Spinnaker Spiro or Mast Hoop positioning

15/04/2017 12:00:57
Gareth Griffiths NHRC
Hi guys 

I noticed yesterday whilst walking past the now quite large collection of Merlins we have at lymington how the height position of the inboard spin pole end attachment to the mast varies quite considerably on different boats.

In the fleet there are four seldon masts one skinny one all the same height, a Paragon P&B slightly lower, a superstars basic similar to paragon and my Chipstow which is considerably lower.

Any thoughts on why? Or recommended heights etc?

15/04/2017 18:34:24
Martin Smith
Some at Blithfield have had two, it depends on how tall or short your crew is and how high they can reach!
So we have had masts with child height rings and adult one higher up.
Recommended height has to be what works best for your crew. 

15/04/2017 20:10:49
Chris Martin
With the long poles it really isnt all that important - what is as martin says is that your crew can reach it.
 
With the - now very - old 6 foot poles to maximise length people used to position the eye high enough for the pole to sit virtually flat.
 
So some variance is to be expected, but there is no "fast" height.

15/04/2017 23:04:15
Andrew M
For years I had 2 rings on the mast and reinstated the lower one for Salcombe last year (it had broken 4 years or so previously).  If you look at the geometry you lose a matter of less than 2 inches from dropping the inboard end by even a foot or so.  With the conventional 2 pole system shorter crews will often have trouble with the above-the-shoulder strength required to get the pole clipped on to a high ring and if it's a bit breezy and crowded by a gybe mark then having your crew fiddling about near the mast is not a very good idea.  Incidentally the other issue I have discovered over the years is that Vectran will shrink, and if the downhauls have got a bit short you only find out when it's honking a bit, you have a fair amount of rake on and the breeze is flapping the kite about to help the job of getting the pole out on the new gybe.

16/04/2017 07:58:16
Gareth Griffiths NHRC
Andrew avoid veteran at all costs it is very volatile rope and disintegrates too quickly.

Cheers for your thoughts chaps

It was an observation. Will be going aspire at some point soon. Maybe in the next few weeks.

As always your time thoughts and musings are greatly appreciated

16/04/2017 19:20:55
Chris Martin
All 12 strand rope shrinks, especially if its pulled round a sharp corner or subjected to mechanical wear. I think that pole vangs on a merlin are probably one of the most testing applications for rope out there.
 
Im actually considering a return to vectran in this role, though i think my current stretch issues are actually in the polyester control line rather than the pole vang itself - i'll try changing this first. I used vectran for many years with no issues in the past, but I sail inland, wash my boat and it lives in the garage so UV and salt water issues (Which are real problems) didnt/wont bother me too much and pole vangs only last a year anyway. The trouble with vectran is it will break with little warning once it starts to deteriorate. 

16/04/2017 21:17:40
Gareth Griffiths NHRC
Chris you are right about vectran it breaks suddenly after showing little wear.

Ten years ago many race yachts used vectran for their steering strops to poor effect.

When the trend moved to change these to dyneema or wire I unspliced many vectran lengths to find that the bury of the splices were like tissue paper. You could tear it apart easily.

For the snodger on the merlins I have rigged I use a 2.5 mm SK99 dyneema. Spliced with a decent length bury I have had no stretch issues.

Dyneema deals well with UV exposure with salt and is better at dealing with corners.

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