Daggerboard paint and hull bottom treatment

Thread starter #1
I recently repaired a ding in my racing daggerboard. I am wondering what type of paint was originally applied to the board or what type of paint I should use to give it a uniformly smooth feel and look. Likewise, what do sailors do to the bottom of their sunfish hulls to keep them as slippery through the water as possible?
 
#2
Bob,

Wet sanding with up to 600 (or higher) grit wet-or-dry sandpaper used wet with a flat sanding board gets the best racing finish. The repairs of the dings will show but the wetsanded surface seems to be the fastest. Most racers aviod wax as wax on the hull or blades actually increases surface tension/drag (hence the water beading you see on a waxed surface) and is slower than wetsanded.

Alan Glos
 
#3
From my experience in recreational sailing, I would suggest the placement of your weight on the hull is far more significant than any treatment you apply to the hull. Before you attemt to make your hull more slippery, I suggest you be prepared to explain why a fish has "bumpy" scales, and a golf ball has dimples.
 
#4
Bob,
I agree with Alan, smooth is faster. No waxing. The big boy's (America's Cup Boats) use McLube on thier hulls, sail, blocks and elswhere. It also cuts down on gunk (weeds, scum and such) sticking to your hull. Suggest reading the Mclube article and the gelcoat repair article under Tips and Tricks on the SF Class Home Page. I also agree with Al on weight placement helping your speed.
A golf ball is dimpled to fly further (aerodynamic lift), not faster. A smooth ball does not generate the lift to sustain the flight of the ball. The history of the golf ball shows the many patterns applied to to golf balls to enhance lift. Scientific experiments have shown that the smooth ball travels less distance than a dimpled.
As to why fish have "bumpy scales", that I can not say. Some aquatic animals (dolphins, sharks) do not have scales and are among the fastest in the sea.
 
#5
Well I've never golfed, and doubt a spherical object generates much lift. What I'm refering to, surface textures, is drag reduction. While I'm far from an expert here, I appreciate nature accomplishes this in a variety of ways, many of which seem contradictory. Man has accomplished this as well, but in my opinion has fallen far short of what nature demonstrates. This is a complicated subject, hence my comment about weight placement on the hull being a more practical attempt to enhance hull speed.
 
#6
From my experience, a waxed hull makes it far easier to drag over the sand to the waters edge. I waxed the deck once, never again! It makes it difficult to stay on board. Passengers will slide off, bumping their heads & bones along the way. As a recreational sailor I've never been too concerned with hull speed. Actually, my greatest concern is to keep the salt water from entering my beer!
 
#7
Al,
I do not play golf either. As an aeronautics major in college, we had to look into why a golfball "flies". It is a combination of ball spin and the dimples that generate the lift. If interested, check this link (http://wings.avkids.com/Book/Sports/instructor/golf-01.html), it gives a more detailed explination of how a golf ball "flies" without getting into the math and other factors involved. As you say, it's a complicated subject.
Since our boats are not spinning, we need smoothness on our hulls to allow the water to flow smoothly past. A defect (dimple, scratch or gouge) will interfere with the laminar flow of the water past the hull, causing turbulence. Depending on speed, a 1" scratch may generate turbulence 10" long before the water reattaches itself back to the hull.
I agree with you on weight placement helping with the speed, my own experience and many of the top sailor interviewed in the SF Bible say the same thing. By sitting foreward, you raise the transome out of the water, allowing the water to flow smoothly back together past the end of the hull. Sitting back lowers the transome, putting the abrupt ending of the hull in the water, breaking up the smooth flow and causing turbulence and drag. Look at how canoes, kayaks and racing shells flow smoothly thru the water vs. powerboats with "square" sterns churning up the water and generating big wakes.
Keep your beer cold, dry (saltwater free) and enjoy. Maybe we could get together next summer for some sailing. My folks are in Maine and my sister in Rhode Island.
 
Thread starter #8
Well, that makes it unanimous among Al, John and myself. None of us play golf. But I do windsurf in addition to racing my sunfish. So, I am accutely aware of body placement and its effects on a hull. In our 5-10 mile per hour wind during our Wednesday evening races, hull balance and speed is everything. So, I will be continuing to focus on balancing the hull with body placement and I will now also be wet sanding the hull for maximum smoothness and speed, dimples and scales notwithstanding.
Thanks
 
#10
Bob,
Check the article on gelcoat repair, under Tips and Tricks on the SF Class Home page (the later steps). As gel coat is not very thick, you can only sand a hull a couple of times. Once your hull is smooth, you have to take care of the hull by not dragging it across the sand and rocks. Carry, use a dolly or trailer to launch and recover, wash any sand and stuff off before putting on a trailer, keep the hull covered when in storage (avoid sunlight directly on the hull for extended periods). Not doing these things will cause the gel coat to deteriorate and you are back to square one. Do these things and it should remain smooth for a long time. I did my hull a couple of years ago and except for a minor scratch or two, it is still nice and smooth (I may spot repair the scratches with Marine-Tex over the off season). If your hull is in decent shape with only a few scratches, don't get paraniod about it being super smooth (unless you are racing for rhe championship). I did my hull as part of a restoration (the bottom was stained, chalky and rough).
Also check the Tuning Guide (Chapt XI, Boat handling) and Bishops FAQs (Where do I Sit...). While a smooth hull is important for racing, more so is the proper set up and handling. As Al says, move your weight around and gain a little speed. Good Luck.
 
#11
Bob,
All of us have ignored you original question about your dagger board. If your board is the composite racing board, I do not believe it was painted, just a gel coat type finish. Just get it smooth and polished. If you have a wood board, you can fiberglass it if you want (a bunch of work). You have to weigh the pros and cons of doing so. Paint, in my opion, is slower than a smoothly polished gel coat or fiberglass finish. I don't care if the board has a repair that shows, it's underwater where it can't bee seen (at least while sailing). If you must paint, one of the Inter Lux paints (check the lable and with the dealer for the correct product) should work. You may need to rub the paint out to eliminate any orange peel or dust and bug spots. Proper preperation will help with a smooth finish. Cheaper are the spray cans (Krylon, Rustolium), the model sailboats racers often use them. Let the paint set up for at least a week before rubbing out. Hope this helps.
 
Top