Jet Provost Another Late Starter Build

[Mark Kettle 1]

Jp body coming together.

Edited By Mark Kettle 1 on 29/05/2014 20:33:29

[Mark Kettle 1]

That's took 60 grams of glue

[Mark Kettle 1]

Wing foam patterns - spars - before sections cut.

made a little jig to help to cut spars in 6 mm from the edge.

[Mark Kettle 1]

Notice curve / angle on wing foam? This drawing will explain.

[Mark Kettle 1]

I glue / attach bowden cable to the edge of the wing sections to unable smooth transition of hot wire whilst cut the foam.

cut on this table

[Mark Kettle 1]

Section mid -way point like R2 before LE sanded.

[Mark Kettle 1]

Made some sanders 'Special Sanders' from rain guttering and cut down plastic pipe, stuck rough grade with contact adhesive to the inside, can turn square foam to round.

[Mark Kettle 1]

Body shape time - been made a bit easier with the use of the sanders. I cut off about 12 mm square corner off with the knife all fours sides and set too with shaping.

Basic Body shape

Tailplane seat area

[Mark Kettle 1]

Inner keel and outer body part.

taken from the rear

[Mark Kettle 1]

The Decalage set-up as always raises a concern when I do a build, balsa and ply a material I can draw on to get the angles correct etc, etc, epp foam is a lot harder to mark-out.

So to help get the desired 1-1.5 degree of positive incidence on the wing from the elevator position - geometric decalage.

I've made a pattern / tool which is pinned on the side after lining up with the tailplane seat with both fuselage and pattern resting on the work bench, then the aperture for the wing is cut out with a vertical hot-wire cutter.

Edited By Mark Kettle 1 on 30/05/2014 11:11:54

[Peter Garsden]

Looks really interesting build Mark.

I was considering doing a lost fibreglass and foam wing version. Paul Janssen has plan of such a version, but he says it is no lightweight. That is the problem with fibreglass.

This looks really interesting and no doubt wiil end up very lightweight.

[Mark Kettle 1]

Cheers for the comments Peter.

Done lots of other fitting and pattern tweaking on the JP. One thing I didn't have was a tailpipe and that curved shape at the rear end, so this evening been working on a small 45 mm depth part to make amends in the tailpipe area.

See photos : -

Edited By Mark Kettle 1 on 13/06/2014 22:15:23

[Mark Kettle 1]

Pattern / jig - to cut body taper parts front and back of cockpit area both top and bottom. This is the taper in plan view for wide to narrow.

[Mark Kettle 1]

Torque Rods :-

Copying Matt Jones choice of torque rods - 2.4 mm steel with 2 mm extenders on servo end.

Also to keep it simple placing rods in mid section of the wing in the epp foam trailing edge -whilst it makes its way to the aileron.

How I put the groove / slot is in the foam edge - at 10 mm wide and 340 mm long is held flat against the hot wire cutting table with a old kitchen tile.

Adjusting the hot wire to 5 mm off the base - it has screws either end of the bow and weighted down to the bench to allow me to do this - I then bring the work up to the wire just melting 1-2 mm in - pull work (trailing edge) back out again.

Then I bring the wire up with one whole turn on both side screws - bring the work back in for another melt - again pull out.

Now I go down with the wire back to 5 mm then down one whole turn on the screws and back in for another melt, being careful not to go in to far . to deep would make the slot useless and not give radial movement.

I find the rod works in the foam like with a 340 mm bearing, when I glue back on the trailing edge sometimes a little glue gets on the rod - however just a little twisting for a couple of minutes soon free's it off.

See the pictures :

Edited By Mark Kettle 1 on 15/06/2014 19:39:45