The whole point of building your own land yacht Gizmo is to do it on the cheap by using what is readily on hand. It's a fantastic project recycling what's easily available or can be altered to suit. I'm certain you would agree with me there.
The little machines that "prairiepilot" has built are absolute corkers.
It's fantastic to see the designs and how much fun he has had constructing them. I love the improvisation and photos of his process. A TOP effort.
Gismo, I really respect your input to the forum and love your engineering background to solving problems, but at the end of the day we are not talking "old fashioned" land yacht or water yacht sails here, they are so old school. Granted these traditionally designed sails work fantastically well, are required for landyacht racing, but unfortunately also cost a fortune when building a starter fun yacht.
I thought we covered uncut windsurfing rigs a while back quite well, but you refuse to take on board the windsurfer sail design trends.
I'm the first to admit, I too was struggling to understand how it was possible, but I'm a very curious and determined bugger when I put my mind to it and not too proud to take on and try others ideas. I have persevered and reaped the rewards of these $30 setups.
So rather than ridiculing us from an "engineering view point" for having a go. How bout you start to do a little research about them before making your flippant remarks about something you don't understand and have never been exposed to.
We are just using windsurfing rigs that are cheap, very readily available and go like hell when rigged correctly. The fact that they don't need out haul is neither here or there, it's a cheap form of propulsion and just works perfectly.
I would really love for you to have a go in my yacht and you could see first hand the potential of being able to set a rig using only downhaul for the different wind conditions or direction of travel.
I'm only a common farmer (and a burnt out one at that) but the bottom line is it all comes back to a sail that is designed to match the mast and it's dynamic changes.
I think the draft of a sail can be altered without the use of an outhaul
I have a 8.4 M 3/4 rig yacht and the draft is altered by tensioning or letting off the backstay which goes to the mast head. This bends the mast which alters the draft and flattens the sail
I imagine the same thing could be done with an unstayed mast by bending the mast with tensioning the downhaul
and it seems to me that that is why windsurfers go to so much trouble matching the sail to the mast and vice versa
I stand corrected if I am wrong as I dont profess to be an expert
I should add that I never alter the outhaul on my water yacht. The friction on all the boom slides makes it an ineffective way of altering sail shape A tweak on the backstay to bend the mast is very easy to do and works well
Select to expand quoteGizmo said..
^^^^ "A MODERN windsurfer sail and mast does NOT need outhaul to shape/set the sail."
?????? Really. I would love to see some proof of that.
I rest my case!!!
Seems my post has stirred up the pot a little! Well, since it's 50 degrees F up here in the middle of winter I decided to try and rig a new 6.0 sail I picked up recently. It has (cambers?) on the bottom 3 battens and seems to set well with just the downhaul. The sail is smooth with a nice belly but without trying it out I'm just flying blind. I also played around with the type of boom to add. I have front half of the windsurfer boom vs. making a curved boom to go under the sail and hit me in the head. Thoughts? Thanks
Forgot to mention this; I've read on here the most of your sails rotate around the mast but with my moving the sail back and forth the mast rotates with the sail. Maybe the results are different with pressure of the wind? Maybe because the mast is flexed so much the sail can't rotate around the mast? Does it even matter?
PP I think you have a good setup there. As you have found out you don't need much outhaul
As your sail has bent the mast back the sail is not going to slip around the mast but rather the mast and sail will turn together in the mast step which is fine and how they work on a windsurfer
I personally would make a boom like you have drawn with the yellow marking attach the clew of the sail to the end and fix your main sheet to the boom where you have shown the bend and run it down to the seat behind your head with the tail running along the boom to a pulley block on the mast step and back to your hand. The pulley block in the front could actually be attached to the downhaul strap which is the setup I have
and works fine Better actually as the sheet does not have to go around the downhaul
cheers Hiko
Hmmm, 70 odd rigged sails in the picture and not a boom in sight. 
Love your work prairiepilot !!!
I agree with Test pilot 1, just try it as it is with the windsurfer wishbone boom.
A straight boom made out of an old snapped mast works really well too. Just attach the rear outhaul eyelet down to the straight boom (extend Hiko's thick yellow line) with a short line and refit the bottom batten. It doesn't matter much if the bottom batten doesn't change sides just to test it.
This sail looks like a real ripper. Just over downhauled in the pic. (see the wrinkles back up the first 2 panels from the bottom. Admittedly the batten is missing.) But still too tight.
Your downhaul ratchet strap system is pretty powerful and you have already ripped one old sail from too much tension. (the older ones didn't take that much to downhaul as they were not made from all monofilm.)
Try and keep the sail/top battens with slightly less downhaul tension, so when the yachts mast/sail is horizontal to the ground you can twist off the tip of the sail when you push down on it gently.
In your photo below you have it pretty right. The sail can then weather cock when hit by a gust when there isn't much sheet rope pressure. Sheet in and these panels will tighten up perfectly.
Yes, as Hiko said the sail, boom and mast rotate all as one.
don't contribute much to forums,but with regards to outhaul on windsurfer rigs here's my contribution. firstly been a windsurfer for 40odd years (also have blokart which I use in the winter),and until recently was an RYA windsurfing instructor, Sails back in the mid seventies required lots of outhaul. But modern rigs require lots of downhaul and little outhaul but it depends on which type of sail,for freeride the downhaul is set depending on the wind strength more for high wind less for lighter... Its basically used to the set draught of the sail,the outhaul is simply pinched up to hold the sail to the boom end. BUT with racing sails most dedicated sailor set the downhaul then rig the end of the boom with a system of ropes and pullys, most racing booms have a small pulley system built into the end of the boom to facilitate this ,the idea being that after setting the downhaul, the adjustable outhaul gives the sailor the ability to alter the sail on the fly. IE more outhaul flattens the draught,and the sail performs better upwind,once round the upwind mark,loosen off the outhaul to give more power on a beam or offwind reach. Even freeride sail become unmanageable,if the outhaul slips when out sailing,so yes they don't need high outhaul but it does add to control.The standard practice being to downhaul to sail to suit the wind then,assuming non racing,outhaul and test the sail by pushing it in the centre so that the sail just fails to touch the side arms of the boom. However I don't think its particularly relevant to land yachts,because I have rigged the blokart so I can use my numerous windsurf rigs with a standard windsurf boom(4m to 9 m ) and don't seem to notice a great deal of difference from standard blowkart sails. Just my humble input.
