HEy. Intending on putting a carbon strip up the stringer of my step up SB that I’m to glass shortly. What’s the best plan of attack to lay it as 0 experience? Spray contact adhesive, stick on and glass as usual? Cheers
A little something to consider. The carbon has thickness. When you add that extra layer, it will bump up the final laminate. So what’s the solution? Extra thick hot coat and sand it smooth? Not really, since you are adding extra weight in hot coat. What you want to do is shape in a slight channel for the carbon to lay into.
Next question, are you using woven tape? if so you won’t have to worry about the edges fraying. If you are using cloth, cut to width, then you need to prep it out differently to keep a good edge.
Epoxy or resin? It will change the technique.
And lastly, why are you doing it? Does the board already have a stringer? Are you just adding a cosmetic racing stripe?
Why flat on the bottom? It looks cool and all, but does a fraction of the stiffening that it would do if wrapped on the rails.
But the simplest answer is laminate with fiberglass as usual. Then pour some resin/epoxy in the channel you shaped for the thickness of the additional carbon strip, lay the carbon into the wet resin/ epoxy and force it up through. Then cap the carbon with another layer of cloth. This top cap can be 2 oz. Then Carbon shouldn’t contact the foam, because the shear/ elasticity is too different. The carbon also shouldn’t be the outer layer. This has more to do with sanding and cosmetic issues.
That all sounds far to complex for me. I’m going to be surfing super shallow coral slabs with it so thought it would help with compression and snappage. I dunno about your presumption of the racing stripe for asthetics : {.
Really don’t want to carve out a channel and fook up my finishing. Already glassing it heavy, so just flag it me thinks. It’s the unidirectional stuff. You really rekon it would be that noticibly proud under a 6oz glass?
Yes, it will be noticeable.
Shaping a slot for it is no harder than a couple of passes with your block plane along the stringer, then a couple of passes with some sand paper wrapped around a block. It’s just a 1/16" max.
You can always just put a really thick hot coat on it and blend it in, but that seems sloppy to me.
If your goal is to increase overall longitudinal flexural stiffness of your board, according to mechanical ingeneering law, carbon above stringer is effective than on rails. Increase flexural stiffness reduce overall buckling of boards but snappage is initiate by localized buckling wich depend much from local skin destabilization than overall flex. So if increase skin stiffness on stringer, where normal forces as the greater because of quadratic moment, is effective for overall stiffness (board response), increase skin stability is more important for buckling resistence. Main way to go is to increase skin stiffness with some sort of sandwich skin or at least with some sorts of “shear keys” (deck channels, power rods, etc…).
Sorry for frenglish
Lemat.
Please isolate the concept of stiffness as it differs from localized skin buckling leading to catastrophic failure.
How can a flat layer of carbon be stiffer than a curved half cylinder of the same weight of carbon?
If your hypothesis were true, corrugated cardboard wouldn’t be stronger than flat stock, fishing poles would be flat, and beam height wouldn’t matter when calculating load and deflection.
If skin buckling only under the narrow strip of carbon is most important, then you may be on to something.but if the Board is 20" wide, a 4" strip down the middle won’t help much.
In I beam design, web height is more important than steel guage of the flange.
With Carbon Rails, you get two webs, as compared to a slightly stiffer strip down the center of the deck (flange) So with carbon rails, you will stiffen the board to the amound that skin buckling won’t happen.
To the OP: You can just put it between layers on your deckside lam, you’ll get a slight bump but nothing you can’t live with. You’re going to wax that side of the board anyway. It’ll stiffen the board a lot, but that will only affect your “break strength” by the extent that reduced bending reduces buckling loads.
You give the answer. If you have a sandwich effect you can’t take each flat surface independant so you have and O beam effect same as I beam. Vertical part of O plays exact same role as vertical part of I (web), only separate flange that take all load. I can demonstarte it litteraly with all formulas with no problem if you want, it’s my job: teaching mechanical ingeener rules !
The purpose of composits sandwich it’s to increase quadratic moment with the stiff material that take load (flange) separate from each other. Corrugate material is a way to increase quadartic momentum, that’s why corrugate panel made from thin panel is stiffer than flat thin panel itself.
That’s way on airplane wing stiffener, much material on flange, just a bit of material, in general Xpattern for web.
It’s a basic of structural mechanics.
Many carbon rails boards start to buckle in top in strong shorebreak here, nobody want’s them anymore.
heeeeeeeeeeeeeeeeeeeee’’ fun times
merry christmas mike
cheers huie
huie, Merry Christmas to you too.
We gotta stop commenting on these structural threads or we’ll see our comments “borrowed” on some major shaper’s blog.
In all the boards ive ever worked on, Big name small name, 90s, 2000s, ive never seen a channel put in for a strip of carbon tape.
Lay it out glass it in and go on. you cant even really feel the bump on the thin stuff. the 6 oz stuff you can and need to use a bit of extra caution and maybe baste the edges before the hotcoat.
foam-carbon-glass.
I guess I can take credit for being the first on that one. = )
Hi Mike,
Since the Coils are putting more of their their reinforcement on the rails rather than the flats, are you finding any problem with them snapping like Lemat says?
Definitely overthinking it a bit but heres my version…
Brush a little resin on the line over stringer and place the carbon over it , as it starts to set mix up the rest of your resin and lam bottom as usual over it.
The difference in thickness is not too much of a prob , you can brush a little extra resin over the edge when you apply it to the deck lamination edge (then sand flat) before hotcoating the whole bottom.
If its got a stringer then your adding a little strength for buckling ( from bottom up as it may only have one 4oz) , if it is stringerless its not going to add enough strength and a Carbon rail would be a better way to go.
Rail reinforcement is good for many purpose but not the most effective for overall longitudinal stiffness and snappage reduction.
Usual Carbon strips are not the most effective material for rail reinforcement. I doubt rail of coils are carbon.
Ud rails carbon on stringerless with light standard lam like ff is finally not better (not to say worst) for durability than “old tech”.
Engineering is a complex world. Not needed to make a surfboards. I spend many years in university to learn it. Then many years in industrial studdies for designing all kind of products from industrial tools to airplane parts. Finally I like it and thinking of it for surfboard is a hobby for me.
Great thread…
If you don’t want to take the great advice already given here and would like to make your board virtually unbreakable you could do what I did for this special project haha…
Isn’t it a bit risky to stop the carbon short of the front fins? I see buckles/breaks right in front of the front fins from time to time, I would think that stiffening up the forward area would leave you with a bit of a hinge effect between the carbon and the front fins, exaggerating the problem of breaks and buckles in this area.
You shouldn’t assume that we’re putting more on the rails. Don’t assume that we’re trying to build indestructible surfboards either, that’s not our goal.
Like I said, I need to stay off these structural threads lol.
That looks insane! What was the purpose of this cool experiment? More info please?
It was for his Paddle-In Hydrofoil surfboard …