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

Viper 500

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Old 11-30-2006, 11:12 PM
  #1  
Edge 540
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Default Viper 500

I got my viper out again for some fast flying. I flew it once (maiden flight) this summer and then bacame preoccupied with other things.
Here is my setup:
46FX
9 x 8 APC prop
s3010
HS 81 for throttle

I was really impressed with the speed of this plane. After a few flights all of the club members and I have been making very rough guestimations as to the speed. 90mph 140mph who knows.

Last tuesday I put my eagle tree flight data recorder in it to find out for sure. I have used this telemetry equipment extensively and it is very accurate. I have checked the calibration. To save weight (but mostly time) I only measured airspeed, altitude and battery voltage.
Now I know I'm probably going to get some negative remarks, but after a full flight of both simulated pylon racing and all out dives for speed I clocked a maximum airspeed of 136mph out of a dive. Pretty darn impressive for an old beat up 46! My pitot tube was well out of the prop wash. I have not tacked the RPM yet.
My level flight speeds were around 110-115 and most diving passes maxed at 120-125.
I know doubting posts will follow, but that is what I got.
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Old 11-30-2006, 11:23 PM
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Flyboy Dave
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Default RE: Viper 500

....sounds fair to me....

[sm=thumbup.gif]
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Old 12-01-2006, 12:30 AM
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Julian537
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Default RE: Viper 500

sounds like the truth to me.
You may try a true pylon prop on that motor, or step down to a 9*7 and get some more RPM out of the motor.
Add a jett muffler and see what you get. Should pick up some speed!!!!!
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Old 12-01-2006, 12:54 AM
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Default RE: Viper 500

Sounds right. Put radar gun on my Viper Os 46AX,Macs Muffler,9x8 prop last weekend. Showed 121 mph level pass. I think with little more tuning and Jett muffler maybe 130.
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Old 12-01-2006, 04:03 AM
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Default RE: Viper 500

Hi everyone, i have a question if you dont mind Edge 540. Im planing on purchasing a viper 500 a couple of months later (need to save up a little first ). Im planing of using an os50sx with what ever prop it will take and also stock muffler. What speeds shall i expect out of it? Also are they ok taking of grass or does it need a tarmac runway?
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Old 12-01-2006, 11:24 AM
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Default RE: Viper 500

Your info is about on the money there.

The 424 racing set up with a good, stock TT40pro and 9x6 will get you 115-120 in level flight, so your data is about right.

Back off on the prop a bit - the 9x7 is a good stary, but try the APC 8.8x8.5 prop on your FX. Should be good for a few more MPH

Enjoy the plane!

Always good to see reasonalbe and accurate data

SKYZKING ...
If you have the OS50SX use it..... 9x8 or 9x9 prop, or 8.8x8.75 . No problem on grass. I fly all of the racing planes off grass field - just do not expect to taxi a great deal. You should see speed similar to what are being discussed here..... 110-125 or thereabouts.
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Old 12-01-2006, 11:29 AM
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vicman
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Default RE: Viper 500

135...thats it?
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Old 12-01-2006, 04:32 PM
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sigrun
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Default RE: Viper 500

ORIGINAL: Edge 540
IHere is my setup:
46FX
Did you use the FX's supplied O.S. silencer with baffle cone remaining in place?

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Old 12-01-2006, 05:08 PM
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Edge 540
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Default RE: Viper 500

The baffle was taken out a couple years ago.

skysking
I have no experience with a 50FX so I'll let someone with experience answer that. You'll like the viper. It is a very easy build. I dont really care for the wheel installation, but everything else is good. Make sure you set up both rates as specified. I found the ailerons to be too soft for my taste even at speed. Take the baffle out of that muffler and use a micro servo on throttle. Takeoffs are easy. We have a grass field but it is not a problem. There definitely wont be much taxiing going on. Have your spotter hold it while you give it throttle, give them the word and you're off to the races. Doesn’t take long to get off, and you dont have a whole lot of time to worry about it anyway. Let it climb out smoothly so you can get the RPM's up.

Be careful about stalling it on high rates. After stuffing my telemetry in there I jammed the throttle linkage. I had full throttle to half throttle... no less! A few oz of fuel never lasted so long! haha Anyway I spent the end of the flight wasting fuel for a few minutes on high rates. After a lot of cuban eights and loops I decided to test the stalling characteristics. If you bury the elevator at full throttle this thing will SNAP on you and it takes 3 or 4 spins to recover! Be careful that you dont do this on accident down low. If you stick to the recommended rates at high speed it wont be a problem. Low speed flight is great. Even when it is windy the plane cruises right through it.

If this is your first really fast plane don’t worry. It is not difficult to fly at all. Things seem a whole lot faster when you are watching someone else fly. This plane is fun!
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Old 12-01-2006, 07:09 PM
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Default RE: Viper 500

Edge 540

Can you please post the data printout from the Eagle Tree FDR from your test.

Thanks
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Old 12-01-2006, 09:25 PM
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Default RE: Viper 500

Edge 540, I've flown 3 Vipers and never experienced the snap the that you describe. I fly aggressively, with a Webra 55 screaming a 9 X 10 prop out of a dive I will slam the stick back and make very tight loop completing wings level. Some minor fuselage strengthening was done. The Viper is flown at the same rates throughout the flight. My C.G is 3 1/8" back and my throws are just short of 1/4" up & down on all surfaces with 50% expo on elevator only. The rear of the V tail mounting blocks are shimmed up 1/6". On all three planes I needed to add more than a 1/4 oz to the left wing tip. Two things I was wondering, are your ailerons sloppy ? Did you check your lateral balance?


P.S My Webra's crankshaft just snapped at the port R.I.P
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Old 12-01-2006, 09:50 PM
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Default RE: Viper 500

My webra 55 broke the crank before I even got it a plane. Strong on power but weak on cranks.
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Old 12-01-2006, 10:07 PM
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Default RE: Viper 500

I know of someone else that had the same problem. I have(had) three of these engines, this one had the least time on it and the least abuse, go figure. Maybe I'll pull the cranks and dremel the sharp edges off around the crank's port to reduce "stress risers".
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Old 12-01-2006, 10:17 PM
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Default RE: Viper 500

The wall thickness is the biggest problem. Never have encountered a crankshaft with such a thin wall thickness. Same goes for the cylinder.
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Old 12-01-2006, 10:20 PM
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Default RE: Viper 500

I have before, a Magnum 52.....It died the same way [&o]
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Old 12-01-2006, 10:32 PM
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Default RE: Viper 500

Darn. That was going to be my next project. Think I will put that one on hold.
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Old 12-01-2006, 10:59 PM
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Default RE: Viper 500

Damn... I was just about to order one of these 55's for a heli... that's the first I have heard of it. A 9x10 you say...? an APC? At what rpm were you running that thing?

Sounds like they just about reached the limit on the SPEED 40 line of engines...

About the Viper: I've only flown mine with a Jett Q500 engine. It was fast but rather twitchy on that: a little less than lowest rates advised in the manual combined with most rearward advised CG... It was very pitch sensitive. Roll rate was OK. I can't even imagine what high rates at that speed must have felt like.
I ended up shifting the CG 1/2" forward, it flies ok now. It's no competition plane, but for 150$ it's hard to beat.

For the record, I must admit I swapped the "paper" hinges for real ones (so there's no hinge gap), and I rebuilt the aileron torque rod setup (I cast them in with epoxy and microballoons).
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Old 12-02-2006, 01:37 AM
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Default RE: Viper 500

The Webra 55 turns an APC 9 X 10 @ 16,300 with a red Jett muffler on Wildcat 15/18. The engine that died had less one gallon though it. The other two have about 2 & 3 gallons on them and still strong, mounted on a standard and clipped wing Diamond Dust with the same prop size. You can run less nitro and see only a small rpm drop.
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Old 12-03-2006, 12:33 AM
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Default RE: Viper 500

65010 -
The data file is on my laptop. I'll see about posting that when I get time.

Freakingfast -
I'm not sure exactly what caused my stall although it was at high elevator rates at 3/4 throttle. I was wasting fuel doing pattern, cuban eights and such. I was way up there and tried to loop it at full rates. At the top it snapped pretty hard. I checked the lateral balance while building, but only with fingertips. The ailerons are very tight. I dont think the snap was any problem. I was on high elevator rates pulling much harder than I should have. On low rates it is perfectly fine. Compeltely my fault, not the airframe.

Rudeboy-
Elevator is very sensitive on this aircraft. I added a little bit of expo. I am at the forward limit of the CG range too.
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Old 12-04-2006, 12:13 AM
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Default RE: Viper 500

Here is a Jpeg of the chart. I left everything there including the start, engine run ups etc. I usually go in and edit out the excess but not this time. As you can see, the second half of the flight was wasting fuel at 1/2 throttle mostly.

The stalls are evident at the spikes of low speed at 505 and 515. My theory is that the first stall had the pitot tube on the outboard wing in the spin but the second stall forced a spin in the opposite direction. The first stall only slowed to 18mph but the second one was at 0. The pitot on the outboard wing would register airspeed and it was on the bottom half so flow separation would not be an issue (I think). The first stall/spin lost almost 280 feet in the process! I think it was 3 or 4 rotations to recover. I did let it build up airspeed really well before pulling out too, so it wasnt as dramatic as it appears.

My 136mph pass was out of a 630 food dive while other dives produced three other passes in excess of 130. Each was from around 480 feet and not nearly as steep. My fastest speed not immediately after a dive was around 128.

I'm not quite satisfied with the engine tuning yet. It was unloading sometimes but not others. I want to get it really dialed in and record some consistent flat line speeds.
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Old 12-04-2006, 12:30 AM
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Edge 540
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Default RE: Viper 500

I tried to make this one bigger. Not sucessfully though. Oh well.
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Old 12-04-2006, 12:51 AM
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Default RE: Viper 500

A lot of under 20' low passes LOL
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Old 12-04-2006, 12:52 AM
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Default RE: Viper 500

Yep!
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Old 12-04-2006, 01:00 AM
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Default RE: Viper 500

When I tell co-workers about us speed freaks going 200mph, video down links and on board telemetry they look at me in disbelief.... I luv it !
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Old 12-04-2006, 01:05 AM
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Edge 540
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Default RE: Viper 500

Actually, I start the plane on a bench so the initial altitude is higher than the takeoff and landings. You can even see a little spike where the spotter lifted the plane vertically over his head to check for fuel pickup. I have not yet figured out why it shows such a major decent because the bench is only 3 feet tall max. I have had this issue with my research project aircraft. The positive altitudes are very accurate, but anything negative of the initial coordinate is falsely magnified. I did not record GPS data, that flight (no room!) so I dont have a cross reference. I mase some very low passes though. Hey, if you can't go 200, 130 on the deck is the next best thing! haha
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