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Thread: Mystery Oz PDR prototype
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21st March 2010, 03:47 AM #1Prototypes-R-Us
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Mystery Oz PDR prototype
I had a little spare time, so I put together another Puddle Duck from plans and revisions by MIK. This one is a little different and lets see how many differences people can spot. The hull went together in 8 hours, ready for paint. The sailing rig and foils are transferable from my other boat.
Enjoy!
Rick.
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21st March 2010 03:47 AM # ADSGoogle Adsense Advertisement
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21st March 2010, 05:36 AM #2SENIOR MEMBER
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Hello,
This has been one quick build!
The differences I note (but I have no personal experience with the PDR nor its plans):
- off set daggerboard case (on the inside of the air chamber leaving the cockpit uncluttered)
- 2 air chambers on the side rather than one big one in front and 2 smaller ones in the back
- tape / filet construction for the chines rather than chine logs
- 2 mast postions rather than 1
- no curves in the decking
- simplified structure with less cross pieces (in the MK2 version required to support the daggerboard case)
It is getting busy at the PDR front with multiple options now available:
- Storer OZ PDR MK2
- Storer OZ PDR simply version (I don't know what name MIK has assigned to this one)
- Welsford Kiwi PDR
- Michalak Catbox
It seems that PDRs will rule the world!
Looking forward to the performance reports!
Best regards,
JoostLast edited by Joost; 21st March 2010 at 05:40 AM. Reason: spelling error
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21st March 2010, 01:17 PM #3Senior Member
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How is it weight wise compared to your other one?
Does it feel like it will rack more than the other?
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21st March 2010, 03:03 PM #4Prototypes-R-Us
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21st March 2010, 04:54 PM #5Senior Member
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Twisting around the longitudinal axis. I would assume it wouldn't be bad even if it does because it is still a lot more reinforced than the original brick.
I assume it would be a tiny bit more prone to oil canning without the stiffeners going across between the tanks. But it is hard to tell because the full length stiffeners would work differently.
Really, I was just curious because it looks like an interesting change over the MK II version. Actually a pretty radical difference. With that much timber gone, I would have thought it would work out about the same weight even with the heavier ply.
Playing the what's different game:
Bulkhead 1 open for storage.
Two mast positions
Mast partner solid rather than box built
Blocking on the sides of the mast partner
Daggerboard off center
Daggerboard case with much less timber.
Daggerboard further aft
Flotation with more volume but spread longitudinally
No coaming in the butt when sitting on tanks
About 2/3 of the timber gone.
Curved chine logs gone
Is there a coaming in the front? Can't really tell from pics uniform wood color.
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22nd March 2010, 03:48 AM #6Prototypes-R-Us
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I assume it would be a tiny bit more prone to oil canning without the stiffeners going across between the tanks. But it is hard to tell because the full length stiffeners would work differently.
Really, I was just curious because it looks like an interesting change over the MK II version. Actually a pretty radical difference. With that much timber gone, I would have thought it would work out about the same weight even with the heavier ply.
The side decks are a bit wider and because they tie in to the rear transom corners, this mitigates a lot of twist, plus the fordeck is one piece for the entire width of the boat. This, along with the framing for the front bulkhead really prevents any twisting. There was an additional piece of framing added to the top of the daggerboard case that was not installed before the picture was taken.
I used 1/4" fir plywood instead of the lightweight 5.3mm lauan, so I think this attributed to most of the weight gain. I used the 1/4" for the bottom,transoms and the airtank sides and the 1/8" for the decks, daggerboard case, bulkhead and side panels.
Because there was a lot of extra plywood, I was able to cut out all 4 side and airtank parts at the same time, and plane them down to the lines. This really sped things up with the build. I preinstalled the gunnels and the framing for the transoms and bulkhead. There was enough timber there to glue and screw (airstaple) the parts together to hold its shape. Then I was able to duct (gaffers) tape the bottom down to the sides and fillet the inside just like I did with the Quick Canoe 155. A little fiberglass tape on the outside chines after the fillet had cured, plopped on the decking which was cut oversized and trimmed it out with a router.
Voila! A really quick PDR build with many of the originals benefits, plus a few added bonuses.
Rick.
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22nd March 2010, 02:06 PM #7
Howdy David,
The thing that allows boats to rack is the lack of enclosed spaces - once a volume is enclosed that area won't rack much ever again.. The original OZ boats were a big improvement over most of the current ducks at the time.
When we reported on the forum we were going for much lighter ply a number of builders warned us against it as they were finding the boats did Wrack and Oilcan.
The Oz mk2 doesn't have a whisper of it. at one stage the biting midge and I stood on diagonally opposite corners and there wasn't a whisper of twist apart from a little bouncy feeling through a very small dimension.
That boat had the bow tank and two stern tanks each side. There was a section about 3ft long in the middle of the boat that wasn't tanked so that was the most flexible bit, but the side decks helped keep the tanks in line.
With the mark 3 the full length tanks will make it the original immovable object.
With the oilcanning - I was drawing in beams across the floor which would require cutouts in the side tank faces, but Rick thought he would give it a shot without. Seems to have worked.
I am pretty happy about that.
MIK
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22nd March 2010, 02:12 PM #8
Now that is a pretty impressive list!
The front bulkhead is open for aesthetic reasons too. Drawing it closed looked real boxy and ugly, but looking through gives just enough feeling of the boat's rocker shape to make it look cute. And it is nice to see what the mast is doing too - I like that aesthetically as well.
There is a coaming at the front of the cockpit. The offcentre case is just far enough over to allow a half inch wide coaming down the sides too if desired. I would probably put one on because even a tiny coaming prevents quite a lot of nuisance water from coming aboard!
MIK
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22nd March 2010, 02:24 PM #9Senior Member
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Well, I have redrawn the MKII enough times I could do it in my sleep now, so the differences were pretty easy to pick out (Sure wish I had done that before I actually built mine. I would not have made as many mistakes.)
Looks really nice and makes a really good addition to the fleet.
Looking at it, I keep seeing a movable thwart that rests across the tanks,
A couple hangers on the inside for oars,
and a sleeping mat in the bottom.
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22nd March 2010, 06:28 PM #10
David,
That's it.
The only thing you got wrong is the offcentreboard is no further back than the centreboard. It is just that it goes up to the deck so that's where the visual reference point is.
With the Mk2 it is the cockpit that is the reference point and the foredeck is not mentally added.
Yes, I think most of it is in the choice of material. The real extra area is the extension of the side tank faces inside the cockpit forward to the bow. That is where the extra sheet comes in.
The idea is to appeal to those who had money but less time. But I had noticed over the last few years the Americans in particular had few worries or hesitations about going out to buy another sheet of ply. So started to understand it wasn't as big a deal as I thought it was.
The Mk2 concept is still the best fighting machine.
MIK
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23rd April 2010, 07:07 AM #11New Member
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Suprise from the off-center board?
With the board in one of the side tanks, is there any possibility of a nasty suprise for a rider / sailor in the event that the little duck decides to go wandering into shallow water?
jtz
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23rd April 2010, 11:18 AM #12Prototypes-R-Us
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In my opinion, there would be no more of a suprise than in a MKII Oz PDR. It uses the same daggerboard, and the case is supported at least as much as a centrally mounted case. It is always a hazard to run aground in any boat that does not have a pivoting board, but at the speeds we are talking, the impact is usually not dramatic, just embarrassing!
Rick.
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23rd April 2010, 12:20 PM #13New Member
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23rd April 2010, 12:28 PM #14Prototypes-R-Us
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There is a slight issue with the bow angle on the MkII which was a misunderstanding of the rule interpretation. The new bow angle does not allow the boat to fit on three sheets of ply. I am not sure if MIK will be offering MkII plans until this gets resolved. Having said that, there is an option to install a central daggerboard case, which would make the MkIII just as competitive, other than the slight weight difference that the partial 4th sheet of plywood adds. The MkIII is considerably easier to build, in my experience, and could be built to the same weight as the older design.
Rick.
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23rd April 2010, 02:41 PM #15
Howdy,
At the moment there is a lot of rule discussion in the background of the PDR class. I am waiting to see what sort of formula they come up with before I continue drawing up new and better versions of the OZ.
If the rules allow me to do my "best practice" style plans where I can accurately define and control the shapes of all the components that go into the boat then I will design more OZ PDRs.
The design and control issues are critical.
On a sales side they mean the plans are incredibly detailed - my original concept of a boatbuilding course in a book.
Everything just fits - and cutting and measuring errors are unlikely and appear quickly if they have been made.
Also the detail means I don't get a huge number of follow up questions from people building the boat - this means that the workload for me doesn't change much no matter how many plans I sell (or don't).
If the revised rules allow me to do that I will continue with the OZ PDR line.
Best wishes
Michael
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