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Skymaster 1:7.5 F-4 Phantom

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Skymaster 1:7.5 F-4 Phantom

Old 01-19-2022, 07:32 AM
  #401  
F16Jeff
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Originally Posted by SkyKnight View Post
Setting up as a twin? What engines do you plan to use?
After speaking with John, it will probably be K102G4+ or may do K120g4+. The 120G4+ will have increased power, but additional weight and size.
The Airex air frame is around 800 grams lighter than all glass airframe. The K102g4+ engines are smaller and lighter than the K100g4+. The K100G4+ are 9.27 inches and 2lbs 14 ounces. The K102G4+ are 8 inches long and 2lbs. The diameter is smaller as well.
The weight savings on the turbines and Airex will make up for the extra engine and hardware. Plus will not have power loss with bifurcation pipe.
Curious what others think of this setup.

Old 01-19-2022, 07:37 AM
  #402  
DAN AVILLA
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I had one with 2 P100's it was not over powered. Dan
Old 01-19-2022, 08:13 AM
  #403  
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Originally Posted by DAN AVILLA View Post
I had one with 2 P100's it was not over powered. Dan
Dan,
Did you mentikn not over powered, do you feel that the 100s were underpowered or just right? I will not have ordinance but think of doing the wing tanks. Want to make sure plenty of power for them.

Jeff
Old 01-19-2022, 08:18 AM
  #404  
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I think it could use more power. I did not have ordnance also . Dan
Old 01-19-2022, 08:47 AM
  #405  
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Thank you for the info Dan, I will probably plan on the K1204+ for the additional thrust. Of course they are heavier which will negate some gain.
Old 01-19-2022, 09:13 AM
  #406  
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IMHO...... I'm flying mine with a 220 single with bifabricated pipe. It would fly with a 180, but don't get behind the power curve. It was designed for a 160, and to me, it would be grossly underpowered. With armament, I wouldn't want any less then a 220.

I view twins as double trouble. If you don't understand the aerodynamics of a loss of engine, rudder input for the yaw required for loss of an engine, not to cross control during the loss of engine, go single engine. With the loss of an engine, the ailerons are more neutral then the RC pilot understands. The directional heading is controlled by the rudder and yaw. With an engine flame out that doesn't have the puff of smoke, the pilot is late to discover the loss of engine, because he isn't sitting behind the panel. Except for TO, where the pilot will know right away. With a twin, I would definitely have engine telemetry that can be set up with Jeti or Core and VSpeak. The telemetry will notify you of an engine loss, before you will realize it. Clean, you won't notice much difference, until you slow down. I flew with a guy two months ago that had his set up as a twin. His had a different sound, but I didn't see the benefits. My guesstimate is that 90% of the guys loose a twin, especially on take off. Single engine, the choice is made for you with a loss of engine. Just don't put gear and flaps down until runway is assured, and you haven't slowed too much. Best glide is clean.
Old 01-19-2022, 11:34 AM
  #407  
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Now you have me rethinking my decision. I was thinking that the turbines being so close to centerline, a flameout of one would not be as significant as if they were spread further out.
i understand aerodynamics and not turning into the dead engine. Also applying opposite rudder if you know which engine is out and reducing throttle on good engine. Keep airspeed up as much as possible and keep it clean.
Just really liked the idea of having a twin turbine F4.
I have time to consider the change.
Thank you for your advice.
Jeff

Originally Posted by RCFlyerDan View Post
IMHO...... I'm flying mine with a 220 single with bifabricated pipe. It would fly with a 180, but don't get behind the power curve. It was designed for a 160, and to me, it would be grossly underpowered. With armament, I wouldn't want any less then a 220.

I view twins as double trouble. If you don't understand the aerodynamics of a loss of engine, rudder input for the yaw required for loss of an engine, not to cross control during the loss of engine, go single engine. With the loss of an engine, the ailerons are more neutral then the RC pilot understands. The directional heading is controlled by the rudder and yaw. With an engine flame out that doesn't have the puff of smoke, the pilot is late to discover the loss of engine, because he isn't sitting behind the panel. Except for TO, where the pilot will know right away. With a twin, I would definitely have engine telemetry that can be set up with Jeti or Core and VSpeak. The telemetry will notify you of an engine loss, before you will realize it. Clean, you won't notice much difference, until you slow down. I flew with a guy two months ago that had his set up as a twin. His had a different sound, but I didn't see the benefits. My guesstimate is that 90% of the guys loose a twin, especially on take off. Single engine, the choice is made for you with a loss of engine. Just don't put gear and flaps down until runway is assured, and you haven't slowed too much. Best glide is clean.
Old 01-19-2022, 12:11 PM
  #408  
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Originally Posted by F16Jeff View Post
Now you have me rethinking my decision. I was thinking that the turbines being so close to centerline, a flameout of one would not be as significant as if they were spread further out.
i understand aerodynamics and not turning into the dead engine. Also applying opposite rudder if you know which engine is out and reducing throttle on good engine. Keep airspeed up as much as possible and keep it clean.
Just really liked the idea of having a twin turbine F4.
I have time to consider the change.
Thank you for your advice.
Jeff
The other negative to having a twin that is over powered is VMCse is at a higher speed. This means at full thrust on the single engine, you will run out of rudder at a higher airspeed during a single engine loss.

Close to center line thrust still requires more rudder then you think. DC9, 727, corporate jets are close to centerline, and still require a lot of rudder.

Last edited by RCFlyerDan; 01-19-2022 at 12:14 PM.
Old 01-19-2022, 01:28 PM
  #409  
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You sold me, I sent a change request to John at Skymaster. Going with the single 200 build which will also make adding smoke easier. I am currently building my 2nd 1/9.5 scale F4e with K142G4 turbine. I love how this one is going together. So the 1/7.5 should be good as will. Probably easier to get all the electronics added since it will be larger.


Originally Posted by RCFlyerDan View Post
The other negative to having a twin that is over powered is VMCse is at a higher speed. This means at full thrust on the single engine, you will run out of rudder at a higher airspeed during a single engine loss.

Close to center line thrust still requires more rudder then you think. DC9, 727, corporate jets are close to centerline, and still require a lot of rudder.
Old 01-19-2022, 04:35 PM
  #410  
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Originally Posted by F16Jeff View Post
You sold me, I sent a change request to John at Skymaster. Going with the single 200 build which will also make adding smoke easier. I am currently building my 2nd 1/9.5 scale F4e with K142G4 turbine. I love how this one is going together. So the 1/7.5 should be good as will. Probably easier to get all the electronics added since it will be larger.
Jeff,

I'm not trying to change your mind. Just pointing out issues with two engines. There are issues with a single too. It's just being aware of characteristics of the plane you are flying. And, how to handle the emergency, should you be put in that situation. Could mean saving the jet or not.

You could also go BIGGER! They have them made for two! 😂😂
Old 01-20-2022, 06:37 AM
  #411  
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Jeff

I think you made correct decision on the single. I have flown lots of F4s and I currently have two 1- 7 3/4 skymasters with 220 and 210 class engines in them
Old 01-25-2022, 07:34 AM
  #412  
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Originally Posted by kevinthoele View Post
Jeff

I think you made correct decision on the single. I have flown lots of F4s and I currently have two 1- 7 3/4 skymasters with 220 and 210 class engines in them
Hi Kevin,
I decided to go back to my original twin build on the F4. Will add turbine telemetry to alert of a flame out. Several pilots at my filed are flying twins from Yaks, F18s, and F4s.
I have a twin FB F-15E that will be a twin as well. The K142s will arrive this week for this one. My Extreme 1/9.5 F4E is getting a single K142g4. Currently building this one.

Jeff

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Old 01-25-2022, 12:41 PM
  #413  
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No matter the twin turbine, I don't have a twin, but have a set up question. If I were to set one up, I would strongly consider a few degrees of outward thrust at the tail. Just as we have trimmed approximately 5į of down thrust with the F4. Outward thrust would help with yaw, should the opposite engine quit. In my mind anyway. It's practiced with prop jobs.

Want to see if anyone flying any turbine twin, sets their jet up with outward thrust? Or ideas about the subject.
Old 01-28-2022, 01:12 AM
  #414  
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I have 5 flights with the bend as in Original Setup in picture below:

And are now planning on using the New Setup in the following flights this season:

Question;
What to look out for in the next flight? Anything to worry about? Elevator trim perhaps?


Here is where I set zero degrees;




Tail-pipe now pointing so much down, that I will have to bend that fiber-glass nozzle downwards too, otherwise it will be melted.



Original setup and new setup. It will be 10 degrees difference !!!!!
Old 01-28-2022, 07:02 AM
  #415  
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Originally Posted by kwik View Post
I have 5 flights with the bend as in Original Setup in picture below:

And are now planning on using the New Setup in the following flights this season:

Question;
What to look out for in the next flight? Anything to worry about? Elevator trim perhaps?


Here is where I set zero degrees;




Tail-pipe now pointing so much down, that I will have to bend that fiber-glass nozzle downwards too, otherwise it will be melted.



Original setup and new setup. It will be 10 degrees difference !!!!!
you need to have engine and fuse at zero with total of five degrees down on pipe. The bend takes care of that. Or you can run straight pipe with engine and pipe at 5 degrees down
Old 01-28-2022, 03:06 PM
  #416  
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Why reverse the pipe? Are you getting a pitch change with throttle? I use a Tams pipe and get some pitch change (can't remember what direction) but, I just mixed it out with a throttle to elevator mix years ago and have never thought about it again.

Mike
Old 01-28-2022, 05:46 PM
  #417  
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Originally Posted by luv2flyrc View Post
Why reverse the pipe? Are you getting a pitch change with throttle? I use a Tams pipe and get some pitch change (can't remember what direction) but, I just mixed it out with a throttle to elevator mix years ago and have never thought about it again.

Mike
I have two Phantoms flying and have helped set up others. With the Tam pipe I set 5 degrees down turbine angle and match Tam pipe to 5 degrees down. No pitch change with throttle at all. Same situation with bent pipe. Set engine level at 0 and measure pipe at rear and move till it is 5 degrees down resulting also in no pitch changes with throttle!!! Then fabricate bulkhead to hold pipe in place.
Old 01-29-2022, 04:42 PM
  #418  
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I have gotten some heat-bubbles in the paint on the underside of the elevators using "Original Setup".

Therefore I was thinking "New Setup" is matching what some of you guys have said we should do.

I dont know whether this is the Tam pipe or the SM pipe, but its bent 5 deg on the middle as indicated in the drawing.

And I have read earlier that the Tam pipe is straight, so this must be the SM pipe.(?)



Last edited by kwik; 01-29-2022 at 04:56 PM.
Old 01-29-2022, 04:52 PM
  #419  
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+
Originally Posted by kevinthoele View Post
Same situation with bent pipe. Set engine level at 0 and measure pipe at rear and move till it is 5 degrees down resulting also in no pitch changes with throttle!!! Then fabricate bulkhead to hold pipe in place.
Okay, then I must eliminate the front 5 deg in "New Setup", and only have the aft 5 deg left, I think ......

To achieve that, the pipe might hit the upper part of the exit-hole in the fuselage. But I will try and see what happens.



By the way, thank you all for bothering answering my questions.

Last edited by kwik; 01-29-2022 at 04:58 PM.
Old 01-29-2022, 07:32 PM
  #420  
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Originally Posted by kwik View Post
+

Okay, then I must eliminate the front 5 deg in "New Setup", and only have the aft 5 deg left, I think ......

To achieve that, the pipe might hit the upper part of the exit-hole in the fuselage. But I will try and see what happens.



By the way, thank you all for bothering answering my questions.
No problem. I just looked again. I leveled the fuse to 0 and put stick on top of pipe at rear and itís 5 degrees down. It does get close to top of bulkhead as pipe starts back and it is close to bottom of tail cones at rear. If itís the bent pipe itís Skymaster. My Tam pipe is straight. Both set ups will help with the heat on tail planes
Old 03-01-2022, 10:02 AM
  #421  
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For those of you "Rhino" pilots who have installed "drogue chutes", what size chute did you use? I've already mocked up the deployment mechanism, but the chute I presently have is a 1/6th [email protected] 34in.diameter and won't deploy consistantly
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Old 03-01-2022, 11:01 AM
  #422  
F16Jeff
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I get my chutes from RC Jet Chutes. Currently getting a 20" chute for my 1/9.5 scale F4.e. This one would need around 25" diameter for scale. I plan to order one that size once my 1/7.5 F4e arrives.
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Old 03-27-2022, 06:45 AM
  #423  
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Default Servos for this jet?

Hi all,
I heard from John that my jet will head to piant shop in a couple weeks. Mya have it end of April or beginning of May.
My question is the servos. I use Savox servos and plan to use SC1256tg w/277 oz of torque on ailerons, flaps, and rudder. I was thinking of using SA1230sg on stabilator. Do I need two on the stabilator or would one suffice? It puts out 500oz of torque.

Thank you for your assistance

Jeff
Old 03-28-2022, 06:17 AM
  #424  
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That "raw aluminum" on the stabs wasn't just for looks on the real aircraft. Advise that, no matter how you pipe it, flite metal the silver. Keep the finish as reflective as possible. On the real jet, thats where the engine exhaust would hit the stab. They quickly figured out, paint on that area would blister and burn off first flight out.

Wasn't just for looks. If it were me, I'd flitemetal and then paint the stabs to give the glass some protection from the heat.
Alyminum hvac tape would also work. Any printing on the aluminum can be removed with isupropyl alcohol before painting.
Old 07-10-2022, 12:44 PM
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Cheers!
Desert Fox 1
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