Are barrier coatings bogus?

[AnchorageGuy]

You have a couple of choices.One is to do nothing. Blisters have NEVER caused a boat to sink and once it's in the water, the only ones that can see it is the fish, and they don't care. Paint the bottom and sail it. If you plan to sell it some day you can either address the blisters or sell it at a price that reflects the need for a bottom job. Ytwo, you can fix it but do it right or don't do it at all. The bottom needs to be peeled to the level that eliminates the offending blisters. THEN it needs to dry out to 3% or less moisture. Then apply the barrier coat according to manufacturers instruction. If you don't want to do this, don't waste your time or money, the barrier coat will blister along with possibly some of the fiberglass you left on, and it will only take one season. So those are your choices. Chuck

[laika]

The broker I bought my boat from had posters hanging up in his office expounding the conspiracy of blister repair.

I have found a few blisters a few layers into the laminate and plan on barrier coating next season.

At the very least, just get a kit of Interlux 2000 from WMarine and layer it on. Like $200. Your hull is probably as dry as it will ever be right now and it'd just be like adding another coat or two of paint.

[jgbrown]

Originally Posted by laika

The broker I bought my boat from had posters hanging up in his office expounding the conspiracy of blister repair.

I have found a few blisters a few layers into the laminate and plan on barrier coating next season.

At the very least, just get a kit of Interlux 2000 from WMarine and layer it on. Like $200. Your hull is probably as dry as it will ever be right now and it'd just be like adding another coat or two of paint.

Does he sell a lot of blistery boats? Lol.

[lateral]

I have never been able to get my head around barrier coat laden with solvent being a barrier, so I use neat epoxy 100% solids at at least 500 microns (0.5mm) then barrier
coat. For a polyester boat I would consider using Vinylester then barrier.

The barrier really being a pre- AF paint easy sand prep coat. I would like to see a study on barrier coat efficacy vs 100% solids epoxy. BC is way user friendly than neat epoxy though.

[lancelot9898]

In 1985 when the boat was brand new having never been into the water, I had the yard put a coal tar epoxy barrier coating on the bottom. For the next 25 plus years the boat has been continuously in the water only to be hauled out every 2 or 3 years for a short duration of a week of less for bottom paint. About a year and a half ago the boat was assessed with blisters and after a laminate profile was done it was confirmed to be in the fiberglass rather than just in the paint. Because the boat was going to remain on the hard for a long time frame, I decided that it would be best to fix the problem even though there was no safety issue involved. I had the yard do the peel removing all the gel and even into the choped strand matt. My son and I did some of the minor sanding and then I preped the boat for the epoxy. The first coat was epiglass, a neat epoxy which would penetrate into the remaining CSM. After removing the blush and sanding etc, the numerous barrier coats of 2000e was applied and finally the bottom paint was hot coated to achieve a chemical bond. I put more layers than the recommended number going with 7 rather than the 4 to 5. Eleven gallons of epoxy was used on a 37 ft boat and that should provide adequate protection. I probably would not have done this work if the boat was going to be sailed, but since there was a long time to be on the hard adequate dry time was esencial.

[Badsanta]

Whats your boat worth and how long will you keep it?

[minaret]

Originally Posted by Waterwayguy

You have a couple of choices.One is to do nothing. Blisters have NEVER caused a boat to sink and once it's in the water, the only ones that can see it is the fish, and they don't care. Paint the bottom and sail it. If you plan to sell it some day you can either address the blisters or sell it at a price that reflects the need for a bottom job. Ytwo, you can fix it but do it right or don't do it at all. The bottom needs to be peeled to the level that eliminates the offending blisters. THEN it needs to dry out to 3% or less moisture. Then apply the barrier coat according to manufacturers instruction. If you don't want to do this, don't waste your time or money, the barrier coat will blister along with possibly some of the fiberglass you left on, and it will only take one season. So those are your choices. Chuck

3% lol! Never seen a boat read that low, not even commissioning new ones straight off the truck, never been in the water.

[lateral]

I have a lignomat pin & protimeter aquant. I have never had timber below 8% (tinder kiln dried) but it does depend how you calibrate them. I calibrate for timber type and time of year at ambient (sheltered) Typical.
How do you calibrate for grp?

[minaret]

Originally Posted by lateral

I have a lignomat pin & protimeter aquant. I have never had timber below 8% (tinder kiln dried) but it does depend how you calibrate them. I calibrate for timber type and time of year at ambient (sheltered) Typical.
How do you calibrate for grp?

You don't, you use a meter designed for FRP. I use the GRP-33 from JR Overseas. They do come with a calibration plate, but you basically just take readings off the plate for comparison to remove any discrepancy caused by ambient humidity. I wouldn't use a regular meter, particularly one with a probe.

[AnchorageGuy]

Originally Posted by minaret

3% lol! Never seen a boat read that low, not even commissioning new ones straight off the truck, never been in the water.

We've never done a bottom job unless we get a 3% reading. Perhaps your meters were never calibrated or it was not taken properly. Not sure how a boat out of the factory that has never been in the water reads a high moisture reading. That makes my point. You can't just take a meter and stick it against the hull. The user needs to know how to use a moisture meter properly. I have commissioned hundreds of boat from the factory that came in on trucks. Some manufacturers do test their boats in tanks. If they have done this, the bottom needs to dry out again before that barrier is applied. Chuck

[minaret]

Originally Posted by Waterwayguy

We've never done a bottom job unless we get a 3% reading. Perhaps your meters were never calibrated or it was not taken properly. Not sure how a boat out of the factory that has never been in the water reads a high moisture reading. That makes my point. You can't just take a meter and stick it against the hull. The user needs to know how to use a moisture meter properly. I have commissioned hundreds of boat from the factory that came in on trucks. Some manufacturers do test their boats in tanks. If they have done this, the bottom needs to dry out again before that barrier is applied. Chuck

Hilarious! New boats usually read 7-8%, which is not a high reading at all. What meter are you using? I too have commissioned hundreds of boats. I have also peeled and dried many hundreds of boats. I would guess you are using a cheap meter made for timber. Tell us the model!

[DefinitelyMe]

Barrier coating really won't take that much more time than just bottom-painting. You can do 4 coats of 2000e plus a tie-coat of hard bottom paint in one day. No sanding between layers, just wait until you can touch the paint without it coming off on your finger. On a sunny day you can almost finish one coat and start straight away on the second. After the hard layer put on your ablative coats (i assume you're using ablative paint?). If you use different colour paints it makes the layering easier (alternate grey and white barrier coat, then use a different colour tie coat to your ablative coat. That way when you start to see the hard coat colour coming through you know you haven't got much life left in the ablative).

You might even be able to do the whole thing in one day. Both 2000e and bottom paint dries quickly!

[lateral]

Originally Posted by minaret

You don't, you use a meter designed for FRP. I use the GRP-33 from JR Overseas. They do come with a calibration plate, but you basically just take readings off the plate for comparison to remove any discrepancy caused by ambient humidity. I wouldn't use a regular meter, particularly one with a probe.

Same as for wood.
GE Protimeter BLD5760 Aquant Moisture Measurement System, GE Protimeter BLD 5760 - at Test Equipment Depot

My boat is timber & epoxy. They (meters) belong to my business. (Construction.)
Also- manual sayes it is suitable for GRP, must read the calibration process, I just have never had the occasion
to test grp.
Besides, relativity to a control sample, is the key to moisture radio frequency meters. Units mean squat.

[minaret]

Originally Posted by lateral

Same as for wood.
GE Protimeter BLD5760 Aquant Moisture Measurement System, GE Protimeter BLD 5760 - at Test Equipment Depot

My boat is timber & epoxy. They (meters) belong to my business. (Construction.)
Also- manual sayes it is suitable for GRP, must read the calibration process, I just have never had the occasion
to test grp.
Besides, relativity to a control sample, is the key to moisture radio frequency meters. Units mean squat.

Funny, I test mine against the calibration plate (control sample) regularly and find that conditions mean little to it. It's remarkably accurate. I have had the occasion to test GRP a great many times. I'm on my 5-6th meter. The sensor plates eventually wear off.

[lateral]

Off topic but interesting.
GRP shouldn't vary too much, should it? As in approx.50/50 glass to resin.
Boat to boat, similar layup.
As cedar, to say jarrah, measures different for the same moisture content.
But what I was saying, the scale don't mean much. As in if you benchmark
on something topside that gets the sun & is dry, with same (relative) structure,
then go back where hull is immersed you get the picture what is going on.
Do you not? Just how long are you gonna wait to get it in an acceptable range similar to topside?
My ol hull wasn't rotten but reading 25-35%. Put a bag over it and got it down to 10-14%. It was a little distressed!
Took the bag off and within two days was back at 25%.
Something about the hydroscopecicity of salt.
Re-strip plank with virgin timber.

Pine in NZ, settles at about 15-16% (summer) under cover, from ambient humidity. 16-17 winter.
I just set my meter on this & won't epoxy over anything > 13%.
Anyhow, too late now.