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Carbon Fiber Tape Thickness

rockitdoc

Well Known Member
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I am using Skybolts to hold my cowl on. Builders have reported bulging of the aft cowl in flight even with Skybolt distances at 3". Therefore, reinforcing the aft edge of my cowl will be done to prevent this as others have done to good effect. I plan to use some carbon fiber tape (2.9 oz. Carbon Fiber Uni-Web - Gaps) for this purpose epoxied 2" wide to both the inside and outside of the cowl for stiffness.

Question: if the carbon tape is 0.008" how much thickness will it add to the cowl after epoxying? I would like the cowl to match the firewall in elevation so a shim will be used to compensate. Currently, the stock 0.032" shim is under the Skybolt flanges shown, but is this enough?

Skybolts port side spaced at 3-1:8%22.jpg
 
Seems like any material used on the outside would be difficult to hide. I epoxied a strip of light aluminum on the inside of mine. Still has a slight pillowing at speed but not ugly.
 
Question: if the carbon tape is 0.008" how much thickness will it add to the cowl after epoxying?

I'll say 0.008 for a wet layup, but it's hard to be precise. A high modulus carbon strip inside and outside is the right idea.

The edge shown below had multiple plies of glass tape added to the inside. The glass was intended to be a shim as well as stiffen, but it isn't quite stiff enough when I close down the cowl outlet.
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I'll say 0.008 for a wet layup, but it's hard to be precise. A high modulus carbon strip inside and outside is the right idea.
.

The idea came from you, Dan. Thanks. And I know others (wire jock) are using it, as well. I will plan on 0.008" x 2 . The shim is 0.032" so if there is still a difference in elevation between the cowl and firewall I'll build it up with epoxy bodywork and sand to match precisely.
 
I could tell you the improvement if you tell me the thickness of the glass cowl there.

Dave

Ten readings were as follows in thousandths:

64
68
72
78
66
110
80
68
71
66

BTW, I plan to lay the fiber in a two inch strip along the edge of the cowl.
 
The carbon will make the .064 thickness 7.2 times as stiff, roughly, and the .110 thickness about 4.3 times stiffer. For the other thicknesses, it'll be somewhere in between.

Dave
 
The carbon will make the .064 thickness 7.2 times as stiff, roughly, and the .110 thickness about 4.3 times stiffer. For the other thicknesses, it'll be somewhere in between.

Dave

Dave, did you figure carbon on both sides of the fiberglass, ie, a fiberglass sandwich between two pieces of carbon 'bread'? ;)
 
That's a big increase in stiffness. That will reduce or even prevent bulging of the cowl between the Skybolts in flight. Especially with the 3" spacing. Problem now; I am anxious to try it out! Thanks for doing the analysis. It puts a quantitative value on the carbon reinforcement.
 
Carbon Fiber

I'm cheap & lazy. I bought a yard long ago. 36x60 is $35.
https://www.aircraftspruce.com/pages/me/carbonfiber/bigraphite.php
Last of it went on my plenum. Scraps are getting cut as needed into 1" strips for reinforcement. Tiny bits get run over and over with the fabric cutter into flox. I keep it in a pill bottle. Carbon flox is awesome for super strong fillet repairs.
If you're careful, very little is wasted.
 
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I'm cheap & lazy. I bought a yard long ago. 36x60 is $35.
https://www.aircraftspruce.com/pages/me/carbonfiber/bigraphite.php
Last of it went on my plenum. Scraps are getting cut as needed into 1" strips for reinforcement. Tiny bits get run over and over with the fabric cutter into flox. I keep it in a pill bottle. Carbon flox is awesome for super strong fillet repairs.
If you're careful, very little is wasted.

Good to know I’m in the same club.

I just bought a 12” x 48” piece of uni 0.008” thick for $13
 
Oops!

I should have asked what 'gaps' meant when I ordered this carbon fiber tape from ACP Composities at their garage sale.

Oh well, I know now.:eek:

Carbon Fiber Tape w: Gaps.jpg
 
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