1/2A combat design

faif2d on Sun Jan 17, 2016 5:20 pm

In the gallery of faif2d you will find a good flying combat design for Tee Dee in PDF. called the whetstone IV

https://www.coxengineforum.com/gallery/Personal-album-of-faif2d/whetstone-iv-pic_899.htm

roddie on Sun Feb 07, 2016 8:48 pm

I like it. Is it your design? I have a couple of questions; what was used for covering.. and the bell-crank platform/tab. It looks to be about 3/32" thickness if you compare it's slot in the center rib to the 1/4" spar-slots as a reference. Is it plywood or some other material? Music-wire pushrod? The plan states 240 sq. in... I tried rough-scaling and I get around a 28" span. and a 7" root-chord. That would be well under 200 sq. with the tapered T/E calculated in. Maybe my math is wrong.

EDIT: I guess it's closer to 30-31" span. I hadn't added the measurements between rib-stations. The inboard wing is longer.

faif2d on Sun Feb 07, 2016 10:40 pm

The bellcrank platform was I think 3/32 ply. I may have made some with 1/16th but can no longer remember. Yes it is my design, I had a friend and we flew practice matches one whole summer using my combat launcher. All of my designs at that time were covered with Doculam a clear mylar covering that was very cheap. The push rod was 1/16 music wire, the new way using aluminum knitting needles is far superior. About 1/2 way through the summer I made some with spruce spars and bass wood TE, using hard balsa for the ribs. They lasted a lot longer! I purchased 2 tee dee's from Gene Hempel and they were very strong. I got a bunch of 5-3 rubber duckie props and some cylinder piston sets from Dale kern. I still have the motors and they will keep up with the early Russian motors but not the new ones now.

Ken Cook on Mon Feb 08, 2016 5:26 am

This looks identical to the Czech Mezjlik 1/2A which is no long available. Ken

faif2d on Mon Feb 08, 2016 12:06 pm

I did not think that any of the eastern European designs used a monoboom and stabalator. Did I miss them? I did purchase 2 models from Mezjlik and they had stabalators hinged at the back of the wing.

duke.johnson on Mon Feb 08, 2016 1:35 pm

I like this design, it might make a nice combat model with a foam leading egde, carbon boom, and carbon trailing edge. Rats, another project on the list. I'll never get through this list. This is by far my best life problem.

fredvon4 on Mon Feb 08, 2016 3:04 pm

Duke...I too have more wants and desires than time...

On the combat plane ..I see you think like me...but don't go down that rat hole unless you have the time

Built as shown they are very sturdy and don't really need all the hi tech you suggest unless you need the best of the best for competition....back yard fun with your boys... great design and quick to cut out and build as is....

fredvon4 on Mon Feb 08, 2016 3:11 pm

faiF2D

I need to see the terminations of the aluminum needles.... wife has hundreds...diameter? How is the z bend or contact to the BC and elevator done.... When I test bend a 90 there is too much stress cracking for my comfort...heating?

faif2d on Mon Feb 08, 2016 4:51 pm

the Mezjlik that I have used .080 dia and I used .090 diameter(US number 1 =.0885). The end with the taper is bent into a z bend but with the first leg at 90 degrees to the body not parallel as it is normally done. No heat but I did use a small round nosed pliers to make the bends. The control horn end is left straight and goes through a circuit board wiring block metal piece that you take out from the plastic. This gives you a nut (where the wire was supposed to go with a screw (used to hold the wire in place) that now goes through the control horn hole. This allows you to adjust the elevator movement. This idea was found by the British sometime in the early 90's. I do think I had to space the 1/2A belcrank up to clear the ply platform.

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