anti-friction coating

[COLD-EH']

I have heard mixing graphite powder in with Epoxy and rolling on the hull makes a good friction reducing coating. I will be applying a coating to a steel hull but I have lots of Poly resin here. How would it hold up as a coating compared to Epoxy and in either case should I prime first or just rough it up? Thanks!!!

[Pericles]

Polyester is acknowledged to be a poor adhesive and requires a gel coat to waterproof it. Try a small area only.

Epoxy resin is used to repair blistered polyester hulls and prevent further water penetration. Your labour is probably the same with each material, except with epoxy you'll only do the task once.

Pericles

[terhohalme]

Is the graphite coated hull wet or dry when picked up from water? Wet, yes.

There is no way to reduse friction resistance by coating, because the friction lies between layers of water molecyles , not between water and hull. Smooth, clean surface is all you need. Or is there some scientific research to prove otherwise?

If you don't belive this is true in water, test the coating in liquid honey or thick motor oil. The phenomenon is similar.

[Pericles]

See this thread on the subject.

http://www.boatdesign.net/forums/sho...d=1#post167640

Pericles

[Anchor Dan]

years ago there was a graphite bottom paint on the market. It made the small sail boats faster. BUT, when left in salt water all kinds of things were growing even faster. So they took it off the market. Graphite and 4 to 1 epoxy works great on my small sail boatincreased the speed a very little, but keep it out off the water when not in use.

[marshmat]

I would be curious to see if part or all of the supposed speed gains with these unusual coatings are simply due to extra care being taken to fair and smooth them, or the coatings being easier to fair and smooth. I have yet to find much sound research linking skin friction to surface material- although the link between skin friction and surface roughness is very well documented. In general, you will have a no-slip condition at the surface no matter what it is made of; the actual amount of skin friction is dependent on the properties of the boundary layer flow.

[Anchor Dan]

The bottom paint was KL 990.
Maybe that is another reason it is gone.

[COLD-EH']

To clarify the friction reducing properties are needed when running across dry ground etc!

[sal's Dad]

I use epoxy thickened with graphite powder as a finish coat on some of my skiffs. Yes, it is slippery, and seems to slide and hold up better dragging over rocks.

I doubt it would be as effective using polyester resin, but what do I know? Maybe you could just mix the graphite into a can of paint, and roll it on?

I can't help you, as to how to get the glue to stick to your steel.


The best way I have seen to make a boat "slippery" is the Grand Manan technique - UHMW plastic sheets nailed/screwed to the bottoms and chines of dories. The boats are slid down the cobble, on their own bottoms, to launch. A winch or pickup truck is used to haul them back up at the end of the day.



Sal's Dad

[rwatson]

Smooth slippery hulls make for substantial performance increases - its not just water molecule friction, which is why dedicated racers go to big efforts to keep hulls clean.
Graphite is not that much more slippery than a fine sanded paint job in water - while graphite is mechanically slippery when compressed, its not that much more slippery in a wet environment where mechanical compression isnt a factor.
Whatever finish gives the smoothest surface (basically well sanded and faired) will be the highest performance.

[COLD-EH']

This would be a sacrificial bottom that if you were driving down a gravel road or across a highway, Well!! Depending on how much it does depends when you have to get the roller out. Hulls built out of steel, guys up here use UHMW as well as steel on aluminum jet boats to be able to slide over jagged rocks. Learn't on Southernairboats.com that Epoxy or Poly is used as well as a preference for Poly tooling gelcoat. Maby not higher than Epoxy but supposed to work really good. They add up to 20% Silicon, Talc and sometimes graphite. I was wondering about galvanic reaction with the steel hull?

[Pericles]

The Tolman Skiff guys use Graphite powder mixed with epoxy resin for two reasons. Protection against UV light and because it easy to touch up or repair. They haul their boats each trip. There are many articles and projects available at http://www.fishyfish.com/tolmanskiff.html

If your boat stays in seawater, then http://www.coppercoat.com/about.htm would be my choice. It burnishes up beautifully.

Pericles

[Go Green]

For a line of waterborne epoxy-silicone low surface energy marine coatings, take a look at www.ecologicalcoatings.com. Series 4000 Coatings, non-toxic foul release coatings providing a slick, hard abrasion resistant surface as well as reducing drag dur to their hydrophobic properties. They might be just what you're looking for.

[Enelson]

There is a UHMW manufacturer in Maine -- try this:

http://www.garlandmfg.com/plastics/products.html

[the1much]

why do people want to get 5 knots out of their boats for a week,,,then watch the speed drop EVERY day thereafter,,,if your dragging ya boat across the rocks,,it aint gonna matter 1 bit if ya got graphite in it,,and graphite "works" by WASHING off,,it only reduces ya "friction""drag" in the water,,,as far as dragging on rock,,,,,why dont ya just sand it off with 24 grit sandpaper.,,if ya dont believe me,,,,google "dolphinite" hehehe,,,thats the stuff that gave ya ALL kinds of speed,,,but wore off in a month,,,then the bottom of ya boat was a pretty GREEN..hehe,,,and if your draggin the boats,,put as much epoxy on the bottom that ya can,,,then plan to re-paint every 6 months,,,,,as for something that will help ya across the rocks,,,try ice.
what ya need is "skid plates",,,like Enelson pointed ya,,,,get plastic runners,,then as they wear replace em
and BUY from Maine,,hehe