Friday, January 17, 2014

Project NCR PCR and adjustable Seat

PY Hurricane bow to bow with a Swordfish
Lower freeboard by 50mm, narrower and longer than a Swordfish
Double foot well being cut out in favour of heels on deck single foot well

Scuppers being removed as I'll need a very small one on the centre line.

I was given a trashed PY Hurricane with no pedals and extensive hull / deck damage.
I'ts being converted to a 'low volume' single foot well with fixed pedals.
I'm planning for an adjustable seat and as little space for water in the cockpit as possible.
PCR rudder at the rear
NCR at the front. Front rudders generally don't work for the same reason darts don't have flights at the front, but I have a plan which I think will work

More later.

Saturday, January 11, 2014

Swordfish PCR

Some perspective on hull shapes. Right Mako Millenium, Left Swordfish. Bows are level.

I had to remove this deck area to repair impact damage which eased PCR modification.

Foam stringer had broken free of the hull and was way off centre.

Unmodified Swordfish rudder tube looking aft.

At the same time I also removed the foot well deck and scuppers as I wanted my heels as low as possible. That's the bog between the hull and foot well which I had to cut and chip out.

I can't remember the exact amount but heels are 35 to 40 mm lower.

Lead light inside curing resin on fabricated flange for deck replacement.

New deck flange being held in place with everything available.

Here's the PCR angle of around 23 degrees with a long rod in the new rudder tube.

New rudder showing new shaft angle.

Crude vacuum bag using excess cloth to absorb excess epoxy.

The finished foot well with the area in front of the pedals filled with foam. No longer adjustable. Ski in the background is another project.

Bullet scuppers are aligned on the center line in series. The lead bullet is under the foam with a channel to the well.
Tandem Bullets seem to be unaffected by their proximity to each other. Witness mark of old scupper alongside aft Bullet.

Better view of the new foot well

 IMO the PCR rudder has transformed the wave riding performance of the Swordfish as it did for my Millenium (Long story but the Millenium got trashed when I got caught in the impact zone with "Dungeons" breaking at 22 foot. Jetski towing in surfers hauled me out and a ferry found the ski.)
Broken into three. Seat raised 50mm or so. Yellow is discoloured foam to displace water.

 I would never have gone to the trouble I did if I wasn't so impressed with the improvement in my Millenniums performance.

Foot Well:
Also worth the trouble for me. I 'fall over backwards' when my heels are too high so I normally raise my seat (50mm on my Millenium). It's so simple and I'm surprised manufacturers don't do this. The only drawback is that there is more volume to be filled with water when stopped or being swamped but the foam forward of the pedals and the bullet scuppers take care of this in no time.

Friday, June 4, 2010

PCR by Johann van Blerck

PCR is revealed above by the shaft inserted into the new rudder tube.

For three years now I’ve been wondering if positive caster would improve the performance of a surfski on waves. Thinking it through countless times while sliding sideways on waves I couldn’t come up with any reason why it shouldn’t. Paddling on flat water I thought, might be its only drawback but in practice this hasn’t been the case. PCR has no advantage on flat water.

I recently damaged the tail of my Fenn Millenium and decided to build in my PCR (positive caster rudder) idea. I chose a fairly aggressive rudder post angle of 23 degrees as I wanted a definite change and also think the chosen angle is the best bang for buck. Less PC will give less downward force and more PC will give more downward force but less turning force. The implementation was simple enough and achieved simply by moving the lower rudder post hole 55mm further forward and leaving the top one in the deck well as stock.After the deck was remove for accident repairs a block of epoxy glass was bonded between the hull and deck after being suitably drilled. The rudder runs directly in this block.

The stock rudder was simply modified by grinding away and exposing more of the rudder shaft to penetrate the now longer rudder tube and the resultant new gap between the rudder and hull was built up with epoxy/glass and is easily seen in the picture. The current installation limits the steering angle in either direction to just 33 degrees and this has proved adequate on the water.

I’ve only been able to test PCR on ferry wakes for now but from the moment I got onto the first wake I knew I was onto something. The wakes I ride are regulars and I’m familiar with what it takes to stay on them with out spinning out (broaching?). They’re pretty easy to ride if you’re reasonably fit and don’t loose concentration because the spin out point of no return is a fine line between running parallel with the vessel and therefore proceeding in the same direction as the vessel and maintaining an acute angle to the wave. With PCR the fine line is gone, replaced with a broad range of control and feel. Maintaining speed with less paddle effort also seems to be the case with PCR and is possibly due to the fact that previously a large (high drag) rudder angle had to be used to maintain direction while PCR requires far less rudder angle to be effective.

To date I’ve not been able to do a decent downwind but have no doubt that the stunning performance on wake waves will translate into vastly improved downwind control and speed especially on technical down winds where waves have to be ridden at an angle where increased speed and control make a major difference.

How good is PCR? I’ll stick my neck out and say that soon, all open water racing ski’s will incorporate PCR and Molokai will be won with PCR, possibly by next year.

It's almost impossible to photograph PCR but here's a view looking forward with the rudder hard left.

The outline shows the original rudder outline and existing shaft.
Two holes are a simple epoxy crack stitch and the other holes just key the new build to the old.