Designing a Board with Kirk McGinty – Part 2, Initial Designs
This morning I got back from an open water swim with my son and this email was waiting.
Popdart dims based on our discussion looking like 7′ x 27.5 x 3.875 x 86L. We can bump up volume by either tweaking width or thickness (or length). My recommendation would be to keep it thin and go a tad wider. This thing will be a rocket ship.TVD dims are similar — 7′ x 27.5 x 3.875 and 86L. Again, a width/thickness/length tweak will increase volume if you’d like to hit 88L mark.This is the PD CAD model.
From Kirk –
Erik, reducing length to 6’10 would mean an increase in thickness to 4.125″ to net 85L. Only a .25″ change. And you’re right – narrow always surfs better. The tradeoff can be adding thickness which affects how high up the board sits in the water thus affecting overall stability. However we are splitting hairs here. ? I also sent you a section through mid to show how the volume is distributed and the step rail design. The Popdart incorporates a single concave running entry to just behind middle. Then transitioning into a double with Vee and the channel bottom. The concave bottom design adds more rocker at the rail than through centerline. More rail rocker translates to tighter turns. The theory behind the channels to add more grip to the rather significant waterway between the fins. From personal experience with these wide tails, the channels make the boards really drive through turns while adding another level of control to all the speed these things generate.
I typically run the displacement hull entry in the classic SIMSUP shapes as these boards are designed to get on plane easy and early and go fast. The hull “belly” up front parts the water generating lift and allowing the boards to fly. I’ve built Popdarts with hulled entries too but personally prefer the single concave.