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Ghost Skegs on The Flying Crutchman

You'd think I'd leave well enough alone.

If you recall, I'd installed a pair of what I now call Ghost Skegs behind my craft to facilitate tracking.

They work.

I've since discovered that by moving the a skeg closer to (medially) or further away (laterally) from the hull I can manipulate navigational forces.

This tweaked with me after considering Kula Canoes from the Tobriand Islands. 


I asked myself,"what does an outrigger do besides preventing the boat from capsizing?"

My Ghost Skegs aren't outriggers. I suspect that generally I won't need outriggers as I have a catamaran type hull -- but they do serve as rear outriggers in a fashion as unlike normal skegs or keels they float on the surface of the water outside the hull.

A Chine Runner
I asked about this on the Canoe sailing egoup and I was  given a reference to Chine Runners (pictured right). 

Chine Runners are used on microcruisers  for stability under sail.

But that's not my skegs.  

If you consider the Kula Canoes -- aside from one guy at back having an easy time of it  steering-- all the paddlers dip their oars on the same side.

How is that possible without the boat going around in circles? Surely one steering oar at back isn't enough to prevent this?

Well, I'll tell you, because I discovered the exact same relationship: the medial paddling force on one side runs counter to the tracking force of the outrigger . One pushes the craft to the left the other pushes the craft to the right.

Neat, eh?

Single outriggers are usually sailed to  windward on a craft for that reason. They not only prevent the boat from tipping when under sail -- as they serve as a counterbalancing weight -- but they also tend to steer the craft -- the bow -- into the wind.The wind on the other hand, will attempt to turn the stern into the wind and the bow away from it: ie: steer the boat to leeward.

That's why a single outrigger  and a canoe's hull aren't balanced -- unlike a catamaran. (Other factors in the mix is the one  weight of the sailors and their gear).

Aside from being a snippet of nautical knowledge the contemporary relevance is that I have discovered that by moving my Ghost Skegs about -- by sliding them left and right toward or away from the hull and then locking them into place, I can replicate a similar effect. 

This is handy because
  • I  need paddle only on one side to hold a course.
  • I can tack and still hold a course without having to compensate for the force of the wind pushing me to leeward.
On The Flying Crutchman, I've worked the balance effect with these skegs by moving them inches medially/ laterally.

Today, as an experiment, with the sail up in maybe a 10 knot wind I moved the windward  skeg further away from the hull and gave the boat a shove in the direction of a tack -- at right angles to the wind. The craft kept to a straight line without any need of intervention on my part (especially as I wasn't even on board!) In case you find that a tad confusing the contradiction is that my  kayak, like most of their species,  is designed to turn into the wind and my skegs don't run along side the hull like an outrigger. They're at the back. 


This irony is fascinating. Since tweaking my back end with these Ghost Skegs tracking is so easy on the Flying Crutchman. I can go for significant distances without needing to dip in the paddle to maintain a course. When the wind is up, I will be able to compensate for its lateral force, if I want, by moving these skegs about.

So as soon as I got back home I pulled apart my Ghost Skeg frame and rebuilt it...out of crutches (of course)! The new fit should enable me to quickly slide the skegs closer to and farther away from the hull. Since they are attached to one another -- moving one closer, moves the other farther away.

I can't wait to get back in the water for more trials.



 

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