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Spot's new tail

Friday,  05/03/24  09:03 PM

Today was great; I added a "sugar scoop" tail to my 505 racing sailboat.  I had done it 100 times in my head, convinced myself it would work, and then I tried it, and it did.  So rare but so nice when that happens.

So "that's cool", you say, but ... "why did you do it?"  Well...

Spot is an International 505, which means it is 505cm long, about 16.5'.  The Southern California PHRF association, which issues handicaps for ocean racing boats, will not rate any boat which is less than 18.5' long.  And in order to race Spot in many handicap races, she has to have a PHRF rating.  So ... how to make the boat 2' longer?  Why not add a "sugar scoop" tail?  And so I did.

By the way, this is not purely cosmetic, making the waterline length of a racing sailboat longer does increase its speed.  I'm rather interested to see how she sails - stay tuned. 

One part of the modification was that it must be un-do-able, that is, I have to remove the tail for one-design racing within the 505 class.  If you look closely you can see the tail is held on by sixteen bolts, which allow the tail to be removed when necessary.

The material I used is 125mil HDPE plastic*.  It turns out it is made for ATV mudflaps (!), and has the right combination of strength, rigidity, flexibility, and weight.  And importantly, you can "work" it with coping saws and rasps, which is how I shaped it to fit.

This tail began as a flat sheet of plastic, in order to give it that "scoop" shape, I had to curve the seam along the back of the boat where it attaches.  The curve is like a clothing seam, it creates the shape.  And the 3D-ness then gives it rigidity.

Anyway it was a fun project, and will be even more fun if it works on the water.  So far so good but even the greatest plan does not survive contact with the enemy :)

* BTW turns out "mil" means thousandths of an inch, not millimeter.  Just in case you are wondering.

Oh, okay, you want to see Spot in action?  Here's some GoPro footage from a couple of weeks ago, racing off Santa Barbara in 20 knots with my crew Chris.  Yeah it was windy.  I wish I had video of the downwind - which was wild, trapeezing with the chute - stay tuned and I'll get you some...