In the type of water you describe, your going to hit something and bend a shaft. It is inevitable. It is also easily fixed (see above post). My fist week out I got her up to 6.5mph with a STRONG wind at my back. It was amazing. Then I hit a stump...and went from 6.5 to 0. Luckily for me the rear fin took the brunt and bent...to tell you the truth I could hardly notice a difference because it did not interfere or overlap with the front fin when peddling.
You will learn from those mistakes... Like how simple it is to straighten a bent shaft. Or preventative measures like Dr.StealHead suggested. (gorilla tape can fix just about anything!). Since that first good bend I have been lucky (or learned) enough to avoid or prevent most other events. As with anything new, after you get a few scrapes on the hull you will learn to relax and to understand how tough this kayak is, and she will become even more fun to fish from.
Congratulations on the new PA...your going to love it!
( BTW - I did build a pretty ridiculous but compact spare parts and tool pack that I keep in the kayak. I have as yet to use a single spare though I feel better knowingly they are there. It is like having insurance...if I did not have it, I would need it...and when I do end up needing a spare, it will probably be that one thing I did not think of!
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