Hi all,

As a "teach myself welding" project I decided to make a landyacht. Please note - I am neither a mechanical engineer, professional sailor or qualified welder, so I'm sure there are better ways to proceed. This build does not attempt to comply with any particular class rules - the only aim is to have fun and be competitive with the local blokarts. I think it achieves this quite well.

My father has built a number of landyachts over the years. As each gradually fell victim to rust he refined the design. For my variant I decided I didn't want to rebuild it 5 years from how, so the whole thing is designed to be as rust resistant as possible.



An unmodified windsurfer sail, boom and mast is used. The main frame is 316 marine grade stainless steel. The rear axle is structural aluminium tube, held in place by hose clamps. This means the axle can be easily detached for transport. The wheels are the standard Fallshaw type. The rear tyres are ribbed, hopefully to minimize rolling friction, while the front has the normal wheelbarrow grip for steering. The seat is just a sheet of canvas with a loop in each end, wrapped around a bar in the frame.



Foot steering is used, leaving your hands free to deal with the mainsheet. I splurged on marine pulleys so the sail can be easily tensioned with minimal swearing and messing around with knots. A Harken 57mm ratchet block is used so you don't have to put a lot of pull on the rope.





I took a heap of photographs during the build and drew the whole thing up in CAD as I went, so I'll document the build in this thread.

Tools needed:

*A way to cut 3mm stainless plate and hollow sections. I used a metal cutting bandsaw, but there are plenty of ways to skin the cat.

*Drill press

*Welder

*Metal lathe and standard associated tools. Mine is a smaller hobby type, as long as it can turn aluminium ~50mm in diameter it'd be fine.

If you use the exact same steering mechanism as me you will need a way to put flats on the side of a 20mm stainless rod. I used a milling machine, but a grinder or saw could be used.

Materials:

38x38x3mm 316 square section for main frame
25x25x3mm 316 square section for seat and front steering fork
20mm dia 316 rod for steering
~2 square feet of 316 3mm flat plate for mast support
Thick 316 stainless pipe for mast base - I used 65NB/sch40, but this was likely complete overkill (I didn't actually have a mast at the time I ordered the steel, and figured it'd be easier to make a reducer than have something too small)
50nb sch80 stainless pipe for the axle grip
48mm structural aluminium tube for the axle
various misc short lengths of solid aluminium as described in the build notes - make friends with your local aluminium supply place.

For the stainless I had good luck with Edcon steel - they were able to give me the short bits of pipe etc needed without making me buy a 6m length.

(an aside - does anyone else not get a "preview" button for replies? It's really annoying when trying to splice in photos etc)

The main frame is easy - we just want a triangle, made up of 2 lengths of 38x38, each 1.6m long. The bottom end of the triangle should be about 660mm from one tip of the side to the other. The ends of the 2 lengths need to be cut at an angle so they're square - ~10.2 degrees on my build.

I welded a bar of 316 to hold the frame in place as I worked, but with proper clamping probably isn't necessary.


I also cut a section of 316 diagonally to make an "L" shape. This got welded onto the front to form a nose, which will later support the steering.


The steering frame is fairly easy

It's just 2 lengths of 270mm long 25x25 with a 3rd length welded on at 45 degrees. Before welding 2x 8mm holes are drilled near the bottom of the sides - these are used to hold M8 bolts to hold the wheel in place.

A 20mm solid rod completes the fork. Before attaching the rod, I got a number of M20 washers and welded them together on the rod to form a stop. I welded it so the top of the stop was ~180mm from the end of the rod. Throw the whole thing in the lathe and turn it square, then weld it to the middle of the fork.

A 20mm dia aluminium rod is cut to slide neatly in the bottom of the fork. It is then tapped thru M8 and pushed into the wheel. Some quick washers are turned on the lathe to make the wheel sit in the middle of the rod. These bolts are then tightened to hold the wheel in place. Once everything fits, remove the wheel again.

Now to mount the steering fork to the main frame.


The goal is to have steering that doesn't get nasty speed wobbles, so an imaginary line down the steering rod should ideally touch the ground directly under the centre of the wheel.

I used a short length of stainless pipe, clamped it at the correct angle to the frame, and welded bits to it until it seemed rock solid. A delrin bush was turned and jammed up the middle of that pipe. A second bush was added to the other end of the pipe to minimise sand entry.

Note at the point the other end of the 20mm rod is unfinished and too long. It doesn't make sense to cut it to length and fit the peddles until the mast is installed.

I then decided to do the axle. The axle is just a length of structural aluminium tube. To attach it, I found a short length of pipe that would telescope over the top of it, sliced that length in half (so I ended up with 2x "C" sections), and welded it to the end of the main frame (the frame sits on top of the C-section, which sits on top of the axle). Stainless Hose-clamps secure it in place. If you're worried about the strength of this arrangement, it has held up fine on similar landyachts for almost a decade.



The wheels then had to be attached to the axle somehow. I'd probably do it differently next time as it's very wasteful, but I turned down 2 stub axles from aluminium solid (6061-T6). These were then secured by stainless M10 bolts w/nyloc nuts.



I'm a little concerned about aluminium stub axles as given enough time and usage they will crack. I'll be pulling the wheels off and inspecting them every so often just to be safe.

Now the seat. What is comfortable for me (I'm fairly tall) may be horrible for you, so modify as to your own personal preference.







The frame consists of 5 lengths of 25x25x3 stainless and 2 aluminium rods.

Cut 2 lengths of 25x25 to 530mm and drill 2 8mm holes, 50 and 75mm in from one end. The other end should be cut at 48 degrees. Weld the lengths so the further-est tip is 250mm from the centre of the axle. Cut and weld a third length of 25x25 between the 2 posts at the top. It should be at an angle so a flat side is facing up. Another length 500mm long is welded to the centre facing outwards. This mounts a pulley for the mainsheet and also serves as a convenient handle (if possible drill for your pulley before welding).

Cut and weld the final length of 316 between the main legs of the frame so it is roughly 600mm from the axle. If you are short, move this length closer to the front.

Cut 2 lengths of 20mm aluminium solid rod so that they fit nicely between the 2 posts. Drill/tap the ends M8. You can now get a length of canvas and sew a loop in each end. Thread an aluminium rod through each loop, wrap the canvas around the far seat frame, and bolt the rods in place. You can add or remove canvas to adjust the seat feel.

Nice job
Looks like it should sail pretty well.

If you find the wind surfer boom a bit cumbersome it will sail just as well wit a more normal boom configuration.
As you can see in the pic below.

I love the simplicity of the design!

Thanks gents. I used a windsurfer boom because a number of them were included with the sails I bought. This landyacht isn't as quick to setup as a blokart but it's not a huge pain either.

At this point we have a frame with a seat. I got comfortable sitting and figured out where I wanted the peddles. I cut the 20mm steering rod to the correct length, threw it in the mill, and cut 2 flats where the peddles should go. Make sure the flats are parallel with the front forks!



I then drilled a number of 8mm holes on the flats. These allow pedals to be moved to allow for taller/shorter drivers. They also allow attaching a delrin bush to both support the rod and stop sand entering the mechanism.

To form the pedals: I grabbed some 20mm aluminium rod, knurled it in the lathe and cut them to length. I put an M8 thread in the end of each rod. A short length of M8 threaded rod is used to screw the pedals into each other.

I used 2 pieces of delrin for the top bush. The first piece is crossed-drilled 8mm and held to the steering rod with an M8 bolt. This prevents the entire steering section from gradually working forward. The 2nd piece simply holds the rod centered in the pipe and keeps the sand out.

Now the steering is done it's time for the part that gave the most pain - the mast base. A heck of a lot of force passes through here so it needs to be strong. I originally used an aluminium weldment to take advantage of cheap structural tubing, and couldn't get it to stop cracking. What follows is the successful version. As it evolved over a number of attempts it is a bit overcomplicated.



There is a short (~30cm) length of very strong stainless pipe permanently attached to the frame. It is set back around 7 degrees. Sitting inside that is another short length of aluminium pipe that serves as a riser. In theory, longer or short lengths should be used to raise or lower the sail. In practice it got jammed so well it isn't going anywhere. Sometimes a super-close fit isn't the best approach!



Sitting inside that aluminium riser pipe is the mast base itself. It should be made from one piece of solid aluminium with a flange to stop it falling into the riser pipe (not shown as mine has the flange on a 2nd piece due to the evolving design). It is tapped M12 on the bottom and retained by an M12 bolt. The length of the fat section could be reduced a lot.

Sitting on top of the fat section is another delrin bush. A 1.5M+ length of aluminium tube will slide over the smaller diameter section and is used to reinforce the mast. Finally, the mast is slid over the tube and will sit on the delrin bush.



The stainless pipe is attached to the main frame by 2x 3mm stainless plates - one on the top of the frame, another on the bottom.





These have held up to a fair amount of abuse so far without any signs of deformation.

The smaller hole is used to hold an eye-bolt. This will serve as an attachment point for the downhaul.

Just realized I forgot to add the rigging part (does this forum /still/ have no "preview" option?). This is where it got expensive for me,



Downhaul is easy. You are looking for a "Triple Block" (bottom) paired with a "Triple Block with Becket (where to tie a rope end) and Cam Cleat (where to easily lock and release the rope)". I wouldn't bother will ball bearings in the blocks. They just seem to get gummed up with sand.

This arrangement gives a 6:1 advantage and makes it trivial to put enough tension on the sail. The rope should be connected as per www.harken.com/article.aspx?id=42513

The Outhaul is also pretty easy.



Here we have a "Fiddle Block" and a "Fiddle Block with Becket and Cleat". The cleat itself is not visible (blocked by the boom pipe). I removed some of the linkages after this photo was taken so the blocks could be moved closer towards each other, putting more tension on the outhaul. This time around we have a 4:1 mechanical advantage.




And finally, the mainsheet. The 10mm rope begins at the end of the boom, loops through a "stand-up" pulley behind the seat, then passes through a Ratchet pulley (Harken 57mm swivel). The rope end is tied to the Downhaul eye-bolt to stop it going missing. This arrangement is easy to control in fairly strong winds.

I started off using rope from bunnings and it was complete rubbish. After being dragged in sand it developed huge bulges which were impossible to pass through the pulleys. After that, I threw it and bought some "10mm double braid rope" from Boating & RV and it has worked magically.

Part numbers:

Ronstan RF41500 Series 40 Ap Block - Fiddle
Ronstan RF41530 Series 40 Ap Block - Fiddle - Becket - Cleat
Ronstan RF20302 Series 20 Triple Block
Ronstan RF20332 Series 20 Triple Block - Becket - Cleat
Harken p/n 2135 Ratchet Carbo 57 mm Ratchet Block - Swivel
Ronstan RF41140 Series 40 Ap Block - Single Stand Up