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Old 31-07-2014, 08:18   #1
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DIY Osmosis Treatment in the Tropics - Advice Please.

Hi,

I sailed my polyester/foam sandwich cat from the UK to the Caribbean last winter, and noticed blisters on the hull when I arrived. That was quite a disappointment since I'd had it out of the water for a year previously, doing other work on it. I'd measured the hull with a moisture meter and a drilled a few experimental holes in the dampest places, and I decided then (with some well qualified advice) not to strip the gel coat off at the time (there was no blistering at all and little indication of dampness on the meter). I just applied 4 coats of epoxy for the purpose of osmosis prevention, followed by Coppercoat.

But it didn't work. I have since heard that this is quite a common occurrence when a boat is taken from cold climates to the tropics.

I had the boat lifted out the water in Antigua in March, and I stripped the gel coat off with a gel stripper (I had to import one from the US, and sold it on to the yard).

I intend to return to Antigua in November to give the underwater sections a new coat of glass and epoxy, a couple of coats of barrier coat, and then anti-foul.

The boat is stored outdoors. I have asked the yard to wash the boat down three times now, to wash away solutes as the hull dries out. I'm hoping this washing down, and long exposure to wind and rain and sun will result in a hull dry enough to epoxy. I hope this isn't wishful thinking, that this treatment will be sufficient, as there aren't many facilities there to do much more than that, and everything there is pretty expensive.

A few questions then:

1. Is it wishful thinking hoping the hull will be dry enough to epoxy when I get back in November?

2. What kind of epoxy would you recommend for working in the tropics? I'll move the boat into a very large shed for the epoxying, so I won't have trouble with direct sun. I'd like some really slow curing stuff, so that hopefully I can get the glass on then go over it with thickened epoxy to fill the weave, without it curing and needing sanding first. Then a light sand and on to filling and fairing. Is such a slow curing epoxy available? - I'm going to ship out materials from the UK to Antigua in advance.

3. What thickness of glass should I use? I've stripped the gel coat off, and in places some of the chopped strand mat between the gel coat and the woven glass too. I don't think removing or damaging the chopped stand mat compromises the strength of the layup, so perhaps the purpose new layer of glass is best described as providing abrasion resistance, and ensuring a thick and even coating.

I've read an awful lot about osmosis now, and am familiar with all the standard treatments. However, I have read that allowing the boat to dry outdoors, with an occasional rinse down, would do the trick. I do hope this is the case - I need to be pragmatic, with limited options in this situation.

Any advice on this would be most welcome.

Thanks,

John
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Old 31-07-2014, 09:20   #2
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

Quote:
Originally Posted by pir8ped View Post
Hi,

I sailed my polyester/foam sandwich cat from the UK to the Caribbean last winter, and noticed blisters on the hull when I arrived. That was quite a disappointment since I'd had it out of the water for a year previously, doing other work on it. I'd measured the hull with a moisture meter and a drilled a few experimental holes in the dampest places, and I decided then (with some well qualified advice) not to strip the gel coat off at the time (there was no blistering at all and little indication of dampness on the meter). I just applied 4 coats of epoxy for the purpose of osmosis prevention, followed by Coppercoat.

But it didn't work. I have since heard that this is quite a common occurrence when a boat is taken from cold climates to the tropics.

I had the boat lifted out the water in Antigua in March, and I stripped the gel coat off with a gel stripper (I had to import one from the US, and sold it on to the yard).

I intend to return to Antigua in November to give the underwater sections a new coat of glass and epoxy, a couple of coats of barrier coat, and then anti-foul.

The boat is stored outdoors. I have asked the yard to wash the boat down three times now, to wash away solutes as the hull dries out. I'm hoping this washing down, and long exposure to wind and rain and sun will result in a hull dry enough to epoxy. I hope this isn't wishful thinking, that this treatment will be sufficient, as there aren't many facilities there to do much more than that, and everything there is pretty expensive.

A few questions then:

1. Is it wishful thinking hoping the hull will be dry enough to epoxy when I get back in November?

2. What kind of epoxy would you recommend for working in the tropics? I'll move the boat into a very large shed for the epoxying, so I won't have trouble with direct sun. I'd like some really slow curing stuff, so that hopefully I can get the glass on then go over it with thickened epoxy to fill the weave, without it curing and needing sanding first. Then a light sand and on to filling and fairing. Is such a slow curing epoxy available? - I'm going to ship out materials from the UK to Antigua in advance.

3. What thickness of glass should I use? I've stripped the gel coat off, and in places some of the chopped strand mat between the gel coat and the woven glass too. I don't think removing or damaging the chopped stand mat compromises the strength of the layup, so perhaps the purpose new layer of glass is best described as providing abrasion resistance, and ensuring a thick and even coating.

I've read an awful lot about osmosis now, and am familiar with all the standard treatments. However, I have read that allowing the boat to dry outdoors, with an occasional rinse down, would do the trick. I do hope this is the case - I need to be pragmatic, with limited options in this situation.

Any advice on this would be most welcome.

Thanks,

John

Can you ask the yard to take occasional meter readings for you? I usually do monthly readings. This is necessary because most boats will initially dry fairly rapidly, followed by much slower drying. This means after 3-4 months you often hit a point of diminishing return. It's worth taking readings, I wouldn't coat a boat that hasn't been metered anyhow. I write the readings on the hull every couple of feet, different color sharpie for each month. This way you can see at a glance how a bottom is drying.
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Old 31-07-2014, 09:40   #3
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

Minaret gives good advice, otherwise your plan is sound.
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Old 31-07-2014, 09:51   #4
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

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Minaret gives good advice
I read these threads, to hear what his advice is.
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Old 31-07-2014, 10:23   #5
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

I just did the full treatment on mine, letting her dry out in North Carolina from Sept to Mar with regular washdowns. She was dry and ready to go by the time I started putting things back together in March.

Not being the pro that Minaret is, my guess is that with regular washdowns and a full summer in the Carib you really ought to be good to go. Free thoughts here, though

I bought all my glass online from fiberglast.com and was happy with their service and product. I used West System epoxy throughout (which ended up costing more than the glass itself!). They have an extra slow cure hardener (#209). My guess is that because you didn't go through all the CSM that you can use as light of a cloth as you want to, if you want to at all. It's a lot of work!!

I learned a lot from studying Minaret's refit page: Nauticat 52 Refit

FWIW, I also documented my DIY refit here: Hull work and barrier coating

Ryan
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Old 31-07-2014, 20:50   #6
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

You can use infrared heaters to speed up the drying process. Btw it's better to remove the Chopped strand mat and apply roven matting. If you like a better finish and reduce on filling, use what's called Peelply over the wet laminate, it helps to fill the laminate and keeps the resin in place. After the resin is dry the Peelply is removed.
Peelply might come under a different name in your country, it's a fabric and won't stick to the resin. Keeps the resin in place.

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Old 01-08-2014, 00:36   #7
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

Minaret: The yard doesn't have a moisture meter, and the place is too disorganised for them to check the levels regularly. They don't do anything regularly - they don't even collect my fees, though they have my credit card details!

laika - thanks for those links. Excellent, and thanks for documenting your own work so thoroughly. As for West 209, I looked at their data and got:

25 degrees 50/70 mins pot life
35 degrees 20/30 mins pot life

I'll be working at around 30 degrees C, so that doesn't give me much time. I'll be working alone most likely. I'll have a look round for other manufacturers, but might have to go with this.

Icarus: I found the source of information I used when I decided leaving the boat in the open and just rinsing down should be sufficient: http://www.passionforpaint.co.uk/pdf/osmosis3.pdf
This guy reckons heat lamps are pretty much a waste of time, and given that the boat is in the tropics, in the trade winds, and will be left exposed for 6 months or so, I don't think getting water out of the laminate will be an issue (there was very little water - there was a slight dampness around blisters as I peeled away the gel coat, which I could see evaporating in the breeze). I don't want to use peel ply - I was hoping to find an epoxy that was slow enough that I'd have time to stick the glass on and then fill the weave. This would reduce the sanding I'll need to do.
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Old 01-08-2014, 00:55   #8
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

I'd be worried most of the humidity in Antiqua Weather Averages for Antigua, Antigua
Can't see how deasent drying can happen in those circumstances. Anyway IMO better to cover the boat with somekind of tarp for a week or so with dehumidifier inside the cover. Same goes with the GF and any other materials (fillers etc), it needs to be as dry as possible aswell as when the actual work is done. Thou got to admit I haven't any experience in the tropics with this kind of work.

ps. You can increas the working time somewhat by storing the epoxy in a cooler place. Pump the patch you need, not much at a time, it starts warming when you spread it on the surface and stir another after that..
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Old 01-08-2014, 03:15   #9
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

My thought is similar to TeddyD - I am wondering if bagging in heavy black plastic would help "sweat" the boat. Seal it with some "room" around the hull and a drain tube at the bottom.

Here is humid Singapore my rudder sat for almost a year with drain holes in it and I know for sure there is still water in it. Sigh... Next year.
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Old 01-08-2014, 14:03   #10
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

Quote:
Originally Posted by pir8ped View Post
As for West 209, I looked at their data and got:

25 degrees 50/70 mins pot life
35 degrees 20/30 mins pot life

I'll be working at around 30 degrees C, so that doesn't give me much time. I'll be working alone most likely. I'll have a look round for other manufacturers, but might have to go with this.
That should give you plenty of pot life. I was working in up to 30C in North Carolina with the west 206 and it was still plenty of time. Certain times it would have been nice to use the 209.

The cure time once on the hull is much longer than pot life, and as long as you are working with the epoxy already on the hull while its still tacky you're good to go. I'd guess youd have a number of hours to work on a given section in 30C with the 209. If you're working by yourself you're just gonna have to do smaller sections.

Keep the depth of the epoxy in the mixing pot to a minimal. The more you mix at a time the faster it will cure or even start to smoke and runaway from you. For instance, a thin coat of epoxy on the hull will take hours to fully cure, but a 6' cup full of freshly-mixed epoxy can smoke and cure in minutes, almost starting a fire in the process

Also, don't underestimate the enormity of the project re: laying up glass by yourself over an entire hull! And afterwards you still have to sand, fill, fair, sand, barrier coat...
If you think the hull is strong enough as is, I would advise just hitting certain areas like the stem and bottom of the keel with glass to provide a little extra impact strength / abrasion resistance.

Again, I'm not a pro, but I just got done with this job myself and I was really ready to be done with it by the time it was finished! That said, I would do it again if I had to.
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Old 01-08-2014, 15:08   #11
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

You are right about costs in Antigua. I spent most of 8 years based out of there, and much was expensive. The one thing that was reasonable was the cost of day laborers. (this has been 20 years now, so things may be different) that work on boats all of the time. Some were skilled, some were just grunt labor, but much cheaper than yard rates. Ask the yard if they allow you to hire your own laborers? You are looking at a big job, in intense heat, so having help might be a very good thing. I have no idea what the day rate for a shed that will fit your boat is, but extra labor(less time in shed) might make the labor cost seem like a lot less. Which yard are you in?? Best of luck. ______Grant.
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Old 01-08-2014, 15:34   #12
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

with west system currently here in the uk with 25c temps i'm finding working with more than 350gms thickend 105 and a slow206 hardner is pushing it for laminating,probably if justroller coating and squeegeeing 500gms would be the biggest mix you could work with in those temps.
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Old 01-08-2014, 17:44   #13
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

We do osmosis repairs frequently, so far with good results. Although we have hot and dry weather here in Australia the drying process is lengthy as the substrate might be dry on surface only, that is the reason why we use infrared heaters. Infrared heaters heat up the core, not just the surface. Reglassing is an underwater body is not an one man operation and difficult at the best of times. Preimpregnated matting is the go. Why you don't want to use Peelply ply ? It is cheap and effective and keeps the resin in place and helps to fill the weave. By the sounds of it you haven't worked with resins on large overhead areas, it's a challenge.




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Old 01-08-2014, 18:10   #14
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

In Antigua, labor rates for ship work are cheaper until October. Right now very little is going on. come November prices go up and the good people can be all busy.


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Old 01-08-2014, 19:43   #15
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Re: DIY Osmosis Treatment in the Tropics - Advice Please.

Just going to throw in another opinion here.
West is great for repairs and laminating. It takes too much thickness for it to be a blister barrier coat.
I'd finish your project with a few coats of Interprotect 2000.


Interlux Interprotect 2000E Osmosis Prevention - MFG#2000/2001G

"Interprotect® 2000E with Microplates® is a unique two-part epoxy coating developed to protect fiberglass hulls from water absorption, which can lead to osmotic blistering. Microplates® create an overlapping barrier to help stop water migration through the coating. The Interprotect® system is the system of choice for repairing gelcoat that has already been damaged by osmotic blistering."
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