I’m slowly approaching the date when my wife and kid will leave for a few weeks, allowing me to mess up the place with my next shaping excercise, and I start looking at my options, so here’s the question:
-I’m thinking of shaping EPS (whatever I find, I don’t think I’ll try hard to get a specific density)
-stringerless
-Carbon fiber shell around foam.
my question is: will the carbon fiber give it enough strenght/rigidity to make for the missing stringer? if so, how much CF should I lay on?
I’ve also noticed that many “stretch” boards have a groove going along the rails, about 2-3 inches in, deck side: is that to increse the rigidity of the board?
I have an old 80’s al merrick that can take a beating, in fact the foam is coming apart, so I’ve retired her. But she has a carbon fiber layer along the stringer … . the foam under there hasn’t powdered (its a clark blank), but everywhere else, it has.
I think with a 2.5 density (or 2+) it will be fine . . . you may find 1 lb too flexy . . . but carbon fiber is stiff . . .
there’s a guy lpcedg I might have the user name wrong . . . there’s a post about a crazy hollow wooden carbon fiber fish , he seems to have experience using carbon fiber layups.
I have a post running about the stretch boards deck rail channels, do a search for that.
I’ve made two boards, Clark/Carbon, and two boards 2#EPS/Carbon.
There are all still working fine 2-3 years later. They are 8-10’ with 2x5oz. top and 1x5oz. bottom. The two EPS boards have carbon perimeter stringers (2x5oz.) vertical 2" in from the rails. I broke the 10’er on an 8’ wave last year and rebuilt it and it rides just as it did before.
The only problem I had was with the darkness (solar absorption) of the carbon and began putting in lots of pigment to lighten the color.
Carbon, I think, is stiff if you use it with a lot of curves, roundedness, etc. If it’s flat you’d have to have 5-10 layers to stiffen it up. The 1-2 layers that I had still allowed the board to flex just nice!
You should be able to see my boards/posts here in the archives. Just search withmy name - tridrles
As I remember from earlier posts on channels, they stiffen up the board, give it more strength (curves/rounded). And Stretch, I think, said that the customers liked them (or was it RR guy, Greg?) because they were good hand holds, Ha!
But to your question… strong enough? If your making a long board put, at least, carbon perimeter stringers in it. If it’s a short board use the channels to strengthen it and no stringer.
Les
PS - The last 5 boards have been balsa composites and I LOVE them! The one I’m working on now is EPS/Balsa/Sglass and at 8’ with out the glass on yet it should finish out to be under 8 lbs! Can’t wait to tri it!
I did some research on stringer vs no stringer… I found that it significantly adds to the strength of EPS foam. EPS has a tendency to squash when pressure is applied. This allows the top deck to collapse inward and fail. check out my link and data.
The main benefit of CF on surfboards is laminate stiffness to weight and its very resin and design dependent. The density of the eps makes a big diff too…just winging it is just that. Might be a very expensive experiment.
I’ve seen a stringerless fish with rail channels on here, but it was a 6’0" or less. would it work in this size? is it just a matter of putting more glass? that’s why I thought about using carbon fiber, to add stiffenss.
what if I just put CF on the rails (A)? or just in the rail channels(B)?
it seems to me that htis couls work as a nice substitute to a stringer, am I wrong?
and in case I’m right, when would I glass the carbon strips? underneath everything? on top of the regular glass? inbetween?
As I said in my earlier post, if you put it (CF) on a curve it will create more stiffness, so… The way you picture it, it would be best to have it, at least covering the rails. That would give you, I think, the equivalent of a stringer but with flex. Now, it’s up to you how stiff or flexable you want your board. In the channels would give the least amount of stiffness, covering the rails would stiffen it up more and on both would give the max stiffness to your board. Make a decision and DO IT! Then let us know!
I would suggest putting the CF under the glass, next to the foam.
what if I just put CF on the rails (A)? or just in the rail channels(B)?
I personally think it is an excellent idea. Many possibilites for sure. You could also put horizontal sandwiched (thin core, like 1/8" to 1/4") panels in the blank in the area and shape that you show. Vary the thickness of the core and shape of the the panel to put the flex where you want it. Carbon has excellent flex characteristics in thin sandwich panels with proper core choice.
You could do either but performance gains could be minimal. I say that cuz at 2 5/8, thats a very thick panel which in and of itself would give you most of the board’s stiffness. There is laminate stiffness and then there’s panel stiffness…two different things…its the distance between the laminates that gives the board rigidity…its how stringers work.
Adding a stiff layer to either the rail channel or rail wrap would give a stringer like affect…problem is doing it cleanly and effectively…carbon fabric doesnt drape well. And you would need a few layers…one wont do much.
The preferred way to cut carbon is with a blade, not scissors. But thats usually done on a firm backing. Dont know how CF cutlaps would come out but it sure would be very easy to sample test before application.
Multiple fiberglass layers wrapped over the rail is an easy and effective way to go. A std surfboard has three layers over the rails…add more and you got a stringer like effect. Stiff epoxy (RR 2000) helps heaps…
HTH
ps - dont get CF chopped fibers anywhere on you, its not exactly safe…wear a dust mask too
