CS17 #240

[bagneaux]

I finally got started marking and cutting out the ply yesterday until it got to 100 degrees. I have a question about the 1/4" ply portion of the bottom. The plans show that the piece of 1/4" is 72" long. However when I follow the drawing, there are 12" from the dotted line where it butts the 3/8 ply, another 36", two 8" segments and the final segment. I read above the drawing that the two 8" segments plus the final segment equal 21 1/2". This adds up to 69 1/2", not 72" I have drawn on the ply to the 69 1/2" markings and it looks like the plan drawing. I have NOT cut it out yet.  I ask for your advice. Thanks.

[Designer]

I am glad that you asked before you mess up that expensive plywood.

The 1/4" bow section is 72" long. The 8" marks are there to position the vertical dimensions that give the round to the lower bow (forefoot). The 12" mark is where the forward bulkhead lands forward of that station.

[JEHayes]

I have a somewhat similar (although, smaller) discrepancy in the CS20 plans.  The 1/4" ply section is listed as 72 inches but when I look at the plans  from the joint with the 3/8" ply, the length is 72 1/4" (5" + 40" +27 1/4").  Is this significant?

[bagneaux]

Thank you. So, 48" from where the 1/4 butts against the 3/8, the forefoot is 1 1/4" above the baseline. At the 56" mark it is 2 1/4" above the baseline and at the 64" mark it is 5 15/16" above the baseline. Finally at the 72" mark the forwordmost point of the bow is 11 1/4" above the baseline.  What does the 21 1/2" reference?

Loy

[JEHayes]

My plans for the CS20 are obviously different than your CS17 plans.  My plans show the segments for the 1/4" section as 5" + 40" + (6+6+6+6+3 1/4) = 27 1/4  for an overall total of 72 1/4.  Of course, the actual length of the piece of plywood used will have to be 3" longer than this to account for the scarf joint.

[Designer]

I think that you are putting too much emphasis on the 72" mark. It has no bearing on the dimensioning for the shape of the panels, it could be 70" of 75" and it would not make much difference, it is just a round number to join the panels. You will notice that the side and bottom panels are made up from 36" stations so that when you pull the tape from left to right you can mark the stations. Because the side panel runs longer than the bottom there is a 21 1/2" dimension forward of the last bottom 36" station to fix the forward corner of the bottom(chine/centerline). The two 8" marks are are just sub stations to define the forefoot and are measured from the forward most bottom 36" station.

I notice that there are some arrows missing or misplaced in that area which may be creating some confusion. My latest CAD update uses a new and improved dimensioning engine which has played havoc with many of the plans. I have corrected 30 - 40 plan sheets so far.

[bagneaux]

Good. The 72" measurement was what was confusing me. I had even used my architect's scale to help lay out on the ply and all my measurements matched what I had taken from the plan. The drawing on the plywood looks just like the plan drawing  I knew it could not be that tough since so many have built the CS 17. Thanks so much.