Just to throw in another variable… how often are you loading the board equally under both feet? I’d say almost never on a modern short board, when generating speed is about pumping, squeezing water through concaves, etc. You almost have to consider the point under each foot separately, and on top of that, the change in pressure under the board as the flow of water increases and decreases velocity…
I believe the board hinges under each foot more than in the middle, giving a recurve to the board instead of an arc.
I actually had to mix together ideas from about 3 different bow designs then tweak them work in a board. I made it out of ceder since many of the other suggested woods were impossible to get.
Any follow-ups to this very interesting thread? Who has ever tried the horizontal stringer concept?
I think horizontal stringers can be optimal only with a very flexible board construction to which the horizontal stringer is added, flat deck is my guess right now, but achieving enough volume without having blocky rails would mean only width could be played with… or making parallel profile boards like Roy for having the best volume fo the best flex. The latter construction means no tapered foil and rails, but a very controlable neutral axis, then what would be lost by not tapering the foil/rails? Any thoughts?
a big light went on in my head when i read your sandcomp thread. the way you do the rails is what i think is the key. you took out the vertical “stringer” that “normal” sandwichboard have. due to the vertical sandwich on the edges the board stiffens to much. and i think your right that its not so much about flex but flex behaviour. as faster as the board moves back to its original shape as more stored energie “pushes back” after a turn or the board moves back to the most effective shape after a curve or bump.
windsurf sail masts made from carbon come 4 times faster back after moving the sail out of shape and bring the sail faster back to its most effective shape, so that you can use bigger sails and “hold” it and be faster
the thickness of a board decides the amount of flex (thicker=stiffer)
theorie
a carbon made surfboard would probably be to stiff. but if you just ad carbon bands at the edges or wrap the edges (top and bottom) the board would move faster back in shape and you could decide the amount of flex by putting the stripes further torward the middle of the board = stiffer= heavier surfer, further outside= flexier= lighter surfer and keep all other materials/processes the same. the carbon could be protected under the glass.
all this is just my honest opinion and theorie ( i only made one (polyester) surfboard in the last 38 years)
uzzi
ps. thanks to your thread i’m infected now. i’ll be at home in 3 weeks and the material is allready ordered.
You could easily make a board with all carbon, but finding a layup that worked well would be quite difficult without mass trial and error or sophisticated math/engineering stuff.
nathan, i think lost did some and i think you’re right it would cause mass trail and error and carbon has some disadvantagdes as well. it is not very impact resistent, uv sensitive and would double the price off a board. just some well placed bands protected under the glass layer and “adustable to surfers wight”.
Yes. Thinking about, designing with this esoteric non-sense we call the NA is a total waste of board building intellectual energy.
Case in point: its very easy to make a very stiff compsand board. If you dont like stiff, changes must be made if you want the buttery feel on a poly. Moving stiffening/reinforcing structural components (ex: center stringers) is one way to alliviate the problem. Once you accomplish getting the buttery feel of a poly, then you can start to address the fuzzy esoteric stuff…but only if youre just plain bored.
There’s been some talk about hourglass horizontal stringers, etc. to control flex.
For what it’s worth I think the skies pictured are trying to achive something else than becoming softer at the cutaway area. You have to look at the foil at the same area, remember twice the width, twice as stiff, twice as thick FOUR times stiffer. For what it’s worth, IMHO the skies are either trying to make the areas less torsionally stiff(for a more cusion/forgiving ride) or more torsionally stiff at the tip(more likely, look at how the beam from outer edge crosses over into the other side in the center of the cutaway). Most likely though it’s hype/marketing gimmick.