Media blasting or sanding?

[John w]

Hi Ladies & Gentlemen

I need some help with my project.

I have a 2011 Bavaria 36 cruiser sailboat & have 10 years of overpainted antifoul on her as you do; we have owned her for 4 years but little use in the last 2 years due to the Pandemic.
Come March 2022 I have her booked to come out for a few weeks and have the following decision to make

I was thinking of having her media blasted at an additional cost of £ 900.00! or Do I sand down the original antifoul to a decent smooth finish then prepare the keel with flapper wheels & Fertan rust convertor (was quite rusty last time out June 2020)Then use barrier coatings & then antifoul

Some basic questions.

The keel will need to be sanded then the pitting treated with some sort of epoxy coating/filler can anyone suggest or give any real-world experience on using something to fill in the pitting?

Has anyone sanded a cast iron keel & then converted the rust with Fertan? Do you know how long it would take to prepare? Is there a sequence to doing the work?

Can anyone suggest a suitable barrier coat to apply if I have her blasted? & how many coats should I apply?

Is there a set way of preparing the keel? And do I need to wipe down with acetone before applying the fertan rust convertor? Also is there a time limit from sanding to applying the rust convertor?

Is it normal to just carry on Appling multiple layers of antifoul & is there a limit as to how many coats are too much? I have used EU 45 antifoul & have found it very good for the fouling in the river Cattewater Plymouth, So will continue using EU45.

 

[Tranona]

Blasting every time if you really want the job to last. Removing or even sanding is hard work and just about impossible to get a surface, at least on the keel to get anything long lasting to adhere. In my experience Fertan is useless on cast iron keels.

There really are only 2 choices. If you do not intend keeping the boat then just clean up the hull sufficient to get a new coat of AF on every year. With the keel, patching every year is probably most peoples' choice - grinding out the rust then prime and antifoul. Next year do the new bits that appear during the season. If you want a long term solution then blast and immediately coat the keel with epoxy. Epoxy for the hull but not so much of a hurry to get it on. In my view having got this far the only sensible thing to do then is Coppercoat as the material cost is only 2-3 times more (under £1k) than one year's worth if conventional AF.

There are many different makes of epoxy, but the one I used was Hempel Hempadur on the advice of the blasting contractor. Just to give you an idea these are the before and after photos (also a Bavaria) where the original Coppercoat failed because of poor preparation. did all the application myself except the first coat which the contractor did. Total cost (2020) about £600. Still good - as is the hull now 6 years.

 

[John w]

Hi There
Great advice knew I had asked the questions in the right place.
Did you copper coat the whole boat or just the keel? If the whole boat can you confirm what the Copper coat cost Please just for a guide as I was given a price of £ 175.00 per foot ( 36foot) for the whole job blasting prep all coatings & then the copper coat which worked out at £ 6300.00 plus the dreaded vat hence wanting to do most of it myself

 

[Tranona]

The boat was Coppercoated from new (Bavaria 33). Delivered straight from the factory to the contractor. Unfortunately the coating on the keel was incompatible with Coppercoat so had to be removed by grinding. This was not effective and after 3 years bits began to fall off as you can see in the before photo. I has a go at patching but next year more appeared so I decided to deal with it myself. The original cost was £4000, but of course there was far less prep than on an existing boat and no costs of taking out the mast to get in the shed. The hull is fine - just a wash once a year and boat is otherwise in the water all year.

It really pays off on an existing boat if you do it yourself outside, but you need good conditions to do it. Blasting and materials for DIY is less than half of your quote. It really only pays having it done professionally if you can then avoid annual haulouts and professional application of AF. If you are DIY then you have difficulty in justifying it financially, although for some aging souls like me avoiding doing the annual paint has a high value! Having said that I am now selling that boat - and Coppercoat helps the sale, but difficult to value and have bought an older and slightly smaller boat. I shall not Coppercoat this as I doubt I will keep it more than 5 years and if the annual paint gets too irksome I shall pay somebody to do it! It also has steel bilge plates which are even worse to coat with epoxy than iron fin keels.

Hope this helps

 

[Concerto]

A lot of boat yards are no longer allowing sand or soda blasting as it leaves so much mess. Try dry ice blasting.

I have chatted to the manager in my boatyard and seen the results. Also the local maintenance guy also recommends Gransden. They will travel all over the country, so if you can get several boats requiring blasting will make it cheaper.