Another try…
EPS hotwired blank, stringerless, Vacuum laminated with Cordura Nylon in this order
Deck:
EPS core, 1.2 oz. Cerex N-Fusion, Twaron roving, with micro balloon slurry filler, 4 oz white Cordura patch, 5 oz Red Cordura.
Bottom:
EPS core, 1.2 oz Cerex N-Fusion Twaron roving with micro balloon slurry filler, 4 oz. white Cordura Custom molded fins Carbon and Fiberglass with Micro balloon core.
Rails:
Layered unidirectional carbon fiber. Between one and three layers.
A little follow up on the latest build. Deck wells are forming on the board without corecell patch. I’ll be going back to doing that on future builds.
Yesterday afternoon surf. A guy dropped in on me. As I was passing him, we banged rails pretty hard. I heard a really loud crack. I finished the wave and checked for damage, and there was none. I guess the crack came from his board.
very good. good feed back on the build too. thx
wat about 3d glass looks super strong
Paul 3dglass i see was heavy. It’s look like a thick, rather stiff fabric, with a roving layer top and bottom join with wires that cross interior wich look like more a kind of flexible foam. I think that final weight is more in range of sandwich make with fibrous bubblized bulker (coremat, matline, sphere core, etc…). It’s possible to make really tough composit with those material.
I agree with Lemat that the 3d cloth adds more weight than necessary for the same strength as other designs.
And something important to consider when designing the build. There are different strengths to each design. Lemat writes about resistance to buckling and snapping boards. His local waves are powerful beach breaks where breaking the board is the greatest danger. His designs reflect that.
Where I surf, Southern California rocky point breaks, snapping a board is less common. I’ve only snapped three boards in forty years surfing. But destroying them by hitting rocks is pretty common. I’ve done that lots of times.
For my choice of fabrics, I first choose those that handle sharp point loads that come from impact with hard objects. high compression strength from fiberglass doesn’t help me much when fiberglass shatters so easily.
Just another thing to think about.
Everysurfer, try kevlar instead cordura. Polyamide aromatique (kevlar) have better résilience than “old school” polyamide (nylon), with same bad aspect, plus you can find it made for composit. I do some work with Guys that build high tech composits parts ( job) and their river kayack (hobby). They try everything from diolen to dynema, vectran, innegra, etc…but they say that nothing is better than kevlar with good resin for impacted composits, and those guys have a real composit background in really high tech products.
Cordura Nylon 6,6 compared with Kevlar
Kevlar is ugly, poo brown, so you have to paint it.
Kevlar breaks down rapidly in sunlight, so you have to paint it.
You can’t cut Kevlar with a razor blade to do a cut lap. Well, I guess its possible with lots of razors and Band-Aids. Cordura cuts as easy as fiberglass and much cleaner. Then clean the cut with a block plane, no sanding.
Cordura retails for $10 a yard for a 60" wide roll. That’s $5 a yard for surfboard widths. Kevlar is double the cost.
Lemat, in many of your posts, you refer to Cordura as nylon, or in your post above as “plain old nylon”. Do you know that Cordura isn’t “plain old nylon”, but nylon 6,6 with very different properties than " plain old nylon".
Again everysurfer, nylon is Dupont trademark for polyamide 6-6, it´s know on public domain, so everyone can use it. Polyamide 6-6 is most commun quality for polyamide, it´s known in other names dépend country. Kevlar was founded by Dupont chemist who want to improve nylon. Nylon is not uv stable, coated can help. Kevlar need to be protected against uv like most plastic fiber. Kevlar as dynema or vectran are difficult to cut because of high tenacity. This tenacity wich give pénétration resistance. Nylon and pet fiber have resistance because of their élongation to break wich is fine for cloth but not for composit because need high élongation to break resin wich are soft, so ended with a stretchy membrane. But they can be succesfully use as thin bulker with stiff fiber, thickening laminate and spread load.
Lemat,
Let’s keep this easy. Kevlar has been used by many, and the feedback is almost always that it is too expensive, too ugly, and too hard to work with.
Same reviews for innegra, spectra and others.
I’m posting up boards and materials that are easy to use, give excellent results, and are low cost. I’d also add that they look really good. My laminations are designed to ride really well and not ding.
Lemat, your posts have me wondering something Aramids stretch 2 to 3 % before breaking, so they don’t need an elastic epoxy. nylons will stretch 20% before they break, so you say they need an elastic epoxy. But when is the fabric, nylon or epoxy ever going to stretch more than 1 %?. So if those loads are never put on the cloth, why does it matter? At some point, reality overcomes theory. And if I am blending my nylon cloth with a warp of Twaron (an aramid) then why does it matter if I use an elastic epoxy?
Thanks
So why use a fiber that can stretch 20% if it never stretch ?
Nylon, even high quality trademarked one like cordura, have low stiffness and low elastic strengh, but high élongation to break and abrasion resistance, that´s why it´s use as technical cloth.
Every time a composit skin crack is because it´s stretch further than is elastic stretch capacity. When resin choice is bad, less stretchy than fiber, that´s resin who break and delam from fiber, composit loose is shape stiffness but part can stay in one piece. For sécurity is a way to design composit parts.
you are right plastic fiber design for composit are costly and hard to work with. So they are only use for hightech composits. Surfboards are low tech composit often made in lowtech way but they work so why going to problem. Their is many way to improve durability. You find a way you are happy it´s good but be carrefull with tech washing even if it´s often use in surfboard´s industry, for build tech and shape too.
Lemat I have a question.
Your thoughs on an aramid-cordura type intertwined hybrid thread interwoven into fiberglass cloth? Would this be low tech enough to still work as a skin on a surfboard?
https://www.youtube.com/watch?v=_RxxQauuhz4
someone hitting 3d glass over 1 pound eps with a steel mallet
kevlar with glass in same cloth work good, often use for boat building, same élongation to break. Kevlar is stiffer so take tensil strengh where it is best, glass help resin to to stay them together increasing compression strengh.
nylon with glass is a no go for strengh because nylon is far stretchy and far less stiffer than glass so glass and resin will take all loads and break then nylon will keep skin in one piece, plus nylon bad adhésion with resin will reduce compression strengh. If you want to use stretchy fiber for strengh need séparate layers.
Sanded,
It depends on the load you are designing for. What Lemat says in theory is correct, but maybe not in real life.
Here is an example of what I’m talking about.
Mixing an elastic cloth with an inelastic resin. Just because the cloth can stretch 20% before breaking, does that mean it ever will? What if the glass fibers are strong enough to carry all the load that will ever be placed on the object , and the elastic cloth is purely cosmetic. Is this a bad design? No.
Or the build that I am doing, with a nylon/ twaron blend.
The twaron warp I added is strong enough to take any load that would stretch the board in flex. So the nylon never stretches past the epoxies ability.
Also, when is a surfboard ever stretched? The skin will take some elastic load during flexing. But the other side of the board will fail by compression load and buckle long before the elastic side shears loose.
The cloth you describe could work perfect depending on its use. And depending on the quantity of stronger fibers and their ability to take the load placed on it.
A fiber stretch because it take load. Sigma= E epsilon, sigma is internal stress, E is stiffness modulus, epsilon is élongation. A low stiffness fiber like nylon not take load if not stretch. If you put fiberglass wich is at least 20x stiffer, il will take near all load and because is élongation to break is around 3% it will break way before nylon see some load. In fact in dynamic stress there are some energy éléments to look at where plastic fiber can play.
sorry but théorie came from reality, it was develop to prédicat what will happened and to improve things. Difficulty is to apply it correctly.