I had some good opportunities to test my new winder in the field. I'm declaring it a qualified success, but those qualifications are important, and may necessitate making a new one.
On the good side, it's super smooth to operate. The bearings in the center handle let the line pay out like silk. On the bad side, it's so smooth to operate that line will pay out fast enough to drop the kite out of the air. So that's a mixed blessing. But it's one I can live with and learn to take advantage of.
On the good side, it feels solid as a rock. I really like having a winder that doesn't flex, walk, creep, and move around as you wind line on and off. This one's a serious chunk of winder. On the bad side, it's as heavy as a rock, too. In my mind this is unacceptable since many of the places I fly can only be reached through serious hiking. Erick, who showed me this design in the first place, said my 1/2" ply is way too heavy. He rarely uses material thicker than 9mm. Mine's 12.5 to 13mm. So there's room to improve.
On the good side the larger diameter of the spool means it really takes line in in a hurry when you crank. My original winder was 6" in diameter, and wide enough that that diameter didn't change much as line was wound on. This one starts at 7.5, and the last hundred feet are winding on at about 10.5". That translates to a difference of almost a foot per turn of the winder at the very end of the line. On the bad side this makes for less leverage, but this is offset by the smoother action of the winder.
And I finally ran the compressive hoop force analysis. Without getting into the nitty gritty of the numbers, and being utterly pessimistic, I'm getting a maximum of 220 pounds of inward force per bolt. The shear strength on those bolts is much higher than this, so the real concern is having a bolt rip out of the side plate. But baltic birch plywood is pretty tough stuff. I'm not worried. Still, on a re-design, this is a good number to have in hand.
But that's what I'm looking at: a re-design. I'm planning a hiking trip in July where I expect to hike from 11,000' to almost 14,000' above sea level. Right now my pack is 22 pounds. I need to shave that by a lot. One area I can improve on is my winder. Given that Erick already pointed out some areas of improvement, I plan to work on it and come up with a new design between now and then.
Tom
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2 comments:
I'm glad I found this blog. There aren't a lot of machine shops in Vancouver. I try to learn as much on the internet as I can.
Unfortunately I stopped posting on this blog some years ago. I started a new one at http://tombenedict.wordpress.com mostly to talk about aerial photography, but engineering and machining stuff started making its way into that as well.
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