Tuesday, March 21, 2017

Too much paint over the years

Every year, when Tortuguita is hauled out of the water, the bottom gets painted with antifouling paint.  This paint keeps the sea creatures from sticking to it by a combination of biocides and ablation.  Ablation is a continual sloughing off process over time.  Ideally, after a year of cruising, all the paint should be worn off.  That way there would be no yearly build-up.  It never works that way since if all the paint ablated, there would be barnacles stuck to the boat where there is no paint.

Ablative paints are can be hard or soft.  Soft will ablate easier and is good if the boat is sitting for long periods in a marina but will wear off faster when moving.  Hard is better if the boat is moving but doesn't sand off very easily. 

Pressure washing and light sanding are usually all that is required prior to a new coat of paint.  Usually 2 coats are applied with more at the high turbulence areas such as keel and waterline.  I figured out that we have 12 layers of paint with 24 layers at the waterline.  The total weight of this paint is around 300 lbs.

I've never seen this anywhere, but from the appearance of the cracks in our paint, I have determined  that if you apply hard ablative over soft ablative paint, it is like building a concrete road on mud.  The hard paint will move around and crack.
As long as the hulls are in the water, everything was fine.  But, with the boat sitting on land in the heat of the tropics, the paints will expand and contract and the hard layers that sit atop the soft layers cracked.

The only way to fix this is to completely remove all the paint.

In Australia we got a quote of $3000 for removing the antifouling by abrasive blasting.  This process is not very accurate and also removes the fiberglass layers.  

I figured that since we were going to a part of the world with cheap labor, that I will save money by waiting so I just sanded the cracked paint at the waterline and off we went to S.E.Asia.

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