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Jun 03, 2020, 06:49 PM
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Build Log

Junkers CL.I


Having been a happy recipient of some Model Plane Foam (Thanks, Mike!), I decided to build something with it. Criteria were that it had to have landing gear, use a KFM2 airfoil, and (hopefully) fit under the FAA's 250 gram limit. Oh, and it had to be full-house, as I really don't like models without rudders.

So, I took one of my past balsa models, rescaled it to 180 sq. inches, and tweaked it to fit a WWI plane, the Junkers CL.1 two-seater fighter/ground support aircraft.

Before I start in the thread, I need to make the following caveat: If the Junkers is successful, I'm going to submit it to RCM&E as a build article. That means that I can't publish the plans.

Having said that, let's get into the build.

First off, the enormous parts list:


I started by gluing the carbon spar halves together, with a 1/16" birch ply joiner.
Last edited by Captain Dunsel; Jun 03, 2020 at 07:04 PM.
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Jun 03, 2020, 06:51 PM
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Next step was sanding the wing panels, then joining them around the spar, on a jig.
Jun 03, 2020, 06:56 PM
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Glued the KFM steps on the wing (not shown), and laminated the fuse parts with white/clear Gorilla Glue.
Jun 05, 2020, 12:38 PM
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Hmm, did a few odds & ends, but didn't take the piccies. Sorry!
Fuselage is roughly sanded to shape and firewall glued in.

Yesterday, I mounted the wing to the fuse, then the tail feathers. I get the wing level on the jig, add the fuse, and then add the tail feathers.

After it all dried, I cut the aileron servo mount area out of the wing bottom, then glued in some 1/4" sq. bass servo mounts and the landing gear (I sewed the LG to the bulkhead with Spyder Wire and soaked it with CA a few days ago).

Today, I mixed some microballoons with clear Gorilla Glue and used the slurry to fill gaps between the wing and fuse and around the LG mount.

I also ginned up some control horns from an old credit card and glued those into the control surfaces. I also trial-fit the rudder & elevator servos into the fuse and made up some doors from 1/8" foam.

CD
Last edited by Captain Dunsel; Jun 05, 2020 at 12:52 PM.
Jun 07, 2020, 07:53 PM
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Glued acetate discs to the wheel hubs, to be primed and painted tomorrow.

Tried setting up the receiver and servos, only to have the receiver (Orange 6 channel, used in two previous models) decide to burn out. So, I've got to swap the receivers I have, so I have a small, end-pin receiver (AR6115e, I believe) available for the Junkers.

Otherwise, I cut the pushrods, added pushrod braces, and so forth. More piccies tomorrow!

CD
Jun 10, 2020, 06:37 AM
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Umm, a bit later than 'tomorrow', but here are some shots.

I wanted to keep the fuse an odd number of laminations thick. As MPF is about 1/4" thick, that meant 5 or 7 layers; I went with 5, to keep the weight down. The negative results are that the battery bay is a bit tight, and the rudder & elevator servo bays aren't wide enough to allow using MPF for bay doors.

So, I'm doing a little Dremeling in the battery bay, and I've made the tail feather servo bay doors from 1/8" house insulation foam that I hot-wired to 1/8". After painting the model, I'll mount the servos and the doors with hot glue.

One note about the wheel covers: I have a large supply of clear plastic, salvaged from Easter bunny containers, etc. Sanded, it glues pretty well to the wheel hubs. Don't use card stock, unless you can guarantee you'll never fly off wet grass....

CD
Last edited by Captain Dunsel; Jun 10, 2020 at 06:46 AM.
Jun 12, 2020, 01:50 PM
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Airbrushed coat of Apple Barrel Khaki on the topsides and onto the wheel covers. Sanded the plane lightly with 400 grit, then sprayed on a light top coat.

I know it doesn't look that great, but I'm trying to keep the weight down.

Next is the green pattern, then the late WWI straight crosses (probably black tape). Still have to figure out the turnover pylon and add the dummy engine.

CD
Jun 16, 2020, 07:21 PM
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Painting is almost done. The color scheme I'm using is white underneath; as MPF is white, I'll leave the underside unpainted.

Profile aircrew and gun, foam dummy engine and exhaust are done, as are all hinges, etc. Actually, all that's left are the black crosses and final balance (so far, it's nose heavy).

I've decided not to submit it to RCM&E. The radio and battery bays are too confining. So, if it flies well, I'll revamp it to use 7 fuse layers instead of 5; that'll go to the magazine.

Since the 5 layer version won't be published, I'm posting it here. Pictures of the painted, crewed, and almost done bird will be posted shortly.

CD
Jun 17, 2020, 02:08 PM
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Finishing is done. RTF weight is 247 grams, although the model does balance nose-heavy, so adding ballast aft will probably break the 250 gram target.

The German crosses were done with scrap LASER labels, painted with rattlecan flat colors. The gun and aircrew were printed onto bond paper, then glued to clear acetate I know the mirror-image, colored in KolourPaint, is wrong in many respects, but it works and is flexible enough to (probably) survive a nose-over.

All paint (except for the markings) is Apple Barrel acrylic paint.

Once it gets tested, if it's successful, a thicker-fuse version will follow.

CD
Jun 20, 2020, 01:17 PM
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Maidened the Junkers this morning. Had a bit of a problem with elevator trim -- as in ran out of up trim and it still wanted to nose down. Once that was fixed, the plane proved to be stable, quick enough for me, and not bad getting off/on grass.

One problem that did occur was silhouetting. Where we fly, the sun is behind models until late afternoon. So, I had to be extra careful not to lose track of the model's attitude...(Before you ask, we had thunderstorms in the area by the time we got home from the field).

I'm a bit uncertain about doing a 7-layer version, though. Even with all sorts of holes in the foam, I suspect there'd still be enough foam (and laminating glue) to outweigh a conventional box structure.

So, Miss Micki and I are going camping next week (Yippee!!!). As always, I'll bring along my laptop computer and will be doing some drawing. I MAY draw a box-fuse version, or I may draw something totally different.

CD
Jun 24, 2020, 07:53 PM
TonyS
Very nice designe and build! Very glad to learn it flys well.

TonyS
Jun 26, 2020, 10:59 AM
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Quote:
Originally Posted by Captain Dunsel
Maidened the Junkers this morning. Had a bit of a problem with elevator trim -- as in ran out of up trim and it still wanted to nose down. Once that was fixed, the plane proved to be stable, quick enough for me, and not bad getting off/on grass.

One problem that did occur was silhouetting. Where we fly, the sun is behind models until late afternoon. So, I had to be extra careful not to lose track of the model's attitude...(Before you ask, we had thunderstorms in the area by the time we got home from the field).

I'm a bit uncertain about doing a 7-layer version, though. Even with all sorts of holes in the foam, I suspect there'd still be enough foam (and laminating glue) to outweigh a conventional box structure.

So, Miss Micki and I are going camping next week (Yippee!!!). As always, I'll bring along my laptop computer and will be doing some drawing. I MAY draw a box-fuse version, or I may draw something totally different.

CD
Kudo's to Captain D! Great looking build.

Ken
Jun 26, 2020, 12:41 PM
flyin' fool
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