Snails trails

[Jamestj]

Fish are slimey, presumably so that they can swim faster. An organic slime can be introduced in an emergency into storm drains to make the water flow quicker to prevent flooding. Covering the hull of an IOM would presumably make it sail faster. I would like to know
1) is it legal?
2) if so, where can you get slime apart from encouraging snails to wander over your bottom?

Thanks,
Joker ?

[Steve Landeau]

A coating is legal so long as it does not come off as the boat sails. This is covered in the RRS. Other class rules may prohibit certain coatings as well, but the IOM does not, so long as you satisfy the RRS.
I have no idea where you can get slime

[Arvin S.]

I have been considering this theory for some time too (years) so far what I understand is that people (specially big boats sailors) tended to just make sure that their hulls are clean and smooth as possible. There are even anti fouling specially formulated to combat slime and algal slime which is considered to create drag.

The problem is probably that you cannot ensure that the slime coated on the hull in such as way that it still gives a consistent hull shape without introducing drag.

I am not an expert about fishes, but in my opinion fishe have slime to protect themselves from parasites, etc. and not for hydrodynamics. Even so most of ideas coming from fishes, and other animals to help improve speed are great ideas in my opinion but sometimes are just so difficult to apply on boats, big and small.

Consider one idea of using the small "shark scales" to improve hydrodynamics on a big boat hull. I don't know what came out of it but one thing is for sure we do not have any main stream boat out there claiming that they are faster because they have a "shark scale" surface.

So the simplest way to go about hulls and speed is to keep it really nice and clean, waxing is okay (as long as it complies with the RRS) but for our small boats, I think that is the only realistic way to ensure your hull is ready to race.

TTFN
Arvin

[Jamestj]

Should the surface be easily wetted as if washed with soap or should it be unwetable as if polished with wax?

I have noticed that although the exhaust manifold of some cars is polished to a mirror finish, the inlet manifold was given a smooth matt finish. I understood that the mirror finish was to prevent carbon from building up but the ideal surface was mat since a boundary layer caused by the microscopic dimples was less lightly to form eddies when air swepped through the pipe.

Do I polish the hull with car wax or rub it down with cream cleaner?

What is the consensus please?

[Chairman]

A coating is legal so long as it does not come off as the boat sails. This is covered in the RRS.

Hi Steve

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.

I just love RRS 53, because I think I "specially texture" my hull surface every time I carefully sand it with wet 'n dry (longitudinally only, not athwartships), never mind carefully choose whether I'm then going to apply Rain-ex or a wax coating... Do I ever want to improve the boundary layer!

[edmorales]

i wax my boats mainly because i sail in salt water.it helps protect the paint from salt build up,nothing else. i dont notice any speed increase(all of them are dogs )

[Arvin S.]

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.

Wow Lester you know this is the first time I actually have come upon RRS53! I didn't know there was a stipulation against this.

On the other hand aside from what your mentioned wet sanding your hull (which I understand is not against the rules), can you please give an example of something that actually IS against RRS53?

I wonder if "shark scales" surface actually violates this rule? Or how about actually making small groves longditudinally or maybe even athwartship to create eddies?

In my unscientific opinion however, any bumps and dimples on the hull will create drag on water that the best way is to get as smooth a hull as possible, sometimes aerodynamics is not directly the same as hydrodynamics, and in my opinion air eddies and ventury making surfaces might not work in the same principle if it's water that is flowing.

Then again I am to talk I have a hull that is full of pits and bumps coz I am too lazy to wet sand it. This is a good topic to get started doing it.

TTFN
Arvin

[Chairman]

On the other hand aside from what your mentioned wet sanding your hull (which I understand is not against the rules), can you please give an example of something that actually IS against RRS53?

Hi Arvin

As Steve has said, anything where something comes off is not legal. "Of course", "everyone knows" that sanding isn't against the rules... But if I take 100 grit, and carefully "sand" my hull longitudinally only, just once, I have created (let's imagine!) a set of longitudinal grooves. Now such grooves have a profound effect upon the boundary layer. Just like the latest swim suits that the olympic swimmers wear, apparently so good for reducing drag that they'll take up to 0.5 sec a lap off your pool times... We don't know if this in fact works for our toy boats, but it illustrates my concern -- I'm not too sure that sanding your hull is, very strictly speaking, allowed by RRS 53!

[RoyL]

The provision regarding textured surfaces can be understood in its historical context. When Dennis Connor won back the America's Cup in 12 meters, Stars and Stripes was covered with a grooved 3M film that was claimed to enhance the flow of water over the hull surface and reduce drag. The change in the racing rules banning textured surfaces was enacted after these races and in reaction to this film. It was never intended to ban wet sanding.

FYI, years ago I obtained samples of the film from 3M and tried it on a Marblehead. Didn't help, 3M explained that the groove size in the film was proportional to the size of the boat; the film they made for DC was accordingly way too big for our boats.

[Arvin S.]

Thanks Lester and RoyL for your replies.

Oh, so is that what happend to the "shark surface" idea, it got shot down by RRS! Too bad, then again it is nice to know that all you have to do is spend time sanding your hull rather than pay for the 3M surface to be competitive. Wow Roy you actually got a sample from 3M, wonder if they are still available. I do agree with their analysis though that the advantages is also scaled down, in fact the same surface might make too much of a drag on say an IOM

Lester I hope no one sees these posts about longitudinal sanding and comes up with a new RRS53 rule that sanding has to be in circular motion to provent such kinds of grooves.

TTFN
Arvin

[Jamestj]

Thanks for your reply, RoyL

It seems that when fluid flows gently, then turbulance is not a problem and skin friction can be significant. Therefore coating the hull with polish would be an advantage.

At higher speed, turbulence is significant and a textured mat finish would reduce drag by increasing the thickness of the boundary layer.

This would tie in with fast moving fish (which tend to be large), such as sharks having rough skins. Slow ones, such as goldfish, (although fast for their size) being smooth.

Perhaps we would need mat hulls in windy conditions and polished hulls in light air!

I eventually found a slug and put the unfortunate creature on a smooth sheet of grp. It obligingly decided to escape at a sluggish speed leaving a trail. I found that water drizzling down the sheet would form a fine film when it ebncountered the trail and run off the sheet more easily.

I suspect that the goo left behind behind the slug would probably improve water flow on a IOM hull.

I have discovered an aqueous gel which would have the same effect. This is more practical since slugs aren't particularly co-operative. It can form a thin coat on GRP, show no measurable inclination to dissolve in water yet, does itself absorb water.

If a hull was painted with such a gel, would it be legal? After all, the gel does not dissolve in water - the water dissolves in the gel. After immersion in water, the weight of the hull actually increases since water has been absorbed.

I coated the inside of a beaker with the gel and added distilled water. After an hour I tested the distilled water for contamination by comparing its electrical conductivity. There was no significant change.

Since this polymer does not dissolve and is not textured then it complies with RRS 53 (see comment by Arvin S.) and therefore would be allowed under the IOM rules. If this were not the case then polishing and sanding would not be permitted.

Any thoughts please?

[johnw]

FYI- These are perfect examples of what you're talking about. I'll leave the legal interpretations to the lawyers.

http://hyspeedkote.com/

http://www.dolphinite.com/products_bottom_coating.htm
(then click "Go-Fast Speed Bottom Coat".)

-John W.

[Arvin S.]

Thanks for sharing this info john,

The dolphinite website is down unfortunately.

Anyways I thought that the hyspeedkote might actually be legal coz they were used during a sailboat race, then when I checked out the Worrel 1000 website I realised that it really isn't a fully under ISAF RRS. It's basically a private race and thus will not help us determine if the product is legal or not.

However the product claims:

Hyspeedkote? is a water insoluble polymer coating that actually holds a continuous film of water on underwater surfaces. The resulting effect of water against water reduces resistance (drag) and increases efficiency, offering one or more of the following benefits:

So in the RRS rules that were mentioned below, I can't see any reason that the product can be deemed illegal. It does not come off the boat while sailing coz it's "insoluble", also it does not create a " textured surface". Of the two I think the most important point to prove is that the product really does not get ejected or released.

TTFN
Arvin

[Chairman]

A very characteristic comment from Graham Bantock:

Do not apply any wax or other surface treatment in an attempt to reduce skin friction - the only ones that work are not permitted under RRS 53. The commonly available static friction reducing polishes only increase the likelihood that you will drop your yacht.

[Jamestj]

RRS 53 could be accidentally contravened by buffing up the hull if a waxy mold release agent had been left behind on the resin surface of a grp hull or if the hull was sanded down lenghtways. It can be deliberately contravened by dusting an invisible layer of hydrophylic compound over the hull.

If RRS 53 was designed to keep the price of the IOM down, the retail cost of applying a hydrophylic film works out at 1 euro per hull.

I feel uncomfortable with RRS 53 but in the interest of conscience, would not contravene this rule though I doubt that it could be policed.