Stretched Cables? Fins Misaligned

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What next?!?!

Two broken masts, (replaced),

A resulting compromised sprocket hole (sprocket replaced)

A torn fin (temporary glue fix)

This evening I was out on the Big Lake testing my sprocket alignment and easing into a very warm, (rare) flat water tour. After a comfortable 6 mile voyage, I encountered a sleek, efficient-looking sea kayak travelling an average 3 - 3 1/2 mph between my Outback and the shore. (I carry a GPS unit) After about a mile of our parallel paddling (er, pedalling), I kicked it into another gear and started an uncommunicated race. The sea kayaker got the hint and increased his ryhthmic stroke in an attempt to match my speed. After a half mile, I lost all sight of him and continued until I completed one mile at an impressive (at least to me) 5.2 mph average. Then I finished the evening watching a beautiful sunset and cooloing off.

It wasn't until I slowed to about 2 1/2 mph that I noticed this "thumping" sound coming from just under the drive unit every pedal stroke starting about 2 1/2 - 3 inches from maximum leg extension. Well, this was MOST annoying!

When I pulled the drive unit from the boat just prior to beaching for the night, I examined the drive while "hand-pedalling". I hadn't noticed before, but my fins do not come to a horizontal position when the pedals are extended away from each other. Instead, they form a very wide "V". I think this might be the answer to the rythymic banging sound I experienced following some extended, perhaps excessive force applied for that rather fast one mile. Fins slapping the bottom of the boat!

Question: (finally )

Could I have stretched the cables on the M-Drive to cause the chain and sprocket to over-extend the fins position?

Some other explanation?

Anyone else have this experience??

Thanks again for the attention, . . . . and apologies for the long post,

- Mett

Hi Mett,

With your pedals fully separated, the fins do normally form a "V" shape. The noise could very well be hull slap. In some hull types it's not unusual.

Is your pedal position too far back? Normally you want full leg extension without hitting the stops. This is actually the most common problem.

Here are some other possibilities:

Is this slapping on both sides or one? Front or rear fin? Insert the drive in your hull and watch the fin action for contact.

If slap is on one side, look for a chain skip or misaligned chain.

If slap is front fin, both sides, check for excessive fore and aft rocking of the drive in the well. If so, try a small rubber tip or tape on the front of the drive and see what happens (you need some rocking front to rear though -- don't take it all out).

Is there anything else on the drive that looks amiss, loose, cracked or broken?

BTW, great speed run!