Effects of bow joint length

[mustangermatt]

I made some interesting observations about the bow while going 3d with cs 17 #97.

I did not find anywhere in the plans describing the length of the flat joint at the bow, so I made an educated guess. (It is probably there, but I need new glasses). Keep in mind I am a guy so asking is not usually the first option. This is where the sides are joined to the bottoms prior to unfolding the boat.

In the messages here I read one that was 12" (cs 20 I think), and looking at some pictures it looks like people are doing anywhere from about 4" to 10"?

I liked the fair look of the bow with the longer joint, where the chine starts farther aft, so I made mine 14" figuring I could cut it back if need be.

I was able to fold the boat (barely). The bottom at the 3/8 to 1/4 joint actually started to fail on one side so I put two more layers of tape both sides, that fixed that. Steeper bend or stiffer wood or both, I don't know which did it. Next boat will use scarf joints instead of butt joints.

It took a lot of work to settle the forward bulkhead into the bottom, but it went.

The keel line is correct since it is supported in a three point cradle that matched the planned outside form of the boat (I was paranoid after reading some of the posts here about sag), but it looks like the seat stringers start a very gradual sweep up as they approach the forward bulkhead. I could only detect this with a level, maybe 3/8" rise in the forward 2'-3'. By design or a symptom of deeper than designed V in the bow?

Where the difference is really noticable is that the bow has a very pretty rounded form for the first 3' and the chine starts well back. Well worth the extra work, but a little tricky. I would be interested in hearing what the length was supposed to be :-)

[Brent]

A word of caution about the three cradle support: be very careful to avoid putting a hump in the middle of the boat.

I used a three cradle system, which helped get the boat into initial form. But over time (mine spent several months in the cradle) and with standing in the hull, there is a tendency to sag between supports. The same thing happens with two supports but with three there is the risk of getting a hump in the middle. I caught this early enough to get it corrected, but thought you might appreciate a heads up.

[mustangermatt]

Thanks for the heads up. I caught a sag between the forward and middle supports tonight that opened up the bottom seam a little. Easy enough to retighten now, but as you say if I had missed it and glued it that way...

Thanks again.

[thebob]

So guys what is the optimal bow joint size?

And what recommendations are there for a support?

I was thinking along the lines of cradles for the front and rear bulkheads and the temporary frame cut to size minus the hull thickness.

Do you think some longitudinal support is needed between the frames ?

Or maybe notch them and use a central support along the keel?

I've even thought of hanging the hull from the bulk heads, but it doesn't seem so practical.

It's a tricky one to visualize before building. On the plans it looks quite flat down there but I'll bet there is quite a curve once everything stitched up.

[Designer]

I like 9" - 12"

[John Yow]

Regarding the length of the tape at the bow, I made mine about 18", but adjusting the assemblies to start stitching the centerline, my tape cracked back to about 10" to 12". To keep the crack from moving further toward the bow, I screwed on plywood pads, then added a couple of stitches (I saw the pads on the CS 17 CD and the stitches in other pictures which Graham has provided to this forum.

[mustangermatt]

I would recommend a support shaped to the bottom at the forward and aft bulkheads, and another at the temporary bulkhead. I built a rectangular frame out of 2x4's about 15'x4'. This rests on castors so I can move the boat around. After placing the forward and after bunks I measured down 1 7/8" (cs 17) for the center bunk. I got that measurement from one of Grahams posts here.

If I had it to do again I would raise all three bunks about 12'" to put the boat at a more convenient height. Tightening the wires along the keel was a real job with only 4" or 5" between the keel and the floor of the barn.

I would agree that 12" would be the optimum length for the tape. I really like the way the 14" tape looks but it was A LOT of extra work.

Thanks for the input Graham, it is really cool to have you so active in this forum.

Matt