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Bottom Blacking

February half term is a busy week or two for us at Thorn Marine.

For those of you who don’t know we have a day boat and a small boat we have had for a few years that we have never done any thing with.

Half term and the week after is our time to black the bottom and re paint the sides and roof, I will explain more about the repainting in my next post.

During the two weeks I also had a customers boat to black as well so that is 1 x 36′ 1 x 30′ and 1 x 40′, Whilst doing this I got to thinking, nobody ever discusses blacking and what it involves. I decided to have a think about what questions you should ask when getting you bottom blacked.

Blacking before
Jet washed and wire brushed all the loose stuff off with a grinder

1. What surface preparation do you need to do?
This can range from a quick jet wash through wire brushing or scabbling to grit blasting. I know of some companies who just give the hull a quick jet wash to get rid of the weed growth and then black the boat, they do nothing about any rust build up on the surface.

2. If your previous coats of bitumen are stuck on well do you need to remove them?

3. What has the boat been painted with previously?
Comastic, Bitumen, epoxy.
This effects what you can use and what surface prep needs to be done epoxy needs to go on clean steel, comastic cannot be put on top of bitumen.

4. What product are you using?
Are they using a product specifically designed for use on boats, under the water or just a roofing product that is designed to get wet occasionally and then dry out. Rylard paints have two products that are designed to be used together one that works in to all the marks etc on the hull and a much thicker one to give film thickness.

5. How many coats are being applied and how thick are they?
The Rylard paint system is 2-3 coats, International recommend between 2 and 5 coats, depending on application method.

6. What drying times and launch times are used?
Most bitumen products require 8-24 hours between coats and 24-48 hours before submersion.

7. What else will be checked when blacking?
Anodes, are they in the right place how much longer will they last.
Prop condition, bits missing or bent.
Stern gear, is there any movement/excessive play.
Rudder condition, bolts corded etc.
General hull condition, pits, corrosion etc.
Welds, are the rubbing straights continuously welded, etc.

8. Do you paint inside the weed hatch/cover?
Some people don’t remove the weed hatch. The tape may need to be replaced as well.

9. A great one to start and argument is does the bottom plate get a coat!

Let me make one thing clear this is not a guide to painting your hull/getting it painted. I am not a surveyor or have any steel/chemistry qualifications, these are just the thoughts of a guy who has been in the industry for about 20 years and have blacked a few boats over the years. Some have been great some have been so badly blacked before they will need the sides over plating.

All I want this to do is to make you think about how your boat is blacked. Remember a boat without a hull is not a boat! You may not see it but the bit in the water it is the most important bit!

Blacking finished
3 Coats of Rylards Blacking Premium Protection, Rytex and then a final coat of Premium Protection.