Strain Gauge Research

Wednesday 2-19-09

A good day today. The sun was out and it actually felt warm for the first time this year.

Today I received approval from US Team Coach, Nathan Luce, to gather data with US Team subjects following the trials for the world championships. I’ll be at the Olympic Training Center in Chula Vista to watch trials (I have an athlete competing) and will stay for a couple extra days to gather data. April 28 is the target day.

For several weeks I’ve been thinking about the calibration process for the strain gauge. Each paddle shaft is unique and must be calibrated. That involves installing the strain gauge and then calibrating the paddle. I’ll secure the paddle to a pair of stands and then hanging weights from the shaft. The paddle will flex, causing the strain gauge to generate a current. The level of current will be unique to the amount of weight I hang from the shaft.

My plan is to place one stand at the location of the non-control hand and the other at the center of mass of the control hand side blade. Then I’ll hand the weight at the location of the control hand. I’m still sorting out strain gauge location. I prefer to attach it just above the control hand because I can easily and directly route the wires to the sending unit mounted on the shaft. Also, in this location there is less likelihood of water penetration into the strain gauge, which would interfere with the signal. I know the signal will be stronger between the center of mass of the paddle and the control hand, but then wires must be routed over the hand, if the sending unit is mounted to the shaft. I could route the wires over the hand to the sending unit, but this would involve additional wires and require some method to keep them from flopping around and annoying the paddler. Another option would be to route the wires along the paddler’s arm and town their torso and attach the sending unit to the kayak aft of the cockpit. This is a lot more complicated and would probably not work in the canoe, where there is so much more body movement forwards and backwards. So I think I’ll start off trying to locate the strain gauge just medial of the control hand.

It’s critical the stand securely hold the paddle during calibration. It also must be portable if I’m to take this system to the paddlers. For calibration stands, I’m using a standard folding roller stand common in the construction industry, and I’m not using the roller component. Harbor Freight Roller Stand #95621 is the model I’ve selected. These stands are very strong and stable; as they’re designed to hold long heavy pieces of wood for use with a table saw. Instead of using the roller head, I’m installing components that will hold the paddle securely during calibration. The stand has a folding base with a telescoping vertical component for height adjustment. This will allow a variety of paddle position for calibration – horizontal, or at an infinite number of angles.

For the stand placed at the offside hand position, I’ve attached a clamp to hold the shaft securely. This clamp is the same model we use in the Biomechanics Lab at Western Washington University to hold our motion capture cameras to the wall-mounted system - Manfrotto 035C Super Clamp is the model. On a drill press I drilled holes aligned with the clamp on the piece of the box tubing to which the clamp will be attached. To allow the screwdriver to fit through the other side of the box tubing, on a drill press I drilled holes in alignment with the clamp side holes but larger in size. This allows the screwdriver to fit through the larger holes for installation of the clamp.

I’m building a platform on which the blade will rest for the stand positioned under the center of mass of the onside blade. It’s composite fiberglass and when it’s further along, I’ll provide description and photos once it's further along.

Ideas and comments are greatly appreciated.

I’m back home and recovering from the disappointment of not completing my trip. Once I returned, I plugged back into school at Western Washington University and have been working on several projects.

1. I’ve been helping to set up the motion capture system in the Biomechanics Lab. Motion capture is a way to capture human movement into a software system where a computer model of the subject can be created to analyze mechanics. Once the model is generated, changes in position, acceleration and velocity of different parts of the model’s body can be calculated to understand the movement. We built a wall-mount system for 4 of the 7 Qualysis 240 motion capture cameras we use and have the other 3 on tripods. We’ve done a motion capture of a kayaker on a kayaking ergometer (SpeedStroke) and are now working on building the model. Model-building and analysis is being done in Visual 3D spftware.

2. I’m trying to better understand how power is applied during the kayak forward stoke. With the help of Jim Shephard from Western’s Engineering Technology department, I’ve learned how to install strain gauges on the shaft of kayak paddles.
The strain gauge will initially be just on the control hand side, just above the hand. It will be wired into a small sending unit that that transmits the data in real time to my laptop in the coach motorboat. The data is available for immediate review and feedback to the athlete and saved for study and analysis back on shore.
Now I’m building calibration stands. The stands will be used to calibrate each paddle. As all kayak paddles are unique, they must be calibrated. To do this, after installing the strain gauge to a paddle shaft, I’ll place the paddle on the calibration stands. For stands, I’m using the base of a roller stand used in the construction industry. These are portable and collapseable and very sturdy. One stand will have a small clamp to hold the shaft at the offside hand position. I’m using the same clam we used for our cameras in the biomechanics lab. The other stand will be positioned at the center of mass for the onside blade. I making a clamp from fiberglass and foam padding that will closely conform to the shape of the paddle and protect it from harm.
Once the paddle is secure in the stand, I’ll hang weights from the shaft at the position of the onside hand. The readings I get from each weight will correlate with a given amount of force resulting in flexion of the paddle shaft as measured by the strain gauge.
This system will be the basis for my thesis. My advisor is Dr. Kathy Knutsen.

3. For my Exercise Physiology class, Dr. Lorrie Brilla has generously allowed be to take the class as an independent study, as it’s not offered until next fall. This will help me finish my degree more quickly. We meet for about 1.5 hours once each week to go over the material and review projects. My class project will be a review of the physiology literature related to canoe/kayak and similar sports, and to develop a training algorithm for canoe/kayak athletic development.

And last, I am very excited that the International Canoe Federation, the world and Olympic governing body for canoe/kayak racing, has asked me to speak on my biomechanics work at their International Coaching Symposium in Warsaw, Poland. They’re flying me over the last week of February to make my presentation. Not only do I have the opportunity to share my research, I will be able to hear the other presentations and learn lots of new information from some of the top canoe/kayak researchers and coaches in the world. It’s a great opportunity.

10-5-08 End of Attempt

I’ve decided to stop this attempt to circumnavigate Vancouver Island. Faced with a storm season that’s arrived about a month earlier than normal, that includes gale force winds and high seas, a series of similar multiple-day storms coming across the Pacific with a day or two break between, my window to complete the trip has closed. There simply are not enough days between storm systems. I could continue for a while but the logistics of when and where I finish, as well as getting back home, gets complicated.

While I am very frustrated and disappointed in not completing this try, my thoughts are now toward a future attempt. My physical condition has been solid and I am confident I can handle a trip of this nature.

Also, even though I have not been successful, please complete your contribution to support breast cancer research at the Fred Hutchison Cancer Research Center. That’s far more important than whether or not I finish this paddle.

http://getinvolved.fhcrc.org/goto/Dorothy.MacGregor

Thank you all very much; friends from home (including our great staff at Cascade Canoe & Kayak), friends I’ve made along the way and especially my trip sponsors - Current Designs Kayaks, Cascade Designs, Kokatat, and Epic Kayaks - for your encouragement, kindness and support.

10-1-08 Port Renfrew

Port Renfrew

Day 0 nm Cum. 208 nm

Heavy fog all day today out in the strait. Very foggy here in the harbor this morning, sunny mid-day and clouding up in the afternoon. Lots of fishing boats making their way into the harbor to seek protection from the coming storm. I’m staying on shore. Environment Canada has issued a Gale warning through at least Sunday so it looks like I’ll be on shore a while.

Getting to know some of the folks here in Port Renfrew. Bob, what an awesome guy, loaded my stuff and me into his van and drove me up the hill to the motel. Leah, a server at the Port Renfrew Hotel restaurant, is an avid surfer and will represent Canada at the world surfing championships (leaves in 5 days) in Portugal – good lats! Don, at the motel, lost his wife recently and it’s left a huge hole in his life. These are really good and hospitable people.

I met Julie from Auburn at the West Coast Sea Kayak Symposium – what a nice lady. She’s a breast cancer survivor and asked me to tell you about the Fred Hutchinson Survivorship Program for Cancer Patients. It’s another great program offered at the Hutch. Here’s the link:
http://www.fhcrc.org/patient/support/

There are so many wonderful opportunities for those of us who are truly grateful for our health to help those less fortunate.

Here’s the link to learn about my mom who died of breast cancer and how to contribute to help find a cure:
http://getinvolved.fhcrc.org/goto/Dorothy.MacGregor
Thank you very much

9-30-08 East Sombrio Beach to Port Renfrew

East Sombrio Beach to Port Renfrew

Day 16 nm Cum. 208

10:00 Launch at East Sombrio Beach
12:15 Port San Juan Bay
1:30 Turn Back
3:30 Port Renfew

Was making good progress heading for Carmanah Pont in spite of a moderate head wind. Then the fog rolled in ahead of me and I couldn’t see the shoreline ahead. This area has very steep shoreline with few beaches, as well as an off shore shelf that causes waves to form. These are no problem as long as I stand off shore a little way. I stay just far enough out to avoid the building waves. This usually winds up just offshore of the kelp beds. They know where to find the calm water.

But I was uncomfortable with not being able to see shore and find the beach. Also, the forecast on my radio called for gale force winds over the next few days and I prefer not to be stuck on an exposed beach.

So about 2 miles west of Port Renfrew I turned back, paddled to the port and found a motel. It looks like I may be on shore until at least Sunday. Having to turn back and sit on the beach for at least five days is very discouraging for me.

9-29-08 French Beach to East Sombrio Beach

French Beach to East Sombrio Beach

Day 17 nm Cum. 192 nm

10:30 Launch at French Beach
1:15 – 2:35 Lunch at Mystic Beach
5:15 Land at East Sombrio Beach

Scenery is incredible. Terrain changed from volcanic, to sandstone and aggregate, to sandstone. Lots of points jut out into the strait. Into the Pacific Rim Park so no more houses – just wonderful scenery.

Lots of seals and many pop up in front of me to see what I’m up to. A sea otter did as well.
At launch and lunch was able to talk with a few people about the trip and fundraising effort, most seemed interested. At lunch at Mystic Beach, Phil from Inverness, CA took my photo and said he would send it to the blog. Really nice guy on a day hike with his wife. Inverness, CA is a beautiful place on Tamales Bay, where Krin and I honeymooned almost 26 years ago.

Two ladies with local knowledge told me about Sombrio Beach and the camping there. They really like Sombrio. Since I paddled further yesterday, I decided to go on to there and shorten the next day. Thanks for the great tip ladies and the most beautiful camp site yet.

For the past 2 or 3 days I feel like my physical condition is deteriorating – I’m really worn down. Also my right hip is very painful and at times it’s tough to sit up. Also, somehow I took a chunk of skin off my right thumb – who knows. So far all is manageable, but am concerned about longer days.

Another great sunset that I videoed.

09/28/08 Victoria to French Beach

Victoria to French Beach

Day 30 nm Cum. 175 nm

10:45 Launch at Ocean River Sports in Victoria
2:00 Race Rocks
7:15 French Beach

Had a late start from Victoria. Incredible weather all day with sun and no clouds. Flat conditions early so I took a more direct route to Albert, west of Victoria. Mixed currents all day but a consistent tail wind. Following wind waves built throughout the day to 3’ by day’s end. Fun through Race Rocks with an opposing current, so worked my way up through eddies. Very shallow between numerous islands. One in particular off (west) of Beechany Point had a nice shoot to run – fun.

Because of late start, plus French Beach was further than I thought, wound up paddling longer than I wanted and arrived with the setting sun. It was a real race to beat sunset and I really worked hard. The stars are incredible and I can see lights from the Olympic Peninsula across the Strait of Juan de Fuca.