Graphite Hulls

[rturbett]

I've used graphite powder with epoxy to finish rudders and daggerboards for racing. I am told this reduces friction and adds strength. Wouldnt it be beneficial to do this to the catamaran hulls as well? What are the downsides to this? (other than having one choice of hull color- black!)
Rob

[marshmat]

Reduces friction, perhaps, since you can smooth it much more readily. In powder form it won't add much strength. Fairing the hulls can be advantageous if they currently have imperfections, but mixing graphite powder with glue will not give you a carbon-fibre hull. So if your hulls are less than perfect it might help hydrodynamics, but will also add weight. You will not realize an increase in hull strength.

[Bergalia]

And it will leave nasty black marks on the ocean floor if you sink

[rturbett]

Matt,
I do realize that it won't add strength the way carbon cloth may, but it does seem like the epoxy with graphite is a harder outer surface than just epoxy alone- and it smoothes oh so nice. If I'm finishing with three coats of epoxy anyways, I thought it might be worth doing.

Bergalia,
I was actually expecting brown marks somewhere else from going soooo fast!
Give my regards to Lady Eliot Island!

[rturbett]

OOOPS-
L.E.I is Queensland- sorry-
Sydney was great too!

[marshmat]

Yes, it would be a harder outer surface. More brittle, too.
The reason for doing this is precisely because it smooths so nicely. The technique allows you to fair the hulls very smoothly. This is the only reason I know of for doing this.

[Bergalia]

Originally Posted by rturbett

OOOPS- Sydney was great too!

Right state - wrong area. Us way down south on the coast near Victoria look on Sydney - to quote Billy Connolly: "is where if you were giving Australia an enema, you would apply the tube..."
It's a BIG country, has even scared the 'brown streaks' out of Texans. Please come and visit some time. As a country, it's addictive

[yokebutt]

Adds strength of any consequence? No. Reduces friction? No. (no-slip condition near surface) Potential corrosion nightmare? Yes.

If you want a hard surface, I'd recommend Pro-Line epoxy primer, but, if you don't sand it out the first couple of days after application you'll be hating it.

Yoke.

[wet feet]

I might be showing my age here by admitting that I can remember when a paint company that is no longer in the boat market brought out Graphspeed.It was originally used on the British contender for the little America's cup in the late sixties.In essence,it was a graphite powder bound together in paint form and the idea was that if you finely sanded the dry coating,you had a smooth and low friction surface.

[dog]

Originally Posted by wet feet

I might be showing my age here by admitting that I can remember when a paint company that is no longer in the boat market brought out Graphspeed.It was originally used on the British contender for the little America's cup in the late sixties.In essence,it was a graphite powder bound together in paint form and the idea was that if you finely sanded the dry coating,you had a smooth and low friction surface.

Yup, showing your age there!

[unhippy]

Originally Posted by rturbett

I've used graphite powder with epoxy to finish rudders and daggerboards for racing. I am told this reduces friction and adds strength. Wouldnt it be beneficial to do this to the catamaran hulls as well? What are the downsides to this? (other than having one choice of hull color- black!)
Rob

The black hull color may be the biggest reason for NOT using graphite.
Black absorbs light and converts it to heat energy which, under extreme conditions, could raise substrate temps to the point that will severely weaken your epoxy. Just passing on some second hand info. I haven't actually seen this myself allthough it does seem feasible given the low melting point of most epoxy systems.

unhippy

[Deering]

Not sure how much effect graphite will have on water friction, but it's sometimes used on the bottom of river drift boats that scrape over rocks in shallow rivers to reduce friction. I'm told it works well. Might not make your rudder faster, but if you hit bottom...

Have also heard of it being formed up in an epoxy matrix as a shaft bearing surface, either as an emergency repair or in an odd, inaccessible location.