Aberle "Li'l Eaglet" - RC Groups
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Dec 06, 2016, 07:59 PM
AndyKunz's Avatar
Build Log

Aberle "Li'l Eaglet"


Back in the 1970's, Cannon Electronics were considered the smallest electronics you could get for your RC planes. Even the transmitters were tiny! Bob Aberle designed several planes for the gear, and the one I'll be building is the "Li'l Eaglet."

Plans for it are available from Flying Models Plan Store, along with over 1500 other FM plans. This is a legit business, run by Thayer Syme.

Anyway, plans are ordered and on the way.

The electronics will be scavenged from the new UMX Cessna.

Andy

Disclaimer: I'm a Horizon employee, so I'll be using and recommending Horizon products. But I would have been using them anyway, even if I didn't work here!
Last edited by AndyKunz; Dec 06, 2016 at 08:08 PM. Reason: Attach images.
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Dec 06, 2016, 08:59 PM
Owner - Flying Models
Just to be clear, the plans are not on the way yet. As much as Andy and I may will it, his order isn't going far until the post office opens in the morning.

Thayer
Dec 07, 2016, 07:44 AM
AndyKunz's Avatar
When I posted that they were. The order was on its way into your computer, and I've seen your reputation in other threads for quick shipping. NOW you tell me that you don't control the postal system - I'm so disappointed!



So I spent the rest of the evening making laser cut ribs for this. The S3016 airfoil is a pretty close match to what Bob chose. I'll also be using lighter construction throughout - no need for a 3 ounce airframe! I'll be making a few other changes to reflect modern technology as well.

Andy
Dec 07, 2016, 12:12 PM
Owner - Flying Models
I wouldn't mind controlling the postal system. I'll bet that is a pretty good paycheck.

But back in the real world, I'm just a customer. USPS tracking says you should have the plans on Saturday, so with any luck you will be able to start building over the weekend.

Thayer
Dec 07, 2016, 09:01 PM
AndyKunz's Avatar
Working from a magazine page scan I was able to get some measurements worth putting into CAD for laser cutting. All the dimensions were nice round numbers, making things even easier. Hopefully I'll be cutting tomorrow night!

I used Profili Pro2 to generate the wing ribs.

Andy
Dec 08, 2016, 08:37 AM
Gravity is a harsh mistress.
Tim Wolff's Avatar
Since you are cutting the parts:
If slow flight is among the goals, I'd go with an undercambered airfoil as they will generally generate more lift at a given airspeed than other profiles. But they also limit the overall performance at higher airspeeds. Doesn't need to be particularly precise in these sizes either.
Dec 08, 2016, 08:41 AM
AndyKunz's Avatar
Slow flight is the antithesis of the goal. I'm actually going to make the firewall so it can take a 280 motor mount as well.

Andy
Dec 10, 2016, 12:51 PM
AndyKunz's Avatar
Thayer,

Plans arrived just now. Thanks for the quick service once again!

Andy
Dec 10, 2016, 03:04 PM
Owner - Flying Models
My pleasure, thank you! Glad they made it while you still have some weekend time available.
Dec 10, 2016, 03:09 PM
AndyKunz's Avatar
Unfortunately I've been working all weekend so far, trying to meet a deadline.

I had the laser files ready, just haven't cleaned off the top so I can cut.

Andy
Dec 10, 2016, 08:26 PM
AndyKunz's Avatar
Parts are all laser cut and I'm sitting down to glue them now.

Andy
Dec 10, 2016, 09:02 PM
AndyKunz's Avatar
The original Lil Eaglet was quite over-built by the standards we use for electric planes this size, so I reduced wood to more typical values for today. The fuselage sides are 1/32" balsa with a 3/32" sheet doubler about 3/32" wide around the edges. This will give some glue surface area for the top and bottom sheeting which will also be 1/32", and then some meat so we can round the corners.

Andy
Dec 10, 2016, 09:28 PM
Owner - Flying Models
Nice start Andy. Getting those first few parts glued up is always a good feeling.
Dec 11, 2016, 02:46 PM
AndyKunz's Avatar
My next step was to frame up the wing. First I glued all the ribs onto the notched shear web. This verifies spacing and keeps things mostly together. I then put glue onto the shear web and ribs for the bottom spar and put it into place on the plans, with a 1/32" scrap spacer under the rear of the center ribs and none farther out. I then pinned things down - the rib behind the spar is rather flat, so pinning it down to the building board helps give a straight wing.

Immediately I applied glue to the top of the shear and ribs and then added the top spar. This I-beam construction is very strong and not prone to warping, and the notches for the ribs make construction very simple.

Next it was time to add the 3/32" x 1/8" TE and pin it down. Note that none of these pins is piercing the wood. They are clamping it to the foam and to one another. Finally I added the 3/32" sq LE. It's up in the air a bit - if you want you can put some scrap under, but I just apply enough pin pressure the it stays put. The straightest piece I had for the LE had a slight bow to it, about 1/16" in the center. I attached it to the front of the wing so that the high spot was on the top in the center. This means that while I'm trying to build the wing flat, if the wood decides to warp on me it's probably going to pull the leading edges down, giving more washout. That would be better than it warping upwards.

I then set it aside to cure, and turn my attention back to the fuselage.

Andy
Dec 11, 2016, 03:01 PM
AndyKunz's Avatar
While the wing cures, I turned my attention back to the fuselage.

The fuselage is built in much the same way as Bob Aberle discussed in his FM article. With the laser-cut corner stock around the perimeter having dried, the next step is to attach the two sides together. On my model I have a 3/32" balsa doubler behind the ply firewall. Glue this doubler so it is flush with the front edge, and add two temporary formers of the same width - one at the LE, and one near the TE. Square them up and allow them to cure.

In the article and plans, Bob Aberle also noted that RC gear other than the Cannon he used was slightly wider, so suggested building the fuselage wider than the plans show to accommodate it. I'm going the other way - my receiver and motor are both narrower than the plans, so I'm building the fuse 1/8" thinner than the plans show. I want to reduce frontal area for better speed if possible.

Andy


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