Back to Basics

Brian wrote: Absolutely Phil, but "plank" doesn't sound very aerodynamic.

Well it made the infamous Wot 4 popular.:dry:

True!

I started the SIG Kadet project because I needed something meaningful to do, simple model, simple task to copy a plan and build it. What I should have done is measure and compare the details of the parts with the plan. Today I've found that the plan is a bit different to some of the parts. When I made a template for the wing ribs, I should have compared the length of the rib and the positions of the spar slots. My carefully cut ribs bear no resemblance to the ribs that would fit the wing plan, well they do, but the spar slots are more than 1/16" out of position. The next snag I found was that the plan view of the wing has the ribs at a nominal 2" pitch, this was OK and I assumed that the ribs were drawn "square" to the T.E and L.E. Once again, I shouldn't have assumed that the drawing was correct, the ribs are off square, and not uniformly, some drift to the right, others to the left. I've checked my prints and I can only assume that errors occurred when the copy of the drawing was first digitised..Anyway, its not all bad news, finding out what had gone wrong and figuring out ways to correct it has made the day pass without a though about the present situation. I've tacked on a couple of photos of my "building vernier" and balsa stripper. For anyone thinking of having a go at building from scratch, these simple tools make things a lot easier.

No photos today, no point in showing a heap of paper with scribbled dimensions, and some bits of balsa sheet cut to shape "to see what it looks like". After endless fiddling, drinking far too much coffee (kept me awake all afternoon yesterday) and eating a mountain of chokky digestives. I think I might have sussed the ailerons for the Kadet. Bit limited in what I can do as I'm running out of balsa in useful sizes. Good thing I've got enough to be able to add the spars and extra structure for the ailerons. So far I've manged to remember to cut holes in the ribs for the servo leads, and I've made a useful jig to enable the drilling and fitting of the wing retaining dowel.

Started to build the left wing today. To keep things simple, I'm going to hinge the ailerons from the top edge using covering material, this minimises the additional structure needed to take conventional hinges, something I don't have anyway. I remembered to cut holes for the servo leads before I glued the ribs, and I found a couple of servos for the ailerons. These will be mounted on their sides, I'm not keen on seeing the top of the servo and the servo arm hanging out of the wing.
I'm building dihedral into the wing, 1" under each tip, I vaguely remember that Dihedral" and "Dutch Rolling" are somehow connected, but I can't be bothered to find out, anyway an inch is hardly noticeable......is it?

Looking good, Brian. I've done 'live' hinges using the covering before and it has never gone well for me. This has been with iron on film where there must be a trick to having the correct sized gap before ironing. Too big a gap and the control surface is loose. Too small and you get restricted movement as well as buckling of the covering over time. This has been my experience and I have no given up on the technique. Now I cover separately and use sellotape crystal clear tape for the hinge if I'm going for top hinged surfaces.

Thanks Mike, it is tricky I must admit, what does work quite well is stitching two pieces of film together "sticky side to sticky side". This gives a strip about 1" wide, the sewn strips are then ironed on to the wing and aileron. This is done before covering preferably. The line of stitches gives a near perfect alignment of the aileron, I'll tack on some photos when I get to the exciting bit of adding the control surfaces. I've used clear tape in the past, but only on a glider. Is it still available? Haven't seen it for a while.

As Mike has stated - film hinges will normally create a wrinkle on the hinge line. So if your not bothered about that the film method does work. Ive even used it on a gas powered aircraft but I applied a stitched Solartex strip before the top film.

Sounds as though we're using the same method Kevin.

Brian wrote: I've used clear tape in the past, but only on a glider. Is it still available? Haven't seen it for a while.

Yes! 3M Blenderm.