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-   -   Bottom Blasting (http://www.cruisersforum.com/forums/f55/bottom-blasting-79207.html)

tsl 27-03-2012 14:09

Bottom Blasting
 
I'm about to blast many many layers of bottom paint off my project sailboat. I took a scraper to it to see what I was up against.
I quickly popped off 6 to 8 layers of blue bottom paint leaving a bronze or brown layer that apeerded to be 3 or 4 mils thick (2 or 3 roller coats). The blue did not adhere well to the brown layer.
Under that was white surfacing or fairing material. I went no futher.

The boat was sailed for year in the DC area. What do you think I have here?

tager 27-03-2012 14:16

Re: Bottom blasting
 
A boat sitting in the yard in need of a bottom job!

daddle 27-03-2012 14:23

Re: Bottom blasting
 
What you have there is ... another reason to use modern ablative paints ?

tsl 27-03-2012 14:35

Re: Bottom blasting
 
so how far down do I blast? It looks like this boat had major bottom job done.

Do I remove the brown layer and work from the white or start at the brown?
do I use barrier coating?

minaret 27-03-2012 16:45

Re: Bottom blasting
 
Take it down to the white, that is almost certainly the original gelcoat. Then apply 5-6 coats of 2000e and 2-3 coats of the bottom paint of your choice. Make sure the hull is dry before barrier coating or you'll be sealing the saturation in instead of out!

cburger 27-03-2012 16:50

Re: Bottom blasting
 
When you say blast what are your referring to?

LeaseOnLife 27-03-2012 16:56

Re: Bottom blasting
 
Quote:

Originally Posted by tsl (Post 917476)
.....leaving a bronze or brown layer that apeared to be 3 or 4 mils thick (2 or 3 roller coats). The blue did not adhere well to the brown layer.
Under that was white surfacing or fairing material. I went no further.

The bronze layer could be VC17, slick stuff, but only for fresh water. If it comes off with alcohol, or E-85 fuel, it probably is VC17. Nothing really sticks to it. Take minaret's advice, sand/blast/strip all the way down, build it up with barrier coat, then bottom paint. Document it, lots of pictures, in case of selling the boat.

Dirk

minaret 27-03-2012 17:22

Re: Bottom blasting
 
Quote:

Originally Posted by LeaseOnLife (Post 917584)
Document it, lots of pictures, in case of selling the boat.

Dirk



Also excellent advice. I don't see this done in the yard anywhere near often enough. I myself often take pictures and give them to clients for their records, they always appreciate it. Visually you cant tell the difference between a well done bottom job and a crappy one, but one will last and the other won't. It's nice to have the proof. My pictures of barrier coating jobs always include pics of the stack of empty buckets to document the number of gallons applied. This proves the necessary millage was applied and not just a couple of coats.

bobconnie 27-03-2012 17:32

Re: Bottom blasting
 
:confused:I hope you are talking about soda blasting, not sand blasting!! sand can do more damage then a grinder in the hands of a Non Expert !! Just saying be careful!!

tsl 27-03-2012 19:40

Re: Bottom Blasting
 
Great help!!! Yes, soda blasting on the fiberglass and glass shards (not beads) on the iron keel.
Will test Brown layer starting with alcohol. Will take pictures. Boat is an 1983 O'day 39

I will go down until I get glass and return tomorrow with results and pictures, Thanks so much for the help!!
Any suggestions for iron primer?

minaret 27-03-2012 19:57

Re: Bottom Blasting
 
Quote:

Originally Posted by tsl (Post 917713)
Great help!!! Yes, soda blasting on the fiberglass and glass shards (not beads) on the iron keel.
Will test Brown layer starting with alcohol. Will take pictures. Boat is an 1983 O'day 39

I will go down until I get glass and return tomorrow with results and pictures, Thanks so much for the help!!
Any suggestions for iron primer?


Don't go down until you hit glass if the white layer is the original gel (which it probably is). Stopping there will help you to keep it fair and provide a nice pinhole free surface to apply your barrier coat to. If you burn through the white you will lose all perspective as to fairness and the laminate will probably be fairly porous, potentially requiring extra coats of barrier coat. If you use Interlux 2000e it will work great on your ballast keel as long as it is properly prepped.

daddle 27-03-2012 20:59

Re: Bottom Blasting
 
Grind a shallow test patch the size of a postage stamp. See what is there. Maybe?

GordMay 28-03-2012 06:06

Re: Bottom Blasting
 
You could etch the clean steel keel with a phosphoric acid based primer, such as Ospho, prior to application of a rust-preventive paint, such as Por-15.

tsl 28-03-2012 06:36

Re: Bottom Blasting
 



Are there any issues concerning this type of product?


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minaret 28-03-2012 07:37

Re: Bottom Blasting
 
Quote:

Originally Posted by tsl (Post 917892)


Are there any issues concerning this type of product?


Zinc Rich Galvanize Qt


Item #13243 ZP
In Stock - Ready to Ship Today
Only $34.99


Eastwood's Rich Zinc Galvanize is a fast drying coating that protects steel and ferrous metals exposed to severe corrosive environments. This high performance compound fuses zinc to the metal substrate and provides long-term galvanic protection against corrosion equal to Hot Dip Galvanizing. The finished film contains 95% Zinc that protects the surface, even when penetrated or scratched, as an insoluble Zinc Oxide coating that forms over surface.


Be the first to review this product
Qty: $34.99



The 2000e I suggested as a barrier coat would be dramatically superior to this product. Just ospho it and apply 2000 immediately afterwards. Interlux recommends it as a primer for metals as well as a barrier coat. It really does have superior adhesion and moisture resistance. But you haven't mentioned which barrier you are planning on using yet.


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