Butt blocks using an old CCA treated SYP deck board

Check out this tight grain, board is in great shape. I put in a 5 foot African Mahogany replacement plank, and these held screws fine. I knew they would as I did same thing when rebuilding hull over 20 years ago, replacing old cracked oak butt blocks with the same SYP wood.

This boards has sat outside for many years, without warping or degrading. I figure that is a good test for durability. I have some old boards like this and chose it as the grain ring pattern looked so good.

They are 1.125" thickness.

 

To set in the plank, cut and ground to fit, then used an angled boat stand to keep one end pressed in tight, and pulled in using C clamps all the way to other butt block.
There is one more plank above this to replace, like a shutter plank.

Plank position is forward bow high up close to waterline. The angled boat stands do a good job, another idea, use a hydraulic car jack, dig a hole to hold jack at angle and use a long wood piece to press in the board end. African mahogany plank I cut to 7/8 thickness, and it does bend into the curved position.
This is a stiff wood.

So, holding one end in position screwed in with temporary deck screws, then place angled boat stand to lock down the end hard. Clamp board all along into position and run in screws fast.

Screws will then be replaced one at a time with larger #12 bronze screws. That way board wont move and I don't have to struggle drilling holes and clamping plank.
Deck screws you run right on in with a drill.

 

Not a fan, honestly.

This is flatsawn lumber. It has very long grains and may cup after repeated immersion or long drying cycles post immersion. You can endseal the blocking, but you can see the end checking caused by faster drying on the outside of the wood. It is perpendicular to the grain.

The length of the grain is the key. A grain running across is the same dimension of the thickness, a grain running flat is the same width of the board or longer.

Vertical grained lumber will end check, but not as bad, and has very low risk of cupping after attached.

All that said, a well seasoned board will probably not move much, but builders ought to consider grain direction and reducing movement of timber, when desired.

 

yes, it is nice and flat. Each butt blocks gets 10 #12 screws.
The others I replaced years ago have stayed flat, I also seen short oak butt blocks split in half where they drove screws.
Mahogany planks even screwed to frames can cup out of the water as they dry out.

I had to replace 3 sections of planking due to borer damage, they ate up the wood bad enough I had to replace these.
Got the upper piece in place today, used a car jack and a 3foot piece of wood to press it up at the aft butt block, Front end was held in by the splash rail.

The little short piece needed, there is a compound curve involved. Instead of bending anything (impossible task), I back ground a full thickness 1.25" piece to follow the subtle curves.
And also will block it around the top edge to the plank above.

There is a thick inner keel wing it screws into along the bottom edge, plan to screw it together tomorrow.

 

I could have replaced more planking, but I looked into all of them and they are still acceptable for use.
Especially considering they will coat an overcoat of 5200, and likely that swimsuit fabric embedded in the 5200.
Just one African Mahogany board, 14 feet long, 7 1/2" width and 1.125" thick is about $90.
It is very nice wood, and it does warp into position in the bow area, using a jack. Mostly this area has a slight twist, so that the end of the board has to twist in about 1", and there is also a slight bow as it bends in towards the stem.

These boards also get narrower towards the bow, so for here about 3/4 to 1 inch difference in width front and rear of the board, it is however a consistent taper.

 

New pic, filling the surface gouges. Used a mix of PL and sawdust.

Why 54 years of bow damaged occured, maybe the bow hitting things, I don't know.
Rough laid glue mix, not smooth sanded yet.
This is waterproof and I have pics of the same thing done 20 yrs ago and it is still perfect on the wood.
I also filled the concavity of these planks.

 

20 yrs ok, I filled these underwater planks, and you can see it is still smooth and well attached to the plank surface.

Used a mix of sawdust and PL Premium polyurethane construction adhesive. Typical don't go past a 50-50 mix. Adding in wood sawdust, it causes this to swell up, so I press it down either with a plastic putty knife or use plastic cereal bags. Then sand it down smooth.
I don't know how this price compares with using epoxy and some filler. The price of epoxy is pretty high. Advantage no mixing. Disadvantage is it does swell up, you just have to deal with it. Swelling up is also good as it forces itself into cracks. You get more out of the glue too.

The dried mix is like a hard rubber. It does flex without cracking.

I let it partially setup, then with back and forth motions using plastic putty knife, I smooth it back down. When you do that you can hear the bubbles popping. It gets stiffer and stiffer, hits a certain point where you can just leave it alone. It does cure faster in warmer weather.

 

etc... 20 years old on the wood

 

Filled all these seams with PL, will need to be smooth sanded.
It is now tight seamed.
This will all get a coat of 3m 5200 with this black 4 way stretch nylon fabric embedded someday.
https://www.amazon.com/gp/product/B08GL4V5JZ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Love how it works out. New planks, old planks, new screws, old screws, it is all good again.





I left the very front bow area undone, as I still have to do some outer stem repair way up front, and may have to spring back some planks to fit in some oak.
Some of those gaps way up front are pretty wide, I will cut some wood strips as filler to save glue.

Last pic shows a notch on the outer keel - stem, that is where worm shoe starts

 

And I have been thinking should use great stuff spray foam for the screw 'bungs' cover, cheaper than PL.
If you're filling lots of recessed holes, that is a lot of wasted glue.
Spray foam is waterproof, closed cell, cheap, easy to use and easier to remove if needed to get at screws in the future. Plus it for sure seals the whole space on top the screw.
Then when cured use a knife and cut it off smooth to plank.
Life is complicated and can be hard work, doing it easier when it is good process is a good idea, will improve your productivity.

Since I am going over it with a coating, makes double good sense. But like anyone, old habits hard to break. Using spray foam will of course also work just having a coat of bottom paint on top.