Keel Fin Boxes

Discussion in 'Surfing' started by NCJohn, Jul 28, 2020 at 9:51 AM.

  1. Ricksurfin

    Ricksurfin Well-Known Member

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    I had a fish with keels in the past that used three of the FCS plugs per side. Not sure who made the fins.
     
  2. NCJohn

    NCJohn Well-Known Member

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    I'm not concerned as much about the box ripping out but more concerned with the tabs on the fins failing. And getting as close as possible to a glassed in fin.
     
    Last edited: Jul 30, 2020 at 3:21 PM
  3. NCJohn

    NCJohn Well-Known Member

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    That looks painful :)
     
  4. NCJohn

    NCJohn Well-Known Member

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    I'm leaning towards using the bahne boxes. The extra weight doesn't bother me. The only real sacrifice (I think) would be fin cant? Would someone correct me if I'm wrong.
     
  5. Bruce Fowler

    Bruce Fowler Well-Known Member

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    Fin cant using Bahne boxes could/can be prefigured before the fins are made. A diagram of a cross section of the box and what the depth of the fins need to be to function correctly with the slider on the track allowing the pin & bind system shouldn't be too terribly hard.

    The other option is to have the fins themselves made pre canted like Futures offers at around 6 or 6.5 degrees. True Ames was making Bonzer fins with 19 degree cant.

    If the desired cant is 6 degrees to flat, or whatever, this should be reasonably easy to pre-calculate.

    Many moons ago I rode a 6'11" Swallow Winger with an 11" single keel. I put a keyhole thru the fin where I needed to drop the fin screw thru to attach to the slider in the box. Worked great. I cut area out of the base to reduce weight.
     
    Last edited: Jul 30, 2020 at 12:28 PM
  6. NCJohn

    NCJohn Well-Known Member

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    That looks like the easiest method. Do you think those small tabs will hold up over time with the stress a keel fin puts on them?
     
  7. strez

    strez Well-Known Member

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    I'd rather have the tab on my fin break than the box. You can always get another set of fins...
     
  8. Bruce Fowler

    Bruce Fowler Well-Known Member

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    I did a Fish for a friend using the FCS Fusion boxes. He told me he rode too close to a beach that he wasn't that familiar with and broke off the keep fin on his board. I personally glassed the board, he wanted it really strong. He said "the fiberglass tabs on the fin broke off and nothing happened to the boxes you installed.

    Fusions have a very large footprint and are vastly better than FCS X2 plug. Ironically they claimed they were the strongest they offer, and I disagree. What they are basing it upon is the "skin to skin" connection using their tooling and scribing the o ring in the foam to the upper deck layer so that resin and milled fiber attaches to the plug and the deck.

    Their thinking is sound in principle but flawed thinking.

    First, the support reservoir around each plug is small, even with their tool crating what they call the "H Pattern" for skin to skin reinforcement, the plugs have been know to punch thru the deck or cause cracking in the top skin. Furthermore, look at the round X2 plugs. There is very little material between the outer wall and the corners of the tab inserts. Stress is placed greatest at those corners causing cracking and subsequent failure. In contrast, look at the amount of material & distance from the tab to the outside on a Fusion box.

    A good example of the stress failure is waterbeds. Years ago, when waterbeds were all the rage, I went shopping and the sales guy told me if I got a round one, I wouldn't need a frame. He said "if you have a square waterbed, the amount of pressure along the seams is all at the corners, but if you get a round one the pressure will be distributed around the entire bed 360 degrees".

    It made total sense. Corners are the weak point, and the FCS X plugs were famous for cracking. The FCS Fusion was originally designed for application into EPS blanks. They worked really well not only in EPS but are a superior insert in polyurethane as well. The FCSII is just an updated, keyless version of Fusion that still can take regular double tabbed FCS fins.

    Robin Mair, who makes the other fin boxes mentioned earlier paid close attention to Fusion. His accept two tab fins and are a good product too.
     
  9. NCJohn

    NCJohn Well-Known Member

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    Agreed Strez. That's why I'm thinking bahne boxes. That way I can have the traditional low aspect keel with a solid connection to the box. And as Bruce suggested maybe cut some of the area out of the base to reduce weight.
     

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