Although it might look simple to make - this 'arm' took some work. No-one I could find was interested in cutting it. With the right equipment it would take five minutes - for me it was hard work. Once finished I knew how it must have felt to make the last chip from the dug-out canoe, or the last little tip of the nose on an Easter Island statue.
Cut from some 6mm stainless plate - I went through many discs and wrecked a good pair of socks - one of the hazards of my angle grinding techniques ! I wouldn't make another - not without some magical cutting equipment - which those 'professionals' have, who refuse to cut things like this for you, hidden in their sad little workshops .Moan, moan ... yes I know I could have done a cad drawing of it and sent it off somewhere to be made up in polished stainless at a whacking price - but, I was happy with it roughly cut, unpolished and was quite capable of drilling the holes. I just get depressed with local engineers who have all this equipment and, it would seem, zero enthusiasm at using it for a simple one off little job.
In that sort of mood today !!!...Lets hope it works.
|Forgot all about this page - sort of got lost
My Patent extra Forestay Tensioning Lever
I made this ages ago and am quite proud of it - if it works !
A strop at the base will set the length hand tight, with a suitable clip device to the stemhead u-bolt. You need a strop below, so you can drop the arm right down to gain the max tensioning range. The strop could be either attached to the stem fitting, or to the lower shackle.
Minor adjustments can be made with the rigging screw - as the shackle can lock into the notch at the top of the lever over a range of position.( In the pic, the notch is not cut - just the hole is drilled to form it )
As in the pic - when opened up, the lever action gains about 35mm. The arm is about 12".
The nice thing is that the only thing to fabricate is the lever arm - all the rest is 'off the shelf' stuff. The bottom arrangement is just two 6mm long reach shackles. On the top, the 8mm long reach shackle replaces the clevis pin, but still acts as an attachment for the forestay eye - but importantly, pivots down to hook over into the notch at the end of the arm.
If needed - a hole can be drilled above the top notch, so a spring type clip can be pushed through, preventing any possibility of the shackle disengaging.
4mm 1x19 wire only stretches about about 13mm on a 9m length for 15% breaking load. The short strop can be something exotic/expensive 'no-stretch' racing stuff - if I'm only buying a metre !
The formula in Fenhursts book, Sail and Rig Tuning quotes -
for any wire size-
0.5mm elongation on a 1m length = 5% breaking load
1.0mm elongation - ditto - = 10% breaking load
1.5mm - ditto = 15% breaking load.
from a start point at 'hand tight'. I presume this to mean a rigging screw hand tight with no tools. So its a bit hit and miss really - but gives an idea of the stretches involved. He quotes cap shrouds at 15%, and backstay/forestay at max 35-40% as a guide.
best measured on at least a 2m length - ie -
make an accurate mark 2 m up the wire from the edge of the ferrule/swage etc, then tighten until it measures 3mm more - for 15% breaking load.
The point being is that, if I have 35mm closing range on the lever, I only need about 15mm of that to tension the wire, the other 20mm can be slack for fitting some kind of shackle - so hopefully it should do the job.
I originally planned the removable forestay for a couple of reasons - I'm not sure how well founded !
Firstly - I have a very good nick Jeckells working jib, which is hanked. The previous owner had obviously been using it with short loops fixed around the furled up genoa.
Secondly - I had my eye on a new storm jib which was going cheap at Uphill Yard, so wanted to be able to rig this if necessary
Thirdly - my foil only has one groove, so with this I can put up two headsails.
It will fix at the masthead just inside of the forestay attachment, probably on a short rope strop at the top so as to give a good clearance on the roller top unit. Where it lives when not set is to be sorted - propbably to one of the main shroud chainplates. It will then be clipped to the extra u-bolt I've put in the stemhead fitting - this is far enough aft of the roller drum to clear it. The halyard is simply the existing foresail halyard, as my roller gear has its own built-in halyard.
It will be nice to have two options - interesting to see the difference between a reefed roller and a pretty new hanked working jib into the wind - though of course you do still have the rolled genoa sitting up front. We shall see...