This is the first iteration of the "Cobra", an open version of my Stinger C-1, which in turn is in turn a modified Estanguet.  I have kept the basic tri-maran style hull, but widened the Stinger by 1.5" in the bow and narrowed it by 2" in the stern.  The object was to move the seating position forward a bit .  

Section through midsection of hull

The Estanguet was the first to use the concave/rail design that is now very popular in both slalom and play boats.

Version 1.0

While the bow appears quite blunt, the waterline is completely below the upcurve.  However, in big waves I have found that the blunt bow pushed water straight up and then into the boat.

Consequently, version 1.1 has been narrowed in certain areas and the flare extended all the way around the bow.  The intended effect (and it seems to work well) is let the water that hits higher up on the bow deflect mostly to the sides, carrying some of the lower water with it.

Final flare design

The final design is still a relatively low volume boat.  The relatively flat bottom with most of the width toward the stern result in a surface boat that glides over most stuff.  Waterline length is at least a foot longer than the competition, making this a very fast boat that doesn't turn very well.
This is my thigh strap system.  Note that it requires low friction around the central loop to balance the tension between the high thigh strap and the knee strap.  It's a bit hard to see, but I've stitched the male and female strap together to make a "Y", with the lower leg of the strap looped around the low knee attachment and held together with a double-d ring.


The lower aluminum strap anchors are made from thin tubing welded to flat plates that are "swiss-cheesed" .  When I laid up the kevlar over the plates, it created a bunch of glass-to-glass areas to lock everything together nicely.  I have used this system in many, many boats and the plate has never come out.  The smooth tubing makes it easy for the strap to slide, so it's easy to release the straps in an emergency.

As usual, my seat is somewhat exotic:  a graphite bucket supported by aluminum tubing and a small foam pillar.

I use the same one in my C-1.  The top flange more or less sits on top of the combing (it's usually much wider), leaving the lower seat about 6.5" above the "floor".  In this open boat, the height is about 7.5".