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Author Topic: Carbon fiber trailing edge and leading edge for P30 wing, and C/F spar joiners?  (Read 294 times)
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PantherM100
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« on: May 15, 2021, 02:39:50 PM »

Hi Guys:  I would like to explore using Carbon Fiber leading edges, trailing edges and and
Spars. First off:  The leading edge, I assume would use very light weight C/F Tube. About
.040” to .050” OD would match the nose radius of the airfoil, (USA 5).  The Trailing edges
I’m not so sure about.  My concern is the shape.  Are they made with a triangular outside
Cross section?  Is there typically a Vee shaped inside profile or are they typically a solid
Rectangular strip??  Or I guess I could make the T/E’s from tubing also.
The ribs will be balsa, capped with less than.005” x .050” wide C/F strips.
The spar I know can be made from very, very, light weight approx 5mm C/F tube,
Like the Russian made material that Mike wood house sells. By the way what is the
Current methodology for spar joiners???
Sincerely,
Jon B. Shereshaw

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Tapio Linkosalo
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« Reply #1 on: May 15, 2021, 11:50:10 PM »


For the leading edge, I use balsa. I doubt that the thin tubing would work, as the covering tends to tighten to the tangent of the surfaces, and thus between the ribs it probably would not follow the shape of the ribs, but would tighten from leading edge to the spar, thus resulting in a very sharp and triangular airfoil. Or, you would need a lot of riblets to keep the airfoil shape. I'd rather suggest laminating a narrow D-box from thin carbon laminate for both the LE and main spar. Some 15mm (or half inch) wide would suffice for a P-30.

For the trailing edge, I use strips of 2*0.5mm solid pultruded carbon, square. They are so narrow that it makes no difference whether they are not triangular. Note however, that you need carbon caps to support the joint and the very thin ribs at the trailing edge.

 
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Tmat
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« Reply #2 on: May 23, 2021, 03:39:29 PM »

Evgeny Gorban uses 3 mm OD carbon fiber tubing leading edges on his F1G stabilizers and even smaller OD on his fins. So it definitely can work.
For P30, a small diameter carbon tube can work, but as Tapio says, I suggest some very light riblets up to the spar to preserve the airfoil. 0.5 to 0.8 mm balsa riblets weigh almost nothing.
5 mm OD tube for the spar is overkill Imo for P30. I used 4 mm tubes for the center panels and 3 mm tubes for the tip panels. I think there is no reason why you couldn't use 3mm carbon tubes for the whole wing.
I use 0.5 x 1.6 mm carbon rectangles for the trailing edges (ribs carbon capped overlapping onto the trailing edge and leading edge).
DPP pultrusion makes a 0.6 mm x 1.6 mm carbon tapered cross section trailing edge stock that works well also. https://www.cstsales.com/carbon_te.html#821
It's amazing how little carbon fiber you need to get the job done. A friend of mine used a 0.8 mm (1/32") diameter carbon fiber rod for the trailing edge and it worked a treat! But stick to 1/4 mil mylar (7 grams/sqr meter) only otherwise it can distort the trailing edge when heat shrinking.
I've attached a drawing of one of my P30's using carbon fiber tubes.

Tmat
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Re: Carbon fiber trailing edge and leading edge for P30 wing, and C/F spar joiners?
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F1B guy...
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Tmat
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« Reply #3 on: May 23, 2021, 03:43:28 PM »

For the joiner between two carbon fiber tube spars I first wrapped aprox 1/2" (12 mm) of the end of the tube with Kevlar thread (to prevent splitting). The joiner is 0.8 mm (1/32") G10 fiberglass plate (or 1 mm plywood) that fits vertically into the tubes. Then it is just glued together. For P30 it is more than enough.

Tmat
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PantherM100
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« Reply #4 on: May 24, 2021, 05:58:31 PM »

Tmat:
I can’t read the weight of your wing.  Could
You please let me know?  It also appears to over
The length limit of 30.0”  I think you are measuring
The projected lengths, but perhaps the dims are the
Flat plan lengths??
Sincerely,
Jon B. Shereshaw
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