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Something a little different this time

Old 04-09-2018, 03:49 PM
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Default Something a little different this time

Having completed the design of a crop duster style plane, using the spare wing parts I had from the "lost" Avenger kit, I switched gears and decided not to build it. Sort of a "been there, done that" mindset, having already built the "Demi Duster".

After awhile, the 'conventional' designs start to all look the same to me. High wing, shoulder wing, low wing, taildragger or trike gear - ho hum.

On to Outerzone I go, once again. Punched "Canard" into the search box and started looking at what popped up. This one caught my eye.

The "Mockingbird" is a 51" span model originally designed for a .19 to .30 glow engine. I just happen to have an equivalent electric motor, ESC, and battery sitting around that would fit very nicely into something that size.

One of the things that interests me is that in the build article the designer laments the fact that he had to add quite a bit of weight to the nose to obtain the proper CG. Looking at the fuselage design, I can build in a very long hatch and battery compartment, and fiddle with battery placement to get things to balance out without adding additional ballast.

Time to make some initial sketch changes on the plan sheets, make some measurements and re-draw the whole thing in my CAD program.

Ugh. Just noticed I'll have to bend my own main landing gear again.
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Old 04-09-2018, 04:12 PM
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Nice one ...

REminds me in a way of the old Cougar model ... was kitted for a 40 glow many years ago. Was supposed to be a sort of jet style model .... but of course no canards

Nigel
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Old 04-09-2018, 09:46 PM
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Landing gear is not that hard to do. I have never bought a factory one in my life. It looks an interesting model though.
I found old road signs are an excellent source of dural.
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Old 04-10-2018, 01:16 AM
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Originally Posted by Panther View Post
Landing gear is not that hard to do. I have never bought a factory one in my life. It looks an interesting model though.
I found old road signs are an excellent source of dural.
Unfortunately, this one doesn't use dural landing gear. It uses two lengths of 5/32" music wire, bent to shape and mounted in wing blocks.

I've done it before, although with a slightly easier 1/8" wire. Bending it isn't the problem, it's bending two correctly so they match up. Last time I bought 30 feet of 1/8" wire (a ten section bundle of 3 foot sections) and by the time I got two done correctly, I had used about 7 of the 10 sections! I think this time I'm going to design a custom bending jig and have my buddy make it up at his machine shop.
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Old 04-10-2018, 02:20 AM
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I usually bend the main leg and screw it to a plank. Then mark on the plank where the support leg should be and bend to suit from there. Then I screw it down as well before I wire wrap and solder. Holds it all nicely in place while the solderer bloke does his job.
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Old 04-10-2018, 02:20 PM
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I tried searching for a Harry Higley wire bending tool. None to be found anywhere. I think they are out of production. Tower Hobbies suggested I purchase one on backorder status, but given the status of Tower Hobbies right now, I didn't think that would be too wise.

I did find a set of the three HH tools (1/16", 1/8", 5/32") on Amazon from one seller, but I balked a little (actually, almost fell over in my seat) when I saw the price of $1000.00! At least shipping was free! :-)
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Old 04-10-2018, 09:41 PM
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Started the CAD process. The airfoil is a Clark Y - I have a database of airfoils in my CAD library, thankfully! Did some measurement points on the plans and started punching in a general outline. I am going to be using a clear canopy (mostly because I just happen to have one unused lying around) so I've modified the outline to accommodate it.
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Old 04-11-2018, 06:52 AM
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I'm looking forward to seeing how this one turns out.
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Old 04-12-2018, 05:49 PM
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One of the things that must be considered in the design process are the available parts that may be needed for completion. After all, there's no sense designing something that calls for a part or linkage bit that doesn't exist! (Unless you like to machine things yourself, anyway.)

With the canard setup, there is quite a gap between the elevator halves. The fuselage is 80mm (about 3 1/8") wide at that point. Conventional connection would be to bend up a connecting wire between the two elevator halves, and then connect a control horn to one of them, with linkage from the servo exiting the fuselage side.

Ugly. :-(

In my brief foray into the world of electric control line, I had downloaded the Brodak catalog. They make a very nice "control horn" that is actually a section of 3/32" diameter wire, with two sections bent back to connect to control surfaces 4 3/4" apart (usually used for wing flaps in CL stunt) and a drilled linkage arm silver soldered to it at 90 degrees to the wire bends. Perfect! And, the linkage will be contained inside the fuselage.

I also checked out their pre-bent wire landing gear selection, and found a pair of wing mounted gear that is almost a perfect fit to the Mockingbird plans. The only thing is, they are 1/8" diameter vs. the 5/32" called for in the plans, but I know bending up a matched pair of gear from the heavier wire is going to be an issue. I ordered a set of wing mount LG blocks with the 1/8" groove as well.
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