abufletcher

Opinion time. I've mentioned to Chris that I'm contemplating reducing the width of the TEs in order to get more of an optical effect of a wire trailing edge. Remember that the TE pieces are made of 0.8mm ply laminated with 3mm balsa (which is sanded off to almost nothing). The point is it's strong. So I've considered cutting it down as in the pencil lines in the photo below. I made up a little test piece of the lamination and it seems plenty strong to me.

Most kit builders would probably prefer to just leave it as it is. But you know me...

What do you all think?

grover1

Don
You can run some CA along the edge of the TE to make it harder .
Greg

udet1918

Since you're asking. I think you will go through a lot of trouble "thinning" out the trailing and still be left with something at least four times the width of an actual wire. IMHO to much trouble for very little gain! Now if you were going with an actual wire........

You're doing an excellent job, looking forward to more.

Ron

TFF

I say half your dimension. What you will loose cutting down the edge is impact resistance once the plane is finished. Get too thin and shrinking the covering will break or bend. I dont know if you would have enough clearance to do this but the two ply parts could be put together with a thinner core and cut back the way you want and then run a couple of laminating strips that stand proud of the ply to act as an edge. Being so thin might not be worth the trouble.

allanflowers

clear plastic?

abufletcher

Hmm...that's a very interesting idea! I could leave it exactly the same dimensions but made of thin plexiglas/perspex type material. Hmm...

Chris probably hates it where I head off into the wild like this when doing a prototype! Sorry!

John Cole

My Feedback: (4)

Don, if you are building the model as a prototype, it might serve the mfg (Chris) to see how the stock kit works out. However, if you have lots of latitude to modify, then I'd recommend using cable for the TE's. It's not hard to do, and nothing you do with wood will look the same, especially with a translucent finish. You may have to brace the end of the ribs a bit. I was reluctant to try this too, but it worked well and I'm glad I tried it. Just a thought.

John

GianFrancesco

In my Albatros CIII, I used a mm. 0.8 music wire; the method is very intriguing and the result is especially pleasing in transparency; but the ribs with my original profile in the scale 1 / 6 were too fragile, so I had to "toughen up" with CA; however, the trailing edge resulted rather wavy ..... a little too much! [:@]
The suggestion of plexiglass or lexan is interesting, I remember a similar suggestion of Mick Reeves for a rudder.

abufletcher

Thanks for all the ideas. John, this is ONE prototype (of two kits currently out there being build) but Chris knows that I'll take a few liberties with it, as I did with the Snipe. It looks like a well-thought out kit with sound engineering all around. But I'm always filtering things through the "scale what-if filter," particularly anything that will be visible from the outside (which is a lot on WWI models). The laminated TE used on the CDScaleDesigns WWI kits is a very good solution to the problem of producing a TE with a scale thin edge. Most kits just leave you with a 1/8" non-scale edge. With Chris' solution the very edge of the TE is only as thick as the ply (and even that is sharped to a finer edge). The lamination of balsa acts primarily as a filler between the top of the ply and the top line of the ribs. But it also adds strength.

Now if CI's came in PC10 or lozenge this wouldn't be an issue. And it wouldn't be much of an issue if the modeler chooses one of the overall light blue schemes common to the CI. But I'm leaning towards one with CDL wings and these wings were sort of semi-transparent. They were certainly sufficiently transparent to be able to see the markings on the top wings from underneath. And that means all the structure is also visible. Chris and I did a lot of research and attempted to make the wings as accurate as possible in terms of things like spar width and placement (all three), rib count, and partial riblets. The only compromise was on the TE where it really is impractical on a kit to do a wire trailing edge.

The way the ribs and TEs are designed (where the TE ply actually forms the very tail end of the airfoil), it's really not possible to just "leave it off" and use a wire instead. The rib ends at least 1/4"-1/2" short of the edge line of the TE (where the wire would need to be located for a scale outline). Also I think I'd have to beef up the ends of each rib with ply to be able to attach a wire.

So for all these reasons, trying to use a wire TE on this model would be swimming up-stream. In a flood. I did get some acrylic plastic sheet (2mm) and experimented a bit with that. It's interesting. The acrylic is at least twice the weight of the ply and balsa but it might be one possibility that I think I'll leave for some future C1 builder to try. But it does look pretty good under the solartex!

abufletcher

So I think it's really just the trimmed down TE or the stock TE at this point.

abufletcher

Besides since I'm planning on using a wire TE on my scratch-built DrI, I can experiment with technique there. Gian, did you pre-bend the scallops into the wire or did the covering do an efficient (too efficient?) job of pulling it in? Did you use Koverall and dope on your CIII?

abufletcher

I had to give it a try...and actually once I found the right tool for shaping the acrylic, it was probably as easy as making a new part from balsa and ply. It looks pretty darn cool. The balsa and ply laminate weighs 8g and the acrylic part 16g. But the acrylic part did fail the "wiggle test." I held the end of both parts and lightly wiggled both up and down (to test flexibility). The balsa and ply laminate flexes very little (good) and the acrylic flexed enough (a lot) to actually snap off where the piece was notched for one of the ribs. Not so good.

Well, I couldn't have lived with myself if I hadn't given it the ol' college try. The second photo shows how it would look covered (with a black sharpie line along the edge to simulate the wire). I'm already planning, no matter which TE I use, to put a small brass wrap-around fitting (or better yet a thin strip of stainless tape) at the end of every spar location. On the original this fitting held the wire to the rib and also had the effect of producing a bit of a "sharp point" at every rib position vs. the slightly too smooth look of the pre-shaped TE on just about every kit I've ever seen.

John Cole

My Feedback: (4)

Don; Ooo, right! I forgot about the ribs being sized for the ply TE. You're correct, a wire TE would not be a simple mod like I was imagining it would be. Well, getting the edge really thin is the next best thing, and it sounds like you guys already have that addressed. Nice build.

John

abufletcher

Hmm...maybe I can just paint the wooden TE cream white. This won't help with the transparency in the sky but will probably aid those on the ground photos. This is similar to the technique of painting internal non-scale structures PC10 with wings that are semi-opaque on the bottom and PC10 on top. It fools the eye into thinking that it's looking straight through to the top surface.

grover1

don
I don't know if you can get Filtesskin [link]http://www.fliteskin.com[/link] in Japan .
The 0.025" Thickness may have some flex in it to use on the TE and be easier to glue as most glues will hold plexiglas/perspex well.

Greg

abufletcher

I can buy FRP (fiberglass reinforced plastic) from the shops in Osaka in sheets that are 0.5mm, 0.8mm and 1mm thick. But I'm not sure what good it would do since it's not clear (but rather an ugly greenish tone). I might allow that thinner (but since not scale) edge but then the ply+balsa is also pretty strong.

I'd like to just get on with this build and use the stock TE's. Again, maybe painting them off-white is a good compromise solution.

The acrylic is WAY too brittle and my nice trailing edge is now in five little pieces with only minimal effort.

GianFrancesco

I used a straight music wire fixed to the ribs with CA and aluminium clips 0,15 mm. thick; the Koverall shrinking combined with the dope (nitrocellulose automotive paint) did all the "work" of flexing the wire; the Koverall was in one piece overlapped at the leading edge; this worked OK in the horizontal plane; a little worse in the vertical one.

TFF

I guess you need to build a Dr1 wing and cover it to see what is going on.

allanflowers

I am not surprised the clear plastic didn't work out in this application. I would be mostly worried about weight, stiffness and the strength of the glue joints. One doesn't want to build a wing and have it start to come apart later when trying to cover it.
Good effort though. We have all learned something from your experimentation.
There are lots of cases on the TE of wings where a big balsa corner gusset is used - where clear plastic might serve as well and not create the non-scale see through issue.
In building my CD Scaledesigns Pup, I had problems with the kit-suggested trailing edges (same .08ply + balsa laminate as on the CI), which didn't give a strong enough TE to hold together while covering - so I would worry about modifying this design to even thinner parts, unless the CI has cap strips which would help hold things together. The answer on my SSW D.III was to go to a 1.5mm plywood TE which, with the cap strips, is very robust. It is holding together great, even with multiple coats of shrinking dope.

abufletcher

I'm surprised to hear this as I certainly had no problem with an identical TE on the Snipe. But then I didn't use koverall and dope, just solartex. It's true though that with such a thin airfoil as we're using on the CI, there's not much "meat" at the tip for the TE to attach to. If I really thought that more strength were needed I suppose it wouldn't be any problem to put a 1mm balsa cap strip on top of the existing ribs and just feather this into the LE.

abufletcher

These photos show 1) the extremely obvious amount of washout built into the ailerons and 2) the flat surface of the inside of the curve of the center cut-out. It seems to me that there must have been a bit of curved ply in there. The last photo shows the degree of washout current in the kits aileron. I can't decide if this looks scale or not. The outer end of the aileron is about 14mm above the inside end.

abufletcher

The diagram on page 21 of the Cross and Cockade special issue on the Albatros 2-seaters shows how the angle of incidence of the top wing changes across the span and what can be taken from this is that the wing stays at 5.8 degrees until the aileron but at the outer edge it's at 1.5 degrees. This would mean that there was 4.3 degrees of washout in the aileron. And that's almost exactly the number seen in the original photo as measured in photoshop (using the line tool and the information palette). I've leveled to first photo to account for dihedral. That it I set the inboard TE at zero degrees.

The blue line in the second photo shows that the model aileron at present has a bit over 2 degrees. The red lines shows 4 degrees.

GianFrancesco

I have checked the drawing I did for my Alb. CIII and the angle is of 5°.
The washout of the aileron T.E. starts from the second rib outwards; the result is very marked.
From the stability I have found during the few flights I have done, I can assure that it helps a lot!
I got the information from the book "Avions Allemande" by La Gorgette (1917) (*) that is a mine of informations,dimensions etc. about Albatros CIII and if, I remember, B1; I suppose it could apply to the C I too.
(*) Let me know if you need the PDF file.

abufletcher

Gian, that's good to hear, and I did go ahead and reset the angle on the aileron trailing edge by jacking up by about 8mm (which is somewhere around 4 or 5 degrees) and then packing up the riblets until they reached. It now looks like the photo.

This alteration, however, means the GFR aileron bellcrank part no longer fits (the angle of the horn is wrong) so I'm going to have to make up two new ones. Chris would send me a couple updated ones, but he's going to be on a well-earned vacation for a couple of weeks so I'll just cut them out myself. When I have the pattern worked out, I'll post it here as a pdf file.

abufletcher

Did some of the little stuff on the upper wing. Gussets and bracings. Also I trimmed down the angled TE part and the tail end of the root rib just slightly (on the outside) to make room a length of 1/4" x 1/16" balsa which will give me the flat look seen in the original photo above. This will get sanded down so that it tapers into the rest of the TE. I also added two additional gussets in the boxes by the bellcrank slot.

One thing I still need to work out is how to do the aileron hinges. The plans suggest three robart-style pin-hinges more or less equally spaced. However, this is not scale accurate in two ways. First, the C1 had four hinges: Two on either end and two on the sides of the bellcrank slot. Also the CI (like most German aircraft) used strap-style hinges. That presents a bit of a problem (i.e. "interesting building challenge"). Since the airfoil on the model is thicker than on the original, the wings/ailerons have more depth at the hinge location. This is why Chris chose the convenience of center-hinging with robart hinges. To simulate a scale appearance, I'd like to put the hinges along the top edge of the wing/aileron. One way might be to insert a bit of dowel (or carbon rod) with one of the same kind of brass strap hinges I've made for my DrI into the top edge of the aileron.