Eganwp

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Hey guys,

This winter I would like to build something to really get my blood moving! Up until now the fastest plane I've had was ~110-115mph level Super Sportster 40 w/ OS 55ax on pipe.

I'm looking for a descent yet cheap setup that would break 130mph, preferrably 150mph or more. I'd prefer not to fly a delta wing or a jet and would like to fly it on a smaller glow engine. I have a GMS .47 on hand as well as an ASP .52 & OS 55ax. The ASP .52 will turn 13,800 on a 10x8 and would probably do quite well on a 9x8 prop but I'd have to see. Since they're only $49 new, I'd love to use em, but am open to anything. Or should I go with a .25 or .35 sized engine instead? I know the Nelson & Jett engines are probably at the top, but I'm not sure on their $$.

What kind of airframe/plane setup do you suggest? I may also get into pylon racing and join the local pylon racing club, but that's yet to be decided. A Quickie 500? A Q40? A Viper? Can anyone lead me in the right direction or even some intro reading I can do? I'm new to this pylon/speed stuff and appreciate any info to help!

Thanks a lot!

still4given

You are not going to get 150mph out of any of the engines you own. You might get 130 on a quickie 500 and the OS 55 with a pipe. Maybe on a Q40 airframe too.

To get 150 mph with an 8" pitch prop you need 20,000 rpm with no slippage.

combatpigg

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You should get a Q-500 plane and see what you can get out of the engines you already own. Practice doing race course laps, put in lots of time at this if you have any real ambition to win.

Eganwp

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Thanks for the advice guys. I do know my GMS .47 turns a 10x7 MAS G3 @ 15,300rpm (I realize these arent great props tho, and generally run apc) so putting a 9x8 should easily hit 16k+. Wouldn't be insanely fast, but would be okay. How is 9" of thrust on most of the Q500 airframes? Too much thrust? Can I afford to drop down to 8.5" or 8" on most Q500 planes?

Are there any cheap Q500/Q40 airframes you guys reccomend? What about the GP Viper to start with? Reason I ask is it's only $130 and in stock locally. Or is there another cheap airframe worth purchasing? How draggy is the Viper's airframe?

I might just go mess around with all my engines at home and see what they'll turn on 8-9" of diameter, assuming you guys think 8" is enough thrust to pull a Q500 airframe.

Thanks guys!

daven

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the GP viper would be perfect for the GMS .47, should be able to hit 120 mph.

9 or 10" props.

APC makes a 9 1/2" x 8 N (narrow) prop that works well on sport .46 motors.

Dave

airraptor

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on the 55 or the .47 run the Jett muffler would really help in the speed area. i would think 130-135 with the 55 and a 9x9 APC prop

vicman

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Dave gave sound advice, especially the prop. I have a few of those just for playing around, just make sure the bearings in your engine are good.
The Viper is a great into to speed planes and pylon racing. I would also recomend looking at the Viper mod thread here in RCU to beef up the trouble spots.
There are a few good Q500 kits out there too if you are up for a little building. The HoleShot by BobHH and Dave's Seeker are two that I have built and really liked.

If you are interested in set-ups and power systems that go fast take a look at the Carolina Speed Rally threads. We post the planes and how fast they went by the gun.

bob27s

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Fast ........

GMS or the OS 55 .... put a Jett muffler on it.. Props as recommended above.

For me ... The 8.8x9 pylon prop is worth trying on the OS 55. Nothing larger than a 9x7 on the GMS.


Airframe: A good Q-500 or an ARF Viper works fine. Simple, stable, fast, durable.


Faster, cut 3" off of each wing panel. Shorten the span by 6" from 52" to 48". Does not affect stabiliy - just cuts down on frontal area and wetted area.

Easy 130 mph out of this.

Eganwp

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Well here's an update for you guys! I picked up the Viper 500 airframe last night from the LHS. Looks good! I cannot wait to build this thing!

Today I went out and tested all 3 of these engines to see which one would be most appropriate for the viper. Here are the bench running results!


+20*C, 3200ft ASL, 47% humidity, 0kph wind speed, 10% Homebrew @ 20% oil @ 80/20, all engines fully tuned and running on the $15 Tower Hobbies "tuned" pipe.

OS .55ax:
9x7APC = 16,440rpm = 175.4kph
9x8APC = 16,050rpm = 195.7kph

ASP .52:
9x7APC = 16,530rpm = 176.3kph
9x8APC = 15,990rpm = 195.0kph

GMS .47: (I've already done crank mods, sleeve mods and intake/exhaust ports durations modified)
9x7APC = 16,290rpm = 173.8kph
9x8APC = 15,720rpm = 191.7kph
Exhaust from 138* to 150*
Intake from 196* to 198*




The results are interesting and was a lot of fun to do the tests. Based on these results it looks like the ASP .52 w/ a 9x8APC turning 15,990rpm will be the ticket. Of course bench running is only part of the story, and it'll be a whole new ball game once in the air. I will also end up raising the exhaust ports to 170* or so on all engines before they go in, so that should give me a few more hundred rpm's as well.

Hope this helps someone else out there! Thanks again for the replies guys!

Egan

daven

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Check out this thread for tips and tricks for the Viper.

http://www.rcuniverse.com/forum/m_7651229/tm.htm

freakingfast

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With the props you tested, I think you would be correct in that assumption. The 55 showed the best prop speed but I think it is near it's peek and wont be unloading any more in the air so that leaves the 52 ready to unwind for more speed.

A few guys have been running the 55 on the viper and found the best prop was surprisingly a 10X10???!!! The engines is not screaming so don't let sound influence your perception of speed. Advantages using the 55 in the Viper, extended run time on a small tank, lower rpm is easier on bearings, less chance of foaming the fuel so you can use a standard tank. Disadvantage, greater chance of prop strike.

Make sure you do the viper fuselage tail strength mods, blue Locktite the wing screws and loose the stock wheels.

Eganwp

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Cool thanks!


Also, Bob, I broke down last night and ordered a Jett Tuned pipe for these engines! Can't wait. I'll give you guys some #'s compared to the $15 tower pipe as I've never seen anyone post comparion numbers, just approximations.

Now I just need to find an online store (in Canada preferably) that carries 8.8x8.75 pylon props!

Cheers!

daven

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Shoot, I thought you could get apc's from Jett Engineering, but I don't see them on the website...

freakingfast

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The Tower 14.99 muffler (not really a tuned muffler, but does add power) is out of stock and may not be coming back. The Ultra Thrust is gone too. That leaves the Jett and the Evolution for compact tuned mufflers.

airraptor

My Feedback: (66)

you should see about 500-1000 more with the Jett muffler.

One thing with the tower, Jett, nelson and others of this type is that they dont add power to the engine. run the engine with open exhaust no muffler record the rpm then put these mufflers on them. If you go past that rpm then your gaining power.


I dont think you will be able to run the 10x10 on these engines with the jett pipe.

Eganwp

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10x10? I don't plan on it, just the 9x8 or 8.8x8.75 for now with the Jett. I'll update all my results if I manage to find time to get out and test them all again. If not, I'll simply be posting my ASP .52 #'s.

I was planning on running open exhaust while compiling my results on sat but ran out of daylight too quickly!

still4given

I didn't know evolution made a tuned pipe. It looks identical to the jett. I wonder if Dub makes them Horizon.

daven

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He does, just uses a different color.

airraptor

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some of these guys will know but under 19,000 the regular 9x8 prop will be fater on the course. Run one of those tooth pick props on a True pylon engine and see how hard it pulls once it reach's 22,500-23,000..............