Jet Provost

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Robin Woodhead
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Re: Jet Provost

Postby Robin Woodhead » March 23rd, 2014, 12:49 pm

Dave,

How you doing on the 108 tailwheel?
Robin

David Brown
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Re: Jet Provost

Postby David Brown » April 7th, 2014, 6:54 am

Well at last managed to get the JP back into the air after its refit with the fiberglass parts from Chris. For the first flight we went with the original ballast set up but after take off it was evident that she was a tad tail heavy. The aircraft was flyable but not enjoyable with the landing a bit heavy. For the second flight we added 155 g in the form of a 3rd battery in the nose cone and all was back to normal with a very scale like flight and smooth landing, both flights this time were off grass. I will check the C of G position and post it later today with some pics.

Dave

David Brown
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Re: Jet Provost

Postby David Brown » April 10th, 2014, 11:54 am

Took some pics today and checked the c of g which is 125mm behind F4 where the leading edge buts up, this equates to 32% of the root chord, weight is 22.5lb. I was hoping to get some more work done on the finishing but work work is getting in the way. From the pics you can see that there is enough room to move the turbine pump & valves into the nose which would possibly enable me to remove the third battery which I do not need in my case, the last pic shows the tank plumbing with the right hand tank then feeding the pump. I had to pinch the jet tronic's valves out of my Vamp to run the retract's coupled with a Festo high flow restrictor to control the speed as I do not like the jet tronic's pulse control. I had planned to try the Xicoy valves but they did not arrive in time, however they have arrived in the mean time and I have tested them in my TN Vampire and they do the job nicely,easy to program and are a lot cheaper than the jet tronic's. They do not have the pulse control for retract speed so some form of flow control is needed like the Festo unit shown or restrictors in the pipes. The most important job to do before I fly again is to box in the nose gear as the amount of FOD thrown up into the air-frame from the nose wheel is massive, thank's to wren for fitting FOD guards as std to their turbines.

Dave
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David Brown
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Re: Jet Provost

Postby David Brown » April 13th, 2014, 12:02 am

Along with my Vamp the JP had another outing, I sealed of the nose gear well to stop FOD being thrown into the fuselage after the last flights. The JP was more relaxing to fly than the Vamp and although the wind had picked up she coped really well. As with the vamp just the final paint finish to do.

Dave

mark houghton
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Re: Jet Provost

Postby mark houghton » April 26th, 2014, 9:02 pm

Hi David good to hear the JP is going well do you have any setup details ?
Ele rud ail travel any expo ? Flap settings any ele comp needed ? Already
Seen your CG position in an earlier post. Looking forward to seeing it painted
Cheers Mark

Dave Wallace
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Re: Jet Provost

Postby Dave Wallace » April 27th, 2014, 4:45 pm

David any chance of posting a picture please of the underside of the wing so I can see retract install and servo install for flaps and aileron

David Brown
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Re: Jet Provost

Postby David Brown » April 28th, 2014, 6:04 am

Hi Mark, regarding the flap setting, there is none. Whether full or part flap nothing changes on mine. I will measure the throws later this week when I put it back together after painting.
Dave I will look to see what pics I have.

Dave

David Brown
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Re: Jet Provost

Postby David Brown » April 28th, 2014, 7:13 am

Hi Dave, I have checked all of my pictures and I am amazed that I do not have any showing the bottom of the wing with retracts or servo boxes. For the retracts I made up a fame using two rails for the retracts & 3 spacers the width of the cut out which I think is 100 mm wide and deeper than needed for the wing section. After fitting the retracts I then slid the frame in the wing setting the rails 3 mm in from the bottom skin so that the retracts fitted flush with the bottom skin. I then marked the top profile for cutting. I am not sure if these parts are supplied with the kit as oversize to do this. I wanted to attached a couple of rough sketches and ballpark dimensions of where I fitted servo boxes in the wing but the scanned file is too large. Send me your e-mail address and I will send them to you, you can call me on 07968254056 if you need more info.

Dave

mark houghton
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Re: Jet Provost

Postby mark houghton » April 28th, 2014, 8:51 pm

Hi Dave thanks for the reply I have txt you with my email address if you would't mind forwarding any photos you may have to help out with this build
Cheers Mark

David Brown
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Re: Jet Provost

Postby David Brown » May 30th, 2014, 12:46 pm

Its stopped raining at last so got on with painting the JP.

Dave
Attachments
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David Brown
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Re: Jet Provost

Postby David Brown » June 1st, 2014, 7:32 pm

Some more pics, picked up some decal's etc to finish it off while at longmarston show. Will update when done.

Dave
Attachments
JP paint3 001.JPG
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Dave Wallace
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Re: Jet Provost

Postby Dave Wallace » June 15th, 2014, 5:38 pm

Could you possibly post a picture of your fitted fiberglass air intakes from the underneath please and also one from the front

Dave Wallace
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Re: Jet Provost

Postby Dave Wallace » June 15th, 2014, 5:40 pm

Forget the front view just the underneath if possible thanks

David Brown
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Re: Jet Provost

Postby David Brown » June 16th, 2014, 7:14 am

I just butted them up to the flat surface & glued them on with Hysol and run a fillet around the joint. Where they stood off at the front I filled with balsa to make good.

Dave
Attachments
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David Brown
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Re: Jet Provost

Postby David Brown » July 2nd, 2014, 5:19 pm

First flight yesterday in its color scheme. I had a fuel problem so only got one flight as I have had to remove all tanks & clean out the system.

Dave
Attachments
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David Brown
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Re: Jet Provost

Postby David Brown » September 14th, 2014, 8:17 am

Following the JP's last outing I have not had the opportunity to fly here until yesterday, With new fuel and clean tanks she performed perfectly and I am still amazed how much power is developed from the wren 70 down the 900 mm jet tube, most of the flight's were at half throttle or less. Steve Foxon who until yesterday had not flown a jet before had a time on the sticks and was amazed how smooth and easy she flew with no vices so it was a good day all round.
Dave

Richard scarbrough
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Re: Jet Provost

Postby Richard scarbrough » December 16th, 2014, 8:28 pm

Well done Dave.

David Brown
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Re: Jet Provost

Postby David Brown » February 20th, 2015, 4:49 pm

Well a new season is just around the corner and I have been looking at getting the JP checked over ready to go, I have its big brother nearly ready so I am looking forward to flying them both. I have just checked my all up weight with about 1 liter of fuel in and it is 26 lb so in the finishing process it has gained a few lb. I have been asked by other members building this aircraft about what throws I use on the surfaces which are.
20 mm up & down on the elevator on high rates and 12 mm on low rates, the rudder is 50 mm each way. Ailerons are 15 mm up & 12 mm down on high rates and 12 mm up & 10 mm down on low rates. both elevator & ailerons are set at 20% expo.

I am looking forward to seeing some of the other JP fly this season
Dave

graham trever
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Re: Jet Provost

Postby graham trever » February 22nd, 2015, 1:00 pm

Hi Dave
I was going to ask about surfave travel but thats now in print so shuld be sorted soon.Model is getting put in primer right now and a bit of rubbing down,should be fitting out soon as will be testing in primer.A previous post mentioned balance at 125mm . I am hoping for many hours out of this model.Will be doing alot of servo checks after my last builds short life.
onwards and upwards.

Graham

chris willis
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Re: Jet Provost

Postby chris willis » February 22nd, 2015, 1:54 pm

Nice to hear you are nearly there Graham, there's a few nearly done now, here's one built by David Wallace, a fine example indeed.

image.jpg
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