Five year bottom paint?

We cruise N Pacific waters above 56°N. Aggressive hard growth (mainly barnacles and mussels) is very normal here. 

Water temps (°F) vary from mid 30's in some of the glaciated fjords, to as high as the low 50's in the Gulf of Alaska- with seasonal variations. You can see barnacles, mussels, etc. on the rocks at low tide everywhere. 

We can even judge the depth of tide by which intertidal growth layers are visible. (Sounds like fodder for a future post...)

Sometimes those cruising warmer waters think hard growth in minimized in cooler water. It isn't. Anyone who takes their dinghy (or kayak, etc.) to shore in these parts can attest to the razor sharp growth attached to any hard surface that spends at least part of the time underwater... 

The following photo we took in Jul-2022 demonstrates an extreme example of this. The image shows a small portion of Margerie Glacier (a tidewater, or fixed glacier at 59°N; 137°W), and barnacles growing on the (fairly) recently exposed adjacent bedrock. I can assure you this is not tepid water...

 

What antifouling paint do we use? Divers cleaning other boat hulls in the harbor often ask us this since ours has yet to need cleaning.

The owner of a commercial fishing boat across from our slip told us about a time he couldn't back out of his slip. He thought his transmission had malfunctioned. A diver revealed he had over a foot of mussels and barnacles coating both sides of his 48 inch 4 blade prop. All was well after the diver used a spud bar to peel off the growth- which had accumulated over 5 months of sitting at the dock in winter. 

We first applied this ablative antifouling paint in Apr-2017. 

Our next haulout was 4 years later in May 2021 (because we needed an insurance survey.)

Note that Denali Rose spends all of her time in the water- except during routine, ~1 week haulouts every few years. 

Following are a couple of photos of the hull as it is still dripping from being hauled-out after sitting at the dock for 4 months over winter: (4 years and 1 month since it was last painted...)

Denali Rose is 50 ft. OAL. This is the smallest travel lift in the yard @ 150 tons.  
We prefer it when our boat looks like a toy in the travelift...

Pre-pressure wash image demonstrating the clean hull [after 49 months in the water full time] with hard growth on some of the metal components.

We coat UW metals with Pettit Prop Coat. It lasts us about 3+ years when overcoated with Hydrocoat per the manufacturer's directions.

Note a bit of greenish slime on the hull and keel from sitting unmoving at the dock for 4 months over winter...

In the above pre-pressure wash images, you can see the 4 year old black Hydrocoat paint would likely have lasted at least another year, but there was some hard growth on some of the underwater (UW) metals (which represents about 13 months growth since the last time a diver cleaned the zinc spray coated UW metals and replaced the anodes. No diver hull cleaning. Ever.)

We have never had a diver clean the bottom since we started using Hydrocoat, but every year or two we do have a diver renew the anodes and remove any hard growth on underwater metals as needed. (We inspect the hull every 6 months or so using a GoPro camera mounted on a boat pole.)

Of course, since we were hauled out for the insurance survey, we renewed the bottom paint in May 2021.

We started using water-based Pettit Hydrocoat ablative bottom paint  in Apr-2017. (NOT the ECO version without copper...) We re-applied Hydrocoat during our insurance survey haulout  4 years later (in May-2021) the day after the above photos were taken. (And the hull is still pristine as of the publishing of this post on 19-Jan-2023...)

Our next haulout is currently planned for 5 years after the last painting in May-2021; spring of 2026.

Stay tuned...

Of course, YMMV...

PS: Other advantages of using a water based (low VOC) bottom paint include we can have it mailed USPS-  which is typically our most ecconomical shipping choice in remote locations. And we can use it to coat through-hull transducers that specify water-based antifouling paint only. (Most potted transducers.)

PPS: What about bottom paint considerations in areas with warmer waters?

In case you aren't familiar with Practical Sailor's [continental US] regional bottom paint testing results, here is a representative article that may be useful. (Scroll to bottom to see extensive rating tables...)

Jamestown Distributors [JD] also conducted bottom paint surveys for several years in a row, and I found this recap article in case it is of interest.

Following are a couple of informative graphics from the JD article linked above:






I couldn't find their live Google map, but I remember you could drill-in and read individual submissions, so asking JD for access may prove useful if you are interested in what boaters reported using (and their ratings) in specific regions of the world.



I recall using a hard, high copper bottom paint (Trinidad?) when I spent 7 years in the S Pacific tropics decades ago on a different boat. Cleaning the bottom monthly was good exercise...


More FWIW info.