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Steve W

Core Sound 20 Mark III #3 "Jazz Hands"

293 posts in this topic

Not much to report. My wife has me restoring a old Scamp camper, so I am only getting about an hour or so a day working on it. I have decided to do all the finger joints now and hide the panels under the cradle until I need them. My workspace is fine, but not huge. I do have a question on the scarfs for the hull stringers. Did you glue the scarfs before you attached them to the hull panels or during assembly? I also have the Cboard just about perfectly shaped.

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I do them before assembly. I cut the 8:1 scarf on the table saw. I made a jig (fixture?) to hold the wood at the right angle to run it through the saw.. The jig has a "rib" on the bottom that slides in one of the cross cut grooves in the top of the table saw.

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Well, I am finally back at it. I had an unfortunate summer, losing a business partner I had for 28 years. He was close friend and a really great guy. Cancer sucks for those who have it and its not much fun for loved ones to watch. I kind of lost my enthusiasm for a bit. So I concentrated on the business, and putting a few honey-do's and other loose ends to bed.

 

My wife talked me into getting away on a trip with a couple of friends at the beginning of September and one of the boats was a Cornish Shrimper 19. I sure was jealous of the cuddy and storage. Her's a video I put together of the trip:

 

https://www.youtube.com/watch?v=Tn72j1wRojU

 

That's me with the Sea Pearl. Spending five days sail camping was the elixer I needed. I got my mojo back and I'm fired up.

 

When I left off in the spring I had built a cradle, bought and ribbed a bunch of stringer stock, and glued up a blank for the centerboard and rudder. You may wonder why I didn't just buy the cboard and rudder in plywood that comes with the kit. Basically, I've had a few failure in plywood foils and have seen my share. It's probably irrational, but we all have our issues. So I decided to lay them up with quarter-sawn Douglas fir. I made a template of the cross section Alan provided and used my table saw and a dado blade to get the profile close. I rigged a stop for the board on my out-feed table and got it pretty close at the top. Of course the board is tapered, so I took the lead weight and traced it on the bottom and now I'm just hand planing it to final shape. I spend twenty minutes on it this morning and got one side close. It's good to be back in the saddle.

 

It's hockey season, and there is nothing better (except sailing) than having the game on (or listening to NPR podcasts) in the shop and tinkering.

 

2015-10-16%25252007.38.53.jpg

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Good to have you back at it Steve. Also good to see alternating grain patterns on your blade blank laminate. This is the way I build wooden foils too. Are you using the stock centerboard plan form and case design?

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I so distrust plywood foils (yeah....It's silly when they are constructed correctly, but I've seen to many failures) that I had Alan make me a kit without them. Otherwise everything in the kit is stock. Spent an hour this morning with my hand plane. Is there anything more fun?

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I'm on your team.

Aside from any other issues, I don't eat up my blades like plywood, and I can put the shavings in a box for the old cat to sleep in, or the compost pile...

post-4050-0-64072100-1445095608_thumb.jpeg

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On small, not especially heavily loaded blades, you can get away with plywood, but any boat over say 150 pounds raw weight, with reasonable aspect ratio, will flex a plywood blade to death pretty quickly. I prefer inert materials when possible. Composite of various types, HDPE, 'glass, etc. seem to last the best, with fewer issues.

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Go Steve go!   So Carlita proves that  the paint job can really make a difference in altering the appearance of this boat.  I think you are on to something.  By the way nice video.  Real nice Navigator there, eh?  ;~)

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I would like to point out that the Mark 3 level 2 kit comes with a laminated centerboard NOT PLYWOOD. Although our standard rudder blade is plywood it is not heavily loaded and we always ensure that the outer grain runs with the rudder and that it is not violated through the area of max bending stress (at the bottom of the cheeks). 

 

I hope not to distract from Steve's build but thought I would post a link to some pictures of the centerboard that we built for Doug Cameron (CS20 Mk3 builder #1) This construction uses the CB from the level 2 kit. https://picasaweb.google.com/107469640725598007206/CoreSound20Mark3Centerboard?authuser=0&authkey=Gv1sRgCO22_ZyFnbKqnQE&feat=directlink

 

Hand shaping the board is a rewarding and fun process. I applaud you. Go Steve go!!!

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Sure, now you tell me! I guess we had a communication issue somewhere along the line, but I was sure the kit included a plywood centerboard. I still wanted to make my own, but it took me longer than I thought, and it's been fun! I'm glad you clarified this for the future builders.

 

I noticed in the pictures that you scabbed on a few supports to attach the centerboard weight. I am just to this point and my plan was just to stand the board verticle and let the weigh of the lead clamp itself while gluing. I'm assuming you anticipated alignment issues?  Or is there something else I'm not thinking of?

 

Take Care,

Steve

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I used the supports to position the lead and made sure it would be fair on BOTH sides. Then I glued it on and glassed the first side of the board all in one step. Then I flipped, removed the supports and glassed the other side. 

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Don, I asked the same question and the logic is that since it's all covered in glass, that isn't neccesary for strength. I like what Alan did with the supports. Seems pretty simple. I know getting the Cboard square and fitting in the trunk is important. A centerboard that hangs is not fun.

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Thrillsbe, you got it right. No bolts, screws dowels or anything just thickened epoxy and glass on the outside. Graham doesn't even always glass all the way around the lead but just down about 3 or 4 inches past the joint. All of the loading is in compression and tension on the outer edge. Keel bolts are always used at the far edges of a keel for the same reason. In this case the glass is more than strong enough. It is essential however that the surface be smooth and continuous so the glass fibers run smoothly and straightly over the joint for maximum strength. The lead must be totally shaped before attaching. Don't be tempted to try to sand or grind the lead once it's glued on, Graham tried this one and the lead just heats up, the glued butt joint weakens and the lead just falls off (that is before glassing of course). Before I glassed the board, I pulled thickened epoxy over the joint to fill in the last of the minute jog in the joint between wood and lead. 

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Is 6 oz cloth OK for glassing the c/b?  That's what I'd planned on.  It's what I have, and have accounted for in board thickness.

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Don, I did like Graham and only glassed down  about 2 inches on the board of my Cs-20 Mk-2. I first "glued" the lead on with the board standing on end and gravity being the "clamp", then used Q-cell putty to even-out and fill gaps between the wood and lead (like Alan did), and lastly, glassing half of the board at a time. I don't remember if it was 10 oz. or 6 oz. cloth. I'd think the 6 would be fine, but you could ask Alan or G. about it to be sure.

 

By-the-way, to cast my lead tip, I shaped the entire board the way I wanted it, and then cut the tip off and used it to make a plaster mold for the lead. Someone else (don't remember where I saw it) made a sand cast mold.

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Graham says for 6 oz glass, use 2 layers locally over the joint. An extra layer shouldn't add enough to bind the board. Should have a 1/16 on either side minimum.

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Thanks, guys.  Good to know that 6 oz is OK.  I'll go ahead and double up at the joint.  One layer of 6 oz and resin adds about 0.050".  I measured the sheathing piece I cut-out for my Anderson bailer.  I always intended to use gravity as a clamp, Chick.  Alan's method worries me, for some reason.  Is there any advantage to doing that, Alan?  And does Cabo-sil = Q-cell?  I've got fairing compound (Quick Fair and an Interlux product), but I think that epoxy thickened with Cabo would be stronger.  Right?

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Q-cell is a brand of micro-balloons, so no, it is not like Cabosil. It sands easier. Actually, I usually use a 50-50 mix of the two. Use only Cabosil to bond, but for filling "irregularities" in the joint, you don't need the strength, so that's why I use something easier to sand.

 

HURRY and finish in time for our "mini-messabout". Only kidding. But I'm excited that you're getting close to finishing. I wanna go sailing!!!

 

Steve---sorry, guess we took over your thread. I was beginning to believe it was Don and my personal conversation. Now we'll turn it back over to you. Keep up the good work.

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