TOPIC: Profile F-15 Eagle for L-2

Hi Guys,

Luke, a fellow member of the prestigious Peterboro Model Flying Club lives quite close to RAF Lakenheath. Not unexpectedly, there has been quite a lot of full size jet activity lately, and Luke has got used to seeing, and hearing F-16's, F-35's and F-15's close up.

He wonderd if small models of these could be made for Rapier/TSP power.

The answer is if course, 'yes', though the F-35 would be quite tricky. So Luke and I thought it best (Luke is new to scale jet modelling) to start with a profile, or rather, semi profile F-15 Eagle. Luke rather fancied modelling one in Lakenheath colours:





This will look great in the sky; only hope the 'stealth' type colours make it difficult to find in long grass!

Our task is made easier because West Wings made a rather nice catapult 'F-15' some years ago, and we saw an adaptation of one of these for Rapier L-2 at Old Warden in 2015:





It was flown, I think, by the estimable Chris Richards, but neither I (nor Chris) remember if he got a complete flight out of it!

Catapult gliders need a different set up to Jetex models, so some thought is required as to the best way to adapt this design.

Tbe West Wings F-15 hasn't been made for some years now; fortunately luke managed to find a complete kit on-line:





This arrived gratifyingly quickly, and scans of the (really rather nice) balsa parts were then made:



Above, this is a good basis for a model, and the scans of the parts can easily be modified using a graphics program.

Which is what Howard Metcalfe, long time F-15 aficiando has started to do:



Note that the nose is now separate and the motor can now be mounted in the middle.

Howard writes:
The engine pods extend to the front of the intakes as shown in red
The centre body provides provide a hand grip for easier launching.
The only questions I have are:
Double thickness for the side pods as well as the nose?
I guess there needs to be separate elevators s to get some decalage?
Wingspan around 14/15 inches?
Last question, can I have one too?????
Oh, extra question, perhaps it would look OK in grey Depron and a bit of paint?
Fun stuff, Howard"

As Howard says, this is a fun project and Luke and I hope to get cracking on it next week.

Below is progress so far. As my usual practice,I'm making only one template first. When this is done and checked, the other template is created as a simple mirror image and only the lettering, etc, needs changing.



The central midddle fuselage pod will be 'fleshed out (about 1cm thickness) but rounding will be kept to a minimum. The canopy will be bluish as a contrast to the grey. Qute a lot of the rather fussy West Wings detail will also go.

More later .....

Some progress made:



I'm inclined to leave it at that for the first prototype and make corrections and refinements after making (and flying) the first prototypes!

OK, a template was rinted on lightweight paper (60 gsm) the parts roughly cut out, sprayed with repositional photo mount ad attached to balsa sheet. Light balsa was used for the wings (2mm balsa), med-hard for the nose and light for al the others. Tail and fins are quarter-grain. Duplicate bits are now cut out:



Everything seems to fit together, so that's good.

Still need to think about wing and tailplane fixing so we have some necessary 'decalage'.

Just a little progress with the F-15. Talking things through with Luke, we decided the best way, or at least one way, to provide 'decalage was to add 1.5 mm doubles to the edges of the middle section.



Cut outs for the wings and tail enable a 'key' for gluing. Trying this out it looked like this:



The wing is 3/32" (2mm) balsa shaped to an aerofoil; the tailplane 1/16" (1.5 mm) is also shaped. Gluing the front of the wing flush with the middle section and the trailing edge flush with the bottom of the middle section, and gluing the leading edge of the tailplane flush with the botton of the middle section (and its trailing edge flush with the top, etc) gives about 2.5-3.0 degrees difference, which should be just fine. Problem solved!

So things seemed to be going well. I then made a big mistake: comparing the West Wings design with proper 3-views taken from my just-arrived copy of "Aircraft Archive Post War Jets vol 3.







Actually, the West Wings design isn't too bad, but showed the moment arm (distance between the wing trailing edge and the leading edge) was almost half what it should be.

Fortunately, this was easily corrected by the expedient of moving the wing forward by 6 mm.

These sorts of minor problems are endemic to building the first prototype, of course, unless you are an expert in CAD!

Next job is to tissue cover the wings and tail.

More later ....