On the landyachts with rigging on the mast they always seem to attach the guys to a point near the wheels. It seems to me that this means when the mast heels this must hasten the lifting the windward wheel. Maybe I'm wrong.
I've been trying the wires attached to short horizontal extensions from the sides of the cockpit. This seems very effective. In the strongest gusts the cockpit twists rather than the rear wheel being pulled upward. Seems to work quite well.
Is there something I've not taken into account here? Maybe extra drag?

Is it possible to post a picture or a drawing on your thoughts?

I've seen yacht setup as you described, and you are right - they tend to be less likely to lift a wheel due to chassis twist (assuming you are comparing to a solid rear axle). Yachts with stay cables attached to the rear wheel locations tend to have flexible axles and this takes the place of the chassis twist. The less axle flex the more 'jumpy' the yacht and likely it is to lift a wheel, similarly if your un-stayed yacht didn't have a flexible chassis it would behave the same.

The trick is to have enough flex to soak up wind gusts, but not so much that you loose energy that might be used to push you forward. Axle flex is also good for sailing over rougher ground.

From my experiences I would argue that you need some flex in a yacht, and if you cant build a flexible rear axle plank then setting it up as you have offers an advantage (of course if you could use an un-stayed mast then you could do away with some extra weight and complexity )

Select to expand quote

gofaster said..
On the landyachts with rigging on the mast they always seem to attach the guys to a point near the wheels. It seems to me that this means when the mast heels this must hasten the lifting the windward wheel. Maybe I'm wrong.
I've been trying the wires attached to short horizontal extensions from the sides of the cockpit. This seems very effective. In the strongest gusts the cockpit twists rather than the rear wheel being pulled upward. Seems to work quite well.
Is there something I've not taken into account here? Maybe extra drag?

Im looking for pics to. one of the reasons for a wider stay triaangle is yacht stability. with a wing masted rig there are massive forces at play and the widest support triangle is neccessary.

pics please

Sketch attached.
The obvious thing to do would be to make the spring rate of the horizontal struts variable and alter them while sailing and therefore tune it to the conditions. Have yet to try this....

Ok got it, be mindful that it has to be less than the triangle formed by the wheels or you might 'trip' on it when you lift a wheel.
Also that attachment bar would need to be VERY strong as there would be considerable forces working on it.

If you wanted to experiment with the stiffness you could make your short beam very stiff, and introduce variable stiffncess in to the rigging using some stiff/ damped springs.

Or you could make the cross beam out of skis?

I'm sure ive read some comments on here that sprung rigs as i have sketched are pretty naff as they absorb the gusts by defelcting and do not transmit in the way you would want. i.e a happy compremise between accelerating and going base over apex.

Is your intention to make the axil very stiff?

I have actually tried the design you suggest. For the test the rear axle was rigid, and the mast was mounted so it could rotate sideways. It worked quite well in motion but made the rig and yacht spongy - resistant to accelerate. However the springs were not very stiff. I have a feeling that the springs (or my preference the crossbar) should be made quite stiff - or i wonder if they can be stiff to start for acceleration, then made less once in motion. Not that hard really, but more to think about while sailing. Like tuning a sailboat...

Are we trying to fit this within any class rules?

IRCSSA class 2 developmental - anything goes.

So are we talking Radio Control yachts or human pilot size?

if its radio control, think about this. we dont use any stays for rigs up 8.6m!!!!!! why use stays on a tiny RC machine . unstayed rigs have less drag

heres my little 0.85m set up. mast is a carbon tube batten from a windsurfer sail
its 2,2m tall . theres a 26" mountain bike next to it for scale. 1.3m long

Yes indeed - that's what I started with. Coming from windsurfing I thought it would be the go, but I found that I kept getting smashed down. No control. I tried many different masts but in the end thought the answer had to be with chassis/sail/ mast flex and I thought i could tweak things easier by having more "handles" by having a supported rig. I may be wrong.
My problem was finding the right stiffness of mast. Didn't try a carbon sail batten but did try carbon fishing rod sections. Interested in what you have done with your yacht in the picture. Does your sail have a curved luff pocket?
I hoped I might learn something from what the big yachts do. Interesting to go from big to small as commonly in engineering we go the other way.
I'd like to be working on human scale yachts but there just isn't a scene where I live. All we seem to have locally is the blokart, which I have no interest in.

the mast is a pulrtuded carbon hollow round batten sitting in a peice of fishing rod through the deck to the keel. the top of the mast is the flexible batten tip with alot shaved off. the cut and luff tensioning is actually a copy of a blokart sail.
the fractional rig jib is to provide self steering . the jib gets a gust and steers down wind which puts load on the mainsail and twweks it back to windward . you get a balance which makes it steer straight. , you need a canoe or kayak to chase on the big ponds

Thanks for that description. Over the last few days I have been trying lots more rigs. I have gone back to the unstayed rig and played around with it some more with various masts.
I think it might be the answer after all. Interested to see the rig lean over to leeward then power up and really take off and point very high.
Now i am going to work on the sail design. The sail I was using was too full at the top. (or the mast stiffness is wrong) I will take a good look at what the blokart sail looks like. Any other help in this regard would be great.
Interested in how you use the jib as a control vane - very innovative.
I am working on a ballast system where weight is moved from one side to the other on a change of tack. Works. Any reason this doesn't seem to be done on full size landyachts?

Made a scale copy of the 4m blokart sail, with bamboo battens, and using a fishing rod for the mast - goes great. Need to make a range of sails now.

Select to expand quote

gofaster said..
I am working on a ballast system where weight is moved from one side to the other on a change of tack. Works. Any reason this doesn't seem to be done on full size landyachts?

In most full-sized landsailers the driver is the biggest ballast. I don't think adding more weight would be helpful (unless you are very light).
That leaves the shifting your weight around the only movable ballast option.

In the boats with a wide cockpit (ex. converted 2-seat Nite iceboats) the sailor does tend to pull themselves over to the windward side of the cockpit.
I don't know if the Manta Twin folks do something similar when sailing single-handed (?).

Leaning out of the cockpit to windward is the best option for most of us.

I explored some 5.6mini designs trading off a narrow rear axle to get a longer wheelbase for better handling.
To get the righting moment back to something like a wider design I had to design a fuselage that allowed me to get my center of mass as far to windward of the leeward wheel as possible. I looked at a wide cockpit and a design where the entire fuselage pivoted to windward. Both had weight, drag, and complexity problems that I couldn't easily see a way around.

This is a photo showing the rig I have been trying. Can someone enlighten me as to what I should be doing at the foot of the sail? I left it attached to the end of the



boom as the sail shape looks better and there is more power, but I'm not too sure about the battern.

I would try just taking a loop around the boom from the clew of the sail and leave that lower batten to give you the outhaul necessary
The wrinkles showing radiating out from the clew seems to show there is too much outhaul there

Thanks. I now have tied the clew to the boom with a lot less tension than before, and also lessened the tension in the down haul, and the sail now looks a lot better, although there is now a gap between the foot and boom that doesn't look good - will fix. Need to try it. I cut the luff pocket curved but may need to try a another with more curvature.

The foot on sails like that are normally cut in a curve also Foot rounding they call it
On full size yachts sailmakers usually do a bit broadseaming there too which is making a couple of vertical seams that are flared toward the foot to make the edge tighter
and not have that wavy edge Mostly just cosmetic just to please the eye of the beholder A fluttering foot can be annoying though
That machine looks like a bit of fun

Lots of fun to use but has been just as engaging to design from scratch and letting it evolve. Some of my crashes have been spectacular - I'd be many times dead by now if it was full sized.
I added a a bit more sail to the foot and sewed a batten pocket along the foot of the sail just for interest - to make it look better and probably will give the sail a better shape there. Have to try it.

probably need to consider changing the sail design to incorporate some tension without relying on the sheeting alone. ie work on a vang and outhauland downhaul

Can you explain more please. I'll build an outhaul tensioner on to the boom now. I can tension the luff now -same as downhaul? The turnbuckle works as a vang but perhaps you have something else in mind?