Mirage drive adjustment?

I am familiar with the search function and Google but I can't seem to figure out what the purpose of the Allen screws at the end of the fin masts are for.  Just swapped to turbo fins and I don't know what to do with them.  I am certain this has been asked many times but I must not know the proper terminology because I don't see anything.

Thanks in advance!

I don’t have the 180 drive but it is explained on p. 12 of the Hobie manual here

https://static.hobiecat.com/digital_assets/Mirage_Kayak_Manual_-_MD180.pdf

The purpose is to set the tension.

There is a little brass nut at the top of the pre-180 drive fins that serves the same purpose. A well-known smart guy on the Hobie forum did some experiments and he concluded its more efficient pedaling with the tension set loose. I’d assume the same is probably true of the 180 drive.

Gotcha, to set tension.  I cannot imagine how that would really be a factor in peddling as the mast rod is so stiff as it is.  Thanks for the answer.  I wish the manual gave a reason why to set tension and not just a how

Welcome to the Darkside!!! What did you get?

Haha, thanks.  I bought a 2018 outback the day before the 19 came out!  Oh well... I gotta good deal anyway

Gotcha, to set tension.  I cannot imagine how that would really be a factor in peddling as the mast rod is so stiff as it is.

Yeah, I doubt it is a big deal in the 180s, as they look pretty stiff. In case you're interested, here is the discussion on the Hobie forum--the guy who goes by Roadrunner on that forum posts lots of really good stuff:
https://www.hobie.com/forums/viewtopic.php?f=11&t=10176&p=53038

Sweet, I’m hesitant on upgrading the revo... cause who knows when hobie bring out a new revo design.

Thank you for the link, it all makes more sense to me now.