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View Poll Results: can you have a smaller rudder on a bype due tothe second wing?
yes 2 16.67%
no 7 58.33%
depends on size of the wing 1 8.33%
I dont know 2 16.67%
Voters: 12. You may not vote on this poll

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Old Apr 17, 2014, 08:28 AM
Flying>Life
JosephSzczur101's Avatar
Joined Jan 2013
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Idea
Concept and Design

Hello everyone,
I have started a new thread on here that is about Concept and Design for F3P and AM indoor planes. On this thread, you can post ideas that have a concept and a design that isn`t a typical for F3P or AM. The main idea for this thread is to use your imagination to come up with a solution for problems such as weight, drag, etc.

Idea 1- Since contas are very expencive, I have an alterative solution. Use a motor in the middle of each wing that spin in oppisite directions.

Positives: eliminates torque

Negitives: can be heavy, 2 motors=2 ESC, needs reinforcement for motor mount

Please share your thoughts and ideas on this type of stuff and make recomandations for these ideas.

Best of luck,
Joseph
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Old Apr 18, 2014, 02:32 PM
"Free" in Christ!
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Joined Jan 2012
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I love the idea of this thread!! I will post here if I have any ideas.

About the contra systems. I have thought about that, but have worried about how your could get airflow to the tail surfaces effectively. I think your biggest problem would be the CoG and the weight of the system. I would love to see someone try it though.
Also, I've made a coaxial system for under $100 including props.

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Old Jun 08, 2014, 11:04 PM
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Joined Nov 2007
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Keep inertia in mind. The more weight you move outside, the more initial (and final) response you take away. You also do not need two ESCs for two motors.

As for rudder size...the rules don't change. And you want your balance of vertical surface area in favor of the rear.
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Old Jun 10, 2014, 10:04 AM
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Joined Dec 2001
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Just an idea, to increase roll authority with a contra-rotating setup could you use differential torque by slowing one down and increasing the other? Like a contra-rotating heli does.
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Old Jun 11, 2014, 10:14 AM
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I think Kimmo talked about this. He said that it would be a bad idea because it would create p factor as well as torque. THIs is the main reason why people don't do it.

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Old Jun 11, 2014, 02:19 PM
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It would be like running a prop in front or directly behind of a wall. Not a good idea.
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Old Jun 11, 2014, 08:58 PM
Adam RED Weston
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Brier, WA
Joined May 2006
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I've got differential speed on my contra set up on my scratch built F3P, it works well... It's particularly useful in doing torque rolls. I've copied Kimmo's set up with two speed controllers, without it, you would have to do a great deal of fiddling to get your front and back motors tuned so they don't produce torque. This is most efficiently done with different throttle curves for each motor. The roll is set up using aileron to throttle mixing.

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Old Jun 11, 2014, 09:10 PM
Adam RED Weston
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Brier, WA
Joined May 2006
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A Little Different Design Aproach

So, I think this will fit on this thread... I came up with this design as I brainstormed how to make a light and stiff structure to compete in F3P. A space truss came to mind as the lightest approach and current designs are adding drag devices, why not use the trusses as structural elements AND drag elements! I call it the Carbon Truss 3D.



That's the concept...now on to execution. I wanted a Mylar surface, and I chose carbon rods to make the structure. I chose a relatively simple design and mirrored some of the parameters from my Vision 3D such as tail volumes and fuselage size. The wing planform started out as a rectangular wing, and morphed later as a added more wing area.

The hardest part of doing a truss is making the junctions between the rods. Another challenge is covering the surface once the truss is built. I used woven Spectra kite string soaked in CA as a joiner. I would scrunch the spectra up so the rods could go down the middle than I would pull the Spectra tight over the rod joint and then soak it in thin CA









the wing is a truss set up to support the Mylar surface. I did some triangles with the rods and Spectra then joined them with some Spectra knots. This continued until I had a full wing.







More soon...

RED
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Old Jun 12, 2014, 11:08 AM
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Joined Oct 2005
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red_hlg Thanks for sharing your photos and construction details. I've been thinking along these lines for some time now. In fact, I bought a Vision 3D kit but I have not begun to build it. It looks like a LOT of building effort. And I'm not sure that I can build it as light a necessary for a really slow, acrobatic airplane without using too much glue weight.

Your joints for the carbon rods looks unique. My earlier attempts to join carbon rods with tow and superglue gave me really stiff, easily breakable joints. So I've thought there must be a better way. In fact, everything I've done with super glue made things so stiff and breakable at the joints.

I like Uhu Creative and Uhu Por for getting flexible glue joints. I don't like the long drying time.

I saw a plane design some time ago which used carbon rods and tiny fuel line to join them. That looked flexible and promising, but perhaps heavy. There also is heat-shrink tubing.

Again, thanks so much for sharing!
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Old Jun 12, 2014, 10:50 PM
Adam RED Weston
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Brier, WA
Joined May 2006
519 Posts
Thanks... Happy to share, I would love to see some folks take this concept and run with it. The plus side on this construction was it it's so tough, yet light. This plane is a lot stiffer than my EPP and carbon rod Vision 3D, and actually ended up being even more durable and WAAAY more durable than a milled depron plane. I ended up over building it, I used a lot of 0.035" and probably could have made it all out of .020 or even 0.015".

The spectra really makes a great joint, it not brittle, and we'll even stay stuck to the rods if you totally break up the CA. In fact, using it as a control horn was where I first learned about this construction. Fred Mallot made an R/C HLG that had carbon rods for push rods, then at the surface you would score the rod about 3/4" (18 mm) from the end of the rod. Then slide the 1/2" (12.5mm) long woven spectra over score. Then you would disk with CA. Then you would break the carbon where the score was and bend the spectra/CA up until it made about a 45 degree to the control surface.

The downside of the Carbon Truss 3D's construction was it was very slow. I spent 10x longer than my Vision 3d and maybe 20 times longer than a flat foam design. I did end up a little heavier than I wanted, but I could have pulled that out with smaller rods and lighter Mylar. Also, the joints with spectra are a challenge because the carbon rods, even when sharpened, tend to snag on the spectra when you slide the sick over the end.

Some additional thoughts on the joint option I would like to explore are some plastic joiners like T's and X's. I could imagine some 3D printed joiner that has five or six nipples pointing in all the directions necessary to make some of the complex joints.

More later... RED
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Old Jun 16, 2014, 08:04 PM
Flying>Life
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Hey Red_HLG,
what was the total weight of your design?
Joseph
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Old Jun 18, 2014, 01:51 PM
Adam RED Weston
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Brier, WA
Joined May 2006
519 Posts
Right now, she's at 84g without battery... So sub 100g flying weight. Like I said, I think this truss concept could be much lighter than what I built it at...

RED
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