I have noticed that with some of the future fiberglass fins the base is loose in the fin box. I was curious if this was a problem with the fins foiling or with the way the box was installed.When this has happened to me I have shimmed the fin, no problems. Also can fin boxes be warped during installation or over time for that matter. It sometimes feels like fins will become more spaced in boxes over time. What is the physical reason for this ?
It’s a lever and wedge scenario. The fin box is a slot. On Futures it’s a long lightly supported slot. The fin root is a wedge, that be design should fit tightly in the original box shape. Now the fin body is a lever arm and it’s working that wedge to spread that slot each time you load up a fin for a turn. The plastic has some memory. But, the longer the slot and the softer the material the less well the slot resists expanding. That’s why Red X uses the strongest most resiliant plastic in the industry for our boxes and we minimzed the length of the slot. Our boxes start out very tight and end up nice and snug after their initial use.
But, the new box I’m developing will have an adjustable slot thickness. So, over repeated cycles you can make the box tighter via adjustment.
Hint for loose fins of any make ('cept those with very small tabs, maybe): put a layer or two (or three) of wax paper around the tab before you insert it. Then trim off exposed excess.