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Feb 18, 2016, 03:57 PM
Chess club geek with wings
blunight's Avatar
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Build Log

Scale Build Off 5 - Dave Platt Bucker Jungmeister


1/4 scale Bucker Jungmeister
Designer: Dave Platt
Radio Control Modeler September, 1978
RCM plan #738
65" wingspan
10-12 lbs.
Rimfire 1.20 motor
100A ESC
6s 5000 mAh Lipo
Solartex covering
Plan source:
http://aerofred.com/details.php?image_id=80012

This plane and the plan author Dave Platt need no introduction, both are pretty well known. My intention is to convert this one to electric so I'll be making some small changes.

I'd rather fly than build so if the weather is nice, I'll be flying so this build may take some time. If you have a suggestion feel free to chime in!
This model is going to be built as a sport scale flyer so if I have to decide between reliability/performance in the air or scale fidelity, I will side with performance.
My intended scheme can be seen below:
Last edited by blunight; Feb 20, 2016 at 03:53 PM.
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Feb 18, 2016, 04:06 PM
Chess club geek with wings
blunight's Avatar
Thread OP
I began by having the plan printed out locally, they did a great job:
http://cheetah-printing.com/

I'm having a short kit cut for this one, it did not include any parts for the tail; I started building it about 2 months ago. As you can see it's built exactly as per the plan, the only thing I did was to add some lightening holes.

The horizontal stab weighs 3.83 oz
The vertical weighs 1.39 oz
Last edited by blunight; Feb 18, 2016 at 04:24 PM.
Feb 19, 2016, 03:20 PM
Registered User
Steve Merrill's Avatar
Nice!!
Feb 19, 2016, 11:39 PM
Registered User
I am looking forward to your build. Love the Jungmeister. John
Feb 20, 2016, 02:21 PM
Desert Flyers's Avatar
I've built two of these from the Platt Kits. Back in the 70's. Used a Webra .91 engine. Fantastic flying airplane. Easy to do Lomchevok (? spelling). Also inverted spins, so easy. I've not had very many models that could do those maneuvers. Still remember the Bucker's with fond memories.
------Bert
Feb 20, 2016, 03:50 PM
Chess club geek with wings
blunight's Avatar
Thread OP
Quote:
Originally Posted by Desert Flyers
I've built two of these from the Platt Kits. Back in the 70's. Used a Webra .91 engine. Fantastic flying airplane. Easy to do Lomchevok (? spelling). Also inverted spins, so easy. I've not had very many models that could do those maneuvers. Still remember the Bucker's with fond memories.
------Bert
That's good to know, thank you. I fly 3D planes almost exclusively these days and I was looking for something different that wouldn't be boring to fly. Your one of the few I've spoken to who have actually built this plane, your ideas and input would be greatly appreciated.

I'm going to start on the wing soon, do you have any ideas for the strut attachments? I want to include flying wires but don't think the clips the plan calls for would be able to handle the stress.

Quote:
Originally Posted by Steve Merrill
Nice!!
Glad to have you aboard Steve. I'm looking forward to shocking my flying buddies when they see me flying something other than a 3DHS plane!
Feb 21, 2016, 12:48 AM
Desert Flyers's Avatar
blunight: Geez! that was 40 years ago. I can't remember those details. I am sure I built as per the plans. In those days Dave Platt was the man and we did as he said.
------Bert
Mar 02, 2016, 04:12 PM
Chess club geek with wings
blunight's Avatar
Thread OP
My short kit arrived so its time to continue! I had Steve at Summit Model Aeronautics cut the kit which included parts for the fuse. You may be familiar with Steve (AKA "Steve85") as he is the moderator for the scale build off. Here is his contact information:

https://www.rcgroups.com/forums/show....php?t=2611736

[email protected]

The kit was nicely cut, it was packed well and was reasonably priced....what's not to like?
Mar 02, 2016, 04:19 PM
Chess club geek with wings
blunight's Avatar
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I'm missing some wood for the fuse so I'll continue with the wings beginning with the top wing>

Unfortunately I was unable to find spruce stock in the exact dimensions the plans called for so I'm making up my own; I ordered spruce sticks from National Balsa.

A) x spar:

Each 1/4x3/4 spar is made up of one piece of 1/4x1/2 and one piece of 1/4x1/4 stock epoxied together with laminating epoxy. (Resin Research using their 3100s slow hardener)
7, 36 long spars are needed for both wings.

B) x 9/16 spar:

Each 1/4x9/16 spar is made up of one piece 1/4x1/2 and one piece of 1/16x1/4 stock epoxied together with laminating epoxy.
4, 36 long spars are needed for both wings

I pinned and glued the spars together and used a straight edge to ensure they were straight.

After they were dry I sanded them all then created the angle in the middle spars by setting my small desk top sander up to create a 10.5 degree angle.
Mar 02, 2016, 04:52 PM
Summit Model Aeronautics
Steve85's Avatar
Glad to see everything arrived safe and sound, Trent. This is going to be a nail-biter of a build for me, since you're the first customer to build their short kit!

Trent was kind enough not to mention that I made few mistakes in cutting some of his wing ribs, so I sent him replacements. Hopefully all the parts will work out "as per plan".

Watching with keen interest...

Steve
Mar 02, 2016, 05:19 PM
Chess club geek with wings
blunight's Avatar
Thread OP
Quote:
Originally Posted by Steve85

Trent was kind enough not to mention that I made few mistakes in cutting some of his wing ribs, so I sent him replacements. Hopefully all the parts will work out "as per plan".
Steve I didn't see a reason to mention it since you corrected the errors and shipped the replacements so quickly!

I matched your parts to the plan, they were perfect; so as long as the plan is correct....
Mar 08, 2016, 08:33 AM
Summit Model Aeronautics
Steve85's Avatar
Hey Trent,

I can't resist; any progress? Enquiring minds want to know...

Steve
Mar 08, 2016, 09:24 AM
Chess club geek with wings
blunight's Avatar
Thread OP
Very little Work is getting in the way of my hobby.

Its slow going, the cutouts for the spars in the ribs are undersized so I have to carefully file away materiel until they fit.
Mar 08, 2016, 10:20 AM
Summit Model Aeronautics
Steve85's Avatar
Quote:
Originally Posted by blunight
Its slow going, the cutouts for the spars in the ribs are undersized so I have to carefully file away materiel until they fit.
Hmmm, something's not quite right. Are all the cutouts undersized, or just a subset? Are they undersized in both directions or just along one axis, and by how much?

"Standard" stock sizes can actually vary by a significant amount, but that probably doesn't apply to your spars since you built them up yourself.

When I draw cutouts in CAD, I draw them to spec, and then the CAM program calculates a tool offset corresponding to half the diameter of the cutting bit, so the hole is theoretically to spec. If it isn't, then I have some error creeping in that I'll need to track down and eliminate. Any feedback you can provide will be very helpful.

Steve
Mar 08, 2016, 09:29 PM
Chess club geek with wings
blunight's Avatar
Thread OP
The spar cutouts in the ribs vary in their problems, the only consistency so far has been the TE notch - its width is 3/32" and it should be 1/8".

Rib W3:
The 1/4x1/4 spar cut out measures 7/32"x7/32"
This rib has dual 1/4 x 3/4 spar cutouts. The actual height of both cutouts measure 23/32" - 1/32" short.

The forward cutout is the correct width - 1/4"

The rear cutout is 1/32 too narrow - 7/32"

Rib W7:
This rib has a 1/4x1/4 cutout for the wing strut mount. Its actual measurement is 1/4 " wide by 7/32" high.
The 1/4 x 3/4 spar cutout measures 1/4" wide by 23/32" high.
The 1/4x9/16 spar cutout measures 1/4" wide by 17/32" high.

Unfortunately I have filed W1 and W2 so I can not tell you exactly where the problems were on those ribs.

So all of the errors are 1/32" too small....I hope this helps


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