sasktag

I was wondering if anyone has converted a JHH F4 to turbine power. I have the ducted fan version and now have a wren 54. It would be my first turbine powered aircraft. Any thoughts?

scale dail

My Feedback: (8)

I had to reply to this! I am converting a JHH F-4 to turb. power. since my Byron A-4 crashed I moved up the schedule of working on it. it will be powered by a Jetcat P-60. I have to talk to Tam about a tailpipe.

kingair41

My Feedback: (13)

I was looking at the JHH f-4 as a ducted fan model. What do think of this kit. What power/fan combo did you use. I fly from grass. How will this aircraft perform on take off. Any comments about this plane would be appreciated. Thanks.

A7Bldr

My Feedback: (40)

I had the this plane for awhile and then sold it to a friend who flies it alot. I feel the Wren would be a perfect match, with out a bypass.
I would consider doing a belly drop tank to carry much of the fuel, too.

Jim

sasktag

kingair41
I only flew mine a couple of times. Our grass strip was too short to get airborn. I was using the dynamax fan with an old 65 rossi. I always wanted to go to a 91 for more power but saved the cash and instead built a wren 54. The 2 flights that I had were further complicated by some other issues so I didn't get a good feel for how it flew.
Scale Dail
I appriciate if you could let me know what Tam has to say about a pipe, Thanks.

Chris Smith

My Feedback: (2)

Gents,

Being another owner of a 12 pound turbine, I encourage you to explore the idea. Email JHH and get their opinion.

I'm anxious to hear about the JHH F-4 with a turbine. I have a T-500. The JHH jets are all really good, but it seems most would be over powered with Wren 54 size motors. I don't know about the F-4 though. The bigger the turbine, the higher the wing loading due to fuel engine weight etc. There is a point when extra thrust can cause more handling problems than it solves.
There is no doubt a bunch of jet guys (most?) can't get enough thrust. But we know there is a point of diminishing return.

I'm not suggesting the Wren 54 is too big, I don't know. But you know how it goes. As soon as someone talks Wren 54 someone else suggests a P70. Then someone else says "no, no a P80" etc, etc.

Since there are not that many neat models for 12 pound turbines, and none I've heard of the F-4, any attempts at turbinizing this model will probably be of great interest to some of us. It would be helpful if Larry or Chris had the time and resources to test all of their models with turbines and tell us what they think, but that is probably unrealistic.

If you dig thru RCU for threads on various JHH aircraft you see the same debate over and over. What power to use. Even the most experienced fellas don't agree. This is not just an issue with JHH models, but I believe the smaller models will suffer more with the wrong power choices. A little jet with a high wing-loading might need as much runway as a bigger jet. Being smaller, if they fly like a rocket, you've got to really concentrate. The only benefit is a cheaper smoking hole. However, match the airframe with a proven sized engine and a small model could become your favorite flyer. Ask Larry about an MW44 equipped JHH F-86 for example. Ask our UK friends about the MW44/L39 combo.

Sorry, I've helped no one with what I've written here except to say the an F-4 that size is well worth the effort to try a turbine. And it may be the Wren 54 is perfect (I hope so). Unless Larry says don't do it due to some reason such as the structure etc, press on. Who knows, you may discover the next King Cat.

Cheers,
CJ

JetsRC

I just bought an F-4 from JHH, still waiting for the final parts though. Acording to Larry and Chris the wren 54 is a perferct match for the F-4. It seems that this kit is a bit larger than the other ones they have, for other kits they recomend the wren 44. Anyway I would personally suggest you call Larry or send an email if you have any doubts, they are allways there to answer any questions.

sasktag

I took a few measurments of my JJH F4. Here are the details. Span 44", length 67". Weight of mine painted and trimmed, without engine, pipe, fan unit, or tail ducting, without any batteries or receiver, but including 2 sullivan saddle tanks, landing gear (rohm retracts),and air system, wheels, 6 standard servos and 2 mini servos is 7 3/4 lbs.
My wren 54 weighs 1 3/4 pounds not including support equipment (fuel pump, battery, ecu etc.) or thrust tube. I believe the projected weight of the ducted fan version with a 91/dynamax combo was about 12 1/2 lbs. I don't think the turbine version would be a whole lot more than that so the wing loading shouldn't change any significant amount. Just my thoughts. I plan on contacting JHH before proceding with this project.

scale dail

My Feedback: (8)

I got my tailpipe from Tam today! it is a thing of beauty. I asked for one that is a little shorter than others are using because I want to mount the Jetcat P-60 a little further back to get standard fuel tanks nearer the C.G. conformal fuel tanks are still beyond my technology. 2- 11oz. saddle tanks and 2-12oz. tanks and the UAT. about 50oz. total fuel load.

sasktag

Wow that's a nice looking pipe. What is the overall length, and how close to the pipe are you mounting the engine.

PhilLin

sasktag, Scale Dail, can you please let me know how long it took for your kits to arrive at your door, from day you placed your firm orders? I have placed mine & can't wait to get my hands on it. Thanks in advance.


Phil

sasktag

Phillin, I bought mine off a friend who had it partially built so I couldn't tell you how long it will take to arrive. sorry.

Wayne22

My Feedback: (2)

Hey neighbour!! I'm going to a hobby/trade show in Feb and JHH has already booked. I plan to ask them a lot of questions about turbinizing their fleet. I had talked to Larry a lot previously, but that was before I got into turbines myself....

razorice79

My Feedback: (1)

that wait sounds about right.. i have a jhh mirage thats weighs about 12.5-13.5 lbs.. its 69 inchs long and 45 inch wingspan with the dynamax/os91, and 9 servos...rohm retracts, 3 tanks..etc.. wren 54 would be a fine match in my opinion.. i was thinking about throwing a turbine in this jet but seeing how mines like 20 years old i would probly be better off keeping the mirage DF and buying a NEW jet made for turbine purposes from the get go...I only got nylon wing nuts holding this wing to fuselage.. will wingnuts be good enough for a turbine high -g load? i doubt it...

-razor

scale dail

My Feedback: (8)

The tailpipe I ordered is 12'' long. the P-60 will be about 3/4'' in front of the pipe. I still have to figure out if the engine will be mounted to the sides or the bottom on the wing.

Wayne22

My Feedback: (2)

The AV8R uses nylon wing bolts. I woulda thought the same, but with all the AV8R's that are flying, we certainly would have heard about it, if this was a problem....