Swing Weight by Darin McQuoid | Feb 5, 2014 | Whitewater | 5 comments There are a lot of guides available that detail packing for an overnight adventure, yet few touch on a paramount principle; swing weight. Swing weight is a slang term for moment of inertia around a predetermined axis. Moment of inertia is the resistance of an object to rotational acceleration. The higher the moment of inertia, the more power needed. Say what? Basically what all this means is that the further any weight (potential moment of inertia) is from the center of the kayak (the predetermined axis) the harder it will be to turn, or once turning, to stop turning. It’s not how much weight you have in the loaded boat, it’s how it’s loaded. Pack the heaviest objects closest to the seat, and lightest the furthest away. On extended overnight trips I’ve seen people put heavy food items under their seat. Reducing your swing weight not only changes the kayaks ability to turn, but also how well the boat will boof, so be wary of putting too much in front of the bulkhead! 5 Comments Butler Cox on February 5, 2014 at 3:53 am Great beta, Darin. How does packing affect rolling & bracing? Tnx. Reply Patrick Levesque on February 5, 2014 at 4:53 pm It’s the same principle for portaging. If your boat feel way heavier with your pin-kit, spare-paddle, float bag and throw bag, try to bring everything closer to the center of your boat. This will reduce the swing weight and make your boat seams lighter. Reply Jay Anderson on February 6, 2014 at 4:55 am A kayaker talkin’ moment of inertia. What has the world come to? Your description is accurate Darin, but you didn’t mention that the effect is exponential. The moment of inertia increases at an exponential rate as you move away from the centroid which is probably right under your butt in an empty boat. Thanks for being so generous with your time to blog for the benefit of all of us! “Hi” to the lovely and talented Shannamar Dewey! Reply Sean Morley on February 6, 2014 at 5:37 pm Great stuff guys! Reply Darin on February 6, 2014 at 7:23 pm As long as the weight is secure I’ve never noticed it affect rolling & bracing. On the other hand if your gear can slide around in the stern, bad news as it can shift to one side and make it tougher to roll and brace on that side. That’s what makes the watershed futa great, you can fill it with air once it’s in he boat so it wont slide around. Reply Submit a Comment Cancel replyYour email address will not be published. Required fields are marked *Comment * Name * Email * Website Save my name, email, and website in this browser for the next time I comment. Δ
Butler Cox on February 5, 2014 at 3:53 am Great beta, Darin. How does packing affect rolling & bracing? Tnx. Reply
Patrick Levesque on February 5, 2014 at 4:53 pm It’s the same principle for portaging. If your boat feel way heavier with your pin-kit, spare-paddle, float bag and throw bag, try to bring everything closer to the center of your boat. This will reduce the swing weight and make your boat seams lighter. Reply
Jay Anderson on February 6, 2014 at 4:55 am A kayaker talkin’ moment of inertia. What has the world come to? Your description is accurate Darin, but you didn’t mention that the effect is exponential. The moment of inertia increases at an exponential rate as you move away from the centroid which is probably right under your butt in an empty boat. Thanks for being so generous with your time to blog for the benefit of all of us! “Hi” to the lovely and talented Shannamar Dewey! Reply
Darin on February 6, 2014 at 7:23 pm As long as the weight is secure I’ve never noticed it affect rolling & bracing. On the other hand if your gear can slide around in the stern, bad news as it can shift to one side and make it tougher to roll and brace on that side. That’s what makes the watershed futa great, you can fill it with air once it’s in he boat so it wont slide around. Reply
