Poly on poly vs epoxy on poly

[Kulharin]

Hello, is it beneficial to glass a poly foam board with epoxy resin vs poly resin on poly foam? Will it help much with weight and durability... and is it worth the additional cost?

[Cranked]

Epoxy is much better.

Epoxy resins have performance advantages over polyester and vinyl esters in five major areas:
■ Better adhesive properties (the ability to bond to the
reinforcement or core)
■ Superior mechanical properties (particularly strength and
stiffness)
■ Improved resistance to fatigue and micro cracking
■ Reduced degradation from water ingress (diminution of
properties due to water penetration)
■ Increased resistance to osmosis (surface degradation due to
water permeability)

In detail:

https://www.google.co.id/url?sa=t&sourc ... M5jMZ1dqqA

[steve shearer]

To be honest, any difference to me has been purely theoretical.

I can't discern any difference in performance and/or durability.

They still dinged, heel dinted, creased, snapped etc etc. Not to mention epoxy tends to yellow in the sun more than PE resins.


I think the glassing schedule and skill of the glasser/sander makes far more difference.

[tootr]

Anyone know much about the HYFI tech that JS are now using?
They claim its 30% stronger or so. Fondled one in the shop and the weight (or lack of it) is something else.

[offshore1]

Epoxy is much better.

Epoxy resins have performance advantages over polyester and vinyl esters in five major areas:
■ Better adhesive properties (the ability to bond to the
reinforcement or core)
■ Superior mechanical properties (particularly strength and
stiffness)
■ Improved resistance to fatigue and micro cracking
■ Reduced degradation from water ingress (diminution of
properties due to water penetration)
■ Increased resistance to osmosis (surface degradation due to
water permeability)

In detail:

https://www.google.co.id/url?sa=t&sourc ... M5jMZ1dqqA

Plus one.
I've done more than my share of boat repair.
All good boatwrights know that cranky speaks three chords and the truth.

[steve shearer]

Anyone know much about the HYFI tech that JS are now using?
They claim its 30% stronger or so. Fondled one in the shop and the weight (or lack of it) is something else.

I've heard the deck caves like melting butter after a few months. Time will tell.
But yeah, be great for low energy summer surf.

[offshore1]

One point of difference between cranked and my experience: epoxy is far more flexible, not stiffer. Polyester is downright brittle.

[steve shearer]

That was my understanding of epoxy, that it was more flexible. Therefore less prone to micro-cracking/shattering.

[alakaboo]

To be honest, any difference to me has been purely theoretical.

I can't discern any difference in performance and/or durability.

They still dinged, heel dinted, creased, snapped etc etc. Not to mention epoxy tends to yellow in the sun more than PE resins.


I think the glassing schedule and skill of the glasser/sander makes far more difference.

Your last line is key. If yours are yellowing it suggests they didn't add stabiliser. Epoxy and vacuum is the winner.

[Cranked]

Interestingly:

"A post-cured epoxy laminate will exhibit tensile strength and
modulus (stiffness) close to double that of a non-post cured
polyester or vinyl ester laminate"

Post curing (176 degrees for 8 hours or something) gives about 30% increase for epoxy AND poly

Do any board manufactures post cure? I know Byrnes in Woolongong used to.

[black duck]

Interestingly:
Post curing (176 degrees for 8 hours or something) gives about 30% increase for epoxy AND poly

Baking a surfboard for that long at that temp is burning a fair amount of energy.