Jet Provost

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David Brown
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Jet Provost

Postby David Brown » August 8th, 2013, 6:35 am

Thought I would start a new Thread for the Provost. Having purchased an old 1/4 scale Jetwelt Provost I decided I would prefer a smaller version to fly first. I had all the 3 views and drawings and after building Chris's Yak 50 thought it would suit his style of design, so we agreed on 1/6 scale and Chris produced the drawings, I had the wings and tail surfaces cut in foam & veneered, picked up some wood from Slec and within a couple of days had some thing that looked like a Provost. Wren had made up a twin wall jet tube for me at 900mm long and the fuzz was assembled around it. We mounted the turbine (Wren 70) and fired it up, with an infa red heat gun we measured the jet pipe temp and were surprised how cool it kept. At best on idle the outer pipe reached 34 C and 22 C at full throttle, we could not measure loss of thrust if any but it certainly seemed to have enough push. The wings have 3 dihedral braces, one either side of the retracts & one nearer the leading edge, I have chosen to use air retracts to keep the weight down on this one. Tail surfaces are foam veneer with the elevator servo's fitted in the tailplane, Hitec thin wing servo HS-7715TH 3.2kg @ 6V 3.9 @ 7.4V and only 20g each, the rudder is to be closed loop. As with the vamp keeping the tail as light as poss is the goal to keep ballast to a min. As stated in the Vamp Thread this is not a full scale model, we have altered things like the intakes to make molding of glass parts easier and cut down build time for the builder, the outline is true to the MK5/Strikemaster with the pointier nose. The whole top from the nose to the un-sheeted part of the fuzz is to be removable for easy access to all inside and is to be a fiberglass molding as with the tip tanks nose cone and air intakes. Will post more later when I get chance to work on it again.

Dave
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mark houghton
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Re: Jet Provost

Postby mark houghton » September 23rd, 2013, 1:33 pm

Hi David have you had any progress on the Provest

David Brown
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Re: Jet Provost

Postby David Brown » September 23rd, 2013, 3:46 pm

No not yet, too busy with work work. Should start on it next month.

Dave

David Brown
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Re: Jet Provost

Postby David Brown » October 26th, 2013, 1:03 pm

Hi Mark had a few hrs on the Provost this week and its coming along quite quick, all surfaces hinged and servo mounts fitted, waiting for some more of the thin wing servo's to arrive to do all the linkages, retracts and oleo's done. Next job is the tanks and glassing after fitting the fin and a final rub down, got some tip tanks off the net which are not fully correct but will do for the prototype and really finish it off . Camera playing up so can't do pics yet, will post as soon as I sort it.

Dave

David Brown
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Re: Jet Provost

Postby David Brown » November 8th, 2013, 6:06 pm

Had a few more hrs on the provost and its getting there, all glassed and in primer now. Still under 20lb projected weight. I will be taking it along to the Wren open day on Sunday.

Dave

Ken Bones
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Re: Jet Provost

Postby Ken Bones » November 8th, 2013, 10:06 pm

Nice one Dave, keep going. Looking fwd seeing this one.
Ken.

David Brown
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Re: Jet Provost

Postby David Brown » November 11th, 2013, 8:02 am

Thanks Ken, we had a good day at Wren yesterday. We ran the JP turbine with and without the canopy cover and all was well with no temp problems, just the fuel tanks and control surfaces to finish off and we are ready to test fly. I have fitted a servo on the rudder instead of closed loop to make installation easier and we are still on target to be under 20lb balanced, it weighs 17.5lb at present. I will have to talk nicely with our chairman to use Woodford in a couple of weeks time weather permitting for the test flight.

Dave
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David Brown
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Re: Jet Provost

Postby David Brown » November 12th, 2013, 9:56 am

The elevator servo's arrived yesterday so I can now finish the flying surfaces and do the final balance. Paul at Kingfisher is making the fuel tanks this week for me and they should hold about 2.5 litre's, these go on the CofG so they won't effect the balance when fitted.I am also playing about with the air tanks & bubble trap to get things as far forward as possible, because it is the prototype I have 2 long studs going through F1-F2 to hold on the nose cone which stop me putting the bubble trap in between them under the pump tray and that is 8 ounces to move forward, if needed I will change the nose cone mounting method as I do not want to add any balast if possible. If more fuel capacity is needed or a smoke oil tank is needed then there is space between F3-F4 under the starter motor for at least another litre .

Dave
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SimonBurch
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Re: Jet Provost

Postby SimonBurch » November 12th, 2013, 11:14 am

Dave,

It's great to see more scratch built jets appearing. To be honest, I just can't afford the composite versions so plan built stuff is the way forward. Could I ask if there are plans to sell plans for this model? I think it would be popular.

Thanks for all the build photo's, great to watch her coming together.

Cheers,

Simon

David Brown
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Re: Jet Provost

Postby David Brown » November 12th, 2013, 12:20 pm

Hi Simon, the Jet is to be kitted by Chris Willis of Willis Warbirds, and should be available early next year if all test flights go to plan. As with all of Chris's kits it will also be available through Kingfisher Aviation who supply the retracts for it.

Dave

SimonBurch
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Re: Jet Provost

Postby SimonBurch » November 12th, 2013, 1:24 pm

Are you planning to tackle any other jets? I think there is a massive gap in the market for this sort of thing. Guess I will have to be patient then !!

Cheers,
Simon

David Brown
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Re: Jet Provost

Postby David Brown » November 12th, 2013, 5:15 pm

Paul at Kingfisher has a new built up jet he is launching called the Raptor, a bit hawk like for turbines up to 140N. Yes we are looking for other less modeled jets to do and possibly a 1/4 JP as a built up kit. For a twin I am looking at the Canberra but that is a while off.

Dave

David Brown
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Re: Jet Provost

Postby David Brown » November 16th, 2013, 8:12 am

Nearly there now, fitted nose leg & steering setup same as the Vampire. the nose wheel should retract forward but so as not to cut up the nose cone (to be used as plug for fiber glass one) I retracted it backward. I moved the bubble trap onto F1 as mentioned earlier. So balancing this time with 3 off 2200 lipo's in the nose at 30% it weighed 19.7lb with no added lead. With the fuel tanks it will push it over the 20lb target but there is a bout 1 to 1.5lb in blue foam in the cockpit,nose & side pods that won't be there in the finished kit so I am pleased with the outcome, for comparison Tony's Vamp weighed 23lb with 2.25lb of lead in the nose ( both are 1/6th scale).

Dave
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Ken Bones
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Re: Jet Provost

Postby Ken Bones » November 17th, 2013, 12:19 am

Test flights soon then, good luck.

graham trever
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Re: Jet Provost

Postby graham trever » November 20th, 2013, 3:09 pm

Hi Dave

Wishing you every success with the test flights as I think it is looking very good.Very keen to get started on one of these.

best regards

graham
WMFC

David Brown
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Re: Jet Provost

Postby David Brown » November 22nd, 2013, 3:01 pm

Hi Graham, no test this weekend, the tanks are not finished yet and its a great weekend. I have been working on my Meister 1/4 Zero while I'm waiting for them, I started this in Jan 2011.

Dave
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David Brown
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Re: Jet Provost

Postby David Brown » December 2nd, 2013, 9:16 am

Yesterday was the day of the test flight and what a day we had. Thanks to our chairman Dave we were allowed to use Woodford for the testing and after a marathon Saturday & an early start Sunday to finish off all the little jobs and fit the fuel tanks she was ready to go. On arrival at Woodford we set up the JP and tested out the retracts etc only to find we had an air leak on the brakes which was not there at home, after fueling up I took her out for taxi trials and was happy with the ground handling. This is where I chickened out and asked Dave to do the test flying, he agreed and suggested doing a few high speed taxi runs to see if she would lift off, next minute she was in the air on her first flight, looking every part a JP in the air. Slow speed handling was fantastic with no hint of stall and rock solid in flight, I had a couple of minutes on the sticks then handed back to Dave to land, half flap was used with no trim change and she glided down on finals as smooth as you can get. For the second flight Dave put in half flap for take off making it more scale like, rolls loops, high speed passes all done with ease, again I had a couple of min's on the sticks then back to Dave who put full flap in for the landing, again no trim change but a slower decent was achieved and another greaser landing. The third flight was as the second but I just sat back and watched Dave enjoy putting the JP through its paces.
The Wren 70 had more than enough power and was a real miser on fuel, all 3 tanks hold a total of 2.2 liters of fuel but I only filled the 2 side tanks which hold 1.6 liters between them, after 5 mins flying she still had 3/4 of one tank left so 8-10 mins is possible. For me the slow speed handling was the high point of the flights so for me a bigger turbine is not needed, I would say it would fly happily on a Wren 54 as she only weighs just over 20lb dry. Now its up to Chris at Willis Warbirds to get it kitted in the new year. Thanks go to Dave for test flying, Paul at Kingfisher for doing the tanks, Paul from Wren for Jet tube & turbine settings, Chris for putting my idea's on paper and a special thanks John & Steve from Catton for help & moral support during the build. Dave Parry has taken some video on his phone, I will see if I can upload it ??.

A very happy Dave
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David Brown
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Re: Jet Provost

Postby David Brown » December 2nd, 2013, 11:53 am

The flights are on youtube WP 20131201 008 & WP 20131201 006

http://www.youtube.com/watch?v=aABnwp8pZX4
http://www.youtube.com/watch?v=Iry_i90f0X0

Dave

stewart clifford
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Re: Jet Provost

Postby stewart clifford » December 2nd, 2013, 3:50 pm

Nice one David, another successful Willis Warbirds design.

Alan Cantwell 1131
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Re: Jet Provost

Postby Alan Cantwell 1131 » December 2nd, 2013, 5:49 pm

Glad she maidened well, wish i had gone now!!! looks great, well done


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