CPES - How dry is dry

[gimmellsmom]

I'm trying to play out the repainting & antifouling of our H28 over the fall/winter layup.

The bottom/anti-fouling, I was planning on sanding down the planks as its mostly sloughed off and using a wire brush on the keel.

The instructions for CPES (cold) are:

"Now, with the wood clean and dry..."

How dry is dry? Do I need to wait until spring to start after its dried up for 3-4 months or does dry mean - not wet fresh from haulout?

Has anyone found any issues with Pettit Vivid over CPES treated wood?

FINALLY (okay, I'm sure I'll have more questions...) is there any concern with prepping for CPES now, while we still have reasonable weather, by Canadian standards but applying it in the spring? Everything i read says it's 90% preparation / 10% paint time wise. We have a potentially short window between suitable for paint weather and launch. If I can knock off some prep work now it will save me from being a crazed bleary eyed painting maniac in April. :eek:

Thank you in advance,
Michelle

[Thorne]

Can we assume you are using Smith's CPES (they are the only ones I know with cold and warm weather formulas)? You can call Smiths in Richmond CA and ask them...Steve Smith often takes calls.
http://www.smithandcompany.org/

I think you want to use it on dry wood for the best penetration. Why not let the wood dry out as much and as long as possible, then coat with CPES? My understanding is that CPES penetrates wood along the fibers in the same way that water penetrates -=- but if the wood is full of water, can't see how that would allow the CPES maximum penetration.

To answer the prep question, unless the boat is exposed to UV, can't see why it would hurt to apply the first coatings of CPES months before painting. But in most cases the final coating of CPES should be about a day before the first coating of paint, aka "hot-coating".

[Gary E]

My understanding is that CPES penetrates wood along the fibers in the same way that water penetrates -=- but if the wood is full of water, can't see how that would allow the CPES maximum penetration.


If the S in CPES stands for SEALER and the wood actually ends up SEALED... how is the "normal" dried out wood boat with it's now open seams going to soak up water and swell so it does not leak? or is this not something that the coolaid drinking CPES groupies consider?

[kc8pql]

Why do you want to use Cpes ?

[pcford]

A you might gather CPES is a topic which there is some divergence of opinion.

I don't think it is a miracle product; some here do. I do think it is a decent sealer.

Your boat after a few months out of the water is likely dry enough to apply the stuff.

As noted above Steve Smith is a very helpful guy on the phone.

[outofthenorm]

Can't advise you on the CPES, Michelle, other than to say that the drier the wood, the better it penetrates. But CPES or not, you'll need to do something for sure. It's a Very Bad Idea to the leave the hull bare or nearly bare over the winter. The wind and cold will seriously dry it out. I've always coated with something in the Fall, depending on the state of the bottom at haulout - I've used boiled linseed oil, red lead paint and, on one occasion, even an old can of antifouling paint that I knew would have to come off in the Spring - anything to protect the hull from a Toronto Winter.

- Norm

[gimmellsmom]

Why drink the kool-aid, well the bottom paint needs to be redone, totally gone in some spots. SO my logic, thinking, whatever, is that if I'm going to have to go through the trouble to get right down to the wood to get rid of the current Bottomkote (which per my local interlux rep cannot be painted over with anything BUT itself) I might as well seal it while I'm at it. Are there rot issues - not yet. But my the CPES was more of a preventative measure.

We've covered her now - biggest tarp known to man - nothing near as fancy as Norm's though. So she's out of the wind & snow to some degree, but I understand the wind is pretty harsh at our club coming off the lake. Next year I think we'll have to get her squeezed between a couple of the monster power boats for better shelter.

[soba]

If the S in CPES stands for SEALER and the wood actually ends up SEALED... how is the "normal" dried out wood boat with it's now open seams going to soak up water and swell so it does not leak? or is this not something that the coolaid drinking CPES groupies consider?

All the lit states that the wood can still shrink and expand and "take up" after the application of CPES.

If I understand correctly, the sealer part of CPES seals the wood in a way different from the conventional definition of "sealing." That is, rather than sealing the inside of the wood away using a barrier coat, it coats or saturates or hardens the walls of the wood cells. I suppose the cells still act the same way, and as it is not a rigid product , they can swell and shrink.

I'm not a CPES user, or hater, or lover, but it seems like an interesting product. Has anyone used their (incredibly expensive) non-sealer epoxy?

[redbopeep]

We've used CPES on lots of "dry" wood (8%-14% MC) and have also used it on "green" wood--our 3"-4" thick tamarack knees--successfully. On the knees, we were trying to keep the moisture "in" and have the knees not shrink up and crack. We installed them in the spring of 2007 and they've been drying out but not really moving around and cracking. So, it works in that way.

Check the moisture content of the wood; if it's in a reasonable range--go ahead and use the CPES.

[BrianM]

I just hauled and pressure washed my boat this afternoon. Last bottom job was 2 years ago. I applied some Navy surplus Epoxy to the bottom after she'd been out 3 days in October (warm dry weather). No special attention was given to "drying" the bare wood out. Paint was tenaciously attached to all the areas I primed with Epoxy, and chipping off anywhere bottom paint was applied to bare wood only.

Lesson learned and which is applicable to your situation.. epoxy seems to have huge "tolerance" for moisture in wood and is a great primer for Bottom Paint.

[TonyH]

I spent a bit of time with CPES (and Steve Smith) as for fun a few years ago I ran a little business importing it into Australia. So I had lots of dialogue with Steve S about how it works and what its limitations are.

CPES is fairly tolerant of at least a moderate amount of moisture in the wood, although applying it to wet wood isn't a good idea. If the wood feels dry to touch then CPES should work OK. The dryer the wood is, the further the CPES will penetrate, all other things being equal. Of course, it doesn't penetrate all that far into sound solid wood, especially if it is a reasonably dense type of wood (and a dense hardwood in particular). What it does do is run into all the cracks, checks, splits, holes, fastening penetrations, joints etc etc where water would otherwise go. So if there is still water deep in these then the CPES won't be as effective at keeping water out of these in future.

CPES is a sealer, in that it makes the wood water-resistant, but doesn't make it water-proof. It slows down the rate at which water enters or leaves the wood, so CPES-treated wood will take up water slower than unsealed wood. This means that a dried out boat treated with CPES will "take-up" slower than an untreated boat, which may be seen as a bad thing if water is pouring in through all the seams:D! On the other hand, slowing down the shrink-swell cycles is good for the boat in the long run because it decreases the stresses in the wood (and thus in the structure) that rapid shrinking and swelling can cause. Once treated and "taken-up", it will also dry out slower next time. In the long run I think that's a good thing.

Other reasons to use CPES under the bottom coat would include:

to improve adhesion of the coating to the wood (the "hot coat" referred to by Thorne is important to maximise this effect);
to make the surface of the wood less palatable to wood-boring fauna like teredo, in case they get through a crack in the bottom paint.

[MiddleAgesMan]

I used CPES on my GIS and seem to recall the instructions said to give it 2 or 3 days before overcoating it. Epoxy resin was my first overcoat so I waited the full 3 days. I knew it was still giving off solvents during this time because I could smell it whenever I went into the boat shop. After 3 days the smell was gone.

I mention this because of the recommendations above to hot coat it. Is that really an option according to Smith's instructions?

[Thorne]

Yep. You are supposed to let all other coats completely cure, which depends on the mix (cold or warm weather formula) and temps.

The **final coat** of CPES should then be hot-coated with the first coat of whatever goes on top, epoxy, varnish or paint. Again, how long you wait before hot-coating depends on the formula and temps -- in warm weather I'll wait 4-8 hours, in cold 12-24.

I'm certainly no expert, but the only time I'd be wary of hot-coating would be if a clear coating is desired (i.e. you want to see the wood when done) and epoxy is being put over CPES. If the weather is warm you want to make sure that most of the solvents have come out of the CPES before the first coat of epoxy, so as to minimize bubbles. What folks here have said is that you should try to do this as the temps cool, so that gas / air / solvents are pulled into the wood, not out of it into the epoxy layer.

For any specifics it is always best to contact the manufacturer. Steve or his staff are always ready to answer technical questions about their products -- one of the best things about doing business with a small company!

[gimmellsmom]

Okay, dumb question number one... why would you apply epoxy over CPES - or do you mean just for repair purposes?
And how far does this stuff go really, I've spoken to their Cdn. rep and she figures 25-50 sq. ft per quart. But I assume it would be dependant on the wood? If one has fairly solid/rot free wood, would 4 quarts do me? I've got an LWL of approx 23' x 4' draft (minus keel). She only has 6 quarts of cold CPES left. But if I do some in the fall, can I put regular CPES overtop in the spring (forgot to ask her that one)?

[jclays]

Yep. You are supposed to let all other coats completely cure, which depends on the mix (cold or warm weather formula) and temps.

The **final coat** of CPES should then be hot-coated with the first coat of whatever goes on top, epoxy, varnish or paint. Again, how long you wait before hot-coating depends on the formula and temps -- in warm weather I'll wait 4-8 hours, in cold 12-24.

I'm certainly no expert, but the only time I'd be wary of hot-coating would be if a clear coating is desired (i.e. you want to see the wood when done) and epoxy is being put over CPES. If the weather is warm you want to make sure that most of the solvents have come out of the CPES before the first coat of epoxy, so as to minimize bubbles. What folks here have said is that you should try to do this as the temps cool, so that gas / air / solvents are pulled into the wood, not out of it into the epoxy layer.

For any specifics it is always best to contact the manufacturer. Steve or his staff are always ready to answer technical questions about their products -- one of the best things about doing business with a small company!

Would you sand before painting.

[Thorne]

Sand CPES before painting? No -- remember you're supposed to be hot-coating, so the finish might feel dry but would not be fully cured.

If the surface is uneven after several layers of CPES (runs or holidays), I'd sand and do a final thin CPES recoat for the hot-coating with paint.

Again, always best to contact the manufacturers for this sort of info!