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1 hour ago, leeava said:

Does anyone have a opinion on ceramic coating the bottom of you Sailboat.

I see on my automobile less static adhesion of dirt/ debris.  Seems to last longer than wax. Smoothing the pours out seems like the right thing to do.

you going to use the cheap stuff or the expensive stuff?

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16 hours ago, leeava said:

Smoothing the pours out seems like the right thing to do.

I don’t know what you’re smoking, but around here a nano-particle coating will not do ANYTHING to “Smooth out pores”!  This has to be done by working many hours with longboards and buffers.  Waxing a pig, or in this case Ceramicing a pig will just make is a shinny pig!  It may only make it a tiny bit quicker, as growth with have a harder time attaching to the hull.  

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1 hour ago, silent bob said:

I don’t know what you’re smoking, but around here a nano-particle coating will not do ANYTHING to “Smooth out pores”!  This has to be done by working many hours with longboards and buffers.  Waxing a pig, or in this case Ceramicing a pig will just make is a shinny pig!  It may only make it a tiny bit quicker, as growth with have a harder time attaching to the hull.  

You're dismissed from the spelling & grammar police.

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24 minutes ago, SloopJonB said:

You're dismissed from the spelling & grammar police.

I didn’t waste too much time with reatin’ and ritin’ classes. I spent my time in chemistry and shop. This bottom is a 50’er that I did a while ago. The smoothness and shine didn’t come from a bottle!  It was from weeks of work!  

6B8E8E3B-9DC6-4CE6-B9FA-EB19AD613419.jpeg

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1 hour ago, sledracr said:

Holy crap... that's pretty!  Nice job.

Thanks!  It helped that I had no budget issues!  
 

53 minutes ago, quod umbra said:

Seriously nice job.
Curious the straps look to be on the hull instead of plastic, wax paper or cardboard, etc.

There was paper in there. But this epoxy system gets super scratch resistant after it’s polished!  

52 minutes ago, SloopJonB said:

Nicer than most topsides but I don't get it - is it dry sailed with wax on the bottom?

A couple days in the water and that mirror finish will be buried in slime.

Yes, dry sailed.  Yes, waxed, just plain wax!  Cleaned daily.  Diver was invested in project.  First few days after launch, he wiped with diapers, then terrycloth, then a white Scothbrite pad late in the week. 

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If you want the absolute best which has been tested and proven..and just in case, I have no skin in this game.

Then you need to investigate "Nano-Ceramic Industrial Protective Coatings" at this address.

www.nano-ceramic.com then find "Market Segments" and select "Marine". 

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12 hours ago, Don said:

If you want the absolute best which has been tested and proven..and just in case, I have no skin in this game.

Then you need to investigate "Nano-Ceramic Industrial Protective Coatings" at this address.

www.nano-ceramic.com then find "Market Segments" and select "Marine". 

This is starting to sound interesting for a dinghy.  Having spent hours on cleaning up two bottoms, one now without a blemish or scratch and you can see yourself in it, the other almost as shiny but I haven't invested in removing all of the scratches yet.

Ceramic bottom on a dinghy seems like something that the relative costs would be less, the work will still be the same?

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17 minutes ago, GH41 said:

I am no rocket scientist but it seems to me like a wet sanded bottom would break the surface tension better than a slick one and be faster.. Why do golf balls have dimples? 

I thought it was about creating additional lift?  And perhaps you are thinking of the boundary layer that determines friction, aka drag?

If a dimple hulled boat were fast I would have expected an AC boat or some other high end, no budget boat to already do it?  Can you imagine the maintenance that would go into maintaining a boat with a golf ball like dimpled surface?  I have never seen anyone purposefully leave a dinghy hull not shiny, certainly the top of the fleet is shiny.

Not that I want to create a new thread about how lift works that morphs into one of the many decade long thread.  I'm just thinking that a ceramic bottom on a dinghy might prevent the browning often seen from sailing weekly over a season?  A shiny hull surface always feels fast even if a dimply hull would be faster.

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Dimples on a golf ball create a thin turbulent boundary layer of air that clings to the ball's surface. This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake.

Sounds like it's only for small surfaces.

Dimpled boats and aircraft would seemingly not be in out future.

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Some friends of ours have been cruising the southern Caribbean on a sister ship to ours for the last several years, leaving the boat on the hard in Trini for hurricane season and returning every November for another 6 months. On their last return, our friends announced they were trying a "new" way of dealing with growth on their running gear/folding prop. A coating of Egg Whites. I kind of laughed that off but, evidently, it's something the locals use to good advantage. N'any case, they gave their gear 7 coats with egg whites before re-launching last December. Since then, they have reported virtually no growth on their shaft and prop. Evidently, PropSpeed has a low cost competitor, eh?
 

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On my truck the ceramic coating the dealer applied was remarkable for it's durability and ease of cleaning.   I did not pay a penny for it so I was more or less a test case for the new tech they had in the detail shop.   I will pay for it next time as it's WAY better than any wax I've put on from a can or bottle.  Collinite paste is great, but doesn't have the durability or easy cleaning of the ceramic coat.

I have been using the Griots spray ceramic after washing for my little boat and it's way easier to clean than without a coating.   The surface has to be shiny and essentially perfect prior to application, but what coating doesn't need that?

 

 

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9 hours ago, Foredeck Shuffle said:

I thought it was about creating additional lift?  And perhaps you are thinking of the boundary layer that determines friction, aka drag?

If a dimple hulled boat were fast I would have expected an AC boat or some other high end, no budget boat to already do it?  Can you imagine the maintenance that would go into maintaining a boat with a golf ball like dimpled surface?  I have never seen anyone purposefully leave a dinghy hull not shiny, certainly the top of the fleet is shiny.

Not that I want to create a new thread about how lift works that morphs into one of the many decade long thread.  I'm just thinking that a ceramic bottom on a dinghy might prevent the browning often seen from sailing weekly over a season?  A shiny hull surface always feels fast even if a dimply hull would be faster.

Do blister count?

 

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12 hours ago, GH41 said:

I am no rocket scientist but it seems to me like a wet sanded bottom would break the surface tension better than a slick one and be faster.. Why do golf balls have dimples? 

Hah... this is an endless conversation at yacht club bars, where everyone becomes a fluid dynamics expert. 
 

  1. The only thing that matters is surface smoothness. And it matters a lot. On this the MIT scientists and the legendary Bethwaites agree: Sanding to 3000 grit and polishing to mirror finish is faster than 800 grit.
  2. It is as a practical matter impossible to make a hull smooth enough that  laminar flow stays attached the entire length of the hull. It invariably breaks into turbulent flow a little bit back from the bow.  The smoother the surface, the longer the laminar flow stays attached and the more of the hull experiences laminar flow and the less of the hull experiences turbulent flow. Laminar flow is faster than turbulent flow.
  3. Dimples on golf balls and those rows of little tiny guitar pick sized tabs on the top of airplane wings are designed to generate turbulence, on the theory that predictable turbulence behaves better than unpredictable turbulence.
  4. Air and water behave very differently: water is incompressible, and a lot thicker than air. What works on golf balls and airplanes may not work on boats.  People have been experiencing with "shark skin" type deliberate roughening of boat hulls for a while, but nothing practical has come out of it yet.   Web searching "reynolds number" will lead you down interesting rabbit holes.
  5. The water molecules closest to the hull don't slide along the hull; they stay stuck to the hull right where they are. The water molecules further from the hull slide over those stuck water molecules. Web searching "no slip condition" will lead you down other interesting rabbit holes.
  6. "Surface tension" is really about the interaction of water and air; it doesn't really have an impact on the flow of water over a submerged hull.
  7. The chemical composition of the surface doesn't matter, only the smoothness. (The chemical composition matters to the extent that it contributes to smoothness, i.e., to the extent that it hard and resists microscopic dents, or that it is soft and mushes around to smooth over microscopic dents after they form.
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17 minutes ago, Howler said:

Hah... this is an endless conversation at yacht club bars, where everyone becomes a fluid dynamics expert. 
 

  1. The only thing that matters is surface smoothness. And it matters a lot. On this the MIT scientists and the legendary Bethwaites agree: Sanding to 3000 grit and polishing to mirror finish is faster than 800 grit.
  2. It is as a practical matter impossible to make a hull smooth enough that  laminar flow stays attached the entire length of the hull. It invariably breaks into turbulent flow a little bit back from the bow.  The smoother the surface, the longer the laminar flow stays attached and the more of the hull experiences laminar flow and the less of the hull experiences turbulent flow. Laminar flow is faster than turbulent flow.
  3. Dimples on golf balls and those rows of little tiny guitar pick sized tabs on the top of airplane wings are designed to generate turbulence, on the theory that predictable turbulence behaves better than unpredictable turbulence.
  4. Air and water behave very differently: water is incompressible, and a lot thicker than air. What works on golf balls and airplanes may not work on boats.  People have been experiencing with "shark skin" type deliberate roughening of boat hulls for a while, but nothing practical has come out of it yet.   Web searching "reynolds number" will lead you down interesting rabbit holes.
  5. The water molecules closest to the hull don't slide along the hull; they stay stuck to the hull right where they are. The water molecules further from the hull slide over those stuck water molecules. Web searching "no slip condition" will lead you down other interesting rabbit holes.
  6. "Surface tension" is really about the interaction of water and air; it doesn't really have an impact on the flow of water over a submerged hull.
  7. The chemical composition of the surface doesn't matter, only the smoothness. (The chemical composition matters to the extent that it contributes to smoothness, i.e., to the extent that it hard and resists microscopic dents, or that it is soft and mushes around to smooth over microscopic dents after they form.

And after all those precise measurements, the crew of engineers somehow comes in last place by 7.32 miles again. 
 

You can’t equate a bottom job to the mistakes that a crew make that can eat off way more time than you can polish up on the trailer:D

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17 minutes ago, Sail4beer said:

And after all those precise measurements, the crew of engineers somehow comes in last place by 7.32 miles again. 
 

You can’t equate a bottom job to the mistakes that a crew make that can eat off way more time than you can polish up on the trailer:D

For most of us mere mortals, time spent perfecting our boathandling beats time spent polishing the bottom.

 

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You got that right. Learn the boat and the routine(mistake management) and the bottom can be ablative, gelcoat or burnished Baltoplate and you will still be way ahead of the competition.

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I like the idea. 

 

these are answers I received a couple of years ago on fast antifouling/bottom. especially part 2 which was apparently from someone who did the research for some America's cup syndicates.

1. Wipe the surface down with Fiberglass Solvent Wash 202
2. Sand the surface with 80 grit paper
3. Remove all sanding residue with Fiberglass Solvent Wash 202
4. Fill all damaged areas with Watertite Epoxy Filler
5. Sand the Watertite with 80 grit paper
6. Remove all sanding residue with Fiberglass Solvent Wash 202
7. Apply 2 coats of InterProtect 2000E
8. Apply 3 coats of VC Performance Epoxy
 
However if the blisters were deeper, where they would have broken into the laminate, then it would be best for you to fill the areas with a clear epoxy resin first to seal the laminate off and then proceed along with the system mentioned above. This system would best be followed as:
1. Wipe the surface down with Fiberglass Solvent Wash 202
2. Sand the surface with 80 grit paper to open up all of the blisters
3. Seal the laminate off with 2-4 coats of a clear epoxy resin (maybe Epiglass or West System)
4. Wash the epoxy with warm soapy water and a stiff brush
5. Sand the epoxy with 120 grit paper
6. Remove all sanding residue with Fiberglass Solvent Wash 202
7. Fill all damaged areas with Watertite Epoxy Filler
8. Sand the Watertite with 80 grit paper
9. Remove all sanding residue with Fiberglass Solvent Wash 202
10. Apply 2 coats of InterProtect 2000E
11. Apply 3 coats of VC Performance Epoxy or 2-3 coats of your desired antifouling paint
 
As for the potential overlapping, if you are using a two component topside finish such as Perfection above the waterline, then I would have no issue with you applying the Perfection overtop of the VC Performance Epoxy or vice versa. However if you were using a one component topside finish such as Brightside above the waterline, then I would recommend that you only allow the Brightside to overlap the VC Performance Epoxy and not vice versa. The main reasoning would be the aggressive solvents which are in the VC Performance Epoxy will dissolve the Brightside if applied overtop, as where there will be very little to almost no adverse reaction if Brightside were applied overtop of the VC Performance Epoxy. 
 
 
I have had good luck with Interlux performance expoxy. Wet sands easily. My 10 year old bottom is still as white as new and glossy as gelcoat. 600 grit is as fair as I go, but for the heck of it, I did take the bulb down to 1200 and it shines. I put overtop a few layers of IP2000e
 
PART 2
 
ther are several, which as mentioned above, i cannot mention due to certain bit of paper.

In essence, we built a series of hi tech devices (water flow) that measured the friction of hundreds of coatings and applied film systems from durepox to PTFE to Graphite to syloxines to silicones etc... You name it we tested it.

We were even involved with clear coatings for red and white cricket balls to make them last, shine, and have consistant flight etc... But thats another story for ..sails and spars

d,urepox is ok for a cost effective " retail" system however if you want a faster system there is one i can give you that i explained in a previous post. Andnits relatively cheap.

This applies to gel coated, urethaned and durepox surfaces.

1. Guide coat hull, rudder and keel.

2. Sand in the direction of the water flow with 350 400

3. Apply Kisscote as per directions. ( its not cheap but you dony need much.)

4. Go faster!

This was a top ten system.

There were a couple of standouts in the top ten and many that were very close to each other. 
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2 hours ago, JMOD said:

I like the idea. 

 

these are answers I received a couple of years ago on fast antifouling/bottom. especially part 2 which was apparently from someone who did the research for some America's cup syndicates.

1. Wipe the surface down with Fiberglass Solvent Wash 202
2. Sand the surface with 80 grit paper
3. Remove all sanding residue with Fiberglass Solvent Wash 202
4. Fill all damaged areas with Watertite Epoxy Filler
5. Sand the Watertite with 80 grit paper
6. Remove all sanding residue with Fiberglass Solvent Wash 202
7. Apply 2 coats of InterProtect 2000E
7a  Sand with 120
7b Sand with 180
7c Sand with 220
8. Apply 3 coats of VC Performance Epoxy
8a  Sand with 320
8b  Sand with 400
 

or some such

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11 hours ago, Grande Mastere Dreade said:

i thought dimpled / textured skins were "outlawed"...       

43 minutes ago, MegaHertz said:

I thought so too. But i'm often wrong.

53. SKIN FRICTION
A boat shall not eject or release a substance, such as a polymer, or have specially textured surfaces that could improve the character of the flow of water inside the boundary layer.
 
But if this were effective I would have expected something like the AC to change this rule to suit their needs.  That the AC has never done so says that their tests in CFD and scale model tank tests have not produced useful results.
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1 hour ago, Foredeck Shuffle said:

But if this were effective I would have expected something like the AC to change this rule to suit their needs.  That the AC has never done so says that their tests in CFD and scale model tank tests have not produced useful results.

" Stars and Stripes design coordinator John Marshall disclosed the boat's "secret weapon" as the hull's underside, coated with a "riblet" skin that helped the craft slide through the sea more smoothly."

https://www.nasa.gov/centers/langley/news/factsheets/Riblets.html

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Some surfer came up with the idea of hot coating the bottom of a surfboard with a clear coat of polyester resin mixed with finely ground Alka Seltzer and after that had cured to sand down just enough to expose the granules of Alka Seltzer. Then you jump off a boat right onto the face of a big wave like Jaws and you have about 30 seconds of turbo bubbles on the bottom of the board to decrease your drag through the water until the fizzy action dies out. Or you die when the wave pounds you into the reef. 

    I googled that concept and lo and behold it turns out to be an idea from Tom Morey (RIP). He talks about aeration on the bottom of the board via dimples and at the very bottom of this excerpt he mentions Alka-Selter.

But when we're riding through yards and yards of water on a wave, you can't make it no matter how you pump and jump because the board is just too sticky.

The wonderful breakthrough in the equipment is that at the surface, where we surf, there's another medium - air.

And every surfer should do this.

Get down under the boogie board or plank, put a face mask on, and when you're in the water, look up at the bottom of the board, and you'll see sitting on the surface, between you and the board, big and tiny bubbles of air.

They look like silver.

If you then wiggle your board, you'll see that the bubbles' size increases and disperse.

If you wiggle it a lot, you will see that instead of just being held away from the water by 2, 3, 4, 5, or 6 percent air, the thing is held away from the water by 99 something percent.

Ninety-nine percent almost like that. They're almost all free from the water because of the air that gets entrapped there.

Now to focus on the air entrapment aspect - that's a great place to spend some time with different texture surfaces on the materials, different pockets.

I had way back come up with golf ball pockets which hold air and keep it away from the surface.

But in between these golf ball pockets and the water, there would another thin and flexible membrane glued here and there on the high points between the pockets, like 100 or 300 tiny trampolins on the [Morey Boogie Mach 8-TX] board.

The air that gets between the water and the trampoline is compressed and must decompress and is pushing back, so you're riding an air cushion that is tempered by a smooth surface.

So, there's all that kind of stuff.

I put this in an article 30 years ago on Surfer Magazine.

I imagined the guy mixing in his final gloss coat on the board. Actually, the final coat on a surfboard today is floor polish - Mop & Glo and that kind of stuff, which is aliphatic polyurethane.

So, you mix it with water and, with a sponge, you spread all over your surfboard and clean its bottom and use mom's finish floor wax diluted with water, which gives it a certain sheen to the scratched bottom.

But you can also do that with some mixture of Alka Seltzer.

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1 hour ago, Foredeck Shuffle said:

 

53. SKIN FRICTION
A boat shall not eject or release a substance, such as a polymer, or have specially textured surfaces that could improve the character of the flow of water inside the boundary layer.
 
But if this were effective I would have expected something like the AC to change this rule to suit their needs.  That the AC has never done so says that their tests in CFD and scale model tank tests have not produced useful results.

It has been done on rowing boats and research shows a measurable drag reduction (https://www.delta.tudelft.nl/article/shark-skinned-rowing-boats#). The only time I actually saw an eight with the textured finish was at Henley, and the crew who used it said that is was very easily damaged, they did not win..... I think that was the year that Queen's Tower/IC won the grand.

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On my Olson 30 , I would use Baltoplate, , worked pretty good for 1/2 the season. then had to start wiping the bottom down with a t-shirt

Would apply then wet sand 100 grit , 200 grit 400 grit , then use bronze wool to buffet it out

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Baltoplate isn't available in CA anymore, not sure about other states.   Same goes for Proline 1088c + graphite.   Both of those were on my boat prior.  One of the few compatible paints I found and recently tried was Pettit Black Widow which can be sanded/burnished/polished to a glossy surface.   I didn't go that far but the whole deal got 400g and progressively higher grit to the bows 1000g currently. 

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21 minutes ago, solosailor said:

Pettit Black Widow

yup. replaced my vc offshore with this. it works very well both as a racing paint and an antifoul, at least where I am.

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On 11/15/2021 at 5:03 PM, GH41 said:

I am no rocket scientist but it seems to me like a wet sanded bottom would break the surface tension better than a slick one and be faster.. Why do golf balls have dimples? 

Surface tension is irrelevant as there is no free surface under water. And golf balls have dimples to trigger the laminar to turbulent transition which is exactly the opposite of what you want on a hull.

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7 hours ago, JMOD said:

 

2. Sand in the direction of the water flow with 350 400

 

Have to be careful here if you are sanding in a deliberate pattern.

From RRS Q&A 2009-029 (L005) http://www.sailing.org/tools/documents/QABookletJune92010-[8951].pdf

Quote

53 SKIN FRICTION
A boat shall not eject or release a substance, such as a polymer, or have specially textured surfaces that could improve the character of the flow of water inside the boundary layer.
Question:
Does finishing a hull using wet & dry sandpaper break rule 53 '...specially textured surfaces that could improve the character of the flow of water inside the boundary layer.'?
Answer
No.
Specially textured surfaces have a deliberate pattern. Normal sanding produces a random pattern

 

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20 hours ago, Rasputin22 said:

.. you have about 30 seconds of turbo bubbles on the bottom of the board to decrease your drag through the water until the fizzy action dies out. Or you die when the wave pounds you into the reef. 

    I googled that concept and lo and behold it turns out to be an idea from Tom Morey (RIP).

¯\_(ツ)_/¯

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On 11/15/2021 at 9:32 PM, Sail4beer said:

You got that right. Learn the boat and the routine(mistake management) and the bottom can be ablative, gelcoat or burnished Baltoplate and you will still be way ahead of the competition.

Right up until you're trying to hold a lane off the starting line and your straight line speed drops you into the second row and a clearing tack - perfectly executed due to your practice - to the wrong side of the course.  

If you're going to practice your ass off, you had best do it on a well prepared boat.

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  • 2 weeks later...
On 11/16/2021 at 10:48 PM, JMOD said:

I like the idea. 

 

these are answers I received a couple of years ago on fast antifouling/bottom. especially part 2 which was apparently from someone who did the research for some America's cup syndicates.

1. Wipe the surface down with Fiberglass Solvent Wash 202
2. Sand the surface with 80 grit paper
3. Remove all sanding residue with Fiberglass Solvent Wash 202
4. Fill all damaged areas with Watertite Epoxy Filler
5. Sand the Watertite with 80 grit paper
6. Remove all sanding residue with Fiberglass Solvent Wash 202
7. Apply 2 coats of InterProtect 2000E
8. Apply 3 coats of VC Performance Epoxy
 
However if the blisters were deeper, where they would have broken into the laminate, then it would be best for you to fill the areas with a clear epoxy resin first to seal the laminate off and then proceed along with the system mentioned above. This system would best be followed as:
1. Wipe the surface down with Fiberglass Solvent Wash 202
2. Sand the surface with 80 grit paper to open up all of the blisters
3. Seal the laminate off with 2-4 coats of a clear epoxy resin (maybe Epiglass or West System)
4. Wash the epoxy with warm soapy water and a stiff brush
5. Sand the epoxy with 120 grit paper
6. Remove all sanding residue with Fiberglass Solvent Wash 202
7. Fill all damaged areas with Watertite Epoxy Filler
8. Sand the Watertite with 80 grit paper
9. Remove all sanding residue with Fiberglass Solvent Wash 202
10. Apply 2 coats of InterProtect 2000E
11. Apply 3 coats of VC Performance Epoxy or 2-3 coats of your desired antifouling paint
 
As for the potential overlapping, if you are using a two component topside finish such as Perfection above the waterline, then I would have no issue with you applying the Perfection overtop of the VC Performance Epoxy or vice versa. However if you were using a one component topside finish such as Brightside above the waterline, then I would recommend that you only allow the Brightside to overlap the VC Performance Epoxy and not vice versa. The main reasoning would be the aggressive solvents which are in the VC Performance Epoxy will dissolve the Brightside if applied overtop, as where there will be very little to almost no adverse reaction if Brightside were applied overtop of the VC Performance Epoxy. 
 
 
I have had good luck with Interlux performance expoxy. Wet sands easily. My 10 year old bottom is still as white as new and glossy as gelcoat. 600 grit is as fair as I go, but for the heck of it, I did take the bulb down to 1200 and it shines. I put overtop a few layers of IP2000e
 
PART 2
 
ther are several, which as mentioned above, i cannot mention due to certain bit of paper.

In essence, we built a series of hi tech devices (water flow) that measured the friction of hundreds of coatings and applied film systems from durepox to PTFE to Graphite to syloxines to silicones etc... You name it we tested it.

We were even involved with clear coatings for red and white cricket balls to make them last, shine, and have consistant flight etc... But thats another story for ..sails and spars

d,urepox is ok for a cost effective " retail" system however if you want a faster system there is one i can give you that i explained in a previous post. Andnits relatively cheap.

This applies to gel coated, urethaned and durepox surfaces.

1. Guide coat hull, rudder and keel.

2. Sand in the direction of the water flow with 350 400

3. Apply Kisscote as per directions. ( its not cheap but you dony need much.)

4. Go faster!

This was a top ten system.

There were a couple of standouts in the top ten and many that were very close to each other. 

Can I ask your opinion on Seaspeed V10X, or should I ask would you use it yourself ?

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On 11/16/2021 at 2:40 PM, Howler said:

Hah... this is an endless conversation at yacht club bars, where everyone becomes a fluid dynamics expert. 
 

  1. The only thing that matters is surface smoothness. And it matters a lot. On this the MIT scientists and the legendary Bethwaites agree: Sanding to 3000 grit and polishing to mirror finish is faster than 800 grit.
  2. It is as a practical matter impossible to make a hull smooth enough that  laminar flow stays attached the entire length of the hull. It invariably breaks into turbulent flow a little bit back from the bow.  The smoother the surface, the longer the laminar flow stays attached and the more of the hull experiences laminar flow and the less of the hull experiences turbulent flow. Laminar flow is faster than turbulent flow.
  3. Dimples on golf balls and those rows of little tiny guitar pick sized tabs on the top of airplane wings are designed to generate turbulence, on the theory that predictable turbulence behaves better than unpredictable turbulence.
  4. Air and water behave very differently: water is incompressible, and a lot thicker than air. What works on golf balls and airplanes may not work on boats.  People have been experiencing with "shark skin" type deliberate roughening of boat hulls for a while, but nothing practical has come out of it yet.   Web searching "reynolds number" will lead you down interesting rabbit holes.
  5. The water molecules closest to the hull don't slide along the hull; they stay stuck to the hull right where they are. The water molecules further from the hull slide over those stuck water molecules. Web searching "no slip condition" will lead you down other interesting rabbit holes.
  6. "Surface tension" is really about the interaction of water and air; it doesn't really have an impact on the flow of water over a submerged hull.
  7. The chemical composition of the surface doesn't matter, only the smoothness. (The chemical composition matters to the extent that it contributes to smoothness, i.e., to the extent that it hard and resists microscopic dents, or that it is soft and mushes around to smooth over microscopic dents after they form.

My understanding is they are vortex generators and are designed to be placed upstream of seperation with the intention to pull energized air into the boundary layer to delay the point of seperation. I had wondered how they would work in water and came up with the thought that a reasonable hull probably doesn't experience seperation. Not sure if this is right?

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On 11/17/2021 at 2:21 AM, Foredeck Shuffle said:

 

53. SKIN FRICTION
A boat shall not eject or release a substance, such as a polymer, or have specially textured surfaces that could improve the character of the flow of water inside the boundary layer.
 
But if this were effective I would have expected something like the AC to change this rule to suit their needs.  That the AC has never done so says that their tests in CFD and scale model tank tests have not produced useful results.

 

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