I recently bought an 8 x 5 sheet of foam from Home Depot, yes the cheap stuff, to start my first project. But Im not sure how to put in the stringer, or what to use? Just balsa wood maybe? And where would I find it? I looked there but they didnt have anything that looked good. Please help! Thanks
-Don Warren - Stuart Florida
Question is WHY a stringer.
Most guys use it to hold the preliminary rocker, that’s all.
You can use paper sandwiched by epoxy just as well.
High density Airex works excellent, divinicell also, with epoxy sandwich.
Some don’t believe in stringers, just laming over the rocker table on one side, it holds the rocker just fine when cured.
I found myself in a discussion with Greg (no stringer) Loehr and “Doc” about this subject of stringer vs no stringer… One of them pointed out that a stringer will eventually splinter under stress and the splintered stringer will puncture the glass from the inside resulting in a fracture point and a broken board. I fell back on the Yvon Chouninard/Patagonia experiments with the pressure gauge and foam blocks that were tested to the point of breaking. After breaking a board that was glassed with epoxy I have to conclude that overall flex capabilities of the blank and resins involved play a part during actual use. My epoxy board seemed quite a bit more flexible than my polyester boards. The fact that I chambered a thick redwood stringer that was sandwiched between two thin red cedar stringers may have been a factor. Anyway, after schlopping the takeoff on a wave that was not that critical, I broke the board. It appeared to break at one of the chambers where the redwood splintered. I’m not at all sure that a stringerless board glassed with epoxy might have just flexed with no damage. Any board will break but I advise to proceed with caution and consider the flex characteristics of resins, cloth and blanks that you will be using.
So no stringer at all will work just fine? Thanks for replying. I saw most boards off the shelf come w/ a plywood stringer. I am just starting on shaping boards so any help would be awesome! Thanks again though!
I CANNOT and do not, see the use of plywood in a stringer. Heck, half the grain runs the wrong way! Okay, okay, it’s cheap.
The only real needs for a stringer I can see are: one, it’s a useful reference line when templating, and two, it provides stiffness when shaping. After that, the glass job should provide the all the necessary strength AND stiffness.
But blanks are sold with stringers, and many tanks I shape want three. Okay, that’s fifty clams more for the blank. I like the look of a triple stringer tank with a clear or lightly tinted glass job, myself.
According to the EPS Construction Primer, the recommendation for EPS is no stringer up to 6 ft. I made a 6 ft’er with no stringer and then a 6’6" with a 6" wide fiberglass stringer sandwiched between the layers. There is definately a noticeable difference. No glass on the boards yet, but the 6’6" is a lot stiffer.
Actually, NO boards come with plywood stringers.
Clark and Walker blanks come with one solid thin piece of wood, as poly resin is not stiff enough to go without the wood stringers.
When you go styro, you need epoxy resin, and it IS stiff enough, given a shape that is stiff, to go without stringers.
There might be some advantage to stringers on styro epoxy for anti break, but still not proven yet. If it anti breaks, it self destructs from the inside out, as the styro foam is very soft and weak, and can sheer from it’s nearest bond. Actually, styro sheers, the bond is fine.
I’m shaping a 7’2" right not, not sure about the tail yet, but i think its going to turn out ok, I didn’t know if theres anyway to make a rocker w/ no stringer? I guess I don’t need one that bad since this is an experiment and i don’t see much surfing on this…but still it would be nice. Is there any way at all to make the rocker w/o a stringer? About the plywood, I was reading about Orion and Nev surfboards and it said built with plywood stringer…so thats why I said it. But anyways thanks, this forum has been a big help already!!
-Don Warren - Stuart Florida
Is your blank just one piece? 8’x5 ???(you said in first post) One 5" thick piece?
You can bend the rocker in if you are gluing up layers of foam. The glue will hold the rocker when dry.
See pic number 3 in this set below.(Sorry about the chic picture. Well not really sorry because I am sure everyone enjoys it. I accidentally uploaded her over the original photo)
http://home.earthlink.net/~bike-surf-photos/boardnumber1.html
I think I might have to start project 1 over…unfortunately. I bought the wrong stuff. I knew from the beggining it looked off, and felt kind of light, and thin…oh well. Im on my way to Home Depot in 30 minutes!! I bought regular styrofoam, doesnt work so good, no smooth cuts or anything…attempt 2 on project 1 will begin shortly!! Thanks!!
-Don Warren - Stuart Florida
Headhigh, your board looks great! I was wondering, are the last pics w/ no glassing?? Is that just the foam blank? Thanks for all the input!
Dang! I must have done something wrong with my EPS blanks. At NO time in the process did the rocker & curves look like the ones on the stairs next to the brick wall.
Teach me, Maestro. 
headhigh:
cool pictures. I just have a few questions for everyone…I want to shape a 5’11 retro fish. This will be my second board. From the sounds of it, I take it a stringer isn’t necessary?
Is eps harder to work with?
How many layers of foam of what thickness are recommended?
Can you tint epoxy?
Thanks. Anything else would be appreciated.
There really isn’t a definite answer to the stringer/no stringer question. There are lots of opinions and methods ranging from no stringer to flat fiberglass strip between foam layers to perimeter stringers, etc. Each method seems to have advocates. I’ve always believed that in a 3" thick blank with a center stringer, you basically had a 3" thick piece of wood adding ridgidity and strength. In basic tests with blocks of foam and a mechanical press that breaks the block of foam, the pieces with stringers held up better. Actual stress created by breaking waves and riders may be quite different from stress created by a mechanical press. Other design factors such as controlled flex have led to partial stringers that end part way through the length of the board…
Lanny Shuler of Shuler surfboards Seaside Oregon Uses 1/4" plywood stringers.Lanny hot wires XPS & EPS and glues up blanks with plywood .I’ve shaped with his blanks. So far no problem. Stringer planer needs to be real sharp. Gordon
xSURF-Thanks! Yep, thats just the foam blank, no glass yet.
Benny - That is a custom order with special curves. Wouldn’t you like to trace that outline for a template? 
Shores
1-Stringer not neccessary for 5’11"
2-Its easy to work with. Just be careful when you are fine tuning or you will rip a chunk out of it.
3-Whatevers available near you. 2"+1", 1"+1"+1", 2"+2"…
4-I don’t know. Search archives.
I’ve seen the Schuler blanks down here in Santa Barbara. Now Hydrofoam is making them that way, and at first look questioned the 1/4” plywood stringers. I ended up asking everyone I knew that had epoxy experience about the issue and ended up w/ no definitive answers. Casey McCrystal is using them exclusively.