It depends on the boat, of course.

For simple boats, like flat bottom skiffs, changing the length  by 10% or less could work. That means that your "foot off the length from each end" should start out as a 20-foot boat and will end up 18-feet long. For a 10-foot final length you should be starting at around 11 feet.

But, when you change the length, you should also be changing the width and height. If you change all 3 dimensions you lose volume as the cube of the change. So a boat reduced by 10% in each dimension would lose 27% of its capacity. It would also lose 34% of the stability.

When you get to a complex boat, like a kayak, then you have to start worrying about the wood bending. In the picture, the wood originally had 15 feet to make the bend. Now it has only just under 5 feet. It cannot bend that much, especially if the width is not proportionally changed, so it has to have a flat front and back.

You really would be better off just getting a boat that's the length you want. Here's the 2008 Cayugas:

Now compare them to the CLC Wood Duck series (10 and 12):

They're pretty similar in design, except that the 12-foot long Wood Duck 12 is lighter than any of the Cayuga series.

That's my 2 cents,

Laszlo

   Well, the kits are wood, which is quite infinitely maleable (admitting that adding wood is harder than taking it away), but when you are talking a modification of a couple of feet, not just an inch or two, you're trying to end up with a TOTALLY DIFFERENT BOAT.  All kinds of factors to condsider, and "lofting" the panels to fit together at the seams and bulkheads to fit within the new hull shape with that radical change wouldn't be a trivial exercise. And a modified LT that is 12 ft long is going to feel pretty skinny and capacity limited, I would think. No telling how things will turn out with stability and handling.

So, I'd honestly build the boat per plan, and be overjoyed at all the work John did in design and the CNC machine did in cutting out parts - OR - design your own boat and then start with some full-sheets of okume and cut out and build what you design.

And if you do try your route with doing a modification - let us know how it works out.

   My reply post was typed up without seeing Laszlo's, so you're getting two opinions that pretty much say the same things in different ways.  His much more eloquently than mine, of course!

  I have played with these ideas and I think both Lazlo and bubblehead are spot on. First, it is very challenging to make any modifications to a stitch and glue design. These panels are computer cut to precisely fit and relofting to a smaller size is very challe ging to do without cad cam technology. The reducing spaces between forms is routinely used in the strip build community to slightly resize a boat...but typically no more than a 10 percent variance (e.g. making a 17 foot boat a 16 foot boat). In the strip build resizing there is no change other than reducing space between forms typically from 12 inches to 11 inches. Anything more than 10 percent requires a redesign. I would go the wood duck route unless there is something in the strip built family that is within 10% of your target. H

   Specifically what I had in mind was along the lines of the Patrel Play.  Move of a touring boat, but at a lenght that is more managable on the waterways I tend to work from.  14', 10% would be 1.4 feet... so landing us at 12.6 which.. the Cayuga 130 was 13 ft. 1 in.... (I'd misremembered the lenght).  So then, well within that margin.

100% want stripa, not stitch and glue.  The wood duck is a fine boat, but not really my style.  A bit on the wide side, more like the 110 which I didn't care for as much. 

I've also taken a bit of molding around my existing cayuga and considered just a full DIY... but a bit nervous about that route, as a "first boat". Lol.

Hi denwoodjones, 

fwiw, i think it will work out fine if you bring it to 13 feet.  a couple other things i will mention now that i see your reply and understand the situation better:

1)  when you make this adjustment you need to be attentive to the cockpit area which you typically do not shrink.   just becuase you make the boat smaller, you don't want to make the size of the coaming smaller.  in a strip build, this is totally doable...just a bit tricky.  if you buy a kit, the cockpit (Coaming, Riser and  coaming inset) will be precut from okoume plywood and you will have to make some minor adjustments to how this mates to the hull as the hull will be slightly distorted relative to how these pieces were cut (anticipating the full size hull).

2) the paddler weight for the boat is 100 to 220 lbs per CLC's description. since you are decreasing the length only by ~ 10 % you will have a top of weight range in the 200 lbs area.  so if you were pushing the upper edge of the boat....you may need to think about this a bit more.

another approach, fwiw, is to tweak the design by reducing some of the overhang and/or volume (e.g., make the bow and stern more plumb).  the picture below is a modified petrel play i developed that is about 13 feet and 6 inches ish.   it weighs in at 28 lbs and quickly became my favorite boat becuase its just so easy to pick up and go.  the weight certainly makes it easy, but the short length is also an important contributor to ease of moving it around.  below the waterline, it is the unmodified petrel play hull.  the waterline length of the petrel play, fwiw is only 13.15 feet.

hope this is helpful.

a fuller description of the project can be found at this link: https://clcboats.com/forum/clcforum/thread/50725.html

h