Mark Milam asked a boatbuilding friend to put together a plywood sail boat based on the OzRacer RV for him. The RV is meant to be a really simple version of my previous Mk2 design.
More about the bigger, more capacious and faster Oz Goose
It is bogglingly wonderful … with lots of the simple corners rounded and exotic woods.
The OzRacer RV is the version with the simpler construction and an open cockpit by fitting a single leeboard instead of the centreboard. it is flexibly set up for family sailing but still sails very well.
The Mk2 Ozracer with the centreboard is still the best for people used to racing small boats who will be sailing solo most of the time.
Mark and his builder have made lots of modifications to the boat and they are thoughtful. In fact I am really impressed.
Hull detail modifications – making a square boat round
The most obvious is the use of rounded corners and big round cutouts in the front bulkhead. When I first saw it under build I thought it would be just too much for the simple plain shape of the standard boat. But, here (I’m invoking Kevin McLeod) they have gotten away with it because of the level of finish and the dazzling woodwork in contrasting colours.
For such a lovely looking boat, there is not a lot invested – four sheets of plywood and timber – but the difference is the amount of effort to make it interesting.
I think it has some of the appeal of an immaculately restored 1957 Volkswagen Beetle.
Fitting a windsurfer rig to a sailing dinghy the Smart way
A second difference was the availability of a nice big second hand sailboard rig. I normally dislike the use of sailboard rigs because people don’t understand that you have to support them at the boom level – like someone sailing a windsurfer.
Eliminating the risk of the mast breaking because of improper support
If you support at deck level like a normal freestanding boat mast then there is too much load on the bottom of the mast which not only is likely to break the mast. But also it makes the mast bend all wrong for the sail shape as well as putting the centre of the sail in the wrong place for the centreboard or leeboard.
Mark has done it right here! The solution is brilliant. This photo shows the standard mast in place AS WELL as the sailboard mast. It is all explained below.
The OzRacer RV here already has two mast supports built in. The front one for the adult 80+ square foot sail (lug or triangular sprit – both are in the plan) and the rear one for a smaller kid’s or beginners sail (though the lug adult version does reef to a similar area). He has set the forward one up to take the standard rig and the aft one has been modified to take a spar that supports the windsurfer rig at boom level.
Additionally he thought of the brilliant idea of putting a track on the cockpit floor so the rake of the mast can be adjusted. This is almost unbelievably clever!
But isn’t the sailboard sail in the wrong place for the leeboard?
It usually is in the wrong place with the way most people do it. Generally you can’t just stick a windsurfer or sailboard rig into a dinghy and expect it to work properly. There is a really important relationship between the centre of the sail and the centre of the centreboard.
Usually if a person just sticks in a sailboard rig – the centre of the sail will be too far forward resulting in performance ebbing lee helm where you have to keep pushing the tiller to leeward to make the boat point upwind. It is tiring and it is slow. Terrible for beginner sailors because they will think it is their bad sailing and incredibly annoying for good sailors because they know what good boats are like.
But get it in the right place and the boat just wants to go in the right direction – almost sail itself. It will accelerate cleanly as soon as the sails are trimmed. Makes beginners look good and the experts will be smiling.
So … Mark has moved the rig well back by putting it at the front of the cockpit and also he has done a second leeboard slot on the other side of the boat. Normally the boat just has one position for the leeboard.
But Mark has a second leeboard in a different position. He will use the back one when the standard sails are used (they will be in the forward mast hole in the front deck. And the more forward one when he uses the windsurfer rig.
This means that you have the drag of water sloshing around in two slots. I think he plans to just seal up the unused one with a piece of duct tape stuck to the bottom of the boat over the hole.
Other things
I do notice two little lugs of wood on each side of the cockpit wall. I wonder if they are seat supports?
The boat will sail really nicely like all the OzRacers. The unexpected thing for experienced sailors, who have the instinct that the square planform hull won’t work, is that the boat has almost unimaginable stability for a small boat allowing very big sails to be carried easily. These boats … whether standard rig or modified like this really stand up to their sail in stronger winds but sail right up to hullspeed even with light and variable winds.
Part of the strong wind performance is also from the mast/sail interaction of the standard rig. When Peter Hyndman and I started work on the Oz PDRacers (as they were back then) went through four mast designs and four sail designs until we got it right. The initial masts were too flexible.
Anyway … there’s a slideshow below of Mark’s photos on Flickr so you can enjoy the craziness and wonder and enjoyment of this very clever little boat.
Belated sailing pics
This sailboard rig looks really good. Many of the modern ones have very flat sails. This has good depth and depth position.
Beautiful sail by Duckworks’ sail maker.
Sailing along nicely
Well done Mark Milam and builders SOUGEE SERVICES in Mandeville La.
So … links
This is Mark’s thread on my forum so you can see how the discussion … as the shock and surprise beset us of what was happening :)
This is the plans page for the OzRacer RV.
This is a discussion of rough water behaviour.
And the slide show.
And my big Flickr set.
