Bottom paint question

[cdwood]

This off season gonna be lookin to raise the bottom paint line by 2 to 3 inches. Who can help with proper prep tips?

Is all that barrier coating needed? Or can I just clean and paint?

 

[seasick]

Are you asking about prepping the 2 - 3 inch space prior to paint?
If so, the steps for applying bottom paint to a new hull would apply(dewaxing, light sanding etc.)
There is little advantage to barrier coating just the new 2-3 inch space unless the rest of the hull was barrier coated. Even then, it isn't critical.
If you are asking about barrier coating the entire hull then be aware that it is a laborious job ( to do it correctly).
Interlux barrier coat has to be applied in four coats spaced apart in time depending on the temperature and the anti-fouling paint has to be applied within a specific window. If you or the person that is going to do the job, doesn't take the time to do it right, it is a waste of money, the barrier coat won't adhere properly.
The barrier coat will protect against blistering but will not fix existing blisters if you have them.
There is a lot of information on the Interlux paint web site. Note that the actual web address is yachtpaints.com

 

[cdwood]

I'm just looking to eliminate some scum line so it seems like just de-wax, sand and paint?

 

[seasick]

I'm just looking to eliminate some scum line so it seems like just de-wax, sand and paint?

My experience with scum lines is that when you raise the paint line, the scum will form on the paint instead of the unpainted hull. Darker bottom paints will show the stain less.
Bottom paint stops barnacles but not slime/scum. The scum stains if left for a period of time are difficult to remove. It presents a more difficult problem on the paint since the paint, if ablative, also comes off when you scrub especially with stronger cleaners. Often the bottom paint as it gets rubbed around will stain the unpainted area. The only way I have found to keep the scum line under control is to scrub with a soft boat brush and soap regularly. Once the scum dries, it is a bear to get off. If my unpainted water lines gets stained from the scum line, I just live with it until my annual spring hull cleaning/painting

 

[BobP]

The beginning of this (past) season I did what CD is asking about, it worked.

It worked because I use black bottom paint, the brown scum stain doesn't appear same as on white hull. More importantly, since I'm using ablative paint, it's an easy scrub to clear the paint off, do it once a month. Not the case with the gelcoat which needs compounding.

I just sand and paint, no primers. My paint line now is about 2 to 2.5 inches above water line, depending on fuel load.

Never used any epoxy sealers, and never had a blister on a Grady.

I do the same on paint chips when they go to hull.

 

[seasick]

The beginning of this (past) season I did what CD is asking about, it worked.

It worked because I use black bottom paint, the brown scum stain doesn't appear same as on white hull. More importantly, since I'm using ablative paint, it's an easy scrub to clear the paint off, do it once a month. Not the case with the gelcoat which needs compounding.

I just sand and paint, no primers. My paint line now is about 2 to 2.5 inches above water line, depending on fuel load.

Never used any epoxy sealers, and never had a blister on a Grady.

I do the same on paint chips when they go to hull.

All good as stated but be careful about existing wax. I would dewax to be sure all of it is off.

 

[BobP]

Good point.

First I layed the new tape line, then brushed off the sanding dust and hand wiped with denatured alcohol.

Sandpaper paper has the wax on it now !

 

[uncljohn]

I redid my bottom 2 years ago - soda blast, blister repair, barrier coat, ablative paint.

I "cleaned" my waterline by bringing the new white barrier coat a few inches above the waterline, then did the bottom paint to the normal line. Looks good. The one poster is correct about you needing to follow the specific timeline for applications, and it can be a real PITA.

 

[GLGrady20]

I did my entire bottom on my old boat two years ago, just a quick sand job and two coats of paint. It held up perfectly until I sold it this past Summer when I got my Grady.

If you don't want to paint, toilet bowl cleaner works perfectly for those scum lines, but the boat has to be out of the water to clean.

 

[BobP]

Brown stains in gelcoat never cleaned up, had to compound it off.

That's my experience.

 

[seasick]

I did my entire bottom on my old boat two years ago, just a quick sand job and two coats of paint. It held up perfectly until I sold it this past Summer when I got my Grady.

If you don't want to paint, toilet bowl cleaner works perfectly for those scum lines, but the boat has to be out of the water to clean.

Toilet bowl cleaner may contain chlorine and chlorine can turn get coat yellow.

 

[seasick]

Brown stains in gelcoat never cleaned up, had to compound it off.

That's my experience.

Same for me, cleaners wouldn't remove it once it dried.

 

[sluggoe]

i am a novice....how many coats of bottom paint will i need to apply in the spring?

the boat has always been painted every season by marina, but thinking of doing it myself in spring 2010.

boat has seen moderate use during 2009.

-slugg.

 

[seasick]

i am a novice....how many coats of bottom paint will i need to apply in the spring?

the boat has always been painted every season by marina, but thinking of doing it myself in spring 2010.

boat has seen moderate use during 2009.

-slugg.

It depends on the paint and what is currently on the hull. You need to select a paint and then follow the directions. Many ablatives specify two coats minimum. I do the two and may three coat the high wear areas. Since I use a multi season paint, the second season only gets touchups to wear areas, transom recoat and new water lines ( after sanding the scum off)