Q-40 Racing Discuss AMA 422 and any other variants of Quarter 40 racing

How to maiden a Q40?

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Old 06-21-2009, 11:51 PM
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tIANci
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Default How to maiden a Q40?

The title speaks for itself. I love speed but the thought of doing a maiden on a plane that has no throttle control makes me think twice. How is it done? My pal has got the Rossi Q40 engine on a scratch built pylon plane. I know she will rev up to easily 19,500 RPM on a 9x6. So what prop do Iuse for the maiden and what would you tune her to? In my simple thinking run the 9x6 at about 15,000 RPM, that means she is not very fast, maybe about 65 mph which is most manageable. Any advice please ... this is so new to me. Thanks!!!
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Old 06-22-2009, 05:01 AM
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redfox435cat
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Default RE: How to maiden a Q40?

Break in the big motor on the bench. I take a well broke in TT46 and add the weight differance to the model and balence it for that and maiden it that way. I find it to be pretty close when I strap the beast on it, it's just a helleva lot faster with qm motor.
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Old 06-22-2009, 07:14 AM
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tIANci
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Default RE: How to maiden a Q40?

Redfox ... great idea but I think I got something wrong, not a Q40, just realised, its one with a rear exhaust ... so no motor to use for the maiden. Anyone please?
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Old 06-22-2009, 07:31 AM
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Default RE: How to maiden a Q40?

Make sure you use the recommended throws and CG.  People tend to want to add a little extra throw on a maiden, and it often just causes more issues. Not sure I would leave it that rich, you don't want it dying in the air, but I do normally use a little lighter prop than I normally use and keep it just a little richer than normal.

One thing about Q40's is you HAVE to use right rudder on takeoff. If you forget, you have a good chance of it snapping left as it comes off the ground. Hold the right rudder for a few seconds after leaving the ground, and SLOWLY move the stick back to center. Normally you can tell elevator trim pretty quick, get that rough first, than see if you need aileron trim.

First flight is getting the trims close, not perfect. Once you have that, how are the throws, too much elevator, aileron? Not enough? Try to remember all this so you can make adjustments when you land. I don't like to make more than 5-10% corrections between flights. Keep flying it and adjusting the throws so you can get down to 1% corrections.

If your trim is close, but you just can't hit it perfect, most computer radios have a step function (at Futaba does) where you can adjust the sensitivity of the trim buttons. Once you have it rough, you can fine tune the step and get it even closer to perfect. You want a q40 to fly perfectly neutral at all attitudes at all times. Trim, and CG should get you there.

Lastly, when you put the plane on a 90 degree knife and pull full elevator, what does it do? Does it slightly roll over, does it slowly roll out, or does it come out exactly level to where it started the turn? This can be corrected on the ground with weight to the tips, or it can be mixed out with a Aileron (slave) mixed to Elevator (Master). If you do this, Start at about 5-10% or about 1/32" of aileron movement when pulling elevator. Start small and add or remove till its a perfect exit out of every turn.

For landing, I like to use high rates, about 20% more movement than my low rates. Just be carefull that you don't switch to high rates too quickly after shutting down the engine. I've seen q40's do pretty little snap rolls across the sky from doing just that. Bleed off a little speed before switching to high.

Good luck, let us know how it goes.
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Old 06-22-2009, 10:34 AM
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Default RE: How to maiden a Q40?

Daven ... most enlightening. Thanks for the rudder tip. My pal wants me to maiden her but I am not keen to. Heheheehe ... I shall enlighten him too. Appreciate the assistance.
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Old 06-22-2009, 10:46 AM
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Default RE: How to maiden a Q40?

With the rudder, depending on what plane it is, somewhere between 1/4" and 1/2" throw is plenty, Just try and keep it straight on takeofff (stand behind it if you can). Have it screaming with a friend holding it, and nod to have them give you a solid push. I find it easiest to hold the fuse just in front of the tail feathers to push from. Hold full elevator and rudder and it will be off the ground in no time.
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Old 06-22-2009, 11:54 AM
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Default RE: How to maiden a Q40?

One thing you may not have considered is the engine throttle or kill switch.

Set the throttle to kill the engine when needed.

A Q-40 design is extreamily low drag and may not land if the engine is still running.

This is not too much of an issue with a 9 x 6, but this is much more of an issue if the pitch is higher.

I was running a 9 x 8 on a Thunder Tiger Pro 40. The only way to get the model down was dead stick.

Good luck! [8D]
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Old 06-23-2009, 12:41 AM
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Default RE: How to maiden a Q40?

Sahart ... thanks for the info ... my pal has fashioned his own choke for the carb, I truly hope it works, I warned him about that not working. I told him the 9x6 would be manageable but he wanted to go with a 10x7 of whcih will overload a 40 sized engine. That old bugger is just too stubborn but he is my best pal. Hehehehehee ...

Here are some pics of the plane and notice how much throw he felt would be ok for the maiden? Anyways, I have ensured that the throws were reduced to something more realistic.

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Old 06-23-2009, 07:06 AM
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Default RE: How to maiden a Q40?

Neat plane, what is it?
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Old 06-23-2009, 09:47 AM
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Default RE: How to maiden a Q40?

That looks much bigger than a Q40 for sure..  And with the tail moment being as long as it is, you'll need less rudder than you think to obtain a straight take off. 

AND, the engine in the photo.. looks to be just your average Rossi 40 motor.  The 10x7 should be fine...plus with the pipe as long as it is, you should run a larger prop.  I wouldn't worry about a huge amount of torgue on take off...

You guys got this easily.. no worries.
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Old 06-23-2009, 10:43 PM
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Default RE: How to maiden a Q40?

Dave ... not sure what it is ... one of the guys built it.

Love man ... thanks for the input!
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