P12 Proa Rig
Most (if not all) cruising pacific proas have one main disadvantage - they have not enough space for crew - inside and outside.
For my concept P12 I think the inside accomodations are as well as possible for four crew. My next consideration was to design the same maximum living space outside. The few existing proas over 10 m show me small ditches which are far away of any comfort. If I sail in warm waters, life happens mainly in the cockpit or on deck. Hence I real cockpit was to define.
If I use a standard slup rig, the mast position must be around one meter to luff, that the stays could hold the rig. But then the mast enthrone where my cockpit should be. Inclusive the crosswise support to the beams, winches, and lines.
My solution is an A-mast which stand alongside on both beams - and the cockpit is empty.
Advantages:
* Large and free cockpit (bimini possible)
* Strong position of the masts at the beams
* Good working space for sail handling
* Three furler sails for easy reefing, and trimming
* Three stays to lee (if aback situation)
* Good balancing of the working forces at the vaka
Disadvantages
* More effort in building and costs?
* More topp weight?
* Problems with furlers?
I like your idea!!!
I think there is much merit in an A-frame rig. I have been irritated at “the mast in the middle of the would-be cockpit” - problem to. I think this is a brilliant solution. The masts would not have to be twice as heavy as one, because an A-frame is much more stable and strong than a single mast. One should be able to use a lighter thinner masts to counter the added weight somewhat.
I like the idea of having two mainsails, to be able to change CE for each shunt, like Gaias Dream does with a sliding mast-foot.
Thanks for al your great ideas!
This will consume a lot of my building-time today.. I have to sketch and think about this…
Johannes.
Add a track for the boom tack (?) and you could alter the sail angle into or away from the wind for light or heavy wind?
Of course it would then be in the way again….. : )
Does it roll onto the boom for reefing the main?
I agree with you that the P12 looks very comfortable. I’d like to cruise the Med coast in him, that’s for sure. 😊
Since all the sails are set like genoa jibs (“flying”) they will require a a much stiffer and stronger rig than say… a crab claw, Wharram “wing sail” or Chinese lug, where the sail is supported by a spar along its length. I think it could work well, and be a great cruising rig, but it will be more expensive and more high strung than those options.
If compared to a standard “Brown” proa sloop (I love how we can call that a “standard rig”!) I suspect it will be heavier and not as efficient due to sag of the main sail, extra mast, and the planform is not as optimum. I recall Russell saying how his boats had comparatively small mast sections because of the unique proa geometry, which allowed better performance, reduced weight, and cost when compared to a similar cat or tri.
The plus side is that the boat would be a snap to get underway and to put back to bed, I imagine that this would be a plus for chartering, day sails, etc.
Add a track for the boom tack (?) and you could alter the sail angle into or away from the wind for light or heavy wind? Of course it would then be in the way again….. : ) Does it roll onto the boom for reefing the main?
I don’t believe, that a short track (max. 80 cm) will improve the sailing abilities so much. You need two lines more to handle it, and in this area there are already two more lines for lift/lower the rudder. One of the main requirements for P12 is easy handling, not maximum performance.
The main sail is set like a vertical jib, and uses the same furler.
Since all the sails are set like genoa jibs (“flying”) they will require a a much stiffer and stronger rig than say… a crab claw, Wharram “wing sail” or Chinese lug, where the sail is supported by a spar along its length. I think it could work well, and be a great cruising rig, but it will be more expensive and more high strung than those options.
That’s right, the effort for that rig will be higher, as for a “standard” one. But how I said in my introduction, there are some arguments which justify the effort. Everybody who has sailed a pac proa with a two rudder system and crabclaw knows the stress during shunting, especially single handed.
Hence I want a rigg which can easiest and save handled eg. by a family or charter crew too. All work must be done from the cockpit.
Why should it be more high strung? At last it works like a “standard” slup rig of which many thousands are sailing. Also google for “a-mast”. The rig tensions can be calculated to reduce the sag to an acceptable minimum. Next year we are experience it.
The plus side is that the boat would be a snap to get underway and to put back to bed, I imagine that this would be a plus for chartering, day sails, etc.
That’s the concept of the P12. To design a pac proa for cruising use without compromises. Sometime a pac proa should find the way into the range of “normal” multihulls, away from any exotic status.
Cheers, and many thanks for your comments
Othmar
That’s an elegant design, coherently programmed and nicely executed.
The A frame mast(s?) will probably add a little weight, cost and windage, but as you said it’s going to be a comfortable cruiser (which I heartily endorse).
To keep sag to a reasonable level, rig stresses are going to be high but it’s all straight compression and tension, easily doable. I would take a careful look at the base of the mainsail, that’s going to be a lot of uplift in the middle of a fairly flat area.
Only other comment is to look for a competent open minded sail maker.
cheers,
Skip
I wonder if the cockpit could be made even bigger? Cockpits are low windage after all.
Edit: how about a support for a single mast below a seat.
I would take a careful look at the base of the mainsail, that’s going to be a lot of uplift in the middle of a fairly flat area.
The “main stay” is fixed at a massive bulkhead below with UD carbon stripes till the bottom.
I wonder if the cockpit could be made even bigger? Cockpits are low windage after all. Edit: how about a support for a single mast below a seat.
Why bigger? The boat is construed for four persons, and for these it’s big enough. I want also to restrict the weight to windward.
In addition to the arguments for an A-mast above, one further cause:
The boat is demountable for transport from boatyard to next water, and also for eg. inside storage in winter. Vaka, beams, cockpit, and ama are single parts. Therefore a strong fixed beam transversely in the cockpit is IMO not the best solution. But at last it would be feasible too.
EDIT: Annother advantage for beam mounting of an A-mast: You are free to shift the mast feet abeam to choose the best angles for the stays.
Why bigger?
Just so that the mast could have some room in the cockpit yet the people could have theirs as well. P12 looks very well thought out either way.
It’s the catamaran/multihull open deck thinking. A proa is more like a tri. Or is it…...
( i like your weekender proa ).
A proa is more like a tri. Or is it…...
Well, maybe and maybe not . . . . 😊
I left a picture of my avatar over on your ‘Te-Pk work in progress’ thread, Alex, as requested long ago. There’s a short description as well. Sorry for the delay. http://proafile.com/forums/viewthread/81/
Multihuller - get the thread title change to P12 and post updates ! I see it s coming along nicely.
The google translation of the German is a hoot - you should read it.
Some 3D sketches of the A-rigged P12. Building of the hulls is slowly coming to an end.
John put some comments to the A-frame rig in another thread, but I will answer here.
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.
Perhaps my English in’t good enough to understand, what you would say with. I have listed the advantages of the A-frame solution on top of this thread.
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.
In principle you’re right, but we made the beam connection very stiff, and the distance of the mast feet to the vaka is short. So we think, the vertical movement between both mast feet should be very small. Further we had choosen a bridle from beam connections on ama to mast top, similar as you recommended. The 3D-sketches are made some time ago. But at the end practice will show, if we are right.
Thanks for your comments.
Othmar
Hi Othmar, I am glad you are confident in your choice and it would be wonderful to see you on the water one day, I’ll certainly keep a look out for the boat with the inclined A-frame mast and you can look for out the boat with the mast inclined both ways. You mentioned the designs of 40 years ago being ahead of their times, it’s always the way then things rationalise to something boring. I hope proas don’t end up with one basic configuration as that would also be boring. The only other A-frame mast I can recall was on a Wharram cat, the builder used two long ladders to form the A-frame, I guess he was going reef hunting and wanted an easy to climb lookout.
The one thing that stands out on this site are the incredible wooden creations the proa enthusiasts create, makes me jealous as I don’t have the patience to work with wood, I prefer fibreglass. I started using the stuff back in 1959 when I reclaimed a cedar planked Canadian canoe that was discarded by doing basic repairs to the cedar planks then sheathing it in glass cloth, it was originally canvas covered.
All the best
John Pizzey