My quad setup uses 4.75" drive fins postioned slightly aft of the centerline of my torso. My tails are wide and my widepoint back so width between fins may not be relevant to your board. They are positioned close to the rail.
I use small trailing fins about 3" in from tail and at a 90 from deck. These fins are again spaced according to tail width but are close-in to the stringer. Putting any angle to these fins changes dynamics greatly.
Seeking advice re: "quad fins" fin placement
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Difficult question Headwax. I ride a non-conventional board design with the wide point way back. Don't know how much of my ride charecteristics is board vs. fins. But my fin placement has been pretty constant as my board design has changed..so will go back a few boards to be more relevant.
I was looking for a medium between the Aussie tri and the conventional Quad which use two fins as drive and two as bounce fins. Angle and placement is everything. I have a big wave board that is all drive with trailing fins angled and is very stiff. My other boards generally have vertical trailing fins that are loose to a point but fit my style of pump and release.Don't know what the "grail" is for quads but my setup fits my surfing only.
I also don't know if my experience translates but I have done many studies on fluids behavior and performance in industrial pumps and process equipment. In example..very small changes in the leading edges of flights on centrifuge scrolls can me measured in torque (friction) while turning in a fluid/air environment. These edges are almost identical to our fins in being foils. Very small changes in camber or toe will dramatically increase or decrease friction and therefore performance. I think what I am saying is that the finquest is an almost endless combination of patterns to be explored. Just changing the foils on your present setup will affect performance. Add or subtract length and you have another endless mathmatical combo. That is why I have left my fins constant and changed board design to fit the fins.
I was looking for a medium between the Aussie tri and the conventional Quad which use two fins as drive and two as bounce fins. Angle and placement is everything. I have a big wave board that is all drive with trailing fins angled and is very stiff. My other boards generally have vertical trailing fins that are loose to a point but fit my style of pump and release.Don't know what the "grail" is for quads but my setup fits my surfing only.
I also don't know if my experience translates but I have done many studies on fluids behavior and performance in industrial pumps and process equipment. In example..very small changes in the leading edges of flights on centrifuge scrolls can me measured in torque (friction) while turning in a fluid/air environment. These edges are almost identical to our fins in being foils. Very small changes in camber or toe will dramatically increase or decrease friction and therefore performance. I think what I am saying is that the finquest is an almost endless combination of patterns to be explored. Just changing the foils on your present setup will affect performance. Add or subtract length and you have another endless mathmatical combo. That is why I have left my fins constant and changed board design to fit the fins.