Pi Hi by John Pizzey
This is John Pizzey’s new design and I’m posting it here in the forums because it’s so unique that it could spawn some good discussion. Enjoy. -Michael Schacht, AKA editor
An easily handled proa where the skipper and crew can sit relaxed under cover while making rapid comfortable carefree progress with frequent long periods of float-up sailing. To shunt, throw off the luff tensioner and the active sheet, let mast pivot back, winch in the new active luff, haul in the new sheet and you are away again, grab the rear tiller and steer your course, pin/lock/bridle the front tiller to its fixed position for best windward performance. You can do this excitedly or at your leisure, either way it won’t stuff-up. If things need to be sorted out for tidiness or safety, these can be attended to after you have set off on your new course, things like ensuring the furled rear sail is tight and locked etc. If you are using the drifter, which I suspect will be the most used sail it is even simpler.
(Peaceful evening sail photo 1)
When the crew (the person who happens to be in the front seat) and skipper (the person who happens to be in the rear seat) are feeling adventurous, a “lifting” spinnaker can be set from the front (the motor drive always determines the rear), for sailing with the float upwind or downwind. A large symmetrical drifter provides progress to windward when all the other boats are stalled and can be carried off the wind in stronger breezes, perhaps 20 knots or so for fast reaching or easy downwind sailing. It will be used to windward until sailing becomes uncomfortable for the skipper or the protesting crew. π↑ will also have large nets at each end for lounging, keeping ropes clear and for storage of a small tender etc. See photo of Zzipey’s crew.
(Photo 2 and 3)
The hydrofoils
Daggerboard type rudder supported at each end of main hull and a canted to windward asymmetrical lifting centreboard in float. Rudders steered independently by rocking tillers, the front one being locked at a positive angle of attack to provide lift to windward. Each rudder, not illustrated, is provided with a short actuating arm connected by a push/pull rod to the upper end of an inclined bellcrank having a lever arm much longer than the actuating arm so the arm can rotate while the bellcrank oscillates. The lower end of the bellcrank is connected via another push/pull rod to the lower end of the rocking tiller which can rock back and forth as the rudder performs 360° rotations. A direct linkage could be used if space permitted.
(Steering photo 7)
The hulls
The Main hull has three steps in each side, like an exaggerated clinker construction, to provide narrow hull progress through the water and waves and flared topsides which provide a centre of buoyancy when π↑ flattened, well out to leeward for self-righting. The float is virtually a replica of main hull to the first step. A long-shaft outboard motor is supported on a pivot mount on the central beam structure near skipper so it can be rotated about a fore and aft axis to and from the water and always disposed below the net with the remote controls near the skipper. There is full headroom in the central cabin. The high cabin, probably with vertical outside face or flared cabin side to match the hull has the beneficial effect of providing floatation well out from the CG when π↑ is flattened. A flared cabin side will enable the base of the inclined mast to be located as far as possible to leeward and that is a definite advantage.
The mast
The pivoting, preferably buoyant mast is supported centrally on outside of cabin top by a strut which extends from a mid position on the mast to the inside of the float. This provides an inclined pivot axis whereby as the mast pivots from its sailing position its upper end moves inward until the mast is vertical (athwartships) and then back out to the new sailing position. The mast has its minimum lean when locked centrally for non-sailing activities. The roller furling headsails are 3/4 or 7/8 rigged with the drifter and spinnaker set from the masthead. Halliards external and mast sealed, a carbon tube would be best although a round aluminium tube would be cheaper. The alternative, as per Flight is to support the prop on the cabin top, as per the attached drawing. This has the advantage of keeping the wing deck area and float free of rigging and keeps the loads in the main hull structure.
See photo 6
The sails and rigging
The tack of each working headsail incorporates a furler connected to the hull through a strop, preferably a length of chain for easy adjustability for fine tuning and probably tied with shock cord to limit shock loads as the mast pivots to the extreme of its travel. This strop enables the mast to pivot to its new forward position when the forward furler is winched down to a windward position along the fore-beam to provide the necessary sheeting angle. The sail trimming sheet passes from the sail to a turning block on the hull, probably at the end of the aft beam to a set of turning blocks along the aft-beam to a winch beside the skipper. The set of turning blocks is also used to lead drifter and spinnaker sheets to the winches. This sail furling lines pass to respective winches on the cabin top where they can be reached by standing centrally in the cockpit in the roof cutout which also provides easy access into and from the cabin. However the furling lines are interconnected to furl/unfurl together with sufficient slack when they are removed from the winches to enable both sails to be furled.
See photo 5
It’s also worth noting that this rig does not utilise a boom, great for ridding the fear of being struck a devastating blow, especially singlehanded and all the sails are set downwind of the cockpit which keeps them out of harm’s way. If you choose to use a spinnaker pole that is up to you but even this may not be necessary.
Sailing under spinnaker
With the masthead pivoted to its rearmost position, the kite should provide considerable lift to the bows and it will always be set from the front end as per a conventional boat which has a front and a rear, greatly simplifying the spinnaker controls and gybing.
See photo 4
Comment
Although proas are mostly symmetrical fore and aft, they do have a front end, best if it is the starboard end and a rear end, best if it is the motor drive end which becomes the port end so that if you motor out and set sail on the move you will start off on starboard tack. If you have difficulty with port and starboard on a proa, paint the starboard end green and the port end red, that should fix it for you and possibly help near competitors who will be wondering what the hell you are up to.
Sailing
The skipper sitting aft under cover has his hand on the rear rocking tiller. The front rocking tiller is pinned at a positive angle of attack to provide lift to windward and to the nose of the main hull which will be heeled about 15° when pressed. The rear “headsail” is furled.
With the drifter (isosceles triangle sail with line from each corner, front one pulled tight to windward and rear one becomes the sheet) the skipper can ghost along surprisingly quickly to windward or anywhere else when every other boat has their sails hanging uselessly, including the monohulls with their crew to leeward who can’t get their boat to heel to 15°. This sail can be held onto to windward until the crew protest too loudly, probably about 15 knots, when further windward progress will require dropping this sail about its medial hoist line, too easy, then unfurling the forward headsail and continuing, mostly on one hull and without concern of being caught out by a bullet.
Sailing downwind, take your pick, one headsail set; two headsails set wing ‘n wing; a headsail and the drifter; the drifter alone, or a spinnaker, it will all depend on the conditions, your course and your mood. You should be able to utilise barber haulers and poles to achieve what suits you.
All of the above options are not just dreams, I have tried them, they work and mostly beyond my expectations. The only exception is the new rudder control which I am enthused about but yet to be tried. It may even be possible to sort out a geometry which will enable the rudder to be raised without releasing its control rod.
That’s what I like about proa sailing, it’s fun and challenging and with the right design you are always likely to come home intact.
Happy sailing
John Pizzey
Nice pics, but I coudn’t understand the advantage of the pivoting mast with the flexible stays. IMHO a fixed mast will do the same without a lot of strops, lines an effort to handle. If once sail cut ist done for a good balancing, I will only furl out and in my sails. Further I disbelieve a good performance when wind abeam without boom. And last what kind of profile has the ‘symmetrical’ headsail for good effect? Or must the stay change the bows? The only advantage I could find is the lifting effect with spinnaker.
Could someone enlighten me, if I am completely wrong?
Hi, there are no simple answers to your queries, each design is unique and all the forces must be considered for the particular 3D layout, not just a side view. If you can get your arrangement to work for you that’s great.
Fortunately in proa designing practically anything can be made to work but to make it work so that you are keen to go sailing weekend after weekend for years, that’s another matter.
All I can add is that I have tried many arrangements, full size, not models, with a view to avoiding getting caught in irons without diligent attention to the setup of the boat immediately before you shunt as for me that is a pain in the posterior and the necessity to plan the manoeuvre will put most people off sailing proas for life. Compare that to a monohull where a tack can happen before you have time to think about it.
I had an extremely experienced crewman on PI for a Brisbane to Gladstone ocean race, he has probably sailed more ocean miles singlehanded in multis and monos than anyone else so he understands boats and now sails a homemade trimaran. After the race I offered him the use of Pi for his honeymoon which he accepted. He and his bride motored out from the harbour late one evening and anchored in the bay where we could see them from our house. Next morning we watched him try to get underway and he couldn’t. He motored to and fro, sails went up and down and eventually he gave up in disgust and abandoned ship back at the harbour. Why he couldn’t make it go I will never know, perhaps he was just too excited. (thinking about it, perhaps it was the steering wheel which had you facing across the boat, lots of people had difficulty with that)
It probably all depends on your temperament and how you want to use you boat.
Hi Michael and thanks for your efforts on behalf of those with an interest in proas. I thought I should attach drawings of my hull shape and of the steering arrangement as these may make my explanation more clear.
Best regards
John Pizzey
- the missing images, I am very much a novice at this and I am not good at reading instructions -
In my earlier response to Multihuller I did not answer all your queries. With the several articles I have written lately perhaps I assumed that readers would understand that Pi Hi is an enlarged updated version of my well tried Flight design shown in action in my earlier article and which has the mast laid off to leeward about 15 degrees from the leeward side so she is self-righting from a knockdown and sails more like a monohull than a multihull upwind with the speed of a multihull off the wind so I guess the description of my new design needs to be read with my articles showing the benefits of this arrangement.
That’s why I referred to considering a 3D layout in my first response as this arrangement places the centre of effort of the sail well to leeward of the boat when sailing upwind, again like a monohull. Flight was very narrow to keep within trailing width limits, 8 foot in fact, this version is wider, relatively speaking.
As for “lots of strops to be handled, lines an effort….”, if I am using my furled headsails I have one extra line each shunt compared to your arrangement, to tighten the luff, and for that I gain the ability to fine tune the balance to suit the cut of the sails I will have to work with,(by adjusting the strops link by link to achieve a desired setup).
Also I would rather winch in one extra line for the headsail, and have an adjustable luff tension to boot to suit conditions, than have to additionally pull one rudder up and another down to achieve my balance for the next tack. I don’t have any extra lines to handle the strops, they look after themselves.
If I am using the symmetrical headsail I handle only two lines, one for the front and one for the back and no furling/unfurling necessary so less lines when compared to the furling arrangement of my new design or your design and that is the sail I will be using most of the time upwind and downwind when I can pull the luff up to or toward the windward bow if I want to avoid using a boom for maximum effect.
The profile for that headsail will be left to the sail maker and if it works no better than the one I used on Piawatha or the one I used on Flight I will be happy enough but if they have improved their techniques and materials in the last 15 years, which I suspect they have, I may well be delighted with the result.
Your comment about disbelief of sailing with the wind abeam without a boom is a personal choice, use a pole if you must as I suggested or use the beam of you multihull. How do you plan to sail with the wind abeam in your proposal?
I hope this answers all your queries.
John Pizzey
Hi John,
Your views and experience are inspiring.
I am new to this forum. I built (and sailed) Blind Date, a 15m Harry proa. It has a rockerless lw hull and I found it sailes bowdown too much for my liking.
So I would tend to put my sail as far aft as possible.
Your positioning of sails has a very clear reason as we can see but don’t you get a bow down attitude?
regards, Rudolf
Hi, there are no simple answers to your queries, each design is unique and all the forces must be considered for the particular 3D layout, not just a side view. If you can get your arrangement to work for you that’s great.
Fortunately in proa designing practically anything can be made to work but to make it work so that you are keen to go sailing weekend after weekend for years, that’s another matter.
All I can add is that I have tried many arrangements, full size, not models, with a view to avoiding getting caught in irons without diligent attention to the setup of the boat immediately before you shunt as for me that is a pain in the posterior and the necessity to plan the manoeuvre will put most people off sailing proas for life. Compare that to a monohull where a tack can happen before you have time to think about it.
It probably all depends on your temperament and how you want to use you boat.
Hi John
I’m far away to criticize your experiences, and your work. But as you wrote about tacking monohulls, as easier to shunt as easier life aboard. I’m sailing my 8m proa with a crabclaw, and know what means to handle all the lines (and rudders) especially singlehanded when shunting. Hence a proa rig should be as simple as possible. Furling sails seems the best solution for a standard rig. My ideas you can see here: http://proafile.com/forums/viewthread/116/
Regards
Othmar Karschulin
In my earlier response to Multihuller I did not answer all your queries.
Hi John,
thank you very much for your fast, and detailed response. I think some replies run cross-over.
... and which has the mast laid off to leeward about 15 degrees from the leeward side so she is self-righting from a knockdown ...
This arrangement I like a lot, because it’s absolutely consistent with the proa philosophy. I wrote a comment to that at the report about your boats in proa-file magazine:
’ ... as an extension to the leeward canted rig I would install a telescoping mast. The upper part is hold by bungees which allow the rig to heel. It should be possible to arrange the forces, that the ama ‘skim’ the waves without flying to high. Some old sketches: http://www.multihull.de/proa/proakent.htm ...
The profile for that headsail will be left to the sail maker and if it works no better than the one I used on Piawatha or the one I used on Flight I will be happy enough but if they have improved their techniques and materials in the last 15 years, which I suspect they have, I may well be delighted with the result.
Will not happen the same problems with a symmetrical headsail like it was with the Bolger rig?
Your comment about disbelief of sailing with the wind abeam without a boom is a personal choice, use a pole if you must as I suggested or use the beam of you multihull. How do you plan to sail with the wind abeam in your proposal?
The beam of a multihull isn’t the same as the beam of a proa, except you use a very wide leepod, where you can sheet the headsail in an adequate angle. It’s hidden in my 2D proposal 😊
Regards
Othmar Karschulin
Hi Othmar, I checked out your boat and it looks great. I am impressed by anyone who will chase their dream and build their own design proa and not bow to the pressures of conformity, resale value etc.
I am pleased to see that I am not the only one using inclined masts. One of the difficulties I experienced with the inclined mast was having to explain all was OK to well intending boaties who stopped to offer assistance to my “crippled craft” and having to explain to them that all was OK it was intended that way.
You are obviously well advanced with the construction so I am a little reluctant to make any comments. However from a quick look only I wonder why you prefer the A-frame to a single central mast mounted on the cockpit surround where it would not interfere with the cockpit accommodation.
My reason for querying this is the relative stiffness difference between an A frame and the structure of a multihull. I often find it best to consider the extremes to arrive at a conclusion. An A-frame will always be very stiff, the fundamental triangle of all stiff frames. So consider a very stiff A-frame with a broad base mounted on a very flexible cross beam structure and see what happens when the structure twists. At some point all of load is going to be transferred to one leg of the A-frame especially as a deep main hull is relatively stiff in the plane of the stays which supports the fore and aft position of the top of the A-frame.
This will tend to occur to some extent in your craft dependant on the relative stiffness of these parts. It may or may not be a problem. A single side stay to the centre of the float may be worth considering.
From a very personal point of view I like the look of your proa but not the look of the mast, thankfully thoughh, beauty is in the eye of the beholder.
I can’t answer your query regarding the Bolger rig as I am unaware of it. This sail has worked well enough for me to want to use it again for a third time, hopefully updated and better than before.
I wish you all the best for your project.
Regards
John Pizzey
Dear John
What is the reason for the double linkage on the tiller, shown in the second picture of post 6? Wouldn’t you get much the same motion if you extended the tie rod (if that is the correct name for the push-pull rod) over the side of the cockpit? You’d have one link between your hand and the rudder, not three. Or five, if you also count the horizontal axes around which the levers rotate.
Regards
Robert Biegler
Hi Riobert and Rudolf, thanks for your interest.
In response to Robert, there is no double linkage, I was just trying to illustrate the extremes of movement with a full rotation of the rudder to show that it is possible. The corresponding extremes of movement of the tiller are also shown.
In response to Rudolf, sailing bow down to some extent appears to be just about inevitable in a proa because of the fore and aft symmetry required unless you can use live crew weight to counteract it. A long cockpit with all the crew at one end might help, a bit like the crew of a monohull sitting on the windward side but a lot more comfortable.
This is how I see it. I can’t immediately see why putting the sail effort as far aft as possible will assist. If you take a main sail on a vertical mast the direction of thrust will be horizontal and always at the same height above the water irrespective of where it is located, so same lever arm tending to push the nose down.
If you take a headsail the thrust will be at right angles to the inclined luff and thus it will have a vertical component (a lifting effect) as well as a horizontal component (the driving component), so the greater the lean on the headsail luff the greater the lifting component. Unfortunately the further back the mast goes to get the extra lean on the headsail the further back goes the lifting force giving less effect to lifting the bow. Thus a headsail only rig may help relieve this effect.
While on the subject of headsails and a headsail only rig as I have proposed for Pi Hi, if you take a rectangle of ply and fix a central mast to it and butt it up against a nail or a couple of spaced nails, the centreboard substitute, it will be relatively easy to push on the mast at the top or below that and tip the rectangle of ply over onto its side because the force is applied centrally. If you incline that mast to one end and run a stay from the masthead to the adjacent end of the ply then try to tip the ply over by pushing on that stay about a third the way up, where the centre of effort od a sail would be located, you might have trouble tipping the ply over, instead it may just want to rotate, it may even be impossible to tip even if you widely space the nails to represent the side force of a buried float.
A very crude experiment which I have not tried but I believe it could illustrate the benefits of doing away with a mainsail in so far as getting caught aback is concerned, and just how fast do you want to sail all the time. I believe Pi Hi’s rig can give you all the thrills you may crave for.
The dynamics of the hull design is probably most important aspect and modern computer simulations should be able to assist in coming up with the best hull form, especially rocker and fullness in the ends for a proa. Flight and Piawatha were both rockerless although the ends of Piawatha did tuck up a bit. Again size is important as crew weight on a small boat with a lot of rocker will be more effective in raising the bow than crew weight on a rockerless hull.
I hope this helps with your deliberations.
Answering these questions certainly makes one think about reasons for doing things which were long forgotten and is certainly useful for me as it make me re-assess my design thoughts and t I hope I have answered most queries, My amateur advice for what it is worth is always go back to basics and consider the fundamentals and I have always advised against taking much notice from amateurs, especially in my profession as a patent attorney where uninformed advice can be costly in the long term.
All the best,
John Pizzey
Will not happen the same problems with a symmetrical headsail like it was with the Bolger rig?
Multihuller is referring to the rig John Dalziel and I experimented with. See here for more on that. But to answer, no the symmetrical headsail won’t suffer like the Bolger rig, because the reason the BR suffered was because we put too much roach into the sail, attempting to emulate the “ideal” elliptical planform then in vogue. That was the source of the problem, not the symmetrical headsail. If we had simply used a triangular planform, the sail would have performed as expected.
Pi Hi reminds me a bit of Botje III, even the concept of automatic hull flying. Taylor imagined it, but Pizzey actually did it.
Hi again Othmar, I have just looked at the link to your earlier drawings. They say that great minds think alike but I doubt that thinking alike proves great minds, on my part anyway.
My earlier drawing below.
All the best
John Pizzey