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Core Sound 17 keel maintenance


greendane
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@Walt S. As a starting point, I was looking at 3/4" wide. I'm going to use 6061 round tube (just for the 39" of stem I am doing) and rip it lengthwise using a band saw (I'll need to find-a-friend as I don't have one), probably about 1/3 of the circle. I'll make a plywood jig to match the curve of the bow stem and then play with it until it fits. The radius of the stem goes from about 100 degrees down to about 60, so I'll need to work that part too. I don't think it will be especially pretty, and the right way to do it would be to flatten the stem itself, re-glass and re-epoxy and re-paint and use a half round solid stock, but it's too late for that for me. I'll be fighting it wanting to flatten the radius a bit, but I don't think it will be too bad given it is starting as a tube.

 

The other recommendation they made, that I think would work fine, is to take the length of tube, bend it first to approximate shape, and then cut with a band saw against a fence afterwards. They said the metal, even if it sprung back some, would retain the memory of the bend. I don't have the tools for that approach, so going with option one. 

 

The worst part about the tubing is that it is far more expensive than the flat bar. 10 feet of 1.5" W 1/8" 5052 was $16.55. The second piece (for the skeg, but 3/4" wide and 40" long) was $3.34. The 40" tube however (6061) was $42.37. The first two also had a $7 each cutting fee, and the tube was $1.10 to cut. Total price, $85.

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This seems a lot of work and money for a rub strip that could be pounded out of 3/4" wide1/16" bar stock. It takes a lot of light taps, but with time and the willingness to not get the curve in a few swats, you can "talk" aluminum around that stem with a mallet. I don't much like the tube idea with a varying radius, as it'll get bigger and smaller as the radius changes, not to mention the "wheel" work necessary to get a tube to the stem shape.

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And I've done it with a couple of dowels clamped in my vise to make a bending jig.  I've done this with stainless, aluminum & my favorite, brass 1/2 oval.  If you have predrilled stuff you just have to be very careful bending near the holes.  And I agree with PAR - bending the tube is going to be a real tricky job - as will cutting it before or after.  If you allow it to twist at all while cutting it in half you might as well give up then.

 

Paul

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You guys are probably right. I doubt I can return the tube now. Some lessons are more expensive than others.  @PaulSmith...the consolation I have on avoiding the twist is using this method (it's all about marking the pipe to get that top line). And this is set up almost exactly to what I imagine cutting off: 

 

 

 

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I like the method!  It depends on getting a good line down the pipe - assumedly a snapped chalk line.  You're still going to have the C section spread out more where it is bent in a tighter radius - so it won't look like it has the same width everywhere.  If you've bought the tube try it & let us know how it works!

Paul

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There does look like there are a lot of the smaller galvanized trailers in our area right now.  All with two pivoting rear bunks and one center roller forward.  And everyone wants between $800 and $1000 for them.  That's not too far off of new prices.  I had noticed in previous searches that the supply of trailers is good in the spring but the prices tend to be high.  Later in the year the prices go down but so does the supply.  Not a supply demand kind of thing but a desperation to get rid of it in a falling demand market I think.

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So nothing ever seems to go as smooth as we hope. Or as I hope anyway. With 5052 aluminum they have to manufacture "flat bar" from a sheet. For the wide one it was fine though did have a slight bow. I straightened it out gently pulling it over a saw horse with firm but mild pressure. The 3/4" piece is another story. It came out with a bow, a twist and a warp. The bow was managed easily enough. And the twist took some twisting in the other direction while clamped. The warp was another story. I started by running it under a mallet. No real movement. But then I clamped it to a table and started working it a. It at a time. It'll be fine. Total of about 45 minutes farting around. 

 

Chapter two has to do with me giving them dimensions for the larger one that were a 1/4" too wide. Ugh. So I'm going to build a jig on my table saw to cut that last bit off. Hope that goes as easy as the rest. 

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Well, it's done. Will post pics in a while. The jig for ripping the tube worked perfectly. It did take some

work with a file to round over cut edges. And the bend was pretty easy too. Just a little at a time seemed to work. I was surprised but it never expanded the radius with the gentle curve. The downside is that I could never get the radius to collapse to align to the tighter radius on the front. So there was a little more lip there then I liked but I just made sure the 3m adhesive filled it in. 

 

All in all, I think it will serve its purpose and I am more than glad to be done. I'll post some lessons learned later too. 

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Transitions: So one of the many things I didn't do well was re-engineer the keel to transition to the stem. And the same thing on the skeg to the keel transition. I should have tapered these down to nothing instead of stopping short. At the time, I guess I thought those little skinny bits would be too flimsy to manage. It was only slightly odd without the rub strips, but with them, the transitions became more obvious. Compared to what I started with, it's better off than it was. But I'd do it differently next time. Some of the caulking here is a little sloppier than I like, but I didn't want to take more away from the seal. And so it is what it is. 

bow stem 3.jpg

kell to skeg transition 1.jpg

stem strip 3.jpg

Stem strip 2.jpg

stem strip 1.jpg

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While I was at it, I cleaned up and put an extra coat of epoxy on the centerboard. It seemed a little thin in places. Also cleaned out the epoxy and paint drips out of the trunk. Next time I would be more careful to mask no just the centerboard, but the trunk as well. Had to reach in with a hacksaw blade to cut away a couple drips that were hard enough to leave scratches on the centerboard when it pivoted. 

 

centerboard.jpg

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The main keel rub strip was the easiest. It was a little warped so I had to gently work it a bit straighter, but it flexed enough that it trued up easily with the screws. Was only off about 1/2" over the 10' length. The setback here was providing the wrong measurements to the metal shop. Ripping the 1/4" off the length of it with my table saw as time consuming. I had to build a jig of sorts to keep the bar flat and into the table, but also square to the blade. Also had to keep the waste section down and still, which I did by clamping a couple of thin paint sticks to the fence to hold just enough down pressure. 

 

Shaping the taper and curve at the end proved more work than I liked. I don't have a band saw, so I tried a grinder. It mostly clogged up and didn't actually work that fast. I ended up cutting the bulk off with a hacksaw, and using a zip cutter to essentially router off the remaining. That went faster than the hand filing, which is what I used to finish it off. 

 

I was going to try to form the front down over the nose of the keel. I did it, but it never took the form well so I had to straighten it back out. It never went back the way it started. So as you can see from the pics above, it's munged up a tad. 

keel.jpg

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In closing, I just would like to thank all of you for your input along the way. I honestly couldn't have done it without you. @PAR -- you were especially willing to share your expertise and take the time to hammer out all those pixels to help me out. @PaulSmith--thanks for your local perspective. We'll need to connect sometime. @Hirilonde--thanks for weighing in as well. You catch the little things. They were useful. 

 

More to come I am sure, but much thanks for your help to get me to this point. All the best!

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Looks great!  I'm amazed at how nice the bow strip came out!  Well worth your efforts!

 

I'd love to get together some time as I'd love to see what the CS17 is like compared to the CS15 my father started & I finished.  I bet the CS 17 will sail circles around my 18' gaff rigged camp cruiser!  I sold the CS15 as three sailboats was enough for me.

 

Paul

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5 hours ago, greendane said:

...so I tried a grinder. It mostly clogged up and didn't actually work that fast.

When I get a file clogged up with aluminium I clean it by running a piece of copper pipe along the teeth of the file (not across the teeth in the  cutting direction but along the teeth - sideways to the cutting direction).  I haven't tried that yet with a grinder but it might work.

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