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Feb 11, 2019, 03:22 PM
Culper Junior
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Build Log

Whirling Dervish for SFV buildoff.

I need another flying machine like another hole in my head, but I don’t want to break my track record of buildoffs. So, here is my late entry.

Right now, I am asking for some help interpreting the plans.

1. How do I know how much twist gets built into the wing? Just measure it off the plans? And how would it be built, with a jig of sorts?

2. In front of the propeller facing left is a notation about 10 degrees of something offset. What is it referencing?

All input is appreciated.

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Feb 11, 2019, 04:49 PM
B for Bruce
BMatthews's Avatar
The line for the 10° is parallel to the motor sticks. So that's the upward angle or "washin" angle for the "wing" at the tips. Basically the two motor sticks are pointed up at 10° angles.

The only thing holding the angles of the motor sticks in place is the strength and stiffness of the two 1/8" square hard wing spars. And because the angles are against each other I'd plan on sanding 10° angles onto the spots of the square stock that are going to be glued to the motor sticks. Otherwise you'll end up twisting them to lay against the sticks. And the twist is going to want to flatten out the angle when you lift things up.

To build this beast I think i'd keep it simple and just angle the motor sticks in place with some packing to hold them at a 10° angle and glue the wing spars down with the center overlap... At least I'm assuming that it's overlapped and not cut and trimmed to form the joint. With only the two pieces of 1/8 holding things together I can't see wanting to cut and glue one side and leave just the one single piece of 1/8sq....

I'd then cut out and trim a bunch of the ribs and simply build it in the air. Fit the middle rib then the rest. The good news is that being so strongly tapered you only need to get the ribls sort of close to the right length and they'll lightly wedge into place with some glue. So building in mid air in this case should not be too much of a bother.

And finally I'm REALLY looking forward to the flight video....

Any guesses for what company Frank Ehling was working for at the time?
Feb 11, 2019, 07:57 PM
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Any guesses for what company Frank Ehling was working for at the time?

Ummm...I think there’s a hint there somewhere but I’m not getting it. Jim Walker? Cause this thing looks like a misguided Ceiling Walker.
Last edited by aeronca52; Feb 11, 2019 at 09:15 PM.
Feb 11, 2019, 09:15 PM
Culper Junior
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Ohhhh....just saw it.
Feb 12, 2019, 04:51 AM
I like real wooden aeroplanes!
Sundancer's Avatar
Well good luck with that A52! I will CERTAINLY be watching!
Feb 12, 2019, 09:41 AM
Culper Junior
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Thanks guys!
My first chore is full size plans, or maybe just build from these using the motor stick length and full size rib pattern as a measuring base.

Next is finding propellers, since I don’t carve props. I’m thinking either a stock 10” from Volarie or molding props from sheet balsa like a Ceiling Walker. Looking at the plans and imagining it in flight, slow, fat, high pitch props seem like better choices than thin high aspect ratio types. IE, only enough thrust to give enough wing rpm’s for flight.

Once the rubber turns are expended there should be no energy to continue the wing to spin so the falling leaf glide should be expected.

It’s so neat to share these thoughts with you all around the world. Model airplanes and the internet, who’d a thunk?
Feb 12, 2019, 10:18 AM
Culper Junior
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Two pictures of a molded prop from a Ceiling Walker for those under the age of 50.

Sorry for the shadows.
Feb 12, 2019, 05:21 PM
B for Bruce
BMatthews's Avatar
Could you give us an end on shot showing the twist and pitch angles?
Feb 12, 2019, 08:09 PM
Culper Junior
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Hope my fat fingers don’t obscure too much.

The first two pics are of the upper stationary prop, the third pic you can see the prop hanger which is the drive prop.
Feb 12, 2019, 10:32 PM
B for Bruce
BMatthews's Avatar
That's what I thought. I like more pitch in my rubber props than most. But that's a crazy amount of pitch if what you are holding is the prop shaft.
Feb 12, 2019, 10:33 PM
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owlsabie's Avatar
This is a fascinating project! Can't wait to see it!!
Feb 12, 2019, 10:41 PM
I'd rather be flying.....
JeffMac's Avatar
I've liked this since i saw it years ago in one of my Air Trails issues....... Watching, Jim.....

Best regards,

Feb 13, 2019, 09:44 AM
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Originally Posted by BMatthews
That's what I thought. I like more pitch in my rubber props than most. But that's a crazy amount of pitch if what you are holding is the prop shaft.
Yes, I have the prop shaft/hanger in my fingers.
Feb 13, 2019, 09:46 AM
Culper Junior
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Owls...thanks for the enthusiasm!

Jeff...hope I can do it justice. Taking a long look at the plans I believe the props and their RPM is the key to successful flying here.
Feb 13, 2019, 01:31 PM
B for Bruce
BMatthews's Avatar
It's so simple yet there's so much going on. It's going to be a great project.

Speaking of flying..... how in heck did they hold it for winding the motors? I'm thinking you may need some sort of jig that holds the two fuselages. Or at least build in a pin in the nose that stops the prop turning on one side while winding up the other.

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