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Round Ranger fins

Round Ranger Fins
I used my existing fin mould to make the fin for the Round Ranger which provides a 460 x 50mm long parallel fin with a 4mm chord.

Two full width layers of 200g carbon cloth are used with a 3rd layer of 30mm wide cloth are used on each side a central 3mm Depron insert is placed in the middle The total weight of un wetted  cloth is 33g giving a target weight of about 60g for the finished fin.

I had a terrible time making this fin and several attempts were made. The fins I produced were twisting and warping for up to two weeks after they were removed from the mould. I'm not sure why this was happening but eventually I made a decent fin. It did lead me to try making a fin using a different method.

The second method of making a fin has been described by Eric Rosenbaum. A carbon sheet was formed using 2 layers of 200g twill weave cloth. Once cured two a 1.5mm carbon strip was glued at the front and a 3mm strip at maximum cord before the two halves were joined the using 20 minute epoxy.



I love this method of making fins. The aerofoil may not be ideal (although it looks fine to me) but is possible to make a fin in a few hours which has; a great finish is straight, light and strong. I'm not using this fin in this round ranger but will in my next boat.

A fin box was made by wrapping 3 layers of carbon cloth on the top of a tape covered greased fin. This was tightly wrapped in latex sheet to force the wet carbon onto the fin. Once the epoxy has cured the fin can be removed from the fin box with a bit of effort. Once the tape is removed from the fin it can be reinserted easily although it this small clearance soon disappears if the fin is painted.




Due to the light weight of this boat I decided to uses as long a fin as possible. The micro magic bulb does look very very small and I suspect that a may end up changing this after a few sailings if the boat looks like it can carry any more weight. It is likely to be the go to bulb in light winds however

A tapped 10mm brass insert was used to provide something for the m2 stainless steel bolt used to hold the fin in the boat and the bulb onto the fin to screw into.


Epoxy is used to make the fin fit the bulb tightly. The fin is covered in a thin layer of grease so that it can be removed from the bulb once the epoxy has cured.x The angle of the bulb can be adjusted by altering the angle of the bottom of the fin

As can be seen from the photos the finish of the fin could not be described as show carbon so a few layers of gloss black paint were applied.

The rudder was made in the same manner as the fin apart from only one layer of 200g twill weave cloth was used on each side and a 3mm stainless steel rod was inserted. The interior void of the rudder was filled with expanded gorilla glue. The finished rudder was fairly light at 20g

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