Well it lasted over 2 years, but I got caught out yesterday with the board inside of me a little leash tension and the lip guillotined my step up winter board. Now I'll be stuck paddling hard and even stomach paddling on the small boards in big and bumpy surf until I can figure out a replacement. Tempting to use opportunity to try something a little different. I've seen many broken sups when used in bigger waves, I don't know if I should just accept this risk or consider a stronger construction maybe sandwich like windsurfers? I wonder if smik is made this way.

Yikes! Hope the swim in wasn't too bad. I thought I saw some interesting low volume SUPs on CA Craigslist last time I looked

One little known fact (at least by me) is that resistance to breakage in half is mainly due to the rails.

The board as a whole can be considered a sandwich construction with the foam blank sandwiched between the deck and hull (and those can be themselves sandwiched or not).

If the lip hits the deck, the deck is compressed and the hull stretched. Some resistance can be added by a carbon strip in the middle of the hull but the main issue is keeping the deck and hull together, via the rails. As soon as the hull and deck "slide", the sandwich effect disappears, the blank breaks and then the deck and hull follow.

This to say that you want a board with hyper-reinforced rails, and this is why you see a lot of glass boards with carbon rails (beware of the ones with just a black paint on the rails).
A strong stringer will also help, as providing a strong anti-sliding connection between the deck and hull.
As wrapping cloth around the rails and sanding them without eating into the fiber requires a good glasser, this is why cheap boards can break in half easily, event though the deck and hull appear solid. E.g visible wood deck with suspiciously opaque painted rails.

Sandwich deck and hull will not help much for this however. They are are great for ding resistance however, and this resistance allows for using less material (and a lighter blank) for the same resistance to pressure dents and impacts, saving weight.

But the most important point if to never leave the board perpendicular to the wave in the impact zone. Try to push it to make it parallel to the beach... if possible.

Tl;dr: Strong rails and stringer.

I agree about rails colas and nice explanation but problem remains a straight eps blank is very weak, but adding a pvc glass sandwich vacuum to eps including over rails creates a very strong and still light blank due to the composite effect of different materials kind of like plywood, this then needs less final glass and epoxy (as you know I'm sure). But board builders can make custom much easier and quicker for less money with surfboard construction and no specialized equipment. i checked the glassing and carbon on my broken board and it was glassed very well good saturation and adhesion to blank etc. no complaints there.

Even with crazy jumping by 90kg heavy pros, and being let go of in heavy surf a light windsurf board never snaps in half, although the force is probably narrower.

I believe smik is sandwich I know Jimmy Lewis is for sure.

I believe smik is sandwich I know Jimmy Lewis is for sure.

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KDog said..
I believe smik is sandwich I know Jimmy Lewis is for sure.

Kalama as well

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slsurf said..
board builders can make custom much easier and quicker for less money

No, unless your board builder is not properly billing the time spent.

For instance, stronger and lighter rails are done by applying cloth layers one at a time, pulling the extra resin and curing between each layer. That will always be more expensive than a factory applying all layers at the same time.

I have now mostly custom boards, as I love the construction (vacuum bagged carbon sandwich), but there is no way they can be made cheaper than production boards, the time the glasser/sander spends on them would not be sustainable in production.