Monday, September 5, 2011

Seat back finished, prop started

As I have mentioned, reworking the seat back has been one of my most time consuming duplicated efforts.  My original design had an integrated headrest with a few extra panels to create this.  Rick and Mike decided against this in the end for various reasons, including ease of indoor storage, so I too revised this design and cut a new top panel with no head rest.  I had this completely built and ready to put on the hull when I decided it was not a good long term solution so I would try the replacement now.  I decided to cut the new panels out of cardboard because I barely had enough scrap to use and I could not afford any mistakes.  In the end I am happy with the result and would definitely use this shape again.  The hatch in this new section is to be fastened with wood screws and is only for maintenance access, not storage.
The gearbox fits in nicely.  You might notice that the hole pattern is not perfectly parallel with the slot.  I don't think the software is well suited to help a designer verify things like angle between two surfaces.  I am quite inexperienced using it, so if there is an easy way, I don't know how, and the end result is my accuracy was off a quarter inch or so.  Fortunately the slot was oversized and still had clearance.  Once everything was together I could see that the crank arms had about an inch of clearance between the inside of the arm and the boat.  It is much more than I needed and it makes my feet farther apart than necessary, but at the time I wasn't sure how far the arms would slide up the tapered shaft, so I erred on the safe side.  Now I would cut the shaft much shorter.  Incidentally, I also swapped my 170 mm arms for 145 mm arms (I had ordered both at the start to be safe).  I have pretty big feet, and it will be very close to hitting my heels on the boat.  Someday I will try, but I didn't want delays on my first outing.

I also started my prop using the same folding hub design Rick has been using.  In fact, he provided a part I could try.  I bent the blades per my design spec, but I did not have time remaining to grind them before we needed to pack up for the holiday weekend.  I assembled them to the hub and to the shaft and that will have to do for the first trial.

Time up to this point:  My motivation to track accurately is fading, but I am at around 150 hours, including around 20 hours of reworks.

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