build thread


I did the math for you

120/1,000  * lb/(ft^2 * in) * 12 in/ft = 1.44 lb/ft^3
130/1,000  * lb/(ft^2 * in) * 12 in/ft = 1.56 lb/ft^3

so it is +/- #1.5 foam


which is not very dense. I use #2.5 xps in my boards (see indian thread). (40kg/m^3 outside the US)

thanks Hans, i'm really enjoying your thread by the way. i've been reading alot about XPS lately. i'm really interested in doing a whole board in XPS

Thanks, I like your thread a lot too!

Keep up the good work!


(by the way, your foam is dense enough since you’re not standing on it. I thought it was good to compare it with non-compsand foam. If I buy foam at a hardware store, I take a scale, a measuring tape and a calculator with me.)

yeewww, this is getting exciting. sick!

I do 2 boards with XPS rails and balsa deck (look in my blog, i put photo of build).

XPS is good because don’t drink water if ding but for each ding i have a small delam.

Lots of work for nothing. No stinger and more (strong) fiber on rails and top is easiest to do and dynamic flex is far better.

Sorry for my frenglish

The blue dow I use is 1.9# - I’ll post some photos soon of a similar build with xps rails around 0.75# core and paulownia deck and bottom…

Nice work, chrisp. One way to save some work (and material) would be to cut some of your deck dome/rail profile in before glueing on the xps. This comes to mind:

Then you'd have a smaller piece of xps to glue, and be closer to shape.

I'm not a big fan of xps, we did all that 20 years ago. The Braz bros have tested every imaginable combination.

“i found that when the wire is hot, it stretches some and kinda gets “u” shaped as you (pull) it through the block”

If you** “PUSH”** instead of pull it’s easier and you have less chance of breaking wire. I have a bow from two years ago with the same wire.

Plus you will have less shatter.

Stoked that you are doing it right by using a variac.

For the XPS rails I take a 11 x 9 sheet of Klingspore 60 grit cloth and cut a strip 4" wide and do some passes on a 2 x 4 stud to break it in and make it flexible. When you get your shape of your rail contour drag your custom sheet of sanding cloth to set the rail.

XPS works really well to balance the flex of the board when used in combination with lighter cores like EPS.


Sorry to hijack your tread.

Your doing a great job thanks for posting!



Yorky: right on! = ) i shared your seal story with my wife. we were both just crying laughing! we emailed it to some friends too.

Lemat: your Frenglish is fine... thanks for your input. did you leave the XPS "rough" only sanded to 60 grit? not finer?

Karl: that sounds interesting i'd like to see it.

Mike: thanks! i remember that thread and your comments about it. i think i will try to build something like that that i could also use to cut my outlines. i was looking into setting up a router to cut outlines but i think i will try the hotwire first... "Then you'd have a smaller piece of xps to glue, and be closer to shape." ha ha ha, yah, that would  have been good... "I'm not a big fan of xps, we did all that 20 years ago.", i remember comments that you've made about XPS in the past = ). particularly a few posts between you and Drewtang about it. Drewtang's stoke on the ride is what first got me interested in the stuff to begin with... yah, seems like you guys got your build soo wired! durability, ride, and custom! that's pretty much the holy grail for surfboards.

Surfding: thanks for the tips! honestly, if it wasn't for all your help, my first experience hotwiring wouldn't have gone as well as it did. thanks a bunch! ... "XPS works really well to balance the flex of the board when used in combination with lighter cores like EPS." thanks for that comment. makes me think that maybe the trouble of the XPS rails will be worth it in the end... "Sorry to hijack your thread." no hijack at all... did you get my PM's?

thanks for all the comments, i will post up some more pics as soon as i get some time.

80 grit screen.

XPS rails work fine for no water intrusion, small delams when ding but no “propagation”.

But to much work for me (i do Mike method) but as i shape with small hotwire custom tool i don’t like glue line.

Good luck for your build.


Sorry for my frenglish.

Any updates?

Any Progress?