Slippery GRP hull

[ianat182]

Trailing edges squared do assist the water flow. Fine edged foils and rudders vibrate and seem to break down the laminar flow over their surfaces, thus slowing the boat, and it doesn't have to be a planing dinghy to get this vibrating effect, larger yachts do too particularly close to hullspeed. It only needs a 3mm flat edge to stop the effect, usually felt mostly on the rudder.

Mind you there is the well trodden myth of the black masts being 'faster' than the silver or gold due for resurrection sometime soon, I expect there'll be a 'new'additive to the anodic finish that will make others obsolete.......

 

[savageseadog]

Golf balls fly further with dimples. I'm sure I read somewhere the same applies to hydrodynamics.

 

[uforea]

I have used 400 grit wet /dry on the underwater sections of both the boats I have owned and it definitely does make a difference. The boat is not faster but does accelerate faster out of tacks, needs less wind to attain hull speed and has a noticebly cleaner and quieter wake. As an experiment one year I did the opposite, polished everything to a near mirror finish, within a month the boat was on the hard being rubbed down with 400 again.
I dont know how often you could do this as it is quite abrasive and could soon break through the gel coat. Both of my boats were 70s vintage and I think the gel coats then were much thicker than later builds. Yes, it does make a difference, try it and see.

Ted