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Core Sound 20 Mk. 3 #22 - Essex Fells, NJ


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Yep, I'm in northern New Jersey, so the leaves are falling in force here.


Some early progress.  Got the crate emptied out and inventoried the parts.  Rather than starting with the hull strakes I've been hunting through the instructions for all the free-floating bench projects, to cut down the number of loose parts that are now occupying every spare surface in the shop.  My assistant has claimed the empty crate and is no longer interested in sanding.


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One early question on the washboard (C6) that drops down to close up the cabin... It has holes cut out and it came with oval shaped lights (C7a) and window flanges (C6b).  I'm wondering what is the right way to assemble this?  I think the procedure is, epoxy paint everything to seal it, then paint, then drop the light in with caulk, and attach the flange with removable fasteners.


However, for the deadlights in the cabin, there is an inner and outer ring, and you glue in a rivet nut between them which you use to attach the outer ring. Here, there is no inner ring, just a rabbet in the washboard.  I could just use screws. . . but it seems like that would be too simple.


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I used inner and outer rings for Old Codger. The outer ring was epoxied on, the clear portlight set in with caulk, and the inner ring bedded in caulk with screws holding them in place. The screws get almost 1/2 inch "bite through the cabin side and outer ring. I think this is plenty adequate for drop boards.

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  • 5 weeks later...

Have been making some progress on the smaller sub assemblies, locker tops, and rudder.  My kit came with a fully CNC'd centerboard and a very heavy solid lead tip as shown in the drawing.    Am getting ready to construct this, and I think I understand the instructions, but I don't really see how it could actually work without breaking off the first time the centerboard  hits the bottom (which will probably be the first time I put it into the water, at least if I'm driving. . . )




The instructions say "First glue the lead tip to the board with thickened epoxy."  I know that epoxy will stick to wood, but it doesn't seem like it should stick to lead. . .  The glue surface here on the lead is relatively smooth.  Do I need to drill dowel sockets into the lead and/or the bottom of the wooden centerboard for shear forces?  Do I need to rough up the lead with a file so that the epoxy has something to hold onto?  I know that the epoxy is pretty strong but this seems like asking too much.


Next / final step reads "Bring the fiberglass sheathing past the lead joint then add another 6" wide strip of glass across the joint."  My question here is, how far past the lead joint should I go with the first coat of glass? I could run the initial layer of glass all the way down to the bottom tip of the board, or I could stop it before the tip and then the next piece could overlap it and cover the bottom.  Or, I could even possibly run the glass from each side around and under the bottom of the lead, like stirrups or footie pajamas, and then use the additional 6" strip to overlap those loose ends with the joint.  My (completely inexperienced) intuition says that without another few layers of glass this will be a breakage point.


In my mind I have this nervous vision of the lead tip whacking a rock at speed, breaking the epoxy joint and just falling out, and I keep sailing on with a the hollow epoxy/fiberglass tip on the bottom of the centerboard that used to have the lead in it.  Maybe I just need more faith in the fiberglass or epoxy.


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You are way overthinking this. Dowels will be on the neutral axis when there is any side loading on the joint and therefore do not contribute much. In fact I can think of situations where dowels are weaker. The two layers of glass contribute way more strength to the joint.


The object of the thickened epoxy is mainly to hold the lead tip and the board together so that you can work on it. It also fills any mynor gaps or voids. Because the lead surface being bonded is smooth, it is always a good idea to sand the surface to improve the bond. 


You have to glass the wood part of the board, it is no extra work to carry the glass about 4" or 5" past the lead joint. You could call it done and you should be fine but we added the extra 6" wide layer just as a safety factor. The exact overlap is not critical, just make sure that bottom edge of the glass sheathing is about an inch below the 6" tape lower edge.


In case you are skeptical, Southern Skimmer has used that same centerboard joint in many Everglades Challenges and many other sails. The joint looks as good as the day it is done except that the leading edje shows a history of hitting the bottom. This is why you should not  glass all around the tip like a footie. Lead makes a wonderful chafing or wear tip whereas glass is not very good.


When I bond the lead to the board, I clamp the board vertically so that the lead can sit on top. I clamp 2 pairs of small pieces of wood  vertically, one pair forward and one pair aft on the board so that they stand up past the lead. The lead is tapering and the wood temporary clamps will not fit tight to the lead but it makes sure that the lead cannot fall over or move out of position but more importantly you can measure the gaps between the wood clamps and the lead on each side to make sure that the lead is straight. Just be sure to put some tape or plastic on the wood clamps near the joint so that you do not glue them to the board. Clean up the squeeze out. 


The only other tip I can think of, be careful if you use a grinder to shape the lead to the wood after it is bonded. I did this once and the transfer of heat into the lead was instantaneous, the epoxy softened and the tip fell off. This should not be a problem for you as I recall that your lead is a pretty good fit. If there is any mynor fairing to be done at the joint, it is better to hand sand and or fair the joint with epoxy.


Good luck with the project.

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I'll add that I was also surprised that this is sufficient before I had a more complete understanding of how strong a layer of 10oz glass really is in tension when used this way. Also, Graham noted that we make sure the tips are a good fit to the board and I think that is an important detail. If there was a tiny step in the joint and it was not smoothed out with thickened epoxy just prior to applying the glass sheathing then this could weaken the joint since the glass fibers are not nice and straight across the joint. I use a 4" putty knife and pull it across the joint with moderate pressure to fill any low spots just before applying the glass. you'll be able to see/feel any "step" in the joint though so you'll see if this is necessary. Another important detail is to use fill coats of epoxy (2-3 of them) over top of the glass cloth until it's nice and smooth and under no circumstances would I sand the board into the glass.  After your fill coats, then you can sand without getting into the glass and do the final fairing with micro-spheres or primer. 


Here are some pictures of a board I did a couple years ago. This one was for Doug's CS-20 Mk3 which was hull number 1. I only used a single layer of 10oz cloth and I did wrap it all the way to the bottom of the lead but as Graham said, that doesn't really do much good as it wears off after only a couple of groundings. I glued my tip on horizontally but only because i was being greedy with my time and wanted to glue the tip on and then immediately apply the glass to one side. (i was in a hurry)



This is a great question and I will add a more detailed picture to the plan sheets showing the glass layers as Graham described for our next victi...I mean builder. 

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Ok, I'm convinced.  Thanks to you both for the therapy explanation.  I was worried there might be some unspoken extra step (e.g. trunnels, other fasteners, ) that would be obvious to the more skilled. . . I'll report back.


Separately should have the rudder finished soon and hung up in a corner of the shop so its out of the way for hull construction.

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You are welcome. I would rather you ask these questions rather than guess wrong and mess it up.


It also helps us to see where we might need more clarification. We agonize over wording and where to put emphasis. I am like most people that if an instruction is too wordy or difficult to understand I will try to work it out for myself.

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  • 1 month later...

Thanks for everyone's suggestions and help, have made some progress on this project. . . finished most of the assembly of the sub-structures in the kit, including bulkheads + reinforcement, cockpit locker tops + coamings, frame for the cradle, tiller assembly and rudder, glassed the centerboard, tabernacles, and scarfed together all the long panels.


I think my next step is stringers + cleats throughout, and then probably the dovetail joints for the hull panels and wiring it up for the unfolding.








Edited by NowWeTryItMyWay
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Looking great. Old Number 3 has been a slow build, but like you I made a lot of the "sub-assemblies ahead of time and now that she's about together it sure feels like I'd hate to be so close and yet so far if this stuff wasn't done. One tip that cost me some time. When you finally get the cradle made, make sure it's really true. Mine was a little off and it took me a bit to figure why my panels were off. I think the fine folks at B & B would have laughed at how little it was off, but I'm a perfectionist until I finally give up and say good enough. Anyway, it turns out my cradle was close to perfect, but my "really flat" shop floor wasn't. Other than that little goof, I'm amazed how perfect the kit is.

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