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Turbinator (V2) Thread

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Old 05-08-2016, 04:43 AM
  #26  
EngineDesigner
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Any Ideas on a good starting angle for the installation of a Kingtech 120?

Thank you very much,
SK
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Old 05-08-2016, 06:04 AM
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Originally Posted by EngineDesigner View Post
Any Ideas on a good starting angle for the installation of a Kingtech 120?

Thank you very much,
SK
My JetCentral,Chertah is at about 15 degrees. May need to increase that, waiting for flight test (turbine is currently in Krill Svanti S for initial maiden)
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Old 05-08-2016, 02:00 PM
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Originally Posted by EngineDesigner View Post
Any Ideas on a good starting angle for the installation of a Kingtech 120?

Thank you very much,
SK
I would say 15 degrees at minimum, but I bet the 120 will need more.

I still haven't been able to fully evaluate my 18 degrees.
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Old 05-09-2016, 01:07 PM
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Default fentress

george...is fentress nalf still usable to test fly a new jet....thanks....richard
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Old 05-09-2016, 05:46 PM
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Originally Posted by av8rk View Post
george...is fentress nalf still usable to test fly a new jet....thanks....richard
Yes & No

We still are able to fly at NALF when we get on the schedule, BUT we are currently waiting on the "Non-Gov't Use" permit to get signed AGAIN!, so we are currently not able to fly at the moment. Last year it took 2-3 months (end of May) before it was signed. I'm afraid it will be same this year because we are low priority. The good thing this time though, it will be good for 5 years, so we won't have to worry about it for awhile once it's done.
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Old 05-10-2016, 08:00 AM
  #31  
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This is good to hear as Fentress is a blast to fly at. I still love that place! Lots of great memories there!!!!!
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Old 05-10-2016, 08:11 AM
  #32  
George
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It's still a great place Ron, just not as accessible as it once was.
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Old 10-24-2016, 08:35 AM
  #33  
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Is anyone flying one of these with a 60 size motor??
thx Vin...
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Old 11-06-2016, 06:23 AM
  #34  
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Has George done the maiden yet?
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Old 11-07-2016, 06:57 AM
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Originally Posted by sam@ata View Post
Has George done the maiden yet?
I did the maiden at FJ in the worst possible conditions, so I really didn't get a chance to get things trimmed and set-up properly.

I'm for Fentress to open up again so I can get some flights in.
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Old 11-21-2016, 09:03 PM
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I ended up with a bare very low time airframe from a buddy.. It had the dreamworks gear setup and a 100 sized turbine and would not take off on the very well maintained 800 foot grass runway we sometimes use.. the grass is like Velcro there.. It is the slowest grass I have ever seen.. My gas corsair I can fly in tall grass at home with no problems-- and I mean tall enough you can see the track the prop cuts on takeoff and on landing with no problems, but when on the beautiful 800foot putting green will flip on its back in a heartbeat.... Anyway, the turbinator came in at 27 lbs so dry as I recall. It seemed heavy as heck for what it is to me but it did fly well.. I am thinking phase one is to take the dremel and open the wheel wells to go up 1" in diameter all around on the wheel size and put a 120-140 in it and fly it for a while. If I feel motivated I may put it on a diet and recover it as it looks like it is built like a small plywood tank.. I think bumping it up to 4" mains and a 3-1/4 nose gear would help a lot for longevity and hopefully let it perform on grass better. Should be a simple mod... Anyone running big wheels? and anyone put one on a diet yet?? So far the only jets that I have seen actually make a successful take off from the 800 foot grass were my CARF tutor with 4"1/2 wheels and a way overpowered eurosport 3d and he used a heck of a lot of the grass to get off.
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Old 11-22-2016, 04:07 PM
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My Turbinator (Miss America scheme) has a JetCentral Cheetah with the Dreamworks gear/struts and does well off grass.
Perhaps it's just the thrust?
And yes, it is built very strong ! Makes a great waiver jet.
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Old 11-22-2016, 06:30 PM
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Put flights 5 and 6 on mine this weekend, original 19 lb Jet Central Rabbit, 23lb dry, 3.5" mains, 2.5" nose wheel on Dreamworks struts and it takes off in half of our 700 grass runway. You've got 4 more lbs of weight but 3 more lbs of thrust I would think your performance ought to be fairly close. You might want to double check your CG and make sure its not nose low when on the ground, also I take off with 1/2 flaps.
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Old 11-24-2016, 03:50 PM
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plane is fine, thrust if fine.. it is the grass..it is very very high drag even when cut putting green short...
So has anyone put 4' mains on theirs.. it looks like a 1/2 in shorter struts all around is the way to go with the 1" bigger wheels.
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Old 12-17-2016, 03:29 AM
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Hi, I am working on my first jet. I have the boomerang terminator and I am using a King tech 120G. I would like to know why you needed so much down Thrust? I had emailed Larry at Boomerang and he said he used 5 degrees down thrust with a 100 king tech. I am just want to get it right the first time.
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Old 12-17-2016, 10:18 AM
  #41  
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Originally Posted by TPerk View Post
Hi, I am working on my first jet. I have the boomerang terminator and I am using a King tech 120G. I would like to know why you needed so much down Thrust? I had emailed Larry at Boomerang and he said he used 5 degrees down thrust with a 100 king tech. I am just want to get it right the first time.
It makes the plane less "pitch-sensitive" to throttle position (thrust).
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Old 12-17-2016, 12:33 PM
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Thank for getting back to me, so if you add more down thrust, you would need some up trim in you elevator do to the down thrust pushing the nose down, is the correct. I am not trying to give you a hard time I am just trying to understand.
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Old 12-17-2016, 12:44 PM
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Without changing anything from the stock position, the plane will want to climb at full throttle...if you trim for this setting (down elevator trim), when you come off the power, the plane will want to dive. If you trim for 50%-75% throttle, the plane will want to climb/dive apart from trim speed, but to a lesser degree.

The down thrust will will help in this regard. If it doesn't eliminate it completely, it will reduce it significantly enough to not be a big issue.
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Old 12-17-2016, 01:02 PM
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Originally Posted by TPerk View Post
Thank for getting back to me, so if you add more down thrust, you would need some up trim in you elevator do to the down thrust pushing the nose down, is the correct. I am not trying to give you a hard time I am just trying to understand.
The issue at hand is the exhaust flowing underneath the horizontal stab, which creates a low pressure area there, pitching the nose up. More exhaust = more of that effect and vice-versa.

A down thrust angle proportionally counteracts that, provided you find the right amount for your engine.

Side note comparison: Although the BVM KingCat is in a different league for quality, the Boomerang XL needs no down thrust while the KC is a down-thrust "grass burner". The reason is the Boomer's higher horizontal stabilizer placement, placing the stab out of the exhaust flow's influence.

Last edited by highhorse; 12-17-2016 at 01:04 PM.
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Old 12-18-2016, 02:48 AM
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I think I am starting to understand what is happening, so when you increase the throttle to 3/4 up to full, the air on the bottom of the horizontal stabilizer will now be moving faster the air on top of the horizontal stabilizer. I take it that the speed of the exhaust from the engine is causing the air to move faster under the stabilizer then the air on top of the horizontal stabilizer so you are getting two different air speeds acting on the stabilizer at the same time. So that is why the jets that have the exhaust of the engine back past the stabilizer do not have this issue. Am I getting the right? Please give me any info you have. I am sure,I am not the only one that is trying to understand this issue.

I can't thank you enough for your help
T Perk

Last edited by TPerk; 12-18-2016 at 03:17 AM.
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Old 12-18-2016, 03:30 AM
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You've got it. Exactly.
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Old 12-18-2016, 04:02 AM
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Great, Thank you so much, I am one you those guy that need to understand, WHY. LOL
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Old 12-18-2016, 07:28 AM
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A simple non mechanical (adjusting downthrust angle with shims) fix would be a throttle to elevator mix in your transmitter.
Just add % down elevator vs increasing throttle position.
Its the opposite of a downline mix in a pattern plane (adding a few % of down elevator at low/idle throttle)
Personally I would start with adding downthrust and then add the mix if still needed...F3A guys always strive for "no mix" airplanes
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Old 12-18-2016, 07:41 AM
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Thank you, that is some thing to keep in mind, doing a mix. I did add some down thrust and I will see how that works and go from there.
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Old 12-18-2016, 06:02 PM
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Dont use the mix.. On a low around and you punch it. Immediate pitch down and splat....get the thrust angle right and go fly..
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