Here's the fin build and final product...bear with me and the explanations:
Layed up god knows how many strands of 24oz roving lengthwise up the fin, horizontal ones are added in the base for strength and tab protection...
Wetted out both sides and then put together under about 50 lbs of weight to squeeze out the excess resin (did not use the vac bag this time, I didn't know how much resin would flow out of the mold in the process and didn't want to risk it yet).
Two hours later I pulled the fin from the mold and this is what where that leaves us before the finish work; its 90% there though...rad!
The fin with the excess cut off and some bubbles filled with resin and sanded flat.
Then the fin got some bondo to fill the rest of the PITA little holes, and some spray paint to cure boredom...yes, the fin is not perfect cosmetically, but I will claim that the flex feels absolutely amazing in hand.
I will take a short video tomorrow of this fin vs. a volan fin and they way the they flex; in so many words I would describe it as twisty...around :34 and then some in this little clip shows the type of flex I'm going for...the muscles of a tuna fin run lengthwise up and down the fin vertically, so it only makes sense to copy it with fiberglass for a more similar flex pattern:
I'd say this fin flexes with a much more similar shape as compared to a volan or other flat weave fin in the way the the tip bends under and waves like a paddle...very excite!
This whole project was spurred by a mention of Greenough's fin building process with plywood molds; i decided to use fiberglass ones but it's the same idea, and he's a genius.
Much more experimenting to do, but I'm really pleased with the first version :)