hey rich ,
in the last 6 months ive gone through another one of those intensive periods where i end up trying heaps of different stuff only to confirm what i already knew , but can at least have a deeper appreciation of why and how to add to the intuative feelings i already had …
ive been through a series of fins from thick flexible ones , thick stiff ones , thinner (not blakestah thin) flexier ones and thin rigid ones …
using as a sandwich or filler , core cell , 80 d cell , 60 d cell , 4.5mm ply and 9mm ply …
fabrics were standard e glass 2, 4, and 6 , 200 gram twill weave carbon , hessian , and lastly cotton , couldnt tell you the weight …
plus tried 2 different epoxies , one with a longer pot life , slightly lower hdt, and a lower barcol hardness which gave it a slightly rubberyer feel , 2 polyesters , standard lam res and a gp resin , also tried tooling 2 part liquid urethane …
regardless of flex , , one common denominator was the fins ability to spring back if it did bend , all the floppier softer fins just didnt cut it in , fast sectiony waves that required quick spontaneous manouvers …
the stiffer fins respond way quicker as no energy is lost while the material loads up ,
in certain soft waves the floppier fins still worked fine as long as you had plenty of time to line sections up , and held nice clean arcs that didnt change to quickly in intensity or tightness …
all the stiffer fins gave instant response time (blakestah will like this) even the thin stiff fins responded instantly , but just wasnt as smoothe and fast out the end of the turn , and tended to stagger or make me do my fast drawn turns in stages washing off a touch of speed with each stage …
so many variables to mention , and give details of each combo …
but in a nutshell the light stiff well foiled fins were the winner …
none of the foam filled fins could really handle serious direction changes without some lag , except some carbon/eps combos which i got super stiff …
so many other possibilities as well , because of the board/fin combos …
it comes down to energy transfer …
energy transfers quickest through something that is stiff with a low density …
i started thinking that the weight of the solids had something to do with them feeling slightly spongier or not quite as responsive , but now im convinced that energy wont transfer through the higher density fins quick enough …
your fins are really at the extreme end of your reach , as far as your ability to feel whats happening far away , almost like an extension of your body …
if you were blind and had a long stiff cane im sure you would be able to define more detail at the end of the cane , then if you had a soft rubbery one…
ive always believed that a board should get proportionately stiffer the further away it gets from you , i think that same philosiphy applies to fins as well as an extension of the board , that every part of the board should get stiffer the further away it gets from your center of gravity/mass to give you the most far reaching sensitive feeling of whats going on around you …
dolphins ride the wave in the power zone , if the power of a wave is deeper down , then it stands to reason we can harness some of that with fins that transfer that energy back to us in a more efficient way …
reaching in past the turbulent boundry zone to the clean green water …
i really think tom would agree with the lighter stiffer fin giving more sensitivity as opposed to the heavier stiffer fin …
but i will make that point again that if you have 2 fins with the same stiffness , but one is heavier than the other , the lighter one will respond quicker , not because of lightness or weight but because energy can transfer quicker through a lower density …
also even if 2 fins seem to have the same weight and stiffness , depending on how the molecules are linked , will determine how direct the energy can travel …
the lower the hdt the quicker a polymer based material will reptate …
those thermo softening style polymers and resins with lower heat distortion temperatures dont seem to feel as lively , even tho they feel similar in your hands when trying to bend them …
if making a standard lay up fin it would make sense to put a layer of carbon in the middle , that way as the fin is foiled , even tho the tip gets thinner it also gets proportionatly stiffer in comparison to the rest of the fin , and when doing side fins , putting the carbon on the flat side …
right now im loving my timber carbon combos …
regards
BERT