Thought you guys may like to see my latest jet model.
It was started many years ago but due to the very poor quality of the fuz moulding it has taken years to finish. It is so old that I started the build to take the original JPX 240 turbine. It was finished last week and now sports an AMT Mercury. The model is built from a Ziroli plan and to save embaresment I will not name the manufacturer of the fuz. Wings and tail are all built up and the finish is glass cloth and G4 resin. Model weighs 20 lbs which is 2 lbs less than the quoted weight for the ducted fan version shown on the plans. A home made fiberglass fuel tank holds 2.6 litres of fuel and the model is very scalelike flying around at 1/3 to 1/2 throttle. Take off last weekend on wet grass was no more than 30m and there was no wind. It flew straight with no trim problems at all.

Very nice. I have to get started on mine as well. Great job!!!
Tommy

Tommy
A few points that may help you.
I used the Robart retracts and they work very well. You do however need to modify the nose gear mounting from the angle shown on the plan to get the wheel inside the fuz. I used Eurokit wheels and brakes and had to change the bushes in the wheels as the Robart axles are 1/4" and the Eurokit wheels are 6mm.
Don't know if you intend using the fiberglass fuz or not but if you do, you should make the rear former that goes up infront of the tailplane out of good quality ply as this carries all of the twisting loads from the tailplane. I would also suggest glassing it into the fuz with some tape. Mine broke some of the glue join during test flights. Luckly it is easy to repair through the tailpipe opening.
Hope you have fun as the model flies very well.

John

I am going to be using a fiberglass fuse made up by a guy in Thailand. It is very good quality and about the same size and dimensions as the Ziroli. The overall size and weight is the same. What thrust rating is your turbine? Where is it located? I was planning on going for the light version and using a 14 pounder, trying to keep it as simple as the RObart Ziroli model which I saw flying last summer. It was very realistic and seems to have great characteristics. I have a set of Century Jet gear, which I plan to use.
More pics if you got them....
Tommy

I have an AMT Mercury turbine in mine, not the HP type, and it produces about 8.5kg of thrust. This is more than enough and the take off on wet grass is no more than 30m in nil wind conditions. The turbine is located with the front mounting strap just infront of the former at the rear of the main gear opening. I used the Ziroli intake ducts and moulded a fueltank to sit between the inlet ducts.
I will take some pictures of the installation tonight and post them tomorrow.

John

Looks great Jon,

The wood shoud arrive today for mine today.
I'm building the all wood version.
Did you need any nose weight with the engine mounted forward like you did?
I'll be using a Simjet 1700 which shouold weigh about the same as your engine.
What did you use for a tailpipe? How long is it?
More pictures of the installation would be great.

Pete,
The completed one picteured here belongs to John. Mine is still in the box, so to speak. But I am sure he will welcome your comments and answer your questions.
Tommy

Thanks Tommy, I corrected it.

Pictures of the installation below. Feel free to post any questions you have and I will try and answer.

Try again with the pictures !!!

Thanks for the pictures John.

Hey doc, how ya doing. Just thought i would tell you. I checked my Z plans against the model. The dimensions are everso different. The wing cores dont match up, you have to blow your Z plans up to fit by 1/8 inch no biggie though. Graduate my undergrad ground course tomorrow, top of class. Later man, Nick

Congrats Nick. We checked our plans as well, and found just a slight difference at the root. No biggie though, it should be fine.
Tommy

My wing roots did not fit either. Got them to line up as best I could with the top surface and then made up the difference with lightweight filler on top of the wing sheeting. Don't look to closly at the underside though !!!! Make sure if you take this route that you do not change the wing incidence though.
In answer to the question from Pete S-RCU about the tailpipe. I used the design that was explained in RCJI in the artical by John Wright. It was written around the Wren 54 but gave dimensions for other motors as well. I just scaled up the dimensions to suit the AMT Mercury. I did make a sliding mount so that I could adjust the distance from the motor to the mouth of the pipe and found that it did make a difference to the thrust. Thrust is now up on a bare motor...and it sounds good as well.

John