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Author Topic: A sorta Gowen penny plane  (Read 950 times)
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Richard Ewing
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« on: December 06, 2014, 11:05:41 AM »

My try at a Gowen inspired Penny Plane. 
3.5 grams.
It flys...
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A sorta Gowen penny plane
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Olbill
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« Reply #1 on: December 06, 2014, 11:20:49 AM »

Nice!
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ykleetx
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« Reply #2 on: December 06, 2014, 12:53:05 PM »

I see the Gowen inspiration -- except in the very flamboyant rudder  Smiley

Please post the plan.

-Kang
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Richard Ewing
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« Reply #3 on: December 10, 2014, 03:58:32 PM »

Sorry for the late reply.  I really did try to follow most of the Gowen plan.  But here are some dimensioned sketches of my wing tip plates and the vertical fin.

Rick
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Re: A sorta Gowen penny plane
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Olbill
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« Reply #4 on: December 10, 2014, 05:56:15 PM »

If I were planning on competition I'd keep the tip plates within the 5" wing chord max. Only a really strict CD would complain but it is possible.
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cglynn
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« Reply #5 on: February 26, 2015, 01:13:00 PM »

Question on max wing chord.  Is the rule written so that as measured from the leading edge of the wing, no part of the wing chord may be longer greater than 5 inches, or is it more like that the wing may not exceed the dimensions of an 18"x5" rectangle? I ask because I just finished a Penny Plane that uses swept back tips, similar to my recent F1L and Kagan's Eidolon F1D design.  The wing definitely extends outside of an 18" x 5" rectangle chord ways, but when  measured from the leading edge, I made sure that no part of the wing chord is greater than 5 inches.  I will post some pictures in another thread once I get home from work.

Thanks

Chris
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Olbill
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« Reply #6 on: February 26, 2015, 07:25:44 PM »

I started to write what I thought would be a clarification but gave up.

I questioned Kagan about the Eidolon when I first saw the plan because when I measured his plan it looked like the TE was sweeping back faster than the LE. As I remember it, he actually measured the wing and had enough clearance under the max chord for the middle part of the wing so that the tips stayed legal.

I think that as long as you don't exceed 5" anywhere in the plan view of the wing measured from LE to TE you will be okay. The problem is trying to write a rule that specifies how and where that measurement is taken. Looking at the tip plates above it seems like as long as they didn't exceed 5" in any location from front to back then they would be legal. But how do you say (in a rule) how to take that measurement?

It would have to be something like "lay the tip plate flat on a horizontal surface and measure parallel to the bottom of the wing". Yuck. What part of the bottom of the wing???

So I think the plan view argument works well for a polyhedral wing and swept back tips are perfectly legal. For vertical tip plates I'd rather see them stay inside the 5" of the main wing - but I don't think I'd DQ a model like the one above UNLESS I could find a front-to-back horizontal measurement greater than 5".

Why does it have to be so hard?
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leop
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« Reply #7 on: February 26, 2015, 10:27:20 PM »

The AMA rules appear to have no section of only definitions so we must look elsewhere for some clarification as to the how to measure the chord.  The indoor rules for the Bostonian, even 215 in Section 22, says that the chord is "measured  parallel to the direction of flight."  This is a good starting point to use for all the indoor classes (hint for the next rules change cycle).  For airfoils with no sweep, rake, or taper we can usually measure perpendicular to the spars.  For airfoils with sweep or taper we need be more careful.  For example, a swept wing will have a shorter perpendicular distance than the chord as the chord makes an angle with the spar.

My current F1L's, F1D's, and LPP's have raked wing/stab tips (both dihedral and vertical) that are not within the chord of the wing/stab.  However, if measured parallel to the direction of flight, the "chords" at all points in the tip are less than the maximum chord.   This is not so hard and does not take any virtual unfolding.  At the Nats and team trials, the judges just use the gauge and make sure that the airfoils, including the tips slide in without touching.

LeoP
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cglynn
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« Reply #8 on: February 27, 2015, 09:05:59 AM »

Bill, Leo, thank you for taking the time to clarify the chord rule.  I feel better about my models now.  Just need to get out and fly them. 

Chris
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