very nice huie.
i have only done glue and peel test for epp. would like to try some presure sensitive glues. ive completely discarded urethanes( gorilla type glues) as useful adhesives in dynamic composites. . carbons ok on rails if the rest of the build isnt overboard but i wouldnt use it for 1 pound foam
gday red im glad the numbers are working out . im not varying to far away from these at all. changes to volume distribution is what im in to. i want a three inch thick board that flexes like a 2 inch thick board
The situation according to Stretch.
http://www.youtube.com/watch?feature=player_embedded&v=kzrltEHd0LQ
Makes the most sense so far.
To answer the OP’s question… I’d say yes , that’s the way I’d apply both Core-Cell and Bamboo.
VH.
No huie, I am not implying wood fibers have no tensile strength. Of course it does, and is a function of thickness… veneers are thin, credit card thickness about, therefore compared to fiberglass cloth, bamboo veneer has less tensile strength. Sorry for any confusion my friend.
~Brian
yeah stretch harmonic vibrationsssssss
tried cork and carbon. i think its not combination myself. . carbon over eps doesnt work as well as a higher density rail material
i like the cork tho. you can buy it as underlay
Tensile strength Bamboo = 14,811 psi
Tensile strength Fiberglass = 140,000 psi.
Tensile strength of fiberglass is ten times stronger than bamboo, and three times stronger than steel.
Not sure why we are interested in tensile strength in surfboard construction. Shear and compression would be more relevant, since surfboards rarely pull appart.
Hi Jeff,
In this picture, see how the glass is still intact? but the wood skin tore? Fiberglass being ten times stronger than the wood below. Also see how the fiberglass separated from the wood? My guess is the bonding failure between the wood and fiberglass was where the damage started.
Hey Mark,
One thing I should point out to you in that pic is how tenaciously the glass held onto the paulownia “stringer” (not a true stringer but a flat ‘springer’ to aesthetically mimic a stringer). You can see the glass ripped where the stringer was and bits of it are still on the board. Whereas the glass peeled off the balsa cleanly. From this failure I’ve deduced that paulownia would be a far superior wood for skins than balsa, if only I could find it milled to thickness in full panel lengths.
I’m not taken in by Stretch’s description of what’s happening with the bamboo in regards to tension. It is fairly hard to shear bamboo from tensile flexing though.
We sure as hell know that the cork has next to zero tensile strength , so i don’t see it being widely used on the bottom anytime soon.
What does happen with a construction like Stretch’s, is the bamboo acts as a springer plate similar to a diving board, and as long as it’s relatively flat it serves that purpose and doesn’t become overly stiff.
The cork acts as a compression dampener and does not affect flex as much as a stiffer material like bamboo would if used on the more complexed curved surface of the deck.
It’s more a matter of hard and soft materials used where they seem to do the most good.
I agree with Paul. The rails are very important and will most likely be the focus of development in the future… Imho.
Glass fiber imbedded, flexible urethane rubber or urethane plastic rails are somthing I’ve pondered for years. Looks like the new Lib Tech boards feature just that.
http://www.smooth-on.com/Urethane-Plastic-a/c5/index.html
It’s just a matter of finding the most suitable material and hardness.
But that’s a different topic.
VH.
@ llilibel03
Did you seal the balsa skins prior to glassing with a cheater coat of either diluted resin or undiluted resin, then lightly scratch sand the resin coated wood sutface.
This step nearly eliminates the glass peeling off in big pieces as shown in your photo’s.
The wood builder guys might want to chime in as to why this pre sealing of the wood increases the bond strength.
I don’t know the “why”, just that it works better than unsealed wood.
The paulownia wood may not require as much pre treatement.
VH.
howdy jeff
like es says, boards are not pulled apart, so the bottom is very likely not proof of tensile strength failure, but more a board that is TORN apart. Ripping apart.
cheers
wouter
I agree with ES. here.
Also notice how the balsa grain pattern is perfectly preserved in the delaminated glass section from the nose. Like a fingerprint, it shows that the epoxy pulled out of the wood skins grain completely.
Was this a case of the board’s nose hitting the sand or coral bottom and the wave pounding it into the bottom? If so , sometimes you get lucky, sometimes you don’t
The power of crashing water far exceeds our construction methods. Always will… Really nice looking board btw, too bad…
VH.
Hey VH,
So you think if we did the first lamination against the foam with colored urethane (more flexible than epoxy) and then did the next lamination clear with a harder epoxy, we would end up with a board that has even more of a controled flex pattern, along with a far less tendency to delaminate? And it would look just like a painted blank, clear board, because the laminations would be done in two stages.
This is really getting good.
In demos I've seen with thinned epoxy, the epoxy will penetrate quite a ways in to the wood and really enhance the adhesion properties. Bert Burger has posted here about using either solvents or an expensive autoclave to achieve this result. Although on Jeff's board the glass peeled away cleanly, often a bit of balsa remains stuck to the glass. It would seem that the deeper the resin penetration in to the wood, the better the bond will be.
Bert has referred to solvents being the cheapest way towards resin impregnation... look it up. Just kidding. Here it is.... page 4 (and elsewhere if you have the time):
yes john some of berts more simple soloutions work better than chasing your tail around?
as i have said before infused skins good core combination is key essential in a board 6lb or under
the board in picture is wrongly built in every way.
sorry but thats how i see it
and for those of you bagging on cork learn to use it correctly and then comment or s t f u
** cheers huie
**