Tubular thruster fins on the 9'5' 'Pretender' HWS

Here's the latest version of the 'tubular thruster' fin setup which we first invented during 2005.

These fins are Paulownia with epoxy resin and graphite over polyester cloth, the first prototypes were made from plumbing pipe.

No fin boxes the fins are set into the board

There's only about 1/8" of toe in on the side fins.

I had a similar setup a few years ago on a pintail and it felt really good but i thought it would do better on a roundtail so here goes... also added about 3/8" of concave through the middle of the board, diminishing towards nose and tail. 

It is quite duiffeent to a thruster in a couple of ways at least, the main one being the large amount of vertical lift it produces, another is the difference in cantfrom outwards to inwards.

The feeling is soft and effortless on the roll axis and extremely powerful on the pitch axis. There's enough horizontal wing area to relieve a large proportion of the water pressure off the hull, so the board is ridden off the fins once it gets going reasonably fast. Thrusters are crisper and grabbier rail to rail. Overall it doesn't feel very similar to a thruster.

Another difference is that whereas the thruster responds predominantly to rail to rail pumping the tunnel setup responds to vertical pumping. That's because the thruster has toe in whereas the tunnel has vertical toe in i.e lift in relation to the bottom.With the prototype (which had a smaller 4 inch diameter tunnel) one had to give a couple of pumps to get the board up on the wing. The angle between the bottom and the wing is slight but it's a bit like how the thruster doesn't like being ridden with both side fins working equally ( drag from toe in) there's a transition speed where the hull in the fin area and the tunnel are working equally, one needs to get over that speed and/or monetarily reduce the load there to let the tunnel take over. this latest board has more than double the lift which the the prototype has so transition will happen sooner, at lower speeds.

That probably won't give you a good idea of how it actually feels, my powers of explanation can't compare with direct experience.