Question-Encapsulating Aluminum in Epoxy in Bilge area for Mast Compression Support ?

[tsenator]

Question for the group -


Would you think its ok to encapsulate large blocks of Aluminum in Epoxy in at the base of the Mast Compression Support ?.


On my particular sailboat it is a known problem that the support under the mast compression post in the bilge could compress overtime and 'sink down' a little (on my boat its about 3/8"-1/2"). The manufacturer put marine grade plywood on-end built up and fiberglassed in and its pretty solid, but over time the wood eventually gets some moisture (even encapsulated in fiberglass) and starts to give a little - The manufacturer even admits it and has a "tech-note" on repairing it.



In the manufacturer tech note they advise removing the wood and replacing it with chop strand and resin mix. I don't have access to a "cnopper gun" and the area is fairly large (8.5" L x 13" W x 8.5" H)


Some people have said they epoxied in layers of 1" G10 FR4 Glass Epoxy
(basically blocks of solid epoxy) but that is a LOT of G10 - Probably about $700 is G10 alone , not counting epoxy and glass.


I have heard of people replacing the marine plywood with some solid wood like oak or something like that (even had a marine repair facility say thats what they wanted to put in there). I know it would be far superior to what was in there but its still "wood" and even if I really encapsulate the hell out of it, there is always a chance of water ingress over time and getting to the wood no matter what you do.



Now to the question. I have a friend with access to solid blocks of aluminum at a great price (free or a case of beer ?) that I was thinking of being used as some of the 'solid filler' that I would try to encapsulate in my compression post base. Would anyone see an issue with that ?



I understand that I would need to do a really good job prepping the material to get the epoxy to adhere (I was thinking of 'G-flex') and think I could make it work, but what do people think about the "Long Term" effects of aluminum encapsulated in epoxy ? Does anyone think there is a chance the aluminum could get compromised and deteriorate and crumble - How does it stand up in an oxygen deprived environment ? (all one needs to do is look at a aluminum beer can after a few months in the warm wet bilge -- they go eventually)



Thanks in advance for anyones thoughts and inputs - or other ideas .

[thinwater]

G10 is sort of internet myth. There are many other excellent pre-cast fiberglass sheets for 1/3 the price. Unless you need the specific specs of G10, it is a waste of money. Buy a structural grade.


Another option is to use wood. How long did it take to fail the first time? Honestly, the boat will probably be scrap in another 30 years. Preserve the wood by soaking with borax and then coating.

[Orion Jim]

https://www.lbifiberglass.com/product/gpo1/

I’ve used this. Great stuff, reasonable price.

[Reefmagnet]

How long do you want to keep the boat for? My boat was suffering the same malady. The problem is the softness of the wood originally used. It causes the base to compress slightly under load which eventually causes fractures in the glass which then lets water penetrate to the wood. I cut the top off my base, dug out all the mush and cleaned it up. Glassed it inside using epoxy to seal it. I then got off cuts of heavy, dense hard wood planks from the scrap bin of the local builder's supply for free which I cut and trimmed to fit the space. I then threw in a bit of filler comprised of epoxy and ground glass to fill the voids around the edges, glassed on a new top and slapped some more glass around the outside of the base for good measure. The worst part of the job by far was digging out the old mush.


I'm confident this repair will hold up for the remaining life of the boat and even if it gets wet, the wood used should survive 20 or 30 years at least. Sweat equity aside, the cost of the repair was minimal.

[Breaking Waves]

Originally Posted by tsenator

Would you think its ok to encapsulate large blocks of Aluminum in Epoxy in at the base of the Mast Compression Support ?.
....
I have a friend with access to solid blocks of aluminum at a great price

do you know the grade of the aluminum?

[skipmac]

Why encapsulate it? Good Al alloy like 6061 would last as long as the boat as is.

[ferrailleur]

Epoxy is the KING of encapsulating....You can encapsulate any material in epoxy and it will be preserved in its original state for ever!

[RaymondR]

Originally Posted by Reefmagnet

How long do you want to keep the boat for? My boat was suffering the same malady. The problem is the softness of the wood originally used. It causes the base to compress slightly under load which eventually causes fractures in the glass which then lets water penetrate to the wood. I cut the top off my base, dug out all the mush and cleaned it up. Glassed it inside using epoxy to seal it. I then got off cuts of heavy, dense hard wood planks from the scrap bin of the local builder's supply for free which I cut and trimmed to fit the space. I then threw in a bit of filler comprised of epoxy and ground glass to fill the voids around the edges, glassed on a new top and slapped some more glass around the outside of the base for good measure. The worst part of the job by far was digging out the old mush.


I'm confident this repair will hold up for the remaining life of the boat and even if it gets wet, the wood used should survive 20 or 30 years at least. Sweat equity aside, the cost of the repair was minimal.

You probably had access to Australian eucalypt hardwoods which are highly rot resistant and very hard and tight grained. Perfect for that job if one can get ones hands on it.

[skipmac]

Originally Posted by RaymondR

You probably had access to Australian eucalypt hardwoods which are highly rot resistant and very hard and tight grained. Perfect for that job if one can get ones hands on it.

In the US a good option would be Live Oak. Very dense, strong and rot resistant.

[RaymondR]

After many years of experimentation attempting to glue aluminium with epoxies a friend informed me about a product called "Renco" which was available in the plumbing section of big hardware chains in Australia. It is a two pack putty used for sealing cast iron pipes and bonds to alloy like nothing else I have ever seen. I suspect that if one bonded an alloy plate on top of your existing mast step with that stuff it would be there for the life of the vessel and never allow water underneath to cause corrosion.

[Reefmagnet]

Originally Posted by RaymondR

You probably had access to Australian eucalypt hardwoods which are highly rot resistant and very hard and tight grained. Perfect for that job if one can get ones hands on it.

Yep. Spotted Gum. Has properties more like metal than wood!