Ok the first two boards were built and have been ridden. Two guys of same weight switched the boards every 20 mins in the water. Two different days, head high windswell.
Specs:
6’0" x 11.4" x 18.75" x 14.6" x 2.25"
squash tail, thruster FCS plugs, FG-5 fins
Volume: 28.7 L
Surface Area of bottom: 6.9 sq ft
Centroid of Surface Area: 34" from tail
Weight: 4.75 - 5 lbs without fins, pad or leash
Attached is a spreadsheet of the weight of the board at every stage of the lamination (inspired by Surfding). It also includes the temperature of the room and resin (before mixing). The glassing room was temp controlled, so it was always the same. The spreadsheet also explains the stiffness of the board.
The boards cured for a week at 75F and got about a total of 1hr 120F oven time. Then I did the resonance test with two different people. Here’s the link for how a resonance test is conducted.
http://www2.swaylocks.com/forums/hard-numbers-flex-demystify-flex-patterns
With the resonance test, you can make a first order caculation of the stiffness (or flex) of a surfboard, if you ignore damping. The calculation is found on this post:
http://www2.swaylocks.com/forums/hard-numbers-flex-demystify-flex-patterns?page=1#comment-1347919
So I engineered them correctly…20% difference in flex. The stiffer board is about the same stiffness as a stock PU with double 4oz on top and single 4oz on bottom. The other board is 20% more flexible. Assuming that the natural frequency is closely related to the recoil rate of the board, the stiffer board recoils 10% faster than the more flexible board. Assuming that the boards experience the same loads, the rocker of the more flexible board will bend 20% more than the stiffer board. So! let’s say that the 1" is added to the rocker when the stiff board is loaded at 2 Gs in a turn. If the more flexible board is also loaded at 2 Gs in a turn, 1.2" would be added to the rocker of the more flexible board.
Unfortunately, I chose the lamination schedule that was optimized for severe impacts and weight. The downside is that it is more vulnerable to pressure dings…which it is already showing under the front foot after two sessions.
As far as performance…hahahahaha…(that’s an evil laugh, btw). Well, like when I teach a structures class, I’ll let you guys debate over it before I give you the answer.
Here’s how structural performance questions go:
1)What is the difference?
2)Is the difference at a level of signifigance?
For each of the four riders, can you answer these questions above???
a) Me, 157lbs 6’0" 29yearsold regular foot 5years surfing…pretty average, but I stick airs a couple times a week, not good at tubes
b)Jeremy 157lbs 5’10" 24yearsold goofy foot 10years surfing…above average, well rounded, longboards about half the time
c)Don 157lbs 5’9.5" 48yearsold goofy foot 33years surfing…totally rips, but not above the lip
d)Ex-pro 155lbs 5’10" 31yearsold regular foot 20years surfing…pro level surfer (keep in mind that this board is a tiny bit too big for him).