Claude,

Looking at your latest animation, several things become clear to me.

One thing I'm certain about is that mast hoops or parrel beads are not going to work here - the sail is going to need to swing forwards as it comes down.

Short batten parrels are not going to act as they normally do, when the mast is vertical or forward-raked. There, they prevent the sail from swinging forward under gravity, at the expense of extra friction. On your sail, the tendency of the sail to swing forward under gravity is very much less (though still there to a small extent, I think). You may wish to try them - but 'try' is the operative word. Such things as this cannot be determined for sure on the computer screen. 

You are going to need to reduce the luff length of the top panel, to the same length as the next two panels down. Even if the yard has extra length at the forward end, and a parrel is rigged between its forward end and the halyard attachment point, I cannot see the present shape being satisfactory. I think it would give you trouble. Either the yard should be at a greater angle, and longer, or the top panel's area should be less. I like a short yard, and would keep it at the angle and length that you have drawn, reducing the area of the top panel considerably.

This sail is quite similar in concept to my current sail, and should operate in a similar way, despite the aft-raked mast. I use batten parrels that are semi-short, and do not attempt to use them to position the sail (first, I tried short batten parrels, and rejected them). I have an upper luff hauling parrel and a lower luff hauling parrel, and use these to haul the sail back as far as your animation shows, when I am sailing to windward; but I leave them slacker when I am reefed right down to two panels. I think you will need to do the same.

But having said all that, I still think that using a mast with such an aft rake is going to introduce, not only some 'known unknowns', but also some 'unknown unknowns', and you cannot expect to get a 'right-first-time' rig. Even if you do not want to make a scaled down model, I would still advocate making a trial sail of polytarp at minimal expense. It will last a year, and then you will have enough experience to know what kind of sail you really want, as opposed to the kind of sail you thought you wanted. I have made quite a number of rigs of various designs, and the one thing they all have in common is that they have taught me that what looks absolutely brilliant on the computer screen does not always survive the shock of being taken to sea.

Annie Hill wrote:

I have never used short batten parrels, but those people who have have concluded that they certainly add a lot of friction when raising the sail.

As for mast hoops - it's a bit hard to visualise in two dimensions, but the sail moves around quite a lot in relation to the mast, because unlike most rigs, it goes through 180^o and sometimes even more.  Being held to the mast with rope, allows it to make its own subtle adjustments which I think a rigid attachment point, such as hoops, would inhibit.  There is also the fact that hoops can entangle themselves, which would be a nuisance.

In your animation - which is a resource that most of us do not have access to - it shows the yard and battens ending up behind the mast.

Hi Annie,

Concerning friction and mast hoops, I did not think of rigid hoops such as these but of flexible ones like these parrel beads .

Concerning the animation it is not realistic. It just follows the method described in PJR to control battens stagger. As I wrote on my previous post, it is "gravity alone" (ie without any batten parrels incidence).

In fact, whatever the choice of batten parrels, reefing will follow mast rake the difference being that with the longest possible barrels (ie attached the most forward of battens) battens/mast overlap will come to a minimum as shown by this new animation (lower than the 0.06 x length of batten required by PJR rule) while with shorter batten parrels this overlap may be kept at a satisfactory level (although It may lead to negative stagger - a point I should verify).

Once reefing follows mast rake there should not be any risk of yard and battens ending up behind the mast.

The real question is friction and I still do not understand why short batten parrels (I never meant tight batten parrels) may lead to more friction than long batten parrels.

I do admit they limit the possible balance swing of the sail aft/foreward and then possibly affect the "subtility" of junk rig but I still wait sound arguments about friction.

Claude

David Tyler wrote:

Seriously, I think that a model is indicated here. You are rigging a boat that is somewhat unusual, you are stepping outside of common practice with such an aft-raked mast, and you are drawing sail shapes of your own, not following a design that someone else has already made and proved, and so you are "taking a bet" on the outcome.

Do you really think I may really make a satisfying model for 50 € ? I do not.

No scale model (unless 1:1) will give a realistic appreciation as most parameters cant be  set proportional in the model as they are to finally be.

Experience and expertise should substitute. That is why I did join JRA.

PJR states how one should verify how battens do stagger and how yard or top batten length may cope with top lifts when reefing.

I did as stated by PJR as shown by this reefing animation.

I does immediately show that if reefing is left to gravity alone with too long batten parrels, it just cannot work. Whatever its size, any model will lead to the same conclusion.

It is clear, without need of any model that if, when reefing,  sail and battens are not forced to slide forward along the mast in order to keep a minimum overlap, it cant work.

This is why I was questionning PJR statements in my previous post :

• " Short batten parrels cannot really be recommended ", but why ? Has any one any sound advice or experience to sustain this PJR assertion
  
• " Mast hoops would interfere with the essential flexibility of attitude of a Chinese sail, and are not considered to be worth further investigation". Once again why ? 

I have not found any reasons in PJR for these two assertions however important they are for this "somewhat unusual"project of Ar Vag melen conversion to junk rig. May one also explain me, for instance, why possible means to keep the sail and battens sliding along the mast such as yard haul and tack parrels should be disregarded ?

Claude

Claude L'Honnen wrote:

Arne Kverneland wrote:I would make (a) model rather large, at 1:10, or better 1:5 scale. 

Arne

as for my 50-50 odds  -  I am not a betting shop...

Are you serious ? Why not a 1:1 model scale !

The question is still unanswered : is it worth trying ?

Claude

Claude,

the 1:5 model may be a bit ambitious, but the 1:10 is easy to make. I haven't made any models, but others have done it and reported that it helps to see how the sail sets, reefs and furls. This would be particularly useful since you are about to break new ground with the mast raking that much aft.

Arne

Claude,

just a quick note.

I know that others have made a model sail with thin cloth or plastic film before settling on the full scale sail. I think that would give a lot of answers  as to how the battens behave, and what sort of parrels you need.  It would also tell how the lazyjacks work and if you need to lengthen the top batten and yard to keep the aft end from catching the lazyjacks. You may even want to fit a 'batten parrel' on the yard. I would make the  model rather large, at 1:10, or better 1:5 scale. 

Arne

as for my 50-50 odds  -  I am not a betting shop...