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  1. #1
    Senior Member
    Join Date
    Jul 2004

    Slotbox protection

    With the addition of a third twin finned board with slot boxes my damage percentage on said fin system has dropped from 75 to only 50 percent. I want to keep it that way!

    I do not want to discuss whether slot is worse than other fin box designs or if some brands use worse slot boxes than other. What I want is ideas on how to increase the likelyhood of a slotted fin just hinging back on impact without ripping out screws or worse.

    To achieve this I am willing to give up both the ability to change fins easily and to place the fins wherever I want in the box. My intitial thinking goes like this.

    Firstly, the chance of having the fin hinge back on impact is bigger the closer the rear end of the fin base is to the rear screw. This spot can be identified by just tightening the rear screw very loosely and sliding the fin forwards until it stops. With my two sets of fins this brings them far forward in the box and give a skatey feel which is ok.

    There is however the question of whether the fin will just slide back on impact before hinging. A possible solution would be to cut a piece of blanking material and fix it at the rear of the box as a stopper. Perhaps rounding it off a bit at the end that sits next to the fin could help the fin pivot. On the other hand a bit of sliding may work as shock absorption, and I have not so far damaged the rear screws on my boxes.

    Lastly there is the question of how to keep the fin in place at the front. Regardless of what others may think or say I do not trust the screw. It will easily rip out. The better the screw sits in the box the more likely it is to take a large chunk of the box with it.

    What I am therefore looking for is some sort of glue, maybe tech7, that could be applied intelligently at the front to keep the fin in place during sailing but also to yield upon harder impact to let the fin hinge back on the rear screw. My initial feeling is that the glue should or could be applied to the part of the base that sits right opposite, in other words the other side of the fin base, of the front screw. I plan to tighten the screw to get the fin in place but then loosen it significantly when the glue has cured. An argument for applying the glue to the side of the fin base or box is that it would be easier to remove if so needed. I do not want a big mess down in the box.
    Last edited by boards_Tomas; 16th February 2017 at 10:47 AM.
    The infamous wavewriter

  2. #2
    Senior Member Gorgesailor's Avatar
    Join Date
    Dec 2009
    I wouldn't glue it. What type of threads are on the grub screws? Are they removable?

    If they are standard set screws, then you could buy different types to increase or decrease hold. For instance you can by cupped or pointed tips for max bite, or rounded or even spring loaded tips to allow release. You may even be able to get plastic versions. All this is mute of course if they are self tapping or captive screws...

  3. #3
    Senior Member
    Join Date
    Jan 2014
    One thing I have noticed a lot with those that sail multi finned boards is they seem to take a lot less care coming in. With a single fin it is so hard to judge the depth with any accuracy that people tend to get of early and walk in. With multi finned boards people seem to ride a wave in that little bit too far more often than not. On a typical day at some spots I see people mashing fins on the bottom more and more. One chap ripped out two fins at the start of a session and a third gybing close to the shore later on. So with multi finned boards, we have 2, 3, 4 or even 5 times as many fins to wreck and we seem to be taking more risks with them

  4. #4
    Quote Originally Posted by boards_Tomas View Post
    With the addition of a third twin finned board with slot boxes my damage percentage on said fin system has dropped from 75 to only 50 percent. I want to keep it that way!
    What? I have had no issues with any of the slot boxes I own.

    We have rocks here in Cape Town and beaches have changed since I was last here. But I have damaged fins, but not the boxes.
    Now back in the UK.

  5. #5
    Senior Member
    Join Date
    Jul 2004
    @ Gorgesailor
    Rounding the tips of the screws would probably help. As would sanding down the edge of the indent in the fin base. None of my five pairs of slot fins have been sitting tightly in any of their boxes in the three boards. So unless I use some sort of glue I will resort to packing tape.

    @ Phil
    You may have a point that multies tempt people to sail further into the shallow. I'm often amazed how people in Pozo (mostly tourists on rental boards I guess) stay in the straps and sink the tail until they touch bottom. I don't.

    I have checked the bases on the fins that chattered my boxes. It's hard to say but it seems they didn't slide back much before pivoting. And that's even though they made huge holes around the front screw inserts. So I guess that as long the fins are placed pretty far forwards there's no need to devise any kind of stoppers. My only goal is to make the boxes more impact resistent. As I have two nice pairs of fins it would be good to keep the possibility of easy change.
    Last edited by boards_Tomas; 17th February 2017 at 05:45 PM.
    The infamous wavewriter

  6. #6
    Senior Member tooold2dance's Avatar
    Join Date
    Nov 2006
    nice house with horses, cats dogs, and bride. USA

    the Slotbox when introduced , on theses pages was critiqued extensively. At that time the weakest part was the screws. Since then variations have been made to strengthen them, now the Starbox, from Starboard.

    i must admit that my feelings were likewise, screws likely to be progmatic .
    for the purpose intended the slot box has been strong. I have removed one pair, after a faulty install, and they were strong.

    your issue, is trying to fix something that wasn't considered, as posted here, all the things they wouldn't do, I suggest the same, nothing.

    K4 Fins 4Boards TRI-sails Sailrepair

  7. #7
    Senior Member chrispavlo's Avatar
    Join Date
    Feb 2009
    quick forum search on Slotbox:

    Quote Originally Posted by chrispavlo View Post
    basher, would you also be a SlotBox evangelist in case Starboard decided for Mini Tuttle?
    it took Starboard 5 years to finally implementing my idea
    Quote Originally Posted by chrispavlo View Post
    just wonder if it would be possible to install standard (short) US-boxes and
    additionally add reinforced sidescrews to also fit SlotBox fins?

    Quote Originally Posted by chrispavlo View Post
    my 2p why i'm not convinced about slotbox from an engineering pov:

    - fixing the fin with a (partly) sidewards force leads to stress points even if the fin just slightly distorting the box

    - the two fin holes distorting the waterflow close to one side of the fin

    - the screw position implies some leverage effect, especially when the fin is moved to a forward position

    - what i like is the depth of the box (~1"/2.5cm?) and the 9mm slot
    just my personal point-of-view

    edit - missed this answer:
    Quote Originally Posted by basher View Post

    Tut tut. Bad science. And that completely misses why Slot Boxes are the answer for multi fin boards.[/I]
    Quote Originally Posted by JB:) View Post
    At what point does this constitute science?!? Can we not just accept that we are a bunch of old grannies wingeing about something innocuous?
    Last edited by chrispavlo; 19th February 2017 at 08:23 PM.

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