moldybluecheesecurds 2

Friday, May 25, 2007

Why we need more physics education

We got a canoe last weekend. A nice find via Craigslist, it even included some lifejackets (aka PFDs), paddles, and a little trailer. K drove 3 hours round-trip to pick it up and we're excited to have our own canoe at last.

Then came the storage issue. The garage door eliminated jff's brilliant plan to hang the canoe over the car, allowing for quick loading/unloading. Canoe must hang sideways. Okay, then we have to clear the rafters of all the accumulated junk from previous owners (hey, nice golf clubs!). Now jff applies his high school physics and gets a couple pulleys. Gee, for some reason, lifting a 60-pound canoe with a thin rope isn't as easy as you would think.

Jff goes advanced - looks up pulleys on Wikipedia. Purchases additional pulleys and constructs a basic "block and tackle" (and slicing thumb with utility knife). In theory, we now only need to exert 30 pounds of force to lift the canoe. (see image)

After a ferocious battle that succeeding in lifting the canoe to the garage ceiling (30 pounds, my ass!), team Canoe Lift could not cleat the rope without dropping the canoe. This failure despite jff wrapping himself in the lift rope like a mummy whilst K attempted to tie it down.

So, those who get physics - help! What's wrong with the pulley system? Is the solution more pulleys (see image below - bonus pulleys in red)? Counterweights? A patch of grass and a tarp?


Matthew said...

My inclination would be to put the anchored-to-canoe-but-otherwise-unanchored pulley between the canoe and the anchored-to-the-ceiling-pulley. Reverse of what you have illustrated.

It seems as if that shouldn't matter but heck, I'm no scientist, and if nothing else that arrangement would look more like what I can find online. (better documented = easier to debug)

This reminds me of tying a balloon to a light package, and the difference in weight when you hold the string near the balloon vs. near the package. Reminds me as in "I don't understand it really but think it's interesting".

Also, from someone who yearly pulleys his Jeep hard-top into the rafters of his garage: Lift the canoe from underneath, not by pulling on the rope. (If you get the pulleys working right, disregard this, but I never managed that and just found that it's easier to get a good grip on the "load" than trying to grasp and pull on a rope.) Then just use the rope/kleat to hold once it's up.

Sorry for the long comment, good luck!

bbthunder said...

Hahaha! What a great afternoon read and laugh! Sorry it's at your frustrated expense. And ouch, the cut!