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Slippery bottoms are the key to go-fast sailing

2021 November 1

We were standing in the yacht club bar after the race when Jon arrived and grabbed my arm. “Were you just feeling her bottom?” he demanded, which turned every ear along the bar into little pointed tufts of attentiveness.

“What?” I asked with Oscar-winning innocence.

“Did you just run your hand across her bottom?” he repeated.

By now things were getting exciting in our normally staid club bar, but I can assure you, Dear Reader, that I did nothing that I couldn’t tell my mother. In fact, since my mother had also been racing that day, I think she copped a feel of George’s bottom too. 

Oh, I know what you’re thinking. Before this column gets out of hand you should know that I spend a great deal of time and effort on my own bottom and I hate it when someone else has a better bottom than mine. No, it’s not the musculature of a gluteus maximus, but the smoothness of the bottom of a sailboat. 

I admit that I did run my hand along the bottom of Jon’s boat, from about amidships to the transom, but it was just the lightest caress. Since he had thoroughly kicked my own bottom around the race course that day, I wondered if his bottom was slipperier than mine. 

Over the years that I’ve been racing sailboats both big and small and one area where I’ve spent a whole lot of time and money stands out. (It’s not sails. I just write a check to my sailmaker on a regular basis and that seems to handle that.) 

The bottom of a sailboat is, as they say in car racing, where the rubber meets the road. For many sailors, the boat bottom is just the thing that keeps the water out. For racing sailors, a smooth bottom is at the top of the list of stuff like food and breathing.

It seems so simple. Your hull bottom, whether you’re racing a 14-foot dinghy or a 60-foot ocean racer, should be slippery. Hydrodynamicists are those scientists who specialize in fluids, but they don’t use low-tech words like slippery. They prefer skin-friction drag and they pepper their conversations with profound stuff like boundary layers, laminar flow and turbulence

When I was racing fiberglass dinghies, there were two parts to my preparations before a major regatta. First, I would revarnish the tiller. Why? I haven’t a clue. It was clearly some sort of compulsion, because it had absolutely no bearing on my speed. I just felt better, and perhaps that’s a good enough reason. 

The second part was to flip the boat over and examine the bottom with the same care that my dermatologist is now checking my balding pate. Let’s just say microscopically. Any blemishes were lightly sanded out and chips were painstakingly filled. 

The next steps were to apply a thick paste of Simoniz car wax and buff it to a high sheen. It was only when I achieved a glossy hull and a glossy tiller that I was ready for combat.

Ah, youth. How little I knew. In my future would come friendships with various hydrodynamicists involved in the America’s Cup. When I mentioned car wax, their eyes rolled back.

The goal of making your hull slippery has nothing to do with how shiny it looks on the trailer. It’s about being hydrodynamically smooth, which is another can of worms entirely. Wax is apparently a no-no because it not only reacts with contaminants in the water to add drag, but it’s also not as smooth as progressive levels of wet sanding.

But, of course, there is a problem with wet sanding. The gelcoat on your hull is basically porous and if you sand through the outer layer, it will absorb water and that’s another no-no. 

Back in the day, I would finish off my carefully waxed hull with a thick layer of dishwashing detergent. I’d heard that it worked and, when you put it on your hands, it sure is slippery. Years later, my scientist friends got a good laugh from that idea, saying it did little more than get scum off the hull and was gone long before I reached the starting line. But I did feel good seeing a wake of bubbles, and the boat smelled great.

Then came the First Revelation of Bottoms: a smooth hull wasn’t the best. What you wanted was a slightly rough surface so that one layer of water would adhere to the hull. The theory was that water sliding past water is a lot slipperier (is that a word?) than water sliding past gelcoat or paint.

Skippers started applying slightly roughened surfaces, like the primer used on cars before the real paint was applied, to enhance the acquisition of a boundary layer. They cited dolphins and sharks, both of which have rough skins and both are darn quick in the water. Did that work? 


The scientific boffins soon recognized that a boat is not sliding across a mirror-smooth test tank, but bouncing up and down through waves. The idea of water staying attached to a hull just didn’t stick, pardon the pun.

Then came the Second Revelation: riblets. No, these weren’t small Rigid Inflatable Boats, they were an almost microscopically ribbed surface applied to the hull. Again, America’s Cup inspired. 

Riblets were first used on Dennis Conner’s America’s Cup 12-Meter Stars & Stripes in the 1987 Cup. These itty-bitty grooves adhered to the hull using a special vinyl tape. In less than the blink of an eye, they were outlawed by new rules that prohibited specially textured surfaces that would alter the boundary layer of water on the hull. No one rued their departure, because apparently riblets were a pain to apply. The one positive result was when the riblets were applied to the U.S. rowing shell, the team won a silver medal in the 1984 Summer Olympics, America’s first medal in that class in years. 

In dinghies, at least, Revelation Three was, ta-dah, Teflon. Discovered as a lab accident at DuPont, it soon coated all manner of frying pans in the 1960s. And who could argue with empirical data: if burnt eggs wouldn’t stick to my mom’s skillet, the same magic would apply on the bottom of my 14-foot dinghy. Teflon was available in spray cans, and that became a part of my pre-regatta rituals. 

Teflon was totally impractical for anything bigger than a dinghy, and the idea of spraying it on a keelboat wasn’t going to happen unless you owned a boatyard. 

So you can see why the regulars at the yacht club bar were fascinated by accusations of my touchy-feely on bottoms. It’s been something I’ve been doing for years. But I still don’t have a clue on how to best prepare a hull for racing. Wax it, sand it, paint it, or just varnish the tiller. Whatever works for you.

I do need to share Caswell’s Rule No. 1 about hull bottoms. The only time the bottom of your boat can be too smooth is when you’ve capsized and you’re trying to hang on.