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Apr 09, 2020, 12:01 PM
AndyKunz's Avatar
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Build Log

Kirby Kadet


Nostalgia. Some times it just gets you.

I remember this article from when I was a kid. I wanted one of those Ace radios in the worst way - I had a World Engines but the receiver and servos were just too big.

Fast forward 40+ years...

I don't remember exactly how this came to my attention, but I ended up with the Outerzone Kirby Kadet printed out at full size on 11x17" paper, sitting on my desk.

I took a few lunches and evenings and converted the parts to CAD. Last night I finally cut them out and started gluing together. It took only 1 sheet of 1/16 x 4 x 36 balsa, 3 strips 3/32" sq and 1 strip 3/16" sq. My plan is to tissue cover it.

For the first time in a long time I'm building somebody else's design with very few changes.

Construction began by laminating all the formers together. These lay perfectly over the plans, if you take care to check the 'actual size' box on the Adobe printer options.

Formers B & C were glued to the left side using squares to keep them perpendicular. After they cured, I added the right side, using squares to ensure proper location. You can't see it, but the aft-most edges are tapered so they will end up as 1/16" when joined together.

Meanwhile, the wing trailing edges were notched to match the plans. I didn't have any 3/32" x 3/8" TE, so I substituted some 1/8 x 3/8 instead. I should have trimmed it to size first, yes, but I was impatient. Anybody else get that way?

The lower spars were laid down as the ribs were glued in place. I left the root rib off for now as I want to set it to the right angle for mating to the other wing.

Andy
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Apr 09, 2020, 12:39 PM
3d and EDF, some scale
MustangAce17's Avatar
too cool! I will need one
Apr 09, 2020, 12:55 PM
AndyKunz's Avatar
Thread OP
I can cut you one if you want. It's a single sheet of balsa plus some stringers, and it all fits into a box I have from back when I was kitting Mark Rittinger's Python. I could probably fit several in there.

Andy
Apr 09, 2020, 01:13 PM
3d and EDF, some scale
MustangAce17's Avatar
Hmm, that sounds enticing, how much? I remember the Python, had one before I knew much about building and it was halfway finished, not sure where it went :/. Pm me a price
Apr 10, 2020, 05:41 AM
AndyKunz's Avatar
Thread OP
Pulling the tail together was normal. I added former E at the same time. D came along later, taking care to insert it at the right location. This was made easier on the top side because the triangular wing saddle helped confirm the spacing.

The nose was a little more challenging due to the sharp bend. I first added 3/32" sq leftover strips from the wing spars to each side, 1/8" back from the front edge. These do several things for me:

a) They increase surface area for gluing former A into place securely,
b) They keep the wood from flexing along the grain, and
c) They keep former A from twisting due to the pressure applied by the clamps.

After the Titebond had cured on those strips, I attached former A using clamps as shown. Having the tail of the fuselage together helps, and it would have been even better had I applied the flat bottom sheeting aft of D. Do that yourself - it'll make it easier to keep the front end true!

This morning (I'm up 3 hours early - something didn't agree with me last night so I've been up since 2:30) I applied ammonia to the area from C to A, inside and out. This will allow the wood to relax ever so slightly, taking some of the lateral pressure off B and A.

Andy
Apr 10, 2020, 09:30 AM
Still the "Pro"-crastinator...
Steve85's Avatar
Andy,

Shall I induct you into the Build-Off?

Steve
Apr 10, 2020, 09:41 AM
AndyKunz's Avatar
Thread OP
If you want. I just wanted to document the construction for a friend.

Andy
Apr 10, 2020, 02:22 PM
Wanted for breaking Ohm's Law
Dennis Sumner's Avatar
Andy,

Are you going to use the electronics and motor from a UMX 2S donor? Looks neat.

Denny
Latest blog entry: RC Throw Gauge
Apr 10, 2020, 02:37 PM
AndyKunz's Avatar
Thread OP
No, I'm going to use a new receiver type and a single A2020 servo. Power will be one of the 50mAh or so 1S batteries.

Andy
Apr 10, 2020, 02:38 PM
Wanted for breaking Ohm's Law
Dennis Sumner's Avatar
Quote:
Originally Posted by AndyKunz
No, I'm going to use a new receiver type and a single A2020 servo. Power will be one of the 50mAh or so 1S batteries.

Andy
So rudder only? Definitely old school...
Latest blog entry: RC Throw Gauge
Apr 10, 2020, 02:39 PM
AndyKunz's Avatar
Thread OP
I'm building it per the plans, as close as I can. My only problem is that my servo + battery + receiver weighs less than his battery OR his receiver OR his servo!!! Nice problem to have!

Andy
Apr 11, 2020, 05:46 PM
AndyKunz's Avatar
Thread OP
The wing tip sheeting is cut from scraps 13/16" wide, then fitted between the spars, LE, and TE. They'll be trimmed to shape later.

The rear bottom sheeting of the fuselage is overkill at 1/16", but I'm going with the original design as closely as I can (it's really hard not to change things like that!).

The forward portions on the bottom are beveled to match the formers.

The curved nose sheet is wetted and glued in place.

It's coming along quickly.

Andy
Apr 11, 2020, 07:50 PM
AndyKunz's Avatar
Thread OP
The top spar is cut and trimmed to fit to the top of the tip sheeting.

The bottom front sheeting is done in two halves. One side is attached and allowed to dry, then it is beveled in the center to match the angle for the other side. The second side is then attached, overlapping the first side.

Time to do a little thinking for making the control linkage.

I hope you all have a good Easter or Passover.

Andy
Apr 12, 2020, 05:53 PM
AndyKunz's Avatar
Thread OP
The nose block was glued on and shaped.

The servo is centered, as I'm going to use it with a torque rod as shown on the plans.

Andy
Apr 25, 2020, 01:32 PM
AndyKunz's Avatar
Thread OP
It's been nearly two weeks since I last posted, but that doesn't mean I haven't done anything. It's just been smaller things, slower progress. I also spent some time building and flying some model rockets with my granddaughter. She just came into my shop and asked if we can fly rockets tomorrow after church. We'll see what the weather holds.

Picking up where we left off, I added the wing saddle, carefully lining it up to keep it centered on the dowel. The bottom side was wetted to help it bow slightly.

After that cured, I added 1/8" sq at the center. This is totally non-structural. Careful trimming of the ends to mate to the sheets help the appearance.

Part of the slow-down was to consider different techniques for attaching the wing struts to the wings and fuselage. I ended up using rectangular magnets out of an old BL motor (micro helicopters DO have a use ... ) on the wings. I carefully notched the bottom side, then taped the magnets in place. 30-minute epoxy was used to glue them on.

NOTE: Before using the magnets, stack them up and mark them to make sure you get the same pole orientation. If you look carefully you can see the black marker on some of mine.

On the fuselage side, I used round magnets and steel 4-40 nuts (I learned I have both brass and steel ones). I cut a 1/4" dia hole with a brass tube, then put the nut into the wood and put tape over it to keep it in place and flush. A dab of epoxy on the back side keeps them in nicely.

After that cured, I put the magnets onto them, using the same polarity (black side against the fuselage) for all. The struts themselves are 1/16" x 3/16" spruce strips. The ends are beveled to the wing side and epoxied in place. Then they are shortened and beveled to match the fuselage. For that the fuselage will be fixed in place and lengths will verify the centering and dihedral.

Andy


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