Looking for some experts out there to see what affects 2x4 oz glass on the top and 1x4 oz glass on the bottom vs 2x6 oz glass on the top and 1x6 oz glass on the bottom
If one uses the surfboard carefully 3 x times a week - 4 hours each day - expecting the board to last a while (few years) but concerned about cost and;
Overall weight, strength and flex distribution of the surfboard
There’s always a trade-off.
Get a group of surfers together and you get different answers to describe their perfect surfboard:
Most would say “super lightweight and super strong!”
To get “lightweight and strong!” with present day technology (not using Varial - the cost) this includes the number of layers of fiberglass cloth on both the deck and the bottom of the board, and the weights of each layer of fiberglass cloth.
To get things started:
There are different types of fiberglass cloth - some will provide more strength with 4oz (like S-glass) than standard 4oz cloth - this glass could increase the weight by 20%
Core is important too. With a soft low density EPS core you’ll have to go heavier on the shell than 4+4. Double layers are proven to be stronger than single layer of equal weight… I.E. 4+4>single 8. S-Cloth definitely has superior material qualities than standard E-cloth.
Then there are your resins and lamination methods…
I’ve heard complaints of “too corky” with boards from SurfTech so there may be a point of diminishing returns on the light weight thing. Some guys prefer a bit of heft especially in chop.
Stringers, too. That extra few hundred grams worth its weight in gold for strength.
12oz over rails vs 16. The 16 will be stronger. Strength is in rail. Full or half lap?
If you want to save weight, use a hard (steel?) squeegee or infuse it. Surfboards are far from optimal glass/resin loading - speak to the aircraft guys.
Sub 5lb shortboards are pretty much disposable (for me, anyway).
depend level, surfing style, surfer weight and waves. Most guys i made board with my “exotics” build come because they can keep standard surfboard more than 6 months of real use and often much less. powerfull barrel beachbreak. most don’t want ultralight nowadays so i do standard disposable surfboard weight but far far durable. i use light core, composite springers, and lot of multiaxial glass. because i don’t use through blank stringer and with right fiber pattern choice i keep some flex but stronger board against buckling/snaping have to be on the stiffer side.
Increasing strength most often results in a stiffer board (for the same shape).
Heavy lip impacts destroy any board.
For me key to increasing strength is increasing the buckling resistance of the deck, which can be achieved by:
Adding stringers or fake stringers that are routed <1cm deep in the foam, these increase the buckling resistance by an increased bonding to the core.
Adding a sandwich layer (veneer or hd foam), considerably increasing buckling resistance through increased skin thickness
The most obvious candidate for saving weight is vacuum lamination, as it will get you closer to optimal resin/fibre ratio. It has one side effect in that is decreases the skin thickness and therefore slightly decreasing it’s buckling resistance.
The main issue with those techniques is that they all considerably impact the board’s stiffness and therefore the shape needs to be adapted, compared to the classic lamination which has been dailed in throughout the years.
Way too many variables. Are we talking resistance to snapping, resistance to crushing, resistance to dings? How important is weight? The density of the foam, the shape, the resin used and how much of it and the quality and type of cloth being used all play a roll as does the competancy of the guys glassing and sanding the board.
for two decades plus all my rides, including HPLB’s, have been glassed S cloth 4, 4/4…no snaps, no breaks or cracks, and they take a pounding up here in well OH Oregon beachbreak.
all started with this 8’0 Schroedal shaped for Fiji in 94’, glassed by Vince Broglio, became my go to at size on the road and in winter SF OB for many years…aside from a few dents this ‘now a wall hanger’ remains dry,light and crack free…it’s durability after my first trip to Fiji, including being caught inside at real size, sold me on 4/4,4 from then on…
Resin strength- The resin used is a big factor. Ortho, Iso(what I use), Vinylester, etc. If you need your board to be bright white then ortho is the only clear one mentioned. Vinylester is even stronger than Iso but has even more color to it. Iso and VE can be difficult to work with until you find the right product and get your system down. I only use polyester resin so that’s all I’m addressing here, epoxy experts are more qualified to talk about those.
2. The order that different weights of glass are stacked- I believe that having larger weave against the foam is less likely to delam and tighter weave on the outside is less likely to get surface cracks. An example would be on a 6+4 glass job having the 6oz on the bottom and 4oz on the top. I know this flies in the face of convention.
Match top and bottom glass schedule- The standard is to glass the deck heavier than the bottom since the deck gets all the abuse from body contact. Unfortunately when the flex and strength don’t match on the top and bottom it’s more likely to result in a broken board. I’ve set up my current glassing schedules with this in mind.
Choice of weave- E, S-cloth, flat weave, etc. A big subject when considering weight/strength ratio.
Avoid unreinforced resin- Excessive hotcoats and gloss coats that aren’t sanded tight will increase the chances of surface cracks. Note that cracks starting on the surface will always find there way through the weave and to the foam, often broken boards start that way.
Sealing- Sealing the blank makes for a better bond to the foam by reducing the chance of a plural space developing between the foam and glass as the resin soaks into the foam during the drying process, especially when tight weave (ie: 4oz or flat weave) is used next to the foam. With proper application sealing shouldn’t add weight and net resin use should remain the same since sealed blanks require less resin to lam. Note that squeegee technique and faster cure times are are always big factors to achieve a good bond, especially if the blank isn’t sealed.
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Several of these items I’ve never heard discussed but seem obvious to me after experimenting and observing. The extra steps are outside of the industry standard and not practical in production glassing. Just things to think about if your looking to make a stronger board at any given weight.
All very good info, especially lemat, Hans and Gene. I primarily glass using production layups and methods. When I take a blank to a glasser unless specified I will be getting a 6/4/6 or a 6/6 deck and 6 bottom. Most of the time 6/4/6. Some glassers mix Warp and E. Occasionally Volan is thrown in. I rarely use or spec S. When I glass my own I often use Vector Net. V-Net on the deck and often deck and bottom. When I use V-Net, everything under and over it is 4oz. One of the more active Shaper/Glassers I sell materials to builds both Poly and EPS boards. Between he and myself we have came up with his norm. Ply stringers or two 1/8" Bass (sometimes 3) glued at center. Silmar 249 OB or Resin Research Epoxy. Warp with an occasional 4oz S deck. Sometimes Carbon Tape strategically located. We recently dropped Hexcel and went to BGF. He uses Marko EPS and Millennium “Red” density. His crew ride the same waves of consequence here in the NW that lcc referred to. Since we have worked out that Build Schedule, problems are few. Good resistance to deck dents and snaps. When I glass them myself, I buck the norm and do as Gene reccomends; six oz. against the foam 4 oz on top. When someone comes to me and specs what they want on a layup, I got no problem doing it in the combination they want provided it’s not bizarro.
"3. Match top and bottom glass schedule- The standard is to glass the deck heavier than the bottom since the deck gets all the abuse from body contact. Unfortunately when the flex and strength don’t match on the top and bottom it’s more likely to result in a broken board. I’ve set up my current glassing schedules with this in mind. "
Thanks Gene for writing down something that I always thought of as very important; I glass all my guns this way (double to triple 6 top AND bottom).
…I can add a few more regarding the outside of industry std thing:
Techniques:
-Over shaping. This is one of the main causes to killing a board.
-Bad resin/fibers ratio. Too much resin. I see plenty; then you would see those stress marks in front of the fins and between front and rear fins.
-Over sanding. Killing the glass work.
Materials:
-Wrong plug; too low density and overshaping (like the machine with the small boards)
-Using a combo of PU/wood stringers makes a difference in some design; where you obtain a good compromise between flex and rigid.
-Volan cloth an error. Premium fiberglass do not have chromium baths.
-If you use hot coat resin instead of gloss resin for the gloss coat you would obtain a more flexible finish that do not have stress marks (like with the longboards)
-Putting the layers at a certain angle is better than all the fibers parallels.
-Cutting the deck first layer to the bottom (something that most do not do) provides gobs more strength to the swing of the board and more resistent bottom rail.
-Put 5 more layers on the tail edges and nose edges and you will never have more dings there (those are the main repairs)
Regarding lamination equal both sides is not the way to go in all the designs except some guns. You are killing the “livelyness” of the intended design. Is like when you repair a broken in a half board. Except when you go stringer less.
Finally; ONLY good surfers and heavy conditions and beginners or bad surfers brake boards in halves.
With two layers; Pulling one layer straight and one layer at an angle may be stronger or it at least seems that it would be logically; but as I have stated before almost always results in some kind of “twist” eventually in the finished board. I prefer to pull it straight off the roll, but mix E and Warp on my decks. S substituted for the layer of Warp is more dent resistant, but does little for snaps. Most snaps result from downward pressure on the deck. At least that is what I have seen the most of over the years.
board break because of buckling of skin that take lenghtwise compression stress. everything that increase flexural stiffness of skin increase buckling stability.
Lemat, you got almost all of it there and I salute you for it.
Basic Strength of Materials classes (I are engineer) will very soon inform the student that THICKNESS (other things equal) is strength.
That said, when we’re talking of composite beams (foam core with glass skin) there are two more things in play to reduce buckling: the bond between the glass and core, and the ultimate strength of the skin. I used to think that snapped boards were caused by the skin separating from the substrate (classic buckling), and this is shown by (some) otherwise cleanly broken boards showing one layer separated from the core at the break location. But boards can also snap by simply failing in tension.
But no one likes thick boards, despite the second-order positive strength of thicker boards. To me, anything under 3 inches is likely to snap, but of course this depends on the waves encountered.
If there are two layers, the strands should run at 45 degrees to the stringer. That uses more linear yards of glass although the actual amount of glass is the same, the rest is wasted.
thickness is choice for surfing ability and not for strength. Thin skins buckle because they have low flexural stiffness and foam (+ foam bond) can’t keep them stable. with epoxy on eps problem is not bond but foam cohesion. At the end everything break, but i like to try make this happen later LOL.
