Adding deck hardware to deck with plywood core

[Spot]

Added the fender washers and a view that shows an opposite chamfer on the underside of the hardware on version C to take advantage of the o-ring.

I wonder just how much butyl-less (sealant-less) hardware and how many hard-edged, 50-year-old plywood backing plates are on my boat...but not to fear, I am blessed with work at a place that stocks, uses, and scraps aluminum and FR4. I can see an advantage in epoxying the FR4 plates in place on a fiberglass hull especially if the backside of the hull is not smooth or flat.

[glenn.225]

Spot


I think you nailed it, the diagram that is.


A - not recommend, or only in the lightest of applications provided sealant is used.


B - light duty applications.


C - medium to heavy duty applications.


Definitely going to pass on if asked with full credit to you.

[Bowdrie]

More "rocket science"?
It might be interesting to see how Hinckley does it.
At prevailing labor rates it's easy to imagine a yard charging a few hundred dollars to install a piece of hardware if tasked/required to use option "C".
Locknuts?

[Carl-T705]

I think that drilling and tapping fiberglass is ridiculous. If you have bolts going through any type of material and you have threads exposed to the core material in this case you are using the wrong length of bolt. You should be using a bolt with a shank that matches the thickness of the cored material. With a bolt which has side loads such as used in a cleat the threads of the bolt work like little saw blades gouging and cutting into the core material. Yeah it's a pain to actually find and use the correct fastener for a job and yeah any type of repair generally will last for a while, and there are many ways to skin a cat. G 10 is the way to go for backing material. Aluminum encourages corrosion ( ever try to remove mast fasteners from an aluminum mast?) as well as wood. I am not a fan of sealing the cabin side of a through deck fitting, I would prefer to know the seal has failed and it needs immediate attention, good luck , I'm sure any type of repair will work, you have gotten good advice in all the post.

[Buzzman]

Originally Posted by ausnp84

Lastly, the advice above re: raising deck hardware is good. Glass a piece of g10 down (or something 5-10mm thick) and it’ll go a long way to stopping leaks.

I was going to add the above advice also, so will second this. Plates above, epoxied to deck, keep water on deck from attacking the edges of the holes around the bolts. Water can't 'sit' there and wick its way under the cleat.
It helps obviously if you can glass over it, and so spread the load around the deck as well, but a simple bevelled edge pad on which to site the cleat is helful.
Also means the line is slightly higher off the deck, making it easier to tie off to the cleat. Less of the barked knuckles on the deck surface....