Hull protection

I've seen many posts her & elsewhere about various additives for epoxy including graphite & suchlike to increase durability.

Rather than messing with the epoxy does anyone have any experience of durable hull protection from paint only & the various additives which may be added to paint to achieve this ? 


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RE: Hull protection

Other than the mixing, epoxy is no more difficult to apply than paint.  There are several marine paints that are also two-part, so you'd be better off going with epoxy.  But the biggest issue is that paint isn't very structural, while epoxy is.  It has to do with the length of the molecules which translates directly into bonding strength.  

There are some additives for marine paint, but mostly for non-skid, gloss flatteners, etc.  You could do a little research on Pettit paint, Interlux, etc. (basically search "paint" on westmarine.com). 

I actually used graphite/epoxy as the finish layer on my Eastport Pram.  It's UV and abrasion resistant.

RE: Hull protection

   Thanks for your reply CaptainSkully

The reason I ask is because I've been chatting with the naval architect responsible for the new UK RNLI Lifeboat, the Shannon class which is designed for a very long service life including beach recoveries, not necessarily on sand.

The attached video shows the Shannon beaching at speed on a North Wales pebble beach 

https://www.youtube.com/watch?v=IBcTXJ7UGVg

For their protection, after trying several different methods including stainless steel skid plates they settled on a special epoxy paint used to protect the waterlines of ice class vessels including icebreakers.

The active ingredient for this durability is powdered glass, mixed into the paint only

RE: Hull protection

The active ingredient for this durability is powdered glass, mixed into the paint only.

Interesting... doesn’t WEST System use powdered aluminum as a wear additive in a similar manner? Graphite’s intended more for its lubricity (surfaces that slide against one another, or bushings housing rotating parts) or its UV-resisting capability. Careful there though if’n it gets any kind of sustained exposure to sun; the solar energy absorption can cause significant expansion, maybe lead to warping / cracking or delamination in the extreme.

Years ago, talking with engineers who built Chicago’s Deep Tunnel storm water mitigation system they said they used a high strength concrete formulated with iron filings for the vertical parts of the system that needed to withstand the highly erosive volumes of runoff when that changed direction. Think of tons of water falling hundreds of feet then being diverted into a horizontal, concrete-lined bore.

RE: Hull protection

For boats that are not running up pebble beaches at high speed, I find water-borne 2-part cross-linked linear polyurethane paints very useful. I used the stuff on my brand-X sailing dinghy and the only thing that penetrated it so far was an aluminum bracket on a dock.

The 2-part LPU is quite tough on its own, but adding the cross-linker locks the molecules into a very solid and tough coating.

That said, the same boat has a graphite epoxy bottom.

Laszlo

 

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