Here's a close up of the axle set up which is different from Clem's design

The next job is to make a seat.My 90 kgs bent the ply to a worrying extent so my design will spread the load of my bod over the length of the seat.

Most land yachts are loose footed on the sail like that
I guess the simple answer is that a sleeved sail is not necessary and it is easier to adjust the sail shape if the sail is loose footed

tryhard said..
The next job is to make a seat.My 90 kgs bent the ply to a worrying extent so my design will spread the load of my bod over the length of the seat.

A couple of stringers glued on the topside edges should stiffen it do you think?
Something solid for the seatback to attach to as well

As I indicated in an earlier post, I intend recycling the windsurfer boom.My plan is to fix the 2 arms of the boom along either side of the seat ( which by the way is designed for a skinny molinky - it is a bit of a tight fit for me but not overly so.When I got married I was Clem's present weight but someone keeps putting things in my food).I am now experimenting with the material to make the nappy seat out of.I tried plastic bags knotted together to make a temporary "sling" and this allowed me to lid down almost flat which I gather is the preferred driving posture.
Another question: should I have a metal plate under the ply where the main sheet saddle is fixed? All the pictures of 3 or 4 blocks to manage the main sheet suggests some very significant forces (upward) will be at work

Thanks Hiko.Here's a pic of my current experiment. My welder/engineer mate thinks I need a bit across the back between the 2 arms to prevent the arms from pulling inward when I lie on it. I've been a bit jittery about this idea because of the extra risk of injury in a prang.

Click on Hiko on the left and you will find photos of it

Lots of unknowns there like how many sheaves you are going to use How high do you like your boom etc etc
Everyone has their preferences When you rig your yacht you will have a better idea maybe use some cheap stuff
initially Generally you dont need your boom to swing out more than 45 degrees I dont anyway

I wonder if I have hit a major problem.My engineer mate has constructed the steering rod set up but used universal joints instead of the plastic joint which Clem used.the problem is the alarming slop over which the front wheel does even at rest.I hope the photos show the extent of the problem.I can see that keeping the unit going in a straight line would be a major mission.Am IO missing something here?

I just measured the distance between the front of the skirt and the mast step is 300mm

It looks to me as though you are sitting too far forward your butt needs to be just in front of the rear wheels
you only want a few kgs on the front wheel with you aboard The mast and sail will add a few kgs more
put some kitchen or bathroom scales under the front wheel and tell us what you get
If your feet after doing that are still way forward then your pedals will have to be moved forward along
with your plywood bits You can see why someone said don't worry about the sandblasting and painting
just yet! Fun hobby this

Like has been said, check the weight on your front wheel first and work from there

Rightio chaps.I think I start to get the picture.This land yachting business is a dark art to be sure.Will the weight distribution solution take care of the steering issue I foresee?My engineer mate says the front wheel will overpower my pedals rather than the other way around.

Somewhere way back in this thread I think I remember the geometry of the steering was discussed
If you take an imaginary line and project it down to the ground it should land directly under the centre of the wheel axle
If this is so then all should be good. You have a well proven steering layout known as layover steering in common use on landyachts
The linkage however I am not familiar with , someone else may want to comment on that ?

You get rid of that weight on the front by moving your bod back If you finish up with somewhere under 10
ready to sail you should be good IMO As you say it is a dark art You won't have to move back much
You are starting to look about right in the picture

Yes these are tricky little beasts. Don't panic, we will sort this out for you. First of all you need to estimate the total weight of you and your yacht fully rigged. If you are 90kg I estimate the yacht will be about 30kg, so lets say we have a total weight if 120kg. I would recommend you aim for having 10 to 15% of that at the front wheel when you are seated in the yacht, i.e 12 to 18kg.
Take the plywood seat off for now as it weighs next to nothing. Plug the mast in. Get a plank of wood (150 x 25)1.5m long and place it across the skis so it is touching the front edge of the rear tires and sit on the plank. This will tell you where the steering peddle needs to be. I like to sail with knees raised slightly. I find it a more natural sitting position. Get something to rest your heels on at the same height as the plywood deck would be at. I notice you have holes drilled in that horizontal tube welded to the back of the mast post. Use those to position the foot peddle where you find it comfortable. That may be all you need to support the foot peddle. Could just cut off the vertical one so you can slide the seat further forward.
When you make the sling seat have a look at some of those low fold up beach chairs for ideas.