GianFrancesco

My memory is not what it once was; reflecting on the issue you highlighted, I think to understand why I have decided to make the linkage of the ailerons like that!
For the linkage movement there is a lot more space in the "plane of the wing" than in the thickness!

abufletcher

Back from Tokyo! I suppose I've been there 20 times or so now, so it's just another trip into the Big City for me. Highlights were Turkish Doner Kabob, The Windows 7 Whopper, and the RC shops!

No one had the HiTEC HS-82mg in stock. So I first considered the HS-85MG which is also metal gear but higher torque. But the price was only a bit less than the Futaba S3102 mini-servo, which has more torque, metal gear, and longer available servo arms. So I went with that. This isn't the digital version. The shop also had a "special price" on Futaba S3003 standard servos so I picked up three of those. Futaba stuff is easier to get here in Japan than HiTEC. I would have been cheaper (even including shipping costs), however, to order all this stuff from Tower and have it mailed to Japan. The only advantage is that now I have them in my hot little hand.

abufletcher

I'm still slogging through the rib cap strips.

abufletcher

Here's one of the wing servos installed. This is a slight modification of the kit (as there were some problems with the kit parts). In my way of doing it, there is a slot in the wing for the movement of the servo arm and the hatch (to which the servo is attached) extends only as far as the edge of this slot. Also notice that with the way I've built the area for the servo, there is a cutout in the rib (LR-13/LR13p) through which the top of the servo extends. In my opinion, this works better and I'd recommend it for the kit.

Keep in mind that with the servo arm/aileron bellcrank geometry, the servo arm requires around twice the angular rotation as the aileron. In practice, this means we'll probably need around 45 degrees of rotation on the servo...and that means the arm will be traveling well outside the wing surfaces. The only way I see to avoid this is to somehow or another have the servo arm (or a bellcrank) rotating on the plane of the wing...which pretty much means moving the aileron servos into the fuse. Personally, I'm happy with this compromise.

abufletcher

There are always lots of little things that need doing on a wing after it's "finished." That's what I've been doing today. Adding "packing" at the spar locations to make it level with the surface of the wing. And adding ply doublers at the spar locations (which should have been done before). Adding bits of 1mm cap strip material to level out areas next to the cap strips (for example around the servo horn slot. And then there are a couple other spots when packing is needed. Then, of course some final sanding and smoothing and evening. It's all rather tedious but it all needs to be done.

And, then, I still need to drill the holes for the spar bolts. Oh, yeah, and I also need to fit the brass wing tubes (though I may do these differently).

abufletcher

The CI just screamed out for a pair of the WB 5" wheels with the white tires! I bought these over a year ago and have been "naturally aging them" on other models ever since. I figure they're now just about right! The best way to get a gray tire is to start with a white one and give it hell! Time to start weathering a new pair for my DrI!

abufletcher

I split a 200mm (Sanwa) extension lead and soldered one end to a long section of servo wire, fed that through the straws in the wing and then soldered on the other end. I wanted to be able to simply unplug the servo if need be without cutting it off the extension. I can also easily replace the wire. It's always fun so see installed servos doing their thing!

abufletcher

More tedium today. Same as before but on the other wing panel. Then it'll be back to the tedious bits on the upper wings. [&o] But at least I'm completely finished with the cap stripping. I've been working on them since Oct. 4 and I'm REALLY looking forward to moving on!

BTW, one odd thing I noticed, when I had laid the wing down over the plan for a photo, is that the cord of the wing and the cord on the plan didn't match!!! The wing seemed to be almost a full centimeter too wide. [X(] I wondered how the heck I had screwed up so badly. Then it dawned on me! The wing is built up on jacks AT AN ANGLE. So the cord as measured flat on the plans is not the actual cord of the wing! The real cord would be the diagonal of a rectangle with the TE down in one corner and the LE up in the opposite corner.

geezeraviation

My Feedback: (3)

Abu your aileron linkage is like a pull-pull system for a rudder. The binding occurs due to the attach point on the servo being about one half the distance from the pivot in comparison to the distance from the pivot at the rocker end. On the full scale aircraft these rods as you know were cables in a closed loop system with one going to the opposet aileron and the other going to the stick and thus no binding. You may be better off driving one rod as a push pull and letting the other go along for the ride, I can think of a couple of ways to do that as I'm sure you can. Nice build, I'm anxious for you to get into detailing the cockpits. Oh dont know if you can get it in Japan but Behlen makes a dye based stain that has no affect on woods ability to absorb glue. Glen T uses it in the pecan tone in some of his work.
Doc

abufletcher

The "binding" I was referring to in my mock-up was due to the rod actually striking the center pivot point of the servo arm. It wasn't the "akerman" style binding common to rudder pull-pull systems. On my mock-up, the small servo arm to large bellcrank set-up doesn't "bind" in the sense of one side ending up with more tension than the other. The problem is in the geometry where the unequal arm length means that only a fraction of the servo arm rotation is transferred to the bellcrank. We chose this geometry because the cables and attachment points would be approximately in their scale locations. Anyway, I think we've worked out a solution that gives us sufficient rotation for good aileron deflection. Using a single rod in place of the cables wouldn't change this geometry. But you're right that this problem wouldn't come up in a full closed-loop system. I believe we would still have the same situation even if we moved the servos into fuse with a closed loop on each wing half.

Actually, I hate working on stuff like cockpit details. In many ways it's the least interesting part of scale WWI modeling for me in that it's all about faking stuff; it's about trying to make little bits of plastic and balsa look like instruments and joysticks. In contrast working on the undercarriage, which most modelers probably hate, is fun for me because it's all about figuring out how to make a fully functioning structural unit of the aircraft that's ALSO scale in appearance.

abufletcher

Lower wings are ALL done!

abufletcher

Sure looks big enough on the table.

abufletcher

Hmm...just realized that that big German cross that I thought would be hiding the servo is on the BOTTOM of the wing. [:'(] I'll have to think of a way to camouflage it on the top.

geezeraviation

My Feedback: (3)

Abu, it'll still hide it a good bit while in flight. Maybe paint the servo case so it's less visible while staticly displayed.
Doc

abufletcher

Doc, that sounds like a good idea. Maybe even just a piece of balsa stuck to the side.

There are still some important details to be finished on the upper wings. There's the boring stuff like adding the hardwood packings on the spars at the strut locations (this time on the bottom) and some 1mm balsa strips to be added to the aileron LE (and the aileron wing cutout). Then there are the important things like figuring out how to do more scale hinging and making a template for a new GRP bellcrank. The current bellcrank supplied with the kit is about 1/4" too long in the front (almost touches the rear spar). Also since I've increased the aileron washout to the scale amount, the angle of the part is no longer quite right. It's also possible that the attachment point for the cable will need to be moved around to get the necessary about of aileron movement.

abufletcher

For some reason I haven't yet figured out, much of the scale aileron washout I added seems to disappear when I "hang" the ailerons. [] Where did it go, and how do I get it back!

geezeraviation

My Feedback: (3)

Does it come back if you remove the aileron and place it on the bench? What sort of angle is on the L.E. of the aileron, or is it rounded? Very odd it would relax or pull out when mounted, any stress or binding in the hinges? If I could juse wiggle it
Doc

abufletcher

Just a note to myself and others: The inboard and outboard struts are in fact subtly different because of the built-in washout to the wings. Also I initially couldn't find the side views of the struts on the plans because a couple of the rib outline drawings are placed "over" the drawings. I ended up cutting out "half" of one of the side views before I realized that it was part of the drawing below. []

As on the Snipe (and other designs) each pair of struts is best constructed as a single intact unit connected by music wire/stainless cross-wires soldered in the middle. This locks in the wing incidences and washout so the rigging is less critical.

geezeraviation

My Feedback: (3)

Did you figure out where the wash out in the aileron went? Is it related to the struts you just posted?
Doc

abufletcher

It's just that the ailerons as they stand now are still quit flexible. It may be a good idea to run a dowel as a "spar" though the center of the aileron riblets (as was done on the Snipe). This would help hold the twist. The kit actually included 3mm birch dowels listed as for the ailerons but aren't shown on the plans.

geezeraviation

My Feedback: (3)

Aha yes. That would help a great deal. In particular when it comes time to cover them, it's so hard to maintain "shape" of delicate parts when covering and shrinking.
Doc

GianFrancesco

Don
in the picture you can see how I have made the ailerons of my CIII; the rod in the middle is a 1,5 mm. dia music wire that "works" to mantain twisted the whole.
Your C I is coming out very well indeed

abufletcher

Problem found. Problem solved! I used a 3mm brass tube with the end sharpened to cut a straight line of holes in the aileron riblet. Then the 3mm birch dowel pieces included with the kit fit perfectly. I might consider using 3mm aluminum tube since it would have no ability to twist. I'll check the weight of both. This should lock in the washout and give it all the rigidity it needs. But I'll need to make sure that each aileron has exactly the same degree of twist.

abufletcher

Well, perhaps not completely solved. But headed that way. I looks like the problem is with the aileron LE. When I have that pinned flat against the wing TE, most of the washout disappears. So I think I'm going to have to make some slightly V-shaped cuts in the top of the ribtlets (which I thought I had already done but apparently not successfully) so that the full washout is there without any degree of stress. Then the dowel, and perhaps a couple of gussets, should hold it rigid in this position.

abufletcher

I'm gettin' there! So, after clamping the LE/TE together with a few bits of 3mm balsa as stand-offs, I used a razor saw to cut through the outer three riblets just behind the aileron LE. Then, starting with the outer-most riblet (the one with the most washout angle), I added some balsa wedges. This keeps the aileron TE up at the right angle. Then I made a balsa template of that maximum angle to use on the other aileron.

The whole ailerons still seems a bit "twisty" and I wonder if it wouldn't be advisable to laminate the LE with 1/16" ply and/or add a few thin ply gussets here and there.

I also started working on the (slightly) modified GRF bellcrank. This is still the one from the kit. I shortened the forward arm about 1/4" and that will mean I need to change the collection point in the back to keep the pull-pull geometry right. The part of the bellcrank in the aileron will also get the cap strips.