Surfboard Fin Repair

Fin Repair
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A broken or damaged surfboard fin doesn’t automatically mean you need to toss it and get a new set. No way!

With a little handiwork and patience, a broken surfboard fin can be repaired and sea-worthy again. However, if your fin is past the point of repair, you can always consider turning it into some artwork.

How to Fix Surfboard Fin Hum & Whistle

If you’ve ever heard your fins hum or whistle as your carving through a fast turn or picking up speed, that’s not the sound of your surfboard breaking the sound barrier, that’s the sound of turbulence and drag.

Humming fins typically mean they’re dampening your drive.

A hum or whistle is often caused by either imperfections in the trailing or leading edges of your fin. The most common culprit being a trailing edge that’s too thick in spots.

Fortunately, the fix for humming fins is relatively simple.

Take some medium-grit sandpaper to thin down your fin’s trailing edge a bit. Follow up with finer grit until the surface is smooth and any unevenness or unnecessary thickness has been removed.

If your leading edge is the culprit, the same steps apply. Just remember that you want a somewhat rounded leading edge. It should be gradually rather than sharp or flat.

How to Fix a Fin that’s Loose in the Box

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If your fin feels wobbly or loose in the fin box, you can try some of these simple fixes:

  • Rub some surf wax or candle wax on the base of the fin that goes into the box to thicken it up.
  • Insert some thin plastic strips to act as shims around the base to keep it snug.

If your fin won’t fit or feels too tight in the box – a light and gradual sanding with medium to fine grit sandpaper will solve that.

How to Fix a Nicked & Damaged Fin

If you’ve run aground or bumped your fin on a rock heading down to the water, you may have ended up with a nick in your fin.

Nicks, divots, and imperfections in the surface of your fin are not good. These act as potential break-off points for the flow of water, which will lead to turbulence, pressure difference, more drag, and loss of drive.

Fixing moderately dinged fins is not too difficult.

You’ll need some sort of resin – ding repair resin kits and solar-activated resins can do the job – and some sandpaper.

To repair a nicked surfboard fin:

  • Apply resin to the damaged spot and allow it to dry.
  • If the affected area is particularly large, consider mixing in some fiberglass strands with the resin to strengthen it.
  • Re-foil the patched area to match the original foil with progressively finer grit sandpaper.

If the nicks or dings are pretty small, you may decide to skip the resin step and just sand them down.

How to Repair or Replace a Glassed-on Fin

Connection damage to a glassed-on fin can be a bit more challenging to repair. However, if you’ve broken a fin off and were able to find it again, you can certainly put it back on. Otherwise, you’ll need to glass on a new fin to the board.

Tools and materials needed to repair a glass-on fin:

  • Fiberglass cloth and rope/roving
  • Resin and hardener
  • Tape
  • Sandpaper/sanding tool

Repairing or replacing a glassed-on fin follows the same procedure. The steps are as follows:

  • Clean up any broken fiberglass/resin from the fin area so that the surface is flat and clean.
  • Align your fin and apply masking tape in a box around it to prevent resin from overflowing to other parts of the board.
  • Using more masking tape, keep the fin in place.
  • Use a piece of fiberglass rope extending about 1” on either side of the fin.
  • Cut two patches of fiberglass that will go over the rope and on the side and base of the fin.
  • Mix your resin and hardener.
  • Saturate the rope and squeeze out any excess resin. Place this along the bases of the fin.
  • Apply the first layer of glass and saturate/squeegee on the resin.
  • Repeat for the second layer.
  • Allow the resin to dry.
  • Starting with a medium-grit sandpaper, sand the surfaces flat and flush with the original foil. Continue sanding with finer grit until the area is smooth.
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