Epoxy fairing of hull

[AbelCMann]

Ahoy Mates! This may have been addressed in the past but I have not come across it so here we go - I have had my 1965 Alberg 30 sodablasted primarily to reveal her history, structural integrity, and any necessary repairs needed. While the hull seems very strong and intact there was many shallow craters left from osmotic blistering. Moisture readings are quite low - 4 was the reading almost everywhere except the sump area, which has since been pumped and wiped dry. My plan is to let her dry for a bit (not long I hope) then fair with epoxy, followed by barrier coat, hard coat, and ablative to finish. The marina service manager suggests West System with cavasil filler added, my surveyor insists it is too labor and time intensive and I should go with a premixed compound. I would welcome those with actual experience and expertise to weigh in and make the case for either or yet another approach. I will be doing the work myself and am not unskilled. Time is a part of the decisionmaking process, but in the end I am determined to do what is required for a sound and lasting solution. Anticipating knowledgable and thoughtful responses I thank you in advance.

[Stumble]

The gold standard is thickened epoxy then long board till your arms fall off.

There is nothing wrong with a premix, so long as it's an epoxy base. But I don't see the point. It just saves you the 30 second step of mixing in a thickening agent.

[model 10]

Another idea might be, give it a coat of barrier coat. Then look it over and fill the really ugly spots. The contrast of blasted surface to fresh paint will high lite what really looks bad. Then load it up with more barrier coat. Bottom paint hides a lot of this kind of damage.
Vinyl-ester bondo does ok under water if it's under epoxy paint and it would be much faster.

[minaret]

Originally Posted by AbelCMann

Ahoy Mates! This may have been addressed in the past but I have not come across it so here we go - I have had my 1965 Alberg 30 sodablasted primarily to reveal her history, structural integrity, and any necessary repairs needed. While the hull seems very strong and intact there was many shallow craters left from osmotic blistering. Moisture readings are quite low - 4 was the reading almost everywhere except the sump area, which has since been pumped and wiped dry. My plan is to let her dry for a bit (not long I hope) then fair with epoxy, followed by barrier coat, hard coat, and ablative to finish. The marina service manager suggests West System with cavasil filler added, my surveyor insists it is too labor and time intensive and I should go with a premixed compound. I would welcome those with actual experience and expertise to weigh in and make the case for either or yet another approach. I will be doing the work myself and am not unskilled. Time is a part of the decisionmaking process, but in the end I am determined to do what is required for a sound and lasting solution. Anticipating knowledgable and thoughtful responses I thank you in advance.

Use 407 instead of cabosil. That stuff is not for fairing, it cures hard as nails and is quite difficult to sand. There are pics of the whole process in my Nauticat 52 refit thread, stickied in the top of construction and maintenance.

[hlev00]

+1 407. West Systems has a lot of great information. They are also very helpful if you call to ask for advice.

WEST SYSTEM | Use Guides - Fairing

[HopCar]

Get yourself a mixer you can put in an electric drill. You'll wear your arm out mixing by hand and you won't have any arm left to sand with.

Minaret, why 407 instead of 410?
Wait I don't want to know. I just put 410 all over the little skiff I'm building! It sands nice.

[minaret]

Originally Posted by HopCar

Get yourself a mixer you can put in an electric drill. You'll wear your arm out mixing by hand and you won't have any arm left to sand with.

Minaret, why 407 instead of 410?
Wait I don't want to know. I just put 410 all over the little skiff I'm building! It sands nice.

Seen too many failures of 410. It does sand super nice though. Often I mix a little 410 in with my 407. Slicks on nicer and sands easier too. I don't like to use more than about 20% 410. Straight 410 is too soft....


You knew I was gonna tell you anyway.

[Chasing Summer]

I agree with Guy ... I've been in contact with the west coast rep for Akzo Noble who reps both Interlux and Awlgrip and he recommended Interlux 2000 barrier coat then fill with Awlfair ... 120 sand and another coat of 2000. After that Hullgard Extra.

[HopCar]

"You knew I was gonna tell you anyway."
Yes I did. I'll let you know when the 410 all falls off.
I need an excuse to repaint it anyway. Fighting Lady Yellow, ugh.
My excuse? I had a lot of it.

[minaret]

Originally Posted by HopCar

"You knew I was gonna tell you anyway."
Yes I did. I'll let you know when the 410 all falls off.
I need an excuse to repaint it anyway. Fighting Lady Yellow, ugh.
My excuse? I had a lot of it.

It doesn't fall off, just gets soft and chalky eventually. Especially below the waterline. How thick you mix makes a huge difference to its longevity. If you mix mayo consistency and it slicks on glossy wet looking, all may be ok. But if you mix it peanut butter thick and it goes on looking dry, you will have problems...

[HopCar]

I'll have problems.

[minaret]

Originally Posted by HopCar

I'll have problems.

It's a boat. You most certainly will.

[HopCar]

I've decided to name the boat "Lumpy".

[Pete7]

Originally Posted by HopCar

I've decided to name the boat "Lumpy".

Paint it blue, sand it lightly and pretend its a Pirate map with lots of islands to find treasure.

[Suijin]

Originally Posted by Guy

Vinyl-ester bondo does ok under water if it's under epoxy paint and it would be much faster.

No.

Don't use vinyl or polyester below the waterline for this sort of thing. It's just asking for trouble. I'm particularly sensitive to the issue as I just got through grinding off about 12 sq. feet of it, under barrier coat, that had become waterlogged and failed. It absorbs water...one flaw in your barrier coat and you'll have a problem and wished that you had spent a bit more time and money to do it right in the first place.

I'm with Minaret on using 407. While it's not *quite* as easy to sand as 410, it has better adhesive properties and in fact I find that the ~20% greater hardness over 410 gives a bit more control when fairing.

For a repair I barrier coat, sand with 30 grit, fair with epoxy/fairing compound, then barrier coast again. The first barrier coast provides a better surface for whatever you're fairing with and provides a bit of insurance to boot.