Thread: Crash and Burn in a PDR

A wild ride.

Man that is a real bummer. . .

If it is going to happen though, it sounds like you went down pretty spectacularly!

With the cheap Luan ply and the PL holding the rest of the boat together it sounds like you are not interested in resurrecting that hull. You do have a perfectly good rig and set of foils though.

Hmm. . . I see a marine ply and epoxy hull in your future. Maybe a goose?

I feel your pain with the cheap ply, i have to be very careful with mine. The 3 ply stuff is crap!

Don't get discouraged though, it sounds like you were really givin'er when you went down,
I hope to go that fast in my duck someday, even if it does eventually break it.

My condolences,
Al

Reminds me of a couple of situations I've found myself in - funny how it always seems to be a "good idea at the time"......Smart wife, by the way

Very cool, both the mayhem and the lake.

Nothing like testing to destruction to confirm the designers calculations, I'm impressed

Sounds like a fresh start with better materials though can't waste that lug rig and gear, the second build should be a breeze.

Originally Posted by m2c1Iw

Very cool, both the mayhem and the lake.

Nothing like testing to destruction to confirm the designers calculations, I'm impressed

Sounds like a fresh start with better materials though can't waste that lug rig and gear, the second build should be a breeze.

No worries! I have the only prototype Oz Mk III in existance sitting finished in the garage, so the foils and rig will get used probably as early as tomorrow afternoon.

Originally Posted by alzuger

Man that is a real bummer. . .

If it is going to happen though, it sounds like you went down pretty spectacularly!

With the cheap Luan ply and the PL holding the rest of the boat together it sounds like you are not interested in resurrecting that hull. You do have a perfectly good rig and set of foils though.

Hmm. . . I see a marine ply and epoxy hull in your future. Maybe a goose?

I feel your pain with the cheap ply, i have to be very careful with mine. The 3 ply stuff is crap!

Don't get discouraged though, it sounds like you were really givin'er when you went down,
I hope to go that fast in my duck someday, even if it does eventually break it.

My condolences,
Al

I had some good times in that boat. I won the Canadian Puddleduck Championships in it, embarrassed the local Opti fleet, took it all over the West Coast of Canada and even on a road trip to Oregon USA. So it had a good run. I build em quick, use em hard, and put them away wet!

Originally Posted by pdr311

Yesterday I totalled my Oz MkII PDR.

G'day Rick
Boat ain't totalled until Andy Linn has burnt it.
Anyway, built-to-the-edge-world-championship-winning-racing-boats are
expected to have short but glorious lives, with spectacular ends.
You fared rather better than our America's Cup challenger...
YouTube - America's Cup - Boats breaks and sinks

cheers
AJ

Alright!!!

pdr311 - your second photo says it all I think......

For some reason this pic reminded me of Tom Hanks trying to get off his island in "Castaway"

Big bloke in small boat.........check
Small boat in big waves........check
Huge sail.............................check

You just know its going to end in tears !!

Good luck with the rebuild.

Originally Posted by Mr Brush

pdr311 - your second photo says it all I think......

For some reason this pic reminded me of Tom Hanks trying to get off his island in "Castaway"

Big bloke in small boat.........check
Small boat in big waves........check
Huge sail.............................check

You just know its going to end in tears !!

Good luck with the rebuild.

Not necessarily. Some boats are built on the edge of design and some on the edge of materials choice. I'm sure the MkIII will be a better boat all round and would eat those conditions

Howdy,

A great report Rick.

It is interesting how the tendency of most (including me in a prior incarnation) was to think of the size of the sail as being the thing that loads up the hull.

It actually doesn't make a lot of difference. All that happens with a bigger sail is the boat will lay over a bit sooner.

It is the forces holding the boat upright that load up the rig - whether it is a big heavy keel or a similar weight of large Canadian hanging over the side.

Rick first reported this on facebook and David Graybeal made the comment that some extra screws may have prevented the failure. With epoxy I don't think they would be necessary - certainly haven't been deluged with mast step failures - had one on a Beth a couple of years back - there was a gap in the epoxy under the step - and with Rick's it is probably more the glue's fault than anything.

The water cleanup glues are not gap filling and require high clamping pressures to have a really good bond - both of which are hard to achieve in this particular position.

So probably some extra screws are a good idea in highly loaded components when they are not glued with epoxy. The mast step and the centreboard case cleats would be the obvious ones.

The other aspect is that this boat is not totalled. I would have the router out and set to the foredeck ply depth and remove the ply over the framing and partner. The fiddly bit is the cockpit front coaming, but not impossible to deal with. Fix the step and partner and replace the deck.

I think it would be quite possible to have it all fixed within a couple of days and be back on the water. But I don't really want to suggest that too loudly as it would be great for Rick to get some sailing in on the Mk3. I really want to know how it feels with the off centreboard compared to the centreboard on the Mk2. The Mk3 has a little bit more weight too.

Best wishes
MIK

G'day MIK
is it worth maybe adding a couple of 19x45 horizontals on their flats outside
the upper partners to beef up the area ? Especially for fat slobs like me.
AJ

Howdy AJ,

I think glued with epoxy you will have no trouble at all.

The engineering works from the point of view that the bottom of the boat and the deck are both oriented to take improbably huge loads, but you have to feed the loads into them and provide enough surface area so you don't crush the mast locally.

The main thing is that so far there have been no failures with epoxy built boats as the step and partner structure can feed the load into the plywood OK.

But if the strength of the gluing is reduced because of using a non gap filling glue and not having the recommended clamping pressures then either some extra gluing area or secondary ways of taking the load (that might also act as crack limiters) like fastenings can be considered.

There have been two structural failures of the Mk2 that have occured.
Both were cases when glues other than epoxy were used. One was a failure of the bottom ply to centrecase join when the PDR hit a log and possibly the sailor stamped down with his foot when he lost balance; and this one with Rick.

I have no doubts that epoxy would have been a very large number of percentage points stronger in either case - purely because it is more suitable for places where you can't get high clamping pressures and maybe cannot get close fits.

On paper and in ideal tests some of the alternative glues are stronger than epoxy in an absolute sense, but once you take practical situations where the joints and clamping pressures are not so ideal the epoxy way outperforms the alternatives.

This PDR experience seems to validate that point of view.

If over time more data comes through - like a single or better successive failure of the epoxy glued OZ structures then it might be time to look at modifying the basic structure. But that hasn't
happened yet with no failures of the designed structure at all.

So far it shows only that the alternative glues are weaker in a practical sense.

Appreciate the points you make as the discussion is useful.

Best wishes
MIK

Originally Posted by b.o.a.t.

G'day MIK
is it worth maybe adding a couple of 19x45 horizontals on their flats outside
the upper partners to beef up the area ? Especially for fat slobs like me.
AJ

AJ;

I would keep with the original drawings, but stick with epoxy for the glue (no pun intended).
At the time I built my PDR, there was a lot of talk on the pdracer.com site about the difference between a 'North American' disposable build, and an 'Australian' permanent build. A lot of non-designer built boats were built from cross-linked PVA glues such as Titebond II and Titebond III, or polyeurathane construction adhesives such as PL Premium. These boats typically cost less than a hundred bucks, went together in a weekend, with a weeks worth of evenings for painting and fitting out, and they lasted about a season or two. Then you wasted another hundred bucks and a weekend, and built another.
MIK came up with his 'boatbuilding course in a set of plans' with the MkII Oz boat, but specified using epoxy and glass, as well as marine ply and proper boat fittings. This would push the costs up to around $500-600, and because of the complexity of the plans, take about 100 hours to get one in the water for a newbie woodworker.
A lot of the traditionalists balked at the idea of spending that much money on a boat that looked more like a waterbed frame, than a sailboat. Even though the benefits would mean that the boat would no longer be disposable.
Anyways, the point of all this is; I split the difference, and used MIK's plans, but cheapy plywood and polyeurathane construction adhesive. The glue held on the bottom, but the top layer of plywood came apart under the stresses. This, coupled with the fact that the glue I used did not work very well on the end grain led to the mast step failure. Had I used better plywood, and/or epoxy, I would not have a very interesting story to tell.
So what I am left with is a days worth of repairs, on a good boat built with marginal materials. If I choose not to fix it, this would mean the life expectancy of my boat would be almost two seasons, just like the normal PDR's built without plans. Mind you, I most likely have about 200 hours of mostly hard sailing time in it, so its hard to say if I have 'worn out' the boat, or if 200 hours is a normal life expectancy before major repairs are required.
Rick Landreville.