pressure dents in new boards!

[munch]

Wanto,
After continously breaking boards, I ended up speaking to the the head of school at unsw (it was a while ago and can't remember his name, sorry!) and two of his students had done thesis on surfboards/how they break. Their conclusions were that they break in compression and he suggested that an extra two inch piece off glass along the stringer would help by increasing the density and creating more of a I beam type structure with the stringer - I've only broken one board glassed like this but it does effect the livelness/flex which is the trade off.

On the subject off "pressure dents" tow boards tend to be glassed with 2x6 ounce all over and they still get pressure dings - you could read into this a few ways:
a) they are a lot thinner ~2 inch and so none of the outer skin is left
b) they are used in heavier situations but I've seen them on the rail from duckdives
c) they were ridden to soon after being glassed
I would suggest it's a bit off a and c with the boards I've seen

[Dicco]

With the theory of the extra glass over the stringer cresting a I beam effect, I woukld agree but methinks that the glass would need to be bonded directly to the stringer to be an effective beam .Using kevlar on the rails should help a lot in ding resistance,But my experience is that kevlar has to be laminated with vinyl ester to be effective .Speaking of hybrid construction, one glass supplier showed me glass that had a 3
inch strip of Carbon fibre down the middle of the glass cloth - supposedly to reinforce the stringer or replace it .I thought what a laod of shit ! but then Im just a simpleton....
dicco

[mad]

You could go 3 stringers like some mals do. Just have to find a blank manufacturer willing to do it in a shortboard mould. It'll be a bit of extra weight but not heaps.

[Dicco]

Then, if you couldnt get the blank maker to put the extra stingers in ,perhaps your shaper could - before he started shaping ...
Year back I saw a Mark Rabiddge Mal that had "rail stingers in it - stringers around 6 inches from the rails tha wre bent to follow the shape of the rails - looked superb and the owner said it was as tough as hell . They didnt appear to go all the way thru the board though .Perhaps yoou should consider this approach ...

[munch]

to few characters.

[mad]

mad wrote:
You could go 3 stringers like some mals do. Just have to find a blank manufacturer willing to do it in a shortboard mould.
anyone know of a blank man. who does this?

Wanto, Burfords at Currumbin on the Goldy will do it. Ring em on 0755 34 3777. They'll probably ship it to Sydney, assuming that's were yez at.

[Dicco]

with the Carbon and polyester laminate you probably would get just a little stronger than S glass /polyester laminate. With a high grade epoxy yu will get a 3- 4 times stronger lamination ,BUT only stronger in tension .
Carbon has about 1/2 the strength of S glass in compression and around 1/3 the impact strength of Glass .So what you would wind up with is a laminate which if stretched would break at 3 times the load of a glass laminate but would break under 1/2 the load if compressed.Then if hit, would have 1/3 the impact/ding strength. Now when do you see a board being slowly stretched ? My experience is that carbon is used in yacht or racing car applications where it will always be in tension ,otherwise it is used with kevlar which bumps up its impact strenght dramatically
Quite often people will compare carbon laminated with yu beaut epoxies with glass and polyester and conclude that the carbon is vastly superior
My thought is that glass with good epoxy compared to carbon doesnt look all that bad
getting back to the original topic of pressure dents , Carbon when laminated properly should be 2-3 times as stiff as glass for the same thickness ( of glass and resin) , so one way of reducing pressure dents would be to cover the deck with carbon - then yu would have a board stiffer on the deck but the cost !