board strength via the rail

Hi,

I’m not a glasser or shaper (i just started doing my own repairs) but as a surfer who doesn’t much like pulling back i have an inherent interest in board strength ie snappability.

for my small-med all rounder boards i usually get 4ozx2 on the deck and 4x1 on the bottom. i sometimes get 4ozx2 deck and 5oz or 6oz x1 on the bottom if the board is for heavier waves. in the past i’ve had boards with 4ozx2 on the bottom as well, but these are noticeably heavier.

i’m keen to find a better solution for increasing strength without limiting performance, and i’m leaning towards more glass on the rails as opposed to more glass on the bottom and/or deck.

i’ve read about tubular strenth, and some of the modern day sandwich techniques all seem to boast that their strength comes from the rails, so why can’t we tap into this strength using traditional materials?

Firstly, lets just confirm that i understand how boards are generally glassed by the everyday shortboard shaper using the above diagram (stolen from another post):

firstly, bottom layer of glass laps up to E or D

secondly, both deck layers of glass lap down to B

Is that correct?

If that is the case, would there be any benefit in having one or both deck layers lap to somewhere between A and B instead of ending at B?

Now for adding some strength, i’ll describe what i mean using the diagram again:

bottom laps to E

1st top laps to B

2nd top labs to B

THEN an extra layer of glass (possibly 6oz) laps from D to A (or E to A if no weaker)

I’m hoping this would add similar strength properties as an additional layer of glass on the bottom (lapped over the rail).

What do you gurus think of this theory?

Anyone tried it?

I thought most of us did that anyway…

Except that when doing 2 layers of glass they are generally laminated as one…

Either way you still get 3 layers on the rail…

Hicksy:

yeah but … you are saying if i get 2x on deck and 1x on bottom i get 3x on rail … and that this is pretty standard. i agree. i still snap the f’kers like pencils.

i am saying if i get 2x on deck and 2x on bottom i get 4x on rail, and a heavy board.

my theory is that if i get 2x on deck and 1x on bottom, then add this extra layer over the rail (from D-A or thereabouts) i get comparable strength to the 2x + 2x with comparable weight/performance to the 2x + 1x … do you agree?

also, i failed to mention this in the first post: i plan on running the extra layer on the rail from about 1 foot down from the nose to about half a foot up from the tail.

thoughts?

ya gunna have to start again ther bro

composite boards get there strength from the sandwhich skin

rail glass has a different purpose

that is, primarily impact strength

The issue is the main strength of a board comes from the stringer/glass interaction, not the glass/foam interaction. Without a stringer you need a disproportionate increase in glass. Stick an inboard stringer 2 inches from the rail, and glass normally.

three layers of glass on a board and you effectively have a sandwhich

if you want a board that wont snap

you need to experiment with the sandwhich

sandwhich over low density core with good shear properties equals board that wont snap

chuck on some high densiity rails

and something changes

eps is a good start

it has better shear properties then hd PU

…there’s been a lot said about the strength of the board overall being in the rails…so check the archives…

But I can say that surfaces that run parallel to the stringer (perpendicular to the deck and bottom) help the board to resist snapping, so while increasing rail strength should reduce “snapability” it would only so negligably, because there’s not much vertical surface to the rail.

As already stated, the stringer/glass I-beam effect gives the board strength, so running a bead of resin, some roping, or an extra set of stringers down the middle will help increase strength by bulking up that I-beam.

Also… since in many situations flex is desired, almost anything you do to add strength decreases flex. So, like everything else, it’s a trade-off.

…notice that 1 of the deck layers goes to C or B (I do to B )

and the other to A

-you can put power rods too

Rail laps act as a channel, so in effect, you should be stiffening the board with an additional layer on the rails. Another method to stiffen/strengthen rails is the rail channel on the deck. A recent example of this is Stretch’s quads and/or shortboards. This stiffens the board (without adding much weight, if any) much like the difference between regular flat cardboard and corrugated cardboard. Can’t say what or how much difference it makes in snapping strength, but the theory behind it makes sense.

edit: Rail laps act as a channel, as in, channel iron. C-shaped thus adding rigidity.

thats kinda what i wanted to say as well NJsurfer

i agree

i think stiffening the rail with more glass for strength thoery, is just that.

a “theory”

it would stiffen the board

this would inhibit flex

therefore increasing its chances of snapping

i believe a thicker stringer and more glass on the parrallel plane to be the only truly effective ways

in traditional surfboard construction

but yeah then they get heavy.

basically

if you want a strong light board that wont snap

you need to go in a completely different direction

With a traditionally constructed surfboard, any extra glass on the rail will make the board stronger and stiffer. Most board breakage starts on the rail. Center stringers don’t offer much in that they allow the board to twist which puts more load on the rails. That’s why perimeter stringers are stronger, they give much more torsion strength.

With the extra glass on the rail, if you want to make the board strong but not make it too stiff, take out the center stringer, make the board thinner, or use bias weave glass for the extra glass on the rail. The bias weave glass is probably the best combination of strength without affecting flex too much, and not requiring any modification to the original shape.

thanks for all the thoughts guys. i really appreciate it. some great ideas, a few of which i’m sure to use.

part of the motivation of this idea is to keep my costs down. that doesn’t necessarily equate to the shaper or glassers cost (ie materials) but getting boards from the local shaping house anything besides standard comes at an extra cost, so i don’t really want to change materials or procedures too much.

blakestah re extra stringers:

i agree, more stringers = stronger board. two problems here tho.

  1. flex. my laymans understanding is that one I beam allows the board to twist on that axis. more than one I beam would stop almost all flex.

  2. it’s pretty hard to get my shaper to use anything other than the stock standard blank.

silly re eps:

are you saying the idea would be work better with epoxy?

NJ surfer re strength and stiffness:

i understand the I beam effect. i don’t understand how rovings increase this strength and have always thought they were a gimmick. as for the stiffness added by the rail glass, i’m hoping this would be less than an additional I beam, and less than an additional layer on the bottom.

reverb re power rods:

wtf? i’ve tried to find a clear explaination of what they are but …

surfthis re rail channel:

yeah, this sounds like an excellent idea. thanks.

silly re stiffness = snap:

i’ve heard this a few times; enough to stop discounting it, but it sounds more theory than sandwich strength. hopefully i get time to test both.

kenz re no stringer and bias weave glass:

how easy is it to get blanks without stringers? i’m guessing this would weaken the board somewhat (while keeping flex properties) which is kind of counter-productive.

now the bias weave glass idea: i used to have a shaper who would lay his glass on the deck diagonally. is that what you mean? or do you mean to lay the 2 deck and bottom layers straight up and down and then the extra rail glass diagonally? i like this idea, please elaborate.

i agree with kenz that perimeter stringers are they way to go

although i have different theories as to the reason why

there are two common types of perimeter stringer and they work in different ways

  1. a traditional 3 mm vertical stringer inset a couple of inches from the rail

  2. solid high density wood or foam rails

2 pd density eps blank with perimeter stringers and more glass on the horizontal plane

and biased weave on the rail

this is deffinately the right direction imo

where are you at Wanto

im sure someone could help you out

i’m in avalon, nsw australia. currently getting boards shaped by matt penn out of the insight factory (onboard) at mona vale.

i’ve had some varied quality glass jobs from them (they use about 5 different glassing houses) but am learning which glassers to avoid as a result. hopefully i can find someone willing to try some of this.

what do you mean by “solid high density wood or foam rails”? is that a difficult thing to do for a glasser?

can someone explain the biased weave concept?

thanks. paul.

solid wood rails aka firewire and a select few builders in this site

the hollow wood guys use them to

and us compsand guys use them as well

the eps guys use them to some extent as well

i guess now would be a time to do a few searches in the archives and readup a bit.

also these guys do it commercialy in the states so it gives you an idea whats out there

http://www.segwaycomposites.com/FoamBlanks.html

check the contour stringer for type 1. version

and yes

epoxy resin all the way

it may turn out theres a swaylocker that makes them close to you

i make my own for a grand total cost of $40 NZ

Quote:
can someone explain the biased weave concept?

You got it right, it’s with the weave oriented diagonal at 45/-45 instead of 0/90.

Basically, when you have at least a triaxial composite with glass running at 0/45/-45, you are creating thousands of tiny triangles, which as you know, are the strongest structure. This will help prevent breakage.

Quote:

so why can’t we tap into this strength using traditional materials?

You can but when you consider the extra incredible performance and the strength to weight ratio of compsands there really is no question as to what works better. plus compsand is 100% still stronger.

The solid wood rails on compsands act as paralell stringers and just totally blow away any competitors in terms of strength and performance.

josh, forgive me but you sound a little biased.

i might try a compsand one day, but i’m betting they would have zero (0) flex, and really would cause a few headaches for my local shaper and glassers who likely have never seen a compsand made let alone attempted it.

i’m sure they are light and strong, but that doesn’t necessarily equate to performance. although i am interested to try it out i’ll hold my breath until i have the time and money to try one out (which isn’t gonna be real soon).

kenz,

  1. why isn’t biased weave standard?

  2. would you suggest glassing the board normally (non-biased) then adding a biased rail layer?

thanks.

Quote:

josh, forgive me but you sound a little biased.

Yes you are correct! sorry.

Take a good look at Stretch’s Fletcher 4-fin model. The top has grooves or channels just inside of the rail. That’s a great way of adding strength. It’s similar to what car designers do to add strength to side panels.

I bet those boards are difficult to glass.

Another way would be to make rails similar to what Jeff Alexander does on his Gemini boards. Adding extra curves gives more strength.