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Hurricane & Scorpius XS

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I notice when I’m paddling my Hurricane in rough and bumpy conditions that the hull ‘slaps’ when I crest a wave or chop and the ama tracks quietly.  Conversely, when I paddle my wife’s Scorpius XS in the same conditions, the ama ‘slaps’ but there’s little hull noise. Just curious, but what is it about the design of the respective canoes that does this? Or is it just me?

1 Answer

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When I first read the question I thought, “hell I don’t know”, then “rocker”, then “I don’t want to think about this right now”.  It’s been a couple of days, and I think there are three parts to the answer:

  • Entry V
  • Center of Gravity
  • Rocker

They are listed in descending order of importance.

In the powerboating world people are always comparing their vees.  Deep vee hulls are smooth into the wind, but burn lots of gas.  Shallow vees are faster and cheaper to run, but compress the spine.  On a canoe a sharper vee in the entry will soften the landing too.

The Hurricane is a swede form hull, the XS is a fish form hull (I’m guessing a little here, I could check the model, but I want to keep moving).  A description of the differences can be found here: swede vs fish

Simply put, if the footwells are forward its a fish, and if they are back its a swede.  If you mentally take the two cases to extremes and imagine how they would each behave going into a chop.  The fish form hull will descend down the back of the chop earlier.  The tipping point would generally be when the CG (center of gravity) passes the crest of the wave.  A swede form hull will tip later, and more hull will be out of the water.

At the bottom of the list is rocker.  As the bow comes down the hull will slap if the rocker is flat, or roll if there is rocker.  The truth is that there aren’t big differences in the rocker curves of any canoes available now.  This will spark criticism, but what I mean is that they will nearly all be within 1″ of an arc with 18′ chord and a 4″ chord height.  When you compare that the the surface of the water in a wind chop, it’s not a big difference.  So while there will be some differences hull-to-hull here, I think this is a smaller factor.

The ama is mostly about entry and beam.  The Hurricane ama has a big entry vee, and is pretty narrow.  The Scorpius ama has no vee at waterline and is very wide.

Why do you ask?

Michael

Your Answer

asked April 17, 2014
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1 Answer

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When I first read the question I thought, “hell I don’t know”, then “rocker”, then “I don’t want to think about this right now”.  It’s been a couple of days, and I think there are three parts to the answer:

  • Entry V
  • Center of Gravity
  • Rocker

They are listed in descending order of importance.

In the powerboating world people are always comparing their vees.  Deep vee hulls are smooth into the wind, but burn lots of gas.  Shallow vees are faster and cheaper to run, but compress the spine.  On a canoe a sharper vee in the entry will soften the landing too.

The Hurricane is a swede form hull, the XS is a fish form hull (I’m guessing a little here, I could check the model, but I want to keep moving).  A description of the differences can be found here: swede vs fish

Simply put, if the footwells are forward its a fish, and if they are back its a swede.  If you mentally take the two cases to extremes and imagine how they would each behave going into a chop.  The fish form hull will descend down the back of the chop earlier.  The tipping point would generally be when the CG (center of gravity) passes the crest of the wave.  A swede form hull will tip later, and more hull will be out of the water.

At the bottom of the list is rocker.  As the bow comes down the hull will slap if the rocker is flat, or roll if there is rocker.  The truth is that there aren’t big differences in the rocker curves of any canoes available now.  This will spark criticism, but what I mean is that they will nearly all be within 1″ of an arc with 18′ chord and a 4″ chord height.  When you compare that the the surface of the water in a wind chop, it’s not a big difference.  So while there will be some differences hull-to-hull here, I think this is a smaller factor.

The ama is mostly about entry and beam.  The Hurricane ama has a big entry vee, and is pretty narrow.  The Scorpius ama has no vee at waterline and is very wide.

Why do you ask?

Michael