Hey guys, I was wondering just what the purpose of a hot coat is and how to mix one. I tried to search the archives, but my computer was taking forever. Thanks. Tom
The purpose of the hot coat, or sanding coat, is to fill in the dimpled pattern left by the lam coat. If you wanted to I suppose that you could surf on a lam coat, but i wouldn’t recommend it. You can by premixed sanding resin, or take laminating resin and add 5% styrene (surfacing agent) per gallon, and throw in some parafin wax just for the heck of it! A good hot ccoat makes a sander very happy i hear! Drew
I heard once that water moves faster past a slightly rough surface. Does anyone know anything about this? Would that be an advantage to not putting a hot coat on? Just crazy ideas.
a hot coat requires a diff. resin mix than the lam. the only difference is that it contains a surfacing agent, not paraffin wax. you can buy it pre-mixed, or mix your own. go with about 5% surfacing agent. kick it a little hotter than your lam, but not too hot. that will cause a brittle hot coat. good luck
Inducing turbulence can, in some very specific instances, reduce drag. It usually involves many hours in a wind tunnel, with a team of Post-Docs to crunch the data. It also usually is done when a gas (e.g air) is the working fluid. Water is 1000 times as dense… Tried it once for a senior project in college, on a Frisbee - actually a disc for ‘Folf’. Didn’t work… I recommend polishing to 600.
Your right about water moving faster over a "very slightly textured surface. Most of the America’s cup boats have some kind of pattern on the hulls. However you my friend will never go fast enough to take advantage of this physical trait. But certainly feel free to try it! Personally I’d hot coat then gloss. Nothing beats a shiny mirror gloss coat!!
The rough textured surface turbulates the boundry layer of the flow over an object. This changes the flow over the surface from laminar flow to turbulent flow…This carries a slight increase in surface drag but reduces seperation. Seperation results in eddies and voids in the wake to the object causing increase in the overall drag of the object. Hence if a shape is prone to seperation then a rough surface can increase the performance by reducing seperation…hence dimples on the golf ball and rough carbon fibre weave on Ferrari F50 bodywork. However in formula one cars (or indy cars) the design is such that seperation is minimal anyway so a smooth surface is better for reducing overall drag. Am not sure how significant seperation is on surfboard performance but suspect there are moer significant factors coming in to play… http://www.geocities.com/pmccutc2/Frontpage.html
Have you guys heard of traping air under the bottom of the board or better yet putting a contiuos air supply(air bubbles)under the board.By doing this you brake the tintion between the board and the water, the resuts is speed or a gas peddle. It’s been done by my dad, Back in the 70’s,Awqa jet surfboards. It works. Another is like sharks is ruff like sand paper, so way not tape some skate board gripe tape to the bottom of the board, another is to put rock salt on the hot coat and then desalve the salt, you get ruff surface. Some iedas,and yes people say I have salt on the brain or what?