Post Process After Soda Blasting Bottom

[Whatfiero1]

Need apply above 50 deg and according to strick time schedule. for the fairing sand out just below gel coat with sander on slow and be careful with 80 grit and a rotory sander on high you can sand right thru boat in a minute. but sand 3 to 4" around and fill first with straight epoxy then thickened then sand flat then apply epoxy barrier coat

 

[jssailem]

I have some travel for work in May, so I would like to complete this work in April, launch the boat in April, and reposition the boat to it's new seasonal marina about 100 nm away.

It is a bugger when work interferes with our planning. But it’s got to be done.
May the Pennsylvania Rodent come out on a cloudy day and you get an early spring. Be sure the boat hull temp is warm enough to handle the fairing compound. It is the hull temp not the air temp you need to worry about.

 

[Ward H]

Be sure the boat hull temp is warm enough to handle the fairing compound. It is the hull temp not the air temp you need to worry about.

I bought a IR Temp Gun to check engine temps but find it useful for many things, including checking hull temp prior to painting. Here is a link to the one I bought. IR Temp Gun on Amazon

 

[snoopy_]

Need apply above 50 deg and according to strick time schedule. for the fairing sand out just below gel coat with sander on slow and be careful with 80 grit and a rotory sander on high you can sand right thru boat in a minute. but sand 3 to 4" around and fill first with straight epoxy then thickened then sand flat then apply epoxy barrier coat

I was planning on skipping the epoxy step post sanding, as the fairing material is a waterproof epoxy. I also was not performing any blister repair as I did not see anything that was worth addressing. Do you think I still need to sand out chips and apply epoxy and epoxy filler?

 

[Whatfiero1]

Well I understand your not racing but you need to get it smooth some how try lightly sanding and then rub your hand across and feel how bad the dip is

 

[snoopy_]

Well I understand your not racing but you need to get it smooth some how try lightly sanding and then rub your hand across and feel how bad the dip is

I don't necessarily have a dip per se, it's just the bottom appears rough from soda blasting. Some spots show pinholes, some have a chip in the gelcoat, and I haven't even sanded it yet. I thought using a fairing compound may fill in all those imperfections and add a waterproof barrier, then I would apply the Pettit Protect as an additional epoxy barrier and finally, apply the antifoul.

 

[Whatfiero1]

I don't necessarily have a dip per se, it's just the bottom appears rough from soda blasting. Some spots show pinholes, some have a chip in the gelcoat, and I haven't even sanded it yet. I thought using a fairing compound may fill in all those imperfections and add a waterproof barrier, then I would apply the Pettit Protect as an additional epoxy barrier and finally, apply the antifoul.

Sounds like a great plan

 

[snoopy_]

The more I read, the more reluctant I become about tackling the bottom work.

In some articles I read about the importance of ensuring the hull is completely dry before applying a barrier coat, not doing so could make the blister issues worse by locking in moisture with the epoxy barrier. Some speak about placing the boat under heat lamps, in garages, etc. and waiting a year or more for the boat to dry out completely. I can't do that, as I've already paid for my seasonal slip!

Other articles discuss barrier coats being a poor choice for a low cost boat such as mine and suggest simply using a primer such as Primocon and applying antifoul bottom paint. e.g. DIY Osmosis Repair

Should I take the time to attempt investigating blisters, sand, epoxy, barrier, bottom paint, as in any job worth doing is worth doing well. Or am I in a "less is more" situation, where to do too much would lead to the inability of using the boat next season? I am due to launch April timeframe.

My boat is thirty years old. It's a nice boat in good condition and I want to take care of it, but it's not a shrine. Am I overthinking this? i.e. Paralysis by analysis.

Thanks,
Snoopy

 

[Whatfiero1]

Sealing is best plan and keeps any new blisters away. You just need pick weather window and set alarms on phone to go thru all steps on time and get it done. If possible let dry on blocks as long as possible and wipe entire bottom bow with acetone before you start first coat acetone removes the moisture from surface

 

[shemandr]

Given your situation I would apply KISS principle. If most the gelcoat is in tact there's no need for barrier coat. Just repair the pinholes and/or fair the rough spots. Epoxy over the repairs, smooth and go on to bottom paint. Then go sailing. A smooth bottom is a pleasure to sail with. But it doesn't have to be perfect - just smooth. If you want to do a complete bottom job you won't sail until after Memorial Day, if not the 4th of July.

 

[njlarry]

Need apply above 50 deg and according to strick time schedule. for the fairing sand out just below gel coat with sander on slow and be careful with 80 grit and a rotory sander on high you can sand right thru boat in a minute. but sand 3 to 4" around and fill first with straight epoxy then thickened then sand flat then apply epoxy barrier coat

Thanks for the link. It sounds awfully complicated for getting the right temps and timing. How do you get two or more barrier coats on and then the antifoul on without a whole lot of sanding?

 

[snoopy_]

njlarry, I didn’t read any required sanding... yet. There was steps in sanding and fairing, and cleaning, but once the barrier coat is started there seems to be a time limit before starting next coats, as well as how long after coating, that the next coat can be applied without having to sand. Then there is specific timing of how long to wait after barrier before beginning bottom coat.

 

[Ward H]

My boat is thirty years old. It's a nice boat in good condition and I want to take care of it, but it's not a shrine. Am I overthinking this?

In my humble opinion, yes, you're getting lost in the weeds.
If you were racing or were a long distance cruiser where 1/2 knot of lower speed may mean adding hours to your trip, then you would want the bottom perfect.
But your not, your a day sailor and according to an earlier post, you want a relaxing sail. What will you miss more, a little speed or possibly several months of sailing this season?

Don't get me wrong, I'm a do it right the first time kind of guy and typically over think and over do a lot of my systems. The bottom is not one of them.

Each spring I scrap off loose paint and put a fresh coat on with a double coat on the waterline and high wear areas. (this is for three seasons now). Once it's in the water I forget about it. I would rather focus on improving my tools for sail trim. That's where I think I will get the most speed increase for my dollar. When I can get perfect sail trim and still want to go faster I'll invest time and money for a new bottom.

I was in a similar position as you are when I bought my O'day 25. The first fall it was hauled out the yard called to tell me that as the bottom was drying the paint was flaking of the bottom. I checked and sure enough it was. I had them media blast it. It looked a lot like yours with little chips out of the gel coat. This was in the fall.
In the spring I used a non blushing penetrating epoxy for the first coat. Then a little thicker epoxy for the second coat. Neither were true barrier coatings.
Then I put on 3 coats of ablative bottom paint. By the time this was done the bottom was smooth. The bottom paint didn't flake off and I just put one new coat on each year for the next 4 years before I sold the boat.
This was not a by the book solution but it worked for me.

As for letting the bottom dry out, a full winter would be better but you are not going to get warm enough weather to do the bottom until later March or early April. Let it dry out til then. Then plan a simple solution for sealing the gel coat and putting bottom paint on. Three days of good weather and you can have it done in time for launch.

 

[jssailem]

Snoopy.
Here is some good info about blisters.

Hull Blisters on Boats and Yachts - by David Pascoe, Marine Surveyor

Online articles on boat hull blisters by David Pascoe, Marine Surveyors:hull blister repairs, blister repair failure, blister warranty, history of boat hull blisters, blister boat purchase

www.yachtsurvey.com

Ward shares some smart thinking.
Seal the boat with thickened epoxy or epoxy fairing compound. Paint all with a couple layers of barrier coat following the paint manufacturer’s application directions.

Cover that with a couple coats of an ablative and splash. Go sailing. Next year touch up and keep sailing till you sell.

I do not believe we can make the boat back to before blisters without a lot of money.
At best we can limit the further damage.