Hi all,

I'm new to this forum and new to carbon fiber composites in general.

My current project is a mast for a sailboat dinghy.

As my first question on this forum, I'd like to ask if my logic is sound regarding the strength of a carbon fiber component.

I have a hollow wooden mast 12 feet (3.6 meters) high and would like to replace it with a carbon fiber mast of the same diameter.
The wooden mast is 3 inches (75 mm) in diameter with a wall thickness of 0.75 inches (20 mm).

(The carbon cloth I plan to use will be bi-axial twill sleeve, along with West System epoxy.)

When I compare the material properties of the wood to the carbon fiber, I find:
in compression, carbon fiber composite is between 12—16 times stronger
and in tension, carbon fiber composite is between 9—12 times stronger.

As I understand it, I can build the dinghy mast with the same height and diameter.
If I divide the wall thickness of the wooden mast by 9, I get 0.08 inches (2 mm) for the corresponding carbon fiber mast.

So a carbon fiber mast with a wall thickness of 0.08 inches (2 mm) would be similar in tension and much stronger in compression than the corresponding wooden mast.

Is my logic sound?

Thanks for your help!

You have to take in consideration as to what exactly the strength values of the carbon fiber means.

In the material properties I noted, the high value is what I calculated for unidirectional along the fibers.
The low value is what I calculated for 2x2 bi-axial twill cloth.

The sleeve would be oversized, so the fiber orientation would be a bit less than 45 degrees.
Wouldn't that make it stronger than the low values?

I thought I was being pretty conservative in my calculations.

Having the angle less than 45* will give additional torsional stiffness, but will reduce the stiffness along the length of the mast (compared to a unidirectional fiber).