Cerex makes an excellent epoxy carrier between foam and skin. Use a wet out table.
The nonwoven acts as a sponge, absorbing in the epoxy. When you transfer the saturated non woven to the blank, and apply the skin and then put it under vacuum, a perfectly uniform amount of epoxy is squeezed out from the non woven, and into the foam and skin. Works better than fiberglass, because non woven nylon absorbs and holds the epoxy better than fiberglass. The fiberglass can drain epoxy, leaving dryspots and a poor bond. I have tried both.
Nylon doesn’t chemically bond with epoxy, but neither do fiberglass or carbon.
I have done impact testing with both fiberglass and nylon 6,6 over foam, and nylon 6,6 outperforms fiberglass.
Were your periscopes and crash helmets done with a foam core like a surfboard? Differing elasticities is a key as to why nylon 6,6 is better. Inelastic next to elastic layers fail under shear. Also, just because your products failed only means they failed. It doesn’t mean that it was better or worse than fiberglass.
Also, peel ply only releases when coated with a release agent. I have some nylon 6,6 woven from Cramer Fabrics that was intended to be peel ply, but I had them give me some before it was treated with the release. It does not release at all. I used it in the Modern Laminates thread on impact tests, and it worked great.
We were talking before about the non-woven bonding better than woven and I was thinking the nylon might not lock up the core-side of the wood as much as fiberglass. So we add some thickness to the composite. The plastic layer is laid between the core and the wood so we maintain that progression of flexier to stiffer. And we can still back the impact area of the veneer with some fiberglass - or maybe even another layer of the Cerez to build up the thickness of the composite.
Someone (I think it was Lemat) mentioned that polyester bonds better than nylon and might be a better plastic for that. I could also see using Cerex to get the gorilla grip with cork. Cork over a quality PU core - that would be another version of the dual density blank.
[img_assist|nid=1075230|title=polynet carpet binder|desc=|link=none|align=left|width=640|height=480]I like the 1.5 oz EPS over the less dense stuff because you can shape it better or better yet PU for real shaping–crisp foam.I have been looking at these poly net carpet binding rolls at work for years. I thinking they would look nice on rails-- rainbow colors and different sizes too. Use it over the cork as a big pin stripe on the rails.
Yes polyester mat should have a better adhesion to resin than nylon mat, but all in all it’s a poor adhesion compare to well treated fiberglass. A good alternative is to use a light fiberglass mat.
Since you don’t use the right resin (with right elongation to break), those “cheap” plastic fiber add nothing to strengh, they only allow to have a “thick” coat of resin, a good thing because resin have many good properties…
Never forget: a fibrous reinforcement only reinforce when it’s stress (tensil) along the fiber, the resin must have an higher elongation to break and a lower young modulus than fiber. For all other stress that’s manly the resin that resists.
Hello Every! Its an interesting area because the fibers dont necessarily act how you expect. Impact resistance is not a function of fiber elasticity. For example kevlar has far better impact resistance and penetration resistance than E-glass yet it's tensile modulus is double that of E-glass. My point was that there was something strange about Dyneema in its bond with the matrix. Dyneema and Kevlar fibers have broadly the same ultimate strength and tensile modulus, yet following impact from penetration tester the Dyneema seems to unbond itself from the resin with a classic white craze. The kevlar doesnt.
The other proof that impact and penetration resistnace is not related to the fibers elasticity is Zylon (PBO). It has far higher tensile modulus than Kevlar and Dyneema (in fact almost that of carbon) yet it's impact resistance is unbelievable! When we used Dyneema in products the impact resistance is great, but then the subsequent mechanical properties are not as good because of the delam I mentioned.
I'm just surprised that Nylon offers such reportadly good impact resistance considering just the bare numbers, although I suspect its not offering any tensile strength or much stiffness. Thanks for the steer, I'll try it out!
What do you suggest on the rail if the goal is to prevent dings? If you just lap the outer layer of glass used on top of the veener which is typically a single layer of 4oz, you end up with two layers of 4oz on the rail which IMHO dings quite easilly on the exposed 1.5-2.0 lbs EPS.
Impact resistance is function of energy dissipation, for impact something that can elongate a lot have grate properties. Try to break flat polyamide sheet with an hammer. Those plastic fibers have great elongation to break so they can dissipate energy but only if resin can elongate too and can stay glue on fiber, an other bad aspect of plastic fiber. A good alternative can be real Sglass with at least 6% to break epoxy resin.
Haavard, i only use wood on top so i have at least 3 full layers of 4oz on rails, first one with elastic foam resin, so it’s reasonably strong. I work only with 2lb foam know. I am not a big fan of wood look, i use it on demand for strong build. For board under 7’ i use on top 1mm thick wood infused with 4oz under (elastic foam resin) and 4oz over + internal Omega stringer “anti buckling” and under 4oz elasticfoam + 4oz warp + 3/4 lengh omega stringer . For longer board is use 6oz warp flat weave for last layer. It seems to be really resistant for standard PU/PE weight.
I can’t agree with what you are saying. A thick coat of resin is as good as without fibers? Take some cured epoxy without fibers and flex it in your fingers. Take the same sample by weight and thickness with fibers, and try it agian. Which one breaks?
Also when you say cheap fibers, which do you mean? Polyester and nylon have poor tensile strength. Nylon 6,6 and twaron have good to excellent tensile strength.
Nylon 6,6 does have pretty good tensil strength, and you are correct about stiffness. On my latest, I used Cordura (nylon 6,6 not regular nylon on the deck and rails. I used a layer of Nylon 6,6 under warp fiberglass on the bottom just for the increased tensile strength.
I would never use just nylon for anything surfboard related.
Nylon is polyamide 6-6, normalize mechanical properties: tensil elastic resistance “Re” is 0.9 to 1 GPa, young modulus “E” is 5 to 6 GPa elongation to break “A” is 16 to 18%. Twaron like kevlar is aramide = polyamide aromatique, High modulus for composits, Re=2.8 to 3 GPa, E=120 to130 GPa, A= 2.5 %. For memory Eglass: Re=2.5 GPa, E=72 GPa, A=4.5% not so bad but specific weight is double.
Apologies if I've got the wrong end of the stick from what you've said. Impact resistance is not just governed by elasticity, or more specifically "elongation to break". If it was, e-glass would be more impact resistant than Kevlar, Zylon and Dyneema (elogation to break: 4.8%, 2.4%, 2.5% and 3.5% respectively). If we assume the right resin is chosen in all cases, Impact resistance is a function of fibre tenacity, elongation to break and the fibres ability to bond with the resin matrix if a durable lay-up is sought rather than just a one hit wonder (not a problem in helmets). Hence I wouldnt use Dyneema in a "long life" product, but its fine in "one-hit" apps.
Something hightly elastic is great at absorbing impact, but that is not the only demand on the material if a light lay-up is needed. Where buckling loads are high in the skin, decent E is needed to avoid Euler and Brazier instability failure modes.
Mat is better at holding a uniform amount of epoxy such as in composite laminations. Woven is better at directional loading. But either way, adding fiber will reinforce the lamination, unless your epoxy has the exact same properties as your fiber. This doesn’t happen unless you have an epoxy that I don’t have access too, or you are using poor strength fiber
It seems you are saying it is fine to make a surfboard with no cloth, just resin or epoxy? We know this in not correct, so please clarify.
Nylon is polyamide 6-6, normalize mechanical properties: tensil elastic resistance "Re" is 0.9 to 1 GPa, young modulus "E" is 5 to 6 GPa elongation to break "A" is 16 to 18%. Twaron like kevlar is aramide = polyamide aromatique, High modulus for composits, Re=2.8 to 3 GPa, E=120 to130 GPa, A= 2.5 %. For memory Eglass: Re=2.5 GPa, E=72 GPa, A=4.5% not so bad but specific weight is double.
What kind of BS gibberish is this crap. Make a surfboard. Which one of you technomath geeks has ever even made a surfboard? What the hell is a T-flex surfboard? it sounds like you guys are designing a space ship?
Didn't the chap ask about ELS density something on the sorst of 1.25lb...whatever that means?
Wheres the blowhard seal licker Resinhead, I bet he's got some babble to add to this BS.
Nylon is polyamide 6-6, normalize mechanical properties: tensil elastic resistance "Re" is 0.9 to 1 GPa, young modulus "E" is 5 to 6 GPa elongation to break "A" is 16 to 18%. Twaron like kevlar is aramide = polyamide aromatique, High modulus for composits, Re=2.8 to 3 GPa, E=120 to130 GPa, A= 2.5 %. For memory Eglass: Re=2.5 GPa, E=72 GPa, A=4.5% not so bad but specific weight is double.
What kind of BS gibberish is this crap. Make a surfboard. Which one of you technomath geeks has ever even made a surfboard? What the hell is a T-flex surfboard? it sounds like you guys are designing a space ship?
Didn't the chap ask about ELS density something on the sorst of 1.25lb...whatever that means?
Wheres the blowhard seal licker Resinhead, I bet he's got some babble to add to this BS.
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This "BS gibberish" is the difference between making 10 boards and one on the road to building the next sweet board. Ever wanted to make something as good as you possibly can? The ramblings of Lemat and Every are the exchanges of two dudes using their know how and technical accumen to come up with the best boards they can. I love it. If it were not for guys like these we wouldnt have even seen a PU/PE, let alone an EPS/Epoxy, T-Flex or Compsand.
Can you explain how you seal the veneer? I’m wondering what difference there is between coating the wood with epoxy as a separate step (sealing) and coating the wood with epoxy when baggging it onto the blank?
You are completly right tenacity is not only elongation, just a general aspect: currently stiff materials are brittle they don’t like impact (carbon for exemple), flexible one are “stronger” against impact even they are not strong (high Re).
Everysurfer:
If you make a composit of fiber and resin with exaclty same mechanical properties you will have exaclty same mechanical comportement than plain resin (or plain fiber). A board with a thick coat of right resin can amaze you !. But you need stiff fiber for weight/stiffness/resistance ratio.
resinbutt
You are right no need this BS to make surfboards, so don’t care of it. I made about 100 surfboards thos last 15 years.
llilibel
First i glue wood on seal coat so resin goes through it. Then i heat the board in my hot box and i spread a water like resin (slow infusion resin) and let it soak by capilarity