Daggerboard Crazy !!!

Discussion in 'Sunfish Talk' started by mixmkr, Sep 9, 2017.

  1. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    OK... bite the bullet...what the heck..
    Added some alum L bracket to stiffen up the area below the original wood board and help keep the extension(s) attached.
    Screwed in the brackets and then West System epoxy to glue it all together. In a bit when it kicks, will start finish glassing, fairing, etc.
    Was going to go sail today, but this is in the same vein....kinda!
     

    Attached Files:

    • Like Like x 1
  2. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    And...
     

    Attached Files:

  3. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    Will let things harden up good and cure. Final fair and sand tomorrow and maybe a sail tomorrow eve!

    If the sail goes good, will then do a final exterior coat.
     

    Attached Files:

  4. andyatos

    andyatos Active Member

    Likes Received:
    116
    Trophy Points:
    43
    Obi-Wan...

    Here's a video I found back when I was thinking about not only making a vertical rudder for my Sunfish but making it a foil shaped rudder as well. I just never got around to making the jig.

    Seems like you could use a jig like this along with a router to shape your 50 inch super daggerboard into the perfect and efficient foil shape.



    Thoughts?

    - Luke Skywalker
     
  5. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    Good idea. Although not as accurate, I'm just going to eye ball things and use a big sander. I can get pretty close
    The issue I see with making a good foil is that the curve has to be fairly mild overall, as the daggerboard isn't all that thick to begin with. Hence why my middle section was remaining still kinda flat with the edges tapered OK. The video with the jig would solve that, but I actually don't have a router. Never really had a need for one. Might be a good excuse.
    I'm going to do some final fairing and sanding today, so we'll see how it turns out. I may regret a foot longer board now too!.... just the hassle of getting it in and out and approaching the shore lines. I'll give it a "rough" fairing, try a sail and see how it goes.
    thx Andy!
     
  6. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    You know...thinking about that custom jig in the above video, you could also use that shape to add/build up with fairing material by spreading material slidding down the board. Ive done similar and will use 12" sqee-gees to fair out larger, flat surfaces. I've also fashioned epoxy spreaders by trimming them to match inside curves. This would just be the opposite. I used my 12 inch spreader on my extension, spreading across the width... i.e...front to back
     
  7. andyatos

    andyatos Active Member

    Likes Received:
    116
    Trophy Points:
    43
    Exactly. Like when I took the maximum thickness of what is now my vertical rudder (previous owner's hand made daggerboard) and made a foil template out of cardboard (NACA 0012 airfoil) where the maximum width of the foil was the thickness of the old, flat daggerbord, in order for everything to work out and match the NACA 0012, the chord of my rudder was only going to be something like 8 inches wide.

    Super high aspect ratio, cool looking, but probably temperamental and persnickety when you move the rudder too abruptly. It would have looked very much like the one in the photo below. So I bagged the idea of making my current vertical rudder with a full foil.

    - Andy

    [​IMG]
     
    Last edited: Sep 10, 2017
  8. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    Andy...
    Yeah I realize a full and measured foil shape would be best. But wiil probably go with the "middle third" flat and fair the edges by what I think just looks good. The aft edge will curve/taper the outside 3 inches, down to about 3/16" on the aft edge. The front I'll just round out starting about 2 inches in. What I did with my first extension made a very noticeable difference. Will see if the same shape but 6" longer makes a difference. If not I'll cut it off and go back to 44" in length.
     
  9. andyatos

    andyatos Active Member

    Likes Received:
    116
    Trophy Points:
    43
    Sounds good! As a data point for your further experiments, I just measured my GRP Sunfish daggerboard.

    Total length - 45 3/4 inches

    Length below the hull/where full foil shape begins - 29 3/4 inches

    - Andy
     
  10. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    Your total length must be TOTAL length (from the very top above the stops) as I think blade max length is 44" to be class legal. Thanks for taking the time to measure. I was going to go out today, but needed to fair it out a bit more and had some other things to do as well. Maybe tomorrow. My lake (KY lake) is now at winter pool, so I have to watch the shallows now! Actually I know where to avoid, but I'll check out in chest deep water how far the boards "looks" to extend below and gauge when coming back to shore.... when to pull it up! I might raise my rig up a tad too, as I don't like the board to interfere with the boom coming ashore and 20" sticking down below the hull isn't a problem.
     
  11. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    This is pretty close what I'll end up having, using your NACA 0012 profile above. blade.jpg

    And what's in the trunk, will still just be the original mahogany board...no profile...and will gradually morph into this shape below the hull...or about 13" down from the top.
     
    • Like Like x 1
  12. andyatos

    andyatos Active Member

    Likes Received:
    116
    Trophy Points:
    43
    That's correct.
     
  13. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    50 inches in all its' glory...
    The "leftovers" from Irma are coming towards Ky Lake, later this week, so maybe it'll be under 25kts for a good test run. Rain for a couple days first, but this weekend looks fantastic.
     

    Attached Files:

  14. Light and Variable Winds

    Light and Variable Winds Well-Known Member

    Likes Received:
    138
    Trophy Points:
    63
    How much of a preparation did you make to the mahogany before applying the original resin "slurry"? 'Seems like an extremely coarse sandpaper would be necessary. I'd cut very shallow grooves—crossways.
    .
     
  15. mixmkr

    mixmkr Active Member

    Likes Received:
    70
    Trophy Points:
    28
    Lots of sanding with 40 grit with good tapered edges for adhesion.
    Too late now to re-do!!
    Check pic in 2nd post in this thread. The last extension was heavily ground out and fiberglass cloth iver the seam. The FiRST extension was close but not as aggressive with the grinding....but my metal L straps extend well into the wood ( see other pics). The first extesion was more a fairing on the edges but cloth laid over the bottom seam too.
     
    Last edited: Sep 12, 2017

Share This Page