Jet Provost Build by RedBaron

[RedBaron]

Andy, it's just one small thing (but interesting).

Maybe it is like all those beautiful ancient Egyptian buildings and monuments, they were always left slightly incomplete or with a small error in order not to offend the gods by being too perfect.

Best wishes,

RedBaron

[RedBaron]

11/02/2014 - I did not make any progress this weekend or today, but I did keep popping into the hangar to contemplate the rear fuselage and develop my work list to tackle this:

Before I finish the top and bottom sheeting I need to fix the lengths of the elevator and rudder snakes, install their supports finalise the exit point of the rudder snake.

Then there is the fiddly block work to get the rear end looking neat and also the jet orifice. The fin parts when glued together will need to be removable for final shaping of the rear parts. I suspect that the very rear end will need to be painted, I can't really see getting film covering to work well here and look nice.

I can begin to feel the work list coming together but have not written it down yet. It is a job for tomorrow morning, to get it into my NoteBook.

One matter I can't make my mind up on yet is which hinging method to use for the elevators, maybe Andy and those who built the JP earlier might tell us which methods they used. Having had my first contact with indoor building and flying I am somewhat taken with glue-line hinging for small models and I think this will do well for the rudder. This method has been just fine on my Phase 3 U-2.

[Andy Blackburn]

Ok, I've checked the drawing and it appears that as drawn, the hole for the wing dowel in F4 is indeed slightly too high, by about one sixth of a millimetre - the bottom edge of the hole should be 11.27 mm from the bottom of the former; actually, it'll probably be a little more than 1/6 mm because of the (double) thickness of covering material.

The procedure for finding where the dowel should go is:

1. find the root rib, go to the front view and project the wing top and bottom surfaces in to the centreline
2. find the difference between the position of R1 and R2 (which is what's drawn at the fuselage side)
3. copy the root rib to the right place on the side view (remembering to allow for the thickness of the wing skin)
4. project the slot for the wing dowel forward onto F4.

This works OK provided that the front view has the wing in the right place, but because I'd been experimenting with several different thickness airfoils before settling on one, the front view was slightly out; Mea Culpa .

However, having said all that, if the cut parts match the plan the difference is so small that the best thing to do is probably just to elongate the hole with a file...

[RedBaron]

Thanks Andy very interesting.

I had to make a slightly bigger adjustment, but I have now checked the wing and tailplane incidences and they are just fine.

RedBaron

[Andy Blackburn]

Posted by RedBaron on 11/02/2014 23:32:22:

...I suspect that the very rear end will need to be painted, I can't really see getting film covering to work well here and look nice.

It *is* possible to use film at the rear end (around the jet pipe) which is what I did, it works OK if you cover before assembly. But painting might be easier, depends what you're used to I guess.

One matter I can't make my mind up on yet is which hinging method to use for the elevators, maybe Andy and those who built the JP earlier might tell us which methods they used.

I just used mylar hinges fixed in scalpel-cut slots on the centreline, glued with thin cyano; I've not pinned hinges for years, and as far as I can recall I've never had one come loose. I don't think it matters what you use as long as the hinge gaps are small. And as long as the aileron hinge axis is aligned with the torque rods, obviously.

 

Edited By Andy Blackburn on 12/02/2014 19:02:49

[RedBaron]

13/02/2014 - Are Jet Provosts shy? Prior to starting on the exhaust area I thought that I would look at a few JP rear ends to set the details in my mind. I have just spent some time looking at literally 100s of JP photos and find that they do not like having their afterworks photographed. I really only found three pictures that were helpful, they do show that there are some variation in this section of the aircraft. So depending on the specific aircraft that you have chosen to portray you may want to check the details for yourself.

 

 

Edited By RedBaron on 13/02/2014 15:17:07

[RedBaron]

13/02/2014 My JP afterworks - After applying some more 3/4inch triangular section balsa in the tail plane seat area and some sheet scrap it was time to mark out some of the balsa to be removed and then remove it:

As I am a bit sensitive to dust, I used one of the Gaskin Softbore tools to remove the curved bits a long knife blade helped with the straighter bits and only a small amount of tidying up with a Dremel sanding drum tool was necessary to get the job to this stage. This all went much more quickly than I expected. Now to figure out the most efficient way to do the external shaping.

[RedBaron]

19/02/2014 - JP now shaping up a bit. Progress has been a bit slow recently due to the build of a new indoor GymStar temporarily having got control of the work bench! Also although I seem to have done quite a few hours on the JP nothing seemed to be photo worthy.

Jobs done include finalising the snake lengths and fittings for the rudder and elevator, finishing sheeting the fuselage etc. Also a lot of planing and sanding to get the fuselage just about to it's various profiles.

All of the control work is done so I guess that I now need to shape the fin, rudder and elevator and do the under wing block work and the intake blocks, the cockpit and canopy. Hmm quite a long list.