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CP2 goes on a diet



At this point, I know of only 4 ways to make Critical Power 2 faster for my attempt at the 24 hour human powered boat distance record on September 8th, 2008:
  1. Increase my power output over 24 hours
  2. CALM water
  3. Reduce the weight of CP2
  4. Stay very close to course markers and keep the angle between buoys as wide as possible.
In response to item #1 (fitness) - I have been training my ass off and I do plan on increasing my average power output by 10%

In response to item#2 (calm water) - One of the reasons I am planning the attempt at Whitefish Lake in Montana is because it is a large lake and there are always areas of the lake that are sheltered by mountains depending on the direction of wind. I am hopeful that we can pick a day during the week of September 8 to 12th where there is a favorable wind forecast and from a direction that has shelter.

In response to item#3 (reduce weight) - I have shaved 10 pounds off Critical Power 2. Less weight means less displacement in the water and a correspondingly faster speed. Rick and I calculated that 10 lbs of weight reduction would be worth about 3.6 additional kms in 24 hours. It doesn't sound like much but I will need every INCH I can get.

The place I started was the floats. When I first made the carbon shells for the floats they leaked like sieves so we filled them up with expanding foam. The expanding foam expanded more that I expected and it stretched out the side walls. It was also quite heavy weighing in a 4.5 pounds per float.

I hired composites expert Dave Houbrechts to hollow the floats out, insert some Corecell bulkheads, water proof the skin, and top-off with a Corecell top deck. He did a fantastic job! They are now as narrow as they were originally supposed to be and weigh in at 1.6 pounds each.






Next, I replaced the aluminum floats strut with a carbon version. I ordered two carbon tubes and joined them together using a sleeve. To fix the strut to the floats I bonded a carbon sleeve tube to each float. The floats slide onto the strut tube and are clamped down to the tube with some aluminum bolts and washers.

The outrigger strut slides into a sleeve that is bonded to the float. Aluminum bolts through the flange on the floats clamp down the on strut tube to hold the floats tight and level



The outrigger strut fits to the top deck with two wood standoffs and aluminum bolts



I also fabricated a new rudder steer clamp with aluminum and replaced all of the stainless steel fasteners with aluminum fasteners.

And finally, I am well on my way to reducing the weight of the engine itself from 156 pounds to 150 pounds. Overall, this should result in a 15 pound weight reduction which should equate to about 6 km over 24 hours.

In response to item #4 (stay tight to course) - another potential source of drag is veering too far away from my course markers during turns. My tiny 1" wide x 4" long rudder is just too small and won't allow me to stay as close to my turn buoys as I need to. I made a new rudder than is about 2 times bigger than the old one. I need to test this to make sure that there is no substantial additional drag, but there was hardly any difference between my backup very large rudder and the tiny one. I would expect that the increase in drag this medium sized rudder adds would be insignificant, whereas my ability to control CP2 around the markers would be vastly improved.

Remember that on September 8th (or the best weather day from Sept 8th to Sept 12th), you can follow my progress by tuning into this blog. Each blog post will feature the following "24 hour progress dashboard":


Also don't forget to enter the free Nomad hand held computer contest by predicting my finishing distance (online entry form at the blog to the right).
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I was away last week in Durham, North Carolina delivering my son Cody to Duke University where he will be joining the Duke Blue Devils diving team and getting through his first year of computer science. We got him moved into his dorm, acquired his first term books, toured the campus, registered with various offices, got him cards, keys, cell phone account, etc, etc.

Cody and Krista in Cody's dorm room at Duke

It was a bit of a stressful week and a bitter sweet time for Helen and I. We are very sad to see Cody move away, but we're thrilled and excited about this new opportunity for him.

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A huge shout-out and congratulations to my two buddies Greg Bradley and Bryon Howard who both smoked Ironman Canada yesterday. Greg achieved one of his long term goals to break 10 hours and Bryon blasted out a 9:45 for 3rd place in his division and a qualifying slot for Kona!

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4 Responses to “CP2 goes on a diet”

  1. # Blogger dennis

    Nice work on the quick diet plan! Great idea, I am confident you will have the speed and power on race day!  

  2. # Anonymous Anonymous

    Hi Greg.
    Great result in almost a 20% weight reduction.
    How about loosing the inside float and tilting up the float strut by 2 - 3 degree's which will make the shell lean out by about the same.
    When you go around the course you will slightly be leaning outwards and lessen a capsize. Less weight and drag?
    Jeff in the UK  

  3. # Blogger Alex

    Greg, I notice in the fifth photo down the double legged frame going from hull to the back of your seat. Out of interest do you need both legs? and if you feel the need for two legs do you need the strut across the bottom? Surely you could either have a single leg in the current configuration with some triangular plate guessets or perhaps to legs in an inverted V?

    Or is to too late to start welding now?  

  4. # Blogger Bryon Howard

    Sweet work ... 10 lb reduction is huge.
    I'll watch with interest as you shed 5 lbs.  

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