Advice wanted on bottom paint vs other types / finishes

Painting options, interior and exterior.

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North
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Advice wanted on bottom paint vs other types / finishes

Post by North » Tue Mar 15, 2016 5:55 am

Hi Folks, (I had this posted under my Progess thread in the power boat section but really wanted to check this paint question out separately...hope noone minds the repost!)

I am about halfway done prep and paint work (on bottom only) but have some questions...or a dilema I guess..re: bottom paint.

This 25ft aluminum hull, planing power boat will spend about 4-5 months per year (albeit much less this summer) docked on a tidal river, about 1/2 mile upstream of the salt water bay / Atlantic ocean. Water at the dock is slightly salty but mostly fresh as the river has a good flow rate all year.

I have kept my older 30ft sailboat there for the last 5 years and regardless of bottom paint choice, or some years even only lightly sanding existing bottom paint, the most "growth" I get is some slime which easily pressure washes off after 4 months.

I have followed mfgr's instructions and (after first sanding the hull) have applied 1 coat of Inteprotect 2000E (epoxy primer / barrier coat) and then faired low spots with Interlux's "watertight" brand epoxy filler.
I have a bit more sanding / fairing to do and then I will be ready for a few more coats of I2000E and then bottom paint - but here is my dilema.

The boat is far from finished but I am hoping to get enough done to do some sea trials and have a bit of fun this summer, knowing many items will not be finished till the following winter.
The boat is upside down now, so it is much easier to apply bottom paint now, but that causes some issues as the boat will not be submerged for a few months, and even then, perhaps not for long, if it requires major tweaking..

As I see it I have the following choices:

1. As originally planned, while final coat of I2000E is still tacky, apply
first coat of Trilux II bottom paint, followed by subsequent coat(s).
Pro - don't have to sand I2000E to apply this bottom paint.
Cons - Mfg says boat must be submerged within 90 days or bottom paint will not be effective- this would be hard to do... I could hold off on last coat of I2000E and bottom paint till it's close to ready for water, but this means painting those final 2-3 coats while boat is then right side up - much more difficult
- Trilux II is a one season paint so no good the following year, need to re-apply - very expensive for only limited use this year.Or, just ackowledge that it will be a finish coat but not antifoul well, so will need pressure washing....
- it is not reputed to be good fighting slime, which is what I get the most....


2. Use a "non" bottom paint such as VC performance epoxy instead of bottom paint.
Pro - less expensive. would not reapply year to year
- can do while upside down - much easier
Con - no antifouling, pressure wash when needed.
- need to cure and sand the I2000E before applying


3. Leave last coat of I2000E (primer/ barrier coat) as final coat (nothing on top if it).
Pros - do while upside down. less expensive, no repeat each year.
Cons- no antifouling, need to pressure wash as needed
- would texture of I2000E allow growth faster than "slicker" paint?
- mfgr tech support (who was very helpful and patient) saif that mya be ok for a few trials but it really isn't a final coat... But, is there any harm in it - it is an epoxy barrier coat...would it hold up to pressure washing, etc year after year..

4 . what other options?

In summary, I am not really trying to save money, but more importantly to not waste money and effort by applying a paint that will be worthless when submerged (due to the only 90 day window). Also, trying to do as much while upside down as reasonable. Perhaps just apply the option # 1 but know the antifoul will not work well, so just pressure wash as needed.....saves sanding at least... Or, leaning to option #3 if folks think the I2000E
would hold up to wear and washing for a few years at least...

Note 1- I have faired since these pics were taken, including rounding out the keel bottom.
Note 2 - the aluminum hull did not actually need any barrier coat, but I wanted to fair low spots and seal the fairing filler, so hence the use of I2000E primer/ barrier coat.

I would appreciate any advice!
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gdcarpenter
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Re: Advice wanted on bottom paint vs other types / finishes

Post by gdcarpenter » Tue Mar 15, 2016 2:34 pm

I can only give my input/experience with VC Performance Epoxy. I used it on my ZIP

I understand it to be rated for up to 60 continuous days of immersion. I have had my ZIP floating for a little over a month at a time, fresh water, and no issues. I have had my bottom VC paint on now for well over 3 years and over 5,000 miles of trailering, no issues. If it gets real slimy or get rub marks I can literally fine sand it, and since there are about 7 coats, I have no plans to redo it in the foreseeable future.
This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

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chugalug
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Re: Advice wanted on bottom paint vs other types / finishes

Post by chugalug » Tue Mar 15, 2016 8:24 pm

:D Most of the aluminum boats I've owned don't have paint on bottom,just bare metal then paint on sides above waterline.sometimes they are left in water all season;you can wash green slime off when it's wet.however if left to dry on,you'll have to use something stronger.My dad swears by Simple Green.I like Zing but you have to wear rubber gloves as its acid.washes off tho.works good to clean off lower unit of outboards.
Working on regular-sized Bo-Jest


"If it's not crooked,It's not mine

North
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Re: Advice wanted on bottom paint vs other types / finishes

Post by North » Wed Mar 16, 2016 5:10 am

Thanks for the responses!

- I am considering the VC performance, but I read that it would have been good over the bare (properly sanded / prepped) aluminum on it's own, so it kind of makes the 4 coats or so of I2000E redundant....or unnecessary..

- I would have considered leaving the hull bare, but I had some low spots / distortion (from too much heat welding) and I wanted to fair the bottom.
I know it would be underwater, but when I see it on the trailer, or stored all winter, I din't want to look at the unfair hull and say "Boy, that would have been a lot easier to fix while it was upside down"....
Prepping and applying some type of primer/ paint seemed like the only choice if wanting to fair,after first coat of primer)

Tech support said I2000E is not "meant" to be a final coat - normally something else overcoats it... but can it be is the question. I know tech support would know more, but my local interlux dealer's paint guy said that it would hold up fine as final coat - just no antifouling, but neither does the vc performance, so I am leaning towards leaving the I2000E on it's own.....see how it does for a year or two... can always sand and apply something else later, albeit right side up and more difficult.....

red
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Re: Advice wanted on bottom paint vs other types / finishes

Post by red » Thu Mar 17, 2016 12:08 am

as long as the hull is primed all over and it looks like it is from the pics all you need is a good two part poly two to three coats and it will be fine. If you like the Interlux products ask your supplier if he can get any of the eclipse line of paint its made by AkzoNobel its the parent company of Interlux.it might cost more than you want to spent but it will last a lot longer than any of the marine/antifouling paints you can get

North
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Re: Advice wanted on bottom paint vs other types / finishes

Post by North » Thu Mar 17, 2016 6:51 am

Hi Red - can you (or anyone) explain why I would need a 2 part paint over the 2 part epoxy primer (paint)? I do understand that primer is usually overcoated with some form of finish paint... I don't mean to beat this to death, but what properties are missing in the 2 part epoxy primer that would be present in a (finish) 2 part paint? i.e. is the primer paint not tough enough to hold up to spray washing, trailer bunks, etc on its own and it needs a final coat over it to protect it?

red
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Re: Advice wanted on bottom paint vs other types / finishes

Post by red » Sat Mar 19, 2016 3:01 am

primer is softer than the top coat it will wear away faster

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jamundsen
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Re: Advice wanted on bottom paint vs other types / finishes

Post by jamundsen » Sat Mar 19, 2016 6:15 am

Primer creates a good surface for your finish to adhere to. And like Red said its much softer.
John Amundsen
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kens
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Re: Advice wanted on bottom paint vs other types / finishes

Post by kens » Sat Mar 19, 2016 6:54 am

What about using epoxy resin, and a filler of some sort,?
I used graphite powder/epoxy for my bottom coat, no paint at all.
There is copper powder that yields a epoxy resin that looks like olde school copper anti-fouling paint.
There are other additives also, derived from various substrates, for different colors.
Aluminum powder?? since it is a aluminum boat??
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

North
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Re: Advice wanted on bottom paint vs other types / finishes

Post by North » Tue Mar 22, 2016 3:56 pm

Hi Ken - had I not already put down 1 coat of I2000E epoxy primer, I may have juts stuck with epoxy the whole way and added something like you suggest. But, since I have the primer on and fairing almost done, I will at least stick with the plan of applying about 3-4 more coats of I2000E primer.

I am leaning towards then juts trying the boat out this year, limited use / sea trials. Then next year I can late apply 1 more coat of primer and then bottom paint, or sand the primer that is on there and apply something else. I am not sure about applying straight epoxy (with an additive), on top of the existing primer...I guess I did apply epoxy to fair it... But how does the epoxy flow? Is its easy to apply, and what are the advantages?

For folks who responded re: primer qualities, etc - thanks. Now I at least know the strengths and weaknesses of leaving it by itself vs overcoating it...

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kens
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Re: Advice wanted on bottom paint vs other types / finishes

Post by kens » Tue Mar 22, 2016 9:00 pm

The big advantage for me is the fact that I have no paint on the bottom, no discussion about what kind of paint etc., etc. I only used graphite powder and it looks like black bottom paint, except it is only epoxy. I can come back later with any kind of paint I may choose. It been 10 years now and I haven't chosen a preferred paint yet, nothing to prefer better than epoxy. But then my build is wood not aluminum. It flows on easy with a roller, and it not as pretty as shiny paint, but it is on the bottom where you can't see it, it is also very easy to patch up after you hit trash in the water, or hit the trailer. I like it for a workboat as ours are,
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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