Surfing Waves

Epoxy boards do snap!

Found this on MSW

Mate, no matter what construction method is used, you can snap a board.

The thing with epoxy is that it has greater tensile strength than polyester. This means basically that for the same strength of laminate, you can use less epoxy than polyester. Board manufacturers can use this to produce an equivalent strength board with less materials (ie resins). The end result is a board of similar strength to a poly board, but of substantially less weight.

The problem is that this is not consistent between manufacturers. Some manufacturers use the increased strength of epoxy as a selling point, saying their boards are ding-proof/snap resistant. These boards use more resin, and are the same weight as a poly board, but a lot stronger (not indestructible however), where as others make lighter weight high performance boards that are just as fragile as poly boards.

The other significant difference between epoxy and polyester resin is the flexibility. Polyester will flex much better than epoxy (due to the cross-linking properties of sidechains in the molecular structures of the resins) and as a result, polyester tends to dent and flex, but rather than crack or shear. Epoxy, by contrast, tends not to deform until it reaches breaking point, at which point there is typically structural failure of the polymer.

It looks like the guy in that photo has simply overloaded the board (not sure what kind of surfing he was doing) but due to the lack of a stringer in the blank, the epoxy sheets simply were stressed beyond their limits.

As a side note, if I were looking for a high performance board, I wouldn't touch one without a ply stringer down the center, as the timber gives far more strength than an epoxy-foam sandwich construction board can ever have (think steel "I" beam versus a sheet of flat steel).

Jimi wrote:The other significant difference between epoxy and polyester resin is the flexibility. Polyester will flex much better than epoxy (due to the cross-linking properties of sidechains in the molecular structures of the resins) and as a result, polyester tends to dent and flex, but rather than crack or shear.

Jimi, you bring up a good point about the flexibilty. I like the fact that poly boards do flex. The idea of riding a rigid or stiff board reminds me of a "dead" board that doesn't give the rider much feel. Also the corkiness of epoxy boards is not to my liking. All of my boards are glassed with (2) layers of 6 oz on the deck and (1) layer on the bottom. They might not be the strongest of lightest, but I can fix them myself. JMHO

I totally agree. That's why so many epoxy boards are total rubbish. It takes a totally different approach to board design to allow an epoxy board to flex, and the end result is still different to a poly board.

There's a mob in Aus doing epoxy boards with some special flexi tail to allow them to generate more drive out of a turn (the board loads up like a spring during the turn, and straightens out afterwards, giving you better speed down the line). I'd love to have a surf on one, but I'm probably not good enough to appreciate the differences.

P.S. you can still fix an epoxy board yourself, and it's no more difficult than poly to work with. Just go to a proper resin supply store, and buy a tin of epoxy with the correct amount of hardener (it's critical to mix epoxy in the correct ratio or it won't set properly).

All boards will snap if you are in the wrong place at the wrong time! I rode polyester boards for 14 years before I tried an epoxy Surftech. I used to snap 10 boards a year and since riding for Surftech I have only snapped four boards in five years! Definetely stronger strength to weight ratio. You have just got to get used to the way they feel at first but once you get used to them there is no turning back

Well now, of course they can snap. Anything can snap if enough force isd applied to it in the right way.

Interesting comments on composite construction (aka epoxy) boards. I am especially interested in the comments about lack of flex in epoxy/composite boards, compared to PU.

Please consider an exercise on an "epoxy" (OK, ok, Compsand) board upside down and rightside up.

As I originally posted on the Bouncy Bouncy! thread.

I suspect the "flextails" you are talking about are, in fact, properly designed and built custom composite boards. I suspect your "epoxy" experience is based on mass produced chinese popouts

The aussie guys you are talking about are probably Bert Burger from Sunova. But there are also a couple of other Aussies who build these who I can put you in touch with if you really are interested.

-doug
Compsand.com!

dougirwin13 wrote:Interesting comments on composite construction (aka epoxy) boards. I am especially interested in the comments about lack of flex in epoxy/composite boards, compared to PU.

Please consider an exercise on an "epoxy" (OK, ok, Compsand) board upside down and rightside up.

As I originally posted on the Bouncy Bouncy! thread.

Doug, I was thinking of "Firewire" http://www.firewiresurfboards.com/learn_technology.php
but it seems pretty similar in concept to Sunova.

Also regarding the lack of flex vs the bouncy upside down epoxy, it all comes down to laminate thickness and foam thickness. If you make 2 identical foam shapes and laminate one using epoxy resin and one with polyester resin (using 2 layers of 6oz cloth on the deck, and one layer on the bottom) you will find the epoxy board a lot stiffer and if you push it to its limit, it will simply snap in half, without much bending before breaking point.

The polyester board will deform, bend, then snap and you'll end up with the two halves attached by a flexible strip of fibreglass on one side.

If you want flexibility in epoxy, you need to use different construction techniques, like (firewire) balsa rails with a very light stringer, or make the board very thin, or only use very light cloth in the laminate (I'm sure there are infinite ways of getting the same result).

The misconception is that all epoxy boards are just the same as the cheap stringerless chinese pop outs.

Sorry Doug, I just checked the compsand web page, and I can tell you get my meaning re chinese epoxy pop outs.

Compsand boards develop their flex due to the balsa (a very well known sandwich core material in the boatbuilding industry too) The epoxy is acting predominately as a skin, and isn't acting as the crucial structural component of the board. The boards would be just as flexible if laminated in polyester, but I understand epoxy is used due to "green" reasons.

In a PU foam cored board, the foam is very brittle, and acts to provide a matrix to support the resin. The stringer is the structural component and plywood (particularly on its edge as in a stringer) is much less flexible than balsa - hence you can't stand on your PU board upside down on a hard surface, or else you break its stringer (and your board will break in half if you keep jumping on it).

Hi Jimi,

Not too surprising you see similarities between Firewire and Sunova. Bert who runs Sunova was the #1 technical and development shaper for Firewire. Shortly after Bert (and trusty sidekick Josh) left Firewire QC went way, way downhill. Here's a tip - don't buy a brand new Firewire until you hear the QC issues have been sorted. They are crap.

The big difference between Sunovas/Compsands and Firewire is that Firewires only use balsa in the rails. They use high density foam in the top and bottom skins and there are ceretain issues with that - it's a mass production strategy that needs to be compensated for in other areas (because HDFs don't recover the same as wood, they suck resin, etc).

Yeah, epoxy popouts have given the real deal a bad rap. People just don't seem to realise that a new consturction paradigm requires a shift in technique.

Plenty of people in the US are building EPS+epoxy boards just using glass and getting good results. They go lighter on the glass and wet it out differently for the lams... And go stringerless. Because epoxy is stronger and forms longer polymer chains you need to use less of it and let the glass matrix take most of the load. The end result looks quite dry compared to PU but a thinned hotcoat/finishcoat takes care of the aesthetics. So 2x6 over and 1x6 under with a stringer using traditional PU quantities of epoxy resin is very much overbuilt for that design. It's not a design I use tho so this is secondhand info and I could have gotten a little of it wrong - a lot of people on Swaylocks have had very good results using epoxy, glass and foam. Digging around in the archives there would answer all your questions on that technique.

Oh and these boards don't use a stringer. The stringth is in the skins... You seem to be understanding some of the technical construction behind custom composites. Actually most of our guys perfer to use EPS and epoxy over PU/PE

Good to hear from you! There's plenty more about these boards on the forums at Swaylocks and you can get better details from the other Compsand guys at our forums if you want... They know far more about the in's and out's of these boards than I do

Cheers!
-doug
Compsand.com!

Cheers for the info Doug,
I've been doing a bit of research re epoxy boards as I'm planing on building one myself. I was thinking about using very high strength foams such as divinycell http://www.diabgroup.com/aao/a_products/a_prods_2.html
and I was thinking about a single layer of very light glass and a layer of kevlar... I'd end up with a very light weight board in the end, that literally would be bulletproof!

it's an ongoing project, that I'll hopefully get around to doing.

Hi Jimi,

You might want to be careful about using divinycell because it agressively absorbs resin, as poor "craftee" discoverred in the divinycell sucks thread on Swaylocks. Some of that can be easily overcome.

A bigger issue I have with the structural use of HDFs is their lack of structural strength. They have virtually no compressive strength (mainly recovery issues) and very little tension strength. Wood has both, which is part of why a lot of Compsanders prefer it for performance boards. That said some of the guys (esp. Paul and Mike) have a lot experience in using it in boards.

Plenty more on the Sways forums if you want to pursue the HDF path!

You got your vacuum setup sorted?

-doug

yeh, vacuum is a house-style vacuum, but it should "theoretically" work fine.

It's just a matter of when I'll get the spare time to do it. (I guess it'll wait till I damage my fave board beyond economical repair).

Should.... hehe!

Do yourself a favour and get hold of an old fridge compressor

-doug
Compsand.com!

Doug, I can understand if you'd rather not give away your secrets etc, but I'm curious, do the compsand boards using Balsa have an EPS core or are you using different HD foams as a core material (or solid Balsa but I doubt it)?

LOL! Nah, no secret there.

EPS core in most cases. I'm personally pretty amped to try some of the fused EPS core material that's arriving on the scene...

Bert ran an excellent thread on Swaylocks that covers a huge amount of how these are done called the Vacumn forming & Sandwich construction (sic) thread, in case you are interested. There are also a number of other threads on there coverring good vac, vac switch and hotwire setups at next to nothing.

-doug
Compsand.com!