Pushmi-Pullyu; a Proa for All Oceans?
It surprises me that (apparently) few of us have ever sailed our proas on their “darkside” tacks, simply out of curiosity. How does YOUR proa perform with its ama to leeward? Can it even be done? (An asym vaka, for instance, might need to be assembled “inside out” to get the flat side where it belongs). Rigging will be an issue—consider purchasing 100’ of ¼” polypro for a few bucks and start from scratch—temporarily. At the very least, consider it from your armchair; what if? Where would your boat be stronger, where weaker? There’s no compromise recommended, no “jack of all trades.” We’re simply taking your existing boat and sailing it on the other tack—what changes? Please, don’t focus on what wouldn’t work; yes we know that staying is an issue when sailing “backwinded”. Yes we know your rudders are now on the wrong side, etc. It’s not necessary to solve the location and function of every bolt and screw on the boat, rather let’s paint with large strokes; what changes?
Dave
I’ve sailed on the “darkside” tack several times on P52, both intentionally and accidentally. Fortunately all the accidents happened in fairly benign conditions, winds less than 15 mph, and catching a wind shift while pinching up (or plain inattention). With a fairly large crabclaw rig it could have been a problem in higher winds pinning the rig against the mast, though brailing lines make that something of a non issue. A couple of sweeps with an oar and you are back in proper proa form.
Intentional tacks (and more ‘accidents’) were all with quarter rudders and balanced club staysail in later iteration of craft. Absolutely no problem as long as wind is fairly low, higher winds would probably in P52’s case get to the point that the added drag of the depressed float would add enough lee helm to overpower the ability to get back on the ‘good’ tack. Short tacking in some situations particularly in tight conditions, like making a docking slip in a small marina, is a go to tool. I think the biggest issue is with rig, some should work quite well, others not at all. With the staysail rig, P52 had a touch of lee helm on the dark side and everything felt a little different hanging out on the wrong side of the boat, tiller extension was handy in that case.
Skip
now that you have “proven” (by calculation only, but still, it definitely look sound to me) that an Atlantic Proa or a Pacific Proa (with ballast) could be as good as one of the best racing trimaran out there, why not choose only ONE configuration, and optimize it even further?
A very good question, often asked.
The reason is, is that it’s what we do every day. We run down the same logic paths, come to the same conclusions, defend the same variables and trash the same partial solutions. Placing artificial constraints on a design forces us to take a fresh look at the problem, reconsider our pre-conceived positions, learn our subject both broader and deeper.
I’ve actually come to a completely different conclusion after this weekend’s MOD70 exercise; one which is novel to me, and hasn’t been discussed here before I don’t believe. It is not intuitive. I’m not prepared to describe or defend it just yet, but it’s the constraint in design which lead to it.
Dave
I know I’m probably starting to sound like a broken record here, but anyone got a take on the issue of pitch stability? And what could you potentially do about it?
As far as I can tell, shifting the CG of a proa aft of the midplane by any significant margin is not feasible without adding a lot of water ballast aft, which a comparable tri wouldn’t need. On a smaller proa, at beach-cruising sizes, where crew weight makes up a very large fraction of the total displacement, and it’s possible to go very far aft due to the completely open nature of the boats and the fact you’re generally operating in good weather you can get the CG aft a good deal. As soon as you get to the larger sizes, even something as comparatively small as ‘Firstborne’ doesn’t really benefit much from moving crew weight aft in the cabin anymore though, since their range of motion is quite limited. On Firstborne you could bring up about 2500Nm by moving the crew-CG aft by about a meter, and a 5° bow down trim would give you about 6000Nm, though I’d rather save those 6000Nm as reserve for when you plow into a wave. Overall that’s still a long way away from the ~14000Nm which Firstborne could bring up when close-hauled as an atlantic proa, meaning a banana board would still have to provide the majority of the pitching moment, which imo is not a reasonable solution.
I’m starting to think that something as absurb/impractical as a surface-piercing V-hydrofoil located right under the bow is just about the only thing which could make the numbers work out where pitch stability is concerned… Or we have to go to a rig with a much lower CE when reaching (like a crab claw rig), so that we don’t need as much pitch stability…
Marco
There is a perception that ballestron rigs must be unstayed. I think this comes from the simple arrangement used on model yachts such as the Mareblehead class, which is the most widely known use of ballestron rigs
A ballestron rig can be rigidly stayed. If the rig does not need to be rotated 360 degrees, it can be stayed the same way as any conventional rig with a rotating mast. It just needs an outer forestay to take the place of the convenional jib stay.
If 360 degree rotation is required (as for the pushmi-pullyu), the stays need to be attached to a rotating base in some way. There may be a small weight penalty for such an arrangement. We used this type of system for the Mi6 proa.
Mal.
If 360 degree rotation is required (as for the pushmi-pullyu), the stays need to be attached to a rotating base in some way. There may be a small weight penalty for such an arrangement. We used this type of system for the Mi6 proa.
Mal.
Good points. Is it possible to perhaps extend the mast higher, so the stays may be fixed yet clear the head of the sail?
Dave
If 360 degree rotation is required (as for the pushmi-pullyu), the stays need to be attached to a rotating base in some way. There may be a small weight penalty for such an arrangement. We used this type of system for the Mi6 proa.
Mal.Good points. Is it possible to perhaps extend the mast higher, so the stays may be fixed yet clear the head of the sail?
You could have a mast head balestron rig, but that limits you to pinhead triangular sails and means or 2 sets of running backstay type shrouds.
With Marco’s suggestion….If you have a conventional sloop rig, then the luff stays need to be in line with the mast for it to work equally on both tacks. If you move the mast sufficiently off centre to get adequate lee shroud angle, the luffstays have to go with it. Finding luffstay tack points could be interesting…..
If you use a square headed or heavily roached mainsail, then all the stays and shrouds have to be running backstay type to get the mainsail through 360 degrees.
You could use a rotating base as Mal has suggested, but I am not sure how practical that would be large scale. Wasn’t there a proa design with a rotating base or circular track???..Disco Volante??
http://www.tennantdesign.co.nz/index.php?page=disco-volante
Any way you look at it, lots of complication, weight, drag and things to go wrong.
Rob
Any way you look at it, lots of complication, weight, drag and things to go wrong. Rob
Yup. So let’s stay with a dead simple unstayed carbon fiber tube, in a rotating bearing. Luff sleeve in the mains’l and a wishbone boom. Giant sailboard rig. 😊
Don’t laugh! this is working at 1500 sf for Tom Wiley and his PHRF rating is on the floor. He sees no reason not to double that.
Dave
Dave,
They are nice rigs….......One question….
For it to work in a proa where the mast is in the centre, the mast would have to be very tall to get equivalent sail area??? with all the problems that go with it .....Or you could go schooner, but that isn’t a good starting point for an all round efficient rig????
I am also cynical about all handicap systems…..the rig is good, but it doesn’t mean it is superior, it is just perhaps that the handicap rule looks upon it over-favorably (for lots of good reasons).
Rob
You could use a rotating base as Mal has suggested, but I am not sure how practical that would be large scale. Wasn’t there a proa design with a rotating base or circular track???..Disco Volante??
http://www.tennantdesign.co.nz/index.php?page=disco-volante
Any way you look at it, lots of complication, weight, drag and things to go wrong.
I say rotating base, but it doesn’t need to be anything more than you would normally have for an unstayed rotating mast, i.e. a bearing at deck level and at the mast heel. What adding stays allows you to do is to reduce the size and weight of the mast higher up. What we did on the Mi6 was to taper the stub mast above the top bearing from 125mm down to about 70mm over a height of about 1 metre. Above that point the mast was a standard 60mm diameter mast section. At the top of the stub mast is a set of spreaders. The lower shrouds run from the stub mast just above the top bearing to the ends of the spreaders. At the ends of the spreaders are the chain plates for the rigging above stub mast, which is just designed as for a standard stayed rig.
On the Mi6 we used a wishbone boom arrangement which was attached to the spreaders, but you could just as easily have a ballestron boom attached to the stub mast just above the top bearing. For some reason ballestron boom are often designed as massive things, but they don’t need to be any larger in section than a standard boom.
The only additional weight of a this type of stayed ballestron rig over a standard stayed rig is with the upsizing of the stub mast to handle the bending stress. It can be argued that there may be weight savings in other parts of the hull structure which may partially offset this.
Mal.
Good point about the tackpoint for the jib when in atlantic mode. There isn’t really anything suitable around, which would probably mean something like the ‘bowsprits’ you see on some catamarans. That’s a not-so-nice addition to have to make…
Testing by Marchaj showed that Pinhead triangular sails are awful because near the top the entire sail is enveloped in the turbulence from the mast, and you could just as cut off a pretty big section of the sail without any effect on performance. Square-topped mainsails, or mainsails where the masthead is strongly curved backwards like on some dinghy classes are much better aerodynamically; the latter can yield a decrease in drag from the tip vortex as well (for close-hauled courses the masthead bend to improve the planform can increase the driving force from the rig by as much as 20%).
Marco
Testing by Marchaj showed that Pinhead triangular sails are awful because near the top the entire sail is enveloped in the turbulence from the mast, and you could just as cut off a pretty big section of the sail without any effect on performance.
Square headed is the way to go, but the mast has to be as tall as the pinhead situation if you want to avoid running back stay type shrouds and stays (and you do, especially multiple ones). That is a lot of empty mast to carry around in the worst possible place. That was the point I was hinting at.
Pushmi Pullyu realistically only works with with some form of cantilever rig, then you can have a square headed mainsail simplicity and ease of tacking and shunting. But it will be (slightly) heavier and less efficient than a leading edge sloop rig. Cruising wise,it definitely would be the way to go but then that is not MOD70 style??
Rob
I agree with you fully that unnecessary mast height is a really bad idea.
Dave,
For it to work in a proa where the mast is in the centre, the mast would have to be very tall to get equivalent sail area??? with all the problems that go with it .....Or you could go schooner, but that isn’t a good starting point for an all round efficient rig????
Don’t honestly know, without some trialing. Can say that Derek M. Baylis (65’ cat-ketch by Wiley) has a 1500 sf main sail, as does the 48’ Ahava, a catboat pure. Pushmi-Pullyu, to Mod70 specs, wants what did I say, 2600 sf? That’s only 75% larger than the Baylis’ mains’l. Will it be as hot to windward as the (much bigger) MOD70 rig? probably not, but… it’d be pretty darn simple, now wouldn’t it?
I am also cynical about all handicap systems…..the rig is good, but it doesn’t mean it is superior, it is just perhaps that the handicap rule looks upon it over-favorably (for lots of good reasons).
I have sailed both with and against several Wylie cats, Including the Baylis, also Ahava and also several 30’ers. These boats are spooky fast—not magically and mostly due to their decidedly non-catboat hulls (plus they’re pretty lightweight—something the unstayed mast haters don’t like to hear!) I once crewed aboard a Farr 40 in a 5 hr windward/leeward point to point night race in SF Bay. The wind was admittedly flukey but it was never a reach of any kind—all courses were either above or below the layline. We were fully crewed (9 I believe) and were racing hard against a sistership who finished within 5 minutes of us. We had sail changes 3-4 times/hour, sat outside the rail for every second upwind and had not one but two sailmakers aboard to optimize the rig at all times.
About 45 mins before we finished—surely and easily in first place??—we heard the finish gun go off. We *knew* the sistership wasn’t that far away and we were right—it was Ahava. She had 8’ on us, sure, but we had crack crew, carbon hull and rig, 13 sails and professional help start to finish. The race was not fast so wave-making drag was not a deciding factor. Ahava had her owners—60 and 62 years of age, sitting in lawn chairs on deck throughout the race and no other crew. She had exactly one sail—her main. No spin, no reefing (shorthanded, and crew too old to boot). no hiking out against the lifelines. Ratings? On corrected time she beat us by more than 2 hours—in a 5 hr race.
Both Farr 40 crews were unanimous, that Ahava must have caught an incredible 2-hr lift, somewhere while out of our sight. Yeah, sure.
Dave Culp
Pushmi Pullyu realistically only works with with some form of cantilever rig, then you can have a square headed mainsail simplicity and ease of tacking and shunting. But it will be (slightly) heavier and less efficient than a leading edge sloop rig. Cruising wise,it definitely would be the way to go but then that is not MOD70 style??
Rob
You lost me here. If you put a cantilevered (stayed) rig on PushmiPullyu and a square-headed mains’l, wouldn’t you *have* a Mod70 rig sloop rig? (albeit smaller and much less expensive being only 3/4 as large on a mast massing 2/3 as much). How would it be “heavier and less efficient?”
Further, Rob, you say that Pushmi-Pullyu “realistically only works…” with the rig you describe. I presume you mean when compared to the fastest MOD70 on the planet and not that Pushmi-Pullyu in concept “realistically only works,” etc? Surely there are one or two use cases where such a mast isn’t absolutely required for adequate performance? 😉
Regarding running backstays; yes these are a pain in the butt, but they’re extremely common, right up to the present time (AC90’s have ‘em, for instance) The only reason the big tris avoid them is due to the extremely wide staying base they have—and even so, relying on very massive diamonds for stiffness (this rig is unsupported between deck and hounds, an uncomfortably large distance on a big boat), they are scarily subject to inversion and shattering. Again, personal anecdote, but I happened to be aboard both a Farrier 27 and a Newick 50 trimarans with identical rigs (3 stays plus massive diamonds on the rotating spar). Both masts, for identical reasons, inverted and shattered (and only a week apart!). The Farrier got off lucky and only destroyed a $60k mast; the Newick (Alacrity) took out $280k worth of carbon and very nearly killed me when the boom dropped on my head and put my face into one of her genoa winches.
In both cases if we’d had runners, the masts couldn’t have gone out of column. So, for “simplicity’s” sake, we had the, it turned out, far more dangerous rigs. They don’t do ‘em quite like that anymore. 😉
Dave
Dave,
I really do like cat boat and balestron rigs, they are simple and therefore easier to control and fine tune. And maybe because of this they can sometimes be more effective than complicated twitchy rigs. Especially at night when most sailors lose concentration and are a little disorientated with too many things to think about.
I have done enough offshore racing to know that it can often be (seemingly) manifestly unfair or unjust. Night time snakes and ladders. The fact that a 48 ft cat rigged boat finishes 45 minutes behind a 40 ft stayed sloop rigged boat in a 5 hour race tells me something. The fact that it finished on handicap 2 hrs ahead of the sloop rigged boat with a hot crew in a 5 hour race (Call that offshore??) says a lot about the handicap system. I have had lots of similar experiences, albeit not with cat rigged boats.
If cat and balestron rigged boats are so close to or better in performance than stayed sloop rigged boats, then most (all) of the serious yacht racing world has got it seriously wrong. Maybe they have all these complicated rigs just to keep the crew occupied???
As for running backstay rigs, eventually they are a disaster waiting to happen, especially short handed which by default a proa will generally be. If it was only one set, OK, but we were talking 2-4 sets for Pushmi , and even then I don’t think they would work. Think how far and where the boom drags the leeward runner(s) around.
Rob