how many coats of Interprotect

[motoryacht lover]

I have a 1995 54 Viking and I am having the existing bottom paint stripped down to the gel coat. One yard says 4 coats of barrier coat (interlux interprotect) the other yard says 3 coats. Do any of you have thoughts on this? Thanks in advance for your response.

 

[Avenger]

What does Interlux say?

 

[Boatsb]

I did a 1987 Viking and it was a mess at the gel coat. Badly blistered so make sure the boat is dry before you start.

The recommendation is the buildup not the number of coats. Either one could be doing it right or wrong.

 

[motoryacht lover]

What does Interlux say?

Good thought. They say 1-5 no matter how you apply it.

 

[motoryacht lover]

I did a 1987 Viking and it was a mess at the gel coat. Badly blistered so make sure the boat is dry before you start.

What do you mean a mess at the gelcoat? you mean the blisters. I have never seen any blisters on my boat. Do you think blisters may come visible once you strip the bottom paint?

The recommendation is the buildup not the number of coats. Either one could be doing it right or wrong.

Do you mind explaining what you mean about the buildup and doing it right or wrong.

Thank you both for your time

 

[captddis]

They want a certain millage. I believe my boat got 6 coats.

 

[Boatsb]

Any paint needs to be a certain millage ( thickness ) to be effective.

Depending on how you apply it and what happens between coats ( sanding ) you will need to build up a dry thickness of at least 10 mils.

 

[Boatsb]

Any paint needs to be a certain millage ( thickness ) to be effective.


Depending on how you apply it and what happens between coats ( sanding ) you will need to build up a dry thickness of at least 10 mils.

 

[saltshaker]

I did this years ago and 2 coats was fine. My bottom was stripped by hand and the gel coat was in very good shape with no blisters. The previous owner did my Hatt right before I bought it. Bottom was stripped due to paint build up. They applied 3 coats and said bottom had no blisters. I think the number of coats required also depends on what condition the bottom is in. If you need to do a lot of filling and fairing then maybe more coats will be needed. For best results you do need to achieve a certain millage. I think this is more crucial if the bottom has been opened up. I would also think that more is better here. This way if the bottom needs to be stripped again, you don't have to worry about damaging the barrier coat.

 

[Avenger]

Yep, the paint manufacturer specifies a certain "mil" thickness. The number of coats is irrelevant, it's the end result of the application that you're interested in. I would stronlgy recommend that you take the word of the people who make the paint, and not the monkeys with the rollers as to how much barrier coat you require.

Directly from Interlux's Pro page:

For fiberglass and most metals, apply enough Interprotect 3000/3001 to reach Dry Film Thickness of 10 mils. This usually
takes 3-4 coats but the amount of paint is more important than the number of coats.

This is the link to the complete datasheet from Interlux:

http://www.yachtpaint.com/MPYACMDatasheets/Interprotect_3000_3001+eng-usa+A4+Y+20100621.pdf

Encarta defines "mil" as one thousandth of an inch. So if we're going to be scientific the yard should be able to tell from experience (and the use of a vernier caliper) how many coats they need to achieve a given thickness. Unforutunately most yards use the T.L.A.R. method, meaning: That Looks About Right. So unless you bring measuring instruments, you're on your own.

BTW, if you go to the yard with all this information and demand that they measure it appropriately you will probably be told to find another yard.

 

[motoryacht lover]

Thank you all for your help

 

[krush]

Yup. The important thing is to ensure you get the right thickness, or "mills". Few painters actually ensure this is achieved. To properly measure it requires some special tools and you must read and follow the instruction manual. Ultrasonic thickness measuring devices are the norm now.

When I was painting GigaWatt (sold it before going back to school) I hired somebody to paint the topside. He's painted for 25 years and has a successful business but didn't do it right. I bought the UT gauge and read some manuals and painted the sides myself--much better.

 

[Maynard Rupp]

Our 36 needed 7 coats to achieve about 12 mills. 1 mill = .001" so I measured from the paint to the bare hull after we moved the stands to paint that area. I just used a depth micrometer. I read .012 which is just a bit more than they ask for. This material has now been on there for 6 years and is just fine with no blisters. The last 4 have been in Miami salt water.