Hi All,

Had a very interesting and illuminating day with David Tyler and Weaverbird here in Poole Harbour.  David Harding, noted journalist with PBO and Yachting Monthly, was watching closely.  There will be some good photos and maybe an article to come out of it. 

Yes Weaverbird did point higher, but more like 2° to 3°,  but that was, for me, not the main lesson. 

What really impressed me was the ‘tolerance’ of the soft wingsail, when close hauled.  Amiina has quite a narrow ‘groove’, on the wind, between luffing and stalling.  The soft wingsail seemed to me to be more tolerant, with a wider groove. 

Other points to note.  Weaverbird is in full cruising mode with lots of stores etc. onboard, and with her outboard down all the time.   On the other hand, she is a 25 year, or more(?) more modern hull design, with 2 foot longer waterline, and 22/25(?) sq. m. sail.  Amiina has only 173 sq. ft. (16.1sq.m).

The sea was pretty flat, in Poole Harbour Upper Triangle. Wind SW F3 to 4.  Fairly steady. , top of the tide, so little tidal effect.   Shows the importance of more like  to like trials, with same hulls and same sail areas. 

Cheers, Edward

ps. Whatever happened to our old title “ Junk Rig and Advanced Cruising Rig Association”. 

With ever increasing commercial interest in soft wing sails, is it timely to resurrect our former mission?

Here are the Polauto plots for Weaverbird's runs yesterday.

What I think I'm seeing is that Amiina's best VMG is at 36˚ AWA on port tack and 32˚ AWA on starboard tack. Edward tells me that there is a sharp fall-off in performance if he heads too high and the jiblets flutter - the boat has to be kept "in the groove". That would appear to be borne out by the fact there are no results showing at less than 36˚ AWA on port tack. Amiina seems to have starboard as her "best tack". That would be with the mast to windward of the mainsail's luff, giving better airflow on the lee side.

The plots for Weaverbird are showing that I didn't really get enough data at the close reaching angles. I got plenty of data when close hauled, though, and it appears that I get best VMG at 32˚ AWA under full sail on both tacks (run 1 P & S) and 36˚ AWA with one reef on both tacks (run 2 P & S). Yesterday was quite breezy, and I was just able to hold onto full sail for run 1 and took a reef for run 2. I get the feeling that the "groove" when sailing to windward is quite wide - there is a wide band of AWA in which she sails well, or high tolerance to varying angles of incidence of wind on the sail. This is what I had hoped and expected to find, as a feature of the rounded luff. of the wing sail.

This is quite encouraging. David Harding, who has done more boat tests than I've had hot dinners, reckons to see 32˚ AWA as giving the best performance on bermudan rigged boats. However, this would be measured by a masthead wind sensor, which may well be giving a different reading from our wind sensor out on the boat's quarter.

And perhaps I was right when I was observing a difference in pointing angles of 3˚- 5˚ : 32˚ vs 36˚!

David wrote:

Weaverbird is in Poole Harbour, and this morning we managed a few runs on Amiina with the performance measuring equipment rigged. The data is yet to be processed. 

This afternoon, we sailed Weaverbird (wing sail) and Amiina (split junk) together, assessing relative pointing angles and speed. On all points of sail, our speeds were equal. Amiina is a little shorter, so Weaverbird should have been faster by about 3.5%, but since Weaverbird cannot raise the outboard whereas Amiina can, and Weaverbird has twin keels whereas Amiina has a fin keel, I think this would account for it.

However, the noticeable difference was that Weaverbird was able to point appreciably higher, by about 3 -5 degrees, while sailing as fast.

Edward disagrees, says the pointing difference was 2 - 2.5 degrees!

I did two runs on each tack on Weaverbird this morning. CSV files for both boats are attached.

David, if you are pointing that much higher, whilst dragging an outboard, it says a lot for the latest rig.  Look forward to seeing the full stats, speed and tacking angle.

well done.

Hi David, her mooring is on the Plym just off Oreston but she will not be there till late summer.

Mark