Hello,
I am thinking of mooring my M this coming up season (Puget Sound). I have heard that bottom paint reduces the boats speed. Under power with a 70 hp Suzuki, how much MPH/Knots can I expect to lose? Under sail? Will it even be noticable? Thanks.
Bottom Paint and the reduction of speed
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Jeff S
- First Officer
- Posts: 371
- Joined: Tue Jun 08, 2004 2:13 pm
- Location: Cherry Point, NC 2000 26X Tohatsu 50
A lot depends on what type of bottom paint you use. Some are slicker than others, some even have teflon in them. Sloughing paint is probably the slowest (most friction drag) followed by ablatives, which are fairly common. If I didn't alredy have bottom paint on or did not keep the boat in a slip I would prefer to keep the bottom unpainted personally.
If you must paint the bottom there is a lot that goes into determining the best bottom paint for you. If you plan to trailer some simply don't hold up out of the water. West Marine Advisor has some good tips on bottom painting HERE
As a side note I bought WM CPA w/Iragrol. A friend at my marina said that I should have bought bottom paint w/o the anti-slime agent and instead go to Sherwin Williams and buy an anti-fungal powder that you simply stir into the paint. I am not sure how well this would work, but it would certainly be less expensive. The marketing on the anti slime makes it seem like the technology can't be matched by simply stirring in some anti-fungal powder but then again it is marketing. . .
In the end bottom paint will cause more drag than a polished hull and it will be more noticeable the faster you go. Under sail it will be less noticeable, however for those who race every 0.1 knot is meaningful so serious racers generally don't bottom paint the boat, or use very slick bottom paint.
So those who answer should qualify with the type of bottom paint they use.
I had bottom paint on the boat when I purchased it, and I gained speed when I repainted because the old paint was worn out and had barnacles so removing the growth and repainting helped my speed by about 1 knot at WOT. I don't know about sailing since I have had a steep learning curve with sailing and have done some rigging changes, added a rigid vang and such so my sailing speeds have increased overall.
Jeff S
If you must paint the bottom there is a lot that goes into determining the best bottom paint for you. If you plan to trailer some simply don't hold up out of the water. West Marine Advisor has some good tips on bottom painting HERE
As a side note I bought WM CPA w/Iragrol. A friend at my marina said that I should have bought bottom paint w/o the anti-slime agent and instead go to Sherwin Williams and buy an anti-fungal powder that you simply stir into the paint. I am not sure how well this would work, but it would certainly be less expensive. The marketing on the anti slime makes it seem like the technology can't be matched by simply stirring in some anti-fungal powder but then again it is marketing. . .
In the end bottom paint will cause more drag than a polished hull and it will be more noticeable the faster you go. Under sail it will be less noticeable, however for those who race every 0.1 knot is meaningful so serious racers generally don't bottom paint the boat, or use very slick bottom paint.
So those who answer should qualify with the type of bottom paint they use.
I had bottom paint on the boat when I purchased it, and I gained speed when I repainted because the old paint was worn out and had barnacles so removing the growth and repainting helped my speed by about 1 knot at WOT. I don't know about sailing since I have had a steep learning curve with sailing and have done some rigging changes, added a rigid vang and such so my sailing speeds have increased overall.
Jeff S
Last edited by Jeff S on Mon Nov 29, 2004 4:41 pm, edited 1 time in total.
It depends on the type of paint used to what effect of friction you will see.
ablative paints are made to slough off as you move through the water. as such they will slow you some. How much? I suppose not much because I see quite a few power boats with ablative paints. And you know how fast those "stink potters" like to go.
Racing sailboats use hard finishes such as baltoplate and vc-offshore. They are hard, help protect against osmosis, and are slick. They are what we use when we sit in the water rather than dry sail. There is some speed difference when OD racing, but it is small and more due to added weight of paint than anything else.
ablative paints are made to slough off as you move through the water. as such they will slow you some. How much? I suppose not much because I see quite a few power boats with ablative paints. And you know how fast those "stink potters" like to go.
Racing sailboats use hard finishes such as baltoplate and vc-offshore. They are hard, help protect against osmosis, and are slick. They are what we use when we sit in the water rather than dry sail. There is some speed difference when OD racing, but it is small and more due to added weight of paint than anything else.
bottom paint may reduce your top speed some 1/10 knots under power and none under sails. but i tell you that NO bottom paint when the boat is in a slip will reduce your speed sensibly! i learned this in 2003 when i moved from an inshore lake to salt water environment and my bottom paint was not adapted to that. i had a biotope of barnacles under my hull (they loved my silicone antifouling!), and at the end of the season the boat moved under sail like a 5 ton barge!
tripp gal, sorry to disagree, no antifouling prevents from osmosis. you'll always need to apply an epoxy coat first.
tripp gal, sorry to disagree, no antifouling prevents from osmosis. you'll always need to apply an epoxy coat first.
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kmclemore
- Site Admin
- Posts: 6301
- Joined: Sun Feb 08, 2004 9:24 am
- Sailboat: MacGregor 26X
- Location: Ambler, PA -- MACX2018A898 w/ Suzuki DF60AV -- 78 BW Harpoon 4.6 -- 2018 Tahoe 550TF w/ 150 Merc
Jeff, may I ask that you re-format your link so that this page is more readable?
Currently your link is coded like this:
However, if you simply edit your post and change that to...
... then we won't all have that horrendously long link to deal with.
Note that the actual address you want to send folks to is contained after the "" ... then you put in some text to make the link active
(in this case the word "HERE") and then you close the URL statement with the "" command.
What you end up with is this:
If you want to get fancy, you can make the "HERE" in bold and/or underlined type, but those
commands must begin and end inside the "URL" statement, like this:
... and that would look like this:
Cheers,
Kevin McLemore
Currently your link is coded like this:
Code: Select all
West Marine Advisor has some good tips on bottom painting at
[url]http://www.very-long-address-here.com[/url]Code: Select all
West Marine Advisor has some good tips on bottom painting
[url=http://www.very-long-address-here.com]HERE[/url].Note that the actual address you want to send folks to is contained after the "" ... then you put in some text to make the link active
(in this case the word "HERE") and then you close the URL statement with the "" command.
What you end up with is this:
West Marine Advisor has some good tips on bottom painting HERE.
If you want to get fancy, you can make the "HERE" in bold and/or underlined type, but those
commands must begin and end inside the "URL" statement, like this:
Code: Select all
West Marine Advisor has some good tips on bottom painting
[url=http://www.very-long-address-here.com][b][u]HERE[/b][/u][/url].Thanks, Jeff!West Marine Advisor has some good tips on bottom painting HERE.
Cheers,
Kevin McLemore
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kmclemore
- Site Admin
- Posts: 6301
- Joined: Sun Feb 08, 2004 9:24 am
- Sailboat: MacGregor 26X
- Location: Ambler, PA -- MACX2018A898 w/ Suzuki DF60AV -- 78 BW Harpoon 4.6 -- 2018 Tahoe 550TF w/ 150 Merc
Now, as to bottom painting, of course you need to use the proper formulary for your locale. However, to get the best speed after painting, I have a couple of tips from when I used to race many years ago...
First, as with any painting, preparation and application are everything. Regardless of the method you use, it's extremely important to get as smooth an application as possible... whether you use brush, roller or spray (last option is illegal with many paints), the smoother you can get the pre- and post- painting surface, the better. Also, remember to apply it in line with the boat's travel so that the 'grain' of the paint is less resistant to the water rushing past.
Second, we found that after application of the bottom paint (or even on the bare gelcoat when we were not bottom painting), if you lightly wet-sand the entire submerged surface with a #320 or #400 grit paper, in line with the boat's travel, you will remove any surface defects and also create a light series of scratches in the boat's surface. These scratches will cause an ever-so slight tubulence next to the boat's skin, causing a very, very thin film of water 'stick' to the surface of your boat, and this thin film of water will act as a sort of lubricant between the hull and the other surrounding water. Now I know this is really fine points, and probably won't make a whit of difference when powering, but in light air during a race it can well make the difference between winning and losing. On the down side, however, your hull looks a bit dull below the waterline.... that is, if anybody notices.
First, as with any painting, preparation and application are everything. Regardless of the method you use, it's extremely important to get as smooth an application as possible... whether you use brush, roller or spray (last option is illegal with many paints), the smoother you can get the pre- and post- painting surface, the better. Also, remember to apply it in line with the boat's travel so that the 'grain' of the paint is less resistant to the water rushing past.
Second, we found that after application of the bottom paint (or even on the bare gelcoat when we were not bottom painting), if you lightly wet-sand the entire submerged surface with a #320 or #400 grit paper, in line with the boat's travel, you will remove any surface defects and also create a light series of scratches in the boat's surface. These scratches will cause an ever-so slight tubulence next to the boat's skin, causing a very, very thin film of water 'stick' to the surface of your boat, and this thin film of water will act as a sort of lubricant between the hull and the other surrounding water. Now I know this is really fine points, and probably won't make a whit of difference when powering, but in light air during a race it can well make the difference between winning and losing. On the down side, however, your hull looks a bit dull below the waterline.... that is, if anybody notices.
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Frank C
Only by "hearsay" comparisons over the years (never objectively tested) ... but I'm guessing that the ablative paints reduce speed by 2 mph, WOT. However, given your premise that you'll be keeping the boat on a mooring, there's simply no choice but to barrier-coat and then paint the bottom, or you'll quickly lose 12mph at WOT.
Granted, this observation could as easily be attributed to poor application methods as to the drag of the paint itself, but it seems that owners have have always reported notably slower speeds after painting, compared with their bare-bottomed hulls. Just one unscientific observation. If you paint your boat, guess we'll have another data point!
Granted, this observation could as easily be attributed to poor application methods as to the drag of the paint itself, but it seems that owners have have always reported notably slower speeds after painting, compared with their bare-bottomed hulls. Just one unscientific observation. If you paint your boat, guess we'll have another data point!
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Dimitri-2000X-Tampa
- Admiral
- Posts: 2043
- Joined: Fri Jan 02, 2004 5:36 am
- Sailboat: MacGregor 26X
- Location: Tampa, Florida 2000 Mercury BigFoot 50HP 4-Stroke on 26X hull# 3575.B000
I don't know if I agree with that estimate Frank. Again by hear-say, I'm not sure it makes much difference at all when you have a clean bottom with ablative paint. I have a bottom painted (paint is ragged out too) boat with 50HP and my top speed varies between 17-19.5 mph depending on my load and conditions. With the exception of a few very stripped and mastless boats that have claimed to have gotten over 20 with a 50, it doesn't seem that my speed is 2 mph lower than most of the non painted boats have reported.
Now, get some good growth on there and you will definitely lose 2-3 mph in addition to messing up your fuel economy.
Now, get some good growth on there and you will definitely lose 2-3 mph in addition to messing up your fuel economy.
KRV
Why not give Seaview boatyards a call. One at Shilshole and I believe one at Everett. I found them to be very helpful when we painted our X. They were up on the latest tests done by Practical Sailor. For me the issue was not speed reduction, but rather how long between paintings as the paint is not cheap.
Why not give Seaview boatyards a call. One at Shilshole and I believe one at Everett. I found them to be very helpful when we painted our X. They were up on the latest tests done by Practical Sailor. For me the issue was not speed reduction, but rather how long between paintings as the paint is not cheap.
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Catigale
- Site Admin
- Posts: 10421
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- Sailboat: MacGregor 26X
- Location: Admiral .............Catigale 2002X.......Lots of Harpoon Hobie 16 Skiffs....Island 17
- Contact:
I slip Catigale in the Hudson and have neither paint nor epoxy on her bottom - I wax her underneath at beginning of every season only.
I dont get growth on her - must be all the PCBS GE put in the river...the coolest thing was the first time she went into salt water this summer at Nantucket, all the fresh water slime shriveled up and died. She was in brine for a week, then came back to fresh water - where all the salt water stuff did the same thing!!!
It took me three weeks of hosing each weekend to get rid of all the salt - my hats off to you salt water guys - its brutal....Im sticking to the Great Lakes...little ponds that they are.
My zincs had never shown corrosion until the first day in salt - then they grunged up. It was galvanising to watch.
My Ericson 32 friend in Buffalo who re-invigorated me to get into sailing years back is bummed since I beat him to salt water - GO MAC!!!
Blue paint is faster than white paint in the northern hemisphere.
I dont get growth on her - must be all the PCBS GE put in the river...the coolest thing was the first time she went into salt water this summer at Nantucket, all the fresh water slime shriveled up and died. She was in brine for a week, then came back to fresh water - where all the salt water stuff did the same thing!!!
It took me three weeks of hosing each weekend to get rid of all the salt - my hats off to you salt water guys - its brutal....Im sticking to the Great Lakes...little ponds that they are.
My zincs had never shown corrosion until the first day in salt - then they grunged up. It was galvanising to watch.
My Ericson 32 friend in Buffalo who re-invigorated me to get into sailing years back is bummed since I beat him to salt water - GO MAC!!!
Blue paint is faster than white paint in the northern hemisphere.
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Catigale
- Site Admin
- Posts: 10421
- Joined: Fri Jun 11, 2004 5:59 pm
- Sailboat: MacGregor 26X
- Location: Admiral .............Catigale 2002X.......Lots of Harpoon Hobie 16 Skiffs....Island 17
- Contact:
I slip Catigale in the Hudson and have neither paint nor epoxy on her bottom - I wax her underneath at beginning of every season only.
I dont get growth on her - must be all the PCBS GE put in the river...the coolest thing was the first time she went into salt water this summer at Nantucket, all the fresh water slime shriveled up and died. She was in brine for a week, then came back to fresh water - where all the salt water stuff did the same thing!!!
It took me three weeks of hosing each weekend to get rid of all the salt - my hats off to you salt water guys - its brutal....Im sticking to the Great Lakes...little ponds that they are.
My zincs had never shown corrosion until the first day in salt - then they grunged up. It was galvanising to watch.
My Ericson 32 friend in Buffalo who re-invigorated me to get into sailing years back is bummed since I beat him to salt water - GO MAC!!!
Blue paint is faster than white paint in the northern hemisphere.
I dont get growth on her - must be all the PCBS GE put in the river...the coolest thing was the first time she went into salt water this summer at Nantucket, all the fresh water slime shriveled up and died. She was in brine for a week, then came back to fresh water - where all the salt water stuff did the same thing!!!
It took me three weeks of hosing each weekend to get rid of all the salt - my hats off to you salt water guys - its brutal....Im sticking to the Great Lakes...little ponds that they are.
My zincs had never shown corrosion until the first day in salt - then they grunged up. It was galvanising to watch.
My Ericson 32 friend in Buffalo who re-invigorated me to get into sailing years back is bummed since I beat him to salt water - GO MAC!!!
Blue paint is faster than white paint in the northern hemisphere.
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Frank C
Well, hearsay is the operative word. You'll not even get a square comparison of boat speeds using identical hulls, identical motors, identical paints . . . since everyone quotes their speed but never their measurement device and conditions. I'm guessing 2 mph from reading before/after comments by owners who, like the original poster, went from bare-hull to paint. That's why I hope to see the results here - another data point.Dimitri-2000X-Tampa wrote:I don't know if I agree with that estimate Frank. Again by hear-say, I'm not sure it makes much difference at all when you have a clean bottom with ablative paint. . . .
