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

Meerkat dopplered....177mph

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Old 01-31-2008, 03:01 PM
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Zman39
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Default Meerkat dopplered....177mph

Hey All,

I went out late afternoon yesterday to make some video attempts for sound bites so it could be Dopplered and see if my GPS readings had been close. Unfortunately, I probably only got to run about a total of 4 ounces of fuel in a total of two different flights. First flight didnt make it once around before it blew plug out. Second flight was starting to show some promise until a sheared prop in flight when the pipe started really unloading. Destroyed the Ultrathrust racing muffler, shook the firewall loose, took a little chunk out of Jett.50 crank case. Mostly fixable other than muffler, not sure of my plans there, might just put red muff back on for a while. Anyway, Mike was nice enough to do some doppler on what sound bites I had and it showed 177mph. Being that pipe never fully unloaded like other day before disaster struck, i am happy with results of 177, this plane scoots.

Ed, I was listening to you and already had some D1 props headed my way for safe factor, I just thought I could sneak in one more flight or two on sport prop. The engine must be really unloading to shear it like it did. Good news is I kept plane far enough away that no one was in real danger when it happened.

Anyway, Mike might post the doppler but hopefully it shows the plane is capable.

Thanks

Mike
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Old 01-31-2008, 03:26 PM
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Mike Connor
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Default RE: Meerkat dopplered....177mph


ORIGINAL: Zman39

Anyway, Mike might post the doppler but hopefully it shows the plane is capable.

Thanks

Mike
Mike contacted me through PM and asked for my help with Doppler readings on his plane. Regardless of results, he was willing to share the outcome with me and others. he sent me four short video clips that I analyzed. Unfortunately Murphy was at the field and got in the way before things could be tweaked for maximum speed. I think this shows this plane is quick and on a good day may actually be close to what the GPS said.

Attached is the Doppler reading and a couple of pics he sent me yesterday.
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Old 01-31-2008, 04:14 PM
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Default RE: Meerkat dopplered....177mph

Zman, that's a tough break but it shows the trouble when sport props are pushed too hard. Glad you were able to save the airplane and no one was hurt.

Could you provide the dimensions of the Meerkat, span, chord, length etc? Your design should provide a good starting place for other experimenters, since it goes like hell with a Jett 50.
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Old 01-31-2008, 04:23 PM
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Zman39
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Default RE: Meerkat dopplered....177mph


ORIGINAL: HighPlains

Zman, that's a tough break but it shows the trouble when sport props are pushed too hard. Glad you were able to save the airplane and no one was hurt.

Could you provide the dimensions of the Meerkat, span, chord, length etc? Your design should provide a good starting place for other experimenters, since it goes like hell with a Jett 50.

I sure will. I will take some pics tonight with dimensions, May have to pretty it back up a touch real quick from the carnage.
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Old 01-31-2008, 04:39 PM
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ChrisAttebery
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Default RE: Meerkat dopplered....177mph

I'm trying to capture the plans in TurboCAD for Ron right now. I'm doing it at work in my free moments, so it might take a week or two. Once I get it captured and Ron gives me the OK I'll post them at the PB website and here if he'll let me.

Here are some dimensions:
WS 42"
Chord 9"

Fuse L 28.75"
Fuse W 2.25"
Fuse H 2.75"

H stab W 14"
Ele W 12"
Ele cord 1"
V stab H 5"

BTW: Great job Mike. I've been watching this progress since Ron first posted it and now you're making me want one too.


Chris

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Old 01-31-2008, 06:10 PM
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Default RE: Meerkat dopplered....177mph

Got to see the initial two trys. You must have blown the motor after I left. It does scoot for sure. Good job.
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Old 01-31-2008, 06:22 PM
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Zman39
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Default RE: Meerkat dopplered....177mph

Here are some pics. Chris' dimensions are pretty close so I will leave it there, especially if he is putting it to plans. I also included a pic of root of wing. You will see where the thickess part of wing is. The wing is foam core and then fully sheeted and glassed in middle. The thickess part of wing is 1". The hatch right behind wing saddle is where two standard size servos rest, then pushrod to back for rudd and elevator. The battery is as far back in fuse as possible for balance. The plane as it is is a touch nose heavy but landings are not bad. However the best landing I have had to date was yesterday when the muffler got sheared off and the balance was perfect, it floated forever . The front house's a 6oz bubble less tank which is important for consistent runs, especially if you plan to push the plane to the max at high rpms. My GPS sits between the throttle servo and rear of wing, barely! Let me know if you have any more questions.

Z
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Old 01-31-2008, 06:25 PM
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Default RE: Meerkat dopplered....177mph


ORIGINAL: Sniper.308

Got to see the initial two trys. You must have blown the motor after I left. It does scoot for sure. Good job.
No blown motor thank goodness. The try you saw blew the plug out. then the next try I had it to lean. After you left is when we got it right but as soon as it started to unload, it slung a blade and took out muffler and a piece of crankcase that I can do without. Thanks for the glue!!! LOL
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Old 01-31-2008, 07:28 PM
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Default RE: Meerkat dopplered....177mph

Only an 18 oz wing loading! An even smaller airframe is still reasonable.[X(]
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Old 01-31-2008, 08:33 PM
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rmenke
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Default RE: Meerkat dopplered....177mph

HP

I have cut the Q-500 wing down to 40" with no noticable skidding in the turns, no landing problems as to excessive speed at 3.75lbs, Jett 60LX powered, scary fast even for a old salt. For some reason, a carbon fiber 52" wing by "Apex" seems just as fast with a little fatter fuse. Don't know what the airfoil is or was. Wings are given to me by club gang when the fuse goes to that great home in the sky. Must still have 3 or 4, but none given in the past several years. Must learn to be more humbe when passing their full out racers. ENJOY
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Old 01-31-2008, 08:51 PM
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freakingfast
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Default RE: Meerkat dopplered....177mph

I once thrown a blade on a 9X9 APC sport prop on my Diamond Dust too. I made an ungodly noise but no damage. I inspect it before every flight around the blade root for white marks, the sign that there's a problem. If I think it's been bumped on landing I toss it and install another. A pylon prop would be safer but I haven't found one as good as the 9X9 for hook up and acceleration after tight turns.
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Old 01-31-2008, 08:52 PM
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Default RE: Meerkat dopplered....177mph

Rog, how come you weren't racing back in the 90's when I was living in Ca? I did a lot of contests in the central valley, and especially Merced.
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Old 01-31-2008, 11:56 PM
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Default RE: Meerkat dopplered....177mph

....oh dear, more APC thrown blades. [X(]

FBD. []
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Old 02-01-2008, 08:32 AM
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Default RE: Meerkat dopplered....177mph

what rpm did you get in the air?
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Old 02-01-2008, 08:40 AM
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Default RE: Meerkat dopplered....177mph

I am not sure if Mike or Bob can take a stab at rpms through doppler sounds but static on ground was 19500 but the unload (never quite got there on this flight) sounds harmonic so much more than 19500.
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Old 02-01-2008, 09:24 AM
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Default RE: Meerkat dopplered....177mph

That was a sport prop Dave, they are not recommended at the rpms that Zman was turning.

The APC props that had issues were the Q40 Black props turning well over 26k, which have since been replaced with heavier hubs and blades which seems to have solved the problem.

I would love to see a Master Airscrew at 26k, I don't think it would make it
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Old 02-01-2008, 09:44 AM
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Default RE: Meerkat dopplered....177mph

Correct, The big disappointment was the D1 props showed up the next day, one day too late . Oh well, other than the UTR pipe, all is back together, now I just need to see if I can find a prop that the regular Jett red muffler will possibly give me similar performance at the lower rpm band of the red muffler. If not, I will just stick with it and have fun with a still fast airplane or buy another ss or UTR pipe and get it back to the speed zone..................with a D1 prop .

Z
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Old 02-01-2008, 11:23 AM
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Default RE: Meerkat dopplered....177mph


Mike, thanks for posting the information .... it was great to see the videos, and I am pleased Mike was able to extract some decent Doppler info.

This has been a fun project.... shows what can be done if someone "builds" an airplane for the extreme speed purpose

Also, provides a great illustration of why using the right prop is important.

A refreshing change from the postings of "how do I get my fat ARF cow to 150 mph" [&:]
But then again, that is a challenge all itself.
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Old 02-01-2008, 11:51 AM
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Mike Connor
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Default RE: Meerkat dopplered....177mph

In flight RPM can be obtained from Doppler. Supercoolprops website shows the procedure using an oscilloscope but I am confused on what #'s to use in WaveosScope. The WaveosScope website does not discuss RPM. Would one of the # crunchers please step forward and help?
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Old 02-01-2008, 12:07 PM
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Mike Connor
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Default RE: Meerkat dopplered....177mph


ORIGINAL: bob27s


... and I am pleased Mike was able to extract some decent Doppler info...
I have had easier videos to work with. I finally ended up using short sound clips of just before and after the the camera pass to get fairly clean lines. Speed ranged from 150+ mph through the 176+ mph posted on four passes. I understand the day of the GPS flight there were winds of around 10 mph so that should be considered. The winds during the Doppler flight were light.
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Old 02-01-2008, 02:45 PM
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Default RE: Meerkat dopplered....177mph


ORIGINAL: daven

I would love to see a Master Airscrew at 26k, I don't think it would make it
....there's only one guy dumb enough to try that around here. [X(]

FBD.
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Old 02-01-2008, 03:50 PM
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Mike Connor
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Default RE: Meerkat dopplered....177mph


ORIGINAL: Flyboy Dave


ORIGINAL: daven

I would love to see a Master Airscrew at 26k, I don't think it would make it
....there's only one guy dumb enough to try that around here. [X(]

FBD.
I wonder if we could get Mythbusters to take on APC vs MAS.
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Old 02-04-2008, 12:44 AM
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Default RE: Meerkat dopplered....177mph

My problem is the Fgoing and Fcoming #'s I am using come up with a RPM that could not be close. Plus the "F" #'s have different values depending on where I sample the speed in WaveosScope.

Here are the Doppler equations.
To get the RPM in the air, we have
f = 2 / (1 / Fgoing + 1 / Fcoming)
and
RPM = f * 60

The question is can I get the Fgoing and Fcoming from the charts below. They are the same chart using a different area to come up with a similar speed
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Old 02-04-2008, 01:02 AM
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Default RE: Meerkat dopplered....177mph

Sorry Mike, I didn't realize that you were asking about the formula.

It's fairly basic in what it is saying. 1/Frequency gives the period in time between cycles. So the time interval of the signals coming and going are being added together, then converted back to the frequency (divided by 2). Then the conversion back to rpm.

A plane doing around 170 will have a doppler shift of about 23%, throw in the unload on top of that, and you will have a pretty big number when the airplane is flying toward you.
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Old 02-04-2008, 01:24 AM
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Default RE: Meerkat dopplered....177mph

Ok, a quick example.

Say that the oncoming rpm is measured at 26,000 and the going away is 16,000. So one might think that the actual rpm would be the average of the two or (26,000 + 16,0000)/2 = 21,000. But this is not correct.

The actual rpm by the formula would be 19,810.

Another formula is 2x((R1xR2)/(R1+R2)) with R1 the approach rpm, and R2 the away rpm.
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