David T wrote:

“If I recall correctly, Slieve, you designed your sail with some convexity in the luff, so that it would want to set better without so much intervention in the form of

Hong Kong parrels or running luff parrels, and this seems to have been justified, if you only have to use one Hong Kong parrel.”

 

Yes, David, I built an open frame model rig and let the battens find their natural balance with a curved leech and curved luff, and copied that into the full size rig. My argument was that the tight leech pushes the battens forward and it requires a tight but curved luff to push them back and find equilibrium. The mistake I made was to not allow for the downward pull of the sheet, which is most pronounced when close hauled. (Remember I sheet the split junk tighter than normal junks as the camber of the 'jibs' allows me to point higher).

 

In practice there is little need for HKs when the sheet is eased, but when close hauled I feel I really need some form of peak halyard to top the yard up against the pull of the sheet, and intend to experiment in this area. I believe there is a lot to learn by making frame model rigs to get the structure right, and filling in the cloth after the rig has been designed. Vincent Reddish reminded us that the Chinese built the frame and tensioned it before filling in the gaps with cloth. I feel that too many ‘adjusting’ lines are an indication of a poorly designed structure, and some of the ‘90s rigs are a knitter’s nightmare. Rig designers should KISS.

 

Cheers

Slieve

I’ve always thought it correct to keep the HK parrels on the sail side of the mast to keep the diagonal stability on both tacks and even if the sail should move back forward or backwards. My understanding is that they were not so critical with the early Chinese sails which were loosely woven and would not tend to form creases, but were found necessary with the more tightly machine woven materials of more recent years.

 

My big question has always been as to why they were always placed in the fore part of the sail. It makes sense to place them there with fan shaped panels, as the panels are narrower there they would be shorter there, but with parallel panels as encouraged by PJR then it should make no difference if placed further back along the batten. In practice it would seem sensible to place them as far aft as possible when using cambered panels.

 

On Poppy’s rig I have fitted just one HK parrel, on the third panel down, and placed it at the leech rather than the luff. It seems to do the job quite well, though I think it has stretched a little and now needs readjusting. This is just an idea of my own, but I’m pleased that the HK only affects the camber towards the luff where it is not so important. It’s just a thought.

 

Cheers

Slieve

Well yes, it does appear to make sense with regards to keeping the lines of the sail. However my experience with Aphrodite is that the Hong Kong parrels are quite sensitive to length and a change as little as 50mm makes an observable difference.

We (Annie and I) have not finished rigging Aphrodite (we are going back to Opua in February) but what we have found is the process of adjusting the Hong Kong parrels has us sending the sail up and down the mast like a proverbial yo-yo.

With the pronounced taper in a junk mast, I'd think that you could have problems. I do however note that Sebastian's Hong Kong parells are at quite a low angle and therefore are quite long. That might reduce sensitivity to changes in length.  On Aphrodite the Hong Kong parrells are at 45deg and therefore are quite short.

I'd be interested in what Arne has to say about this.