Anonymous wrote:
A drawing exercise with hi-balance sail
Frederik uses to publish photos from his building progress of Hogfish on FB, both on his own account and on the FB group.
Recently he published an old sailplan from me, not the one he is actually going to use - a Paul Thompson design. Then I was dumb enough to stick out my head and air my view on plumb masts contra raked ones. I shouldn’t have done that, least of all on FB, where most of the contributors are mainly armchair enthusiasts.
Still, Paul was generous and mailed me his sailplan in .dxf format to let me draw my preferred version onto it. I have now returned it to him with my extra details added.
This sail differs quite a bit from the first one I sent to Frederik some years ago. Thanks to Paul Schnabel’s experience with a Johanna 60 type sail on his Maxi 77, which he pushed further and further forward, I could now conclude that 27% mast balance works well.
I therefore picked another Johanna 60 master sail from my stack, scaled it up and fitted it to a plumb mast on Hogfish, a little aft of the original one (stub still visible). The lovely thing with this is to see how close the CE now sits to the mast. This will ensure easier steering downwind than with my former low-balance sails.
Now, this is just an exercise and a demo of the hi-balance sail. I admit that I am not so fond of forward-raking masts, but when Paul T. says that they have worked well on his boats, I have to surrender - although a bit reluctantly...
I can only wish you both good luck!
Arne
(..full size diagram under Arne's sketches, Section 8...)
The problem Arne, is that your mast is plumb in the middle of Frederik's nice big double bank and my design brief was to preserve it, as Frederik has not taken the celibacy vows yet, nor has he any plans to do so anytime in the future. A mast in the middle of a double bunk can seriously interfere with some (admittedly non sailing) activities.
The 4° of forward rake that I've put in the mast is in fact the standard rake that I give all my designs where it is possible. I avoid vertical masts if it can be done.
As for sail balance, as you well know, I have been using varying amounts since 2013 when I put 22% into LC's foresail. That sail shape has been one of my most successful ever and I've used it on a number of my designs. The sail for Frederik's Hogfish is based on it, as was the sail I made for Graham Cox's Blue Moon. Incidentally LC's foremast was raked forward 4°.
I've put 28% sail balance in the sail for Frederick (measured along the batten, from the center line of the mast to the the luff). There is absolutely nothing new about using a decent amount of sail balance when it will do useful work. I feel you can safely use up to 33% sail balance. However somewhere around that point instability will start to occur... I suspect that the amount of camber will also figure in what that point is.