Fast Bottoms

The gelcoat on my boat is in good shape, with only a few minor scratches. I'm looking to roll her over next week and fill them all in. After fixing scratches, one would think that a good compounding and then a coat of wax would be a good idea. The problem is that I have heard that gelcoat that has been waxed is actually slower than one that was not waxed. So what do you think? What makes the bottom the fastest? I've heard of simply wetsanding, and I have also heard of some other products that should be used rather than wax. Thanks for your input 3873

Comments

Wax is slow,water beads on a waxed surface because it can "get a

Wax is slow,water beads on a waxed surface because it can "get a grip" Compounding leaves a simular waxy surface. Wet sanding with at least 600 grit is faster. Be sure to use a sanding block and long strokes parallel to the keel. Products that "last less than 1 year" are illegal. Bob New

I use a marine polish, not wax, to seal in the pores on a wet sa

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.

quote:[i]Originally posted by bobnew[/i] [br]Wax is slow,water

quote:
[i]Originally posted by bobnew[/i] [br]Wax is slow,water beads on a waxed surface because it can "get a grip" Compounding leaves a simular waxy surface.
Are you sure that this is not backwards? From what I remember of fluid mechanics and physics is that a low friction surface allows liquids to bead because their surface friction is lower that the surface tension of the liquid. The liquid will seek to form (as close as possible) a sphere (look at what liquids do in zero-g environments where the "surface" is air) since the sphere has the least surface area for a given volume of liquid. What about all of those surfers and skiers who seem to always be looking for a faster wax? Wouldn't some of them have tried no-wax? As usual, I could be completely out in left field. dave boling dave boling Huntsville, AL FS3431

I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

I have tried it both ways and am now of the opinion that waxing

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.

In my experience with trying to race club boats over the years a

In my experience with trying to race club boats over the years and wetsanding far to many boat bottoms, the last boat I purchased from Karen and Harry I took delivery of, brought home and polished the hull with teflon polish made by starbrite found at west marine. Helps prevent discoloration from minerals in the water and have had no problems with boat speed. Doc Bellows

I think Gallus' thining is partly correct but partly flawed.

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.

Frank is right - some people refer to this at the "golf ball eff

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

quote:[i]Originally posted by FS4019[/i] [br]Frank is right - s

quote:
[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
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.

Gallus.

Gallus...who's Doc?!

quote:[i]Originally posted by frank barbehenn[/i] [br]Gallus.

quote:
[i]Originally posted by frank barbehenn[/i] [br]Gallus...who's Doc?!
That would be Doc Bellows, who posted earlier under ltxsbf.

Waxing? (.

Waxing? (..I don't mean Brazilian guys[:X] ) I use Starbrite Teflon on our bottom. Granted wax is hydrophobic and not considered fast, I still think a clean slick bottom is the way to go. I'm just too lazy to sand the bottom before every big event. Besides on most of our inland Texas lakes your bottom will turn an ugly stained off-white if you don't wax. I'm sticking with Starbrite Teflon wax. And now the flip side, sanding...... Many championship sailors seem to lean towards wet sanding 600 grit, then 1200 grit, and some all the way to 2000 grit. The theory is that a smooth sanded bottom allows for hydrophillic and hence promotes lamilar flow of water molecules running over molecules on the bottom of the boat. Essentially, the sanded bottom attracts and holds a super wet layer of water molecules over which the ultimate layer of water molecules speedily slide across ....hence a fast bottom boat!

Michael Mittman

FS 5804, Fleet 23

Corinthian Sailing Club

White Rock Lake, Dallas, TX, USA

that's what I had read and was saying earlier.

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

at the risk of sounding like some kind of fanatic (maybe i am),

at the risk of sounding like some kind of fanatic (maybe i am), i would refer to frank bethwaite's HIGH PERFORMANCE SAILING . he provides a well-reasoned theoretical, then practically tested, analysis of bottom and foil prep. the information provided completely changed my mind about the subject and dispelled many day to day misconceptions. once read, i doubt that many would adopt any other theory at current levels of knowledge. (note that some of the info would be illegal under scot rules, but much of ti could be applied).

Is it not against class rules to use the teflon starbrite on a s

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 not the proscription against bottom coating refer to ablati

Does not the proscription against bottom coating refer to ablative coatings? How exactly would a scrutineer detect a layer of teflon-based polish that builds up to a layer of no more than one or two thousandths of an inch? dave boling Huntsville, AL FS3431

I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

Does Starbrite teflon last "less than one year"? Could be deb

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

Phil Scheetz

FS 4086

Fleet 163, Nockamixon Sail Club

I am new.

I am new.....so what is the rule about a year?

Marv Pozefsky

FS 733

FSSA Handbook ARTICLE S-V - RACING RESTRICTIONS 3.

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

Phil Scheetz

FS 4086

Fleet 163, Nockamixon Sail Club

I hear ya, but I can only repeat what I was told.

I hear ya, but I can only repeat what I was told. I think the rule was silly...I think I will email him again and ask for it in writing.