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Wing design.

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RoarkS

RoarkS

Mechanical
Jul 10, 2009
264
So...
I have the plans for a Great Lakes biplane. I rent one on occasion when I need to go do upside down stuff. cool plane, just I really hate how the wings are made.

2x (fore & aft) spruce spar, with 2017 aluminum stamped ribs screwed in with cad plated wood screws... wooden drag rib, internal tension wires, and compression tubes. It's like transition tech between full wood or full metal wings... and an absolute pain in the rear to make. Did I say wood screws hold the ribs on? Seriously I would rather sit there with a exacto razor saw and build up wooden ribs glued together with resorcinol... or better yet... I teach aircraft sheetmetal... I could make a sheetmetal wing EASY. Past that... I think composite wings on a biplane would be amazing, but I know NOTHING about composite design (would like to learn if someone would point me in the right direction)

I just don't know how to go about designing it properly.
What steps do I need to do?

each wing panel is held on with 2 bolt in double shear to the fuselage (lower) or upper wing section (upper). There are N struts out board obviously... and of course brace wires.

My primary concern is I'm worried about getting roughly equivalent stiffness in the wing... I dont want to build an immovable rigid wing that would overload the bolt joints. So my thought is to do a strength analysis of the truss structure. I've never done something like that's real/that complex.

I have solidworks with its Simulation add in...

What do I need to do to minimize the need of a) using a parachute and b) loosing my $30k engine in a wreck?
 
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For a plane like a great Lakes, you may not want an advanced composite wing. Technically you have a composite wing now, it is wood metal and fabric, which is the old FAA definition of a composite wing.
Now if you are talking a molded plastic wing with re-inforced fibers, the modern definition of advanced composites , then you need to know that with the exception of carbon fiber re-inforcements , most molded plastic wings are heavier than the wings you now have on your bird. the only real advantage they have is that with the molded surface they can achieve true laminar flow over a greater percentage of the airfoil.
B.E.

You are judged not by what you know, but by what you can do.
 
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So things to note moving forward.
1:No wood screws. Only bolt holes or glue for wood.
2:I love AN470 Rivets. A carbon cub style wing would be awesome.
3:If I build a modern composite wing it will be lighter. Think Belite aircraft composite wing... not 40 year old Rutan urethane foam fiberglass open mold... which I'm still not entirely convinced would be heavier... though you're not the first to say that.
4: Google 3D printed spitfire and look at those wings... work of structural art. I'm not ready to take additive manufacturing wings serious but maybe someone can convince me with the maths... which is why I'm here... maths please.
5: I really don't want to change the performance of the wing... in fact I'm mildly terrified of precisely that. Remember in the dictionary next to the definition of aerodynamic drag is a picture of a biplane... it actually comes in quite useful. As long as she's got something on manifold pressure it's fine. Cut power to idle and put her in a slip... boom wings turn into Hoover dam and you fall out of the sky.
 
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You need to know that Aluminum rivets and carbon fiber are not a good combination , can you say battery ? Anywhere you want to put aluminum rivets you have to isolate the carbon fiber electrically.
B.E,

You are judged not by what you know, but by what you can do.
 
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I'd talk to a local kit plane builder, or people near you who modify planes.

As an owner/operator/builder there isn't much certification oversight (mostly it is "caveat emptor", but there is some involvment).

Designing/building a wing is not (as I'm sure you appreciate) something that's QED (quite easily done). To replicate stiffness isn't Too difficult to verify (ground test the original wing, design the new wing not meet the same stiffness/deflections, and then check the new wing). You need to understand the interactions between materials (like berkshire is telling you above) ... of course there are solutions for these problems, but you have to know.

Forming a composite wing could (would?) be very challenging. Remaking a wing (with doped cloth ?) could be challenging enough these days (another lost art ?). Designing the ply lay-up is difficult/artful, manufacturing the wing is another "world of hurt". You'd probably be limited to a room temperature cure, unless you have access to a large autoclave) and this I think limits your choices in composite.

I would if you could make a (female) mold for the wing from an existing wing ?

another day in paradise, or is paradise one day closer ?
 
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Does anyone know how to do math for wing structures?

 
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yes ... do you have something like 10 years ?

much is available online ... use at your peril.

another day in paradise, or is paradise one day closer ?
 
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Oddly enough that's exactly what I call this plane project to my wife. The 10 year plane.
I got a BSE in aerospace engineering in 2010... essentially worthless. D17.1 weld certs in TIG and gas welding...and a miller Dynasty... that took a few years to get proficient back in 2014 so I could do the chromemoly tube frame. I got my FAA A&P license not too long ago. Currently teach Aircraft sheetmetal fabrication at community college. My day job through all of this is a design engineer for aircraft weapon systems... nothing nearly as complex as wing design. And aside form that I'm just about done designing a radial engine out of lycoming o-360 parts.
Wings are the next step. I have Peavy and Bohn's books... but still a bit abstract for me. Looking for a little more direct experience.
 
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I appreciate that resume ! You are clearly not the loose cannon your previous posts could have been from !?

Doing a wing from scratch is a heck of a thing. Remanufacturing someone else's wing is much easier (you've already got a shape). Using an existing wing as a mold would seem to be reasonable. Your college should give you access to knowledgeable people and maybe the wing could be a college project ? you should be able to test the wing to verify strength and stiffness before you risk life and limb and fly it.

GL, share some pix when you get it done !

another day in paradise, or is paradise one day closer ?
 
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