Two composite sandwich builds

[Surfdad]

I'm going to build two boards that are basically identical, but one will have a divinycell h45 @3 pcf foam skin and the other will utilize an aramid honeycomb @1.8 pcf skin. Pictures of the "stuff" that I'll use for the skins.

[Surfdad]

Divinycell (a cross linked PVC) is fairly cheap, readily available and conforms to complex shapes readily. It also has no shear strength and is as floppy as a wet noodle at the 3mm thickness that I am using. I prefer the stronger SAN as in corecell or PMI as in rohacell to the cheaper divinycell.

With the composite sandwich construction I can change the skin type from a HD foam to the aramid honeycomb...when I save my pennies I want to try an aluminum honeycomb also.

Propaganda from the Honeycomb retailers website:

Aramid Honeycomb is a lightweight, high strength, nonmetallic honeycomb manufactured from aramid fiber paper. After the honeycomb is formed, it is coated with a heat resistant phenolic resin to increase its strength.

Phenolic Resin is basically Carbolic Acid and Formaldehyde - all my favorite things! It is incredible rugged stuff, for any of the skaters out there, Skatlite is recycled paper and Phenolic Resin...old timers that worked on cars or in electrical componets will remember Bakelite - distributor rotors used to be made from the stuff and all sorts of insulators were made from it. Phenolics have high heat distortion and insulation characteristics. The Aramid fiber (it's actually paper ) also has high heat and insulation properties, the two in concert make for a very stiff core material, significantly stiffer than the Divinycell and in the dimensions I am using, is a lower density.

The honeycomb is marketed under the tradename Nomex. Nomex is typically associated with fibers used in fireproof suits, but this paper honeycomb is a staple in the composites industry.

Nomex comes in two "flavors" the hexagonal cells and a rectangular cell. The Hex cells are stiffer and the rectangular cells afford more drape - similar to the low density divinycell.

I hope to video the builds and post them up on wake9 - I have my own blog there now!!! Thanks Ragboy. http://www.wake9.com/blogs/surfdads-corner

I'll post pictures and some of the narrative here, but will most likely do the indepth at Robert's place.

[AdaminMN]

I was looking at using that honeycomb material fro repacing a deck on a sailboat. I was wondering if it could be used for a board as well. I guess we'll (you'll) find out.

[Surfdad]

It's been done before, typically not as the core itself, but as a skin with a laminated fiberglass facing. Hydroepic, which is now defunct, was probably the biggest manufacturer of HCB skinned boards. They were hollow with carbon fiber sikns and an aluminum hcb deck. The biggest problem they has was the seams of the board ran along the rails - the weakest point on a board and they would split!

The folks from Segway Composites created the same basic thing with their Kolstof line of hollow boards. I saw a prototype from the Cerritos College composites workshop. One of the issues for those folks with the aluminum hcb is that saltwater eats the stuff alive, so it requires significant protection and increased weight.