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SOF Design Scaling

BigandSmall

BigandSmall

Paddler
Joined
Mar 2, 2012
Messages
433
Location
Northern BC
Has anyone had success with scaling down a design to fit a small paddler?

The internet is a fabulous thing, looking around on it has me considering building a SOF for my wife since we are still one boat shy for the family. After watching her paddle her 21" wide Tsunami SP I see she could easily go a lot narrower and not be unstable. I haven't seen many boats that are not designed for someone 30 lbs heavier than her (which is 1/3 her weight). The one model I have seen in her size is a Waterfield Kayaks Qaanaaq SS but I don't see them listed anywhere in North America unfortunately. She is a hair under 5 feet and 95 lbs so I was thinking roughly 15 feet long and 19 inches wide.

If I take a boat design that is 17 feet long and 21 inches wide and scale it down by 10% on each dimension I get a boat that is 15'3 long x18.9 wide. I read that if the boat was designed to optimally be used by a 150 lb paddler and I wanted see how it would fit I would multiply it by all 3 dimensions being scaled H x W x L. So .9x.9x.9x150=109lb which is close hopefully without being tippy. I did see some pictures of another scaled design for a paddler her size that was 18 inches wide but we lack experience and the extra inch might be comforting.

Does this sound correct for those who have done it? Would it be reasonable to expect the design to paddle as well as the full size model?
 
I'm considering scaling down a Yostwerks Sea Rover 2 by 10%. That would make the boat around 15' x 16.5" (from 17" x 18.5"). Hopefully I'll be able to build it this year. This would be purely a rolling boat, as it wouldn't have enough volume for much else... and I have my Avocet LV (16' x 20.5") for day-tripping and rough water play.

If I had more time on my hands, I would build a SOF the more traditional way (bending ribs and such) by basically building around the paddler's body. That way the boat will be a perfect fit!


http://yostwerks.com/SeaRover2.html
 
The approach you mention sounds fine for the paddler size given. I'm sure you realize that packing volume is way reduced, tho.
 
10% is a lot, when you're talking about scaling all three dimensions... read that as 30% (10+10+10) less displacement. The sea rover I built a couple of years ago, at 19'-8", is quite comfortable for a 165# paddler, pushing it a bit for a 185 pounder, and I'd advise watching the foot clearance as well, since mine is a bit tight there. OTOH, the Sea Rover design is a wonderful starting point for a low volume, fun paddling boat, and a very fast sof. Shortening the design is no problem, but I wouldn't go more than 5% on the other two dimensions... which should yield almost the right displacement. More than 1 to 1 1/2" freeboard behind the cockpit is too much for this design, but it does tend to ride that well, even in rough waters- it's a very flexible kayak.

If in doubt, email Tom Yost. He's more than happy to reply and give feedback on his designs. I still hear from him occasionally, and I haven't built one of his designs for 3 or 4 years.
 
We've looked at the Sea Pup and think it would be an ideal fit but we much prefer the look of Dave Gentry's Disko bay. It makes the others look a little vanilla after having it on the desktop for a while.
http://gentrycustomboats.com/Disko%20Bay%20page.html

I saw this 7% scale down of a Disko bay at the bottom of this page that looks fabulous also. It's the one that got me considering shrinking an existing design.
http://capefalconkayak.com/tassie.html



I've since been told I need to rebuild our deck first before I start another project.....
 
BigandSmall said:
We've looked at the Sea Pup and think it would be an ideal fit but we much prefer the look of Dave Gentry's Disko bay. It makes the others look a little vanilla after having it on the desktop for a while.
http://gentrycustomboats.com/Disko%20Bay%20page.html

I saw this 7% scale down of a Disko bay at the bottom of this page that looks fabulous also. It's the one that got me considering shrinking an existing design.
http://capefalconkayak.com/tassie.html



I've since been told I need to rebuild our deck first before I start another project.....
Click to expand...

Disko bay kayaks are pure hunting kayaks , designed to weathercock . I don't know if Dave Gentry's interpretation at 22" beam has the seat positioned to lessen that effect when paddling with a beam or quartering wind . Greenland kayaks are usually very appealing visually , paddling them recreationally can be tiring when they weathercock .

Tom Yost's boats may not have the appealing upswept ends but if you wanted the Sea Pup's gunnels could be added to at the ends for a more S.W. Greenland look . Mr.Yost's designs are well thought out
 
Thank you, that is good to know. I just liked the more traditional look but if the Pup will paddle better that changes things a lot.

Function over form.
 
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