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

I have a few questions about real speed?

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Old 11-14-2004, 06:24 PM
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somajr
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Default I have a few questions about real speed?

I built a q 400 years ago. I installed a OS 91 DF engine with a tuned pipe. I also shortened the wings by two ribs. This plane was FAST! I was sort of a menace at my local field as all of the old timers at the time were building and flying 1/4 scale Jennys. I lost this plane due to Flutter in the elevator. Now that speed seems to be in favor..I have returned to the sport. I am building a Wonder.... with a os 46 for starters.

My question is...has anyone balanced their control surfaces here to prevent flutter? It seems that I read a lot about stiffening the control rods but nothing about balancing???

Also, has anyone here installed something extreme like an OS 91 in a Diamond Dust?
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Old 11-14-2004, 07:43 PM
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daven
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Default RE: I have a few questions about real speed?

If you have tight hinges, stiff control rods, and cover the hinge line, you should not have a problem with flutter.
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Old 11-14-2004, 08:41 PM
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Default RE: I have a few questions about real speed?

You know, I just read book in my LHS last week and "part" of the solution to flutter is where you mount the hinges and the rod. Sure you may never experience it and maybe you will but the location of the whole thing is a factor. I forgot the name of those books but they are all yellow on the cover and consist of many differen topics.

Also I have seen a few here at altitude with a 25fx and it was fast. Did you consider a Webra 32?
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Old 11-15-2004, 12:29 AM
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Default RE: I have a few questions about real speed?

The hinge line has been covered- (Literally

Chuck Auger had 2 different Whiplashes (Composite delta looks like a DD) one with a Rossi-65DF engine #2 had a modified Rossi-81DF that apparently was VERY fast until he threw a blade in flight---

Others use Jett- FIRE 50's, Nelson's or the West-50 and are approaching 200MPH- I believe.... Well built with a Kevlar belly and composite everything else-- no monokote to come off.

Welcome back to speed!
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Old 11-15-2004, 03:43 AM
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Default RE: I have a few questions about real speed?

ORIGINAL: somajr
I have a few questions about real speed?
Hi somajr,

if you intend to perform 'real speed' you will be pleased with the following thread. You may want to take a close look at these aerodynamically superior designs enabling amazing speeds...

Pics: Extreme speed event in Germany

http://www.rcuniverse.com/forum/Pics...2257303/tm.htm

Mr. 'combatpigg' and Mr. 'smchale' already started with their very interesting scratch built "real" speed planes

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Old 11-15-2004, 07:05 PM
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Default RE: I have a few questions about real speed?

ORIGINAL: somajr

My question is...has anyone balanced their control surfaces here to prevent flutter? It seems that I read a lot about stiffening the control rods but nothing about balancing???
Not a prop job, but I balanced my old bandit and I am doing the same to my new one as well. you can see them in the pic (at least the little covers that go over them.

At some point, the stiffest control linkage in the owrld will not save you, the trick is to stay below that speed, UNLESS you mass balance.
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Old 11-15-2004, 10:27 PM
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Default RE: I have a few questions about real speed?

to balance a SIG Wonder witha OS.46 on the nose you will need a LOT of tail weight.

also inmprove front wing mount
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Old 11-16-2004, 03:04 AM
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Default RE: I have a few questions about real speed?

Well to start with, I have moved everything to the rear of the plane. Battery etc. This gets the CG close. I did an initial balance and it seems that it will still need a little weight. I wish that I had looked at this point sooner. I could have shortened the nose by about 2 inches...and it would have came out perfect. Oh well. I have also cut out slots forward of the ailerons and elevator so that I can add a counter balance. I will post pictures as soon as I can. Looked at that video from Germany. Impressive!!! I must say "Gutten fast!"
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Old 11-16-2004, 03:41 AM
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Default RE: I have a few questions about real speed?

ORIGINAL: somajr
I have also cut out slots forward of the ailerons and elevator so that I can add a counter balance.

That's how I did it, I molded little covers for the weights as well
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Old 11-16-2004, 10:23 AM
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Default RE: I have a few questions about real speed?

Nice work Matt.....

I did something like that with my old XLT years ago.... was tough to keep the big ailerons from buzzing. I had 1/8 oz fishing sinkers on counter balance rods, under small cover...similar to what you have. Your's looks nicer

Does make for a good point. You will notice that most speed planes (models anyway) have small control surfaces. You will also see many warnings about taking a 3D plane (big surfaces) into a full throttle dive. Design is important for intended use.
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Old 11-16-2004, 12:36 PM
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Mike Connor
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Default RE: I have a few questions about real speed?

One important thing about flutter has not been mentioned yet. The leading edge of the aileron should be at least as thick as the trailing edge of the wing it mates to. Some of the early Diamond Dust shipped with 3/16" ailerons and a 1/4" wing trailing edge. Most that pushed these to high speed experienced flutter, even with sealed gap.
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Old 11-16-2004, 08:53 PM
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somajr
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Default RE: I have a few questions about real speed?

Matt.....Very clean! I was just going to do the fishing weight at the end of a rod....at least to see if it worked.

Crazy4flight.....I also forgot to mention that I took a long look at the wimpy front wing mount on the Wonder. My plan was to beef up the dowel system a little and then incorporate a hold down from the top by bringing the fuel tank cover up and over the front of the wing. Not sure if that will be overkill but shedding a wing after a vertical dive is embarrassing right after everyone told you it was going to happen.....you know....I've done the a bunch of times before "WATCH THIS er uh OOPS, anyone got a shovel?"
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Old 11-16-2004, 09:02 PM
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Default RE: I have a few questions about real speed?

ORIGINAL: somajr
I was just going to do the fishing weight at the end of a rod....at least to see if it worked.
Just make sure you put the weight near the middle of the surface, preferably near where the control horn is. If you are not careful you can actually make the flutter tendency worse with these weights, particularly is the surface is flexible and the weight is near one end of the surface and the horn is near the other end.

The best way is to have the weight evenly distributed along the whole leading edge, but that is not really practical.

Good luck.
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