…On my current project, I’m using 1/8" lauan plywood for the stringer…On both sides of the stringer I laminated one layer of 6 oz. carbon fiber cloth with epoxy resin…The strength increase is incredible…And thats just after one day of the epoxy curing…after a month it should be double incredible… …Anybody else try this…or why not…??? Paul http://www.hollowsurfboards.com
Paul are you talking about one of your wood boards or a foamie?As for stringers in foam boards I feel that most of the stock woods used by say…Clark…are not that hot.They have no noticable spring back qualities.The boards are gonna flex so why not use a stringer like ash with the proper grain??I’ll tell you why…it costs a little more and is harder to shape.Just a little more effort and you could have a better product.The same thing goes for the clear board thing…but I won’t rant and bore you guys with this one again. R.B. (Paul I enjoy all your emails…I just got my email deal figured out so I can respond)
I’ve tryed it on foam blanks with no good results, in the shaping proces the little fibers broke off leaving some damage to the foam. Regards Peter Rijk.
You can submit your own stringers/wood/plastic to Clark Foam. Or glue up your own, ask for a cut blank. Generally people are too cheap to spend the extra money on quality wood. Shape-ability over performance, They sell what the customers want. Also, I don’t know how you would shape it, but www.gordoncomposites.com makes bomb proof pre-tensioned fiberglass, carbon and s-glass in a variety of ways. Sluggo
I almost don’t even want to open this can of worms here but… I have extensively tested different stringers for many, many years, all different types and with numerous types of glues and glue up techniques and to be honest… and this is where everyone will probably disagree with me… stringers aren’t that effective at what they are supposed to do. They are supposed to add stiffness and strength. Anyone who has ever seen a stringer unstrung can tell you that until we reach about 3/8 of an inch they really don’t have much structure. They are poorly supported by foam and add little in the way of stiffness or break strength. Once reaching 3/8 of an inch they begin to have the kind of structural integrity that can make a difference. Unfortunately they also, at this point, begin become heavy, weighing in at about 3/4 lb. glued in a short board. 3/4 of a pound is about 6 oz. of one side of glass in a finished board. In other words I can have a blank glued with a 3/8th inch stringer and glass it with a 4 oz. bottom and a double 4 oz. deck. Or I can have a stringerless blank glassed with a 6 oz. bottom and a double 6 oz. deck at the same weight. Which is stronger? Which is stiffer? Actually about the same. The difference is that the board glassed with the 6 oz. has 50% better ding strength and even better 50% dent strength. Now as Cleanlines stated above better materials does make for better strength qualities (strength to weight) and as Paul stated carbon can give exceptional results. But I have shaped carbon stringers and I didn’t care for the itch that went with it and couldn’t imagine doing things like that on a daily basis. Likewise with glass stringers. From here I don’t know what more to say accept that stringers do a great job at holding the rocker while the boards being glassed and also give the shaper a center to work off of BUT if your looking for strength from standard stringer material used in surfboards today I believe your fooling yourself by what appears to be a structural advantage.
…One of the reasons I’m using carbon on the stringer on this hollow is to maintain rocker… There is natural tension in the wooden deck and bottom skins…That tension wants to flatten out…The CF stringer will maintain the rocker without distortion…and the strength is there too…I’ll likely CF the interior rails on this one too…The interior deck and bottom skins will be mostly balsa with CF laminated to the interior surface…Light and strong… Paul http://www.hollowsurfboards.com
I would agree with a lot of what Greg has to say. In typical laminate or sandwich construction, the center of a laminate, or in this case core, is considered to be a neutral zone, not dealing with the strength factors that the skins have to deal with. It doesn’t really make since to have a thick peice of wood in the center of a blank where it can only add weight and not strength. Overall you are getting an I-beam effect with stringers and they do help hold the rocker in the board. There might be better ways a creating a strong light I-beam than going with a thick center stringer I know Clark Foam did some testing back in the hayday of windsurfing and did some testing with different stringer arraingements. They had a published write up on the test. If my memory serves me, (3) 1/8" stringers glued up as offsetts were much stronger than a single 3/8" stringer on a sailboard. Heck if your going to add a 3/8 piece of wood to your board no matter the glue up, why not stick a baseball bat in the center of the board as well, unless weight is a factor you are trying to achieve. Sluggo
Another though for the stringer tank: Where do you think 1/8"wedge stringers running 0" at the nose to 6" at the tail fit into the structural integrity picture? They sure make the tails of swallow a hell of a lot more durable and with them running askew I would think that would give a measure of strength that parallel stringers of the same size don’t though I could be wrong. No Worries, Rich