I don’t own any boards with futures or fcs2 plugs. I borrowed a board with FCS2 plugs and center fcs2 fin, but just got around to modifying one of MrMik’s 3d printed broken GWhale turbucle fins to fit fcs2 plugs.
This particular GW fin was an earlier version, when MrMik was printing them hollow and filling them witth silk saturated with epoxy, which proved to not be strong enough for a 10" deep fin in a Longboard… He had sent me a bunch of broken ones along with his latest base designs, and this is one of them cut down to around 4.25 inches deep.
These fins need to be further back on the board, as there is no raked tip bringing the center mass of the fin backwards. This puts almost all of the stress on the rear, smaller fcs2 tab.
I drilled into the fin in 3 stages to 5mm diameter, then epoxied in 3 unequal length 5mm pulltruded carbon bars up well up into fin body through rear fin tab, then later added finrope to extend the base well forward to form the front tab. Just got it to fit today, although I did not bother making the divot in rear fin to have it lock in with the toolless fcs2 design. I added a grub screw in the rear portion to lock it in place.
I did not bother making it perfect, but it fits tightly, and the rear fin tab should be more than strong enough with three 5mm pultruded carbon fiber bars bridging box to base of fin for lateral loads, but a frontal load will likely separate fin rope from fin body. Pulltruded carbon fiber bars are way stiffer and stronger and lighter, than teh carbon fiber bars I have made by saturating and hanging lengths of carbon fiber roving.
Whether the FCS2 box itself can handle 90% or more of the lateral fin load on the rear portion of the box is another matter.
The board owner is a very capable surfer, who never liked the board, “hated it!”, and is willing to sacrifice its fcs2 box to try the fin, which does not make it a good test bed for testing fin performance, unless he decides it no longer sucks. It is a stringerless JS in near perfect condition. Not sure of dimensions, way too small for myself and did not fondle it appropriately like I would a board which I would consider riding.
I have several of these Cut down GW fins to fit my own board’s proboxes. They work very well as center fins, but with 50/50 foils do not work so well as rail fins, most of the time. Kind of love/hate realtionshoip with them as rail fins. Love them when going fast, but hate them when going slower.
They have a tendency to catch the leash and not release it, when one paddles at the wave to position themselves deeper and swings around last second to do a buoyancy assisted take off, so this and dragging weed/kelp are considerations a surfer has never really had to consider before with standard looking fins.
Turbucle fins are very forgiving at high angles of attack, stalling and regaining traction very predictably and smoothly, intuitively. When stalled they do not feel like one is dragging a sea anchor, like a regular fin. A regular fin is all or nothing when transitioning from traction to stall, but turbucle fins are just happy go lucky through that whole range. Add in the super high aspect ratio and these are much less draggy and present little resistance to tight turning radius as well, which takes some getting used to.
I’ve been wanting to have some capable, non close minded, HPSB rider give one a go as a thruster center fin. I’d prefer he have a board he actually likes, to try it in, but he claims he will be able to tell if he likes the fin or not, and having seen him surf, I believe it.
