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by bjt4888
October 13th, 2019, 7:24 pm
Forum: Wright Stuff C
Topic: Wright Stuff C
Replies: 317
Views: 20061

Re: Wright Stuff C

Xiangyu, Sorry to hear about all the homework. Yes, very good idea to practice winding to destruction. Tan SS should stretch 10x relaxed length before breaking. A nondestructive breaking can be accomplished by hooking over a doorknob (lubricate first and pat most lubricant off) and stretching 7x and...
by bjt4888
October 13th, 2019, 7:05 pm
Forum: Wright Stuff C
Topic: Wright Stuff C
Replies: 317
Views: 20061

Re: Wright Stuff C

Also, it appears that the airplane is stalling at the end of the flight. Iis difficult to tell for sure as the video cuts off just as the biggest stall appears to be happening. Stall can be fixes by adding nose weight or sliding the wing saddle back a little. The airplanes this year are very sensiti...
by bjt4888
October 13th, 2019, 6:55 pm
Forum: Wright Stuff C
Topic: Wright Stuff C
Replies: 317
Views: 20061

Re: Wright Stuff C

If, for example, your loop length is about 30.5” (.0415 g/in), and your stretch 5x relaxed length to wind (after break in, properly lubed) an 85% breaking turns number would be 4,100. Probably need more back off (the large number of backoff turns needed is another indicator of needed changes (thinne...
by bjt4888
October 13th, 2019, 6:30 pm
Forum: Wright Stuff C
Topic: Wright Stuff C
Replies: 317
Views: 20061

Re: Wright Stuff C

Sorry, didn’t see the end of your data set mentioned that you have turns remaining of about 300. Still would suggest the same set of items to test in that order. Rapid descent indicates motor remaining torque is very low. A thinner motor will result in more turns remaining, but possibly longer time ...
by bjt4888
October 13th, 2019, 6:25 pm
Forum: Wright Stuff C
Topic: Wright Stuff C
Replies: 317
Views: 20061

Re: Wright Stuff C

Xiangyu, If you can supply the rubber motor loop length we can calculate the motor density per inch and determine the maximum number of turns it can handle. The typical solutions to all turns getting used before landing is: thinner rubber, longer rubber, more propeller pitch or different propeller d...
by bjt4888
October 4th, 2019, 10:14 am
Forum: Wright Stuff C
Topic: Biplanes
Replies: 4
Views: 1073

Re: Biplanes

First,

Good job doing the research. Moving the center of pressure doesn’t create any Aero advantage. The same can be accomplished by slightly shifting both wings forward. One wing directly on top of the other is easier to build.

Keep up the research.

Brian T
by bjt4888
October 3rd, 2019, 4:59 pm
Forum: Elastic Launched Glider B
Topic: Elastic Launched Glider B
Replies: 55
Views: 2878

Re: Elastic Launched Glider B

Bxt,

The Freedom Flight kit is also excellent. Won a very competitive Michigan States last year.

Brian T
by bjt4888
October 3rd, 2019, 4:56 pm
Forum: Wright Stuff C
Topic: Biplanes
Replies: 4
Views: 1073

Re: Biplanes

First,

I agree with K. Biplanes take a little more time to build but have the significant advantage of lower wing loading.

Stagger was used on full scale biplanes to improve visibility for the pilot. I suspect no aero benefit.

Brian T
by bjt4888
October 1st, 2019, 6:28 am
Forum: Wright Stuff C
Topic: Wright Stuff C
Replies: 317
Views: 20061

Re: Wright Stuff C

Eric, Glad changes look promising. 1 mm wing incidence seems like a small amount unless there is a decent amount of negative stab incidence. But test flights will sort this out. We usually start with slightly excessive decalage so that the airplane will stall and then gradually reduce till short of ...
by bjt4888
September 30th, 2019, 8:01 am
Forum: Wright Stuff C
Topic: Wright Stuff C
Replies: 317
Views: 20061

Re: Wright Stuff C

Eric, Yes, we are rebalancing with changes in motor weight. A little bothersome, but, once we have selected the competition motor, we’ll hopefully be done with this step. I agree, the pitch trim that eliminates the initial power stall doesn’t look quite as good later in the flight. We’re still consi...

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