Since the Practical Junk Rig book was written in the 70's, there have been many developments......
The most important (in my opinion) are:
- Putting a curve into the sail to induce an aerofoil effect and
- Using a stainless steel cap fitting, fixed to the sail, on the batten ends to attach lines and so, with using eyelets to lash the sail to the batten, these completely eliminate the need for batten pockets, loops to attach lines etc,etc etc...
Home made batten cap ends recipe:
I used 1 1/8" internal dia stainless steel tube, 6" long, firstly, I flattened the ends in a vice....
the hero caught in the act:
then Supergit drilled a 8mm hole in the flat for a 5mm long shackle (i.e to attach the control lines)
- Drill 2 x 10mm holes at the top of pipe, and then two 6mm holes at the bottom of the tube
- Drill a countersink into the bottom holes (from the inside) for bolts.
Attach to the sail by 6mm nuts with dome head nuts, sandwiched between two 1" SS repair washers (PS I also reinforced the sail with additional sailcloth panels...just to be sure!!)
Attach to sail...
ready to fit to the batten...
Slide in the 1" aluminium battens into cap and bobs-yer-wotsits job done!!
Note: to reduce the chemical reaction of having aluminium next to stainless steel, and make a tight fit, I wound the batten ends with white electrical PVC tape before inserting....
Then cook for 3/4 hour in a moderate gas setting .... nooooooo 'es getting carried away again moosh.......
Apparently a major defect with the original junk rig sail design was being flat, they have no "lift", which is the effect caused by the wind flowing over an aerofoil shaped sail....
So, when compared to the conventional Bermudan type sail, tacking close to the wing is not very good, or
"Bleedin' crap upwind, Harry me old cock-sparrow"
...a highly original but technically correct term I believe, Alistair old chap....
However, if you could put a curve into the sails, so you do have an aerofoil effect... its a by jingo and a quick hearty wave as you steam along, thrashing along, overtaking the prats in the far inferior Bermudan type rigs.... dreams dreams oh hopeful dreams....
Note: if you contact Robin Blain at Sunbird marine, he can provide you an information pack (£25) that details many articles on the subject.. or join the Junk Rig Association (JRA), you can do this through the internet, then you can access their extensive library for free (good website advice forum too!)...
From investigation, and much advice from junkie types (sailors not druggies!), I have ignored using 'wishbone' type booms and battens and other super-dooper 'high-tec' solutions: they are all too bloody complicated and too much work for a simple soul like me ! ....
So, there are two much simpler approaches:
- As with Bermudan sails, build in 'fullness' when the sail is designed and sewed...whilst a very straight forward concept (details available through the JRA)...... it is well beyond my limited sewing capabilities... straight lines is about it for me innit, Guvnor !! or...
- Cut the full length batten into 2 or 3 pieces and fit in tapered wedges. so, when the sail is lashed to the battens and batten ends fitted (above) a curve is induced. Note: using wedges means rather than simply bending the batten means that the sail can flex and take up the same shape after tacking... the picky purist will say "3 corners do not a smooth curve make"... but from extensive wind tunnel tests, this makes no difference... so its yahboo to you bigheaded know-all, up yours and nah-na-de-nah-nah n' all that!
(1) Cut the battens at three points: 30%, 20% and 50% (measured from the luff), when the tapered wedges are fitted this makes a shape very similar to an aircraft wing, tip-top-boo-ga-loo giving a nice smooth air flow...
(2) From the various wind tunnel tests and trials it would seem that the ideal curve is about 6 degrees.... I am led to beleive that this is worked out measuring the central point of the curve to the horizontal plane, divide one by the other add granny's age divide by two bees add the first number you think of etc etc ... in short, for thickos like me, simply jump to the last page and go with what they tells yer!!
Having sorted all that out technical stuff , you then find in practice that you can use double sided or single sided tapers.... you can buy these from Sunbird marine (aluminium) or make them from aluminium, GRP, nylon or wood .. this is an example of a home made wooden version (seen at the JRA rally)....
Looks good, but there's a problem Houston...it would seem that with wooden or nylon wedges, when you tack, the force can simply snap them in two, so I decided I would go for single 6 degree tapered aluminium wedges...one thought being that if I need to increase the angle or change to doubles, this could be done at a later stage...
So with the help of good ol' Bernie Godden (the bosun) and his trusty lathe, he produced the beasts (bottom RH corner)... what a fantastic job!!!
The final result, attached to the end caps and sail lashed on with 3mm line through the eyelets etc etc....
"Oooooo Harry, you can see the curve from 'ere"...
Just one more point, apparently as the battens flex, the wedges rub against the batten, aluminium to aluminium, this can cause a 'orrible black stain on the sail, some sort of very flexible cover is needed, some have used plastic tubing, I thought of using some bicycle inner tube, but for now I have wound it with gaffer taper.....
Gypsy is a bit concerned that the battens might split at the join, rather than the taper snapping.... personally, I think she is barking up the wrong tree.... but we shall see?!! (The jokes are getting worse, Harry).....
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