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.
image-2image-3image

 

I love the look!  I know that Kieth commented yesterday that look isn’t everything and I agree, but there is an aesthetic element to a good surfboard design.  There are some boards that you can look at and know they’ll be dogs.

 

Some initial thoughts on this Popdart.  Kirk says it would be better to say wide and thin, but my reaction is that I could still paddle it just fine at 26.5 and that might make it surf better in the pocket.  Something I’m really looking forward to testing is how a 4 inch plus surfboard works when you thin out the rails and keep the volume in the middle, that’s what Pat Rawson has been shaping Mo.  I wanted to try his boards when he was here, but I could’t paddle low 70’s volume.

 

I’m going to ask Kirk for a center rail section of this shape to see the rail profile.  (Kirk sent it)
7' PD Erik center section

 

Keith also asked about hull designs.  Kirk, can you comment here and shed some light on different bottom contours and when/why you use them?  This board has some significant channels.  What’s that going to feel like?

 

I’d love to see what a 6.10 at 26.5 would look like.  How thick would it need to be to hit 85L?

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.

Published by Erik Antonson

Erik is the founder and host of the PaddleWoo podcast, 2X Costa Rica National SUP Surf Champion and owner of Blue Zone SUP Camps.

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8 Comments

  1. This looks a lot like an S3 with the step rails. Differences in the tail split w/ channels vs square tail w/ a stinger. Would that tail have a big difference? The hidden question is the overall rocker. I think the different models have different flat spots that change where the gas pedal is. Can’t wait for Kirk to chime in.

    Eric – post the TVD pics if you have them for comparision. I have the non-channel version with the split tail. It has a lot of ‘V’ in it and I think it really makes it loose (that’s relative to a lot of bigger boards that I have ridden).

    1. No pics of the TVD yet. I’ll post them when when they come over. I’m liking that continuous rocker of the Popdart, and the nose flip for paddling through whitewater.

  2. Also, something must be different between these 2 boards. They have the same dims and the same volume. If you overlay a pic of each, where does the PD hide the volume that would be in the front corners of the TVD? Wider tail perhaps?

  3. Kirk,

    What about the TVD bottom/rails? I’m trying to figure how the Popdart compares. Throw in some S3 discussion too as I also have one of them and I can compare. I love these boards.

  4. I have a Popdart with a belly nose. 90% of the time I’m surfing a 1-3 beach break and thought it may give me some gitty up and go. It surprises me from time to time, early and thinking I’m not gonna get it, it starts taking off. Normally, and in the right spot, one or two strokes and its off like a rocket.

  5. I see in the centre section profile it’s a stepped deck, how much extra volume does this let you keep in a board as apposed to smooth transition to rail?

  6. One of the beautiful things about a square (shovel) nose (TVD) type nose is that it allows for a longer, straight rail line which then permits a much shorter board without much loss in stability. Shorter boards are generally more maneuverable, with a tighter turning radius allowed by the short length. Design in Kirk’s hull designs and the highly functional s-rails and you will have a high performance jet fighter in your quiver. As Kirk said, don’t be afraid to go wider than you think you’ll need. This is an L41 which is not like the more conventional shapes you’ve ridden in the past. And since it will be your first (and probably not your last) it will be your baseline L41. You’ll learn a lot from this board which will feed into your stoke for the next L41 in your quiver. This part of the process is almost as much fun as riding the board. Enjoy!

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