Broke Center Rib! Help

[TradGlenn]

I was attaching my rub rails this morning and had already screwed one into place and was clamping up the other side when I heard....CRACK! :shock:

The opposite side of the center rib broke off. I had a gusset on one side of the rib but the cypress itself looked as if it just split.

So I'm making up a new center rib right now but want to get some suggestions.

My rub rail is pretty beefy and it is 1.5" wide and an inch thick and is a solid 16 ft long.

It may be a bit to much for pulling the sides straight but heck if I know.

Suggestions?

 

[seedtick]

Smaller rub rails or bigger ribs.

Big stick against a small stick, big stick wins.

IIRC the strength of wood goes up with the square of cross sectional area. So a board twice as thick is 4 times (2 squared=4) stronger. Stiffness goes up with the cube. A board twice as thick is 8 times as stiff.

Also need to check structural parts so there's no grain run out or other defects that'll make the board more prone to splitting

 

[TradGlenn]

I rebuilt two more ribs out of clear pine and a little bigger stock. I also added 1/4 plywood gussets to both side of the rib joints.

I will use the extra rib as an extra support while attaching the rail. I'm also going to rip the rail down a little more.

Will see what happens....fingers crossed!

 

[FlaMike]

When I put the rub rails on mine, I wanted to keep the stress even on both sides of the hull. So I started the attachment at the center of both rails, at the same time.

Then I moved towards one end and applied the next clamp, again on both sides at the same time. Rather than continue on towards that end, I turned around and went the other way, pulling both rails in at the same time and clamping them.

I kept doing that, working my way from the center to the ends, back and forth until I got to the ends. This allowed me to keep the stress even on both sides, with no twisting or torquing.

Mike S.
Spring Hill, FL

 

[FlaMike]

Forgot to add:

Almost without exception, every time I used a screw, I drilled a pilot hole first. Having two drills makes this go pretty fast, one with a drill bit, the other with the screwdriver head.

I've always been a bit paranoid about putting screws into small to thin pieces of wood like these boats are built with.

Mike S.
Spring Hill, FL

 

[TradGlenn]

FlaMike I wish I would have done it the way you did but live and learn. I have been drilling pilot holes also and screwing the brass screws in by hand as to not over torque them.

I took a little break from the build but will try to attach the rails again in a few minutes.

 

[FlaMike]

live and learn

Exactly!

Better to learn from the mistakes of others, but sometimes you just have to make your own.

Maybe you could use my own, personal mantra:

"It's only epoxy and wood. It's only epoxy and wood. It's only epoxy and wood. It's only epoxy and wood. It's only epoxy and wood. . ."

Mike S.
Spring Hill, FL

 

[TradGlenn]

Outside Rails are on and man the boat looks SWEET! 8)

I am going to upload some pictures in my other post right now...

 

[FlaMike]

Cool!

Mike S.
Spring Hill, FL

 

[Kayak Jack]

Now that you have it on, OK> When you build your next boat, consider this.

Construct an in-whale, rather than an out-whale. Put spacers in between the boat and the in-whale. Spacers can be pieces of wood in square, rectangular, or round configuration. In any of these, you can drill out excess wood from the center of the spacer, leaving a perimeter.

Trim the upper end of the ribs so they serve as a spacer. While more work to construct, this setup has several advantages in use. First off, it is lighter than a solid chunk of wood. Spacers can be scraps wood, sanded smooth. It is a box beam, and stronger most solid pieces you would use on there. It provides a ventilated gunnel so you can pour out water when on the land. It provides nice points for lashing in gear or fastening lines for various reasons.

Most boats don't need an outer rub rail. But, if yours does, use 1/8" plywood.