Flex Research: First two builds

General Discussion
1

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).

 

2

open sesame

voila…it attached this time

 

I just updated the spreadsheet 1:10pm PST 4-July-2010

https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/surfboard_weight_AND_Flex.xls

3

[quote="$1"]

...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.

... [/quote]

Ok Benjamin, I'll make first shot at guessing which your test riders preferred. My guess is that they liked the stiffer board best. The stiff board is stock PU stiffness, so I expect your surfers who span from very competent to pro would be used to stock PU stiffness. I think they will find the more flexy board too slow and unresponsive however from reading your posts I will predict that of the test riders you will be the exception and prefer the flexy board.

However a test that interests me just as much would be for you to get constructed a stiffer than stock PU and hand it to the riders - my guess would be that they would prefer the more flexy stock PU over the stiff board. I cannot personally relate why riders prefer stock PU flex over a stiff board, but that seems to be the overwhelming preference on this message board and SurferMag message board so that would be my bet.

4

Ben, why did the weight go up after wet sanding?

5

Because the board was airbrushed, then glossed, then wet sanded, but the glasser didn’t weigh between these stages.

The glasser is a production glasser and pretty much everything I asked him to do was new to him.  I wasn’t able to be there when he glassed, so there are some mistakes he made and things that he forgot.  Still the work he did is quite good considering it was his first time.

If you look at the weight of the boards after every stage of lamination you would have to conclude that either the glass work was not consistent or he didn’t weigh them correctly.  I would asume a little of both.  Next time I am sure it will be better.  There’s a lot of learning going on here.

6

Before I give out the answer, consider that the boards are airbrushed white after they are laid-up, so that no one knows which board they are on.  The boards look identical.

1)Assuming you’re correct, do you think that the difference is subtle, mind-blowing or in-between?
2)Does everyone notice the difference?
3)Is the physical difference the same to everyone, but the preference is not the same for everyone?
4)Is the pro more tuned in to the difference or less?
5)Do some of the riders mistake the flex board for the stiff board, or do they unmistakably know which board they are on the instant they stand up?
6)Do the boards ride basically the same but just flex differently or does it feel like you are on a completely different board (different shape)?
7)If the riders prefer the stiffer board and we assume that it is because they are used to stiffer boards, after the third session (this morning) would they adjust their riding and learn to prefer the flex board?
8)Is preference learned or intrinsic…or a combination of both?

7

I just updated the spreadsheet.

8

A Marko lam will go on the next boards.  I didn’t get it in time for these.  And Graphite Master sticker will soon go on.

FCS, Graphite Master, Marko and Mitch’s Surf Shop have donated tons of hard goods to make this happen.

3024×4032 2.37 MB

https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/Deck.JPG

9

[quote="$1"]

1)Assuming you're correct, do you think that the difference is subtle, mind-blowing or in-between?
2)Does everyone notice the difference?
3)Is the physical difference the same to everyone, but the preference is not the same for everyone?
4)Is the pro more tuned in to the difference or less?
5)Do some of the riders mistake the flex board for the stiff board, or do they unmistakably know which board they are on the instant they stand up?
6)Do the boards ride basically the same but just flex differently or does it feel like you are on a completely different board (different shape)?
7)If the riders prefer the stiffer board and we assume that it is because they are used to stiffer boards, after the third session (this morning) would they adjust their riding and learn to prefer the flex board?
8)Is preference learned or intrinsic...or a combination of both?

[/quote]

Benjamin, you are going to have to tell me, I have no clue to the answers to the above questions. All my personal experiences tell me the lightweight stiff board performs the best - its faster and more responsive, however the elite surfers have a command of their boards that I can only dream of. I've also noted that I'm on a different planet from almost everyone else when it comes to stiffness.

10

In terms of rider preference, I think the results will be…inconclusive. Though the Longboarder may prefer the more flexible board, if he is a traditional style longboarder.

11

My guess is that the younger/quicker/more advanced/agressive surfer will prefer the stiffer board in a head high windswell. They will also prefer a ligher board. But in a more hollow, powerful wave scenario, they may prefer the flexier board.

Here’s my theory… I think the key to finding the right flex for a particular rider has to do with the rider’s natural pumping rhythm… if you’re a “fast pumper” or a “slow pumper”… for lack of a more PG-rated term. This assumes that the rider does not necessarily have to match the flex in a pump-per-cycle sense, but it has to be in sync… like one pump per two cycles. It just has to be in rhythm. LIke, 3 cycles per second means three pumps per second, or 1.5 pumps per second. Either one will be able to use the flex of the board to generate speed.

BTW… bottom contours?

12

Any video? Just curious

13

Come on - let us know!

14

I haven’t done much work on this project this last month, because I had to make some money…sorry:

http://www2.swaylocks.com/forums/best-board-comparison-application-everdebuting-sacred-craft

 

 

The pro hasn't ridden yet, and we don't have any swell for two more weeks.

answering the questions above:

1)very obvious for everyone, but I was the only one that was blown away

2)yes

3)physical difference is the same for everyone and there’s not really a
preference. The flex board you have to adjust your riding…different,
but not worse or better

4)we’ll see

5)the riders notice the difference the second they stand up and never
mistake the identity of the boards

6)you would NEVER guess that the boards are the same shape…it’s
totally transformational

7)yes, it took some time to adapt to the flex board

8)I still haven’t decided yet.

 

Honestly I’m am blown away by how different the boards
are…I’m learning A LOT…some of my theories need modification.  I’ve discovered more new questions and fewer answers. I’ll
post more details as we move on.

15

Hi Benjamin -

Nice work!  I'm always appreciative of someone who goes the extra mile to quantitate board data. 

Yvon Chouinard of Patagonia also did some nice work a number of years ago with destructive testing of standardized sample planks.  More recently Michael Ward did his PU/PE EPS/Epoxy comparison study with careful weigh-ins at each step with pro rider feedback.  I put your work right up there with theirs in significance.

It (quantitative testing) makes a lot more sense to me than listening to the typical shaper/salesman BS, with lots of hand jive thrown in, about this feature or that making a board "SOOOOO much more responsive" or whatever.

I also like that you've spelled out clearly what you did to engineer and construct the 20% difference in flex.  Good call on the engineering specs.  That sort of info, along with your other research published here on Swaylocks about lamination schedules is the kind of stuff on which we should be focusing IMO. 

I think the lamination schedule research answers clearly the advantages of multiple thin layers of alternating weave vs a single layer of heavier weave yet that type of  question continues to be asked. 

Keep up the good work and best of luck at ASR/Sacred Craft.

 

16

What you're proving is that build tech can make a huge difference in the way the board rides - even when shape and weight are held constant. Watch out, you may upset the status quo!

 

17

So... I did some work on the data that Ben posted.  I did this back when the xls file was first distributed.  I made a graph, uploaded the image, got distracted, and never posted it back to this thread. 

Somehow, Ben discoved my unpublished image and sent me a PM.  He provided a great explanation of what is going on in the graph. 

Here's his quote:

[quote="$1"]

I just ran into the plot you posted on my data. Is that attached to any thread?

Anyway, you actually plotted force vs displacement....which is always linear in the beginning.

Energy would be the integration of that curve. If you integrate a linear curve, you get a parabolic...the line would accelerate upward. Keep in mind though that only the energy in the linear region of the force curve is conservative, where the energy will be returned nearly 100% when the spring decompresses. Energy beyond the linear region of the force curve goes into changing the structural arrangement of the molecules (material damage). In this region a spring can no longer return to its original position.

[/quote]

Here's the original image.  I don't have the original Excel file anymore, so it still has the incorrect title.  The title should read Force vs. Displacement.

[img_assist|nid=1051209|title=Benjamin Thompson's Data|desc=|link=none|align=left|width=0|height=0]

 

 

18

Groan....

I feel like such an idiot.  Why can't I post an image?  I went through the whole process to upload the image.  I wrote my post, clicked on the little camera icon, selected my image, chose preview, and inserted the image.  It looked fine before I hit submit.  Now all I see is a little thumbnail.  What is the correct way to do this?

19

The image is here:

http://www2.swaylocks.com/swaylopedia/image/benjamin-thompsons-data

Just keep in mind that it is labeled wrong.  It should say “Force vs. Displacment”…not “Energy vs. Displacement”

 

20

“someone who goes the extra mile to** quantitate** board data.”

 

John, will all due respect, did you verbulate a noun? (ha)