It's best to look for a description of the drive design not in scientific articles on the efficiency of fin propulsion, but in patent descriptions, such as this one:
Not at this scale. 15% more forgiving than 10% at a small increase in drag, theoretically
Thanks for the info, I'm sure there are other equally elegant mechanical solutions. For the time being I'll continue the path I'm on and see where it leads.
Sorry I misunderstood, thought you were referring to my going to 6315 profile from a 6310. Can't really comment on O foil.
It's likely going to continue moving until the following dead centre of the mechanism is reached due to the flow arround the foil. Wether it will move further than that will mostly depend on the inertia of the mechanism, e.g. flywheel etc.
Please Ask AI: Comparison of Thick and Thin Airfoils as Oscillating Foil Propulsion
That's a little bit more complicated than what I was thinking, but <shrug>. I was thinking two phased scotch yokes; the main strut and a pitch control rod running down through the strut, driven by the same chain ring. The mechanical complexity and maintenance requirements of such systems shown in the video (i.e. the exposed sliding pivot block) far exceed those of a conventional shaft and stern tube. There is a reason everyone got rid of sliding bearings for power transmission. The only place I can think of them now is for the crosshead of a LSD and absolutely covered in lube oil.
That's the advantage of a scotch yoke, you can adjust the pitch on the fly. So the strut crank pin would be fixed, but the pitch crank pin could be adjusted, resulting with no change in pitch when it's radius is the same as the strut pin... need to get out my book on mechanical movements....might need a throwout to be simpler.
Of course you're right, Skip, good luck, but... wouldn't it be better to leave just the fin in the water and move the rest (spring, fin rotation stops, etc.) above the waterline, connecting them to the fin via a parallelogram link? This wouldn't require much modification, but it would definitely improve the propulsion.
Smile. Yes, I thought I had the answer early in this journey with a setup that had everything above the water except the fin and strut. It turns out that my facility for seeing all the elements together in their entirety has diminished with age. It turned out there was a lot of motion but the net result was zero.
Excuse my mechanical ignorance. My current setup moves the strut up and down via a pushrod. I considered using a scotch yoke but didn't see any advantage and the current setup is a bit easier to make.
fin is connected to an assembly made up from laminated pieces of G10. I could disassemble the thing and change up things with a file but I'd only gain a few degrees.
