Thread: Mystery Oz PDR prototype

I've had to answer some questions to a few people here in FL who ask whether or not my boat is still legal. My response is and will always be, "I built this boat to have fun on the water and rules or no rules I will have fun on the water. That's what PDRs are about."

I understand some people build these specifically for racing against others and I can see where the rules would make it fair. But when folks start becoming hell bent on winning over having fun I think it detracts from the camaraderie and intent of the class to begin with.

Originally Posted by paulwjax

I've had to answer some questions to a few people here in FL who ask whether or not my boat is still legal. My response is and will always be, "I built this boat to have fun on the water and rules or no rules I will have fun on the water. That's what PDRs are about."

I understand some people build these specifically for racing against others and I can see where the rules would make it fair. But when folks start becoming hell bent on winning over having fun I think it detracts from the camaraderie and intent of the class to begin with.

Well said

Well Mik the rules have been cussed, discussed, and finalized for the time being. Have you decided where you're going from here? I certainly wouldn't blame you if you decided to scuttle the whole PDRacer project.

If you decide to go in different direction with your small boat designs I'd like to make a request. A cross between a PDRacer and Classic Moth scow, an optimized fast racing design that is nearly as easy to build as the OZ Mk 2.

That's my fantasy.

Brad

Originally Posted by Boatmik

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

Hi Brad,

I am still deciding what to do with the PDRs.

The problem is that Shorty is starting to stipulate that the only side panel that can be shown in a plan is the rule side panel.

I would have no problem using it directly except it is not very fair (smooth) and I am very reluctant to draw up something that is not the correct way of doing things. The rule shape is out by somewhere between 1/4 and 3/8" (6mm and 9mm), mostly in the front part of the boat. Most points are only half this distance off.

I spent a half day a few weeks ago fiddling with nails into chipboard looking at the original shape and the ones my computer was coming up with to work out what was fair from the point of view of actually marking out the shape with a batten.

The batten has to be approximately the same stiffness as a chine log or a chine log lamination - so my batten was about 12 x 19mm. The rule with battens is the best situation is if it is clamped to the nails at the end points only and lies fair along the nails, particularly for a simple convex shape like the PDR - no reverse curvature. If there is a part of sudden curvature you might need a clamp on a nail adjacent to it, but using a clamp on every nail shows it is not very fair.

I worked out that you could get the bottom kind of fair if points were moved from the rule points by about 1/8" (computer, confirmed with nails in chipboard) - some up and some down (for a variation of a total of 1/4") but that still left quite a bit of curvature at the first point behind the bow.

Generally it is good for curvature to reduce as you get close to the ends of the boat because that is what a chine log or gunwale is going to do anyhow when it terminates on the bow or stern. The last little bit will be perfectly straight. - or mathematically it will be "tangent to the curve" or both mathematically and boatbuildingly "unrestrained". You should never push on a batten outside the last nail either - if you have ever had a problem getting a gunwale to bend to fit the hull at the very end of the boat ... that is what the designer or builder is likely to have done.

I would use the bottom curve exactly as it is shown in the rules (like a shot) if it was fair (smooth) but I can't bring myself to put things that are bad practice in my plan. "Boatbuilding course in a book" - I have to show the right way to do things.

That it is not fair means there will be variation about how each boat is marked out and how the chine log will take the curve, leading to variations of the range that the rule line is out of fair. Currently my bulkheads and centrecase fit accurately - people are always writing to me excited that the bits that they have cut fit to within a millimetre with the PDR. That is how my building system works.

If I use an unfair shape things will be out by the amount of unfairness - around 1/4 to 3/8" . Also it is impossible to pick up any marking errors. With a fair curve, if one of the nails is in the wrong place you can see it right away. But if the curve is not fair and a nail is in the wrong place you may never pick it up.

Shorty has also said that designers cannot mention fairing in their plans so the results will be variable depending on whether the person knows about fairing being part of normal boatbuilding practice. Some will be faired and some will not.

Be very clear .... this doesn't really affect self designed and built boats much. Everything will be adjusted on the way through and can work well if the boat is really simple - the builder will just adjust things as they go through and their knowledge and the stiffness of the batten and chine log they use will define the shape.

A designer can do a fuzzy plan and assume that people will adjust on the way through, but you can't do a fully documented plan the way I do and make it fuzzy.

The funny thing is that whether a person has used the rule side panel or not cannot be tested by using the measurement rules. There is no way of telling if variations away from the rule shape are from inaccurate marking, innaccurate cutting, the chine log follow a more natural curve when it is bent on or because a person has faired the hullshape.

The rules accept variation because there is a tolerance and that is measurable and practical. That all boats should follow the side panel is something that can never be objectively tested. I could self build a boat that went right to the edge of the tolerance and nobody would know if it is sloppy building or optimisation. They could look at the builder's resume I guess.

So the only functional part of the rule in terms of the bottom curve is the tolerance. The wish that all boats reflect the rule side panel is ... a wish.

Shorty made one really good point in the PDR rules kerfufful (as some were calling it) and that is a boat set up for the mass market should probably go up the middle of the tolerances. That is what I would do with the MK3 - just take enough of the tolerances to fair it but stay as close as possible to the rule panel.

OK ... that is enough on why I find it difficult to draw up a new PDR.

Also it has been clarified that the rules will not prevent boats that are intended to be PDRs from being registered or taking part in events - this is important as it means that building a boat out of spec unintentionally doesn't prevent someone from being part of the group - this is what most have been worried about - that not fitting the rules would mean exclusion.
_______________________________________________________________

Back to where I am actually going with PDRs ... I am have one thing on the way and then will evaluate where to go after that - thinking about it in the meantime.

There is one PDR related step I am going on with. Chuck at Duckworks has introduced me to a chap in Texas. For some years he has been doing after the market bits for sailboats - rudders, masts, tiller, centreboards, rudder boxes. He wants to do kits.

So I will be designing most of a PDR for him. It will be based on the Mk3 - the mystery boat of this thread.

I will be supplying the drawings for all components ... but I shall probably omit the bottom curve completely. The rules say the tolerance is there for builders, not designers (even though it cannot be tested objectively which one it is). So John will mark out the bottom curve in the way he sees as appropriate, make a template, check that it fits the rule tolerance and if it does put it into production.

He is talking to Shorty directly to keep him informed.

I will do the documentation for his kit PDRacer but because it is a kit I don't need to have any dimensions for the hull at all.

Just a set of instructions for assembly.

John is already much of the way through doing a kit for the Disposable, I mean, "Quick Canoe" on a trial basis so he can sort the kit and feed back into the documentation - building guide.

I don't really like the idea that there might be a kit but not separate plans so you can build from scratch - some of the kayak kit manufacturers use that as a marketing ploy - no plans you have to buy the kit hehe - but this is not the intent here.

After that we will see.

Best wishes
Michael

Mik,

I understand what you're saying, I'm using your revised MK 2 plans and I did have to clamp the batten to the nails in two places besides the ends then I had to push the batten a bit beyond the bow end nail.

I am going to brag on your accuracy. When I was ready to cut the side tank panel I used a scrap piece of ply thinking there would need to be some trimming on the bottom curve but like you said it was a perfect fit.

Brad

MIK, now that you've had extensive experience with the PDRacer format, what would you draw if you could start with a blank sheet of paper and had no external rules to conform to? So far I have only read that you would fair the rocker profile.

Here are some of the OZ PDRacer qualities I appreciate:

1. Sophisticated sailing performance
2. Self rescue ability
3. Light weight for easy cartopping
4. Enough displacement to sail two adults
5. Elegant, jaunty appearance
6. Compact size for storage
7. OZ subset rules that keep it all simple and affordable

I'd be very curious to hear what a fresh Storer design might incorporate, just given that set of parameters.

Grant

Originally Posted by BradLH

Well Mik the rules have been cussed, discussed, and finalized for the time being. Have you decided where you're going from here? I certainly wouldn't blame you if you decided to scuttle the whole PDRacer project.

If you decide to go in different direction with your small boat designs I'd like to make a request. A cross between a PDRacer and Classic Moth scow, an optimized fast racing design that is nearly as easy to build as the OZ Mk 2.

That's my fantasy.

Brad

Howdy Grant,

I am still working out what to do. At the moment I will concentrate on drawing up the hull for the Texas kit builder - he will draw up the bottom curve himself and incorporate it in the kit.

The heart and soul of the OZ are the centreboard, rudder, rudderbox, spars and sail design. These are reasonably shiftable to other boat designs. The Son of Goat concept will probably use some or all of those items.

If I could think of a shape that is different enough from the PDRacer but hit the same points then I would go that way. However I think from a simplicity and APPEARING simple point of view the PDR is just about perfect. Also its shape gives in enormous stability - it really is boggling how stable a boat that is 4ft wide its entire length is compared to something that is veed or goes in a bit at bow and stern.

You see, my resistance to doing something "similar" is that I like to do something original always - my handypunt is a stretched version of Bolger's Skimmer, but I was able to incorporate enough differences to give it quite a nice feeling of its own.

So not saying no ... just trying to find a way that I like well enough to say yes!

Just like the OZ PDR has quite a nice feeling compared to the run of the mill PDRacer. So something different would have to be different enough to feel good as a design project.

At the moment I am booked out anyhow. Still have to sort out the plan for the Texas kit - it is a complete redraw of the Mk3 because of rule changes and clarifications. I have a number of outside things to do this month too.

Then I guess the priority becomes the Son of Goat - which was going to be the next boat anyhow once I "knocked out" the Mk3 drawings and documentation. That was supposed to be finished months ago!

MIK

The 12 foot stretched version of the MkIII (PDGoose?) would use all the good stuff from the Puddleduck, yet may be even easier to build because of the relaxed curvature in the bottom would allow bending the chine logs into place instead of laminating them. It should have a long enough waterline to allow it to plane easier, plus it can carry a passenger much easier than a duck would.
Maybe you don't have to reinvent the wheel?

Rick.

Snap!!
I was in complete ignorance of the PDR design shenannigans.
Was about to write that the Mk3 seems to meet most of the original SEB
design request (which transmogrified into the RAID41)
Agree with Rick that the PDGoose would appear to be a good starting point.
Maybe pull nose & tail in a bit to soften the box & choose an ideal rocker.
AJ

Originally Posted by Boatmik

The heart and soul of the OZ are the centreboard, rudder, rudderbox, spars and sail design. These are reasonably shiftable to other boat designs. The Son of Goat concept will probably use some or all of those items.

Then I guess the priority becomes the Son of Goat - which was going to be the next boat anyhow once I "knocked out" the Mk3 drawings and documentation. That was supposed to be finished months ago!

MIK

Hello MIK,

That sounds perfect to me: it will be easy to "upgrade" from a PDR to SOG as you only need to build the hull first to go sailing. A second set of spars and foils can be made at a later state if the PDR is to be sailed at the same time.

Great to hear that SOG will be your next boat!

Best regards,

Joost

Thank you for the thoughtful reply MIK. Can't wait to see your ideas for Son of Goat!

Grant

Originally Posted by Boatmik

Howdy Grant,

I am still working out what to do. At the moment I will concentrate on drawing up the hull for the Texas kit builder - he will draw up the bottom curve himself and incorporate it in the kit.

The heart and soul of the OZ are the centreboard, rudder, rudderbox, spars and sail design. These are reasonably shiftable to other boat designs. The Son of Goat concept will probably use some or all of those items.

If I could think of a shape that is different enough from the PDRacer but hit the same points then I would go that way. However I think from a simplicity and APPEARING simple point of view the PDR is just about perfect. Also its shape gives in enormous stability - it really is boggling how stable a boat that is 4ft wide its entire length is compared to something that is veed or goes in a bit at bow and stern.

You see, my resistance to doing something "similar" is that I like to do something original always - my handypunt is a stretched version of Bolger's Skimmer, but I was able to incorporate enough differences to give it quite a nice feeling of its own.

So not saying no ... just trying to find a way that I like well enough to say yes!

Just like the OZ PDR has quite a nice feeling compared to the run of the mill PDRacer. So something different would have to be different enough to feel good as a design project.

At the moment I am booked out anyhow. Still have to sort out the plan for the Texas kit - it is a complete redraw of the Mk3 because of rule changes and clarifications. I have a number of outside things to do this month too.

Then I guess the priority becomes the Son of Goat - which was going to be the next boat anyhow once I "knocked out" the Mk3 drawings and documentation. That was supposed to be finished months ago!

MIK

Originally Posted by b.o.a.t.

Snap!!
I was in complete ignorance of the PDR design shenannigans.
Was about to write that the Mk3 seems to meet most of the original SEB
design request (which transmogrified into the RAID41)
Agree with Rick that the PDGoose would appear to be a good starting point.
Maybe pull nose & tail in a bit to soften the box & choose an ideal rocker.
AJ

Thanks AJ,

I think a PDR alternative needs something more than that. There are too many other softened boxes around and to do something like that would feel very derivative.

I think the Goose strategy of Rick's is worth looking at - it started to evolve out of the PDR quite organically among the PDR group but the recent shenanigans has more or less disowned all the variants. The main thing the Goose loses is the tiny storage space - it can't stand on its transom against a wall - and the tiny building space.

But I think there would be a niche there.

Best wishes
Michael

Okay, here is a quick video of the new Oz MkIII. Hopefully the YouTube link works.

Rick.

[ame=http://www.youtube.com/watch?v=JF8OOaaSQ8Y]YouTube - ‪Oz MkIII 007.mov‬‎[/ame]
[ame=http://www.youtube.com/watch?v=1Kd8FHPLlGQ]YouTube - ‪Oz MkIII 010.mov‬‎[/ame]
[ame=http://www.youtube.com/watch?v=fe1OUrBugSQ]YouTube - ‪Oz MkIII 009.mov‬‎[/ame]

That polytarp and gaffers tape sail has over 200 hours on it, and that flapping is most likely causing enough drag to affect performance, but it still points pretty darned good for a boat that isn't supposed to. Apparent wind on both tacks is pretty much lined up with the centerline of the hull.

You can also see a glimpse of my messy cockpit, but it is pretty roomy and spacious compared to the MkII.

Any critique on my self-taught sailing skills would be appreciated, but remember, if you can't be kind, at least be vague!

Rick Landreville