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Paddler Weight vs Stability

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What's the relationship between paddler weight and kayak stability? 


For example, in my Curlew with a stability factor of 93 and a max displacement of 300 pounds, is it more or less stable for me at 200 pounds, my neighbor at 150 pounds, or a kid at 100 pounds?  What's that curve look like?  Is the difference negligible?  What happens at the extremes (way overloaded and with no load)?  Is it something I can calculate?


This isn't specific to Kudzu kayaks, but I figured this would be a good place to ask.



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Good question on a very complicated subject.  If you put a very small person in a boat designed for heavier adults it is not going to sink the boat to it's design water line so it will not perform as intended.


As for stability that depends on the hull shape.


A friend of mine was dating a lady that was probably 110 lbs soaking wet. We put her in my personal Curlew and it was like she was paddling a white water boat. Tracking was miserable and with every paddle stroke she struggled to keep it going in the right direction since she didn't displace nearly what it was designed for.


Stability wasn't an issue with that boat.  But a different shaped hull would be totally different.  A more rounded shape would probably be less stable?  So the answer is  it just depends on the boat.


That is why it is important to stay within the design parameters. 

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Thanks, Jeff!  Is there a rule of thumb you'd recommend for minimum paddler weight? 


For my Curlew and its 250 lb design displacement, I'm right there with 200 lbs of me, 30 lbs of boat, and 10 lbs of clothes/vest/paddle/gear.  Your friend's 110 lb girlfriend would be like 150 lb displacement, and that was way too light.  So is the range like +/- 20% (200 to 300 lbs displacement)?


I need to pick another one of these to build for my wife, and she's quite a bit smaller than me.

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Jeff gets it right: "It just depends on the boat." The weight of the paddler is most important because that effects the underwater shape of the boat. However, the height of the paddler's center of gravity is also significant. The CG is affected by the height of the seat and the CG of the paddler's body (women tend to have lower CG's than men). The higher the CG, the more tiddly the boat will be. But remember that stability is just one aspect of a boat's overall character. Any design is a compromise of top speed, long range speed, tracking, agility, initial stability, secondary stability, and so forth. It just depends on what you want the boat to do.

Fair winds!

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 I do all my calculations at 250 lbs.  That is just a good number to use and allows for heavier and lighter paddlers. It doesn't mean you need to displace 250 lbs.  Hard to say how low you can go and it will vary with different boats but 150 lbs is probably a good number.  There is always the option of adding a small skeg to help with tracking.


I designed the Short Shot LV (low volume) just for the the lighter weight paddlers. I have only sold a very few plans and only seen photos of one build so it shows me there isn't much demand for one.

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