Monday, May 30, 2011

Science Experiment, Take 2

Emilie fell asleep around 8:30 tonight, so I'm filling in for her tonight.  I thought I'd give a real quick update on our second attempt at determining how fast the creek flows under the road.

On Friday I found a 8-10" long 2x6 board in the garage and painted it Home Depot Orange.  I drilled two holes in the  middle of it and threaded a strand of heavy duty jute twine through, then tied it off with a nice bowline knot.  I was pleased with it.  Emilie was not so sure.  I assured her it was strong enough and that we would not have a repeat of last week's failed experiment.  I even stood on the board and pulled up on the line as hard as I could to show her how strong it was.

When we got down to the creek the setup time was a lot shorter because of some of the lessons learned last week.  Lesson #1 don't stand on the line after tossing your "measurer" (Beckham's word) into the creek.  Lesson #2 leave Sanders strapped into the stroller so you don't have to tie up one hand holding on to him.  Lesson #3, know where to stand so you can get the best view.

Everyone was all set.  I dropped the board into the creek and it took off.  I waved at Emilie and got the timer started with only a slight delay.  Emilie waved back and I stopped the timer.  Then came the fun part.  I handed my phone to Karaia so I could go about "reeling in" the board.  The problem was it was fighting hard.  I figured it was stuck on something so I let out a little slack then started pulling again.  Then it freed itself up.  Or so I thought.  There was still a fair amount of pull on the line, but then Karaia started telling me that it had broken.  Apparently Emilie had been signaling to her from across the road.  Sure enough, the tension became less and less until I reeled in an empty line.  Just like last time.  Ugh.

Emilie said the board came shooting out of the culvert then promptly bee-lined it for a large-ish stick over to the side.  When I started pulling back it got caught in the stick.  As I was pulling then letting go a little the jute twine was rubbing on the stick.  As far as ropes and twines go, jute twine scores very low on the abrasion resistance scale.  Away it went.

Beckham and Emilie watched the board head down the creek and around the corner.  The creek crosses through three yards, then back under the road again before emptying into a small pond that mainly acts as a debris basin.  We decided to walk down to the pond to see if the board had made its way down there.  We had a nice walk around the pond, but didn't find the board.  We even drove by the pond a few more times throughout the rest of the day to take a peek.  We never found it.  It must have gotten stuck against some stick, rock, eddy, etc.  I can always paint a new board, but that one worked so well why roll the dice with another one.  Besides it was the line's fault we only got one shot at it not the board's.

And now the part you've all been waiting for, the results.  The board took about 5 seconds to travel under the road, give or take a half second, which equates to 18 feet per second or about 12 miles per hour.  Emilie and the kids were certain it was moving faster than that, but I was less convinced. You'll be happy to know that at a discharge of 25 cfs, 18 fps means only 1.38 sq ft of area are being used by the creek traveling under the road.  The culvert's total area is 12.5 sq ft so there's plenty of capacity left as long as the culvert doesn't clog up with debris.

I'd still like to try the "science experiment" again, but this time with actual rope.  Something strong that can handle a little rubbing against rocks and sticks.  I'd also like to try snagging the board out on the downstream side of the culvert with a golf ball retriever or something to avoid having to fight the creek all the way back up.  If anyone has any other good ideas I'd like to hear them.  We're pretty booked up until probably Thursday, so I'll have time to adjust my approach.

In the meantime, happy experimenting.


Tobi said...

Kevin, you and my brother Danny (PhD in engineering) need to get together. It would have to be alone because if any other people are in the room their brains might explode! Ha ha!

April Weeks said...

So fun reading that Kevin, even though I had had a prior telling, it was fun to read and re-live it. This has to be so fun for the kids too. They will remember it forever.

I'm glad Em went to bed early. I felt bad making her play the "touch" game cause I could tell whe was tired. She is a good sport.