29/10/2009 12:13:30
Dave 3633
I need to replace my puller:

Rather than have a wire strop made up, i thought i would use some dyneema/vectran but what thickness should i use? Its for SS mast if that makes much diffeence?


29/10/2009 12:29:59
Fairly certain mine is 4mm, which appears to be the Winder standard.

29/10/2009 13:09:04
Dave 3633
Thanks, Is that D12 or V12 ?

29/10/2009 13:44:50
It's grey which, by the looks of the Marlow site, makes it 'V'.

29/10/2009 13:52:19
Looking at the pictures of Tom Stewart's boat in the 'rigging guide', it looks like he has used 3mm V12. The thinner stuff has a SWL(?) of about a tonne so should be fine. Think of the windage you could save !!

29/10/2009 17:14:13
Safe Working Load?

29/10/2009 17:32:52
I suppose I should have said 'breaking strain'! Happy now?

29/10/2009 20:31:18
Ben 3634
3mm Vectran or Dyneema.

29/10/2009 21:11:08
Oops, I took the question mark after SWL as an invitation to explain the abreviation. To be really picky SWL is quite different to breaking strain.

I'll get my coat......

29/10/2009 21:57:23
Charlie Campion
SWL = Safe Working Load

Back in the days before computers, when quality control was less exacting, formulea simpler & ships had derricks Safe Working Load was taken to be 1/6th of Breaking Strain...

29/10/2009 22:13:59
and of course breaking strain and SWL are totaly different: one is a load (mass or force) and  proportion of tensile strength, the other is how far it stretches before it breaks.

30/10/2009 08:48:10
Andrew M
There was a time when you could just post a question on a forum and get an answer, though not on this one, where you can fortunately rely on the initial question being subverted into a discussion of Danish phrases, engineering terms or what happened in the class in the 1950's

30/10/2009 09:03:35
Perhaps I should have refered to TPAWIRIMGP, then everybody would have realised what I was talking about. Oh, sorry! You don't know how to define TPAWIRIMGP? Silly me; it's 'The Point At Which, I Reckon, It Might Go Ping'.

30/10/2009 09:33:08
Andrew M
To give a sensible answer, 3mm Vectran or Dyneema is fine, the plaited variety BUT after a certain amount of time the UV will cause degradation and that will weaken it as will the chafing of the jib sheets and eventually it will reach pinging point, inevitably as you power up the kite on a tight and windy reach.  The bang as it goes is quite impressive, we thought we must have lost the mast but as it is a venerable Superspar from the 1st batch of carbon technology it is fortunately pretty bulletproof.  I have resolved to replace annually since.

30/10/2009 16:53:46
Thanks for the clarification on the 'technical' terms.  I had been told by my wife that safe working load was the amount of shopping I can bring in from the car in one trip, and that breaking strain is the point our relationship will reach when I want to go sailing all weekend. I can confirm that this is often the point at which it might also go ping, so thanks to Alistair for the confirmation on this point.

30/10/2009 17:24:13
Interestingly Dyneema is stronger than the equivalent sized vectran!!

I'll also get my coat!

30/10/2009 17:57:22
If the puller goes ping, what goes pong and how soon after the ping will the pong follow.

30/10/2009 19:06:58
A Einstein
If ze co-efficient of ping iz multiplied by ze square on ze hypoteneuse of ze pong elemental retardational constant, zen we have ze ping:pong ratio.

I expect old colon-bracketty bloke will tell uzz zat ve are all wrong! Vot duz he know viz his name made up of punctuation?!

03/11/2009 08:17:21
You don want the pull to be stronger that the breaking point of the desk pully pulling up the deck, do you? Whats more expensive - deck? Mast?

03/11/2009 08:18:56
should have said - deck? deck & mast?

03/11/2009 09:52:17
Andrew M
The force on the deck sheave will be horizontal and it's difficult to break the deck in that plane, the mast will go first in a wipeout particularly one of those fragile expensive Chipstow twigs.  Another 3 bust at Ranelagh I see.  Just as well I have had my insurance premium demand for this year!

03/11/2009 10:43:09
Ben 3634
Andrew, you're raising an interesting issue for the class here: what is the breaking point of an insurance company?Or rather how many claims will it take before insurance companies place restrictions on our sailing because of repeated claims?

03/11/2009 10:53:27
Chris m
I wonder if people overload their mast in strong winds. Leeward shroud just tight is a lot of tension in 35mph of wind!

03/11/2009 12:20:29
Has anybody done any analysis of mast breakages? Point of breakage? Age of mast? Hit the bottom? etc. Every time it blows much more than a F4 there seems to be a report of a broken mast.

03/11/2009 12:50:31
Chris M
I think all of the ones broken at Whitstable hit the bottom. At salcobme it was very gusty, wind hits boat, boat nosedives and the wind pretty much blows the rig off the boat. I'd imaibne Ranelagh was similar.

03/11/2009 13:23:10
All 3 at Ranelagh hit the bottom - capsize + wind over tide + shallow + sticky clay on river bed = goodbye mast!
2 of the masts were aluminium. Ours was a Proctor carbon supplied on 3599 when new. It was broken for the first time in the last race at Salcombe this year (caught on moored rigging) and expertly repaired by Chipstow (the 2 new breaks were nowhere near the repair).
Don't be put off sailing in the excellent river series though. I have been sailing nearly every week on the river for the last 14 years and never seen this happen before.

03/11/2009 16:47:44
Measurement Man
The latest slant on this thread is an interesting one, but I would be surprised if breakages were significantly higher now than they were when the M1 was the twig of choice - they seemed to collapse with regularity.  I would also be surprised if Merlins were picked out by the insurers for special treatment; I was ARO at the the Tide Ride this year, and was around for the 200/400 meeting at HISC, and on both occasions there were many masts reverting into kit form - both Ali and carbon - with ne'er a Merlin in sight...


03/11/2009 16:54:04
Chris M
I think it's just unfortunate that the two major events in the class have had a lot of breakages this year. At salcombe this was due to the extreme nature of the wind and at Whitstable due to a windy day and being a relatively shallow venue. At Looe last year how many masts broke? 

I don't think that carbon masts are any more fragile than the ally ones, they have certainly come a long way since the bad old days of the origional Proctor carbons!

03/11/2009 17:05:13
John 1201
I don't think it is true to say that all the mast at Whitstable broke because they hit the bottom.
Approximately half broke because of gear failure as with Salcombe.
It is just as easy for an Ali mast or a Carbon mast to break when they hit the bottom.
If you are careful and a bit lucky you will get away with it.

03/11/2009 17:38:15
Chris M
I do, I was there.

I don't think i spoke to anyone who hadn't got the mast stuck in the bottom. I will stand corrected if necessary.

03/11/2009 18:12:07
Andrew M
I have had 2 masts break in 14 years one hit the bottom at Chichester and the top bit is still there along with the top panel of the mainsail, the other was when a shroud broke at Ranelagh.  Both were alloy.  I wouldn't mind breaking a mast to replace with a more modern alternative but I can't seem to do it.

03/11/2009 22:28:51
Dave Lee
And given Andrew's track record with carbon tiller extensions that's really quite remarkable......sorry Andrew, couldn't resist :)

03/11/2009 22:44:53
John 1201
I was there at Whitstable, as well and definately half the mast that broke were gear failure.

04/11/2009 09:14:57
Andrew M
OK Dave, but I haven't broken another one since that memorable day!!  Now have on Tony Blackmore's recommendation a big thick carbon thing that has resisted me falling on it admirably.  Maybe if I fell on the mast in a capsize?

04/11/2009 11:58:33
Interesting fact, A 49er belonging to a un-named relative of mine, with a ally bottom mast and carbon top mast, had a bit of an accident this summer. The ally mast section broke, the ally spreaders broke, the carbon bits were all fine. By the way, the bill for repairs were probably 3 times the cost of a similar style crunch up on a merlin, (the insurance is about twice and so is the excess)

04/11/2009 14:36:42
Interested in the points about gear breaking and specifying rope diameters for the puller. 
Seems to me that we need to look less at the breaking point of ropes and more at the actual working range.

According to the Marlow web site, 4mm Excel D12 stretches by 2% at 20% of its break point of 2056KG, V12 stretches by 1.6% at 20% of its break point 1678KG.
I believe they both break at around 6% elongation.
So Vectran stretches marginally less but has a lower break point.
As a rule of thumb they suggest 20-30% of it's breaking KG would be a good working range for applications to minimise stretch and reccomend not to exceed 50% of it's breakload.

So using 4mm V12 at 25% of the breaking point would be useful in applications with a weight / pull of around 420kg going upto 840kg for occasional maximum load.

Trouble is, there are so many factors involved in the forces acting on the mast / puller I can't find out what it needs to stand up to, and I have asked a few people who ought to know!Any ideas?

Lastly, they say it retains 50% strength after 2.5 years of UV exposure - so replace often!

The marlow site has spec sheets to view/download and here's a link to a site comparing ropes from different manufacturers and hope it brings someone some peace of mind!

04/11/2009 16:20:19
Andrew M
The main force on the puller is opposing the push from the spinny pole and Newton therefore suggests about the same as the tension in the guy.  Powered up on a tight reach that is likely to be up to 150Kg do we think, about twice what I can pull in a straight 2-armed yank on it.  But if the mast has actually gone out of column and begun to invert there could be on occasion another 50Kg max to pull it back into line, certainly won't be much more.  Who here has actually broken a puller that was not old and a bit frayed, and how?

04/11/2009 18:45:41
A. Cad
I once pulled something that was broken, old and frayed...does that count?

07/11/2009 18:59:22
This is a link a the Speeds web site that has a description of the Holt Pro Line 3mm, which would be ideal for a puller.

http://shop.speedsails.co.uk/index.asp?selection=detailed&uid=453101885&itemtitle=Ultra Line 3mm


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