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

Speed secrets?

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Old 01-13-2005, 12:02 AM
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FlyerBry
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Default Speed secrets?

What are your favorite tricks for getting more speed out of an airframe besides the obvious like installing a lighter, more powerful engine? Sealing hinge gaps comes to mind as well as building light. Are there any covering tricks, etc. that you suggest that will make most any plane faster?

Is one covering lighter than the rest and therefore, better for speed planes?
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Old 01-13-2005, 12:38 AM
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Default RE: Speed secrets?

if we told you then we would have to kill you

sharp trailing edges
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Old 01-13-2005, 12:44 AM
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Default RE: Speed secrets?

If you are working with a clean design to begin with, then propellor work will net the most gain. Keep going down in diameter and up in pitch until your plane shows signs of slowing down. If you look at a competition pylon racer, C/L speed or combat plane up close, there aren't any "secrets" to what makes the airframe fast. The biggest difference in speed between similarly powered and designed ships is in the prop work.
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Old 01-13-2005, 11:52 AM
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Default RE: Speed secrets?

Cowl the motor and muffler. Retract the landing gear.

Try to eliminate as much parasite drag as you can. Probably the biggest contributor to parasite drag (other than the motor, muffler and landing gear) are the exposed linkages to control surfaces. So, enclosing your control linkages adds speed. This means using torque rods for aileron control rather than having servos mounted outboard "flapping in the breeze".

The RX switch can also be enclosed so that it doesn't protrude. The RX antenna should be routed inside the fuselage--NEVER OUTSIDE.

If there is a gap at the fuselage/wing joint, taping over the gap with what we racers call "speed tape" will help. Also tape over the heads of the wing hold-down screws.

Speaking of wing screws, these should be of the counter-sunk variety so that they sit flush with the surface of the skin. No round or--what's worse--hex headed bolts protruding to produce drag vortices.

Basically, take a critical look at your plane and try to get rid of all the little bumps.
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Old 01-13-2005, 03:53 PM
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Default RE: Speed secrets?

some good information here.

getting a 'bit more speed' from a specific project or airframe is probably more of what you may wish to know... correct?

As noted, Drag is your enemy. It takes a LOT more HP to overcome a little bit more drag. Closing up holes, retracting the gear - with GOOD, tight gear doors helps a bunch. Cowled engine as noted - with good controls on airflow through the cowl (you do not want a big old hole up front). Thin wings, sharp trailing edges help with the package. Of course a good engine and a prop correctly selected or fabricated for the aircraft makes a big difference too

Sometimes folks want to know "how can I make my Sig Kougar do 160 mph". Well...... short answer is it can't. Fat wing, lots of drag, and even with retracts and a monster engine.... its not going to happen. Just as an illustration.

If you have a specific project in mind.... let us know. Im sure folks can suggest tweeks appropriate to the project.

There is a great thread in the speed forum here on building a speed dedicated airframe. Take a look. Lots of your questions can be answered there.

Bob
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Old 01-13-2005, 07:02 PM
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Default RE: Speed secrets?

If I told, then I would have to kill this guy

ORIGINAL: Crazy4Flight

if we told you then we would have to kill you

sharp trailing edges
[>:]
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Old 01-13-2005, 07:04 PM
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Default RE: Speed secrets?

The right prop has a lot to do with it. Many think they have it mounted but they don't
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Old 01-14-2005, 11:44 PM
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Default RE: Speed secrets?

Hi Flyerbry,

Im told that cubic bucks is very handy in helping things go faster...

Carlos G
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Old 01-14-2005, 11:47 PM
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Default RE: Speed secrets?

Thanks for all the comments. I don't have a particular plane in mind. I'm mostly interested in developing good techniques that I can use no matter what the subject. These are all good ideas.

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Old 01-15-2005, 12:01 AM
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Default RE: Speed secrets?

Hi Again Flyerbry,

You might want to try a simple Quickie 500 type of plane (wood kit ) and your best .40 engine to get your feet wet. A Scat Cat flys well and is relatively cheap and easy to learn on. Try Lone Star balsa supply for the kit , they have an ad in Model Aviation. Build it light, straight and pay close attention to the details.

Then go out and have fun!

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Old 01-16-2005, 10:10 AM
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Default RE: Speed secrets?

A quickie is a good way to go fast with minimum effort. You can also leave off the landing gear and reduce wing area for even more speed. Try it at about 40" span.
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Old 01-16-2005, 02:01 PM
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Default RE: Speed secrets?

A guy I fly with occasionally has a quickie. I agree, they are simple, light and definitely haul!
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Old 01-16-2005, 02:59 PM
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Default RE: Speed secrets?

Getting back to props, one thing that the guys who are seriously into speed have in common, they use carbon props with thin blades. The other "secret" is to use a tach and temp probe to optimize the engine/pipe and prop combo. Small racing engines that are timed for tuned pipes seem to share a common trait, their exhaust durations are extreme. The timing guidelines are given at some informational websites that talk about pipe design and engine timing. I have used a die grinder with a carbide rotary file to raise the exhaust port on even unpiped combat engines with good results, of course tork and throttleability are compromized, but who cares?. Another internal trick is to remove some of the piston skirt material on the intake side of the piston, and dig out some of the excess material that is inside the piston. Removing some material from the back side of the crank throw[not the counter weight end] makes the counterweight effectively heavier and can contribute to high rpm smoothness. I also convert the standard caged bearings to a retainerless type called,"full complement", which means that there is no retainer, just more balls. These are a little bit tricky to build, but they have less drag and no way to come apart. The only other trick that comes to mind is to lap the lower portion of the liner with a brake hone, don't go any higher than the lower edge of the exhaust window. A lot of these tips are hit and miss and depend on the mechanics' judgement to know when enough is enough. Occasionally you will go too far, but if you never go too far, you will never know when enough is enough.
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Old 01-16-2005, 08:32 PM
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Default RE: Speed secrets?

ORIGINAL: Snoop Doggy Bag

If I told, then I would have to kill this guy

ORIGINAL: Crazy4Flight

if we told you then we would have to kill you

sharp trailing edges
[>:]

So then do I have to kill the people you tell ???[sm=punching.gif]
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