hull preparation

[Birdseye]

what do you do, if anything, to prepare your hull for a race?

 

[DFL1010]

Depends on a) the race, and 2) the condition it's in.

If you did it properly in the winter, then a lift and pressure wash is fine.

If not, then lift, strip off old anti-foul, long-board for fairness, check the foil profiles (and reprofile if needed). Then re-antifoul and burnish. This is, of course, assuming you don't drysail, in which case it's polish time (although opinion differs on how smooth to make the hull - some research suggests that supersmooth is not superfast).

But, like I say, what's the race? I'd do all/most of that for Fastnet/Middle Sea Race/similar.

Club racing, not so much (but do quite a bit over the winter and lift/clean 2-3 times through the season).

 

[DFL1010]

Above the W/L: strip winches; mouse out halyards and replace as needed; clean and one-drop (or replace) blocks, travellers, jib tracks, etc etc; thoroughly inspect the standing rigging; and think about pulling the stick. Touch up non-skid as req'd.

Polish hull topsides.

Again, depends on the race, and the state of the boat and Planned Maintenance schedule.

 

[mrming]

For club racing I just make sure we have a scrub every 4-6 weeks. The bottom is pretty fair and coppercoated. The idea was to do a good job once and put on a tough finish that can handle regular scrubs. The antifouling properties aren't great in our brackish water, but we scrub so regularly it doesn't matter.

 

[lpdsn]

what do you do, if anything, to prepare your hull for a race?

I presume you'd not have the time for a decent level of preparation, with full long-boarding etc, but it would be worthwhile flatting the anti-foul on the keel and rudder with say 400 grit before you go back in the water. Concentrate on the leading edges.

 

[Birdseye]

Curious for two reasons. First is a club member who sprays on his antifoul every year and then flats it with what liikes like 800 grit wet and dry. Looked like a ridiculous amount of effort but then he is an habitual one make winner.
Second reason was that I did a simple trial myself last year. Unintentionally as it happened , I did a speed trial under engine before I lifted and washed and afterwards . Surprised by the difference given that the hull was simply a bit slimy with no crustaceans

 

[Marine Reflections]

Curious for two reasons. First is a club member who sprays on his antifoul every year and then flats it with what liikes like 800 grit wet and dry. Looked like a ridiculous amount of effort but then he is an habitual one make winner.
Second reason was that I did a simple trial myself last year. Unintentionally as it happened , I did a speed trial under engine before I lifted and washed and afterwards . Surprised by the difference given that the hull was simply a bit slimy with no crustaceans

If he did no more than to flat the antifoul I would have thought IMO that this would work against him.

To get an object to travel through water faster or more efficiently it would need to be hydrophobic, flatting of the antifoul would make it more hydrophilic, it would grab the water.

There is an published experiment online somewhere, where they coated a golf ball with a hydrophobic coating and dropped it through a tube of water with gate sensors to measure how fast the ball fell through the water. Did the same with a hydrophilic one and the results were conclusive that the hydrophobic one was quicker.
This was through tap water though so possibly it may have a different effect through salt water, who knows.

Would love to have test facilities at my disposal and start adding some coatings with antifouling to make a super slippy coat.

One aspect that would be great to achieve is to imprint the mould of a hull with a micro finish such as that on a sharks or tuna skin, when the hull was popped out of the mould it would have a finish that would cut through the water faster than any coating.

 

[lpdsn]

If he did no more than to flat the antifoul I would have thought IMO that this would work against him.

To get an object to travel through water faster or more efficiently it would need to be hydrophobic, flatting of the antifoul would make it more hydrophilic, it would grab the water.

There is an published experiment online somewhere, where they coated a golf ball with a hydrophobic coating and dropped it through a tube of water with gate sensors to measure how fast the ball fell through the water. Did the same with a hydrophilic one and the results were conclusive that the hydrophobic one was quicker.
This was through tap water though so possibly it may have a different effect through salt water, who knows.

Would love to have test facilities at my disposal and start adding some coatings with antifouling to make a super slippy coat.

One aspect that would be great to achieve is to imprint the mould of a hull with a micro finish such as that on a sharks or tuna skin, when the hull was popped out of the mould it would have a finish that would cut through the water faster than any coating.

In that case if you could get everyone to lash the AF on with a brush I'm sure the rest of the racing community will be enternally grateful.

 

[Marine Reflections]

Dont understand lpdsn??
Grateful that AF not being sprayed, or that a brushed AF would be slower?

I can understand sanding the AF would the reduce drag by taking off any nibs etc, but the effort might be undone by making the hull more hydrophilic and creating drag in that regard?

Only a consideration for serious racers though I'm sure.

Are there any rules when racing as to what you can do to the hull to improve flow through water?

 

[lpdsn]

Not sure I understand?

I was just gently ridiculing your advice not to flatt the anti-foul. I though all those debates on smooth Vs rough surface preparation had been concluded years ago.

Your sharkskin gel coat idea might be good for a fast cruiser, if it works, but until they make significant changes to RRS53 it's a non-starter for racers.

 

[Marine Reflections]

I was just gently ridiculing your advice not to flatt the anti-foul. I though all those debates on smooth Vs rough surface preparation had been concluded years ago.

Your sharkskin gel coat idea might be good for a fast cruiser, if it works, but until they make significant changes to RRS53 it's a non-starter for racers.

Ah, I'll consider myself gently ridiculed

Wasn't offering advice, just an opinion.
I had it that a smooth surface goes through water faster yes, but like most things there's always room for further debate.

Smooth versus rough I can understand, hydrophobic versus hydrophilic should also be considered though yes?

It's an interesting subject as the skin of a shark is not smooth, it is rough.

Edit: RRS53 ? is that a rule?

 

[Marine Reflections]

Ah, I see that it is indeed a rule. But does that not mean that 'conditioning' of the skin - i.e. sanding for example would also be a breach of the rules?

How much fettling can one get away with before another team cries cheat?

 

[lpdsn]

Ah, I see that it is indeed a rule. But does that not mean that 'conditioning' of the skin - i.e. sanding for example would also be a breach of the rules?

How much fettling can one get away with before another team cries cheat?

The ISAF rule outlaws specially textured surfaces. The RRS would apply to nearly all racing regardless of handicap system - there are exceptions like the America's Cup which would race under their own modified version of the rules.

Sanding (long-boarding) is generally accepted as OK. That said, we strongly suspected that we were penalised up to 6 points under IRC for longboarding a boat. They never confirmed it but they did point out that they considered long-boarding a production cruiser as a modification, so we felt we got some penalty. Presumably it is assumed that a purpose built racer would be long-boarded already so no effect on rating if you do it again.

Incidentally, the production cruiser didn't have anti-foul applied after we long-boarded her, we waxed and polished the hull, so were getting close to your hydrophobic surface (without reliquishing anything on the smoothness of the surface argument). We certainly felt she was faster, but she did have to be dry sailed and the owner gave up on that after about half a season.

 

[lpdsn]

I had it that a smooth surface goes through water faster yes, but like most things there's always room for further debate.

The smooth surface delays the switch from laminar to turbulent flow, so it's not just about being faster, but also about the extra lift from foils. Hence my advice a few posts ago that if the OP didn't have the time/money/inclination to put in a massive amount of effort on boat preparation, smoothing the keel somewhat gave the most advantage for a moderately small amount of effort.

 

[Marine Reflections]

The ISAF rule outlaws specially textured surfaces. The RRS would apply to nearly all racing regardless of handicap system - there are exceptions like the America's Cup which would race under their own modified version of the rules.

Sanding (long-boarding) is generally accepted as OK. That said, we strongly suspected that we were penalised up to 6 points under IRC for longboarding a boat. They never confirmed it but they did point out that they considered long-boarding a production cruiser as a modification, so we felt we got some penalty. Presumably it is assumed that a purpose built racer would be long-boarded already so no effect on rating if you do it again.

Incidentally, the production cruiser didn't have anti-foul applied after we long-boarded her, we waxed and polished the hull, so were getting close to your hydrophobic surface (without reliquishing anything on the smoothness of the surface argument). We certainly felt she was faster, but she did have to be dry sailed and the owner gave up on that after about half a season.

Interesting that they would outlaw specially textured surfaces, do they know something?

My interest really is in 'Super' hydrophobic surfaces - surfaces that have a contact angle of surface tension of more than 150º

Past 150º a water droplet won't just land on a surface, it will bounce.

Given the experiments mentioned in previous post regarding a golf ball travelling through water (with or without a hydrophobic coating) I wonder how far the boundaries can be taken.
I mean, was the test done with a coating that could achieve 150º or was it simply hydrophobic (greater than 90º) I'm certain the results would differ dramatically.
This would have significant consequences not just for speed but also for fuel costs on a tanker for example.

Of course as you point out, the normal problems of maintaining a certain condition once achieved still apply. Which is why my thinking is down the path of printing a condition onto the skin rather than applying a coating or conditioning an existing one.

Pressed copper coat with microscopic fins ?

 

[Ingwe]

My interest really is in 'Super' hydrophobic surfaces - surfaces that have a contact angle of surface tension of more than 150º

Past 150º a water droplet won't just land on a surface, it will bounce.

Given the experiments mentioned in previous post regarding a golf ball travelling through water (with or without a hydrophobic coating) I wonder how far the boundaries can be taken.
I mean, was the test done with a coating that could achieve 150º or was it simply hydrophobic (greater than 90º) I'm certain the results would differ dramatically.
This would have significant consequences not just for speed but also for fuel costs on a tanker for example.

Of course as you point out, the normal problems of maintaining a certain condition once achieved still apply. Which is why my thinking is down the path of printing a condition onto the skin rather than applying a coating or conditioning an existing one.

You can already get extreme hydrophobic anti foul in the form of Aqua Cote antifoul it gives the hull a soft silicone style finish that lasts- think of a silicone cooking utensil but applied over the bottom of a hull ! Or I know some dry sailed boats now use things like "eel snot" which is more like an extreme hydrophobic hull polish so has to be regularly re applied.

 

[lpdsn]

Interesting that they would outlaw specially textured surfaces, do they know something?

My interest really is in 'Super' hydrophobic surfaces - surfaces that have a contact angle of surface tension of more than 150º

Past 150º a water droplet won't just land on a surface, it will bounce.

Given the experiments mentioned in previous post regarding a golf ball travelling through water (with or without a hydrophobic coating) I wonder how far the boundaries can be taken.
I mean, was the test done with a coating that could achieve 150º or was it simply hydrophobic (greater than 90º) I'm certain the results would differ dramatically.
This would have significant consequences not just for speed but also for fuel costs on a tanker for example.

Of course as you point out, the normal problems of maintaining a certain condition once achieved still apply. Which is why my thinking is down the path of printing a condition onto the skin rather than applying a coating or conditioning an existing one.

Pressed copper coat with microscopic fins ?

Generally these sort of rules are there to stop 'arms races' which push up the cost of racing. As I say, some special events or classes will modify the rules, but I'm unaware of one that modifies RRS53.

I suspect the microscopic fins would still probably count as a specially textured surface. I don't think there are rules on coatings, other than RRS53 banning the release of any substance, but it's usual just to wax and polish the hulls of dry sailed boats.

You could try contacting the Technical Dept at ISAF to get a bit of clarity around what is covered by the rule and which of your ideas it may or may not outlaw. ISAF are only the first hurdle though, as there is also the most common rating rule, IRC, which is managed jointly between RORC and the French. They typically over-penalise anything innovative. There's a well-known bloke called Mike Urwin who is the guru of IRC that you could try to contact.

 

[DFL1010]

AFAIK the shark's skin type was the reason why 53 reads as it does: they were used in the olden days in the AC (end of the 12s/start of the IACC, I seem to recall). The trouble was they are hard (i.e. expensive) to apply as they have to be aligned with the flow lines otherwise they slow you down, and they only work over a certain speed range (which was okay as they weren't exactly fast boats).

Either drysailing and using Hullkote, or burnishing a decent antifoul to 1200grit or so will suffice.

However, bear in mind that one fluffed tack, second lane start, or picking the wrong side of the beat will all be muuuch more costly than not doing the bottom to the nth degree.

 

[Woodlouse]

Last time I prepped the bottom of a race boat the travel hoist had a hard time getting a grip on the thing when it came to launch.

On the topic of releasing substances to increase speed, the 90 foot tri that oracle built for the 2010 fiasco had slits at the forward end of each hull that could release a polymer of some sort that would separate the water from the hull. I seem to recall they never used it in the cup it self, but trials showed an increase in speed of several knots.

 

[Pete7]

Powerboats have a stepped keel which in addition to some strategically placed vents causes air to be pulled down and released into the step reducing the drag. Perhaps sticking the dinghy pump down the bog and pumping like mad is the solution.