I have an older wood Eggharbor 37 want to use HDPE for worm shoe

The prior worm shoe is Cumaru, very hard wood, It survived as in remained keel attached but worms attacked it, and from the bow back 6 feet, it disintegrated easily by prying.

Was a waste of couple very nice boards, it was painted. Waste of money and time. It was 10 years on the boat. I am hoping new board does better. These borers easily eat the hardest woods.
10 years ago I paid twice the price for that Cumaru wood, the wood pic today cost $43 each.

 

At first glance, I would have said that the board with narrow growth rings would be stiffer, but on closer inspection, the summer wood is thicker than the early wood on the lne with wider rings. I would agree with your choice of which to use where, but I think that the strength and stiffness will have to go to the judges.

I was looking at a pallet of foundation grade .60 CCA SYP this afternoon, and saw some good examples of the range of variation to look out for. Next time I get out there, I will take a picture and edit this post to keep the pictures closer to gether. One in particular has rings with much thicker early wood than late wood, and others looked more like the ones you have. It would be interesting to support the ends and place a weight at the center to see if one is stiffer than the other.
EDIT:
I was not aware of 2.5 pcf CCA treated wood. Living as far from an ocean as possible on this continent, it isn't something mentioned locally. Now that I know what to look for, it is easy enough to find.
The best example of a presumably low strength pressure treated board is below. The lightly colored board at the bottom has narrow summer wood rings and very wide early wood rings. It is at the bottom of the pallet, so I can't do anything with it for a while. I tried crushing a ball bearing between two boards in a vise. It does give some very different results, but I need to set up better for a picture. The ball will see exactly the same load since it is between the boards, so it give a comparative result. There is a tool for measuring brinell hardness in the field. It has a set of standard known hardness samples, a ball bearing and a 'slide rule'. You hit the thing with the bearing between the known and unknown hardness and compare the indentation diameters. The slide rule gives a brinell hardness value based on the sample and the diameters.

 

Yes will test for stiffness. I just thought narrow tight growth to be stiffer

Editing, ok, the narrow grain board has greater stiffness. I laid them flat sides down, side by side with 2x lumber positioned at board ends to test their springiness. I can depress both boards flat onto the concrete in their centers.

The bundled boards at the Treated Lumber Outlet store all looked as pretty, decent wood.
Nice and flat and straight with no or few small knots. They might be related to this company, like they get wood from them.
Decks & Docks: The Top Marine Construction Supplier (decks-docks.com)

Searching location our local stores show up on their website
Locations - Decks & Docks Company (decks-docks.com)

If there is a location near you, why not go for the 2.5 CCA marine submersible wood they have.

 

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