Chesapeake 17LT Centerline Question

The cold weather has kept me from moving ahead with my Chesapeake 17LT build (cold garage that I can't warm up enough), so I've been spending most of the past week or so trying to make sure everything is aligned properly before I move on to the fillets. 

To my eye, the hull looks symmetrical. With winding sticks I waffle back and forth and pick some nits, but generally looks okay no matter where I put the sticks. Only the aft bulkhead is wired in right now.

Last night I decided to run a string from bow to stern. Again, to my naked eye it looks pretty good. But when I take measurements from one side of the boat to the other from the centerline I get a fairly consistent "extra" 3/16" on the starboard side. 

My questions are (1) how do I shift my centerline and (2) will I even notice if I shift the centerline 3/32" to even it out?

I'm happy to put in the work if it's going to make a big difference, but my concern is that I'll throw things even more out of whack if I go splitting hairs when I don't really need to.

4 replies:

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RE: Chesapeake 17LT Centerline Question

If it was my boat I wouldn't bother. Among other things, you haven't put the deck on yet so it's likely to change again.

But if you're going for extra credit, which centerline are you getting the discrepancy with - the top with no deck or the keel?



RE: Chesapeake 17LT Centerline Question

What else besides that aft bulkhead is there to wire in before you start tacking panels together?

Recall that these kits, once delivered and unpacked, are a flat pile of plywood shapes. The 3D effect becomes stunningly apparent as things're fitted in place; that 3/16" difference you're seeing may just disappear once you've got more of the parts holding everything in position.  

And as Laszlo's suggested, 3/16" on a ruler ain't much on a 17' hull assembly.

I'd proceed with a build before jumping to conclusions about what's not symmetrical at the stage you're at. 

RE: Chesapeake 17LT Centerline Question

Hi RDunlin, 

The most important element you want to focus on at this point are:

  1. is the hull center line straight including the stem and stern (e.g, would a vertical plane line up with the centerline stem to stern on a hull which is sitting level)
  2. that there is no twist.
  3. That the basic hull geometry (angles between panels) are in the proper shape.

If you have that condition, then what is probably accounting for your 3/16 to starboard is the hull side bulging out a bit differently.   Given wood is a natural product and not 100% consistent, two plywood panels will almost always have a slight difference in how much they will bend given a certain force.  the bulge is subtle enough that you are not detecting its impact on the three points above.

What I do to address this prior to filleting, is to use some strapping tape to pull the hull sides together to the correct width at a couple stations. (e.g. one at the part of the boat that equals the 23 inch width) as well as temporarily wiring in my bulkheads…. then I do my tack welds to hold everything in place prior to the final filleting.

All that said, its not uncommon to see the kind of variation you are seeing absent bulkheads in place and setting the width of the boat properly.  if it did not go away (and it never goes away 100%)....i can assure you it will not be noticeable to anybody but you nor will it impact performance.  

so if you want, the strapping tape and temp bulkheads are a way to get comfort and reduce or eliminate this variation prior to further assembly.


RE: Chesapeake 17LT Centerline Question

Thank you all for the comments. They're very helpful and resassuring.

I think I'm probably missing the forest for the trees here. The weather-imposed delay has left me with lots of time to second guess what I'm doing.

After wiring in the forward bulkhead last night, spending another hour or so looking at the boat from every angle, and reading these comments, I've decided I'm going to move forward as soon as I can get an acceptable temperature in my garage!

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