• 15th April 2010 - By greg

    Hello:

    After going through my rough period during some stormy weather at my offshore sea trials in Ucluelet last week, I returned home to go through another rough period – this time it was psychological in nature. I was really upset that it took so little wind (25 knots isn’t exactly a hurricane) to knock WiTHiN onto her side like that. You can read about the trials at this blog post:

    http://adventuresofgreg.com/blog/2010/04/04/offshore-sea-trials/

    And, you can watch the new YouTube video here:

    This was not good. Rick Willoughby and Stuart Bloomfield designed WiTHiN to drift such that the bow points down wind, but in reality she ended up being very balanced and she stays abeam to the wind. That might not necessarily be a problem, but due to my 45 degree heel during the knock down, the rudder was not effective, and I had poor traction on my prop due to churning up air from the back side of waves. I lost control and couldn’t get myself out of that orientation. That’s a problem.

    DSCF0545

    In my mind, the last few months planing for this expedition were supposed to be for focusing on my training and getting ready for the expedition psychologically. But… I found  myself right back in R&D land which was very stressful and frustrating for me.

    The good news is that Rick has come up with some relatively easy modifications which should solve the problem which include a larger rudder, more ballast in the stern and a method to shift some ballast from side to side to trim out any uncomfortable list from wind abeam. I am feeling better now, and I am motivated to keep pushing forward.

    The reason wind can effect the orientation of a boat in water is due to the difference between the center of lateral pressure (CLP) and the center of lateral resistance (CLR). CLP is the center point where wind pushes against surfaces that are above the water line. In my case, this would be somewhere around the middle of my cabin top. CLR is the center point of surfaces that are under the water that provide resistance to where the wind is trying to blow you. When the CLP is in front of the CLR, then the bow will turn to FOLLOW the wind. If the CLP is aft of the CLR, then the boat will turn up into the wind.

    DSCF0541

    In my case, WiTHiN is balanced. So if we want WiTHiN to follow the wind, the solution is to either increase surface area under the water near the stern, or increase surface area above the water near the bow. To increase it would mean to add a sail, and since this is ‘human powered boat’, not a sail boat, that’s not an option. We have decided that the easiest way to increase the surface area under the water line near the stern, and in so doing, move the center of lateral pressure (CLP) back, is to make a larger rudder. The larger rudder surface will also give me a more control in strong winds.

    DSCF0544

    The other way of moving the CLP back, is to weigh the stern of the boat down which will lower the hull in the water and provide more surface and resistance at the stern. I can do this by adding a back-up supply of fresh water bottles to the far stern storage compartment, and make the new rudder a bit heavier than our old one. The other advantage to weighing the stern down with regard to achieving “lee cocking” (when the bow turns to follow down wind), is when the boat rolls due to wind pressure abeam, the lateral area of the rudder and keel actually get smaller and that CLP moves toward the bow which is something we do not want. When the hull itself rolls, the lateral surface area under the water stays the same. I know that sounds complicated, but compare rolling a tilted cylinder in the water. The surface area under the water will always be the same regardless how how far you roll the cylinder. Now imagine a large fin (like a rudder) protruding out of the cylinder. As you roll the cylinder to 45 degrees – or even further to 90 degrees, you are actually moving the fin right out of the water. Now your surface area under the water has been greatly reduced to include only the cylinder body itself. Now you are probably more confused – right?

    DSCF0542

    The other modification we are making is the addition of a method to slide my marine battery from right to left to trim out any list. This is a problem that I noticed during this sea trials trip because I was in WiTHiN solo. During the inside passage sea trials trip, the guy in the cabin (Bryon or myself) could move from right to left periodically to trim out any uncomfortable roll or list caused by the general wind direction. When I’m alone, I have no way of countering that roll, so thought it would be nice to be able to trim it myself by moving ballast. Also, Rick calculated that the effect of moving 110 pounds from one side to the other would be enough to counter the 45 degree roll I experienced in Ucluelet.

    So, I do hope that the addition of a larger rudder will give me more control in wind, and the combination of the larger surface area from the rudder, but more ballast at the stern will result in WiTHiN lee cocking when adrift (bow pointing down wind). Since the prevailing wind direction on my route to Hawaii will be following, I would like to take advantage of that by continuing to point downwind when I am drifting and asleep in the cabin. I am also hoping that shifting the weight of the batteries (about 100 lbs) will help remove some of an uncomfortable roll, or at least trim out the boat such that I am pedaling on a level platform – not that it is level often due to the waves, but at least I should be negating the effect of the wind-caused heel.

    Ken and I are busy working on the modifications now. I am hoping to be able to take-off for more trials late next week if we can get the work finished. All I need is an UNFROZEN lake and some wind. The closest lake that is open is Okanagan lake, so I’m thinking of planning a little training / testing week out there by pedaling from Penticton at the South end of the lake, 120 km to Vernon at the far North end, then back. I can tie up to mooring buoys at night and sleep onboard WiTHiN. Over 3 or 4 days, at this time of year, I am bound to get into some decent winds. I hope.

    okmap

    I would love to get back out to the coast again for more testing, but Clive is unable to take more time off work, and I don’t want to go offshore again without a safety boat nearby. My close call with the rocks last week taught me that there is possibly more that can go wrong when you are close to land than if you are far off shore.

    It’s like when I used to fly. My instructor taught us that ALTITUDE is our friend. If something goes wrong, you have plenty of time to fix it when you are gliding (or even FALLING) from 10,000 feet than if you had just lifted-off the run way. We used to do spins from 8000 feet up. I would kill the engine by shutting the throttle off and pull all the way back on the stick to stall the plane. Then the plane becomes a very heavy rock falling to the ground. But because I had plenty of time, it’s relatively easy to re-gain control by sticking forward, getting airflow over the wings again, then slowly easing back on the elevator and start flying again (or at least gliding).

    I have 2 and one half months to find some big wind on the water somewhere – it doesn’t have to be off shore (ocean), but that would be preferable if I can find someone with a boat who can support me. If WiTHiN handles the situation as expected, then I don’t see any reason to postpone my July 1 departure. If not, well, then we have some bigger problems to solve and I don’t think a departure this summer is in the cards for me.

  • 7 Comments to “Offshore sea trials movie – rough period”

    • Rob Harris on April 15, 2010

      one thing dude. fresh water and salt water will make the craft float different due to salinity. lake trials, and sea trials may not be as accurate as you want.

    • James on April 15, 2010

      Ross Lake in the North Cascades get some pretty wicked winds too. Keep up the great effort!

    • Russell Moore on April 15, 2010

      Will you always want to go downwind? I would have thought that the addition of adjustable fore and aft fins would have been a better solution.
      Also with the movable ballast, what would happen if when you were asleep the boat is forced off course and the ballast ends up being on the wrong side?

    • brisy on April 16, 2010

      fine thinking and explanationof clr/clp situation the idea of moving the battery laterally is fine(no weight added ) i supose you thinked of the possibility of tilting the keel on the side although it’s a lot of trouble for many different reasons the great Tabarly was saying :” long testing of a new boat is useless if well calculated ,because the main troubles or failure may not happen before a long sailing time or peculiar circumstances, just check closely things before you start” i wish you the best
      friendly
      marc

    • Emery on April 17, 2010

      Too bad you can’t steer with the drive leg to get some sort of vectored thrust and drive in whatever direction you steer. Keep on designing and peddling.

    • jamie hastings on April 18, 2010

      when we first saw you i could not belive it. what the heck is that! we were on the south end of quadra island across from campbell river fishing and had to pull up the lines and check you out.my friend mitch flanagan sent me this video and i figure if your realy going to do this you need support.i live in black creek on vancover island and igo fishing all over the island.i have lots of room for camping and will help any way i can. cheers

    • David Tangye on April 20, 2010

      “there is possibly more that can go wrong when you are close to land than if you are far off shore” Yup. Check out where almost all shipwrecks are found 🙂


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