BYYB Forums

Anybody have thoughts (positive or negative) on using graphite powder mixed in the final coat of epoxy below the waterline for a vacationer?

Thanks in advance,

John K.

I presume you are planning on doing this instead of paint.

Won't hurt, will add a bit of UV protection to epoxy, but not much. Will make it wear better over time, but again not much. If it is really smooth it will decrease the amount of drag on the bottom while underway, but again not much when compared to a good paint job. You just won't have to paint the bottom.

Several of the builders have used it on their Weekender hull bottoms and seem pleased with the results. But then I know of a few that still wound up painting over it ultimately. A number of drift boat bottoms have been done with graphite mixed in with the epoxy. They are getting better wear than with just paint over the epoxy. But then that is a relative thing. They are dinging up the epoxy bottom on the rocks and since there isn't any paint, they just don't notice it as much.

A good 2 part LPU will give better protection and long life. Can be rolled on and brushed out. A quart will go a long way if you are just using it on the bottom.

A good porch/deck gloss polyurethane would be next best from a wear and toughness point of view. Also a lot easier to touchupwhen it gets dinged.

I used graphite on the last two coats of my hull bottom and it still looks like new. (Launched in 2000) It is extremely UV stable and tough, much tougher than paint. I'd strongly recommend it to anyone who doesn't want to be painting the bottom of their boat every couple of years.
Pictures are at my website under "Nine Lives".

Terry, have you been using your boat and not sharing the tales with us?

Scott had it on the bottom of a boat.... he uses his boats alot.... it got dinged up and he decided to sand it off. From what I hear, he is still cleaning up black powder and the warden was not very happy.

I think it is over rated for what you need, you need something with I high concentration of biocide, the barnacles here are a beast and seem to attach overnight.

Graphite makes the epoxy hard and permits the surface to be "burnished" for an extra slick surface, commonly seen on racers. The advantages of it on a well raced planning boat, that is regularly buffed, is high, especially compared to some types of bottom paint. Most people and practically all of the Stevenson boat owners will see little benefits of this material in the epoxy. It doesn't provide any anti-fouling properties. Mixed at around 10% by volume it can increase epoxy break down from UV, but should not be the only thing used to protect the epoxy. Any biocide added to the epoxy will become entombed in the cured goo and not leach into the water to act as an anti-fouling agent.

Graphite is also commonly used as a bearing surface, seen in rudder fittings, under high load areas as reinforcement, etc. It does increase the scratch and scuff resistance of epoxy, but not as well as other materials. On the bottom of a Laser, coating centerboards and rudders it has found good uses, but the average cruising boat doesn't need it.

Thanks for the responses everyone. Seems like for my uses, I wouldn't see a real benefit from using the graphite, so I think I'll skip it.

Weather cooperating, I'll be glassing the bottom this weekend...

John K.

Hi John,

I had thought about applying graphite to our bottom hull, but after seeing a photo or two, it just seemed too messy. So, we opted for a deeper keel and a big, really big sail.

I told Bill Olney just the other day that we still might add graphite to our bottom hull. Just colouring everything in with some lead pencils should do it. Bill said that I had been out in the sun too long, working on my boat.

:wink:

Good to see your log in again Dr. Barnacle. Graphite is messy, but not much different then other fillers. You're not far off with your joke about pencil coating the bottom of your boat. I've seen it done to both bottoms and sails and it worked until they stopped using graphite in pencils. Many things have been used, Teflon, oil (now banned from racing circlets) highly polished metals and plastics, special paints designed to be burnished or wear off fresh coating surfaces or leach biodegradable slippery stuff, all sorts of things. In a racing fleet, where a 10th of a knot can mean winning or being in the middle of the pack, you'll smear custard on the bottom of your crew, if it provides an advantage.

A copper bottom on your boat Jim, would be quite traditional and look great. I'd recommend paint, but you can hammer on sheeting and polish it up, like aunt Sophie's big stew pot, if you like. Maybe some copper power in the epoxy.

Come on Paul, do this right. Copper sheet to be polished every week! Can you just imagine the work???? :lol:

I know racers that polish their bottom each week. The Americas Cub boats wet sand (2400+ grit) and buff their bottoms just about every day. Of course it's a ridiculous amout of effort, but if you can get a free 10th of a knot more boat speed . . .

These same folks will replace rigging pins, shackles and other attachments in the rig with high tech, very light weight bits of line, to reduce what amounts to ounces, in an effort to keep weight aloft to the bare minimum. Carbon fiber spreaders a fraction of the weight of aluminum, Kevlar stays and composite spars all can dramatically reduce the weight of the rig, which translates into a lower CG, higher ballast to displacement ratios and a faster, if much more expensive boat.

This type of diet for the rig is only effective on designs that can take advantage of the decreases in windage and weight. As a rule, gaff rigs can't enjoy the marked gains the high aspect Bermudian rigs do. Saving windage aloft with small blocks, minimal rigging or internal lines (inside the mast halyards, and lifts) can help the gaff rig. So can better sail attachment by using bolt rope grooves or tracks to keep the luff close or in contact with the mast, rather then hoops or lacing. Using sails designed with a "shelf" or designed as a proper "loose" foot, or specifically shaped to fit the rig arrangements of the particular boat will have good returns on gaff sail performance. We're talking about possibly a full knot of additional boat speed, if you go completely crazy with reducing windage, sail shape and attachment enhancements.

The average owner of a Weekender, Vacationer or PC can't or will not incorporate most of the possible refinements available. The boat with internal halyards, in mast sheaves and dainty aluminum gaffs will loose much of the charm they are loved for, but will perform better, by a marginal amount. Compared to other Weekender's, it'll kick butt, but when against other, more modern interpretations of a pocket yacht, will have the same draw backs.

If I had to pick a single improvement, that the average person may want, to improve performance in these boats, it would be a centerboard or daggerboard (in that order of preference), properly positioned. Pound for pound, dollar for dollar, it would provide the most bank for the buck in regard to a performance upgrade. This coupled with internal halyards and sheaves would amount to a big difference in windward ability.

This said, custom sails are not cheap. Internal halyards and sheaves require a new mast, or at least a heavily reworked one. The centerboard could be housed in the keel assembly without being inside the boat, but would be best planed for during construction, rather then a retro fit. These are considerable draw backs, but not unthinkable or doable.