Thru Hull / Strut Backing Material

[Stupidav]

Come to find out while replacing my Rudder Supports, the Backing material for my Struts is falling apart. The original is / was some type of Plywood.

What is the best material to use for that now? I have a feeling that Treated Plywood might not be the best (could be wrong). I have seen people utilize various types of materials. Considering it is for the Struts, I would like to use the best / better material for this. Anyone have any recommendations on a better / best material (even if it is plywood)?

[prowlersfish]

Plywood was used I believe. Todays plywood is not like it used to be I used Oak on mine ( F36). Others have used marine plywood, marine plywood with epoxy, plastic boards and G10 fiberglass I would never use treaded plywood, it has too many voids. If I was to replace my Oak I would go with G10. G10 is a fiberglass board it is made with epoxy. It is hard to cut but good stuff. I used it on my rudder ports fwiw.

[captainmaniac]

Had one of mine replaced a few year back as well, and I believe 'my guy' made the new one out of oak.

[Stupidav]

The one thing that comes to mind, is why has it always been Wood for 99% of the backing plate material? Regardless of brand of boat or what it is going through the hull, there is almost always a backing plate, especially if below the water line. Someone once told me it aids in keeping the item perpendicular to the hull, by conforming to the inside surface of the hull, which is why it is wood. Someone else once told me that it is because it will absorb a minimal amount of shock should something happen. Yet some manufacturers provide some type of plastic or other type of material to help with the perpendicular theory, although I have even seen spring-loaded apperatuses for some odd-ball items, supporting the absorbtion theory.

While I am leaning towards going with a "Polyester Resin" Fiberglass Block / Panel - 1/2" thick for the Strut backing board, and I also figured that I am going to replace the rudder mount backing board as well, I just don't want to load another can of worms for the future by doing so. At least initially I am having difficulty finding 1/2" thick G10 board, which is why I am looking at the product that I am looking at.

[prowlersfish]

Polyester should be fine. Here is a link to G10 They have different types. Wood is also fine.

https://www.mcmaster.com/products/~/mul ... ars/?s=g10

[P-Dogg]

For mine, I used fiberglass. Since I also did all of my through-hulls, including my exhaust, I had a countertop shop with a waterjet cut all of the shapes for me. Not inexpensive, but you get net shapes without risk to your health or shredding saw blades. I would also consider exterior plywood soaked in epoxy.

https://www.mcmaster.com/8537K46/

Some of my prior work: viewtopic.php?p=81909&hilit=tricab+unde ... ust#p81909