[jason3317]

My boat bottom is barrier coated and the anti-fouling is Micron Extra.

Interlux website says 'lightly sand and apply' to renew the anti-fouling. Exactly, what is meant by light sanding?

1. What grit?
2. Can an orbital sander be used, or is hand sanding with a block recommended?

What else do I need to know? The bottom appears to be in good condition (no chips in the paint, etc)....

Btw, I posted the same over to Anything-Sailing, so don't get too mad when you see my question there too.

Jason

 

[JimsCAL]

If the paint surface is in good shape, I wouldn't sand Micron as you will reduce the paint thickness and thus the anti-fouling life. Only sand to smooth the surface. A wipedown with thinner is all you need to do to prepare for a new coat.

 

[sailingdog]

Hand sanding with 80-100 grit should work just fine. You're just roughing the surface to give the new paint something to grip.

 

[sailingfool]

My boat bottom is barrier coated and the anti-fouling is Micron Extra.

Interlux website says 'lightly sand and apply' to renew the anti-fouling. Exactly, what is meant by light sanding?

1. What grit?
2. Can an orbital sander be used, or is hand sanding with a block recommended?

What else do I need to know? The bottom appears to be in good condition (no chips in the paint, etc)....

Btw, I posted the same over to Anything-Sailing, so don't get too mad when you see my question there too.

Jason

I think what you are asking is how to renew the paint prior to launch, without putting a new layer on...? I usually just launch, leave the paint alone, I assume the spray-washing after hauling leaves the bottom ready to go...subject to any necessary touchup, or a periodic additional coat as needed.

 

[jumaggafanny]

Ablative paint releases the compounds to the water over time. I think what you are asking about is sanding to expose new compounds. A light hand sanding with 100 grit to remove just a little of the oxidized surface and expose new "active" surface. It does remove some of the thickness but anti-fouling is a process that must be maintained. Recoating when you wear thru.
Good Luck Jason, try to keep it only partially submerged!

 

[sailingfool]

Ablative paint releases the compounds to the water over time. I think what you are asking about is sanding to expose new compounds. A light hand sanding with 100 grit to remove just a little of the oxidized surface and expose new "active" surface. It does remove some of the thickness but anti-fouling is a process that must be maintained. Recoating when you wear thru.
Good Luck Jason, try to keep it only partially submerged!

Ablative paint IS "the compounds", it releases itself, leaving nothing behind. It does not oxidize. Most non-ablative paints have a binder of some type which builds over time. With ablative, if you pressure-wash the old scum off, it's ready to go. All any sanding does, is remove valuable and expensive paint.

 

[SailChick20]

Just to clarify...are you applying the same paint?
Make sure no compatability issues before applying.

 

[sailingdog]

Just curious—

Are you just trying to renew the paint and splash the boat or are you actually going to be painting the bottom?

 

[CalebD]

What SD said.
No paint? Leave it alone.
Painting a new coat? A light sanding followed by an application of a coat of paint.
Now I am really mad.

 

[jason3317]

Sorry, everyone, I was computerless yesterday. And, I didn't do a good job explaining my question.

I have ablative/self-polishing Micron Extra on the bottom currently. I am painting the bottom with Micron 66 on top of the Extra.

Intexlux compatability chart says 'sand lightly to a tightly adhered surface and paint' - they are compatible paints. So, I don't need to completely remove the old 'Extra' paint..

I'd like to use my random orbital sander to minmize the sanding effort. I am planning to lightly scuff up the paint with the orbital + 80 grit discs by moving quickly across the existing paint surface.

So,I know I need to sand 'lightly'. But, I am not sure what lightly means?

 

[sailingdog]

I wouldn't use an orbital sander for this. There really isn't any need. All you're really going to be doing is scuffing the surface so the new paint has something to grip. A random orbital sander with 80 grit is going to remove a lot of the ablative paint, far more than necessary IMHO.

 

[jason3317]

What's the best practice alternative to the orbital? Hand sand with a block? What grit?

 

[gc1111]

What I do (I have similar bottom paint) is to wet sand with 100 grit paper. I put some on a pole sander like the drywallers use and give everything a once over lightly. I try to get the discolored (and probably oxidized) parts of the top surface off. The goal is to leave as much on as you can while still getting a surface with enough "tooth" to let the next coat bond well. I think a mechanical sander will remove too much.

 

[T37Chef]

Using two or more colors

I put some on a pole sander like the drywallers use and give everything a once over lightly. I think a mechanical sander will remove too much.

Great suggestion for applying an ablative over ablative.

TIP: The new paint should be a different color than what your painting over, this helps to identify when its time to paint again.

See here, my base layer paint over the barrier coat (barrier coat is gray) was black, than two coats of blue.

Black over barrier coat

Blue paint over black (note good looking Ford F150 in the back ground )

All finished (except new boot stripe )

 

[39512]

I think you are better off using the least aggressive sandpaper that you can. I'd bet 120 will do the job. Lightly means thoroughly dulling the surface. If you break through the paint, touch up those spots before flood coating.

 

[harbin2]

T37 Question

Nice photos. I'm getting close to what your photos show and I'm considering the same colors. I have been scraping and sanding all winter and now have all the old (unknown) bottom paint off. I still have a little repair work to do. Then I'll apply 2 coats of Interprotect over the existing (unknown barrier). I'm considering using black Bottomkote Classic as a first coat of bottom paint followed by one or two coats of Micron Extra. What paint products were you using?

 

[tommays]

Interlux wants you to wet sand with 80 grit

 

[T37Chef]

In the photos I used Pettit, ablatives, and if I remember right, it was Trinidad?

Sorry to hear you have been scraping so long, I opted for a blasting job, but then I had blisters and the blasting helped to pop them out

You can see more here: http://www.sailnet.com/forums/gear-maintenance/43729-bottom-repairs.html#post322678

 

[PalmettoSailor]

Interlux wants you to wet sand with 80 grit

Petit says 80 grit also. My boat has ablative over a barrier coat and there is some slight "texture". I plan to use an orbital to smooth that some, as well as create "tooth" for the new paint. I'm trying to get as smooth a bottom as possible using a roll on ablative like the Hydrocoat in using.

 

[harbin2]

Chef - thanks for the link. I have looked at lots of bottom paint posts but had not seen this and it is very well done. Also, great looking boat. I have an Islander 30 but the paint job and boot strips look just like your end result and what I want to keep.

It was a lot of scraping and sanding. I probably shouldn't have done it but was pretty happy with the sander I got. It's a Makita RO, 5" sander. Was very light. Even with that, at times I could hardly hold a phone to my ear after sanding for 4 or 5 hours straight. My marina let me use their Fein vacuum. A fantastic match up. The sander plugged into the vacuum and controlled both units. One problem I had though was that I ended up getting the bottom too smooth. I guess I didn't change paper often enough or maybe the paper was just a poor quality. My local (Chesapeake Bay) Interlux rep tells me I have to re-sand the entire bottom to rough it up (60 grit). Got some Norton 3x for that.

I'm thinking about using Bottomkote Classic for the initial coat. I'll time it to stick to the outer coat of Interprotect. But I'm not sure how or when to apply the ablative (planning on Micron Extra). Do I really need to follow the directions that would have me paint the Bottomkote on and then lightly sand it after it dries to prepare for the Micron?