TOPIC:

I am removing the muscle box on my rather old Fairey Albacore 1717 and I intend to fit a low friction cascade system to enable better halliard tension adjustment. It seems simple enough to do and I need some guidance as to which blocks to use.



In heavy wind the suggested rig tension is around 350 lbs and this load is presumably shared by the halliard and shrouds. The shrouds are likely to be loaded alternately when going up wind with the leeward one going slightly slack. I presume the halliard will always be under the greatest load when going up wind.




Am I right in thinking that the 350 lbs rig tension would be shared between the halliard and shrouds and therefore the maximun loading on the halliard and the first turning block in the cascade system would be no more than 50% of 350 lbs or thereabouts?



And one final point, what is the best purchase power to use? 8:1 or 16:1.

Is 8:1 enough or does it need 16:1 to be comfortable and effective.

I am also experiencing difficulty in sourcing the best blocks to use. Any suggestions as to suppliers now that Speeed are no longer?

Thanks

Dom





dom3152010-06-07 09:12:04

FOWLER wrote:

Phil

MikeMac has an extra block on the jib halyard just to make it easy to hoist the jib!

Is that not to reduce mast compression loads and hence reduce bend caused by the jib halyard?

Phil



MikeMac has an extra block on the jib halyard just to make it easy to hoist the jib!

Yes you are right and I should have realised that only seeing that far forward is harder as your eyes dim. I'll look at that as it makes sense ~ thanks.

dom315 wrote:

... However one thing I have discovered is that no matter how often I calibrate the rig tension with a loos guage and make calibration marks on the control line, there is always some degree of variation. I may be knots still settling in.

Modern ropes are very low stretch but they do creep which may be why you are seeing the variation. Also you should be using splices rather than knots as they are much stronger.



The best place to calibrate is where the hook goes onto the haliyard softeye.



JW JohnW2010-06-14 20:50:00

I have removed the muscle box and fitted a 16:1 cascade. It operates from a block and beckett attached to the hook which goes through the halliard soft eye. This then goes back through a cheek block on the centerboard box and then back through the orginal block and then forms a cascade along the side of the centreboard box.



All in all it makes for a low friction solution at reasonably low cost which is very effective. However one thing I have discovered is that no matter how often I calibrate the rig tension with a loos guage and make calibration marks on the control line, there is always some degree of variation. I may be knots still settling in.



It is very useful to get peoples' views on this forum.

Good point John!


Mike Mac has a cascade at the top of his jib before it enters the mast, this would reduce friction but makes halyard lengths difficult.


Cheers


Phil

It's a big ask for a one string on an Alb.



The Scorpion & Merlin, there may be others, are two classes that have adopted the idea, these are deckstepped with a spinny, the spinny being the most useful tool in their armory off wind, the position of the rig not so crucial.

The Alb has only the rig, which takes far more controlling, to make the difference off wind, making it far more critical to try a get right. The one string I am sure will put you in the right area of rake & tension, but there is no substiute for the feel of the thing, (a little bit on, a little bit off)& never forgetting the vang is the most potent control you have at your disposal.



Interesting project though & something Nev & I have obviously talked through, but not got around to.



Interested by-stander. FOWLER2010-06-14 18:34:21

MrGin wrote:

I reckon its better to use a quad and a triple with tails going back along the centre board case. This evens the load out and takes away the need away for a bullet prrof block, although this is proably a more expensive system.

And has a lot more friction in it. I have just got rid of all my triples and the system runs much more smoothly.



JW

I reckon its better to use a quad and a triple with tails going back along the centre board case. This evens the load out and takes away the need away for a bullet prrof block, although this is proably a more expensive system.


Cheers


Phil


A6504 "Nemesis"


Northern Rep

Thanks for the information John, thats very useful.

I guess most of the loading is on the top sheave and then the sheave at the bottom of the mast. And I will do as you suggest and use a couple of high tesnion blocks in the first part of the cascade. Lets just hope the old boat can take it.

Thanks

Dom

Hi Dom,

350lbs is the static rig tension in shrouds the dinghy park, the jib haliyard tensions will be slighly less than this due to the increased angle of the jib luff (but I dont think 50% lower). However I dont think you can assume this figure will sailing, cranking on the kicker upwind could inrease the jib haliyard tension above the 350lbs level.



P&B have just done some mods on my boat including the jib haliyard. For the first stage in the cascase you need to use high tension blocks. I would suggest that 8:1 is not sufficent purchase, you need 12:1 or 16:1.

For 12:1 use a 3:1 purchase on the first stage of the cascade with a block such as this:

shop.pinbax.com/index.asp?selection=detailed&uid=36174

(400kg working load).

The benefit of fitting the additional high level block on the jib halyard, is the reduction of effort needed to straighten the rig, particularly useful when sailing to windward.



I have heard the lower compression argument but this I feel is the biggest gain for little trade off.



Mast bend can ge controled by spreaders & ram / strut.FOWLER2010-06-17 17:10:45