Okay, I’ll add a bit, based on 20 years plus in the ding biz;
With the single exception of Neira’s method, adding stringer stuff will virtually guarantee a bad alignment both side-side and along the line of the bottom. I have had to cut apart more than one board that somebody used dowels or similar in holes drilled in the foam, and it screwed up the alignment of the two pieces. There is no easy way of making holes in two irregularly broken pieces of foam that will line up in every way.
Making oversize holes, filling 'em full of resin plus thickener goo, adding dowels and sticking 'em together…well, that not only buggers up the alignment but it also makes the board Really, Really Heavy.
Taking a router to the board, carving out channels to set the ‘reinforcements’ in, filling the channels full of goo ( because the router wavered a bit) and then setting in a few sad pieces of wood…makes the board heavy, looks like hell and adds no strength.
That’s right, strength added is zero. You are sticking wood into foam, right? Well, do a little demonstration; a test model.
Consider Irish Coffee: coffee plus irish whiskey plus some whipped cream on top ( a dash of creme de menthe like a resin swirl on top of the whipped cream is optional) plus a couple little narrow straws stuck into the whipped cream, just like the wood pieces stuck into foam. Ok, have one, but before you drink it, do the test.
Grasp the straws firmly, and brace yourself. Using all the strength you have ( which is why I suggest bracing yourself ) - pull the straws through the whipped cream.
Wasn’t real hard, was it?
Nope.
By the same token, sticking wood into foam won’t do jack. Nada. Zero. Wood against soft foam, wayull, the wood crushes the foam and there you are. No strength added. It’s a waste of time.
I have fixed quite a few busted boards with no additional stringer stuff ( and using a jig kinda like you have there ) , just wrapping glass around the board and they were just as strong as they were originally or better. In fact, you have to be careful to feather the edges of the new glass, or else the flex and strength is messed up and the board tends to break right at the edge of your repair.
But there are a few problems with doing it with a jig and no ‘stringer thinger’.
First is alignment. You need to get it aligned in three ways: rocker, twist and side-side. And it’s a pain, you have to set your jig to deal with all of those. And you have to set your jig differently with every board, every break. To hold the damned thing in place, you wind up strapping it in place, and that tension on the strap… yep, out of alignment.
When a board busts, some of the foam is permanently crushed. So if you butter the foam on both sides with goo, set 'em tight, you have a tweaked board, an abrupt change in rocker and usually a twist besides. You also have excess goo, which has to be sanded, and you wind up sanding into the foam, which has to be sanded, which has to be filled, which has to be sanded… Besides which, the goo is a lovely lubricant. So that when you put a little tension on the board to hold it in the jig, the pieces slip out of alignment. Been there, done that, repeatedly. Wasn’t even close to fun.
But the biggest problem is this; your average surfer is a f’ing moron. A halfwit who believes the nonsense that is the ‘common wisdom’ ( an oxymoron in itself) of surfing and that about stringers in particular. And if you are fixing boards for fun and profit, you have to deal with said f’ing morons, who will belabor you with “Duuuude ( zaaap ) , I mean, duuude ( zap zap) , if you don’t put in some gnarly ol’ stringers, it won’t be the strong” and insist on some sort of non-functional stringer thinger.
You have to deal with said morons, in order to get paid for the repair. Which means you have to pander to their idiocy to some extent. That or else educate 'em, and usually they have gone a lifetime without learning a bloody thing…it’s not worth it unless you have a few decades of spare time. Me, I don’t, especially at my age.
Enter Neira’s Really Nice Way of Fixing Busted Boards. If you did a decent job with your hand saw, your side-side alignment is smack on, your alignment with regard to twist is smack on unless you do something really weird, the rocker you adjust by eye when the wood strips are in. The slightly oversized splints in the saw kerfs act as a clamp/jig so that they hold it all in place until the glue goes off, and then a few swipes with a block plane gets it down to where it needs to be.
And it also takes care of the f’ing moron factor.
Now, if you want to keep it from showing ( much) , use basswood, less than 1/8" thick so it’s just barely wider than the handsaw cut/kerf, and don’t even think about using a power saw of any kind. The friction against the foam holds things nicely. You do not need or want anything thicker. This is barely more than veneer thickness, and just about invisible.
It’s a nice white wood, it’s cheap, you can find it in 3" or 4" wide x 24" long x several appropriate thicknesses in hobby shops, it will look a lot like foam and won’t be immediately visible. Compare that to any other way of adding a stringer or something like it, which will frankly all look like hell, add a lot of weight and add zero strength at the expense of a lot of labor.
Don’t even think about using 1/4" plywood or something like that. The key word is ‘thin’.
On that particular board you’ll be doing a yellow glass lamination as an inlay, so that’ll also cover it up pretty well. Then do the rest of your glassing with clear and you’re set.
hope that’s of use
doc…
