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Vought F7U Cutlass....will it fly?

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Vought F7U Cutlass....will it fly?

Old 10-29-2009, 11:23 PM
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JohnMcGowan
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Default Vought F7U Cutlass....will it fly?

[img][/img]Well here is a rare bird indeed, a WAY OFF-stand back about 20 foot type- funscale Vought F7U Cutlass kit made by Global .
It weighs in at 7lbs ,4 oz and has an OS 46SF with a 10x7 prop for power. I hope to do the maiden this Sunday if the weather co-operates. Its got split ailvators, all for turning and for the up and down motion, all done with 2 metal gear servos. Rudders are fixed and non operational. This thing might just be a bear to fly due to its really thin wing, but there's only one way to find out right?I hope this one flies lots better than the real one! [sm=drowning.gif]
Thats a shot of my good friend Brian who did some amazing work to finish this plane for me.
[img][/img][img][/img]

John
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Old 10-29-2009, 11:51 PM
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JohnMcGowan
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Default RE: Vought F7U Cutlass....will it fly?

one more...[img][/img]
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Old 10-30-2009, 12:00 AM
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Ram-bro
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Default RE: Vought F7U Cutlass....will it fly?

its just a flying wing. I heard somewhere thye are OK flyers....Is there some reason why you think it wont fly? hey, its a good looking bird.
Old 10-30-2009, 12:12 AM
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Default RE: Vought F7U Cutlass....will it fly?

Thanks Ram.
I dont know, maybe Im worrying over nothing, the wing is super thin though. With no working rudders on it, Im just thinking if she ever decides to spin on me, this party is OVER! LOL
It should be (hopefully) fast though. I may have to play around with props to see what gives the best overall flight...if it makes it thru the maiden... will keep you posted.
Later,
John
Old 10-30-2009, 12:41 AM
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Default RE: Vought F7U Cutlass....will it fly?

remember , better nose heavy than tail heavy
Old 10-30-2009, 12:07 PM
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Default RE: Vought F7U Cutlass....will it fly?

The real one was nicknamed "Gutless"
http://www.youtube.com/watch?v=il-19...eature=related

http://www.youtube.com/watch?v=9CT67...eature=related


jeff
Old 10-30-2009, 07:40 PM
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Craig-RCU
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Default RE: Vought F7U Cutlass....will it fly?

The real one was only called that because it was underpowered. I don't think that will be a problem for this model that is powered by a 46sf. I might go with a 10x5 prop instead of a 10x7 to give more static thrust for powering out of trouble quicker and to keep the top end speed down for a nervous first flight.

Beautiful model, John and best of luck on the maiden flight.
Old 10-30-2009, 11:19 PM
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Default RE: Vought F7U Cutlass....will it fly?

Thanks so much Craig.
I've got the cg where she is nose down at 5° when measured at the cg point and the plane has a tad of negative incidence when sitting on the ground so that I can build up some speed on takeoff and then feed in some up elevator to lift off, instead of how the original full scale plane sits nose high with that long front landing gear strut that would push thru the cockpit and sometimes kill the pilot on a hard carrier landing... that has nasty takeoff wreck written all over it
Yes, the full scale plane were way underpowered and plagued with hydraulic problems and killed several test pilots as well as numerous air force pilots.
We'll know Sunday , good weather permitting, if she's a keeper or not. Is either going to be really good or really bad .

John
Old 10-31-2009, 02:38 AM
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Default RE: Vought F7U Cutlass....will it fly?

I'd recommend against negative incidence. Depending on how close the main gear are to the CG, it may be really hard to take off if you have a negative incidence set up when sitting on the ground. That swept back nose gear will bend back and compress more as speed and negative lift increase. Drag from the front wheels can cause more negative incidence when trying to take off too, especially if you are taking off from grass. If it is able to take off with the negative incidence, it will probably take a lot of elevator input. It could then suddenly pop off the runway into the air because it will be hard for the pilot to react to the sudden leap into the air and reduce elevator input before the plane is in a steep climb-out angle. This can cause speed to drop quickly and possibly cause a stall at low altitude. I'd recommend a positive incidence of at least a couple of degrees. Your plane will have to be moving at cruise speeds in order to take off with a positive 2 or 3 degrees incidence which is well above stall speed so should be plenty safe. Bending the nose gear forward might get you enough positive attitude and also minimize any compression due to wheel drag bending the gear backwards. What do the instructions recommend for AOA while on the ground?
Old 10-31-2009, 02:29 PM
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Default RE: Vought F7U Cutlass....will it fly?

They actually dont have a recommended ground AOA Craig. Its very minor they way its set up now while sitting on the ground and I can always change that by moving the front strut (lengthening) out appx 1/4 inch or so.
What I was concerned about, and it might be for nothing, is that I had read others who had built this plane and they had used the positive angle on the front strut and the bird had lifted off BEFORE it had acheived flying speed and then did the infamous figure 9 manouver .. so we're sure not wanting that to happen.
The plane is upgraded with 3/16 rear main landing gear wires instead of the suppiled 5/32 crap that will bend if you even look at it, so its a little beefier there.
Our runway at the club is appx 650 ft of good asphalt runway, so if she wont come up off from that, I need to take up knitting or something, LOL. I'll be ready to relax the elevator should it be needed right after takoff. I need to go downstairs and dial in some expo in the tx ..( I like expo due to the handshakes and knee-knocking on a new plane, and most any other time I fly , my flying buddies makes fun of me saying : Look at McGowan over there and how much his antenna is whipping around ,it looks like a polygraph needle bobbing up and down when giving a politician a lie detector test, LOL)
The weather is supposed to be good, clear skies and wind about 6 to 10, so I think its a go.. Im trying to get one of my buddies to run the camera for me so we can get some video,.. I'll be the one with the tx antenna weaving back and forth[sm=spinnyeyes.gif]
We'll keep you posted, wish me lots of luck.

John
Old 11-01-2009, 12:29 AM
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Default RE: Vought F7U Cutlass....will it fly?

http://www.rcuniverse.com/forum/m_31...10/key_/tm.htm
I browsed through this thread after my last post and found some posts that confirm my advice in my last post. The plans are on the first page of the thread and they show the nose gear extends further below the fuse than do the main gear. This will result in a positive AoA of a couple of degrees at least. In post #233, Blade47 recommends increasing the AoA another 3 degrees by extending the nose gear 1.5". I found a reference to the "figure 9" maneuver in that thread but not a description of what caused it in the Global Cutlass plane design. A figure 9 is the flight path that a tail heavy plane will follow on take-off, though, especially if one has to hold in a lot of up elevator to overcome a ground AoA that is not steep enough. In post #233, Blade47 also has a recommended C.G. marked in red, so it could be that this is forward of the plan's possibly tail-heavy C.G. recommendation. Anyway, best of luck with your maiden tomorrow.

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