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

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Old 09-18-2009, 10:02 PM
  #1  
zero-cool
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so i have a viper that i clipped the wing to 40in.put on a sj50 with ss muffler and a 8.5x7.25 prop I have not flown this set up before.what kind of speed do you think i will see out of this bird?
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Old 09-19-2009, 01:24 AM
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Default RE: viper

That sounds like a good starting point. If you go back a few pages there is a thread titled Cheap Speed [or something similar] that has prop choices listed. APC is a pretty special company to have so many choices.
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Old 09-19-2009, 09:12 AM
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Default RE: viper

Not long ago a similar setup, except for the black muffler and different prop (8x?), hit speeds of over 180 as I remember. Your setup will probably be slower then that. My guess would be 140 or 150 mph. Get a recording and we can Doppler it.
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Old 09-19-2009, 09:28 AM
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Default RE: viper

the SS muffer is tuneed for higher revs the the SJ muffler but I would used a little more pitch. 8x8 or 8.5x8
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Old 09-19-2009, 11:13 AM
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Default RE: viper

If he hasn't flown the engine yet, the first prop he listed should be pretty easy on the engine.
There was a guy a couple years ago who built a Q-500 type plane with a short span wing who hit 180 or so IIRC
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Old 09-19-2009, 11:59 AM
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Default RE: viper

yup.brand new engine.I hope i can do better then 140.mabey i will clip the wings to 36in what do you think?
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Old 09-19-2009, 12:47 PM
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Default RE: viper

I wouldn't cut the wing span any more. Try what you have and play with different props.
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Old 09-19-2009, 12:57 PM
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Default RE: viper

Yeah, don't try to hit a homerun on your first trip to the plate.....it's a long ballgame. Once you get a good idea about how the plane handles, then bring some tools, a cutting board, tape, glue, etc. out to the field and see if a little trimming helps. Without someway to measure speed right then and there, it's not easy to tell which way you're heading with changes. At some point the speed won't improve, the model will just become a useless brick to try to fly and land.
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Old 09-19-2009, 04:09 PM
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Default RE: viper

Zero, did you break-in the engine on a test stand with the recommended break- in prop as per instructions before you mount it to the Viper?
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Old 09-20-2009, 10:02 AM
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Default RE: viper

the break in was done on the plane.and I just finised.was using a 8.5x7.25 then switched to a 9x8. it tached at 17,700 that seems very good to me.does that sound about right? it has the ss muffler so bob27 said i must hit 17,500 ground with the ss.im going to the field today for the first flight
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Old 09-20-2009, 10:16 AM
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Default RE: viper

zero,

what field are yo going to?

bob

I am getting my dodger ready to go, it has SS40 on it.
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Old 09-20-2009, 10:39 AM
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I cant go until later.working on my truck.are you going to the flyin pilgrams?because I also want to maidan my dd also
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Old 09-20-2009, 10:56 AM
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Default RE: viper

8.0" pitch @18k, 125mph if you are lucky

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Old 09-20-2009, 07:11 PM
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Default RE: viper

Engine must be run on the test stand first - know how it runs, learn how it runs, get 20 minutes on it ...... then fly it.

8.5x7, 8.5x7.25, 8.5x7.5, 9x7 are suitable in this configuration. 8.75x8 and 8.75x7.75 are good too.
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Old 09-21-2009, 11:57 AM
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Default RE: viper

A rossi 53 with modified exhaust & transfer timeing - JETT carb - Q500 JETT pipe - APC 8.8x9 prop - 19500rpm onthe ground = 155mph radared , wing was not cut down.
$100 viper kit $75 rcu engine = fun,fun,fun

Go for it, just watch out for the v-tail trim issues.

Go fast or go home!!!!!!!!!!!
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Old 09-21-2009, 03:48 PM
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Default RE: viper

wow! 19,500 ground!! on 8.8x9.0.thats a bunch.I also have a lr-1 that i got from from bob on this forum and a sj50 is going in it.I hope to get great speed out of that one.should be way faster then my viper.
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Old 09-21-2009, 04:09 PM
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Default RE: viper

Hey zero,

I've still got my LR-1 with a JETT 35 in it, it hauls,
Don't forget to cut for the rudder, the LR-1 needs right rudder on take off other wise it will ground loop to the left every time on take off, I have plenty of experience with this little bugger, it's a nice little plane , I think I may have a new one still in the box some where?

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