Corsair/Spitfire hybrid

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Will Aldridge

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Re: Robin Ultralight

Thanks for the info and effort to get it. Do you know what the limitations are on coiling it ie why they can't? That being the case I wonder if I could get them to cut 22 foot lengths and ship via semi?

I have also briefly looked into the possibility of a custom pultrusion. Ideally I would like a 2.5" x .015" section. I have read elsewhere on this forum that there are warping or twisting issues with thin wide pultrusions?
 

planebuilder

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Re: Robin Ultralight

the limitation is the bend radius. For the .125 diameter rods that was 18" so at 36 inches per package, you are right at the limit (length x width x girth) of UPS and FED EX. You can definitely ship them on a Semi, but the shipping and crating will cost more than the pultrusion. that option would only really be feasible if you were doing a very large order and if you were in production. I doubt the thinne sections would warp, but if they did, it would be a simple matter to straighten them. I bought 1200 feet of the .125" rod. When I got them, i made a huge mistake and just slit the tape. The **** things sprung out just like the clock spring of a tape measure. it took me hours to roll them up on a reel i could use to disperse them.
 

Hot Wings

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Re: Robin Ultralight

When I got them, i made a huge mistake and just slit the tape.

Empathize. I cut 2 tapes on my first batch and quickly figured out I'd better not cut the third. A couple few loops of safety wire replacing the tape was a satisfactory, but awkward solution.
 
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Will Aldridge

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Re: Robin Ultralight

It's hard for me to beleive that .019" thick material can't be coiled, it's a little less than 1/5 the thickness of the .092 stuff.
 

Will Aldridge

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I haven't been able to wrap my mind around any design issues lately but wanted to do something with this project, so I decided to apply my current fantasy paintjob to the plane knowing full well that red is not compatible with composites, but its' keeping the dream alive that matters.
 

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planebuilder

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Re: Robin Ultralight

You know I’m working for the company that built the original “Bent Wing Bird” Vought Aircraft. We have a plane that was restored by the Vought retirees , they just delivered it to a Museum in Dallas. I got a really good look at the spar carry though. The whole thing is machined from a steel forging. Besides “kicking” the wing spar loads around a corner, it also is the lower attach point for the engine mount and the attach point for the landing gear main trunnion. That’s a pretty efficient use of steel. They never had any fatigue issues with spar.

Designing a composite gull wing carry through is rather tricky. On the upper cap there will a normal tension load that points inward all along the bend radius in the outboard section, like wise for the lower cap. But in the inboard section this load vector will reverse. If were designing that type of spar, I would place a vert stiffener that connects the tangent point of the upper spar to the tangent point of the lower spar, and maybe an additional stiffener in between. The inboard section however where the vector reverses, might require a lot more stiffeners to react the tension load. That is a terrible direction to load an adhesive and in reality, some type of bolted girdle or plate might have to be used. corsair spar.jpg
 

Hot Wings

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Re: Robin Ultralight

That is a terrible direction to load an adhesive and in reality, some type of bolted girdle or plate might have to be used.

I was assuming that he might be planning on using kind of an outer shear web that passed over the top of the spar rod pack to keep them restrained and not de-laminating. I'm thinking that the spar caps in this area can be thought of as a whole bunch of little columns pined at their infinitesimally short ends and the problem ends up being how to restrain the pins?
 

Will Aldridge

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I'm using Rhino so here's what I did. I copied the file and then deleted all the extraneous stuff so I just had the outer shell, then I drew curves on the vertical longitudinal cplane and extruded them and used those surfaces to split the existing surfaces then i changed the layers and colors.
 

Will Aldridge

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Re: Robin Ultralight

Maybe everything from post #117 to this point could be transferred to Will's thread? I some times forget which thread I'm actually in. :emb:
That sounds like a good idea to me. Sorry for the hijack and thanks planebuilder your help.
 

Will Aldridge

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Re: Robin Ultralight

You know I’m working for the company that built the original “Bent Wing Bird” Vought Aircraft. We have a plane that was restored by the Vought retirees , they just delivered it to a Museum in Dallas. I got a really good look at the spar carry though. The whole thing is machined from a steel forging. Besides “kicking” the wing spar loads around a corner, it also is the lower attach point for the engine mount and the attach point for the landing gear main trunnion. That’s a pretty efficient use of steel. They never had any fatigue issues with spar.

Designing a composite gull wing carry through is rather tricky. On the upper cap there will a normal tension load that points inward all along the bend radius in the outboard section, like wise for the lower cap. But in the inboard section this load vector will reverse. If were designing that type of spar, I would place a vert stiffener that connects the tangent point of the upper spar to the tangent point of the lower spar, and maybe an additional stiffener in between. The inboard section however where the vector reverses, might require a lot more stiffeners to react the tension load. That is a terrible direction to load an adhesive and in reality, some type of bolted girdle or plate might have to be used.
That is a terrible direction to load an adhesive and in reality, some type of bolted girdle or plate might have to be used.

I was assuming that he might be planning on using kind of an outer shear web that passed over the top of the spar rod pack to keep them restrained and not de-laminating. I'm thinking that the spar caps in this area can be thought of as a whole bunch of little columns pined at their infinitesimally short ends and the problem ends up being how to restrain the pins?
Wouldn't a C-shaped shear web, with the caps on the inner side avoid that?
Here’s a picture of a Corsair spar. Maybe some ideas here?



Rob
spar.jpg

As you may or may not be able to see in this screen grab, I have incorporated a lot of the ideas you guys presented. Thanks planebuilder for helping me understand a little better the loads that will be imposed.

As you can see the wingspar is a c section sandwich(as opposed to the corsairs which appears to be an I-beam). I had originally thought to use foam core underneath the the spar caps as well as in the shear web, but I think maybe having the shear web attach directly to the caps is the way to go. And I was planning on having the shear web totally encapsulate the spar caps.
 

orion

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Unfortunately what works in a metal design doesn't always work in a composite. Although the mechanism of the force resolution is the same, the physics of material behavior is not. The metal spar is an "I" beam for a reason - it is a balanced symmetrical design - the channel is not balanced and due to that fact alone may result in out of plane motion. But even more seriously, the cap's motion tendency at the outer corners will have the greatest potential of fatigue and failure. I think this particular spar configuration is a really bad idea.

To stabilize the caps you will need reinforcement not only on the inside as you show, but also on the outside, resulting is sort of a filament wrapped box beam. But even then it'll take a bit of work to properly analyze since there will be deflections that could lead to secondary stresses. Be very careful on this one.
 

Hot Wings

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Here is a pic of what I think Orion is concerned about. It might help with the communication if nothing else.
Curve spar.JPG
 

Will Aldridge

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I actually had an idea kind of like #3 at one point. The center of the spar would have had a solid piece of 2 lb pcf foam completely wrapped in fiberglass then lay up the pultruded rod on the top and bottom then bond 5 lb pcf divinycell onto the front and back, then wrap the whole thing in fiberglass again.

I just ordered composite airframe structures by Niu. So hopefully that will give me some more insight into this. As always your comments have been read and appreciated.
 
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