Radio Controlled Landyacht
RC Landyachts are great fun and relatively cheap and easy to make at home.
They sail fast, much more like high performance 18ft skiffs or big cats than conventional sailboats.
You do however need to find a big flat smooth open carpark somewhere for a sailing course. Outdoor netball courts could be OK as long as there are not too many wind obstructions around.
The photos above show the progression in designs from 1975 on the left, made with school friend Paul Schroeter, to the 2009 version with enclosed body and wing sail.
The original 1975 version didn't perform too well mainly because the base was too small and sail too tall. It would take off downwind then topple over as soon as it turned, and just wasn't stable enough to sail upwind.
Other designers have come up dimensions that are a good combination of size and stability so these are the basis of my recent versions.
Mast height 1.2m
Radio Control Unit
Only the steering and sail angle need to be adjusted so an entry level 2 channel RC set is OK.
I bought a Futaba T2ER kit from Tate's Toy Kingdom in Geelong for $90. This includes handset, reciever and two S3003 servos. The S3003 servo is fine for steering but not strong enough for sail angle with a powerful sail.
After stripping the cogs one fine windy day I replaced it with a stronger Hitec HS 815BB Mega Sail servo (~$70) which works very well.
100mm Razor scooter wheels work well. 65mm roller blade wheels would be good for a smaller landyacht. Both of these can be bought very cheaply in recycling depot shops or "Cash converter" type shops. They will most likely come fitted with roller bearings and you may even be able to fit new skate board bearings straight in.
These wheels spin freely but don't have much grip so you may find your landyacht spinning out or drifting in decent winds. It's however great fun learning to control or even cause these high speed spinouts.
I now use 210mm diam. wheels with rubber tyres on the back, from a kiddies scooter, giving much more grip, and a 100mm Razor scooter wheel on the front.
Note the wheel mounts cut from 3mm ali angle (Mitre10) and fishing clips used as stay connectors. This photo shows the 100mm Razor scooter wheel.
2 skateboard wheel bearings, glued into a block of wood, hold the rotating steering bolt connected to the front forks. The cords on either side attach to the steering servo.
Mounting the steering assembly at an angle gives smoother steering at high speed.
The body is 5mm ply with just enough width inside to house the servos, receiver and batteries. The cross beam is 2 lengths of 5mm ply laminated together for strength. Glue is West Systems 2 part epoxy wood glue.
This shot shows batteries and extra weights added for stronger winds.
A powerful Hitec Mega Sail servo operates the mailsheet, which alters the sail angle.
However when the landyacht is going fast you just crank it right in no matter what the wind direction.
There are many sail designs possible, ranging from a simple triangle to a sail with more roach and battens to a full wing sail. All work pretty well.
But it's much easier to start with a simple cloth sail made with kite material using your sewing machine. I tend to use the wing sail in steady 10kn+ winds and the battened cloth sail in lighter winds.
The wing sail is made from balsa ribs, beech dowel leading edge/mast, PVC top cap and covered with heat-shrink wing covering plastic. The aerofoil profile is NACA0014 meaning it is symmetrical, maximum thickness = 14% of the chord length and 30% back from the leading edge.
The wing sail needed a trailing edge flap for more power.
Flap angle is controlled by 2 lines running forward to the mast base.
The cloth sail mast is 15mm aluminium tube from Mitre10
The sail cloth is ripstop nylon from Kite Power
The boom is a fibreglass kite spar from Kite Power
The mast base and gooseneck (boom/mast joint) are cut from an old nylon chopping board
Clips and mast cap on the wing mast are PVC from storm water down pipe, shaped by softening with a paint stripping heat gun
More photos - Wing sail video - Cloth sail video - Onboard video