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The fastest engine for a viper 500

Old 12-13-2006, 12:25 PM
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Default RE: The fastest engine for a viper 500

The name of the game is POWER TO WEIGHT AND SMALL FRONTAL AREA.
Old 12-13-2006, 01:42 PM
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Default RE: The fastest engine for a viper 500

honestly, for a Viper, just a plain TT40Pro or TT46Pro is all that is needed. Perhaps add a Jett-stream or ultra-thrust muffler to it for a few more RPM. A basic APC 9x7 prop. At 130 mph it will be the fastest plane at most flying fields.
Old 12-13-2006, 02:37 PM
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Default RE: The fastest engine for a viper 500

the guy's at are club are all ready getting 125+ with TT, and O.S. So the TT40Pro or TT46Pro just will not do. I don't want to go the same speed or an extra 10 mph. I want to blow past them and not look back!!!!.[:'(]

Has any one out there put a prop on a O.S. VX DF what size and what rps's did you get?
Old 12-13-2006, 07:29 PM
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Default RE: The fastest engine for a viper 500

Well in that case your best option really is a Nelson or Jett 428 engine.

Q500 planes are built around .40 size engines. Smaller is possible... bigger becomes a hassle in every possible way. If you want bigger, you're better off building your own plane.

You and the guys at your club will be amazed at the difference in speed between a regular sport .46 and a current racing .40. There is simple no comparison.

If you want to go faster, the Viper is not the plane you should be looking at. A 428 engine already pushes that plane to the very top edge of its performance envelope. Any faster, and things are bound to go wrong sooner or later.
Old 12-13-2006, 08:41 PM
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Default RE: The fastest engine for a viper 500

A Webra .50 with a large venturi, 9x8 prop and open header will put you in the mid 150s with a DD and be easy to tune. I would expect even more speed with a Q500 plane. I think the Webra is relatively light compared to a TT.
Old 12-14-2006, 10:15 AM
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Default RE: The fastest engine for a viper 500

Rudeboy makes a good point, and sorta follows up on what I noted....

Putting a ton of engine on a viper is a waste. It is simply not designed/built to go THAT fast.

If you are looking for speed, you want a Vortex, Bird of Prey, or one of the other "competitive" Q-500 designs, preferably with a composite wing, which are DESIGNED for 428 power. Then put an actual 428 engine on it.

Current Q-500 speeds are 170+ mph. If that is the goal, what I described is the basic formula to get there. A viper with mods and alternate engines is not going to get there.
Old 12-14-2006, 11:31 AM
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Default RE: The fastest engine for a viper 500

Forget the Quickie and go with something like this.. About the same cost as a good composite quickie but looks like a real plane and unlike most planes people talk about, is capable of the 200 mph mark with the right prop.. Couple that with it's stablity and handling, you'll blow everything out of the water with it..
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Old 12-14-2006, 11:45 AM
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Default RE: The fastest engine for a viper 500

It’s a real easy formula.

Viper with a good Nelson or JETT Q500 engine and pipe with a bubbles tank, running an APC 8.8 x 8.75, 9.0 or 8.25 on 15% will get you 155 to 165 mph. I don’t believe any other readily available engine will do it. Keep in mind at this point this is not a sport plane. By most sport flyers standards these things are scary fast and should be banned from the field. They are pretty much full throttle or nothing. If you decide to do this also be very careful with the engine. One very lean run and you need a new top end.

Good Luck
Barry
Old 12-14-2006, 12:33 PM
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Default RE: The fastest engine for a viper 500

True Barry...

I tend to guide folks away from the 428 engines for the Viper though, especially if just for sport flying. Its a good plane, flys very well, and a number of folks have been racing them in 428... but only after some 'experienced racer' checks and modifications.

The success or failure depends a great deal on the modeler setting up the plane and engine.
Old 12-14-2006, 02:10 PM
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Default RE: The fastest engine for a viper 500

Your correct Bob/Barry.. The people at the field where I fly have seen me fly these(Quickie 428 & Q-40) a hundred times but still most of them hide behind their trucks when I fire one up. Of course, that could be due more to my flying than the speed Either way, the racing engines and planes are not for the faint of heart or wallet...
Old 12-14-2006, 06:25 PM
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Default RE: The fastest engine for a viper 500


ORIGINAL: diggs_74

Forget the Quickie and go with something like this.. About the same cost as a good composite quickie but looks like a real plane and unlike most planes people talk about, is capable of the 200 mph mark with the right prop.. Couple that with it's stablity and handling, you'll blow everything out of the water with it..
That's what I'd like to get my hands on...(without it costing an arm and a leg )
Know anybody who's willing to part with a decent used one for a "reasonable sum"???
Old 12-14-2006, 06:31 PM
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Default RE: The fastest engine for a viper 500

So I guess the Viper's wing is "slow"? Too thick or out-dated airfoil? Old fashioned balsa sheeted wing?

I've been trying to keep abreast of what's going on over in the pylon forums, and I know that the Viper and Predator(s ) are sort of an intermediate step...then you have the stronger / more efficient Q-500 airframes...then the Q-40's (or is it QM-40? )...am I correct?
Old 12-14-2006, 10:22 PM
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Default RE: The fastest engine for a viper 500

Well, IMO the Viper wing is pretty good (for an ARF).
It is not too thick, it is built to follow the Q500 rule book (1-3/16 inches minimum). And the airfoil was not a bad choice either I think. It is an "old fashioned" sheeted balsa wing, but that doesn't (or shouldn't) make it slow.

The big difference between the composites and a Viper is in the "finesse". Q500 planes all look the same at a glance (because of the rules), but it's the little things that make all the difference.
Pefectly machined wings, tails and fuselages
As aerodynamically shaped as possible without voilating the rules.
A stiff plane (very important)
No hinge gaps (skinned)
Internal linkages
You get the drift

All these little things added up make for a pretty big difference in the end. Stuff you simply cannot do in a chinese or thai ARF shop at "reasonable" cost.
An experienced builder can surely build a foam/wood Q500 that will be close match for any composite plane, that's the beauty of Q500. But it is impossible to deliver that kind of quality in an ARF at 120$.
Old 12-15-2006, 09:57 AM
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Default RE: The fastest engine for a viper 500

ORIGINAL: Rudeboy

Well, IMO the Viper wing is pretty good (for an ARF).
It is not too thick, it is built to follow the Q500 rule book (1-3/16 inches minimum). And the airfoil was not a bad choice either I think. It is an "old fashioned" sheeted balsa wing, but that doesn't (or shouldn't) make it slow.

The big difference between the composites and a Viper is in the "finesse". Q500 planes all look the same at a glance (because of the rules), but it's the little things that make all the difference.
Pefectly machined wings, tails and fuselages
As aerodynamically shaped as possible without voilating the rules.
A stiff plane (very important)
No hinge gaps (skinned)
Internal linkages
You get the drift

All these little things added up make for a pretty big difference in the end. Stuff you simply cannot do in a chinese or thai ARF shop at "reasonable" cost.
An experienced builder can surely build a foam/wood Q500 that will be close match for any composite plane, that's the beauty of Q500. But it is impossible to deliver that kind of quality in an ARF at 120$.
Well said. The airfoil is vital for top speed and the ability to turn with a minimum of speed loss. Newer airfoils that can outperform some of the standbys exist, but the profile is too critical for traditional construction techniques, and the potential performance gains are unlikely to be realized unless they are produced in CNC'ed molds and using decent composite construction methods. That doesn't mean that a wing designed around that airfoil but built from foam and sheet balsa is necessarily a dog, but it may not offer better performance than something less "exotic" if not executed properly.

Those final incremental gains in lap time or top speed are, as you said - all in the little details.
Old 12-15-2006, 10:21 AM
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Default RE: The fastest engine for a viper 500

Thanks guys
By "old fashioned" I guess I just meant that it doesn't have skin (or skinned ) hinges...and I don't think it has CF under (or over ) the sheeting anywhere, does it? It looks like a pretty nice wing to me, but I know that there are better, custom made wings by the "hard core" racers.

I see what looks like coke bottle (or perhaps "laminar flow" would be a better term? ) style fuselages too
They look like a reflexed airfoil from the top view...

I am designing an airframe now (well...the fuselage anyway ) that looks sort of like a fish...like a cross (if you will ) between a Trout and a Barracuda

I plan on carving the shape out of blue (or pink ) foam insulation, then covering it with epoxy / glass w/ some CF reinforcements around critical high stress areas. Then dissolving the foam w/ acetone or lacquer thinner, etc.

I need some ideas though on airfoil selection and % of thickness. I'm thinking around 9 - 10% max.

edit: should also say that it certainly isn't intended to be a Q-500 in any sense of the rules, or appearance...just something different...and hopefully clean / efficient and a good home for my K&B 6.5 RIRE F-1 and scary fast [X(]

nf...sorry for hijacking your thread bud...
Old 12-15-2006, 10:39 AM
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Default RE: The fastest engine for a viper 500

Actually the Viper is really pretty good. The Texas group races them in 428 (fast Q500) and did some serious testing. Viper against Vortex the Vortex is about 2 seconds quicker and 4 mph faster with world class pilots. On the west coast we see the same thing. If the fast composites are running 107’s the Viper’s and Predator’s are within a couple of seconds assuming equal piloting skills. The reason the wood ARF’s get a bad name in 428 is that a majority of pilots and all the fast guys fly composites. At a typical 428 race we have 20 + entries. 17 are composite 3 or 4 are wood. At a typical 424 race we have about 16 entries. 14 are Vipers or Predators and 2 are scratch or kit built.

Barry
Old 12-15-2006, 10:51 AM
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Default RE: The fastest engine for a viper 500

Thanks Barry [8D]

Do you guys think the Viper wing would be strong enough for the fuselage/power that I'm intending to use (as described above )?

Actually I would like to have a wing similar to a Q 40 ship...but I'm not sure of my ability to cut a core and sheet something that thin with the accuracy (and strength? ) that I want / need.
Old 12-15-2006, 11:34 PM
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Default RE: The fastest engine for a viper 500


[quote]ORIGINAL: MJD

ORIGINAL: Rudeboy


The airfoil is vital for top speed and the ability to turn with a minimum of speed loss. Newer airfoils that can outperform some of the standbys exist, but the profile is too critical for traditional construction techniques, and the potential performance gains are unlikely to be realized unless they are produced in CNC'ed molds and using decent composite construction methods. That doesn't mean that a wing designed around that airfoil but built from foam and sheet balsa is necessarily a dog, but it may not offer better performance than something less "exotic" if not executed properly.

Those final incremental gains in lap time or top speed are, as you said - all in the little details.
Indeed. Turning is where the true speed gains are made. Races are not won on the straights...
Old 12-16-2006, 03:57 PM
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Default RE: The fastest engine for a viper 500

how would an os32sx do on a viper????
Old 12-17-2006, 07:02 AM
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Default RE: The fastest engine for a viper 500

Thats is what I have on it right now. But it just not as fast as I would like it to be.[]
Old 12-17-2006, 08:15 AM
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Default RE: The fastest engine for a viper 500

OS .32 should do about 110 mph, maybe a little more with the right prop. Good information above, if you want speed on a quickie, you really need a true racing motor (Jett or Nelson). Keep an eye out for a used motor, they get sold every once in a while that would still get you up near 160 mph and appear much quicker than the 125 mph TT birds your seeing now.
Old 12-17-2006, 01:32 PM
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Default RE: The fastest engine for a viper 500

If you want more speed with a 32 in a quickie just clip 5 or 6 inches off the wing tips.
Old 12-17-2006, 10:50 PM
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Default RE: The fastest engine for a viper 500


ORIGINAL: proptop


ORIGINAL: diggs_74

Forget the Quickie and go with something like this.. About the same cost as a good composite quickie but looks like a real plane and unlike most planes people talk about, is capable of the 200 mph mark with the right prop.. Couple that with it's stablity and handling, you'll blow everything out of the water with it..
That's what I'd like to get my hands on...(without it costing an arm and a leg )
Know anybody who's willing to part with a decent used one for a "reasonable sum"???
PLEASE DEFINE: "reasonable sum" [sm=spinnyeyes.gif]
Old 12-17-2006, 10:55 PM
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Default RE: The fastest engine for a viper 500


ORIGINAL: xandips

how would an os32sx do on a viper????
I have a 32 SX with the Mac muffler on a Kankge F3D-30.
It Hauls butt, but much less wing area and a thinner airfoil too.

BTW my first "speed plane" was a Scat Kat with a TT pro .25
Later the .25 was surplanted with a OS.46FX
Old 12-18-2006, 10:15 AM
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Default RE: The fastest engine for a viper 500


Good post Barry.....

In genernal, the Viper design is sound - and it is quick. Not an obsolete design by any means. But it was designed for sport racing.

I think of late GP has made a few small improvements to the kits (construction) based on feedback from Dub and a few others playing with them in 428 racing. Lets see how that goes.

The actual advantage the composite wings have is more from their tooling - First, they are repeatable - so each wing/aircraft tends to perform the same as the next - consistantcy. As for construction, the advantage is that it is possible to create the complex trailing edge shapes that are nearly impossible to form from foam/wood construction. That last 1/3 of the wing chord is what really makes a difference when it comes to how the wing performs in dash speed and turning.

Of note, the OS32 will be just fine for the Viper. Plane will still be quick, and it will perform great.

I fly a couple of my retired Q-500 airframes with an ST-29 and a Webra 32. Pleanty of power for sport and beat-on use

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