i have had an interest in surfboards with flex. a EPS board glassed with epoxy does it need a stringer since epoxy is so strong? and if it dosn’t what kind of flex could be loked for limp like a noodle:snap, or comprable to a greenough spoon:snappy? THanks a lot
Most always yes (super short with heavy eps might not but…) You can use heavy eps with a central stringer (very similiar to a traditional board) or go the vacuum bag route with lite eps and parimeter stringers on the rails.
I don’t think you’d need a stringer up to about 6’6", if you’re using 1.5 or 2# density EPS. If you’re using the 1#, you’d need something, either center or at the rails.
You can get creative, though. I’ve heard of guys using 4 oz 4" wide fiberglass cloth as a couple extra layers in the rail wraps. 5 layers total, with your 2 on the deck & one up from the bottom. That would be lighter than wood, would allow you to skip the cutting in & shaping hassles of a stringer, and could go on with the lam steps. Be plenty strong, especially for a shortboard or fish…
hi Riderofwaves !
does it have to be eps foam and epoxy ?
The reason I ask is because [well , here in west oz anyway] , I was able to get a stringerless polyurethane blank [called a 'packing blank '] . It’s what I used for my ‘bonzer bottom’ 6’5" board recently.
Blank suppliers , when they deliver stringered blanks to board supply places , apparently pack these “packing blanks” into the corners / ends of the blanks’ stack , to prevent damage to the stringered blanks . As a result , the packing blanks are sometimes just sold very cheaply [ some places may even throw them out ?]
Just a thought you might like to explore, if you want to find a cheaper, quicker way of experimenting with flex. And , if you want to use epoxy, you can glass these with epoxy without having to ‘spackle’ [or whatever ] the foam !
I hope this is of use …
ben
hey thanks no it’s dosn’t have to be esp. but i was thinking of maye getting carbon fiber tape and running it down the center in order to act as some bracing bo i have stringless feel with the flex but still has strenth
Forget the carbon. It is totally stiff and dampens the ride of the board to feel like a …carbon fiber surfboard.
Lots of windsurf boards use only TWO strands of carbon full length, and it’s noticeable.
Most don’t use any carbon at all, except heel patches for compression resistance, and they last just fine…without anything for stringers.
Stringers can cause a whole new set of headaches, like rising thru the glassjob, holding a twist from a load, and adding weight.
Remember, don’t matter how strong the stringer is, it’s the FOAM around it that fractures, delams, falls apart, and you know foam is not strong.
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i was thinking of maye getting carbon fiber tape and running it down the center in order to act as some bracing bo i have stringless feel with the flex but still has strenth
You could also use regular fiberglass tape down the center on the top and bottom if you don’t want it too stiff. Some other things to try are deck channels around the perimeter or down the middle, putting one layer of glass on the bias (45 degrees), and shaping the board with a concave deck. You could try some of these selectively, just where breakage might occur, and not where you want flex.
I’ve done stringerless boards up to 8’ without a problem with 6+6 deck, 6 bottom.
We’re trying 1mm woven bamboo sheet epoxied in between two sheets of 1lb ESP.
Right now I’m trying to finish a 6’3" stringerless modern fish with triple bamboo stringers and 1/8" balsa bottom and top but no balsa rails. Probably double 6oz on top of all that on both sides.
We’re thinking of migrating to using glass-bamboo-glass on the bottom and glass-balsa-glass on the top or vice versa.
On a 7’4" Stubb Vector we’re using a full template bamboo stringer (cut 1-2 inches from the rail)versus just 4"-6" wide stringer strips then using bamboo and balsa lams on the outside. The bamboo doesn’t wrap well so on the deck it would have to be cut as a deck patch with balsa around the perimeter for the rail wrap.
Still need to see how this all works out. but it’ll be all epoxy glassed.
The glue up is of 1" and 2" EPS sheets with the 1" on the bottom so on the bigger board it’ll be like a surfboard napoleon sandwich made of 6ozglass+wood+6ozglass+foam(2")+wood+foam(1")+6ozglass+wood+6ozglass. Should be pretty strong but we’ll see. With just the horizontal bamboo stringer the foam is still flimsy but holds it’s rocker well. I agree with Benny though there’s a need for the balsa or divinycel rails to tighten things down the shell. 1lb or sub 1lb is way too flimsy with out some type of shell and shell lock (rails).
We like this sandwich strategy as you shape the bottom on the 1" while it’s still a flat sheet before you glue it up under vacuum to make your rockered blank. Oh yea the rocker is created by vacuuming the 2"-1" sandwich while attached to the bottom of another surfboard. No hot wiring or rocker table required just another board to attach the foam to with stretch wrap and tape… You could even lam on the bottom glass wood layer while creating your rockered blank. Then finsh the top and lam on the top layer. Should save alot of time going from a flat sheet of EPS to a finished board.
Another interesting is to create two separate wood/glass/foam/glass/wood sandwiched shells for the top and bottom using 1" EPS sheets. then building a subframe out of 1/4" balsa like than shown on the HydroEpic carbon board design and vacuuming the top and bottom shells to the wood frame like you would if you were making a guitar or violin. You could use solid wood balsa rails like the sides of a guitar to secure the top and bottom and use the internal rib bracing pattern to tune the flex…
I’d love to see some give this a go… Probably take a luthier. Just a dream I guess…
But I think Paul Jensen’s pretty much doing this except his shells aren’t pre-formed and pre-rockered. He uses his ribs to accomplish this.
I bet this is exactly what Hydroepic is doing except they’re using heated pressure molds to build the carbon kevlar shells…
thanks for all the advice every one it will be a long time before i get to shape no job little money, so maybe this summer i will bring this back up.