User Tools

Site Tools


Weight Effect on Boats

Increasing weight in or on a surfski will usually result in a reduction in flatwater speed. How it affects stability depends on the location of the weight. An increase in stability can allow a paddler to go faster in rough water than they can go with a boat that is faster in flat water but less stable because a stable paddler needs to make fewer paddle braces and can apply power more confidently and effectively in their boat.

  • Speed there have been a number of studies on the effect of weight change on rowing shells. Theory suggests the following: Flatwater paddlers will be approximately 1/6% slower for every 1% increase in total dead weight, all else being equal. Tom Holloway found similar real world results for flatwater kayakers. As you can see this formula should predict a greater difference for lighter paddlers for the same amount of weight change since it is relative to % increase in weight. Mr. Holloway provides the following averaged generalization: “ For a typical single kayak one extra kilogram of dead weight is roughly equivalent to: 7 seconds in the 12km Wednesday night time trial”. Assuming one is not altering muscle mass, a 10 kg change (22 lbs) would result in a 70 second difference over 12 km. 12 km = 7.44 miles. Or 9.41 seconds per mile. At 6 mph this is about .1 mph difference. At 8 mph that would be about .16 mph difference.
    • These differences should apply to boat weight, paddler weight and anything added or taken away from a boat. Weight differences should have an added effect on ability to accelerate which makes an important difference in catching waves when downwinding. It's worth noting that weight reduction in paddler weight may often be available in larger quatities than what can be reduced in boat weight. As long as a paddler retains their strength while losing weight, they are going to increase their ability to accelerate.
  • Stability added weight that is added close to the bottom of a boat should contribute to greater stability if the weight is secure and not able to shift position. The weight also needs to be centered longitudinally and sidewise so that it does not generate any force counter to a boat's resting upright, balanced, trim position. The higher the added weight is positioned vertically the less benefit for stability. A boater who carries water in their life jacket likely gives up some stability. Some surfskiers add a hatch in front of where they sit, under their legs, to provide a place to add stabilizing weight in rougher conditions. They may secure the weight by gluing velcro strips to their boat inside the hatch and to the object that provides weight (can be a water bag with a hose that runs through their hatch cover).
  • Boat Weight - different construction of the same boat design that is lighter should be a little quicker to accelerate catching waves, a little bit faster on flatwater, and a little less stable.

Discussion 2015

weight_effect_boat.txt · Last modified: 2020/12/12 02:40 by preavley