Papillon
Hi,
I live in Sweden and I have been reading and following almost every build here on Proafile for quite a while now. I have a dream, a cruising Proa for open water, I have just started with the drawings in Freeship and in Rhino as well and are just about to start building the first model. This Proa is called Papillon, the name is french and means butterfly. For me its symbolises freedom.
The Ama in this design will be built first and used for a smaller proa for tests while I start the build of the bigger Vaka, just like Inigo Wijnen did with his Gaia I and II. According to my calculations the Ama will satisfy the needs of displacements and load to do this.
Data for the Vaka:
Design length 10m
Draft 0.45m
Lwl 9.23m
Bwl 0.82m
Displ 1.06 tonnes (might change according to design)
Data for the Ama:
Design length 6.72m
Draft 0.27m (fully loaded)
Lwl 6.35m
Bwl 0.40m
Displ 0.21 tonnes
When it comes to the hulls cl-cl, I have calculated the distances of 3.8m according to Sven Stevens figures (http://proafile.com/forums/viewthread/27/). However I think this will make a very small distance between the two hulls so in the picture below I have put in one extra meter. Im not sure where the figure of 0.42*Vaka Lwl comes from, well I think from some watertank tests for sure, but I wonder if they relate to some kind of wawe analysis between the hulls? If I go for the 3.8m Im sure its possible to adjust Ama with waterballast.
The hull design Im working on look very similar to the one of Alexanders “Nixe” which also got the sharp V hull. Only I want mine to be a bit smaller (10m or 32.8 foot ), yet with standing room. I know this will break Wharrams windage rule about the hight relative to the length a little bit. Therefore I want to keep the windage down to an absolut minimum and will use a free standing junk rig, partly to reduce the windage, partly to have an easy to maintain rig and perhaps to reuse thrown away sails. Since Im looking far away over the horizons, I want a safe rig, easy to reef and easy to go wing/wing on the milky run.
If looking at the design from the front one will see a shape of a triangle with the sides bulging out a little, this is a very strong shape which make for a light hull. The free standing masts has no forces which try to shoot them through the keel, or for that matter to snap them of. They got to be short so what could be more right than to design the proa as a shooner. The junk rig will fit well into this concept couse they has the winds force well spread over the cloth and also a low point of effort. Since rigged with two masts one can (hopefully) steer the boat with the rig only, the rudders can be kept up most of the time. Also its easy to hang a lifting jib between the front mast and the ama if needed.
When it comes to the choise of rig, I have not yet decided for sure about the junksails. I have some other ideas and will return about them. However I want to satisfy the following.. In abitrary order…
1. Easydriven, even in light winds, less motor more peace of mind.
2. Set and forget, no need for constant trimming, I know a sail has to be trimmed but why constantly? I want/need to do other things as well and if that mean loosing a knot so be it!
3. Safe and easy handled, Im no fan of a sail that is hard to reef, a sudden gust on the Atlantic sea can come fast.
4. Combining sails, no worry for me, if that mean setting a small storm sail then why not?
5. Windward, some conditions will call for a sail that can go high in windward.
Please remember that Im new at this , but want to learn so all comments is most welcome.
//Matz
Looking nice, just a quick comment: if you make the crossbeams angled just a little (longer apart at the aka then the at the ama), then you will gett less momentum (is that correct english?) in the joints of crossbeams vs aka/ ama.
Best wishes
/Garg
Looking nice, just a quick comment: if you make the crossbeams angled just a little (longer apart at the aka then the at the ama), then you will gett less momentum (is that correct english?) in the joints of crossbeams vs aka/ ama.
Best wishes
/Garg
The akas should be deeper at the vaka end and narrower at the ama end. With a parallel beam there will be a large stress concentration at the vaka end, you want to equalise the stresses in the top and bottom faces of the beam, think on a leaf spring
TINK
Just a quick warning about FEA that’s being drilled into me at the moment: Garbage in = Garbage out.
Thanks for your advices, I have not given the beams much thought since I has to design the bridge deck as well, but will keep your advices in mind.
First I will build the ama and use it as a vaka for a small proa to play with while I start the big build. But is it doable to reuse the ama or should I go for a much lighter and new ama when time come?
I’m also building a model right now and will use it to test some types of rigs. Im trying to learn more also.
Matz
Hello
I have read a lot about both Chinese junk sails as well as Crab claw. Both rigs can use unstayed masts and that is something I like to have. I want a simple and safe rig that could be used on open water. What I read about the two is that the junk easily break down from wear, also that it is heavy and slow in upwind. (Heavy can be discussed since it doesn’t need wires and deck fittings as for example a Marconi).
When it comes to crab claw it seems like everyone out there prices the rig and it is safe and easy to reef, only it can be hard to handle singlehanded. But that issue should be solved with two small sails….
Anyway, I can’t find many examples of a crab claw on a two masted schooner. My question (or rather thoughts) is, wouldn’t it be easier to shunt a crab claw on a two masted proa? This way one shouldn’t need to bring the sail all the way over to the other end. Instead one just needs to swing two slightly smaller sails around each mast, the work is done at the wider part of the deck so no worry to loose ballance and fall in teh drink. I know the issue about the balance of the CE but when sailing with two sails one can easily adjust the sails, since we are not talking top speed I have no problem about reducing one of the sails.
Also have a look on those links to a rig I found on the web… could they be applied?
http://papillonsails.wordpress.com/
http://papillonsails.wordpress.com/rigging-gear/
It’s a little bit funny about the name “papillon” since it’s the same as my project 😊
However I’m not really fully understood about how this sail will work, but I can see what they call the “tack tackle”, can this be used instead of a rail for the crab claw sail? I mean if one has a small bom rotating around the masts foot and with its other end attached to the sail, it can be used when swinging the sail around at the shunt?
All the best
Matz
I just realised there is a better idea that suits a schooner with crab claw sails. The spinnaclaw with its adjustable CE would be a good way to go for a schooner rig as it give the sailor all the control he wants by using his air rudders.
The text and picture below is from the link…
http://proafile.com/archive/article/the_spinnaclaw
The idea is to mount the crab claw boom to a spinnaker pole, and shunt the sail like a big asymmetrical chute! The reasons you would do that:
•Quicker shunts. The radial motion of the spinnaker pole combined with the fact that it travels only half as far as the traditional rig fore and aft should make for snappier shunts.
•Better helm balance off wind: traditional crab claws develop powerful weather helm on off wind courses, the result of all that sail hanging off the leeward side. The Spinnaclaw shifts approx. 20% of the sail area to windward as it bears off, thus reducing weather helm.
•Quickly adjustable CE. The pole can easily be shifted fore and aft while under sail, fine tuning the sail’s center of effort and helm balance for all courses. A nice feature for a boat that steers by weight shift and the occasional steering oar.