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17th July 2013, 06:58 PM #16
Hi AJ...
Darn good points.
You do make me think about what the difference is. The PDR feels OK in rough water in a way a harem skarem moth would not - the moth would be slithering all over the place at about twice or more the speed, overtaking waves.
The duck is dignified and would never admit to wanting to go quite that fast.
If the duck was faster I would think a mothlike pinching of the stern would be worthwhile, but it is not overtaking waves and risking nosediving into the back of the wave in front. Just too much rocker.
I think that is the answer as to the difference.
Also my biggest criticism is pointed towards pointing nosed boats with very wide transoms as pigs in following seas. Fast pigs when they are not nosediving or veering off, but pigs - considering that it can be relatively easily fixed without losing the speed. At least the duck has similar volume fore and aft
MIK
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17th July 2013, 08:14 PM #17
Pulling in the ends would be tempting, BUT, you would introduce instability, reduce load carrying capacity, and then you need to reduce sail area. We are not looking at a junior Moth here. This is a boat to be sailed by adult graduates of an LTS program. In the breezes to be encountered, I would say leave well alone. There is no sense in creating another NJ (Northbridge Junior), VJ (Vaucluse Junior), MJ (Manly Junior), Cadet or Sabot. Those classes are well established for Juniors. The balance in the beam of the OzRacer makes it an adult 8 footer, which meets the brief for the design from the Concorde Ryde Club. Adults will love to sail the OzRacer because it has the performance for their weight which would all go out the window with nipping and tucking.
Remember, Aussies are quite used to weird sailboat designs. There was the winged keel on Australia II and there were the scow Moths.
DSCN5030.jpg
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17th July 2013, 09:20 PM #18SENIOR MEMBER
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I believe I am not suggesting at all any changes resulting in a junior boat. I fully appreciate that stability comes from the width of the boat being constant at 4 ft and that you cannot change much there before you lose much of that. My earlier question was, would the boat benefit from pulling in the ends just slightly (I was speaking of 1 meter transoms and 1.2 meter maximum width) and having a slight V section in the front 1/3 of the boat and perhaps the aft end remaining an adult boat.
The junior boats you are referring to have extremely narrow bow transoms with very V'd sections forward and much pinched in aft transoms which would indeed mean an enormous loss of volume in the ends and therefore stability and sail carrying ability.
Further, the rocker line of the PDR was created with, if I understand correctly, carrying capacity foremost in mind (in other words, exaggerating, let’s just have a lot of rocker to keep the ends out of the water) and not really aimed at performance. I just don’t believe that the current hull shape is the best possible within 8 ft for a boat aimed at adults and that it cannot be tweaked in any way (the current Moths are very different from 20 years ago and those are again very different from earlier Moths).
And yes, competition sailors don't care much about how a boat looks like as long as it is fast. But we are, most likely, talking about people here who either have more or less firm ideas on how a boat (and let's not forget the rig!) should look like who may have a biased opinion largely based on looks rather than performance. Also, most likely, they are willing to spend a few more $$$ on a sail and such and not as much focussed on operating very low cost.
Just my 2c.
Joost
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17th July 2013, 09:45 PM #19SENIOR MEMBER
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More discussion and information here:
An open 8 Footer for adults? - Boat Design Forums
The thread of the above link was started by someone involved with the CRSC sailing club. This person also makes reference to, it seems, a sprit rigged OZRacer. He seems to have a strong opinion on the OZRacer regarding rig and the bow section.
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17th July 2013, 10:25 PM #20
It wasn't a very informed discussion by anyone of credible credentials was it? Not one mention of the OzRacer, although the PDR was mentioned a couple of times. If any of them had the remotest idea of design, they would have mentioned the OzRacer in the knowledge that 8sq m was entirely feasible. I mean they were even talking of limiting sail area to 6.5 sqm!
This project has OzRacer stamped all over it!!
MIK, I think that discussion needs some input from somebody who knows what they're talking about. Then again, maybe not. Play our cards close to our chests and turn up with the OzRacer on race day
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17th July 2013, 11:26 PM #21SENIOR MEMBER
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I fully agree that the discussion was not very informed.
In view of the PDR, reference was made to (i) the luff of the sail going down to the deck; and (ii) the rudder fittings giving trouble. The rig must be a sprit rig by the description of it. The OZRacer plans have the sprit rig as a standard and describe how to make home made rudder fittings, hence me coming to the conclusion that the OP in the discussion had seen an OZRacer in the flesh (also remember that until just a couple of years ago, the OZRacer was also a PDR and that we are talking about Australia). The rudder fittings, if not made accurately according to the instructions, may end up giving issues. But hey, this conclusion is just my personal interpretation and I may have have come to a completely wrong one.
One observation from the discussion: the boat is clearly aimed at a fleet of mixed ability with races often taking place in a chop and 20 knots. The unfavourable impression of the PDR being stopped dead in the chop may have been caused by a non-proficient sailor not keeping the boat flat. As such I understand the OP's possible concern that it will not allow for good and close racing in the sail club's situation.
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18th July 2013, 01:07 PM #22
Howdy ... good points .. but let's think about what will turn up if there was a serious competition.
There is some difficulty designing a pointy bow 8ft boat that might have to float over 300lbs (could be over 150kg too) of boat and person.
So there will be a bunch of pram dinghies of plywood with curvy sides.
From a pure marketing point of view it is worth doing something different to stand out from the pack.
And the weird thing is, if the boat performs well the performance will be ascribed to the visible differences.
I really think the trick is (having been tricked, more or less into designing the thing in the first place, and then being startled by how well it sails) to rely on the stability and the big sail area and don't be tempted to go in the limited directions everyone else will be heading in.
I'm open to thinking more about alternatives, but four years of development and three iterations of the design are hard to beat.
MIK
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18th July 2013, 01:10 PM #23
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18th July 2013, 01:43 PM #24
I did have doubts about rough water too when we built the first Ozes, but a number of times, including at the Goolwa Wooden boat show, I've been out in all sorts of nasty weather and chop when other boats were deciding not to go out.
It is common experience for the PDRs too. They have a reputation for going out when other boats are doubful about the conditions.
People still talk to me that day at the Goolwa show and how their "concept" of what works in rough water doesn't match the way the boat really goes upwind and down ... see the video below.
It was much the same for me ... I really didn't expect the Oz to perform well at all and we stuck a silly great sail on it because the sail is so cheap and it is the Australian tradition . We really were expecting the boats to be a joke.
But then they weren't.
Also about the load carrying ... I have learned a lot about that. The PDR was derived from the Bolger Brick. The brick was designed for a family and a dog to go sailing in so has a very generous static displacement.
But in practice it is not useful. The high rocker, low length and lots of sail conspire to make the boat sail very close to hullspeed most of the time and it generates a deep wave system around the hull. Any short curvy boat should be the same. But it does mean that the "Brick" shape ... designed to statically float a family and a dog ... is just about right for one big person when the boat is moving. If there was much less rocker it would drag its ends.
Actually ... the really cute thing ... is ... upwind the corner of the bow is pointing straight into the waves. Usually you are heeled in the strong stuff upwind so the waves are well below the windward side of the bow (advantage of the wide bow?) but if something does hit its right on the corner of the bow so you don't even get water in the face as you do with a pointy nosed boat which has the side of the boat at the bow more square to the waves.
Shallow water and much bigger chop than shows in the photo. The left side of the boat is just on the top of a wave and about to drop down the trough.
Brad Hickman
And Brad's video of practice before the pdracer "worlds"
MIK
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18th July 2013, 01:57 PM #25
I couldn't resist ... I put the hickman video up on boatdesign.net
MIK
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18th July 2013, 03:57 PM #26
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18th July 2013, 07:53 PM #27
G'day MIK
You put good arguments up for an unadulterated OzRacer.
It would be nice if both a Mk2 & an RV were there - choice of lay-outs.
Mk.2's insides look more like what a racing club might expect.
The RV clearly "works" and is probably more adult friendly, for us larger bods anyway.
Next question...
What 8' designs are out there already which would be faster around the flags carrying an 80kg adult ?
And should it be named the CR24 or the CR2440 ?
cheers
AJAlan J
Nothing says "Unprofessional Job" so loudly as wrinkles in the duct tape. - B.Spencer
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18th July 2013, 11:02 PM #28
AJ,
A new name is only necessary if there is a special version. Like an RV with centrecase.
Theodor,
There are a bunch of boats now where they like to have X.X as the name where X is a digit and it suggests the boat length.
I am really only joking about that name. But if there was a special boat built ... that would be a fun way to call it.
MIK
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19th July 2013, 07:01 AM #29
CR24 is slightly better than CR8
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20th July 2013, 01:11 AM #30SENIOR MEMBER
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A small boat that I like, never have seen one sailing in real life but looking at the pictures it seems to go alright, is the British Moth:
britishmoth.co.uk
I don't know why, but I like scows a lot (the reason why I built my Chickadee scow, which I must say sails like a dream both in light puffs and when it really blows).
The very large sail gives a lot of performance, albeit is quite a handful in a blow. The hull shape allows for reducing wetted surface but also easy planing.
At 11 ft quite significantly longer than 8 ft, but this was a bit what I had in mind pondering about an adult 8 footer when posing my questions.
Joost
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