Laterally assymetric monoproa. Pictures and video - sailing.
Today the hulls look like this.
I will testsail them tomorrow. Its raining today and there is almost no wind.
Johannes.
Deep Purple! 😊
Looking good.
Better with Deep Purple than Led Proa!
Thanks!
I will start rigging the monoproa tonight. It will be the same luggsail i have used on my previous models.
Johannes.
Deep Purple! 😊
Looking good.
For a bunch of sailing “Machine heads”?
Okay….even I’m groaning at that one 😕
I have tried this monoproa today.
It was quite strong wind, somewhere around 7 - 9 meters/second, and some breaking waves. Hardly perfect conditions to test a new strange kind of sailboat. I should not have done this, as it sailed well enough that i want to build a real monoproa….
Youtube-video of my first testsail. I hope to get better conditions tomorrow. I think this kind of boat has some serious potential. It was really fast!!!
Johannes.
One more picture.
Johannes.
I walked around the monoproa to show it from diffenrent angles.
Johannes.
I should not have done this, as it sailed well enough that i want to build a real monoproa….
If you want to get off this idea, I suggest an additional test that might cool your ardour: put in a radio control and make it shunt.
I first came across the idea of a monohull proa in an exchange of letters published in AYRS publication #94, Shallow Draft Craft. They settled on the name moa. The proposal was a narrow hull with a permanently canted lifting keel and Newick-style rudders. Righting moment could be adjusted both by lowering the keel, which would bring the ballast bulb further to windward, and dumping water ballast carried in a narrow full-length lee pod.
I have run aground a boat at enough speed that the Newick-style rudders would have been a problem, and Mbuli damaged both rudders running aground during her first outing at an Everglades Challenge. If the rudder is ever the deepest part of the boat, I want it to kick up.
Side-hung rudders on a moa have a problem with changing immersion a lot when the boat heels. Not much of a problem on a two-hulled proa, but here it would be.
I have an idea for rudders that could be in line with the bows, projecting beyond the ends of the boat. Make a frame that is a distorted tetrahedron. Attach two corners to the gunwales on either side of the hull. Attach a rudder to the other two corners. Make sure the rudder axis slopes so that it is further in at the top, further out at the bottom, by 5 to 10 degrees. Seen from the side, the two rudder axes form a very steep upside-down V. Give the rudder a T-foil that is horizontal when the rudder is at operating depth (possibly put a little float at the top of the rudder to make sure it doesn’t go lower). Then if you reverse direction, the T-foil gets a positive angle of attack that is twice the slant angle of the rudder axis. If the rudder axis is inclined 5 degrees towards the centre of the boat, the T-foil gets a 10 degree angle of attack. The forward rudder would lift out. If you control the elevation of the rudders with a line that connects them, the new aft rudder drops. As the T-foil bites, the aft rudder is pulled further down until its T-foil is horizontal. The forward rudder gets pulled up. How much depends on how deeply immersed the rudders are when they are at the same depth. You may have to pull the forward rudder up a bit more.
I have a notion that a T-foil large enough to do the job would impose quite some forces in a sea rough enough that the forward foil gets hit by waves. You need a structure that keeps it from being flipped all the way back into the rig or into the deck. The tetrahedral frame would also get in the way of anchoring. That’s why I am not too impressed by this idea.
If you have a well enough balanced rig, you might get away with what Peter Lynn did on a kite sailing boat: it had four rudders, one pair each in the bow and stern. The forward and aft pair counterrotated. Draft was quite shallow, and the rudders were made more effective by end plates. Such rudders might end up quite a bit shallower than the keel. The forward rudders would still be vulnerable to a rock that is deep enough not to hit the bow, but steep enough to hit the rudders before the keel. Rudder shafts would have to be dimensioned for collision loads, which would be a lot higher than any force that comes from water flow.
The first of the proarigs I described in another thread might give you the helm balance you’d need for Lynn-style rudders, but you’d be stuck with having to raise and lower jibs even when shunting in tight spaces. Not desirable. Another possibility would be a schooner with a pair of junk sails that have permanently curved battens. That would give you the power of the Bolger rig without the control problems and with the convenient reefing of the junk. Use only the foresail on long tacks. Leave the aft sail up when you have to reverse quickly, but let it idle. You might not even bother with double sheets, but have just one sheet for each sail.
Put a fixed keel on the windward side, and (on a small boat) use movable ballast like Sven Yrvind did in his last boat. Store it on the lee side in light wind, so that the boat is level, move it to weather when required. Actually, unless you can shift ballast, I see really no point in a monohull proa. I don’t see any advantage that would be worth the bother with the rudders and rig.
With few moving parts, no beams, and sails you can make yourself, a moa with asymmetric junk sails should be a fairly cheap boat. If I can’t get space for a multihull, this might be a candidate for my next boat. But first, I would want a model that shows me that the rudders work, either version, but preferably the Lynn rudders, which seem simpler.
By the way, how thick is the plywood you use for your models, and if it is 2mm, where do you get it? In Trondheim, I can get 2mm plywood only in sheets 50cm x 30cm, and I haven’t found any Norwegian source for longer sheets. In Edinburgh, getting 100cm x 30cm was no problem, and I am still working with stuff I have left over from when I lived there. I try to think carefully before I use up what I can’t easily replace. And I haven’t seen at all a source of 0.8mm plywood, which I want to use for wing sails. I lost one sheet to a tortured ply hull. It turned out to be too thin for that a use. I only have one more left.
Regards
Robert Biegler
Thanks for your lengthy answer!
I use 3 mm Baltic birch plywood that i buy at Bauhaus.
It says 4 mm but its actually 3,2 mm when i measure it.
We have 1,0 mm 4 layer plywood, but its very expensive. (I work at Bauhaus in Gothenburg)
After these first tests i think there is a lot of merit for the monoproa or Moa as you call it.
Its much faster than my Matt Layden Paradox model. Its much more directionally stable, almost as directionally stable as my 10:1 advanced sharpie proa. When it starts surfing up on the beach there is no tendency to turn the waves a broadside. It just starts surfing almost straight up onto the beach.
Actually, unless you can shift ballast, I see really no point in a monohull proa. I don’t see any advantage that would be worth the bother with the rudders and rig.
I think that a skinnier waterline when heeling, a very directionally stable and shallow draft boat is very interesting.
I don’t worry much about the rudders as i would use cassette-rudders connected to the stems like the tied rudders on a Wharram cat. The cassettes would be tied to the stems instead of the rudders so i can lower and pull them out of the water when shunting. I think only the aft one should be in the water when sailing, especially when there is some rough seas.
I don’t think the Moa should be uneven loaded to get a higher righting moment. I think that the asymmetric shape creates a higher righting force without the need to shift ballast around. Any shifting of ballast/weight should be a “bonus” when sailing hard to maximize speed. If the weight-distribution is wrong it starts to behave really bad. Its much harder to steer.
I think that righting force thing is a bit counter-intuitive. Its easier to think of it like its a scow/barge kind of boat when it heels like it should. Its actually much easier to heel it over the wrong way than the way the wind does when sailing.
I tried to test it some more today, but there was to much wind. I will ad a chinerunner on the leeside soon.
Johannes.
I post an old picture from my Advanced Sharpie - Thread.
This is how i imagine the rudders.
After testing the Moa i dont think i need any added lateral resistans. The hull and a chinerunner is probably enough.
I will have to test some more.
Johannes.
After these first tests i think there is a lot of merit for the monoproa or Moa as you call it. Its much faster than my Matt Layden Paradox model.
I suppose you used the same sail? How do length and weight compare?
Come to think of it, is there any chance of sailing both models side by side? Perhaps even with radio controls? I just finished my experiments with hinged foils (report on the AYRS yahoo group), and my foiled model seemed to move along well enough when i sailed it on its own. I needed the comparison with a model that has the same hull and sail, but a keel instead of the foils to find out that the foils didn’t provide a noticeable advantage.
Regards
Robert Biegler
This moa thing is pretty cool. I couldn’t believe how it tracked with no dagger board!
There might be some overlap with the moa concept and the scow-like monos that have been killing it on the mini transat circuit.
They talk about how as the boat heels (since monos need to do that to go) the angle of the centerline of the waterplane is shallower (straighter?) for the scow than the typical beamy pointy hulled boat. Well, the moa might be an even straighter waterplane! Maybe that’s part of what you are seeing?
I found this through Sailing Anarchy on this INCREDIBLE blog ( I already shared the Hereshoff catamarans in another thread).
http://chevaliertaglang.blogspot.com/
lots to mull over there…
This moa thing is pretty cool. I couldn’t believe how it tracked with no dagger board!
There might be some overlap with the moa concept and the scow-like monos that have been killing it on the mini transat circuit.
Yes that is why i suddenly started this idea. Its more of a scow than what one can see at first. The sudden intererst in scows are to get maximum righting force from a given hull length, and a much straighter underwater-shape when the boat heels. Its exactly like the picture you show Loumanen.
Thanks for the picture and the link to the blog. Great stuff!!!
I suppose you used the same sail? How do length and weight compare?
The Monoproa is larger and more heavy then the Paradox, and they use the same sail. I cant compare them side by side at the moment. I only have one sail. I will see what i can do.
Johannes.
I have been testing my MonoProa some more today. The wind changed from good southwesterly via almost no wind to a very light northwesterly.
I’m very impressed by its course-stability. I have to adjust the rudder so it sails towards the beach. The water is to cold to swim and i don’t want to driver all around the lake and search for it.
