very thin surfboard

General Discussion
1

Hi, I’m planing to build a very thin surfboard for riversurfing. Thickness will be around 1 inch, (around 2,5 cm). I want to use styrofoam / XPS and a 1/8" (3mm) poplar stringer. The board has to be quite durable as it wil hit the concrete walls sometimes and I will jump on the board instead of doing a take-off. What lamination schedule do you recommend? I thougt about 2x6oz on the bottom, 2x6oz on the deck, and some deck patches. Should i do a 6" glass strip running along the stringer on top and bottom also? Forgot to mention: I use epoxy resin.

 

 

2

Florian, I made 2 boards around an inch thick, 

the first one I did several layers of 6 oz glass top and bottom  and in between 2 layers of 10 mm XPS (being more rigid than eps), carbon deck skin and vacced the lot.

it flexed too much, way too much…Bulletproof thru the deck but boards of a certain length need to be a certain thickness to maintain dimensional stability.

 I then added more glass top and bottom and it only made it SUV heavier.

 The second one I added 7 stringers and it weighed a ton and didnt flex but it was stiff like a steel tube.

kiteboards can do it thin and stiff because they are short but for a longer board like a surfboard there’s a limit to thinness and rigidity and weight gain.

 If I had to do it again I would shape the board then cut it into 5 or 6 or 7  longitudinal slices and wrap each slice entirely in glass and bag them all together. That would use the glass wrapping as ‘lightweight’ stringers.

3

I wouldn’t use a poplar stringer if you ding it regularly. Get something more water resistant.

 

XPS is a good choice for river surfing, no need to repair dings immediately.

4

Hi Surffoils, thanks for your answer, it’s so cool that no matter what you ask, somebody has done it and can give some advice. so i have to control flex. I could do some rail channels on the deck to stiffen the board up?

5

@ hans, i guess any wood is sucking water, so i could just lay some extra glass at the nose to protect the stringer. Because i don’t no what else to use for stringer material that is water proof AND shapes well. any suggestions?

6

didn’t made much boards yet, but in my earlyer life, I built some flying models with very thin and very stressed airfoils.

we built the stringer/spars with carbon/balsa/carbon.

if you take an balsa edgewise and cover it with glass or carbon tape you will get stiff and still flexible, lightweight board.

unfortunately I can’t image, what dimension you need for such a stringer on a board.

out of my bead I would expect that a 6 cm stringer with 1 to 1.5 mm glass-tape would be a good start.

7

 

I use poplar ply for my stringers too, but for a river board I can imagine that the nose gets hit very quickly. (I assume you are surfing the eisbach)

 

Maybe use a foam tail an nose-block. This will significantly reduce the chances of exposing the stringer to water.

8

Here is how i stiffened the last board I made:

The grooves were about 5mm deep. Done by hand. I used an old credit card as a backing and depth gauge. Just attached a small section of “would be stringer” to the cc card with 5 min epoxy. Then attached a bit of sandpaper and trimmed it to the width of the wood plank.

This made the grooves just wide and deep enough to glue in the stringers. Although i made a mistake of not accounting for the added thickness of the sandpaper, so in the end the grooves were a bit deeper than the stringers resulting in some mellow channels after lamination.

I glued the stringer in with wood glue…

 

Hope this helps…

9

Don’t do it too thin. I also shape mostly riverboards and under 1 3/4" i feel like loosing speed that I have too compensate with tail area and then I loose agility.
Also I don’t like super thin rails. Don’t know which wave you are building for, but in my opinion there’s no riverwave you get advantages using a 1" thick board instead of 1 3/4" or 2"

10

It’s going to hit concrete walls? Holy shit.

11

I suggest Kevlar/epoxy it may be less expensive than carbon and more available/less expensive. Pretty stiff too depending how you use it.

12

Hi parick, the board would be for the eisbach. I wonder why your thin board was so slow. Probably it flexed too much,  and the increased rocker made the board slow? Any other explanations? Do you think the thin rails made it slow? I would make a completly flat deck to carry some thickness to the rails. More like a skimboard.

13

 The more vertical stringers you put in  ( either wood or glass ) will return better stiffness than just adding slabs of glass to either side.

 Keen to see what you build …

14

A flat deck will flex more than a domed, or concave deck… the same reason skateboards have concave decks.

Pardon my ignorance, but why do you need it so thin?

15

Strength is the cube of surfboard thickness (beam depth). 1^3 = 1,  2^3 = 8,  3^3 = 27…

I think retrothis has presented a potential thin lightweight solution.

I have been wanting to try internal floating stringers, in the main riding/stance section of the deck only – like where the old-school FG deck pads were placed.  Stringers would span the thickness of the board. from deck surface to bottom surface.

I want to try 3 or 4 short, floating balsa stringers in the “stance area.”  In your case maybe “thick,” 1-inch square balsa stringers.  For my 7’6" board, I am thinking the longest floating center stringer(s) at 36"- 48" with a couple of of 24" - 30" stringers on either side.  Stringers placed in a parallel arrangement (6" to 8" apart), each “centered” rlelative to one another, in the “deck-pad/stance” section.

My objective is to maintain a stiff planing area under my feet/weight while keeping flex in the nose and tail.  Combining performance characteristics of both stringerless and stringered boards.  Basically, a shorter stiffer board within a longer board with flex.

BTW carbon cloth (bottom only) rather than FG might help improve tensile strength and reduce flex.  Maybe Uni-axial carbon instead of biaxial plain weave carbon.

You might even consider a solid eliptical piece of balsa (1" thick) inserted into the stance area of the blank/foam leaving a couple inches of foam around it at the rails.  Possibly with thin hardwood stringers in the solid balsa elipse.

Just my $0.02.

This photo is an example of the floating stringer concept (foam core long-skate deck).  But the “floating stringers” pictured would be too long relative to board length for the surfboard concept I want to build.