Has Anyone Tried This........

Was wondering the other day while working on a boat that utilized a twin prop drive system where the front prop is so significantly different from the rear, Has Anyone Tried This.........

How using 1 Turbo ST fin & 1 ST fin I know its been said that the rear fin does less duty since it being fed slightly turbulated wated and then you have the frictional loss factors of the longer fins, but I know theres been much talk on the subject of loose vs. tite & the different settings of front fin vs. rear fin so has anyone actually tried 1 of each or has everyone just said the Turbo ST's are gr8 and we aint gonna screw around like that.

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Fastfish/Geoff
Kayaks Owned>Outback/Mine & Revolution/Wife

Interesting idea - I've never heard of anyone trying it. I wonder what the feeling would be???? I doubt there is much, if any, benefit. It might just be an in-between gear feeling somewhere between the two fins.

I have no idea really (about anything usually! haha_)

My brother tried using a standard finned drive with a turbo in his tandem and reported that the standard finned Mirage drive was "geared" too low to be of use. Might be different with ST fins.

In general, using unmatched fins tends to rock the boat back and forth as the greater lateral thrust of the larger fin is felt. You can get this effect to varying degrees by using one fin only, using mismatched fins or even setting the clews grossly differently.

Having said that, it is possible, to successfully combine a stiffer fin with a more flexible fin (as for example, combining an original Turbofin with a current production Turbofin). The stiffer fin (having less blade twist) is set in the rear position and that clew outhaul is opened up to increase the pitch. The idea, like with the contra rotating props referred to above, is to take advantage of the altered slipstream created by the leading fin.

With the Mirage Drive, this can generate a very small gain but the old style fins are now hard to come by and the gain is probably not worth the trouble for most. I do have a set-up like this however -- need all the help I can get!

My wife and I swap positions in our '09 Oasis from time to time. I weigh 30# more than she does so it does change the waterline length of the boat probably. We have found at the same heart rate/same day (cruising) that we move through the water 1/2 mph faster (gps and corrected pitot) with me in the forward position. On a bicycle and rowing erg I generate about 27% more power (watt meter), at the heart rate we were using, than she does. We both use ST Turbo fins.

We can attain a higher speed with her forward at max output. I feel this is because we can ride higher up on the bow wave with the lighter weight in front.

I suggest sticking with ST Turbos in both positions due to the increased efficiency of those fins. If someone is over exerting pushing those fins just have them reduce the cadence.

Just some thoughts.

Rick

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Just Traveling About