[Paddlewise] Sponsons

This is going to be a real treat - to talk about this sanely.

I did some testing of rescue devices on my vacation some time back. We
tested several devices in Pamlico Sound in 1 to 2' waves and here is what
we discovered about sponsons.

1. They do provide added stability as advertised and I could think of lots
of reasons why they would be useful.

2, They do install as advertised.

3. They do appear to be well made.

4. People do feel more secure in boats with the sponsons installed.

5. It was not possible to feel any difference in paddling performance
although one could feel it when the sponsons dug into the face of a wave if
the boat were heeled.

At this point I was favourably disposed towards them.

The next day two of our group wanted to run Oregon Inlet. (Great fun when
the on-shore breeze is not too strong) There was a strong on-shore breeze
coupled with the outgoing tide that produced large, steep breaking waves.
One of the paddlers was skilled. The other, who owned the sponsons, was
not. The wimp, me, took one look at it and stayed on shore.

As they paddled through both boats capsized. The skilled paddler rolled up
and braced the rest of the way through. The less skilled paddler attempted
to install his sponsons. A breaking wave literally threw the boat over his
head. He lost his grip and the boat floated away. The outgoing tide carried
him out to sea where he was rescued.

This event caused me to reassess the pros and cons of sponsons. We did
further tests in heavy breaking waves and these were our observations.

1. The added form stability increased the chance of capsize in beam
breaking seas.

2. When one is re-entering it is best to do it from the upwind side so you
can hold on to the boat even in large breaking waves. 

3. So long as the boat was held at right angles to the waves the sponsons
improved the feeling of security.

4. I was sometimes difficult for less skilled paddlers to be methodical
about installing them in really hairy conditions. Fear appeared to play a
large part in how they performed their tasks. 

>From this I concluded the following.

1. Sponsons can be useful but they have drawbacks and there are conditions
where they are detrimental. From this I felt that sponsons could not be
considered the "ultimate" rescue device

2. Any rescue method that involves a wet exit increases your risk as
opposed to a method that allows you to stay in your boat.  Separation from
your boat is always increased in a wet exit.

3. It is unrealistic to expect inexperienced paddlers to remember to
install their sponsons before trouble just as it is unrealistic to expect
novice paddlers to keep their boats properly oriented to the waves although
sponsons do make that task easier.

On returning to Canada I ran some studies comparing boats with sponsons and
geosims having the same stability. {A geosim is a similar shape but with
dimension(s) changed} For this test I used a Nordkapp. I found that when
the beam of a Nordkapp is increased to the point where it had the same
stability as the Nordkapp with sponsons the performance was not all that
severely affected and it was unlikely that a novice would notice the
difference in resistance. The more uniform shape of the wider boat should
(I say should because I don't know) be easier to handle than a sponsons
equipped boat since the shape would not alter drastically with heel). Here
I should point out that I use the term "sponson" differently from some boat
manufacturers. The long built in inflatable tubes on some folding boats are
integral to the hull and, while they bulge out the hull, they are not
really "additions" to the hull. It is a fine point but is important in the
discussion as I hope will become obvious later. 

I then shifted the center of gravity on the narrow and wide boats and could
easily duplicate the stability of either boat just by shifting the CG. This
explains why wide expedition boats are not dangerous when loaded. Load the
boat heavily enough and get the CG low enough and it will offset the
negative effects of beam. I recently read Hannes Lindemann's book and sure
enough he mentions this effect several times and was much concerned about
it.  

>From this I concluded that;

1.  If stability is a reassuring factor to a paddler he is better off
having it built into the boat rather than increasing his risk by having to
put it on after an accident when the chances of separation from the boat
increase with time spent in the water. This would be particularly true in
cold weather.

2. That form stability can be, as Marchaj and others have shown, a bummer
unless accompanied with adequate displacement and a low enough CG. 

3. That sponsons serve a useful purpose for those who are doing long
crossings of open water in higher performance boats that have insufficient
stability for easy re-entry or for proper rest at sea. 

4. That sponsons are a definite asset to those who physically cannot roll a
low stability boat and insist on paddling a low stability boat.

5. If sponsons are used they are best used in conjunction with a sea anchor
to assure the boat will not be turned beam on to breaking seas. 

In a general way I concluded that there is no end all and be all of self or
group rescue. Every method and device has is pros and cons. My observations
were that people thought they were very safe because they had skills and
devices and my experience had shown that, on a subconscious level and
sometimes on a conscious level, they seemed to be taking greater, and
possibly excessive, risks because of them.

 At that point I became interested in accident prevention and risk
homeostasis although I did not know at the time that was what it was.   


Cheers
John Winters
Redwing Designs
Specialists in Human Powered Watercraft
http://home.ican.net/~735769/
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