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Old JHH F-4 airframe conversion

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Old JHH F-4 airframe conversion

Old 03-14-2010, 07:56 PM
  #26  
hyperdyne
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Default RE: Old JHH F-4 airframe conversion

Ravivos, thanks much! I tried to maiden her yesterday but the steering was jacked up (the push-pull cabling was getting hung up). Plus she was really sensitive to steering input. After fixing all that I tried again and it ended up spinning out and going off the runway. I have never seen a plane do a doughnut before! Had to fix a bent gear and found that the dual wheel nose gear was slightly crooked and only engaging one wheel on the ground normally. I think this may have something to do with it. Plus I was (purposefully) quite nose heavy with a full load of fuel, this may have made the issue worse. So back to figuring that out.

Anyway here are a couple pics of my install. This was the first jet I actually built from just a body and a few installed pieces. So it was a learning experience figuring out how to install and fit everything, getting it to balance, etc. Plus there just isnt a lot of others out there with build logs on this plane.

I ended up putting much of the equip in the cockpit area. The biggest decision are the fuel tanks. They will really only fit right in front of the intakes. After much trial and error, I was able to get a dubro 50 oz. + a dubro 16 oz. to stack on top of one another and fit perfectly in the area behind the cockpit. This gives 66 oz of fuel capacity which will be great for a 14 lb turbine!

The UAT and fuel pump are right in front of the fuel tanks. All electronics and gauges are up front.

For CG reasons, I ended up putting the system battery and receiver battery in the engine bay. I am using a 15amp BEC to run all the servos. The retracts are air up/spring down. A simple robarts valve with flow adjustment is what I used. Both air tanks are also in the engine bay underneath. If you can find the small silver robarts tanks these fit perfect in that area. For some reason the white tanks are a tad longer and wont fit without cutting the spar (didnt want to do that). I ended up using a jettronic valve and BVM 2.25" sport wheels and brakes for the mains - they work great (the same one listed for the yellow F-4).

Dry (but with UAT filled) the plane CGs perfectly at the 9" mark. With full load of fuel she is nose heavy but hopefully from what I have heard doesnt change the performance that much. Plus I want to be nose heavy on most of my jets. I also have a CG excel worksheet if you need it (got it from JPO site and filled it in).




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Old 03-14-2010, 10:30 PM
  #27  
scale dail
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Default RE: Old JHH F-4 airframe conversion

Your JHH Phantom looks good!
Mine had a P-60 for power. And at 18 pounds full fuel it was a real pig on the takoff but really got going once off. My best landings were with with the flaps full down and the nose up dragging it it with lots of power. Hey that's scale too! I lost it on a cloudy day a few years ago.
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Old 03-14-2010, 11:04 PM
  #28  
hyperdyne
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Default RE: Old JHH F-4 airframe conversion

scale dail, thanks for the input. Sorry to hear you lost your phantom, it looks top notch in the pics! I like the paint scheme.

Your info on landings helps out, thanks. I am guessing this thing doesnt flare like an F-16, but does it tip stall by dropping a wing or just get mushy? Did you have power on while wheels touched as well?

I am following Larry's advice of 30 deg flaps on takeoff and 60 deg flaps on landing. My bird is also 18 lbs wet, so I hope it will be ok on takeoff. I'll let it roll out as long as I can. Glad to hear someone else has had one of these fly well under turbine power!





Old 03-15-2010, 01:33 AM
  #29  
Ravivos
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Default RE: Old JHH F-4 airframe conversion

Jim, your build looks very good, thank you for the pictures and ideas
have you tried going with a slight tow-in on the main gears? this will surely help her track better.

can you further elaborate on what tail-pipe did you used ?where can i get one? price?

thanks
Old 03-15-2010, 11:00 AM
  #30  
hyperdyne
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Default RE: Old JHH F-4 airframe conversion

I will try and get the pipe info, it was already in the plane when I bought it.

Anyway, your toe-in idea on the mains is great! I will definitely try that. [sm=thumbup.gif]

Old 03-31-2013, 03:41 PM
  #31  
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Default RE: Old JHH F-4 airframe conversion

Hi all,
would like to get this thread up and going again as I've decided to try and proceed with this nice build.

so, i scraped most of the paint off, still needs a lot of elbow grease to get it to the way i want it to look, will then have another primer coat and some bondo (car-kit) to fill up the needed places.
cut the nose, as i plan on building a new E-version nose, unfortunately, Larry from JHH says that it is no longer available for purchase (Thank you Larry for a great communication and help).
removed the old (horrible) fixed horizontal stabilizers, will build a new set of full flying stabs with the correct mechanism.
when i opened up the wing, to much of my amazement, i found no beams nor any structural strengthening spars, lucky me that i didn't try and fly it that way.
will come of with a spar/beams structure so the wing wont fold and the spar structure will also include the landing gear housing.
the upper sheeting (from the inside of the wing) will get a new carbon fiber layout to withstand my not-so-perfect landings.
any thoughts will be more than welcomed.

i do have some questions, especially for those who flew/fly this nice little turbine powered bird -
i bought a used (but in great condition) bifurcated pipe that i think was done by Tam, but i came across a few threads regarding this pipe that it has a high loss and using a 12lbs turbine with this pipe will be a deadly blow to the plane.
as you can see from the pictures, the output nozzle is very small, can anyone comment on this?
if one of you how fly this plane with a 12-14lbs turbine can measure the output nozzle, it would be great.

please feel free to share your thoughts.
Thanks,
Ravivos.
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Old 03-31-2013, 03:43 PM
  #32  
Ravivos
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Default RE: Old JHH F-4 airframe conversion

two more pics of the pipe...


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Old 03-31-2013, 04:18 PM
  #33  
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Default RE: Old JHH F-4 airframe conversion

Great progress Ravivos !
Old 03-31-2013, 09:55 PM
  #34  
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Default RE: Old JHH F-4 airframe conversion

Hyperdyne ,did you ever get to fly your f-4?
Old 04-01-2013, 12:39 PM
  #35  
Ravivos
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Default RE: Old JHH F-4 airframe conversion

well, had some progress today -
cut the front cover with the canopy and fabricated a frame for it,
working on the inside of the fuselage, every former needs to be done separately, as i don't have any information nor drawing for it,
so i just used a piece of cardboard and hacked it away until i got the proper shape, then cut the formers accordingly.

i have two 1.2liter fuel tanks that i want to use, unfortunately the space inside the fuselage is rather restricted and the only place i can locate them is behind the front tray, between the inlets, although it will affect the CoG, hope it won't be too much.

planing on mounting the fuel tanks in a way that the turbine's starter will seat between them, any thoughts about that? any input about the minimum distance between the front of the turbine (compressor) and an external object?

still looking for any input about the pipe...

Ravivos.


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Old 04-01-2013, 12:41 PM
  #36  
Ravivos
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Default RE: Old JHH F-4 airframe conversion


ORIGINAL: i3dm

Great progress Ravivos !
Thanks!
Old 04-02-2013, 08:37 PM
  #37  
Ravivos
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Default RE: Old JHH F-4 airframe conversion

Anyone with a JHH or a yellow F-4 that can comment on the pipe issue?
Old 04-02-2013, 10:44 PM
  #38  
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Default RE: Old JHH F-4 airframe conversion

Ravivos

Maybe this can help you ............   http://www.rcgroups.com/forums/showt...=1431521 

Regards
Dragan
Old 04-03-2013, 11:20 AM
  #39  
Ravivos
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Default RE: Old JHH F-4 airframe conversion

Hi Dragon,
Thanks for the link, it sure was informative, although the pipe that was used on the YA F-4 in your link is a modified bifurcated taken from a different model.
although mine is an original TamJets bifurcated pipe, i've came across some complaints about it been to restrictive or lossy, wonder if there are several version of this pipe and if someone how flies this plane with such pipe can comment on it...

Thanks.
Old 04-18-2013, 02:20 PM
  #40  
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Default RE: Old JHH F-4 airframe conversion

Got some work on the wing,
as i proceed, and the layers of the old paint are slowly peeling away, it seems that the wing is in a rather bad shape, as the previous builder of this plane obviously wasn't thinking of the proper way it should be built/repaired.

so, as i mentioned before, when i opened the center section of the wing i found no beams nor spars to hold the two halves together.
spend some time thinking and decided to build the entire spar structure so it will carry the load of the landing gear (instead of the foam) and will act as a proper spar able to take the abuse of a turbine flying speeds.
i've built the structure that you can see in the picture, which have the plates for the landing gear,
i then implemented it into the wing using a polyurethane glue (Gorilla), which is absolutely perfect for gluing the wooden spars into the foam core.
once it was all align and the wing was leveled, the structure was glued into place and with couple of things in mind -
first - it should be able to withstand my not-so-perfect landings, so the top of the wing will be partially sheeted with a carbon fiber cloth at 90degs, this will provide an excellent top skin strength and will prevent the wing from collapsing on those negative Gs.

once the structure was in place, I cut the wheel wells,
as for the spar and its ability to take the high G turns, I've used a unidirectional carbon fiber tow (10 strands of 12K carbon tow) to create an I-Beam that will prevent the main spar from collapsing and withstand the pulling forces generated on the bottom of the wing at positive G.

there still a lot of work to be done, as i need to design and create every little piece of this flying puzzle.

Thanks.
Ravivos.
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Old 04-19-2013, 05:54 AM
  #41  
Ravivos
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Default RE: Old JHH F-4 airframe conversion

just a quick picture of the top carbon skin glued in place, with some UD tow for strength.

Next thing to do is to build the servos tray on each side of the wing,
i was thinking of building is as one big hatch with two servos attached to it (Aileron and Flap), that will be screwed into place with 6 screws.
any thoughts or ideas?

any input regarding the pipe? perhaps Tam can chime in with his two cents, regarding the exhaust pipe output diameter...

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Old 04-19-2013, 06:06 AM
  #42  
Ravivos
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Default RE: Old JHH F-4 airframe conversion

after reading the threads on RCG regarding the CoG, I've decided to go with a pair of saddle tanks, so i modified the ones i have to me mounted as in the picture,
the turbine will be mounted on a single rail that will be properly secured to the fuselage, just like on a CARF Kangaroo (see pic)

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