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Edit: How do I re-size the images?
After some procrastination and plenty of research help from a number of you (thanks all), I’ve finally gotten started on my KC-135 to 707 conversion. Though the two look similar, the 707 has a wider tube and the wings are moved further back. I’ve been documenting my build to make it easier for others to do the conversion as well in the future.
Step 1: Moving the wings: there are two schools of thought, either remove a donut aft and add one ahead, or move the WBF. I chose the latter, because the former involves resculpting the WBF, which sounds too daunting a task. I used a razor saw (steadied by masking tape) to make vertical cuts between the front of the wing slot and just aft of the KC-135 cargo door and immediately aft of the WBF at the aft end (you want to get right at that limit to minimize the impact of fuselage taper). The removed sections look like this:
AMC provides a convenient cut guide aft in the form of the tanker reinforcement strips. I measured out the .277″ that need removing and it fell right on the second line here (note also the cut right at the WBF):
For the horizontal cut, I scored the panel line above the wing with a hobby knife a few times, going deeper every time until there was a clean cut. After this, I cleaned up the edges and test fit everything.
The next step is adding internal reinforcements to reattach the removed WBF sections:
Once this is done, the internal cargo deck needs to be changed as well so that the landing gear aligns with the new wing position. I glued a piece of sheet styrene to the top edge of the deck, leaving the bit in the middle over the gear well dry. Next, I cut the gear well, removed a .277″ section aft of it, then glued the well aft and the strip forward, and got this:
Following this, I reinforced the upper side by gluing in scrap sprue parts:
Today I’ll try to glue the WBFs back in and get that in the next couple of steps.
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Good job and best of luck with your conversion! I’m sure we’re all watching in anticipation! (at least I am!)
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Me, too!
Most interesting and exciting project!
Good luck to you!
-Harry B.
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Make sure you have an updated KC-135R kit to start with, as it has the extra a/c pack intake part (the original kit didn’t have it). All 707s have dual air cycle machines in the belly. The KC-135A/E/Q/R only has one. Most other USAF C-135 variants have two, as do the French C-135F/FRs.
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Jennings :
Make sure you have an updated KC-135R kit to start with, as it has the extra a/c pack intake part (the original kit didn’t have it). All 707s have dual air cycle machines in the belly. The KC-135A/E/Q/R only has one. Most other USAF C-135 variants have two, as do the French C-135F/FRs.Jennings, I got the KC-135A kit with the single pack, so I’m going to cut and re-sculpt the second intake. The reason I went with this specific kit is that it has the Heller sprues that I am using for the engines in the 707-138B model. I’ve also traded the horizontal stabilizers to the large set with the increased span at the tip.
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After cleaning up all of the cuts, I glued sheet styrene in the fuselage halves with bits of sprue to strengthen and straighten the joins. This is especially important at the back end by the WBF because it helps force the wing section to conform to the taper of the aft fuselage:
Once the styrene is in, the WBFs can be glued back into their new locations further aft, leaving a slightly weird gap at the forward end. My plan for this is to wait until the halves are re-glued, then build up thin strips of styrene in the gap and finish them with putty/sanding, which I’ll have to do plenty of anyway to get rid of the tanker reinforcement strips aft:
Because I’m lazy and don’t like putty/sanding incessantly, I fitted further scrap sprue in the tail underneath the boomer pod gap. When the two halves are glued, I can just slide a sheet of styrene in there and keep some limits on the sanding/puttying. Also visible here is the aft WBF join and the widening strips. To get a 707 from a KC-135, you need to ad .056 inches to the upper lobe, starting at the front of the cargo door and tapering down at about .5 inches (13 mm) from the tailfin (ref/thanks to Jodie). I used 5 strips of .010 that I layered progressively, again to reduce gaps (putty/sanding):
As the fuselage join looms, I’ve painted and built up the flight deck. The tanker kit has a gap for the ladder on the port side, I carved out a section of this part to fill the floor area, hence the seam. It won’t really be visible inside anyway, so I’m not overly worried about it being flush. Also, looking at this picture I realize I need to do a few touch-ups:
Another conversion need mentioned by Jennings was the need for two AC packs. If you got the KC-135A kit (like I did), you’ll need to cut an opening. I used a hobby knife to cut around the side and aft edges, and then bent down the strip in the middle. Once this is done, the sides need to be re-aligned and glued, and the inlet shape needs to be matched with the molded one:
My kit has a pretty seriously warped tailfin, so my next step will be to glue something in there while keeping it on a flat surface to straighten it out a bit.
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The other day I fixed the inlet by gluing a piece of sprue onto the flap that I cut to align it with the bottom of the wing:
I then test fit the major pieces together after painting internals, and will try to get the fuselage together today after some sanding/shaving to improve the fit:
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After the basic test fit, I realized that I would need more alignment tabs due to the widened fuselage, so I cut up some scrap sprue and glued it in place:
Following the tabs, I put the nose gear leg in its well and glued the well to the starboard side. After this was the deck with cockpit, and finally, lead nose weights fixed with epoxy. I realized in retrospect that I added too much, but it’s better than not having enough:
Because the deck is full-length and joins with the lower wing piece as well as the fuselage, I debated which order to assemble them in to minimize risk of mistakes. What I ended up going with is the lower wing piece first, which gave me the chance to glue more reinforcement tabs in, which is important given the weak spot by the WBF. I affixed them using tube glue, then mated the parts and used Tamiya extra thin to join the seams together both and the fore and aft ends:
Finally, I glued the port side of the fuselage onto the rest of it, putting tube glue on the alignment tabs and the cargo deck, then using tape and bands to hold the whole thing together. I realized here that it’s important to use a lot of tube glue to soften the fuselage a bit and force the deck to the sides, otherwise the lower lobe gets wider instead of just the upper one. You can see the widening strips in the top of the fuse here, I made sure to run enough extra-thin down there to bond them all together well. Also visible is the vertical stabilizer. I made the mistake of adding the stinger too early, I advise waiting until just before painting to add it, that way you don’t break it off:
Next up, I filled the gaping hole at the bottom with sheet styrene that I bowed out around these two sprue bits to approximate a curved cross-section. Here you can also see the ridges for the tanker that will need to come off:
Once the rear hole was mostly plugged, I glued a thin strip of styrene across the forward gap between the fuselage halves, then puttied over the boomer gap and the forward gap to get this:
After this, I attacked the putty and the tanker ridges with 200-grit, and then followed up with a second layer of putty that I had diluted with acetone to make it more spreadable. After this will be more sanding, then the wing join.
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During the putty/sanding phase (which ended up being 5ish cycles), I ran into a roadblock: the nose taper was incorrect in profile view because my widening strips went too far forward, giving an ugly 777-neck look as seen in the following comparison between the KC-135 conversion and a Heller 707 (which I’m told has minor inaccuracies as well):
I fixed it by punching out the putty in the gap and using a razor saw to get rid of some of the excess widening, which let me redo the taper with putty and sanding to just forward of where the sharkfin where the taper starts on the Heller kit:
It’s still not 100% perfect, but it’s good enough, as is the boomer pod gap:
Now on to the lobe creases and then the wings. Having a Heller 707 as a template will help with this….
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What a fun project! You’re doing a great job, I’m sure the finished product will be sharp. Since its’s a -138 I assume it will be in QANTAS colors?
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baby9 :
What a fun project! You’re doing a great job, I’m sure the finished product will be sharp. Since its’s a -138 I assume it will be in QANTAS colors?Thanks! I’m modeling VH-XBA as she appears today after I read this awesome story about her restoration. The finished product will ideally resemble this:
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Next up is the lobe crease and wing join. The lobe creases are best modeled on this picture:
Here’s my attempt at the crease (not perfect by any means): Start a small crease at the level of the top of the WBF about 3.5″ back from the nose at the second panel line and go to just over the wing root, then start 6″ ahead of the tail and go till just over the line where the trailing edge overlaps the fuselage (as per the picture):
After scribing these, I epoxied a carbon fiber rod in each of the upper wing sections to stiffen them, then glued them in place on the center wing piece that’s joined with the fuselage:
Once these parts are set, I taped the lower outboard sections in place and held them to prevent twist (the parts were warped). Next, a good bit of Tamiya extra thin through all the gaps, and then this as the outcome:
Tomorrow I’ll try to get going on the wing glove, which will be a bit of a challenge….
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The wing glove for the 707-100Bs was a bit tricky, at least the way I tried it. The other weekend I went to the Museum of Flight and took pictures of the wing root of their 707-153B (AF1) to make stencils. My plan was to add a root extension, add a leading edge extension, and then wrap a thin sheet of styrene around and be done with it. Doing the stencils took a decent amount of trial and error to get the right shape and cut, and once I had those done I glued the root profile and leading edge extension (both .030″ styrene) to the wing:
This was simple enough, but when I went to wrap the .010″ styrene around, it creased and knocked the other bits loose, so I glued the upper part of it to the leading edge extension and then filled the area beneath with putty:
I still need to clean it up a bit, but it’s getting there.
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After finishing up the wing glove, which required lots of sanding and more puttying, I added the ventral fin, which I got from a Heller sprue and then cut down to the right size. Fortunately it comes with mounting pegs, so I drilled two holes to mount it:
Next up was the wingtip VHF antenna, which appeared on some Qantas 707s, but not all of them. Fortunately, the AMT KC-135A kit includes two VHFs for the tail, one that has the refueling light and the other one without. The one without went up on the fin, and the other one I cut in half to embed in the starboard leading edge:
An embellishment unique to the aircraft I’m modeling, VH-XBA, is a pair of logo light pods. These are not included in the kit, so I carved a set from scrap sprue:
One of the more tedious aspects of the kit conversion is adding the four sets of vortex generators that go on the 707’s wing. Using my Heller 707 as a template for location, I cut ~100 small rectangles of .010″ styrene and glued them down to the wing:
This last picture shows all of these modifications glued and puttied in:
At this point I’m done with all the fuselage and wing modifications, and only need to finish up the engines. I’ve started masking the nose gear legs and cockpit windows and will move on to painting next. Thanks to everyone for all the help with this conversion, I really appreciate it.
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The hush kits predictably required more sanding and putty cycles than I’d care to count, but they turned out ok in the end. Once finished, I primed the the metal parts with black and then shot a coat of Alclad on. In the past, I’ve had issues with Alclad peeling off when masked, so I coated those areas with Future and let them dry for a few days before moving on to paint the nacelles and pylons in a light gray:
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After 8 months, I’ve finally finished the conversion. Overall, it was a rewarding, if frustrating project full of “learning experiences”
I highly recommend this conversion to anybody looking for a large 707 model and who has a table to spare….
[photoid=13596] [photoid=13594]
[photoid=13592] [photoid=13591]
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Beautiful job, however I cannot help but think you created extra work for yourself by this method instead of using a C-135 wing and a 707 fuselage.
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skyking918 :
Beautiful job, however I cannot help but think you created extra work for yourself by this method instead of using a C-135 wing and a 707 fuselage.Thanks! As far as the best approach, a number of us discussed it last December, and the conclusion I reached is that between cost and effort, moving the WBF was a better idea than trying to cut down a Heller fuselage and having two half-kits left over. The lobe crease, and plenty of other things, are not 100% perfect, but they pass the three-foot test….
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