Thread: Building the OZ PD Racer - now renamed the OzRacer

Hi Mik

Nah I don't want to debate the issue, I just wanted to put the question out there to see what the go was. Theres two posts there, one says yes and other says no.

But I was just bringing the cost issue because I remember the club mirrors we had at our old yacht club, if we broke one we'd just slice a bit of timber off anything to replace it.

Anywho, I'll just go with the no battens.

The centreboards question? Was it to see if they'll fit in the PD? I'm actually investigating making my own mould for centreboards (for the cat), I've contacted a cnc company to get some approx dollar figures, but need someone to develop cad drawings for them. Whats your theory Mik, 0008 section or something like a 63008 section, I don't know much about it really, but I'm keen to make my own.

Regards

Matt

Howdy Catsailor,

I stick with theory which is that you don't get to the Reynolds numbers required for laminar flow foils until the boat is quite big or extremely fast.

If you multiply the speed by knots by the width of the foil in metres I seem to remember that the number has to be around 6 or over to make laminar flow foils worthwhile.

I haven't done this for a while - but way back when I was coming to grips with it I went through the calcs and found that it was totally irrelevant for the types of boats I managed to own!! So I might be out with the ballpark calc above.

I imagine your foils on the cat are around a foot or a bit less wide so you have to be doing about 18knots to hit the low drag envelope - and that ain't gonna happen upwind.

If your keel on a yacht is a couple of metres wide than you only need to be doing around 3 knots to make it worthwhile.

However, there have been new families of foil come out since then including the Eppler series and I don't know much about them

Though I used one on my Orange Boat project for Duck Flat - it had a chord of 1.5m so just worth it 4 knots and up and it is reputed to be a tolerant section so supposedly not too bad if going slower. It's thickness was around 13% through to 15% at the bottom of the bulb - just to get more lead in there without the wetted surface going crazy.

Basically the story between the NACA laminar flow section (the 6 digit numbers like you mentioned) were the result of wind tunnel testing - so the original experimentation requires a bit of luck to come up with something good within the framework of manufacturing different sections, whacking them in the wind tunnel and seeing what happens - it is hugely expensive so they can't test that many - so is hit and miss.

The Eppler (and other modern sections) have been developed on computer using CFD programs (computational fluid dynamics) so that allows them to set up an algorithm to generate a huge number of sections and test them all automatically - so it comes up with a much more optimal section.

As far as thickness - I would go with whatever the best guys in the class are using. Generally the slower the boat or the more it is slowed up by waves or if it doesn't have quite enough foil area relative to its sailpower - then you need it thicker.

Anyway the good guys would have settled on something and probably made that info available somewhere - or will tell you if you ask.

But the thing is that the accuracy, surface finish etc have to be perfectly up to scratch. There was a period in the 70s and early 80s where we were using laminar flow foils for NS14s - quite successfully. Now we know that they were not going fast enough to work as advertised. But their profile shape and finish were perfect. The point is that even the wrong foil if it is made more carefully that the correct one may still show better performance.

I'm feeling like a bit of a dud here - so just to wind up - I've only used 2D CAD until recently and am starting to learn 3D - my brain hurts - and I'm not good enough at it yet to do it for you. Give me a few months and I might be able to help (ie find someone else - sorry)

MIK

Hi All,

Just to show you what we are up against with the PDR here is a quote for a carbon fibre mast, boom and spinnaker pole (ex fittings ex GST)

Flying Ant Spars
Not inc GST
Flying Ant Mast - Complete Bare Tube Set Includes the tip panel, mid panel & base panel, sleeving & glass track only 800.00
Track Attachment 220.00
Mast Sanding & Clear Coat 220.00
Boom ( Foil 73 x 33) 330.00
Boom Sanding & Clear Coat 138.00
Spinnaker Pole, 29mm OD 173.00

So let's see - a total of $1881 and that doesn't include any of the fittings.

Oh, by the way - it is a class to get a couple of under 16 year olds on the water. Providing they are not toooo big.

We could get between 6 to 8 PDRs on the water for the same dough - I guess the two kiddies would still be saving up pocketmoney to pay for the rest of their Flying Ant.

I suspect that such expensive items on a kiddies boat says something about their parents who I imagine would be the rulemakers for the type of boat.

MIK

MIK advised me tonight that he has got all of the photos together of me building PDR118 at the spring boatbuilding school put on by Duckflat Wooden boats at Hindmarsh Island.
Gee , it makes a clown like me look like I might even know what I'm doing !<VBG>.
I guess its up to MIK if he makes it for general viewing , although I suspect you could get to it via his site.
If you do get to see it , look for the obvious cockup I , repeat I made , and later , you can see it corrected , no damage done .
I'll admit to being "all at sea" with this initially , I could only improve , and I did a bit , but if I can build a PDR , anyone can !.
You will note in the photos the "book" , it sure helped having such instruction available , and i'm sure MIK is improving it all of the time !.
I was steadily working away on what remains to be done , but we got a bushfire fright last night , so the boat is unfortunately on the "backburner" for now.
But congratulations MIK on putting this thing together (is it called a BLOG?) , its good !.
Rob J.

Howdy Rob,

You can just copy the webpage address (URL) direct into the text on this forum and it makes it visible automatically.

So for everyone who wants to see Rob's (Dopeydriver's) great little boat click here
http://www.flickr.com/photos/boatmik...7594384558679/

I'm just going through and commenting on the 180 photos so the full commentary will be there in a few hours.

MIK

Hi All,

for those who haven't noticed it yet I've started a new thread about the building methods involved in building the three PDRs that I and some others are building at Duckflat over the next month or so.

Basically the methods are a little bit more woodwork oriented rather than the our building of the Mk1 boats on this thread - which involved some trial and error.

The thread on the link below is designed to show some of the details of building a bit more clearly.

That is when I get the chance to take the photos!!!

I'm also having a crack at showing the method drawings from the plans alongside the photos of what actually happens.

Anyway - we will see how it goes

See the new thread Building three PDRacers at Duckflat

Well I may have accidentally not done any work on the original PDRacers for a year now, which means of course that with a bit over a month till the Nationals at Goolway, there's a bit of work to do to finish them off.

This actually turned out to be a bit fortuitous on two counts, firstly we can fix the scrapes and nicks of a year of abuse, and secondly I can con Boatmik to come up here and do the work!

So here we are, one month to go, with two boats to paint, two new masts to build, two new sails to make, a trailer to rebuild, oh and no I've sold the tow car as well!

Anyway while I've been rebuilding the Goat Island Skiff trailer to suit a couple of PDR's (and to make it tough enough for 5000 k's via Cunnamulla, Bourke, Broken Hill - I didn't say our navigation was any good!), Mik's been in the garage:

1) Two primed boats, undercoated, patched and sanded.... Mik starting to think our invitation for his visit was really a trap!

2) Thankfully he finds painting quite relaxing, fortunately he's also very good at it. We decided against spraypainting because: I'd have to do it (and we all know how long that would take) and: brushing gives a great finish within everyone's means and abilities, with a bit of care.

3) The blue pox descends on the fleet. Michael marks all the bits that need particular attention after the first topcoat, and sands with 180 grit on the ROS.

4) Second coat goes on, and Mik continues his meditation

5) Beautiful!!!

Cheers,

P

Thanks Midge for not picking one of the ones where I was sticking my tongue out!

MIK
http://www.pdracer.info

Originally Posted by Boatmik

Thanks Midge for not picking one of the ones where I was sticking my tongue out!

MIK

I have no idea what you mean!

P

Originally Posted by bitingmidge

I have no idea what you mean!

P

DOH!

Soooo ... Mik's staying with Midge ... and they're abusing each other on the forum

What was the fight about boys?

Richard

It's harder than you think!

Every time I go to log on, the cable is plugged in to HIS computer (and vice versa). So replying to one another is a serious logistic nightmare!

The road to Goolwa is soon to be paved with little yellow boats!

P

A somewhat sobering look at the actual costs:

While Michael's been here and hard at work turning the white primer coats of the boats into a nice shiny yellow, and the new the new white polytarp arrived for the new sails yesterday, a special Duck Flat purchase that's much better than the old blue ones. Cost $35 per sail though,
nearly $20 more than the old blue ones (ouch! ).

We're about to build two new masts to the new plans (there goes another former pergola ). This will be useful as I never did get round to fixing
the one we broke, so we've had to resort to sailing one boat and towing the other for quite some time now.

The trailer is almost together again.

I pick up the new car tomorrow (didn't have anything that could tow a trailer any distance with any guarantee of arriving in one piece).

So far the costs of the "cheapest boat in the world to build" look something like this

Two PDRacers (each) say $300.00 (well we've replaced the masts and sails and painted them in a really nice marine paint after all).

Fix the boat trailer - $250 in parts, tyres, bits and pieces (originally cost $40.00 twelve years ago.)

Car to tow the thing with (new Suzuki Grand Vitara) $32,000.

6,000 kilometre round trip to the first Australian PDR Championships in Goolwa,10-12 March, through the inland, and back via the Great Ocean Road, Gippsland Lakes and the Victorian Alpine country......PRICELESS.

If nothing else, I'm hoping to pick up a PDRacer record for the furthest travelled to a regatta this year, and maybe one or two other things along the way!

Cheers,

P

The road trip begins....

In the meantime I have a bunch of pictures to upload, more on sailmaking, "how to" on el-cheapo signwriting using photo-copy stencils, and so on, but it will all have to wait till the grand adventure ends one way or another!

So on to the trailer:

When I built the Goat Island Skiff 12 years ago, I scrounged an old rusted box trailer for free, and bought two lengths of second hand pressed steel roofing purlin for $40.00. One weekend later I had a perfectly good boat trailer using all the running gear and even the rusty mudguards from the oldie.

Roll on a decade or so, and with the new need to tow two boats around 6,000k, it needed work!

Firstly I gave it new springs and bearings, then put a ply "floor" down to try to minimise damage from stones. I bought a tin tool box for $40.00 from Supercheap which is big enough to house all the boards, lifejackets, paddles, sails etc, and screwed it to the floor. This will hopefully also put enough weight onto the trailer to stop it being blown off the road everytime a road train passes in the other direction!

The trailer was designed for a 16 footer of course, so it has a longish drawbar, perfect for opening the back door on the Suzi without hitting anything!

Spars are bundled in polytarp and on the roofrack.

By the way, one boat fits perfectly upside down on a standard 6 x 4 trailer, so don't fret, if you don't own a fleet, you won't need any of this.

Pics:

1) The load. Rakish angle is produced by the need to get the transoms up high enough to fit the tool box under the hulls!

2) It pays to advertise! Back panel is easily removable to convert the trailer back to carry the GIS.

3) Old sheet of ply on the front will hopefully prevent sandblasting of the paint. The colour looks a bit like an Australian landscape, but it was really left over after I've been spraying some lattice a few years ago.

4) Each boat is tied using ratchet ties, normally I'd use rope and a truckie's hitch, but I needed a really simple solution, and passing the ties through holes in the beams located everything easily.

For a real nautical look, I added Baggywrinkles over the ratchet bits to prevent scratches!

5) Given the whole classy presentation of the rig, I thought a couple of fins would set it all off, so a few minutes work with a bit of old formply was all it took!

Now of course comes the test!

How far will we get??

Cheers,

P