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Skymaster 1:7.5 F-4 Phantom

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Skymaster 1:7.5 F-4 Phantom

Old 07-05-2017, 04:12 PM
  #26  
MaJ. Woody
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Thanks Kevin!
Old 07-06-2017, 06:09 AM
  #27  
Chris Smith
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Since the subject of CG is being discussed, it is interesting that a number of guys are way aft with their CG compared to the Skymaster design CG.
The Skymaster manuals say 280-300.
Old 07-06-2017, 06:15 AM
  #28  
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Skymaster was being very conservative with the recommendations. I would be a little afraid of 280 as it is very nose heavy. So many guys have moved the CG back that I would feel Skymaster may want to change their recommendations to say 310-330. I have heard of some back as far as 350 but I would start 310-320 for those that don't want to go to 340 to start but you will eventually move back from there. Although you may like a nose heavy plane and if that's your style OK
Old 07-08-2017, 09:48 PM
  #29  
ozief16
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Has anyone balanced their stabs?

if I shut off power the stabs move rapidly to a full down position. Should I be thinking about statically balancing them? I have a ton of power on them (two MKS 777s) but am not wise on such questions

Thanks
Dave
Old 07-09-2017, 06:32 AM
  #30  
Kelly Rohrbach
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At 62 lbs of torque I bet it don't matter. It might save some battery drain. I think the benefit might be just not having the servo snapping to attention from full deflection to neutral.
Old 07-09-2017, 10:05 AM
  #31  
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Good point kelly. I wonder if the Jeti has a "soft start" function? I'm not home so can't look now. The flaps also have 777s on them and go to full deflection the second the power shuts off
Old 07-09-2017, 01:08 PM
  #32  
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You could place tiny rare earth magnets on the inside of the stab to assist in holding the stab centered.
Old 07-09-2017, 04:43 PM
  #33  
Kelly Rohrbach
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Soft start would be a nice feature, of course not for everything. ��
Old 07-09-2017, 09:02 PM
  #34  
ozief16
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Good idea buck
Old 07-10-2017, 02:12 PM
  #35  
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Jeff, can you give me the gain settings you are running for the Igyro? I had one in my Edwards F4 but I sold it and don't have the numbers. Im not a fan of the test fly asst.
Thanks Don
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Old 07-10-2017, 05:16 PM
  #36  
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Originally Posted by Jetkopter View Post
Jeff, can you give me the gain settings you are running for the Igyro? I had one in my Edwards F4 but I sold it and don't have the numbers. Im not a fan of the test fly asst.
Thanks Don
Hi Don, sent you a PM.

Cheers,
Old 07-10-2017, 06:30 PM
  #37  
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Jeff, thanks for the info !
Old 07-11-2017, 01:44 AM
  #38  
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Originally Posted by ozief16 View Post
Good point kelly. I wonder if the Jeti has a "soft start" function? I'm not home so can't look now. The flaps also have 777s on them and go to full deflection the second the power shuts off
Soft Start is a servo function, the TX has no way to know were the servo position is....even on JETI.

That will eventually change with the new DITEX Hacker servos once the Telemetry (JETI software update when???) for the servo is available. I have a bunch of those for my next build.
Old 06-18-2018, 06:29 AM
  #39  
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I am approaching the big test flight day. I have my cg set at 330 and the fuel tanks in series. The front main, lt saddle then rt saddle. The stab is set as shown in the picture in this thread. Will it survive at these settings? Dry wt 36#. Rhino 38# for blow.
Old 06-18-2018, 07:19 AM
  #40  
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Luv Me Some F-4s. One day I hope to be an accomplished jet pilot able to build and fly one ---- one day. I love the RF-4 Spirit of America or the F-4F Phantom II WTD61 "Flight Test". Both are beautiful. Chic

Last edited by redtail; 06-18-2018 at 07:22 AM.
Old 06-18-2018, 10:28 AM
  #41  
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Originally Posted by tp777fo View Post
I am approaching the big test flight day. I have my cg set at 330 and the fuel tanks in series. The front main, lt saddle then rt saddle. The stab is set as shown in the picture in this thread. Will it survive at these settings? Dry wt 36#. Rhino 38# for blow.

Yes, that all sounds very reasonable.

The problem with skymasterís CG and pipe is:

CG: At their CG recommendation, with full flaps, the airplane will lose elevator authority and it wonít be to pull up if the nose drops. Hence, your CG is better.

Pipe: SMís pip has a bend in it. If it isnít place so the bend is down, the F-4 will want to climb with power. Tamís pipe is straight and people report no climbing with Tamís pipe.

Go fly it! You will love it!!
Old 06-18-2018, 03:17 PM
  #42  
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I love mine so much I ordered another. This one will be totally decked out lighting and full ordinance. I would put CG at 340 and never look back. Use Tam pipe with 5 degrees down angle or skymaster with bend going down.

My tanks feed saddles and then the front. Fuel for long flight with K210 7 plus minutes

Hope this helps
Old 06-18-2018, 04:26 PM
  #43  
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Thanks Kevin. I think i will stay at 320 for the first flt since my cg will move back as fuel is burned from the main tank first. At least i am in the ball park. I need to add 3# to the nose to get it to the 320 point. Was really surprised with that. I dont have a cockpit kit yet but it is still fwd weight but at least it will be useful weight. If anyone has a cockpit from a departed one please let me know. Also pylons and wing tanks.
Old 06-18-2018, 09:43 PM
  #44  
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Tom,

i just bumped another thread that has a lot of good data in it for your SA

Dave

ps-if you need anything specific let me know and Iíll help if I can
Old 06-19-2018, 02:31 AM
  #45  
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Thanks Dave...good info
Old 07-18-2018, 08:49 AM
  #46  
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Originally Posted by kevinthoele View Post
I love mine so much I ordered another. This one will be totally decked out lighting and full ordinance. I would put CG at 340 and never look back. Use Tam pipe with 5 degrees down angle or skymaster with bend going down.

My tanks feed saddles and then the front. Fuel for long flight with K210 7 plus minutes

Hope this helps
if you flip the stock pipe with bend going down do you still set engine 5 degrees Down thrust as well?
Old 07-18-2018, 10:53 AM
  #47  
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I will have my engine going straight down the middle of pipe. I have not done this yet but Tam is out of the pipe business so I ordered the bigger pipe from Skymaster. The net result should be 5 degree down angle on exhaust

Last edited by kevinthoele; 07-18-2018 at 02:13 PM.
Old 07-18-2018, 11:07 AM
  #48  
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Originally Posted by kevinthoele View Post
I will have my engine going straight down the middle of pipe. I have not done this yet but Tam is out and the pipe business so I ordered the bigger pipe from Skymaster. The net result should be 5 degree down angle on exhaust
ok I think I follow you. Keep the front of the pipe at stock height. It's the bend that creates the 5 degrees down ...correct?

The guy that worked at Tams is now on his own . He is on facebook. He just did a pipe for the F4 7.75.
Hiep custompipe
Old 07-18-2018, 12:10 PM
  #49  
kevinthoele
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Well now that I bought Skymaster pipe Iím going to try it. Yes motor stock location and bend in pipe does 5 degrees. I will measure and may need to shim pipe and motor to match to get 5 degrees down angle total at exit. You can call me if you have any questions
kevin thoele 281-615-8455
Old 07-18-2018, 12:12 PM
  #50  
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Originally Posted by kevinthoele View Post
Well now that I bought Skymaster pipe Iím going to try it. Yes motor stock location and bend in pipe does 5 degrees. I will measure and may need to shim pipe and motor to match to get 5 degrees down angle total at exit. You can call me if you have any questions
kevin thoele 281-615-8455
Thanks Kevin !

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