Jump to content

Downhaul (Cunningham) power?


MartinRF

Recommended Posts

 

2:1 head shackle is Tylaska H5

 

 

or for those running a more budget style campaign they could use a "mylaska" available at all good marine stores :)

 

(also known as a shackle and a sheave)

 

Ah now that's a great idea... has it ever unscrewed itself though? Guess you just need to tighten it with a shackle key…

Link to post
Share on other sites

 

2:1 head shackle is Tylaska H5

 

 

or for those running a more budget style campaign they could use a "mylaska" available at all good marine stores :)

 

(also known as a shackle and a sheave)

 

Ah now that's a great idea... has it ever unscrewed itself though? Guess you just need to tighten it with a shackle key…

 

Actually that is not a good idea.

 

One day that rope will jump off the sheave. expect it to happen when you are reefing in 40 knots.

Also quite quickly the sheave will get mutilated then it will wreck your rope.

 

Tylaska's aren't too expensive and available from Fosters (Harken NZ)

Link to post
Share on other sites

yes your points are correct mr wolf, when the halyard is slack the shackle can move around allowing the rope to jump off, but a bit of tape each time rectifies this issue.

 

We have been using the same sheave now for 2 years and it has not been at all damaged and has not been mutilating the rope.

 

"Tylaska" is a much more elegant solution. But "Mylaska" is definitly a solution.

Link to post
Share on other sites

Tylaska H5 are made from aluminium, I thought Mr Wolf, you are adimant aluminium has no place in a marine envrionment. Or does that not apply to aluminum (carefully note the spelling) as tylaska's are made in the US..... :o

Link to post
Share on other sites

We've been using the same 6mm stainless shackle and nylon sleeve for over 6 years with no problems, and although we may not see the same loads as the unrestricted boats it works perfectly fine as long as the sheave is a snug fit in the shackle.

 

Bobbo.

Link to post
Share on other sites

By way of explanation.

 

We have seen a few cases where the Mylaska type of homemade shackle sheave thingy has fallen over.

this can happen when the halyard is loose, I used the example of reefing in 40 knots, sometimes you ease the halyard but

the head is hard to pull down.

In that case its quite possible for the halyard to find its way into even a small gap between the shackle and the sheave.

 

The second problem is if you over hoist the halyard and the sheave hits the underside of the head crane. Over time this can cause the sheave to break and if that should happen it is likely to damage your halyard rope.

 

I know the above because I've personally seen it on a few occassions.

 

Most of the rigs we service have a Tylaska shackle at the head (or a similar product).

 

the advantages are:

Very light weight

The shackle can be pulled up very high getting your main up higher.

The shackle fits between the plates of the head crane.

No moving parts

Shackle pin is captive (so easier than fumbling around with the sheave in your hand as you pass the shackle through the head of the main, then reassemble the sheave)

 

I guess though at the end of the day they are made of alloy (very bad) and they cost $100 so won't be for everyone.

Link to post
Share on other sites

Fair enough Tim. I see wichard do a similar concept to the tylaska too. No idea on cost.

 

I guess though at the end of the day they are made of alloy

 

Not a problem for most people... :lol:

 

and they cost $100 so won't be for everyone.

 

A problem for lots of people

Halyard.JPG

Link to post
Share on other sites

The other option is the middle sized Wichard halyard shackle, and the medium sized low friction alloy thimble fit well together. Its a poor mans Tylaska, and what we are running on Slipstream (Y88) and Creepy Crawler at the moment. It works very well and a whole lot cheaper!! You just slightly bend the shackle open a touch to get the thimble in, Then close it up tight around it.

Image006.jpg

Image004.jpg

Image003.jpg

Link to post
Share on other sites

Some nice Kiwi No 8 action going on here.

Marshy's has the edge on the rest, very clever :thumbup:

 

That would be only a 'small size' thimble though.

 

As a FYI - we just tested a few of the chinese made halyard shackles that look like those. Came up a lot better than expected and we think perfectly fine for anyone one knot pushing load boundaries hard who also has a smaller sized wallet. The numbers were well above what 99% would expect to need and knot at all far off the brand name versions, many of which are probably made in the same factory anyway :?

Link to post
Share on other sites

We had a "mylaska" type thing on GDT untill it jammed just above the hounds dropping the main in 25 knots of breeze. After Marshy shimmied up the rig and spend quite a while hanging on for his life trying to free it while we were in a fairly hairy spot near the harbour bridge Marshy replaced it with something far far better!!!

 

 

Hey guys, you are cheating!

Don't you know we are supposed to buy as much brand name HW as possible?

:-)

 

But then I am also a sinner. I am known to have built my own blocks and I am not sure ball bearing blocks

are really superior to plain bearing bocks.

 

http://hem.bredband.net/b262106/Boat/Blockfriction.pdf

 

/Martin

interesting read Martin. One thing that I was wondering, perhaps the BB blocks would show a better reading when under a higher load ( i.e. near max working load?) and also perhaps when they are running at high speed? all your tests were low speed tests

 

I would be interested to see how a proper block like the ser 57 Black Magic Harken with needle BB would fair in the tests.

Link to post
Share on other sites

I remember that now Sam. And i certainly wouldnt reccomend it again! They go so well until they go bad! Murphies law it goes bad on the windy day! And that was one dodgy mission to get the main down...

Link to post
Share on other sites

we use to use a tylaska but we found we were breaking halyards every few weeks. they get real hot on a large hoist and were burning the halyards.

Link to post
Share on other sites
we use to use a tylaska but we found we were breaking halyards every few weeks. they get real hot on a large hoist and were burning the halyards.

 

What size boat?

Link to post
Share on other sites

interesting read Martin. One thing that I was wondering, perhaps the BB blocks would show a better reading when under a higher load ( i.e. near max working load?) and also perhaps when they are running at high speed? all your tests were low speed tests

 

I would be interested to see how a proper block like the ser 57 Black Magic Harken with needle BB would fair in the tests.

Regarding higher load: That is on the wish list but my test set up is not up to it. The loads I have reached covers what you have on the line of a hand-operated tackle (as opposed to winch-operated).

 

Regarding the Harken blocks you mention: Please send some and I will test this winter.

:-)

 

But if internal friction in the line dominates, how much improvement can you get from the bearing of the block?

 

Note on Harken: Not all Harken blocks are ball bearing blocks. I have good experience with their wire blocks using them for my main sheet. They are plain bearing blocks, something I just found out reading their data sheet. The balls are only there to center the sheave between the side plates.

 

/Martin

Link to post
Share on other sites

heres another version of the 2:1 haliyard shackle, retailing for around $99inc

I think the safe working load is 1500kg

takes up to 8mm rope I think.

Weighs 35 grams

Marshys weighs 125 grams

pm me for details on where to purchase one

 

you could also use it for other high load applications

DSC00090.JPG

Link to post
Share on other sites

SWL 1500kg on that shackle?? I very much doubt that unless that round thimble is about 80mm or more OD.

 

Very clever thinking though, I do like it :thumbup:

Link to post
Share on other sites
heres another version of the 2:1 haliyard shackle, retailing for around $99inc

I think the safe working load is 1500kg

takes up to 8mm rope I think.

Weighs 35 grams

Marshys weighs 125 grams

pm me for details on where to purchase one

 

you could also use it for other high load applications

 

What is the size of the shackle pin Sam ?

 

You need at least an 8mm pin in 17-4 to claim SWL of 1500 kg.

 

Normal s/s pin of 10mm has SWL of 1520 kg.

 

 

FYI The tylaska H5 has a SWL of 1136kg, a pin diam of 6.6mm, and weighs 36.9 gms

Link to post
Share on other sites

Archived

This topic is now archived and is closed to further replies.


×
×
  • Create New...