Yellow Aircraft F4 Phantom jet pipe design and other questions
04-21-2018, 03:33 PM
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Yellow Aircraft F4 Phantom jet pipe design and other questions
Hello Everybody,
I finally got my hands on a unopened "brand new" Y/A F-4 Phantom kit. These are very difficult to find in Spain and I had a great experience with the F-18 (still flying:-))
But for this new kit I have some big decisions and questions:
Jet pipe design for Jetcat P-60:
Long straight part:
"photos.app.goo.gl/X39bcrOnUoLY9GYD3"
I am considering this one due to some pipe issues that I had with the F-18 due to breakage of the pipe divisor
Short straight part:
"photos.app.goo.gl/3XIUr2lhZlMLjurx2"
Looks like could deliver better performance based on some post in RCU and RC groups... But I don't know.
In any case I am considering leaving the final part of the tube in angle rather than adding a straight ending, as seems to provide less friction to the ariflow.
Any thoughts on these? or maybe other options that are better? in both cases I am using 20% greater exit area than the intake (70mm diameter). Is that ok? i just estimated that this could be ok, but there is no calculations behind.
Other concern is the alignment of the pipe and turbine. I can see that in the Phantom the pipe thrust line is not aligned with the fuselage, but pointing down... Wouldn't make sense to angle the turbine to align it to the pipe? the original ducting seems to have the EDF aligned with the wing, rather than the thrust line.
Questions on the kit.
It seems to be made for permanent attachment of the wings to the fuselage, and all the effort seems of some stingers coming out from the formers in the fuselage. These stingers are glued to the foam core of the wing that is balsa sheeted. In any case I am going to glass the wing, but is this strong enough for turbine conversion?.
Is there any reinforcements that should be done in the airframe overall to cope with the extra weight an stress of turbine power?
Any suggestions, pictures or links are welcome:-)
Fuel tanks:
I have read some sad posts about GC shifting due to the weight of fuel making the plane nose heavy and unresponsive to the point of crash. To counteract this effect and still carry enough fuel for a reasonable flight time I was planning to copy the fuel tank scheme of the F-18. 2 conforming fuel cells slightly behind the GC and a third fuel tank ahead of the CG. But I don't know how to calculate the fuel conforming cell positions and overhang on the GC to maximize the capacity and minimize the CG shift on flight.
Any hint on how to do this calculations is very welcome. :-)
Flaps on landings: The manual states that flaps should not be used on landings due to some blanking of the elevator control, but in some post from Shaun Evans it seems that is a misconception. Maybe is the language barrier but it still not clear to me, should flaps be used for landing this plane or they may pose some issues with the effectiveness of the elevator?
Thank you in advance from any help and guidance you can provide and best regards
I finally got my hands on a unopened "brand new" Y/A F-4 Phantom kit. These are very difficult to find in Spain and I had a great experience with the F-18 (still flying:-))
But for this new kit I have some big decisions and questions:
Jet pipe design for Jetcat P-60:
Long straight part:
"photos.app.goo.gl/X39bcrOnUoLY9GYD3"
I am considering this one due to some pipe issues that I had with the F-18 due to breakage of the pipe divisor
Short straight part:
"photos.app.goo.gl/3XIUr2lhZlMLjurx2"
Looks like could deliver better performance based on some post in RCU and RC groups... But I don't know.
In any case I am considering leaving the final part of the tube in angle rather than adding a straight ending, as seems to provide less friction to the ariflow.
Any thoughts on these? or maybe other options that are better? in both cases I am using 20% greater exit area than the intake (70mm diameter). Is that ok? i just estimated that this could be ok, but there is no calculations behind.
Other concern is the alignment of the pipe and turbine. I can see that in the Phantom the pipe thrust line is not aligned with the fuselage, but pointing down... Wouldn't make sense to angle the turbine to align it to the pipe? the original ducting seems to have the EDF aligned with the wing, rather than the thrust line.
Questions on the kit.
It seems to be made for permanent attachment of the wings to the fuselage, and all the effort seems of some stingers coming out from the formers in the fuselage. These stingers are glued to the foam core of the wing that is balsa sheeted. In any case I am going to glass the wing, but is this strong enough for turbine conversion?.
Is there any reinforcements that should be done in the airframe overall to cope with the extra weight an stress of turbine power?
Any suggestions, pictures or links are welcome:-)
Fuel tanks:
I have read some sad posts about GC shifting due to the weight of fuel making the plane nose heavy and unresponsive to the point of crash. To counteract this effect and still carry enough fuel for a reasonable flight time I was planning to copy the fuel tank scheme of the F-18. 2 conforming fuel cells slightly behind the GC and a third fuel tank ahead of the CG. But I don't know how to calculate the fuel conforming cell positions and overhang on the GC to maximize the capacity and minimize the CG shift on flight.
Any hint on how to do this calculations is very welcome. :-)
Flaps on landings: The manual states that flaps should not be used on landings due to some blanking of the elevator control, but in some post from Shaun Evans it seems that is a misconception. Maybe is the language barrier but it still not clear to me, should flaps be used for landing this plane or they may pose some issues with the effectiveness of the elevator?
Thank you in advance from any help and guidance you can provide and best regards
05-01-2018, 06:28 AM
#5
My Feedback: (1)
F4 setup
I have built and flown many yellow F4s. I did one straight pipe set up and flew it many years until it was sold. I however made former for the back and had pipe go straight out the back. Best option if you want to do single straight pipe. Also used Tam bifurcated pipe with good results as well. I sold my last one set up this way to a friend was is going through it to make new again
Call if you have any questions 281-615-8455
Kevin
Call if you have any questions 281-615-8455
Kevin
05-02-2018, 07:14 PM
#6
Join Date: Mar 2009
Location: Canberra, AUSTRALIA
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I think I'm the one you're referring to regarding the sad report of a nose heavy aircraft. Yep, sure was sad - not even one circuit. In retrospect there might have been some other explanations for the crash, like signal loss, or maybe turbine flame out (I couldn't hear my aircraft over the sound of another taking off next to me). But, it was nose heavy on take off and needed lots of up elevator which I was desperately trying to trim for in the few moments before it went in. I would still strongly urge you to use two saddle-like tanks in the turbine bay, in conjunction with a (smaller than mine) main tank.
I reinforced with carbon cloth around the undercarriage retract wells because there are plenty of reports about punching the gear up though the wing. The only other major mod was placing the elevator servo towards the tail - this required cutting a hatch in the top of the fuselage. Good luck with your build.
I reinforced with carbon cloth around the undercarriage retract wells because there are plenty of reports about punching the gear up though the wing. The only other major mod was placing the elevator servo towards the tail - this required cutting a hatch in the top of the fuselage. Good luck with your build.
