Saturday, March 31, 2012

OzRacer modified wins Puddle Duck World titles 2011

As many know the world titles have been won the last three years by boats either designed or modified from Storerboat versions. These boats no longer comply with the rules of the PDRacer class ... so you have to make similar changes to Brad Hickman's boat that won in 2011.

  • 2009 - Georgia USA - Shawn Payment in an OzRacer Mk2 
  • 2010 - Canada - Rick Landreville in what is now known as the OzRacer RV 
  • 2011 - Oklahoma USA - Brad Hickman in a modified OzRacer Mk2 changed to fit the current PDRacer rules.  
This photo is Brad sailing his boat very nicely.  The information posted below are Brad's comments of preparation for the event.  He has a background racing conventional boats so took a little time to get adjusted to the lug rig.  But obviously he is quite adapted now.

Another nice side is that the boats are highly robust.  Built as designed every part is extremely reliable over the long term


Brad won from boats designed by Jim Michalak and John Welsford.  The interesting thing is that the professionally designed boats were up near the top of the rankings, though some self designed boats did well too ... I am thinking of Kenny Giles who always sails his self designed boat well too.

Anyway ... over to Brad Hickman ...
While preparing for the race at the Sail Oklahoma messabout I had two concerns. One was I'd been reading about a recently completed Kiwi PDR that was reported to be very fast. The other was some speculation that the 90 square foot OZ rig didn't perform as well in light winds as some light weight production sails with more draft. It turned out neither of those was anything to be concerned about.
The Kiwi with it's 55 square foot Lanteen rig wasn't able to keep pace with my OZ under any conditions, light or moderate to heavy winds. The 90 Square foot balanced lug sail will perform well in light wind if it's set up properly.
The owner of the Kiwi, who also has two OZs, told me there's a racing sail being developed for the boat but he also said that even with the racing sail he doubts he his Kiwi will be able to keep up with my OZ.
Things I did to prepare for what was forecast to be a light wind race, listed in order of importance:

  1. I spent 16 hours sailing my OZ the week prior to the race tuning and training.
  2. I removed the lacing from the yard and replaced it with zip ties (don't know what you call them in Australia but they're the adjustable plastic bands used to bundle wires). I set the zip ties at the middle of the yard for a 12mm gap between the edge of the sail and the yard then tapered the gap to 4mm at the peak and throat to give more draft in the head. I also eased the head tension lashings so there was very little tension in the head. My sail is made of light weight, 3.1 oz, poly tarp.
  3. I got a Laser style mast mount wind indicator. I've tried tell tails at various locations on the sail but could never get them to work to my satisfaction due to the turbulence near the mast. The win indicator (http://www.apsltd.com/c-2322-laser-windindicators.aspx) gave me instant information on wind direction and shifts which I would not be able to detect in the very light winds.
  4. I lightly sanded my bottom and foils with 320 grit wet or dry sandpaper. (Brad means the boat's bottom.)
I wear knee pads when sailing the OZ in light winds and kneel in the center of the boat as close as I can get to the centercase. The boat must be kept flat, even one corner of the transom dragging in the water will slow it down. I also keep any movement minimal and when I do move or trim the sail I do it as smoothly as I can. Abrupt movements can actually stall the sail in light wind.
I attached photos of my sail trim in light wind. The first four are of the head and foot close hauled, the other two are the head and foot on a reach. I have an adjustable outhaul.
Brad
Read more: http://www.woodworkforums.com/f169/oz-vs-kiwi-125432/#ixzz1qeufZQpr
Rick Landreville, the previous champion asked ...
I wonder out loud how transferable that info is with your aluminum (aluminium? Why not?) spars. I have quite a bit of flex with my tapered wooden spars which throw some draft or some flatness into the sail without resorting to retying the sail to the spars. The only thing I change is the outhaul tension on the boom to change the draft of mine, but I am using the heavyweight polytarp (12x12 weave, 7 oz perhaps?). Downhaul tension really loads up the spars in my case. I am using a 6:1 boom vang from my Geary 18 for the downhaul.
How much flex do you get from your yard and boom? They look quite, um, robust!
The photo above is Brad's rig.  The sail is homemade from polytarp for a cost of less than $50.  The OzRacer plans have full step by step instructions on how to make the sails yourself using a simplified method. Some of the sails at the regatta were professionally made or from regular sailcloth at much greater cost.  Brad did use aluminium spars but the designed wooden versions work well too.

Brad replied to Rick
I don't know how the aluminum would compare to wood since with wood there is a wide range of stiffness depending on species, grain spacing, grain orientation, and other variables. The yard I'm using has the same dimensions and alloy that Needlespar uses for the Keyhaven scow, which also uses a balanced lug. The yard is robust but I can easily get enough bow in it to flatten the head with the 8:1 downhaul I'm using.
Your 7oz polytarp is more than twice the weight of the 3.1oz I'm using. I think the heavy weight tarp was a major factor in the "90 sf balanced lug sails don't work well in light air" speculation.
I can change the draft in the head using the downhaul but I wanted a little extra for the light air conditions that were forecast, and fortunately the forecast was right for a change. Using the zip ties I could have quickly changed back to my original setup.
Another thing I've done that I didn't mention is put an eye strap on the yard to run the throat to yard lashing through. It seemed that when I would apply downhaul tension the head would slide down the yard and flatten out before there was much bow in the yard.
I'm still experimenting and looking for the optimum setup so I'm not sure what I'm doing is exactly right, but it seemed to work well last weekend.
I'm looking forward to hearing what Mik has to say after looking at the photos I posted




 The above pic is Brad's boat in a gust.  The lug rig does have more twist than a more conventional racing rig.  But the whole boat only cost as much as a spinnaker pole or a jib for one of the senior racing classes.

The below was Michael Storer's take

My feeling about this is that the OZ plans lead to the putting together of a very good package. Everything is not too far away from how someone would turn up to a national champs in one of the more competitive racing classes - that's where my head was at when we worked through everything from the plan to the rigging setup - it takes decades of lessons from competitive sailing into account.

That is within the constraint of the cheap materials and polytarp sail of course - even though the materials are everyday - and the sail cloth and cutting is relatively crude - the actual detail is quite highly refined - four masts and four sails for the sprit - and the lug was just great from the first one.

The plans cover all that stuff - so that if someone follows the plan they end up with a very sophisticated and optimised boat.

Something that can be raced in a championship next day (almost).

It is hard for someone without the background to put something together that will work this well.

The other side is Brad has also tricked the boat up with a vang and some other adjustments to make it faster still. As you all know I always struggle a bit with the complexity issue - but everyone else seems to decide what they want pretty easily - simple or sophisticated. No probs!

And the practice counts for a lot too. Before the worlds that they won I think rick in Canada and Shawn in the USA spent way more time out on the water than anyone else.

Put with a good boat it is a very effective mix!!!

MIK


Finally ... a nice video of Brad a few months early "motoring" (ie sailing fast) and pulling away from a much larger boat in his tiny 8ft OzRacer.  The main lesson from the OzRacer experience for me is that the hull shape almost doesn't matter if you have good foil shapes and a good sail/rig interaction designed in.  The real advantage of the hullshape is enormous stability that allows it to carry a bigger sail than the Laser.  The stability also makes it an almost foolproof boat for beginners - but it is refined and responsive making it an excellent teaching vessel.






1 comment:

cumberland harbourga said...

Boating Community
GREAT EXPERIENCE IN BOATING!!!!!

The PDRacer, OzRacer, Catbox, Kiwi PDR

The "ducks" are an ideal first boat for adults or ids and a great way to take the first step into boat building as well!

Visit our OzRacer site at PDRacer.info or follow any of the links for a gold mine of free information, comprehensive boat building advice and access to plans and building manuals.

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