Smoothed and Polished, Not Sanded and Left Alone
Some months ago I asked the Lightning email List how our members prepare the bottoms of their drysailed fiberglass Lightnings. If you subscribe to the list, you know that I got an earful. I think we all agreed that fair is fast. There cannot be low spots or high spots, if you want the best performance. After that it got much more interesting. People use everything from steel wool (on the board) to lemon juice (cleans hull stains). They were all over the map, with not much of a detectable pattern. Opinion varied, to say the least.
Some point out that it is more important to be on the right tack than to use the right polish, and of course this is true. What we’re looking for here is that extra foot at the top of the leg so we clear that Starboard tacker, for example. You upgrade your sails periodically, right? Tune your rig properly and adjust controls for conditions? So, don’t you want to use your hull to its full potential? And, the psychological factor should not be undervalued. If you are confident that your boat is at its peak, you might loosen up and sail better. Even placebos can be effective.
So, I went back individually to some of the class experts, speed demons and recent champions for whom I could obtain an email address. This was not a scientifically exact sample, and we can’t know if they tell us all of their deepest secrets. Some did not respond, and a couple said “I have a guy who takes care of all that.” However, the responsive experts showed a lot of consistency. They experts who responded generally agree that smoother is better. They sand with up to 2000 grit paper, some then buff it, and all apply polish. Most said they do the same on the board and rudder, as well as on the hull. (The others did not say: nearly none of the experts said they do nothing to the foils.) The consensus expert opinion seems to be that Super Smooth is the way to go. The idea that a rough finish encourages laminar flow is out of favor, at least in this group.
This quest for smoothness makes sense to me. For one thing, all the proponents of a dull finish who would wet sand and leave it that way emphasize that all sanding strokes should be parallel to the water flow. However, this may be impossible! We always sail with at least a little heel, so the water flow will be different on the different tacks. Flow patterns probably change with boatspeed changes, as well. Can you really sand precisely with the flow?
The Best Bet
Based on all the input, weighted toward the expert opinions, here is the consensus. First, fair it: Build up any low spots and sand down any high areas. Start sanding with whatever grade you’ll need to get it smooth. If it’s already pretty fair, start with a higher number. Run up the range of paper: 800, 1000, 1200, 1500, and 2000+ if you can find it. (Certain auto parts stores seem to specialize in painting supplies, and can be a source for the higher grades of paper, and a selection of compounds, etc.) Then, machine buff with a light rubbing compound. Then use polishing compound by hand, maybe removing it with a random-orbital buffer. Then apply a coat of Teflon polish such as Starbrite, Hullcote, or equivalent. Finally, put on a second coat of Teflon. – And be sure to wear sunglasses as protection against the shine!
When to do this: not on a new boat. I think they all agreed we should leave a new boat alone, just buff and polish it. Only sand if you need to make it fair. Our experts generally use the same process on their foils as on the hull.
Tips From the Experts
Between paper grades I'll take a pencil or even a sharpie and draw all over the bottom or blade so I'm sure I hit all the area as I sand. All the markings should be sanded away. Of course, only sand in the direction of the water flow.
A fresh sanded 500 grit or so is the fastest finish but it only lasts for about a day or two and then you would have to do it again. Not very practical and you would run out of gel coat pretty fast.
Skip Dieball said, Once I’m happy with the smoothness, I’ll apply a wax/Teflon/cleaner. My current favorite is the Holmenkol products out of Europe. They have two products that I like: SportPolish and AquaSpeed. Check them out: http://www.sailingproshop.com/Holmenkol.aspx . Of course I’ve used the handy Starbright Teflon product and its West Marine counterpart.