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Heres a question for the technical/engineering DIYers out there.

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

Jason IR-2010

The Wind and The waves
Sep 3, 2010
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3
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Hello,
I have a problem, well it's not really me it's my mothers, you see she has a fused ankle on her right foot which means that only her left foot can actualy be used to propel her (using fins) through the water. I was thinking of making a pair of fiberglass fins for her, and me for the summer.

My question is, what angle to the foot pocket should I make the right fin blade at? Because when you stretch out your foot it reaches an angle of 20-30 degrees off horizontal (if your foot at rest is 90 degrees). Would I have to make the fin with a 70 or 90 degree bend in it to compensate, I know that seems mad but my mothers foot is completly inflexible.

I have seen the posts on how to build a fin so there is a good deal of info on how to do that. If there has been anybody with the same problem please get back to me as both of us would greatly apprectiate the help
 
Reactions: Kars
You are right, the fin would have to have a angle of 70-90 degrees.

Theoretically, I see no reason why the fin should not work for you mom. Making a 70-90 degree bend for the fiberglass blade should not be too hard. However I think most footpocket tendons will not like the 70-90 bend unless it is very gradual. The Mares razor footpocket has the most flexible tendons I know of, but even those might not be happy with a right angle bend.

Also keep in mind that the left and right side fin will be different, so you may need to try several times to get the stiffness to match.

Another crazy idea is to couple the fin to the shin instead and bypass the ankle and footpocket altogether! This will require a lot of ingenuity.

Good luck!
 
I might give force fins a try, I was also thinking of using a hot wire to heat a plastic fin so the plastic at the foot pocket joint is soft and then form it into shape.
Thanks for the advice,
Jason.
 
if you use a shoe like sporasub fins you will be able to do a 70 degree fin.
Composite materials don´t like very sharp angles ,´There was a topic on Medfish , about a new type of fins . try to find it. At the time there were a lot of ideas to make a different fin
 
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