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[kdaust]

I was considering a few different build methods the other day, and the simple high density EPS with traditional stringer kept popping into my mind as possibly the easiest way to 'convert' my mate who currently shapes his own boards out of PU.

So I started mentally planning it.... (yep, still a gunna for now)

1 (small-ish) block of EPS from a foam place;

Homemade hotwire (frame, battery charger, nichrome)

Stringer wood, epoxy, glass  etc etc

But getting a perfectly straight stringer cut with a homemade hotwire seemed impossible.

Has anyone considered cutting a really rough centre-line (even freehand with a saw), and then just using the outer edges of the block as the ones to glue up the stringer?

Hopefully, given the outside was cut by the factory, that would give you two perfectly straight edges to mate up.


Or am I totally mad?

[Sparrow]

Hey mate, i set up a vertical hotwire contraption which goes thru a hole in a table surface(plywood). Try searching the net for a "hotwire bandsaw" - you'll get the idea.
Make sure it's set up 90 degrees and square to the table surface, set up a fence to run the foam along and you'll get a perfect cut every time.

[Jarrod]

Has anyone considered cutting a really rough centre-line (even freehand with a saw), and then just using the outer edges of the block as the ones to glue up the stringer?

Yes.

Check for straightness yourself, but yeah, the factory should have gotten it right and that will work just fine.

[kdaust]

Nice Sparrow!

Fixed hotwire + fence = straight cut

It could also be used to follow planshape lines I guess.

[Kit Sidwell]

Its definitely the cheapest way to make a board in your backyard!
Makes a pretty good board too.
I'd fully recommend that method to anyone just starting out shaping, or experienced guys who want to get away from poly.
Centre stringers are not necessary either. But I 'spose they do give it the "look" most people are after.

[kdaust]

Yeah, its all about 'the look'. 
I've wondered about balsa or PVC foam as the stringer material.
Easiest?  Cheapest? 'Green'est?

What are foam sleeping mats made out of? I have a few of those laying around I think... How about a recycled sleeping mat (purple) stringer... lol. That'd be great for 'the look'.

PVC foam sheets from composite suppliers or even off-cuts from boat builders or sign making companies?

[Jarrod]

Is it the kind of "rubbery" feeling sleeping mats?  Like the kind they use for yoga mats?   Then it's definitely not suitable.   Actually, if it's anything you can roll up, it's not stiff enough to be used as a stringer.

Easiest, cheapest and greenest is going to be to just go to your local lumberyard and find a chunk of wood which is wide enough to accommodate your rocker.   Then just glue it in and cut away the excess.  If you have a friend with a thickness planer, you can get the thickness down to where you want it, otherwise a 1/2" stringer will probably be your lower limit.    Cedar is really easy to work with, smells great when you're planing it down, and looks awesome under glass.

[kdaust]

Yeah I figured as much about the sleeping mat, but thought i'd throw it out there.  Always better to re-use than to discard.

I guess the wood is an (relatively) easy option.

I might also just check out sheets of PVC foam if I head out to FGI to get some epoxy.  It seems pricey, but if you can cut straight strips and bend it with a heat gun [I seem to remember this being done by a few people - paul being one I think... is 'bendability' dependent on the crosslinked vs uncrosslinked foam structure?], one 4' wide sheet could net you up to 12 centre stringers (or 6 parabolic) with a maximum 3" thickness.

Foam would be easier to cut than wood I would think?

[lemat]

Has anyone considered cutting a really rough centre-line (even freehand with a saw), and then just using the outer edges of the block as the ones to glue up the stringer?

Hopefully, given the outside was cut by the factory, that would give you two perfectly straight edges to mate up.


Or am I totally mad?

Sometimes i made it like this, it's ok. For stringer i use Komatex PVC foam, it's the same weight than middle weight wood, you can roll it but it's strong for a stringer and easy to work. Some surfer find my Eps Epoxy with wood stringer to much "rigide" and ok with PVC stringer.