one of my 2" thick wormshoe boards bowed due to tension when split from the 2x8

The other side is fine.
Board is bowed like a bow and unusable, to stiff to straighten. about 2" by 4" by 7 feet, and very stiff.

I am planning on splitting it down the middle then a flip and glue to straighten it.
It is 7 foot long and I think I can cut it using a new 6 TPI jigsaw blade.

Idea is cut it following the curve down the board center.
Turn the cut piece in against the other and glue together with clamps.
I may glue it against a long steel box beam I have here.

So if you have a bowed length, how do you straighten it without loosing wood?

I was trying to think, what if I center cut it freehand down the table saw, would that leave me with nothing usable to glue up straight?

 

Pic showing what's going on
Laid against uncut wood to show the bow-curve

Wife stood on one end and I pushed on other, and it simply lifter her up, it will not straighten out with force that I can manage, and even so that much tension would be bad on a keel bottom.
I want it full length as it bridges across my keel bottom repair.

The board under it seeing it was cut from that, may also be tension wood on the left side, seeing the tree center is offset to the left.
The right side likely will cut off straight, but I don't like wasting wood.
It is just a wormshoe.

 

The grain looks like it goes to hell on the far end of your board.
I’d try cutting a piece off the other side, but cut it wider in case you need to trim it straight.
That failing, slice it up and relaminate it or buy a better board. A new piece of lumber will be far cheaper than a bunch of work to salvage what you’ve got now.

 

I could see where it begins bending off, Maybe would just have to slice it down that far, then glue the cut end to straighten.

I need to take a good look at it.

This wood is 2.5 CCA marine treated, its not cheap and a long drive to buy more. Big board underneath is straight, it has some tension in it. That gets exposed when cut.

 

You cannot cut tension wood straight, In general terms, making it narrower allows it to move even more.

That board is a terrible board for anything (boaty) because the pith is in it. Usually, if the pith os straight down the board; it will not be tension wood; so you could try a rip and epoxy lam, but a crapshoot. It might get worse and then need lotsa clamping to laminate.

The only way to use that board, at its full width, is to horse it over as it connects to the boat. This could be done with ratchet strap and a car hitch. You might end up with some lift off the keel, which defeats the purpose a bit; that is the risk. 5200 and 3” screws? I forget how you said you were bonding it, but mechanical is the only way with that board.

I know a little bit about wood.

 

Pith - Wikipedia https://en.m.wikipedia.org/wiki/Pith

Not the best choice for the shoe. Sometimes, you can fingernail into the pith..

 

Guys, I can't dig into with anything, its not soft anywhere.
It is only for a wormshoe.
If I can glue it reasonably straight, I am going to use it.

I drew a line right down the center, and getting ready to cut it with a jigsaw.
It's a broiler of a day, but I am home in the shade.
Currently the eastern seaboard is in a massive heat wave

I like that this piece is really hard and stiff. should hold up decently as a wormshoe.

It is flat, only bowed in one direction, not twisted or warped.

 

I split it down the middle, took a while to cut with a jig saw.
Planning on screwing one side to the flat board I have to straighten it out flat,
Then glue, clamp and screw cut off other half back on to the same side I cut, so the cut edges face each other.
Jigsaw cutting thick wood always goes squirrelly on me. That way the outer edges will remain true, and as long as guide board is flat, the glued board will be flat.

 

Typically, when you are trying to make something crooked straight; you overbend. So, if both pieces are bent same, to laminate straight; you overbend. For example, let’s say both pieces are 8 feet long and bent same way; you can either flip and bond them, or you can bond them back together 10% away. Or for a board with a 1/2” error; you’d overbend it if bonding the same cut. Otherwise when you release it; it will bend again.

Now, if you want a 4” bend; you bend 4” plus 0.4” or 4.4”. But here you want to remove the existing bend. Let’s say the existing bend is 3/4”. Overbending it is done at 10% of 3/4” or 0.075”, or about 1/16th of an inch. This means you bend it 3/4” to straight plus 0.075” or a bit over 13/16” from what it is, or if you want it straight, a 1/16th inch extra bend from straight, or middle on the line and each end 1/16th over the line for bonding the cut edges. A bit does depend on whether anything odd happens when you cut as well. If the boards open away from each other; you may not want to overbend, etc.

I failed to overbend my rooftop laminations and they were a little flatter than designed…and discovered this 10% thing the hard way.

 

Ok, It is done and decently straight

The board cut in half, one had more tension than the other


I screwed the straighter one to the big board
Laid some PL glue on both pieces, and screwed and clamped them to each other



IT is so hot and humid, feels like 105*F, the adhesive glue cures fast.

Removed all screws.
smeared some pl over the whole board.
Let that dry
Then laid it flat to the big board
It developed a slight bow on the wide side, but it is a weak bow, and clamps easily make it flat

The board edge is now straight and will fit straight on the skeg keel base

 

Horsing it over, it is too strong and thick, it was really stiff all together before the cut. I weigh 240 pounds, and me standing on it on edge could not make it flat.
Then imagine if you could, all the tension on those screws, whole thing could come loose.

After I cut it, it got so much weaker, I easily made it straight. I lost at most the width of a jigsaw blade, which is not a lot. The keel bottom is 3.5" and this is about 3.65" using my digital caliper.

 

All the glue I use is this PL poly adhesive, I found it is 100% waterproof.
I use the 28oz tube as it is cheaper than the 10 oz tube for what you get.
Loctite PL Premium 28 oz. Polyurethane Construction Adhesive Tan Cartridge (each) 1390594 - The Home Depot

 

Here it's cut and finished for bottom paint and straight
I coat it with that PL rubber glue first, just a thin coat.

I also edge laminated a 1/4" thick piece on one side and cut it straight on the table saw.
So now it is 3.815" wide. You can barely make it out on the left edge of the board.



And here I am using West Marine green copper paint.
Keel bottom also gets a coat of rubber glue.
Painting this, then I paint keel bottom, and screw it on.



Heat wave is still on. But will break this weekend, I think.