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"SkyWing" hybrid wing body ultralight

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Victor Bravo

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OK, I'll play.

First, I do NOT know how to stress test your wings, or anyone's wings. There are several people here who know how to do it, some of whom have done it professionally. The mathematics and engineering are way above my level of education.

But I am a world class expert who does know why to test them. I can do that calculation as well as any engineer on this planet, and I can say without a doubt it saves you a lot of money on funeral costs. Remember the guy who had to put Sonny Corleone back together after that toll booth incident, so Don Vito could have an open casket at the funeral? I happen to know how much his services cost, and trust me it's more than you want your family to get the bill for.

And I do happen to have enough experience with experimental airplanes to know when and where cheap is acceptable and is not acceptable. Cheap is always acceptable in a few places on experimental airplanes, it is never acceptable in a few other areas, and it is maybe acceptable in some other places only if you determine each case individually. My point is that one of the areas where it is almost always "never acceptable" is in primary structure.

So it's a bi-plane, you say? Excellent choice. Where are the flying wires that take the shear and bending loads imposed on the aircraft's wings by normal flight loads?

3 times aircraft gross weight applied to the wings themselves may be usable, because when you do a stress test you assume the wings support themselves without applying any bending or shear loads to their own spars. So if you have a 500 pound airplane, and 200 pounds of that are the wings, then you test the wings to 1500 pounds, which is a 7.5G test using the "non-lifting components" as the weight.

Can you tell me how much difference there is in price between 6061-T6 aluminum tube and the SDR-26 PVC tube? Meaning if your design needs a total of X feet of tube for your spars, then that many feet will cost you how much in PVC and how much in 6061-T6 aluminum?
 

Speedboat100

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Europe
I figure that since PVC tubed furniture is made for heavy people to sit on that it should not break under the stress of 500 pounds of ultralight airplane and pilot distributed over seven wing spars of 14 feet long.
That's 75 pounds on each wire-braced spar. I'm searchin for total affordability. Maybe $6,000 with engine. Hirth F-33.

I think even electric AC is doable with 6 big ones.
 

Allen

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Jun 3, 2010
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Key West
Thanks for all the input guys. ;=] I will let you know how the sandbag tests turn out.
 

Lendo

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Feb 6, 2013
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Brisbane
I did read somewhere, that some people are determined to kill themselves - at the lowest cost possible.
No criticism implied or intended on our Experimental Pilot friends.
For myself I try to do everything myself, wherever I can. If this means designing and manufacturing a lot of things I look for the best 'Value for Money' on materials, not always is the most expensive the best. I know I'm preaching to the converted.
George
 

Allen

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Jun 3, 2010
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Key West
This wingless aircraft is an ultralight I'm designing to build with 2" blue styrofoam and 1 1/2" PVC pipe for wing spars. Power will be a 22hp Briggs 4-stroke gas engine. meeceblog.wordpress.com
Here is an illustration of how the PVC pipes are arranged into the styrofoam ribs. The outboard ribs have rudders.
 

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Allen

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The spars will be covered in shrink-wrap plastic as is used to protect beached boats in winter. Of course there will be braces added to prevent the shrink wrap from bending the pipes. The cockpit module uses doorskin mahogany sheet to provide a rigid center box for the wing base. This looks E Z and affordable.
Any POSITIVE ideas? ;=] [Wiseguys stay away from this board please. Go to Twitter and talk to the Dumpster]
 

jedi

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Sahuarita Arizona, Renton Washington, USA
The spars will be covered in shrink-wrap plastic as is used to protect beached boats in winter. ..... The cockpit module uses doorskin mahogany sheet to provide a rigid center box for the wing base. .....
Any POSITIVE ideas? ;=] [Wiseguys stay away from this board please. Go to Twitter and talk to the Dumpster]
Yes!

Do not give up on your ideas but continue to learn and refine them. Thinking about blue foam and PVC costs nothing but gives concrete ideas a form.
Mock ups made of PVC and foam are quick and easy and will show weak areas and deflection under load. Once you have refined the design a hundred times and revised the mock up 20 times replacing a sub par structural pipe with a 6061 T6 tube is a no brainer.
 

daveklingler

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Jan 22, 2013
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Albuquerque
Allen, I'm assuming that your goal is to put together a design for a cheap, flying airplane that anyone can build with materials available at the local big box store.

This goal is held and is discussed daily by a large number of people on this forum. There are hundreds of designs for airplanes that meet your requirements.

Begin with Peter Sripol's experiments with foam on Youtube. Also look at the Sky Pup, the Bloop, and the Zing, the KR-2, and the Volksplane as examples of planes that use "cheap" materials.

There is a composite material readily available in a different section of your local big box store that's fantastic for airplanes, and really cheap: wood. If you look at the Fisher Flying Products aircraft (or the Zing, or many others), they saw a perfectly good piece of lumber into toothpicks, then carefully reassemble the toothpicks into an airplane. Very little wood is used, so materials can be very cheap. It's covered with Dacron from Joanne Fabrics, and can be painted, should you so desire, with house paint.

In the Southwest, where I live, Doug Fir is widely and cheaply available. In Florida, you might look for something else. Regardless, wood is cheap, easy to find in engineering tables, really strong, if used correctly, and easy to cover when you're ready.

PVC is good as a foam but it has a poor strength-to-weight ratio and low reliability as a tube. Blue XPS also has a poor strength-to-weight ratio in comparison to PVC foam, but you can make an airplane out of it with fiberglass from the store's paint section. Remember to sand the gloss off it, first. This is where the Peter Sripol videos come in handy.
 
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