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  #1  
Old 08-03-2022, 06:02 PM
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Default Carbon Fiber Tape Thickness

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?

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  #2  
Old 08-03-2022, 09:05 PM
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Default

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.
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  #3  
Old 08-03-2022, 10:21 PM
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Quote:
Originally Posted by rockitdoc View Post
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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  #4  
Old 08-04-2022, 06:43 AM
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Quote:
Originally Posted by DanH View Post
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.
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  #5  
Old 08-04-2022, 09:30 AM
David Paule David Paule is offline
 
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I could tell you the improvement if you tell me the thickness of the glass cowl there.

Dave
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  #6  
Old 08-04-2022, 11:18 AM
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Quote:
Originally Posted by David Paule View Post
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.
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  #7  
Old 08-04-2022, 02:52 PM
David Paule David Paule is offline
 
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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
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  #8  
Old 08-04-2022, 04:43 PM
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Quote:
Originally Posted by David Paule View Post
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'?
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  #9  
Old 08-04-2022, 09:01 PM
David Paule David Paule is offline
 
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Yes, of course.

I am in the middle of doing this for my oil door....

Dave
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  #10  
Old 08-05-2022, 06:42 AM
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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.
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