Thursday 28 February 2013

AMT KC-135 to 707-138 conversion


I had a half built AMT EC-135 model that was looking quite sad, considering my attempt at putting it together was dismal to say the least. The wings were not straight, the gluing really bad, and it had gaps galore.  So for the last 15 years it languished in the corner of the workshop worthy only of the trash. It seemed such a shame to throw it away...

So "heck...", I thought, "...don't throw it, convert it." I decided I will convert it into a 707-138!

Qantas operated the 707-138 and the 707-138B. The 138B was a 'souped' up version, with better engines and aerodynamics.  I won't go into the details, there are many people out there who are experts on such matters, so you'll have to google it!

Starting out the conversion
Due to the condition of the model,  my approach was relaxed and I felt I could be quite liberal in cutting it up.  In some respects it is an experiment out of boredom.  It was mostly complete, had engines, but no gear. The gear had been ripped off some years before.

Obviously I wanted the outcome of the finished product to be good enough for my cabinet, but this was an experiment. If I stuffed up I would just throw it away.  In fact, at one point I toyed with the idea of building a"what if"' KC-135 by re-locating the wings to the top of the fuselage, much like a C-141 but I soon canned that idea because I'd likely end up wasting modelling materials.

As some of you are well aware a KC-135 is not a 707. They are completely different machines, so technically it's not possible to get a 707 from one. But hey this is modelling and anything is possible - even a high-wing KC-135!!

Starting the conversion
I located the excellent 707 conversion guide by Jodie Peeler (Jodie is well known in the US Airliner Modelling circles), and got to work. Jodie's guide is comprehensive and provides all the measurements and advice on 707 conversions. For a 707-138, the KC-135 fuselage length is the same, but the wings are located too far forward.  Also, the KC-135 fuse is narrower, so there is no "lobe-crease" that is visible on all 707s (and all later single aisle Boeings).  There are also some other differences but I wasn't worried about those aspects of the conversion yet.

For those that have built AMT's KC-135 you might know about the dreaded "wing-droop" problem.  I was not aware of it when I originally built the model but I sure found out about it. It was part of the reason I abandoned the model. The "droop" leads on to other problems if not rectified (eg no 1 engine pointing 'up') and just makes the model look dumb.  Another problem is the gap for the main wing/fuse joint. The mating surfaces are small and it is difficult to get a nice solid join,  making the whole wing-body assembly weak. So knowing this, the wings had to come off.  The engines I had were the wrong type for my project so they got ripped off too. And the fuselage? Well that had to be split apart.

Easier said than done. Nothing wanted to come off in a hurry, I must have used a ton of glue when I built it.  After a bit of wrenching, I managed to get things apart but not before cracking the left fuselage causing it to buckle, damaging the trailing edges of the wing halves and putting holes in the plastic where the engines were... Oh well I thought, it was stuffed anyway...

Next the I had to make cuts in the fuselage to re-position the wings  Following the suggestions in Jodie's guide, I had to remove a 7mm plug from the aft and insert it forward of the wings.  Doing this meant I had to re-sculpt the aft wing-body fairing sometime a bit later, but that didn't worry me, as there was a fair bit of sculpting to do elsewhere. In addition to this, the top of the fuselage has to be wider than the bottom and eventually a "crease" made down the side.

The razor saw made good work of the cuts and I didn't get too precise about the measurements. I measured a 7mm segment to cut out and proceeded to cut away...