Dry dock

[Charlotte Burnett]

I'm in the process of ordering everything I require for dry docking in early April. I intend to paint both the underside and top side in a week - thankfully, I've help coming in the form of parents and friends. I've a 72' River class so there is a hell of a lot to do!

 

On very good advice, I have decided I'm going to overpaint the remnants of the bitumen with Epimastic MT - the theory being that I've scraped most of the black off breaking ice and anything that remains is well stuck. I intend to paint from the gunwales down and had intended 3 coats. The price though is eye watering and I want to run through that before I order.

 

72' = 22m, width = 7' or 2.1m depth = approx 1.5m

 

therefore, 2(22x1.5) + (22x2.1) = 112.2 m2 (one coat)

 

@ 6m2 per litre = 18.7 ltrs per coat

 

3 x 18.7 = 56.1 ltrs/5

 

= 12 tins @ £57 each = £684 - and that's before I've bought rollers, scraper blades etc!

 

Should I perhaps only do 2 coats?

 

Thanks

[ditchcrawler]

I'm in the process of ordering everything I require for dry docking in early April. I intend to paint both the underside and top side in a week - thankfully, I've help coming in the form of parents and friends. I've a 72' River class so there is a hell of a lot to do!

 

On very good advice, I have decided I'm going to overpaint the remnants of the bitumen with Epimastic MT - the theory being that I've scraped most of the black off breaking ice and anything that remains is well stuck. I intend to paint from the gunwales down and had intended 3 coats. The price though is eye watering and I want to run through that before I order.

 

72' = 22m, width = 7' or 2.1m depth = approx 1.5m

 

therefore, 2(22x1.5) + (22x2.1) = 112.2 m2 (one coat)

 

@ 6m2 per litre = 18.7 ltrs per coat

 

3 x 18.7 = 56.1 ltrs/5

 

= 12 tins @ £57 each = £684 - and that's before I've bought rollers, scraper blades etc!

 

Should I perhaps only do 2 coats?

 

Thanks

From this site it says one coat. It also says that blasting is not required if its not going to be immersed, as its the bottom of a boat and is going to be immersed I would suggest that indicates blasting is required.

[STUBAG]

From this site it says one coat. It also says that blasting is not required if its not going to be immersed, as its the bottom of a boat and is going to be immersed I would suggest that indicates blasting is required.

And PLEASE remember, any coating is only as good as its substrate, ie if you put the most expensive paint in the world on top of mediocre, old, porous coatings, you've wasted your time and money.Also, if you paint the entire boat in the time you have specified, you've done it wrong.

[Rebotco]

I think your maths is a bit suspect!

If your boat is 22m long and you are coating 1.5m depth, that is 66 sq mts all round per coat. (But allow say 75 sq mts because of the front and rear curvatures)

The width of the boat is then hardly relevant.

75 sq mts at 6 sq mts/lt is 12.5 litres per coat. In 5 lt tins that is 2.5 tins per coat at £57/tin = £142 per coat.

(except you'll presumably have to buy 3 tins, so £171 total)

And if its a 2 part mix, I think its usually only one coat thats needed.

That looks a bit better doesn't it?

[Charlotte Burnett]

From this site it says one coat. It also says that blasting is not required if its not going to be immersed, as its the bottom of a boat and is going to be immersed I would suggest that indicates blasting is required.

 

Yes. Further down, by the "brush/roller" application, it also states multiple coats will be required to meet film thickness requirements.

 

The recommendation to paint over the bitumen with it did not come from a bloke in the pub, it would be unfair of me to name him because both he and I are well aware that it is contrary to manufacturer recommendations but he has extensive experience of doing just this on a commercial fleet. The proviso is that the hull is scraped and wire brushed to a very high standard.

 

Doing it wrong?! I'm desperately trying not to and the schedule is very tight. I intend to try and get a lot of the surface prep done before I go into the dock but it is tight. My understanding is that I prep the boat with 80 grit, then prime, 150 grit, prime, 150 grit, undercoat, 240 grit, undercoat, 320 grit, top coat, 320 grit, top coat. Is that about right?

 

The plan was:

 

 

Saturday

 

remove all relevant portholes

Sand bow and roof and Furtan

Pressure wash

wire brush, scrape

 

Sunday

 

needle gun, wire brush and scrape

Set up scaffolds

Sand sides

grind and sand gunwales

Prime roof, sides, gunwales, bow

 

Monday

Fill low spots

2nd coat primer

Survey

Black bottom and sides

 

Tuesday

 

sand

1st undercoat

anodes

Black bottom and sides

 

Wednesday

Sand

2nd Undercoat

Black bottom and sides

 

 

Thursday

Sand

1st Topcoat

 

 

 

Friday

Sand

2nd topcoat

 

Saturday

back in water

 

 

Thanks

[Timleech]

Yes. Further down, by the "brush/roller" application, it also states multiple coats will be required to meet film thickness requirements.

 

The recommendation to paint over the bitumen with it did not come from a bloke in the pub, it would be unfair of me to name him because both he and I are well aware that it is contrary to manufacturer recommendations but he has extensive experience of doing just this on a commercial fleet. The proviso is that the hull is scraped and wire brushed to a very high standard.

 

 

 

I've used Epimastic MT on non-grit blasted hull repairs, it has survived intact until the next docking but then came straight off with the (powerful) pressure washer, so I wouldn't expect it to hold up well against serious abrasion.

I'd expect to get roughly one coat on one side of a 70' boat, top guard to chine, put on with mini-roller and brush, from a 5l pack, though it's a couple of years since I've done a job like that so my memory may be inaccurate.

I think you would struggle with it with a full sized roller.

 

Tim

[Grace and Favour]

Yes. Further down, by the "brush/roller" application, it also states multiple coats will be required to meet film thickness requirements.

 

The recommendation to paint over the bitumen with it did not come from a bloke in the pub, it would be unfair of me to name him because both he and I are well aware that it is contrary to manufacturer recommendations but he has extensive experience of doing just this on a commercial fleet. The proviso is that the hull is scraped and wire brushed to a very high standard.

 

Doing it wrong?! I'm desperately trying not to and the schedule is very tight. I intend to try and get a lot of the surface prep done before I go into the dock but it is tight. My understanding is that I prep the boat with 80 grit, then prime, 150 grit, prime, 150 grit, undercoat, 240 grit, undercoat, 320 grit, top coat, 320 grit, top coat. Is that about right?

 

The plan was:

 

 

Saturday

 

remove all relevant portholes

Sand bow and roof and Furtan

Pressure wash

wire brush, scrape

 

Sunday

 

needle gun, wire brush and scrape

Set up scaffolds

Sand sides

grind and sand gunwales

Prime roof, sides, gunwales, bow

 

Monday

Fill low spots

2nd coat primer

Survey

Black bottom and sides

 

Tuesday

 

sand

1st undercoat

anodes

Black bottom and sides

 

Wednesday

Sand

2nd Undercoat

Black bottom and sides

 

 

Thursday

Sand

1st Topcoat

 

 

 

Friday

Sand

2nd topcoat

 

Saturday

back in water

 

 

Thanks

 

But you're not giving ANY of your coats of paint time to cure!!

 

I would (this is strictly my personal OCD) allow at least a day between coats, and a few days after the final coat before dropping it back in the water

[GUMPY]

I'm in the process of ordering everything I require for dry docking in early April. I intend to paint both the underside and top side in a week - thankfully, I've help coming in the form of parents and friends. I've a 72' River class so there is a hell of a lot to do!

Took my stepson 2 weeks prep on the topsides

Then 2 weeks in the dock to repaint 2 coats and 2 Coats of blacking.

You will run out of time unless you do a lot of prep before hand.

[Ex- Member]

If you're going to use quality paint then put it on a properly prepared surface otherwise you're just throwing money away.

 

As a minimum requirement I would remove all bitumen, a 2 pack epoxy coating usually requires a much better substrate than tar.

 

Personally I would do the whole job properly, shot blasted with a minimum 2 coats. I went a bit OTT and applied 6 coats to the sides, but then I shouldn't need to come out of the water for 10 years.

 

We had our 60f/t wide beam blasted for £350

 

shop around you should get a good price.

 

BTW with 2 pack I managed to coat ours in 6 coats inside 7 days, 2 pack paint dries quick and can be over coated quickly, in fact you can't leave it for too long otherwise you'll be rubbing it down again. It also cures quickly and can be back in the water within 24 hours of final coat.

 

We used Jotun, absolutely brilliant stuff, pricey but worth every penny, apply with roller, lay off with brush. If you shot blast I would highly recommend a barrier primer if there's such a coating from your Epimastic MT supplier. ake a look at Joun thoug, I was originally sceptical of expensive paint, but you do get what you pay for with Jotun and would assume from other 2 pack coatings.

[David Mack]

I think your maths is a bit suspect!

If your boat is 22m long and you are coating 1.5m depth, that is 66 sq mts all round per coat. (But allow say 75 sq mts because of the front and rear curvatures)

The width of the boat is then hardly relevant.

75 sq mts at 6 sq mts/lt is 12.5 litres per coat. In 5 lt tins that is 2.5 tins per coat at £57/tin = £142 per coat.

(except you'll presumably have to buy 3 tins, so £171 total)

And if its a 2 part mix, I think its usually only one coat thats needed.

That looks a bit better doesn't it?

 

There's nothing wrong with Charlotte's maths. She is painting the bottom as well as the sides.

[Rebotco]

There's nothing wrong with Charlotte's maths. She is painting the bottom as well as the sides.

 

 

Ah thank you. Thats not clear from the description, but is more so from the figures given.

Not used to people painting their baseplates as a rule.

[David Mack]

I hope you have a lot of help! Cleaning off and reblacking a 70 ft hull, bottom included, and repainting the topsides in a week is no small undertaking.

 

When we last had Fulbourne in dock we had a team varying from 2 to 7 over the course of the week, averaging 4-5 and we managed to wire brush the whole hull to remove the old (lumpy) blacking, three coats of bitumen, repaint the bow and stern and touch up the back cabin. We did also have a hull survey and couple of bits of welding done, but they didn't really add to the time taken. But there's no way we would have had time to paint the whole of the cabin.

 

Having cleaned off one side of the hull we made an early start on the blacking while still cleaning the other side (at the other end), and continued to work in stages around (and under) the hull. Allowing 24 hours between coats and 48 hours before refloating, we still only just about finished in time, and the bits that were welded didn't get the full three coats.

[DHutch]

Personally I would say that one week to do below the gunnel, and a week to do above, is about right, rather than doing it all in one.

 

You can then

 

Day one

Pressure wash off and start surface prep of blacking and full inspection.

 

Day two

Finish blacking surface prep and primer bare metal

 

Day three

Coat one blacking and begin preping remainder of below gunnel side.

 

Day three

Second coat blacking, priming etc of area above.

 

Day four

Coat one of area above and messing around other things like repacking stg.

 

Day five

Coat two of area above and messing about with things like painting your gas locker

 

Day six

Some contingency time but also any thing else want to get done

 

Day seven

Back in the water.

 

 

Then do the topsides when the ground is higher up and less far to fall head long onto!

 

 

 

Daniel

[Timleech]

There's nothing wrong with Charlotte's maths. She is painting the bottom as well as the sides.

 

I hadn't looked at the maths so didn't spot that.

It's highly unlikely the bottom plate will be fit for applying 2-pack after just a bit of wire brushing. There's usually much more work to prepare a bottom plate than sides.

 

 

Tim

[Malarky]

Personally I would say that one week to do below the gunnel, and a week to do above, is about right, rather than doing it all in one.

 

You can then

 

Day one

Pressure wash off and start surface prep of blacking and full inspection.

 

Day two

Finish blacking surface prep and primer bare metal

 

Day three

Coat one blacking and begin preping remainder of below gunnel side.

 

Day three

Second coat blacking, priming etc of area above.

 

Day four

Coat one of area above and messing around other things like repacking stg.

 

Day five

Coat two of area above and messing about with things like painting your gas locker

 

Day six

Some contingency time but also any thing else want to get done

 

Day seven

Back in the water.

 

 

Then do the topsides when the ground is higher up and less far to fall head long onto!

 

 

 

Daniel

 

That seems a much less frightning list!

I would just add the price of materials to the start; and probably set that before even enquiring

about products, mostly 300, 500 or 1000 incremental choices; and it costs 20 to go out the door, goes at the end!

[blackrose]

I've used Epimastic MT on non-grit blasted hull repairs, it has survived intact until the next docking but then came straight off with the (powerful) pressure washer, so I wouldn't expect it to hold up well against serious abrasion.

 

So in the OP's case what's the point of paying out all that money for epoxy paint and then putting it on top of old bitumen? It seems like a waste of time and money. Personally I'd either be getting the boat grit blasted (or ultra-high pressure water jetted) first, or not using epoxy and just using bitumen.

Edited March 12, 2013 by blackrose

[ditchcrawler]

So in the OP's case what's the point of paying out all that money for epoxy paint and then putting it on top of old bitumen? It seems like a waste of time and money. Personally I'd either be getting the boat grit blasted (or ultra-high pressure water jetted) first, or not using epoxy and just using bitumen.

Same.

[kevinl]

I'm in the dry dock in a few weeks, the price I was quoted (last week) for; docking, cleaning off and scraping then 3 coats of a good quality blacking was £10.00 per foot + VAT. It should last 3-4 years.

The costs given here don't seem to include the cost of docking, all the consumables you'll need (white spirit, rollers, cleaning materials etc) and the schedule is to say the least tight in terms of time if one thing goes wrong the whole plan falls apart. I'd focus on getting the underwater bits done properly and any of the topside you can get done is a bonus you can always finish it later out of the dry dock.

I also agree with other comments that putting anything over conventional blacking without blasting first probably isn't the best idea.

[Lady Muck]

What Timleech said, ours had been epoxied before we bought her, it all came off with pressure washing when we craned out for a survey, the whole lot just fell off. I suspect it was millscale as the boat was still pretty new, but it just shows you, you have to prepare the hull properly or you're wasting your time.

[RickH]

Yes. Further down, by the "brush/roller" application, it also states multiple coats will be required to meet film thickness requirements.

 

The recommendation to paint over the bitumen with it did not come from a bloke in the pub, it would be unfair of me to name him because both he and I are well aware that it is contrary to manufacturer recommendations but he has extensive experience of doing just this on a commercial fleet. The proviso is that the hull is scraped and wire brushed to a very high standard.

 

Doing it wrong?! I'm desperately trying not to and the schedule is very tight. I intend to try and get a lot of the surface prep done before I go into the dock but it is tight. My understanding is that I prep the boat with 80 grit, then prime, 150 grit, prime, 150 grit, undercoat, 240 grit, undercoat, 320 grit, top coat, 320 grit, top coat. Is that about right?

 

The plan was:

 

 

Saturday

 

remove all relevant portholes

Sand bow and roof and Furtan

Pressure wash

wire brush, scrape

 

Sunday

 

needle gun, wire brush and scrape

Set up scaffolds

Sand sides

grind and sand gunwales

Prime roof, sides, gunwales, bow

 

Monday

Fill low spots

2nd coat primer

Survey

Black bottom and sides

 

Tuesday

 

sand

1st undercoat

anodes

Black bottom and sides

 

Wednesday

Sand

2nd Undercoat

Black bottom and sides

 

 

Thursday

Sand

1st Topcoat

 

 

 

Friday

Sand

2nd topcoat

 

Saturday

back in water

 

 

Thanks

Often overlooked but worth a small mention , you will be sitting on blocks in the dry dock , that part of the bottom will not be able to be scraped or painted unless the boat is lifted and blocks replaced at a different location , unless you're going to simply , leave those bits .

[Ex- Member]

Often overlooked but worth a small mention , you will be sitting on blocks in the dry dock , that part of the bottom will not be able to be scraped or painted unless the boat is lifted and blocks replaced at a different location , unless you're going to simply , leave those bits .

 

 

The proviso is that the hull is scraped and wire brushed to a very high standard.

 

That is not sufficient for application of 2 pack, oils tars and greases must be removed and or any existing coating that is not solidly applied.

 

You'll not do that with scrapers and wire brushes. Where tar is apparent it should be completely removed, abrasion to bear steel surfaces is also required, wire brushes might partially remove paint & surface rust , but will not etch the metal adequately to accept a quality 2 pack paint.

[kittsy]

why dose everyone try to do the maths just slap it on with a good wide brush as thick as you like below the water line and at the waterline where the hull sides meet the air then neat and tidy above the water line rollers do not constitute a coat as there is no way of knowing how think you think your application is so paint it on with a brush and roll it out dont bother trying to save money do working out how much you need and just protect your investement as best you can

[Dovetail]

Yes. Further down, by the "brush/roller" application, it also states multiple coats will be required to meet film thickness requirements.

 

The recommendation to paint over the bitumen with it did not come from a bloke in the pub, it would be unfair of me to name him because both he and I are well aware that it is contrary to manufacturer recommendations but he has extensive experience of doing just this on a commercial fleet. The proviso is that the hull is scraped and wire brushed to a very high standard.

 

Doing it wrong?! I'm desperately trying not to and the schedule is very tight. I intend to try and get a lot of the surface prep done before I go into the dock but it is tight. My understanding is that I prep the boat with 80 grit, then prime, 150 grit, prime, 150 grit, undercoat, 240 grit, undercoat, 320 grit, top coat, 320 grit, top coat. Is that about right?

 

The plan was:

 

 

Saturday

 

remove all relevant portholes

Sand bow and roof and Furtan

Pressure wash

wire brush, scrape

 

Sunday

 

needle gun, wire brush and scrape

Set up scaffolds

Sand sides

grind and sand gunwales

Prime roof, sides, gunwales, bow

 

Monday

Fill low spots

2nd coat primer

Survey

Black bottom and sides

 

Tuesday

 

sand

1st undercoat

anodes

Black bottom and sides

 

Wednesday

Sand

2nd Undercoat

Black bottom and sides

 

 

Thursday

Sand

1st Topcoat

 

 

 

Friday

Sand

2nd topcoat

 

Saturday

back in water

 

 

Thanks

 

 

If you have a couple of people helping you and putting in a good weeks work then I would say you have a good chance achieving this but otherwise I think you have little chance ticking everything on the list.

Early April can be cool and damp and can effect drying time especially if you are planning the work at Uxbridge?

The most important thing is to black the boat and then consider anything after that a bonus. I wish you good luck and hope you get good weather even if you are under cover as it makes all the difference.

[JDR]

Has anybody heard of blacking being applied over two pack? I only ask because my neighbour's boat has been blacked over the top of the original two pack and I wasn't even aware this was a possibility.

[Ex- Member]

Has anybody heard of blacking being applied over two pack? I only ask because my neighbour's boat has been blacked over the top of the original two pack and I wasn't even aware this was a possibility.

 

Unless the 2 pack was properly prepared then tar applied on to it won't last very long. 2 pack should be re-coated ideally with the same, and again the original would need keying back ideally with an 80/100 grit DA sander. 2 pack paints dry back really hard almost like a glass finish, in fact many contain powdered glass, so any re-coating requires quality preparation meaning all the shine should be removed.

Edited March 17, 2013 by Julynian