Graham wrote:Hey Paul, that is a beautifully-setting sail.  I'd be interested to know what your camber is.  I am interested in the relationship between camber and displacement, and what people like Arne, Paul Thompson etc, think is the ideal ratio.  I'm envious, looking at all these beautiful junk sails.  I'm looking for a cheap, suitable, fibreglass boat between 26-28' (8-9m), with moderate displacement, as I do not think my current boat is right for the project.

Camber and sail area versus displacement.

Graham, I cannot say that I have found that ideal general ratio between camber and displacement. I used to say that heavy displacement boats should have more camber than the others, but these days I am not so sure. Maybe on auxiliary rigs mainly meant for reaching and running...

For my own boats I have settled on 8% (real, measured) camber, as this has proven to both be close-winded and easy to keep in that groove between luffing and stalling. In addition, this modest camber (compared to genoas with 12-15%) works well as the wind picks up. Remember, the camber in a junksail cannot be adjusted under way. What can be easily adjusted is the sail area, so I generally rig generously. This extra sail area gives a nice long luff (including the 60-70° head) for improved upwind performance, but also spreads out a big nice area for running before.
Then, while the Bermudan sailors flatten their sails in rising winds, I drop a panel (..or three...).

Paul S. has demonstrated this beyond any doubt with his generously rigged Maxi. That sail was originally meant for a much heavier boat.

Soo, if I after all dare present a rig size and camber strategy, it may look about like this:

·         Decide how tall and heavy mast(s) the boat can carry in the conditions it is likely to meet. The answer depends on what material the mast is to be made of. This again depends on what is available at a tolerable cost. I try to keep the mast below 3% of the boat’s weight.

·         Then, rig as big a sail as possible.

·         As said, I stick with the 8% camber in the lower panels, as this is easy to make with the barrel cut method (plus Amateur Method B). The top panels are made progressively flatter, but never completely flat (..the top panel on Paul’s Maxi has a 44mm Round at both the yard and top batten...).

I hope this makes some sense...

Cheers,
Arne

Paul wrote:

Ups, you are right! I just dully translated the german expression "Backbordbug" to "port tack", but it is the other way round. Thanks for clearification, I corrected my post below!

The foto shows the position of sail I mean.

Hey Paul, that is a beautifully-setting sail.  I'd be interested to know what your camber is.  I am interested in the relationship between camber and displacement, and what people like Arne, Paul Thompson etc, think is the ideal ratio.  I'm envious, looking at all these beautiful junk sails.  I'm looking for a cheap, suitable, fibreglass boat between 26-28' (8-9m), with moderate displacement, as I do not think my current boat is right for the project.

Paul, as for getting the pointing angles symmetric or not, there are two more noise factors plying in:

1.     If the batten parrels are slack (worst with wooden masts with some taper.), the sail will ‘believe’ it has been sheeted in more on sb. tack.

2.     The sheeting point should be asymmetric to make the sail swing symmetrically back and forth when tacking. How much?
Excactly...

..good luck with that...

Arne

Paul,

I am confused.
If the sail rides at the port side of the mast, then sailing on the port tack means that the mast is on the leeside of the sail, right?

Arne

Paul, I’m very happy on your behalf!

It is quite a relief to see when a sail design turns out to work well. In this case, it was not a big surprise, since it is a 1:1 copy of Boudicca’s sail. However, Ilvy’s sail seems to be set with more mast balance.

I have a few questions for you, so I can ‘finalise’ the design of that rig:

·        Could you measure the horizontal distance from the luff of the sail at work to the middle of the mast section? In other words  -  what is the current mast balance?

·        Have you found a considerable difference in pointing angle on port or sb. tack?

·        Could you measure the actual max camber in one of the lower panels?

I hope to get rid of the last traces of fear for big mast balance, by busting the myth of the bad tack, even with rather high values of that balance...

Anyway, keep up the great journey!

Arne

http://goo.gl/khii3l