CAP 21 Progress Part 1
This article is a progress report on the ongoing construction of my CAP 21 and will be added to at various points along the way.
The CAP was given to me partially completed after having passed through a couple of hands already. Best guess is that it was a Pat French Models kit from the late 70's to 80's. It's about 1/4 scale. There are no plans or instructions and so things like the center of gravity and control surface movements are going to be something of an adventure! The previous owner had made a nice job of re-skinning the foam wing in 3/32" balsa as the original obechi veneer had peeled and bubbled. All I had to do to it was to fit the wing dowels and adapt the aileron servo holes to fit my Hitec HS 605 servo's (5.5kg pull) and hinge the ailerons. It was even covered for me! At this point the previous owners enthusiasm had evaporated and the fuselage remained as he acquired it apart from some tail fixing mod's.
 I couldn't find a length of 3/8 - 10mm hardwood dowel anywhere for the wing dowels. It was all pine, why no one had hardwood I don't know. In the end I turned down an old drumstick which was lying about in the garage! One thing I hadn't realised was that Profilm fades with age, or the manufacturer has altered the colour, I don't know which. As soon as I covered over the aileron servo bays the difference could be easily seen. There's no solution other than to recover the whole wing, and I'm not about to do that matey! And anyway the leading edge is covered in brown, which I don't think they make anymore, and which, despite misgivings at first, I'd gotten to quite fancy. If you look at the photo's it's pretty smart in a 70's sort of way. I think it suits it anyhow. When I first acquired the model I searched the internet for photo's of Cap 21's and could barely find a thing! Plenty of CAP 10's, 20's and 232's, everything but a 21! Later, after I'd decided to go with the yellow and brown, which was already on the wing, I found 21's all over the place! Typical huh?
The undercarriage position on a CAP 21 is in the wing, but the previous owner had moved it forward of the wing onto the engine mount box. On balance I think this was a good idea as anchoring an undercart with that much leverage into foam seems a bit shaky, especially considering the weight of the model (should be about 13 - 14lbs). However, it's not scale and I wasn't happy about how far forward it was too. I was worried that the tail may not come up on take off. The undercart itself is one of those fiberglass jobs. By altering it's shape at it's center section I got it back another 3/8", right back to the former at the leading edge of the wing. Then I realised that I could slice off the bottom of that former and get it back another 3/8" or more. Futher study revealed that I could overhang the former with the U/C and so got it back 1 1/4" altogether. It'll be fine in this position and you have to look hard to tell it's not scale!
I managed to get a new Super Tigre 3000 (30cc - 1.80 cu in) at a good price but minus the cast alloy mount and carburetor. The carb problem was solved by fitting the carb' from my ST G23, but the mount was a bit more difficult. I was told that these mounts are pretty heavy devices, around 6 ozs, and, as I was trying to save all the weight I could, I decided to make a mount out of 1/8" duralamin. When finished, it weighed a little over 2 ounces, so a good saving there. I just hope it'll stand up to the job, we'll see! This then mounts to the firewall on three 6mm bolts which means you can adjust the motor position for up/down or side thrust easily. I've fitted a 20 oz tank and hope that it'll be big enough... Once the motor could be fitted I got the fiberglass cowl hacked out to fit and prepared for paint.
 Began sanding the fuselage ready for covering and ran across a little problem. Whoever had built the fuselage in the first place had made a bit of a botch of the rear top decking. Where the top decking sheet butts to the fuselage sides there was a step, the sides being thicker than the top deck sheeting. So they'd put 1" wide strips where the top sheet met the sides and tried to feather it in. Trouble is they'd glued it on with cyano' so there was never a hope of an invisible join! I tried but eventually sanded through the top deck. As it turns out it was lucky I did. I decided to remove the top deck sheet and re-sheet it. I began breaking away the sheet and whole stringers were becoming detached too! The reason for this soon became evident. The formers that the 1/4" square stringers were attached to were 1/16" balsa! I couldn't believe my eyes. So, tore the whole thing off and made new formers in 3/16" and new 1/4" square stringers and re-sheeted the lot. There's a lot more torsional stiffness in the fus' now as you might guess! At this point I decided I didn't like how thin the wing seat was. I was considering gluing 1/4" strips down the inside but then thought how nice wing fairings would look. I didn't know if the full size had them or not but decided to make 'em anyway. When I finally found a CAP 21 on the net I was pleased to see that, yes, they do have wing fairings. Happy, happy happy...
Got the fuselage covered with no further problems and then trotted off to our local car accessory dealers to find a paint to match my yellow Profilm. Some hope, nothing even remotely similar. So, off to Bancrofts with my little square of film to get a match. I must admit that the guy who served me couldn't have been more helpful, and eventually we found a colour that looked almost perfect. Except that, once it was sprayed on my cowling, it wasn't! Nevermind, it's close enough, and they say paint gets lighter with age so in ten years or so I should have a match! One thing, some while ago I bought a 500ml, that's half a litre, tin of Humbrol cellulose thinners for £4 odd at a model shop; at Bancrofts I bought a GALLON for £5.35. It's one thing to support your local model shop, but blimey!
 Still worried by the weight and so decided to try and find the weight of other models about this size. Suprised to find that most are about the same, some lighter, some heavier. Had a scan on the 'net and found this: Mr Aerodesign is Martin Rousseau and he has many CAD drawn plans for sale, one of which is a CAP 21 of the same scale as mine. Not included in the specs was the weight, so I e-mailed Martin and he replyed saying that his CAP weighed 18lbs. What a relief! However, his had ribs and formers from wall lite ply, as used in house construction, without lightening holes, and had a cherry wood spar and was powered by a Zenoah G45. Even at this weight he reckons it flies great, unless, as he says, you want to do 3D and hover 2 foot off the ground. The plan he sells has construction from lite ply, with lightening holes, and an aluminium spar joiner etc and will weigh much, much less.
Well, It's all covered and fuel proofed so now it's the radio installation. I'll save that for the next episode... G :-)
FF 16.08.01
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