Hi,
Well as Angie would say, I have made some sawdust. I cut out and planed the dagger board and rudder for the Triad I am building. They were cut from a short piece of African mahogany. I bought the African Mahogany for the keel and had some extra. The board was 4 quarters thick (1") so I planed it to 3/4" as the plans described. My questions are:
Should these be encapsulated in fiberglass?
If not encapsulated should the leading edge be glassed?
Finally what type of paint/finishing would you recommend?
Terry, there are two schools of thought about 'glassing wooden boards and blades. One is to embalm the wood with epoxy, then sheath it with cloth, forever (hopefully) sealing out the moisture, the other is to just paint or varnish it so it can breath and let the moisture out naturally. This applies to trailered craft, which assumes it will remain high and dry the vast majority of it life.
Personally, I dislike wooden boards and blades, in spite of my love of wooden things. In this application (boards and blades) wood tends to check, warp, have moisture gain/lose cycles, is easily damaged, can rot, etc. I prefer to use inert materials for these parts of the boat. The way I figure it, the board or blade will eventually get moisture in it, regardless of the actions and coatings, including epoxy. If there isn't a sheathing or even epoxy, the board will swell and contract, but this is okay as long as the moisture can get out. If there is an epoxy coating or sheathing, then the moisture will get trapped and in time will cause issues.
Since you have a wooden board and blade cut and ready to finish, we'll deal with that. The leading edge on both will receive impact and abrasion damage in short order, if it's not protected. A sheathing can help, but what works really well, is cheap and easy to do is epoxying a section of double braid line to the leading edges.
To do this you carve a cove shape (a groove) along the leading edge. This serves to hold the rope on the centerline. Soak the double braid (you could use single braid too, but three strand wouldn't be a good choice) in unthickened epoxy, also wet out the cove. Mix up a fresh batch of thickened epoxy and butter up the cove (sort of fill it). Now tack (finish nail, brad, etc.) the soaked line to the top of the board, in the cove and stretch it tight, as you pull it down, tucking it into the cove and thickened goo as you go. You'll only need a few tacks to hold it in place as the goo cures (the cove holds it). Clean up the oozed out goo and use this to fair the sides of the line to the board. The cove only needs to be deep enough to keep the line where you want. 1/4 to 1/3 the diameter of the line is usually fine.
When this dries, it will take a surprising amount of abuse without issue. If you're neat about the way you applied the thickened goo (masked off the areas you didn't want any) you can epoxy coat the rest of the boat and call it done (after paint or varnish of course).
Another idea is to use a "half oval" of brass or stainless along the leading edge. This is easier, just bend it on and screw it down over bedding. I don't like these that much, because impacts will dent the metal, which in turn dents the wood and rot forms behind the metal in this location.
The choice of goo or no goo is a difficult one. If you think you'll have your boat covered and well cared for during its life then you probably don't need the epoxy. If you think you might be a tad abusive to the little girl, put her away wet, leave her in the water for extended periods, lots of exposure to direct sun (no cover), etc., then maybe epoxy and cloth coverings should be considered.
Way to go Terry, glad to hear it! Don't paint that beautiful mahogony, glass it and leave it bright. It is too pretty to hide. When do we get photos?
Quote:Personally, I dislike wooden boards and blades, in spite of my love of wooden things. In this application (boards and blades) wood tends to check, warp, have moisture gain/lose cycles, is easily damaged, can rot, etc. I prefer to use inert materials for these parts of the boat.
Paul, What kind of material do you prefer for a rudder? I have been looking for some kind of "plastic" material but have not been able to find anything I like. I am sure I don't want to use UHMW. the stuff I used on the bottom of my keel was a pain to work with and is somewhat flexible even in the thicker stock.
How about HDPE?
http://www.plastic-supply.com/pages/tech..._board.php
thanks, joel
Joel, HDPE is a good material and easy to work. West Marine sells pre-made HDPE rudders for common production sailors (Catalina 22, Laser, etc.). It's nearly neutral buoyant so it doesn't weigh the butt of the boat down either. Not much sticks to it, including pond scum, so it's easy to keep clean.
I've been using foam cored construction for a while and like it for several reasons. You can make the rudder buoyant, which if locked down, can help hold up the squatting butt of a sailor. If I don't need this feature, I weight it just enough to sink. The weight factor is also important. Getting weight out of the ends of a sailboat is an easy performance enhancement and also benefits the ride and handling qualities of the boat. This method has no moisture sensitive materials, can't soak up water, gain weight, warp, rot and all the other stuff wooden boards and blades have a nasty habit of doing in time.
A couple of layers of fabric, a moderate density foam and possibly an armature inside (aluminum or stainless) to resist side loads, particularly on high aspect blades. I generally use an 8 pound foam and biax and 1/8" aluminum plate if I need an armature.
If I had to build a wooden blade, I'd strip plank it, with a careful eye on grain orientation and sheath this in Dynel or Xynole fabric, set in epoxy. Nope, you'd not see the pretty wood under the goo and cloth, but it would be more stable and longer lived.
Thanks for the replies and ideas! I have kind of decided to incorporate Angie and Paulâs ideas by attaching rope to the leading edge and then either varnishing, epoxy and varnishing or fiber glassing and then varnishing. I agree this is nice looking wood and though it will spend most of "sailing time" underwater (hopefully) it will be pulled out while not in the water. Also it will give me practice finishing something.
By Varnishing I mean some sort of clear coat that offers UV protection. Spar varnish gives UV protection but the instructions say not to use below the water line. Any suggestions on products or methods?
As for the rope will poly rope work or should it be nylon?
Both polyester and nylon will work, just don't use three strand. A single or double braid line will give you a nice smooth leading edge.
Clear finishes have a difficult time with continuous submersion applications on wood. A good quality polyurethane may hold up better then a traditional varnish. In either case, you'll be a trailer sailor, so continuous submersion will not be an issue, which is why you see the warning on the label. Embalmed in epoxy, the clear finish of your choice will have less difficulty, as you're coating cured goo, not raw wood and it will act more like the thermo plastic it is, then the wooden plank it was.
If you do apply cloth, then use less then 6 ounce stuff, preferably 4 ounce. Anything heavier will clearly show the weave pattern under the clear finish. 4 ounce cloth will not show any at all. 6 ounce will show a slight weave, but you have to be pretty close and catch the light just right to notice.
What do you think of the idea of just polyurethane coating without glassing? Possibly with an application of Clear Penetrating Epoxy Sealer and then the poly. Is there another primer type coat that could be applied before the polyurethane that would let the real wood look show?
Solid lumber will usually shed a clear coating pretty quickly (varnish, polyurethane, etc.) if the wood is permitted to cycle through wet and dry periods. Penetrating epoxy alone will not make the rudder water proof, it has to have an overcoat of straight, unthickened regular epoxy, to be truly water proof. Since you're applying the goo anyway, it makes good sense to also lay on some light cloth to toughen up the blade (which takes a lot of abuse). I've stopped using penetrating epoxy all together, except in special applications where I can use its physical properties to advantage. Regular epoxy, if applied correctly, can out perform penetrating epoxy, in most cases
The general rule of thumb with epoxy (of any type) is once you start to use it, you have to go all the way. If one edge of a plank is coated, but the rest just has paint, varnish or poly on it, then moisture will get behind the hard, water proof epoxy and the swelling wood will pop it off. Epoxy only works if you literally embalm the piece, every fastener hole, notch, nook and cranny included.
I have a question concerning the hole in the top front of the rudder that the short rope goes threw. The plans call for a 1" hole that is centered 1" in from the front and 4" down from the top of the rudder. This leaves only 1/2" of wood between the front edge of the rudder and the edge of the hole. Further the plans call for a hole to be drill threw the front edge of the rudder into the hole. The rope goes threw this hole, is knotted and then pulled into the 1" hole so it will not interfere with the movement of the rudder.
My question is do you think it would be ok to make the hole that is 1"in 4" down only 3/4" in diameter? I think I can knot the rope and pull the knot back into a 3/4" hole just as easily as if it were a 1" hole.
I am totally new to boat building and the limited sailing I have done has been in boats that do not have kick up rudders. So I have no working knowledge of how important that hole size is. I am concerned that the ½â thickness of wood, with a 5/16â hole drilled threw it between the edge of the rudder and the hole, in a ¾â thick board will leave a very weak spot. The wood I used for the rudder is African mahogany.