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Discussion in 'Boat Design' started by Guest625101138, Jul 14, 2008.

  1. Guest625101138

    Guest625101138 Previous Member

    Ian
    Not hard to come second in the division because there were only two boats classified UNR1 OV50. The other guy just happened to be the overall winner in the Full-distance Open. I was happy with 14th out of the 69 starters.

    His boat is boat #16. It is the very long boat in the foreground of the photo at the start of Day1. My estimate is that it is well over 7m long and would suit his weight and power. It is not a conventional kayak as it is longer than any standard kayak for single paddler that I know of - hence the unrestricted classification. It is not a surf ski.

    The length of V14 is close to the lowest drag for my weight and power level. The best way for me to go faster is to get the weight even lower and get rid of the shaft strut. The success of the folding prop enables both of these possibilities.

    I have attached an image of a boat I am working on for my sister. If it works out well I will build a slightly longer version for me. The hull will be almost identical to V14 but it will have the drive and seat integrated with the hull. Should also reduce windage.

    Rick
     

    Attached Files:

  2. Guest625101138

    Guest625101138 Previous Member

    Leo
    A good deal of my gratitude goes to you for Michlet/Godzilla. It is satisfying to know that I am close to the optimum hull. I have a sense of satisfaction when others complain about my boat being lousy for drafting.

    I have little doubt that the flat bottom of this V14 hull (constrained chine) is better than the "optimum" rounded chine V12 hull (no chine constraint). There is a slight weight advantage with V14 being shorter but even in the 10 to 11kph range I am getting a little lift rather sinkage. At higher speeds I do not have to work particularly hard to leave all the paddlers at the start. No doubt legs are better than arms for power but my start group had a couple of young and fit guys in very light/fast racing kayaks. (They nick-named me Lance for my fast starts)

    I am glad you enjoyed the report.

    Rick
     
  3. I57
    Joined: Feb 2008
    Posts: 172
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    Location: Melbourne, Australia

    I57 Senior Member

    Don't knock the place Rick, 2nd is 2nd, they don't have to know the number in the group. Problem with 10 year age groups is the big difference between a 50 year old and a 59 year old, thats why in Masters Athletics they have 5 year age groups.
    Design for boat looks interesting, biggest challenge will be getting the weight down. As you have said previously V14 is almost at optimum design, its either reduce weight or look for an entirely different approach ( maybe someone out there has some ideas).

    Ian
     
  4. Guest625101138

    Guest625101138 Previous Member

    Nick
    It takes quite a bit to get through the results.

    The toughest race is full-distance. There are half distances and even shorter for Juniors.

    The toughest way to compete is as a single person. Followed by single crew, and then relay.

    As far as I can tell there were two boats faster in actual speed than Tony Hystek's 13.6kph. One was a two person recreational kayak with the same crew. The class has a length limit of 7.5m. The two OV40 guys averaged 13.8kph. The other boat was a K4 that operated with crew relay. It averaged 14.1kph but was not as fast as the K4s in previous years. It would have crew of 4 at any time and 16 to 20 people in the team. Hence you would expect it to go fast. There was a K1 in the open category (no age allowance) who equalled Tony's speed.

    Tony would have been maintaining about 12kph through the water for the entire time. That is quite impressive for anyone let alone a 53yo. I need to get a lot smarter and a bit fitter to beat that.

    Rick
     
  5. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    We saw the photos and we know why they named you that!

    I'm not sure if you can squeeze much better performance out of the
    hull design, but maybe adding a small amount of form drag will help
    your predictions. If you don't believe in form factors then ignore
    what follows :)

    For rowing singles and doubles, Scragg and Nelson found a
    form factor that could be applied to the (empirical)
    1957 ITTC skin-friction formula. Their factor is:

    1+k_f = 1 + 0.0044 *(a_in + a_out)

    where a_in and a_out are the entrance and exit
    half angles in degrees.

    I have also used Prohaska plots to convert their experimental
    data so a factor can be used in conjunction with Grigson's
    skin-friction formula. In that case:

    1+k_f = 1.0289 + 0.0015*(a_in + a_out)

    These factors are only available in my personal version of
    Godzilla, but you can add the form drag after finding several
    candidate hulls to see if it changes their ranking. I'm guessing it
    won't gain you much more that 1%.

    Good luck!
    Leo.
     
  6. Dennis A
    Joined: Aug 2009
    Posts: 41
    Likes: 2, Points: 8, Legacy Rep: 47
    Location: Amersham bucks uk

    Dennis A Junior Member

    Murray Marathon

    Well done Rick

    Both you and your boat have achieved a excellent performance.
    With regard to that troublesome weed on the shaft strut, could you not build the curved shaft into a small skeg that is about 125 mm deep beneth the hull and angled at 10 to 15 degrees, or would this increase the drag to much.
    I was also interested in your comments on flat bottoms and lift.
    I have found that lift can be increased by setting the boat to float with the hull laying at 2 to 3 degrees up at the bow.
    On my 16 Ft Flat bottomed boat that I am at present building, I am using a square stern to create maximum lift in the hope that the surface in contact with the water will be reduced.

    Dennis
     
  7. Guest625101138

    Guest625101138 Previous Member

    Dennis
    I am going to try without a strut, which works OK going forward.

    A little rake on the strut to force leaves up rather than down should work for leaves but there is also curled bark and longer weed that will build up on the strut irrespective of the rake.

    My V14 hull has some rocker and flat bottom sections. At rest it sits on its lines but there is enough rocker and flat surface at the bow to give it slightly bow up at higher speed. I have not measure the lift or inclination but I can notice it in the speed compared with round bottom hull.

    Flat transoms are interesting because they tend to squat first before providing lift. The water under the hull accelerates to the free surface and this higher velocity lowers the pressure under the transom and it sits lower. So you get more bow up but at the cost of the stern sinking deeper.

    Rick W
     
  8. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    If you are willing to send me the offsets etc of the V14 of your central hull I will calculate the sinkage, trim, and the sinkage force and trimming moment for a range of speeds.

    However, I will need offsets above the static waterline so Flotilla can use true offsets rather than assuming that the hull has vertical sides above the waterplane.

    Leo.
     
  9. Guest625101138

    Guest625101138 Previous Member

    Leo
    It will be a very interesting result for me. I feel I am starting to get lift above 3.5m/s. I have never taken it to full power because the folding prop has light blades but I have got to about 4.7m/s.

    See if the attached offsets from Delftship makes sense. It is as a very simple hull form made from 4 flat panels per attached image. The sides flare slightly.

    Rick
     

    Attached Files:

  10. OldNick
    Joined: Dec 2009
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    Location: Perth, Western Australia

    OldNick Junior Member

    Gee Rick that boat for your sister is starting to look like an F1!:cool: You need to make the ama arms in a wing shape now!

    I assume that integrating the shaft into the hull will remove or lessen the problems with a free shaft and no skeg. Since you talked of a lighter prop (remember the logs and rocks!) I was wondering if you could surround the shaft with a foam and composite sheath, actually attached to the shaft, so that the shaft tended to float more when stationary. I know it's more drag but it may solve a problem.

    Nick
     
  11. Guest625101138

    Guest625101138 Previous Member

    Nick
    The main problem I have had with unsupported shafts is having them hit the hull in a turn and taking chunks out of the hull. By mounting the prop aft of the hull it can move about freely. The shaft is spring steel and will take a heap of abuse. With the prop unconstrained it will easily bounce off rocks or logs.

    The prop will be lighter but I expect it to be higher strength for weight with aluminium alloy blades and solid HDPE or nylon hub.

    Attached has a bit more detail on the new design.

    Rick
     

    Attached Files:

  12. portacruise
    Joined: Jun 2009
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    Location: USA

    portacruise Senior Member

    Thanks for the interesting report and pictures, Rick. Good information for us on an extended, rugged test of the folding prop and shaft. You indicated the finish was done with a fixed blade prop, so at least you have good data for improvement on the folder if it was jammed, damaged or lost. The folder is appearing to be an important breakthrough, as I had thought.

    Running without a strut would seem to be the way to go, as you have indicated. That's the way I've minimized weed problems in my low power unit. For reverse, an on board paddle is not glamorous, but eventually gets the job done. Another possibility might be some kind of retractable hook that could deployed ONLY as needed to keep the prop from diving when doing reverse or when beaching.

    I ran across this torsion capable CF tube when looking for ways to further lighten my drive shaft:

    http://dragonplate.com/ecart/product.asp?pID=4107&cID=79

    It is overkill in my application, but possibly HPB capable, maybe in one of the larger diameters.

    Congrats on a good run. I'm sure your design improvements by next year will put the young wippersnappers on notice.

    Vic

    Porta





     
  13. Guest625101138

    Guest625101138 Previous Member

    Vic
    I have been thinking along the same lines with the hook. At least for easy transport to stop the prop from bouncing about.

    For reverse it is not a big deal to use my hands. I can get 3 to 4kph just by paddling with my hands. In the temperature up there I try to stay wet all the time to get the evaporative cooling.

    I am thinking of trying to diagonally wrap an aluminium shaft with fibreglass tape or CF tape to get some bendy but good in torsion. The CF tube pictured does not seem to have any diagonal strands. It is close to the right size and price is reasonably so could be worth a look. I wonder if they have actually measured the torsional compliance?

    Rudders and prop now added. With building it was as easy as drawing it.

    Rick
     

    Attached Files:

  14. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    No luck, Rick. Delftship gives me a mess at the top of the hull and holes in the bottom.

    Instead, maybe you could produce a Michlet file from your Delftship fbm. Temporarily set the draft high so the file contains waterlines above the static waterline.

    Leo.
     

  15. Guest625101138

    Guest625101138 Previous Member

    Leo
    Here is the .mlt file. The draft is set to 130mm. The design draft is 97mm. That is where I am when light.

    Most testing is done in a freshwater lake with depth from 5 to 15m. Temperature up to about 15C this time of year.

    Rick
     

    Attached Files:

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