Bottom paint question

[belybuster]

Hi All,  I use my CP-23 in fresh water and am planning on hauling it and painting the bottom.  It currently has Pettit, Neptune - 5, applied by the previous owners marina.  I'm taking it home and thinking of using Pettit Neptune HRT, which is water based.  The directions say to sand the old paint but I don't really want to get that stuff all over me and the barn.  What do you all think?

Thanks very much for the input!

[Tim Gardner]

Well, Buster, do you know if your 23 has a barrier coat of epoxy under your current bottom paint?  If not, there is no better time to check than now.  If you plan to leave your boat in fresh water, the barrier coat prevents blistering.

Just sayin'

TG

[wes]

If the question is whether you really have to do the scuff sanding step, I'd say yes you do. Assuming you've already checked Pettit's instructions and verified it's ok to apply the HRT over the Neptune 5, then you need a clean, roughed-up surface for the new coat to adhere to. A light sanding with 80 grit on a random orbit sander is pretty quick and easy. Use a shop vac attachment on the sander and a HEPA style (yellow) bag in the vac and you'll throw off very little dust. You should still be careful to wear a respirator, gloves and a tyvek coverall. Can't be too careful with your body.

Wes

[belybuster]

Thanks Tim.  I'll check for blisters and check into epoxy undercoaters.
Thanks Wes.  Sanding, I guess, does make sense since that's what they say to do.  Your recommendations of a sander with dust collection and personal protection is definitely the way to do it and I agree that when you attack it like that, it should go pretty smooth and easy.  I'll do it out in the open.  I'm glad no one said just let the marina do it because the previous owner's bill for haul out and bottom paint was  $1,100.00.  That's at least a months worth of rum.

[philb Junkie19]

Yes, get it out of the barn. For light sanding I have used a swivel sanding pad mounted on a pole, what you might use for sanding ceiling drywall seams, not perfect but keeps me a little farther from the dust.

[brackish]

When I built my epoxy composite skiff a few years back, I made a number of fairing sanding boards.  Simply a piece of thin, flexible plywood with handles on both ends that will flex to a curved surface.  Made them various lengths up to 40" long.  Found that in addition to fairing, they were great for scuff sanding the bottom of the 23 because they would flex to the curve of the hull.  I bought rolls of adhesive backed sanding paper to stick on them in various grits, 80 was perfect for the rough up required for a new coat of bottom paint. You can cover a lot of ground with them quickly and have much less airborne dust then with power methods.  You pull them along the length of the hull at a slight angle as you move them side to side in the direction of the board. Surface will hold paint fine but not be perfectly smooth.  If I wanted that I'd have it shot blasted with mild media, sanded and then spray the coating.  But that tenth of a knot I lose to drag from that ever so slightly rough surface is not worth considering to this non racing sailor.

[HeaveToo]

If you don't want to get stuff every where put something down under the boat before you sand.  To keep it from being airborne wet sand it.  You can buy sanding blocks that are prefect for this and just dip them in water as you go along and wet the bottom.  Some marinas require this these days.

Also wear a mask and old clothes you intend to get rid of anyway.

There is no way around it, doing the bottom is a nasty job.  It was always my least favorite.  If I had a bigger budget, I would have paid someone to do it but, then again, do I trust them to do a good job.