Use of carbon fiber pultrusions in extreme lightweight wing construction

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patrickrio

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I am looking for Builder logs, Drawings and Specifications for very light airplanes that use carbon fiber pultrusions in wing construction. I want to see what variations have been used to date to utilize the benefits of pultrusions. I am particularly interested in designs that used carbon fiber in the d tube also.

It is probably a pretty short list....

Criteria is:

Must use CF pultrusions in spar caps
Gliders with empty weight of below 220lbs
Motor Gliders with empty weight of below 300lbs
Airplanes with empty weight of below 300lbs

Here is the first airplane, the Monarch... link for Carbon Monarch and Monarch G with an added carbon spar link.
Carbon Monarch Build Log (links to previous pages at bottom of page)
Monarch G Builders Manual
Marske Page on using Carbon Fiber Pultrusion Rods
 

patrickrio

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Pretty sure it would be cost prohibitive to do the "pulled D tube" for a wing. The setup costs would be immense and you would need to do hundreds of feet at a time... and it would be a constant D tube the whole length which would be a waste of the capabilities of composites really...

I am thinking the ideal currently would be an epoxy infused CF fabric open D that gets closed to a D tube with the spar.

The spar I am less sure about. It seems the easiest would be a CF infused C spar like in the Marske link above.

I wonder though if you could include the pultrusions at the edges of the Dtube infusion layup, and then use an adhesive to attach a carefully CNCd foam spar web between the pultrusions to close the D tube out.

In any case, I am looking for different ways that pultrusions have been used in light wings, regardless of if additional CF is used in the rest of the wing.

I am particularly interested in seeing different ways that pultrusions are laid into the caps and how those variations affect the results.
 
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sming

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Check the Klingberg mark 2 wing series on youtube, lots of good info on how to build a 15m 100lbs flying wing...
 

patrickrio

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Check the Klingberg mark 2 wing series on youtube, lots of good info on how to build a 15m 100lbs flying wing...
should have put Klingberg wing in first post.... I have watched most of those videos and just forgot to include...
 

wsimpso1

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Pultrusions as caps in spars? Cool. Fiber orientation is along the spar as needed, and is easy tapered along the span to tailor strength and/or stiffness to the bending moment.

Pultrusions in webs and D-tubes? How would you even build them with pultrusions? How would you connect the web to the cap and get the loads between them?

Have I missed some innovation in pultruded sheet with fibers on the bias and conforming around the caps or D-tube?

Most pultrusions are axial fiber bundles, which works great for spar caps. Spar webs and D-tubes are usually made up of fibers at +/-45 degrees to carry shear. In a 200-300 pound sailplane, the web and D-tube would each need to be no more than a very few plies of 6 oz cloth on the bias and then it would be molded to wing profile - it would be a tough task to bend a pultruded sheet accurately around the rib shape.

Billski
 

BoKu

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...fibers on the bias...
Yup they're doing that these days. The keywords are "braiding pultrusion." As you say, it's only for constant sections, and as you might expect, the minimum thickness appears to be too thick for lightweight aero structures. But it's certainly a thing to keep an eye on. Braiding plus uni might someday be a good bet for cost-effective wing spars for strut-braced LSAs.
 

patrickrio

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Klingberg spar is interesting in that he uses REALLY small rectangular pultrusions. So small he needs to group/epoxy them together first to work with them.

He also put the flat bundles flat against the sides of the web at the ends.... see in this video:
 
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patrickrio

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Pultrusions as caps in spars? Cool. Fiber orientation is along the spar as needed, and is easy tapered along the span to tailor strength and/or stiffness to the bending moment.

Pultrusions in webs and D-tubes? How would you even build them with pultrusions? How would you connect the web to the cap and get the loads between them?

Have I missed some innovation in pultruded sheet with fibers on the bias and conforming around the caps or D-tube?

Most pultrusions are axial fiber bundles, which works great for spar caps. Spar webs and D-tubes are usually made up of fibers at +/-45 degrees to carry shear. In a 200-300 pound sailplane, the web and D-tube would each need to be no more than a very few plies of 6 oz cloth on the bias and then it would be molded to wing profile - it would be a tough task to bend a pultruded sheet accurately around the rib shape.

Billski
Yes. in the spar caps... I may have used wording other than standard to show how the pultrutions are oriented. Essentially, even when oriented alongside the web toward the edges of the web where traditional I beam caps would be, the pultrusions become the effective caps. I just think is is interesting that some constructions put them alongside the webs so that the effective caps are closer together than they could have been for a given wing thickness.

It seems like it would be better to kind of concentrate the pultrusions stacked in the corner made by the wing skin and the web.. formed into a kind of triangle to get the pultrusions as close to the corner as possible.

it seems some have them flat to the skin though, and some put them flat to the web.
 

patrickrio

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Yup they're doing that these days. The keywords are "braiding pultrusion." As you say, it's only for constant sections, and as you might expect, the minimum thickness appears to be too thick for lightweight aero structures. But it's certainly a thing to keep an eye on. Braiding plus uni might someday be a good bet for cost-effective wing spars for strut-braced LSAs.
The third machine in this video (continuous lamination) shows a machine making a continuous flat pultruded sheet that is then put on a roll. They can use the same first part of the continuous lam machine, but bend it into a d tube shape instead of making it flat. Then they have to cut the resulting 3d shape to length on the machine because it obviously will not roll up any more..... The sheets can be any combination of fabrics with plies going in any number of directions. But as Boku says, they currently have to make the sheet too many layers thick to be useful for small planes. AND as he says and as you can see in the video, the shape will be the same along the whole length of the D shaped pultrusion.

They can currently make the flat laminations very thin though, so maybe soon they can make the very curved ones thin also. The key will be to make dies cheap enough that smaller runs can be done cost effectively too.
 
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stanislavz

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Another black plywood thread ? Do you already tried to build any parts with hand laminating ?

Making D tube is easiest part per whole aircraft. And you can tailor ply orientation and thickness as you want. Plus you can make it with same Jim styled corrugated ribs in place.

Plus - again Jim words - for D tube skin hand laminating is ok - it is thicker and more rigid due to higher epoxy content.
 

rv7charlie

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Check the Klingberg mark 2 wing series on youtube, lots of good info on how to build a 15m 100lbs flying wing...
Well, the video that's 1st up on that youtube channel isn't exactly encouraging...
edit: May well be a different design, but it's the latest posted video on the channel.
 

sming

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Read the comments on the video, there is some informations. It's an old crash of an archeropteryx (?) were the pilot pulled to much Gs.
I think the first flight of the klingberg wing is scheduled today or something ?
 
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