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Building the Bay River Skiff 15 #152


Don Silsbe

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On my Belhaven, when trailering I had a short rubber keel roller mounted on the trailer under the CB to let the center board ride on . I was always concerned of the extreme force of leverage on the up haul hardware while trailering. While on the trailer I would relax the uphaul to take the stress off the hardware.

 

Scott

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I'll throw in my vote for "D".  Don't forget that you live in a state where people reload their own shotgun shells.  You don't really have to melt the lead if you can just head to Walmart and buy a bag of #8 shot (at least in Watauga County you can).  You can cut the hole in the CB then put in some screws as Chick mentioned, then put the shot in the hole and pour epoxy in to hold it all in place (be careful not to pour too much in one shot on a hot day, though).  Afterwards you can glass over the whole thing.

Also, don't forget that you need to make sure your board can't go over center in a grounding.  If that happens the boat will weathercock into the wind and it will be quite difficult to rotate the board back into position.  In the as-drawn setup the handle keeps the board from pivoting over-center and hanging you up in the shallows.  This isn't a theoretical argument - I've assisted one CS20 that had this problem and I'm glad I had the little 2hp Honda on board that day.

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Don,

 

That is a perfectly workable system.  The drawback of a cascaded system is the room taken up, which is restricted by the forward bulkhead in a BRS.  I use that same method on other boats.  I actually like the horn for its simplicity and as an indicator of board angle.  Must make special allowances for the crew though.  I would not be concerned about the shape of the board bottom as you would not notice any difference in performance between the one on the plans and the more optimum elliptical shape.  The rectangular shape does offer more area.  I much prefer the epoxy/rope edge to a lead one as I am convinced that it is stronger and makes for a more durable CB.  There is no real need to add screws, nails or anything else to hold the lead in the board.  A simple chamfer around the edge of the cavity will do that and even that is overkill with a glass overlay.

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I agree with you on all counts, Chick.  I can see the advantage to "A" being the lightning rod for (non-electrical) grounding events. The idea of cutting off the tip, and using it for a form was taken off this forum.  They, of course, used a fancy sand mold compound, and not some easy-breezy Plaster of Paris.  Do you have experience with casting into PoP?  I've never done it.  Also, for "D", would you pour right into the hole in the c/b?  Doesn't that wreak havoc with the (temperature sensitive) epoxy laminations?

 

Don:

 

The reason for sand molds vs. plaster of paris is the latter will still have some residual moisture in it no matter how long you let it dry. When the hot lead hits it, the residual moisture in the PoP will turn to steam and since it can't vent into the plaster of paris, it vents into the lead or builds pressure within the casting and blows it apart.....and may do so in with a violent explosive release (think flying molten lead). The sand mixes.......even wet ones........allow the steam to vent through the sand......all very benign. Cement mixes, mortar, plaster of paris......all mixed with water......all behave the same way.

 

You could use the lead shot with epoxy for this, but this mix won't be nearly as dense as pure lead, so the tip would have to be made larger. Smaller the shot the better. Pour in small stages......put the slow cure epoxy in first......then pour the shot into it and let the shot displace the epoxy. Main concern here is to avoid a large enough epoxy pour that would "go off" on you in a wild exothermic reaction.

 

To get a board to sink without a downhaul, total amount of lead will have to overcome the buoyancy of the board. To figure out how much that will take, you will need to know the density of your wood vs. water and then the weight of your board to know how much to add.

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"To get a board to sink without a downhaul, total amount of lead will have to overcome the buoyancy of the board. To figure out how much that will take, you will need to know the density of your wood vs. water and then the weight of your board to know how much to add."

 

Or you'll have to ask Alan, who just tested it :)  The amount of weight needed to sink a CS20 board will certainly work on a BRS15.

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McMaster Carr sells very small lead "shot" which is what I used for Petunia. I built the center board, made a cut out, closed off one side with a layer of glass cloth and then poured about 5 pounds of the small shot into the cavity. I tamped it down pretty well, and being SO small there wasn't much room left for air pockets so it was a pretty dense fill. After that I poured thinned epoxy over the shot, and then sealed the open side with another patch of cloth, and  covered the entire board with a layer of cloth. I also added a strip of Kevlar tape to the entire rim of the board for anti collision protection. She has worked perfectly so far, but if I were to do it again I might have gone a little lower on the board with my "pocket", as well as adding just a few more pounds of shot for good measure.

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Just found my "board folder" of pix. This shot shows the board after the shot was installed and after i had rimmed the edges with both carbon fiber and Kevlar tape. Belt and suspenders again...

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Comment on plaster molds. I bake my plaster mold in my wife's (!!!) oven on the lowest setting for an afternoon. I've not had a problem since I started doing that. Make your mold box as small as you can to avoid a lot of volume to hold moisture. Let the plaster cure and remove the plug (what you are making the mold over) before putting the mold  in the oven. I leave the plaster mold in the mold box so it will be supported well.

 

I learned the hard way about baking the mold many years ago while making drafting spline weights. Hot lead spattering all over!

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Clever trick, Chick!  Yes, I can see that avoiding molten lead is preferred.  I love the encapsulated shot idea.  Unfortunately (or not), my brother gave me about 50# of lead.  Looks like I'll be doing some casting.  @Docpal-- the mirror finish in your last photo makes your c/b almost disappear!  Nice.  @Scott-- I was also thinking of a roller.  Brilliant idea!  @Ken-- that over-center situation has me rethinking this.  Finally, my c/b is made of white oak.  I think I'll need half the amount of lead as one made of cedar!

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Don, if ya don't want to do the math, you could always go "old school". Attach a bag or something on your board and take it to your local pond. Add weight until it sinks the way you want it to.

 

I agree with supporting the board on the trailer. Even a 2 x 4 across the trailer frame from side to side with a couple of layers of carpet under the board will do the trick. (Sometimes there is no cross bar on the trailer in the right place.) Be sure to raise your board off of the support before you launch. A c/b dropping down on the ramp as you back the trailer down and hit the brakes could get real "interesting".

 

I never had the problem of grounding with the board over center, but I can see that it certainly could happen. If you can lift your boat high enough on dry land, or swim under it in the lake (br-r-r-r), drop the board to where it is extended to where you want it, and them mark the pennant so you'll always know where it is. You could also add a stop on the pennant where it goes through the jam or clam cleat. a figure eight knot would do the job.

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Make sure you use a low-stretch up-haul if you rely on it to prevent a similar event.

A little more information: The boat in question was mid-tack in 20+knot winds when it grounded. The boat stopped dead in the water and then was pushed back by the wind (I can't remember if there was much current at the time). We were sailing in company and there were no other boats around. It was really well stuck. We had to try several times from different directions to get the boat off the ground before we were finally able to tow it off under power (sideways, I think, but I don't remember for sure).

It's not the kind of thing that will happen often, but if they had been alone and if it had been winter they would have had a real adventure on their hands.

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Make sure you use a low-stretch up-haul if you rely on it to prevent a similar event.

A little more information: The boat in question was mid-tack in 20+knot winds when it grounded. The boat stopped dead in the water and then was pushed back by the wind (I can't remember if there was much current at the time). We were sailing in company and there were no other boats around. It was really well stuck. We had to try several times from different directions to get the boat off the ground before we were finally able to tow it off under power (sideways, I think, but I don't remember for sure).

It's not the kind of thing that will happen often, but if they had been alone and if it had been winter they would have had a real adventure on their hands.

Graham and I had the same experience in Southern Skimmer in high winds.  Grounded in shallow water before attempting a test run trough the Harlow Canal for the NC Watertribe Race.  Wind drove the boat backwards and busted the CB through the pin and locked it in place.  Good anchor though.  I had a knife and was able to finally make a purchase hole in the CB which we used to force the board up.  Luckily there was a private marina close enough to get to and find transport to go for trailer.  Not our finest hour.

 

I always provide support for a centerboard on the trailer.  For many years, I have covered all small boat trailer beds with a sheet of 1/2" treated fir plywood.  The floor supports the CB, allows hull supports to be anywhere you like, provides space for storing the rudder, tiller and sprit booms as well as protecting the hull from road debris.  Also makes it easy to climb onto and launch or retrieve when you don't want to get wet.

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I've gotten everything nice and level, now, in preparation for taping the seams. I've also spent a lot of time templating, scarfing, and tweaking the seat tank sides. Additionally, I made a cardboard model of the standard seat hatch opening, and evaluated my rod storage idea. After a few iterations, I got it all to work. My long-handled bass rods woulds like the hatch openings to be more like 22" instead of 19". Do y'all forsee any issues with making these openings larger?post-3770-0-22898800-1427483539_thumb.jpg

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