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Old Feb 17, 2012, 04:50 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,661 Posts
Extension

Cover it tonight and fly tomorrow morning.

Tom
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Old Feb 17, 2012, 10:01 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,661 Posts
9:00 AM tomorrow

If the weather's OK.

Tom
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Old Feb 18, 2012, 02:58 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,661 Posts
Wow - that didn't work!

The right wing extension worsened all problems. Left aileron was required for flight. Left turns were made only with difficulty. Ground control was terrible.

Actually, the airplane met all design goals on it's first flights. It just required left aileron trim. I believe it can be rigged with minor mods.

Back to the shop.

Tom
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Old Feb 18, 2012, 06:06 PM
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Joined Oct 2004
2,854 Posts
Try removing one segment first. Also, how does the lateral CG look now? Building up more structure might add more weight than the lift it adds.
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Old Feb 18, 2012, 06:49 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,661 Posts
Brandano,

Too late. I sawed it off. Left the end rib so I could sand it down for a better tip.

The structure was very light. The CG was close to the fuselage right side - like before.

I think it's just drag. I'll add a little weight to the left wing and get another data point.

As I said above, the airplane is fine. I'd just like to understand it from a design perspective.

Tom
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Old Feb 26, 2012, 04:37 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,661 Posts
Thrust offset

I decided to add a little left thrust - and discovered that the motor actually had some built in right thrust. It wasn't something I'd noticed because of the folding prop. So, I put in a shim that gave bit of left thrust - not much maybe a degree or two.

Really nice flying day. Took off and observed it still leaned right. Powell (pilot) trimmed it for hands off and it handled so well that we forgot about time. One problem with Hyperion Lipos is the flat discharge curve - when power sags it's all over. Powell got it down as quick as possible but missed the edge of the field. The prop and gear folded and the model kicked up a lot of sand with little damage.

Checked the trim angle of the aileron. It was less than half that of previous flights. I will increase the left thrust offset to 3 degrees.

Also I suspect there could be some difference in incidence angle between the left and right wing panels. They are all strung on the tubular spar. It's possible for a slight twist to have worked it's way in. It wouldn't take much.

Will fly again Tuesday. Hope to start hand launches soon.

Tom
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Old Feb 26, 2012, 05:43 PM
internet gadfly
nmasters's Avatar
Colorado
Joined Aug 2006
2,186 Posts
It sounds like you're working the bugs out just fine. It's hard to do anything perfectly the first time. At least now you know that, in addition to flying, it's tough enough to survive a hard landing.

--Norm
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Old Feb 26, 2012, 06:22 PM
Grad student in aeronautics
United States, GA, Atlanta
Joined Oct 2010
464 Posts
So do you have any final conclusions for us regarding that balance issue? I didn't quite follow the discussion about tip extensions, tip ballast, aileron trim, etc.

Thanks
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Old Feb 26, 2012, 07:57 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,661 Posts
No conclusions yet.

I want to build a slightly smaller version. I'm sure I can scale it with some mods and get a satisfactory result. However, that would hardly constitute 'design' - manipulating parameters to obtain a predictable result.

I have the CG at approximately the half span point. I'm going to leave it there as I investigate further.

The model is very strong, has lots of room for equipment, excellent forward visibility and is a delight to fly. But, I definitely do not understand all I know about this airplane.

Tom
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Old Feb 26, 2012, 08:32 PM
Herk
HerkS's Avatar
Virginia USA
Joined Jun 2007
1,650 Posts
Quote:
Originally Posted by Tom Harper View Post
No conclusions yet.

I want to build a slightly smaller version. I'm sure I can scale it with some mods and get a satisfactory result. However, that would hardly constitute 'design' - manipulating parameters to obtain a predictable result.

Tom
Real aircraft are developed - not just designed
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Old Feb 26, 2012, 08:49 PM
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HELModels's Avatar
Joined Aug 2003
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I did some quick and dirty asymmetrical experiments way back. I used a water bottle, an off center mounted wing, and ...wait for it...a V-tail mounted at different angles.

What I saw was a tendency to turn easily in one direction. I didnt pursue it far enough to determine if I could get a V that would work.

Keep going Tom, it's good reading.
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Old Feb 26, 2012, 10:29 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,661 Posts
Thanks guys!

This is what makes it interesting.

Tom
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Old Feb 27, 2012, 04:35 AM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
2,971 Posts
Tom.

Nice project and good results, congrats with the successful flights!
Tom, a short message.
I did read all the posts of your thread and didn't read anything of it but maybe there was written about or you thought about it already.
What about the photo camera laying on his back to reduce frontal drag. Isn't that possible?

For a period I did make photographs this way, see the picture also combined with a video transmitter to preview locations.
Result is the photographs are mirror images but software can solve that problem.

The profit is the frontal drag generating surface can be a lot less depending of the model of the camera and so reduce the assymetry of the plane. You probably can reduce the heigth of the pod. Smoothing the corners also reduces drag.

In my picture you see a small mirror on top of the "Sky Box".
The video transmitter is on the "doorstep" near the bottom of the fuselage, antenna pointing down.

Success and I will read about your project.

Cees
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Last edited by Taurus Flyer; Feb 27, 2012 at 04:40 AM.
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Old Feb 27, 2012, 11:48 AM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,661 Posts
Cees,

That's an interesting approach that had not occured to me.

Have to think about that one.

Thanks,

Tom
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Old Feb 27, 2012, 01:21 PM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
2,971 Posts
Tom,

Short note, if it is a kind of automatic photocamera think about measurement of light and distance.
So "mirror" these sensors too. Maybe the distance sensor you can overrule?

This is a "Fast Personal View"!

Cees
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