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Near screw up!

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Prop Screw up

During the design phase, I misinterpreted the proposed diameter of the prop and only allowed enough room below Within's hull for a 12" dia prop. Ricks design calls for a 17.7" diameter prop! Oops.


I had added a couple of 'safety' inches to the length of the drive leg, but was it enough?

In my computer model, I dropped the drive leg down so that the 17.7" dia prop just cleared the hull bottom. Then I added about 1/2" for the hull skin thickness and took a measurement from the hull floor to the center of the crank. This, I figured would be the highest I could have the crank without having to rebuild the drive leg. The question now, was the 10.75 inches of clearance be enough to circle my feet without my heels rubbing.



I set up a mock drive on the floor using my fiberglass recumbent seat and the drive leg propped so that the center of the bottom bracket was the crucial 10.75" distance from the floor. Then I clipped in and peddled normally. It was good. Whew! My heels are the tiniest fraction of in inch from the floor, but it works. If I need slightly more clearance, I can move my shoe up on the cleat or go with slightly smaller cranks.

This is good because it keeps my center of gravity as low as physically possible. My seat is right on the floor of the hull and the angle of the seat back is quite reclined. Even with my feet circling around the raised cranks, I would think that my over all center of gravity would be not that much higher than standard sea kayak sitting position where your back is straight up and down.

More Rudder Madness:

more progress on that rudder - I welded a stainless rudder tube with some offshoot 'branches' to insert into the hollow rudder shell. These stainless branches will provide something for the epoxy filling to 'grab' onto and will make it pretty strong and stiff when torqued hard.



I also filled the rudder steer tube up with epoxy to further strengthen it and to seal it from the potential of water running into it and down into the rudder shell.



I inserted the rudder steer tube and poured epoxy resin into the rudder shell.





Next on the agenda is to build the drive leg bay, seat and partial bulk heads (for the kayak hull only - I'll extend them up and into the deck when I get to bonding the deck onto the hull).

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1 Responses to “Near screw up!”

  1. # Anonymous Leven Brown

    Hi Greg,

    Rudder looks good. This area of the boat comes under tremendous strain and it is essential that it is strong.

    The project looks like it is really coming along now - can't wait to see what your thoughts are after the sea trials.

    Very best wishes to you and family from this side of
    the Atlantic.

    Leven  

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