Fast Bottoms

I use a marine polish, not wax, to seal in the pores on a wet sanded gel coat. With the polish there is much less staining of the hull due to water pollution such as the occasional oil blob. As for speed, I sincerely doubt that you will be able to tell the difference between a polish applied on a wet sanded gel coat and the same wet sanded gel coat without polish. Recent tests on a laser centerboard indicate that anything beyond a 400 grit sanding is a waste of effort.

I have tried it both ways and am now of the opinion that waxing does work. Here's why I believe this: First, the topsides were already waxed, per conventional wisdom and recommendations from the factory. Second, the topsides are partly immersed much of the time when sailing, particularly when sailing to windward. So if a substantial part of the hull is under water at any given time, and if it is waxed, then there is a dis-connect on the wax-the-topsides-sand-the-bottom-meme. If we wax the topsides, then why not the bottom? Or if we wet-sand to 400 on the bottom, why not the topsides, too? I decided to try the wax-it-all approach. I think it's faster, but not for the reasons that usually get discussed over post-race beer sessions. People think that you get either beading on a waxed surface or a nice smooth, lubricated boundary layer effect with the 400 wet-sanded surface. (I used to believe this and have said so on more than one occaision) Neither is true. These are phenomena which occur on the surface when the boat is exposed to air (a different fluid). The water beading effect doesn't apply when the boat is in the water. Put on a diver's mask and look under your boat when afloat. You won't see any beading there on a waxed bottom. Likewise, if you touch a 400 surface under water, it doesn't have that slippery "boundary layer" that you feel when the boat is out of the water. I believe that any reduction in skin friction (aka "faster") is due to the bottom being cleaner. This is a result of the waxing process (I already wet sanded). There is less stuff on the bottom to cause drag. You get the same water spots on the hull as you would on your car if you just hosed it off without toweling or chamoising the surface. Those minute mineral deposits will slow you down, so if you clean them off, you reduce skin friction. My sense is that waxing minimizes the spotting, makes cleaning & wiping easier, and contributes to a smoother surface. Wax, or a good teflon polish, is not inherently slower or faster--it just keeps the hull surface free from many of the imperfections that most people are sailing around with anyway.

I think Gallus' thining is partly correct but partly flawed. Yes, cleaning the bottom is key. However, the argument about the wet sanding does not address the core argument for those in favor of it. Their argument is that AS THE BOAT MOVES there is a layer of water that adheres to a rough sanded bottom. That layer then functions like a wax over which the rest of the water travels. Therefore, you will not feel a slippery bottom to the hull when the boat is stationary--only if it moves will you get the effect of water sliding over water. I however do not know if anyone has ever tried to measure this effect, and compare it to a waxed bottom.

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[i]Originally posted by FS4019[/i] [br]Frank is right - some people refer to this at the "golf ball effect". The dimples (or small scratches in this case) are what make it fly. Byron Jamerson FS 4019

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The dimples on a golf ball are a special condition that applies to a spherical surface. The dimples trip the boundary layer and facilitate an earlier re-attachment of the flow. This results in less drag than if the golf ball were perfectly smooth. The seam patterns on baseballs and tennis balls achieve the same effect, but in a different distribution. Refer to Bethwaite (High Performance Sailing) on page 269---he basically says you can't get a hull polished enough. I'll defer to him as he has run the tests and I haven't. I plan to try the teflon based polish, as Doc (and others)recommends.

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[i]Originally posted by frank barbehenn[/i] [br]Gallus...who's Doc?!

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That would be Doc Bellows, who posted earlier under ltxsbf.

that's what I had read and was saying earlier. but does anyone know of anyone who has tested these ideas?

Is it not against class rules to use the teflon starbrite on a scot? If I remember correctly the head measurer told me no at the NACs to that stuff. Travis Weisleder 5341

Does Starbrite teflon last "less than one year"? Could be debated. Phil Scheetz FS 4086

FSSA Handbook ARTICLE S-V - RACING RESTRICTIONS 3. No temporary coating of grease, graphite, pot lead, etc. is allowed on the hull, center-board or rudder. Waxing of the hull, centerboard and deck may be done at the option of the owner. (See also CMR’s #28 & 72) CMR #28. Any bottom coating which is represented by the manufacturer as designed to last one season is not a "temporary coating" and therefore not prohibited under the provision of S-V-3. CMR #72. The use of any liquid soap, detergent, soap or any such wetting agent applied to coat the hull , centerboard or rudder is prohibited under the provisions of S-V-3. Any such material may be applied to clean the hull, but must be removed (squeaky clean) prior to launching the boat. (March 1994) Phil Scheetz FS 4086