Flexible Resin

Designed to flex. Composite fins for freediving are catching on.

This is exactly what I am making; however using a combination of fiberglass and carbon fiber. I still have not found the perfect resin though to maintain a flex like this. I would truly value any suggestions on a resin that can flex enough for a dive fin, while doing vacuum infusion.

I think the side rails are very flexible. The bending I see in the carbon part is nothing unusual for a thin part. You can play with the amount of layers to achieve the bending you need.

The Tg of an extremely flexible resin is very low. If the Tg is higher, the resin starts acting glass like instead of rubber like!

Thanks Herman for responding. I am rather new to composites, but I would like to clarify your phrase.

Are you saying, that I should look at the material data sheets of the resin and see what the Tg value is?

And do you by any chance have any suggestions of a resin where I could achive a flex like this:

I am currently working with US Composites 635 with slow hardener and using infusion. I am getting rather hard piece of composite. yesterday I did an infusion using less hardener, and it is currently curing right now. I am still on the search for the “right” resin for this type of application.

This is so cool

Many resins should be able to handle that curvature. It is all about thickness of the laminate (which should be very thin). Try and find a resin with an ultimate strain of 7% or more. Actually most cheap resins are more or less flexible.

Fiber orientation is important too. Try to concentrate longitudinal fibers -if necessary at all- at the neutral axis. Different bindings and stack orders will give you greatly different bending characteristics in thin laminates.

Here is the data sheet for a flexible resin from Sicomin; http://www.mcmc-uk.com/prod-data-sheet/sr-8150-uk.pdf

flex return and part Dynamics are in play here… definitly could improve the product with fibre orientation, placing less need for a flexible resin…