Removing bottom paint: How long does it take?

Dr. D

.
Nov 3, 2018
278
Beneteau Oceanis 35.1 Herrington Harbour North
This winter I will put my boat on the hard. During that time I will sand the bottom to remove the last layer of hard bottom paint (Trinidad Pro). From posts here and on other fourms I have picked up how to do it, but I can't tell how long to do this for a 34' boat. Some posts imply several days, others a few hours. My marina rents sanders for $15 an hour. That would be OK for a few hours, but not if this will take 10 hours or so.

So when you sand off bottom paint, how long does it take you?
 
Feb 21, 2013
4,638
Hunter 46 Point Richmond, CA
Days..........you may have to use multiple techniques to do that. I am sure other forum members will also offer their experience.
 
Jan 1, 2006
7,468
Slickcraft 26 Sailfish
$10/ Hour isn’t bad compared to $ 90/Hour labor rate. I just bought a Dewalt jig saw for $50 at a pawn shop.
When I did my Mark 25 bottom it took days to get to gel coat.
 
Sep 25, 2008
7,336
Alden 50 Sarasota, Florida
Last time I sanded off bottom paint was on a 40 ft hull and it only took about 5 hours total. And I’m slow.
 

Dr. D

.
Nov 3, 2018
278
Beneteau Oceanis 35.1 Herrington Harbour North
Here it is again!

"Days" and "5 hours".

Are we somehow comparing apples to oranges?
 
Jun 25, 2004
1,109
Corsair F24 Mk1 003 San Francisco Bay, CA
With all due respect, why do you want to remove the last layer of Trinidad, down to the gelcoat? Unless you have a special reason for doing that, why do it? There is no need to remove all the paint down to the gelcoat before you apply a new coat of bottom paint, unless the old paint is flaking off or the gelcoat is badly blistered.

If the bottom has been power washed immediately when hauled, cleaned of hard and soft growth, and the paint is well adhered, all you need to do is sand the surface with 80 grit before repainting. That's 3-6 hours with a sander and vacuum system . The vacuum system is necessary to capture the poisonous dust.

I have used Trinidad SR for the past 20+ years. It's a very good at preventing hard and soft growth, and very easy to repaint. (It's also expensive, but worth every penny. IMO)

I have done bottom paint jobs 12-15 times in the past 25 years
I can prep and paint 2 coats on a 30 foot hull in two full work days, including dry time.

I have stripped old paint down to gelcoat and barrier coated hulls 3 times in the past 25 years.
Barrier coating means more prep and applying at least 5 coats.
Barrier coating is a big job and very expensive. Materials cost twice as much as repainting. Labor time is at least triple compared to a good antifouling job. It's much more labor if you fair and longboard the bottom after sanding.
 

Dr. D

.
Nov 3, 2018
278
Beneteau Oceanis 35.1 Herrington Harbour North
My first post could have been worded better. I am not seeking to get down to the gelcoat, or the epoxy barrier coat. I want to remove most of the last layer of paint before repainting to avoid arriving (in several or more years) at paint flaking off due to having too many old coats. There is a layer of red Trinidad over the barrier coat and the last layer of paint is black. So I want to sand until I get to the red coat.
 
Jun 25, 2004
1,109
Corsair F24 Mk1 003 San Francisco Bay, CA
My first post could have been worded better. I am not seeking to get down to the gelcoat, or the epoxy barrier coat. I want to remove most of the last layer of paint before repainting to avoid arriving (in several or more years) at paint flaking off due to having too many old coats. There is a layer of red Trinidad over the barrier coat and the last layer of paint is black. So I want to sand until I get to the red coat.
I've done this exact job with Tridnidad at least 10 times.

4 days total. two paid yard days.

Day #1 Haul out day.
They don't charge you for the haul out day usually Get it powerwashed while its wet. Let the bottom dry thoroughly.

Day #2 First yard day:
4-5 hours to tape and sand, fix any dings, then retape before painting.
1 - 2 hours to apply first coat. Check the paint film thickness with a film gauge available at any paint store for $1 or 2.
Find an old office chair on wheels to save your back. Most yards have them hanging around.

Day #3 Second yard day.
Apply 2nd coat in morning.
After it's dry to the touch, have the yard move the boat stands and sand/paint 1st coat on bare spots.
Apply 3rd coat on leading edges in the afternoon after necessary drying time to overcoat. Remove tape.
Clean up and prep boat for launch.
Come back later and paint a 2nd coat where the stands were.

Day #4 launch Day. Usually this day is free. The yard launches when it's convenient for them, not you, so it's free.

Judy B
PS don't forget to take the tape off your depth sounder and speedo plug. it doesn't come off by itself. Don't ask me how I know.... :facepalm:
 
Last edited:
Feb 21, 2013
4,638
Hunter 46 Point Richmond, CA
Sand first layer only.............that makes a big difference so hours. Agree wiwith DrJudyB.
 
May 17, 2004
5,541
Beneteau Oceanis 37 Havre de Grace
Removing the last coat vs removing all coats is definitely the apples vs oranges. On a 37’ boat I spend about 3 hours sanding the top layer off with 80 grit on a vacuum sander. On a 28’ boat I spent about 4 days removing 20 years of layers.
 
  • Like
Likes: DrJudyB
Jan 1, 2006
7,468
Slickcraft 26 Sailfish
Here it is again!

"Days" and "5 hours".

Are we somehow comparing apples to oranges?
Yes! There's a huge difference between prepping a bottom for re-painting and stripping all the paint off for either a barrier boat or for a start over in bottom paint.
 
Sep 24, 2018
3,262
Catalina 30 MKIII Chicago
As for the sander, I can attest to the dewalt that I bought for $70. It's by far the most used power tool (aside from a drill) that I use on my boat. It's been through a lot, pukes fiberglass dust everytime it's turned on and it still runs like a champ. If I were to do it over again I would opt for one that has variable speed control so I can use it to keep my gelcoat looking pretty (occasional touch ups, not full 600-1000 grit full hull jobs)
 

Joe

.
Jun 1, 2004
8,158
Catalina 27 Mission Bay, San Diego
Just a quick comment. Invest in a variable speed oscillating sander and a shop vac with an additional hose. Unless you are prepared to enclose the entire boat so dust cannot escape and contaminate neighboring boats, do not use a disc sander.... but... if you do 'cause you're in a hurry... NO 80 grit!!!! that's a good way chew right through to the fiberglass.. I stripped a boat down to the base with a variable speed disc sander... I used 240 grit on low speed and I had to be careful with that.
The 5" or 6" vs osc unit will be one of your most important power tools and has a myriad of uses... on the boat or at home.
 
Jun 25, 2004
1,109
Corsair F24 Mk1 003 San Francisco Bay, CA
Hi repainted the bottom (all three of 'em!) on my Trimaran the weekend of June 15 - 18, working on Saturday and Sunday. I used a Mikita 5" Random Orbital Palm sander with a shop vac with a HEPA filter. and a very nice hose system. I think I used 80 grit and 100 grit, because that’s what I had. I used a foam pad under the sand paper, not a hard backing disc. The foam pad prevents gouging.

And, yes, I did wear a P100 mask.

 
Last edited:
Apr 12, 2007
202
Hunter 420 Herrington Harbor South
Make sure you check the HHN yard rules they are getting very touchy about personal sanding jobs.
 

jviss

.
Feb 5, 2004
7,089
Tartan 3800 20 Westport, MA
Considering the toxicity of bottom paint, I would never sand it myself. My boat yard, due to environmental regulations, won't allow removal of bottom paint unless it's done by a certified pro. Folks wanting this hire a pro who builds a tent around the boat, including a floor, and blasts it off with walnut shells or some such stuff. There's a collection system for the debris. Very thorough, fast, and clean, but not cheap.
 

jviss

.
Feb 5, 2004
7,089
Tartan 3800 20 Westport, MA
"Antifoul is designed as a toxic paint to chemically aggitate marine life that gets near it. For this reason it is not safe for humans either. Dry sanding, the toxic dust particles are so fine that they will go through carbon filter masks. The dust will also be absorbed through skin and eyes. As well as many other harmful substances, the copper content gets absorbed into the blood stream. Copper is very difficult for the body to digest and will build up to higher levels over time, which can be fatal. It has been proven in studies that, even after wet sanding, small particles get trapped under the finger nails and end up on your sandwiches in dangerous ammounts, and that is after washing your hands."

Dry sanding off your antifouling.
 
Jan 19, 2010
1,271
Catalina 34 Casco Bay
A club mate of mine removed many layers from his C&C 33 this spring. He used the power washer with a sand pickup tube technique. Went thru 500 lbs of sand. Bought the attachment to convert the washer for $50.00. Trick is to keep the sand dry. So mounting it higher than the Venturi pickup tube keeps water from falling down the tube and making the sand wet.
 
Sep 24, 2018
3,262
Catalina 30 MKIII Chicago
A club mate of mine removed many layers from his C&C 33 this spring. He used the power washer with a sand pickup tube technique. Went thru 500 lbs of sand. Bought the attachment to convert the washer for $50.00. Trick is to keep the sand dry. So mounting it higher than the Venturi pickup tube keeps water from falling down the tube and making the sand wet.
Any chance you could ask him where he bought it from?