering why a rectangular wing might be better in this case. Also, I don't really know much about drag and the such so if anyone could refer me to a good book/ article that would be great.

I was thinking of making the fuse just long enough for a decent tank, reciever, battery, 4 servos packed as tightly as permits, and a very small compartment in the back for weights if needed.

Also, what difference in speed and control exists in a trailing engine (pusher) and a leading engine (puller?)?

Thanks!

Misha
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Old 12-27-2005, 04:04 PM
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Dave_Gherardini
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Default RE: Defining speed

"In military aviation the planes with swept back wings were usually a bit (or quite a bit) faster than the others then delta wings came along and beat the swept back wings."

Misha. the flight envelopes of these planes cannot be compared to models. Mostly sweep on models is eye candy. Unless there is no fuse, Then sweep can add stability. There are exceptions though. And thats being very simplistic in explanation.
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Old 12-29-2005, 12:34 PM
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BruceDana
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Default RE: Defining speed

Dave is correct. Airfoil and drag elimination have a lot more to with facilitating potential speed of an airframe than wing sweep, which main advantage is moving the compression wave off of the control surfaces during supersonic flight. Case in point, zero swept Dynamic Soaring sailplanes are now 300+ mph !
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Old 12-29-2005, 12:41 PM
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Default RE: Defining speed

In case you are unfamiliar with Dynamic Soaring:

http://en.wikipedia.org/wiki/Dynamic_soaring
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Old 12-29-2005, 01:59 PM
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Default RE: Defining speed

Misha, the sweep in the jets was there to delay the compressability effects of the transonic speeds those craft were operating at. Not needed at our speeds. As for fuselage length a relatively longer fuselage offers better handling up to a point. Shorter fuselage will require a comparitively larger stabilizer and fin which is more drag.
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