Thanks for your replies folks.  I do have a double block at the masthead at this stage but intend to change to two singles as soon as possible.  I was not thinking of the stresses on the mast but more of chafe, as the lead of the parts to the yard is slightly different to the part going down to the deck.  This is most evident when the drift is only 300 - 350mm, but once I have one panel down, and the drift increases to 1.3m, it is hardly noticeable.  Perhaps if I have two single blocks up there the movement in the blocks will absorb some of the twisting force.  The problem only occurs when the yard swings around in sloppy seas and light winds.  The yard swings to windward and then swings back, wrenching the masthead sideways.  The leverage is astonishing and the top of the mast twitches like a rod with a big fish on it!.  If the wind is steady and the sail is full of wind there does not seem to be a problem.

Stavanger, Thursday

 

 

I agree that the drift of Johanna is too short, but somehow we seem to get away with it. The tackline  is a bungee so the whole sail can lift a bit when the sail swings out. Since the mast is rather overstrong for the 3 ton displacement, I think the yard, rather than the mast, is the weak part. The main tube is only 65 x 3.5mm so the sideways loads are quite high. However, since I reef in mid-F4, it is not a big problem. On both my next boats, Broremann and Frøken Sørensen, I have about 50cm drift, and that looks good.

 

 

The PJR’s requirement of  a drift of 0.3 yard length would result in a 1.3m taller mast on Johanna than today  -  lots of dead weight. I think 0.3m taller mast would have been fine.

 

When studying photos of Arion, it seems that the drift is only slightly  on the short side. I suggest you stand at the mast and sight up along it while under sail. If the bend is fairly even, up along it, I would not worry.

 

 

Arne

This matter has been discussed elsewhere (by me and others) but I wanted to ask members for specific comments on this topic.  PJR recommends that the top of the mast should be 0.3 of batten length above the sling point on the yard when the sail is fully hoisted.  On Arion, with a batten length of 4.6m, this would be 1.38m.  My clearance is actually about 500mm and the drift between the halyard blocks must be about 300mm.  Boats like Peregrine seem to get away with it and I have sailed Arion very hard, but have become nervous of the wringing action on the masthead when the yard slams about, as it does in certain conditions like light winds and sloppy seas.  My mast is massively strong but I have noticed the masthead whip in these conditions and am now sailing with one panel reefed in all but the smoothest seas.  This is annoying though because Arion is a boat that likes all the sail it can carry.  I have 36sq m for a displacement of 5 tonnes and would like 10% more sail area for light winds. I am thinking that one of these days I might take the mast out and add a metre to the top of it. Of course if I added 10% (an extra panel perhaps) I'd have to go up another 2 metres!   What do others think?