Saturday, June 6, 2009

A note on triplanes

Just a quick note for now; i wanted to post up a tiny bit on the history of the triplane bottom...Greenough (go figure) developed and used it as a bottom shape on the kneeboard design that was between Velo, and the Edge Board.

George was looking for something that would go well in less than all time waves, since Velo only really turned on in great waves...The triplane bottom keeps the same rail line as a hulled out bottom, high in the nose and low in the tail.  But having it blend into an edge instead of a round curve gives you a flatter planing area in the middle of the board allowing it to skate (i hesitate to use that word though) a little more and use the less than perfect parts of the wave to your advantage.

I guess its a pretty natural (if you see greenough as the foundation) progression from hulls (velo derivatives) to triplanes, to...whatever's next (edge bottoms?).  we're all looking for the same hull feeling in a different wave situation...

So i guess all I'm saying is that inevitably we're all going to be filming dolphins and riding mats.


PG said...

I was there, and this is a correct assessment of the evolution of Greenough hulls back in the 70's.

One clarification...the triplane bottoms not only facilitate the high to low rail line while still maintaining a flat (or flattish) bottom, they also allow for the "rail rocker line" to be independant of the "center rocker line."

In many ways, this is one of the keys to hulls. A predominately flat bottom, low railed board is stuck with one rocker curve, rail to rail. This is a huge loss of design potential. Center lines should be independant of rail rocker lines, even if the variation is modest!

Also, another variation of the tri plane bottom is the "curved tri plane bottom." Which means the center panel is slightly domed, and the side chines are also slightly domed. You still have the wedge shaped line of distiction between the three planes, but the three planes are domed independantly. Great concept, rarely used.

Paul Gross

Ryan said...

best comment ever left on a blog...thank you for "chiming" (get it? .....get it?....chime...HA!) in paul!!!
very cool :)

Hilbatron 3000 said...

Paul pretty much said it all- my crew used to call this "the landing strip", and you can see it in a subtle form on a lot of Greg's newer boards.
Of course, one of the essences of hulls is the differential between rail rocker and stringer rocker; but I feel a lot of magic remains to be discovered in the transition from one to the other, including reversing the curve from convex to concave at the transition line. I've had great luck with this on the GeeBees, and a couple of the P-38s, besides actually putting in a couple of shaped concaves in the center flat plane, 'a la Mike Cundith in the mid-seventies- probably the first
double-concave triplanes made.
Very good looking sled, Ryan! BJ