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-   -   Viper 500 questions (http://www.rcuniverse.com/forum/extreme-speed-prop-planes-104/1980751-viper-500-questions.html)

radiocontrol 07-11-2004 05:30 PM

Viper 500 questions
I flew my GP Viper for the first time today. Man, that plane is quick!! I landed on high rates as the manual instructed, but I think I could have had plenty of ruddervator on low rates. Does anyone land on low rate ruddervator when it specifies movement of 1/8"? Also, would there be any disadvantage to mounting the engine right side up to get the muffler out from under the plane? It barely has clearance to the ground the way the manual specifies. Also, I landed dead stick to keep the prop from hitting the ground. Does anyone know of a manufacturer that makes a carbon fiber landing gear for this plane that is longer than the stock gear? Any comments would be appreciated!

JohnBuckner 07-11-2004 07:03 PM

RE: Viper 500 questions
The reason you will never see any serious Quickee racer with an upright mounted engine is the impossiblilty of getting the fuel supply high enough to prevent leaning problems under (G) load. The spray bar must be down near the center of the fuel tank. The well flown Quickee can also use the muffler as a brake by applying down elevator, don,t laugh this is a commonly used technique.

Always land a Quickee dead stick, trying to land with an idling engine just results in floating off the runway end. Once agine this is the normal technique. Do not try to taxi a Quickee and do a throttle up takeoff. This frequently results in ground loops and prop strikes. The technique is to have a helper hold the airplane in position and throttle up, then after power is stabilized he will release. The airplane with any forty will be off the ground in a few feet and stable.

Yes there is carbon gear avaliable from LCS performance but the gear will be no longer. This airplane is a racer and there is no reason to make long higher drag gear.


bob27s 07-12-2004 07:29 AM

RE: Viper 500 questions

ditto on what John said.

what engine and prop are you running right now ??

I have a 15 year old scat cat with nothing more than a tail skid that will taxi out and back nicely every flight. Retired from racing, right now it just has an old ST.29 and revup 8.75x7 prop. Engine side mounted, muffler underneath.

I run my Q-500 engines 90 deg to the side using the square backplate mounts. I also have run with 30deg cylinder down so the muffler goes under the center line of the fuselage between the gear. Best fuel flow either way.

For most of us in Q-500, the muffler ends up being a 'skid' of sorts once in a while... protects the prop and fuselage.

For general sport use, where you are flying more than high-g left turns, you can orient the engine how you wish, as long as the engine will draw fuel well.

radiocontrol 07-12-2004 05:21 PM

RE: Viper 500 questions
I am currently running an OS .46 AX with a 10x7 APC prop. Now that the engine is broken in, I will be switching to an APC 9x8.5 pylon prop. I am flying this plane for sport only, and don't plan on entering any competitions. One question that John didn't answer: since the Viper comes in very fast on landing, would I have enough ruddervator control to land on low rates? The manual says to use hi rates, but even at landing speed, the ruddervator is so sensitive!

garys 07-12-2004 05:48 PM

RE: Viper 500 questions
You probably could land on low rates without any problems. In 16+ years of racing, I've preferred to have my racers set up without dual rates if possible. I just land a little hotter than some others. Some planes can still slow to a crawl without high rate, it just depends on airfoil and CG.
Gary Schmidt
Team Futaba

bob27s 07-13-2004 07:29 AM

RE: Viper 500 questions

If you are just sport flying the plane....... set the CG up at 2.2" back from the leading edge. Set up the elevators so they are comfortable for normal flying, and you will have pleanty of control authority at that same throw (rate) to land the plane.

Btw...... the plane will land at the same speed most sport planes will....sometimes slower. Take some time to learn how to slow it down. Practice at idle at altitude. You will see that the plane is well behaved flying slow, and it will let you 'feel' how the controls react when you approaching stall. Usually the tail will stop flying first, and the nose will drop... just ease off the elevator, and the plane will recover. It is only when flying 'really slow' like this where the extra high-rates come into use sometimes.

You are actually better off switching to that smaller prop now. Let the engine turn up a bit. Always, keep it slightly rich by 500-800 rpm and you will rarely have any problems.

radiocontrol 07-13-2004 05:57 PM

RE: Viper 500 questions
Thanks guys. I appreciate all your input. I'll let you know how my next flights turn out.

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