Yesterday I showed some pictures about why I have chosen to put the carbon fiber on the inside of the Divinycell instead of the outside.

Below are photos of tests I made about 15 years ago. Those tests convinced that placing carbon fibers on the inside of a sandwich construction makes it way more stronger than to have them on the outside, regarding impacts.

These two samples each are laminated with carbon fiber. The left one on the inside, the right one on the outside. Hitting them with a big hammer the right sample was easily penetrated the left one got a dent but no more.
The inside of the same two samples. The left one with the carbon on the inside shows no damage. The right one with carbon on the outside is completely penetrated.

Clearly the difference to impact impact is like day and night. It is no more difficult to or not much more difficult to put the carbon on the inside than on the outside, but it so much more safe. My advice to builders of small ocean going cruisers: Use carbon fibers on the inside to get a strong safe boat.

To be continued…

Regards Yrvind