I have been looking at earlier posts (see: http://www.merlinrocket.co.uk/forum/main/topic.asp?topic=2699 and http://www.merlinrocket.co.uk/forum/main/topic.asp?topic=2085) around the topic of self-launching / self recovering poles.

There seems to be an opinion that the stanadard twin pole manual set-up used by all (?) the top guys is better. With the suggestion that having a second, lower, D-ring on the front of the mast is very useful for people who may be shorter or weaker in the arms than the normal Merlin crews.
Is there a standard height for the normal D-ring?
Is there a standard / recommended height for the lower D-ring.
If using the lower ring, would you change the elastic tidy-aways the poles run on (less gravity working for you)?

If the auto-recovery poles are led back along the same guiding elastic that is used for the normal manual poles, is there still a problem with crew decapitation?
(I can't quite see how the helm gets hit: Surely they are sitting to windward normally?).

Thanks, Chris

I currently sail with No 2 son (12 and 5ft), and have two rings on the mast.  The lower one is just above the puller attachment point and c. 250mm below the normal ring height.  

With the snodger arrangments (downhaul tensioner) that modern Merlins have, he has litle problem getting the pole on the upper ring on running or broad reaching legs (usually standing on the top of the centre board case), but really struggles on reach to reach gybes or hoists, when he uses the lower ring.

What ring height you use has no impact on the elastics, but it is better to select one ring and always use it in a particular race because the effective length of the poles (perpendicular to the mast) is shorter when they are used on the lower ring.  This affects such things as up haul adjustment, and stopper knot positions in sheets (if you use them) to prevent the poles from bending around the jib luff.

Sailing with a very light weight crew (i.e. around 5 stone in our case) brings its own challenges in a Merlin, and you soon learn such things as how uncomfortable light winds sailing can be, and how essential an easy to dump kicker is in those windy reaches (thanks for the tip, Dave Fowler).  

More often than not in breeze, we sail tight to beam reaches as fast with two sails as we would with three, given the limited strength in his little arms (I'm such a cruel parent...).  The runs are still fun with a kite tho.

Regarding the elastic, the only force on the pole with the conventional system is upwards. The only risk if injury (It does happen) is if your crew is a little overzealous with the the throw back, so it does pay to be nice to them just before a gybe or drop!

The first wide merlin I had had a system of elastic which ran through the boom and physically
 pulled the pole back with no guide. This was dangerous and quickly abandoned.

What about (2 questions in one post!):
Keeping the elastic guides that exist on the current manual poles, and add a retrieval elastic to pull the pole back? The guides should mean not much extra danger compared to the current boats, but the elastic retrieval will allow the launch the pole by pulling a rope idea.

OR: keeping the idea of a pole launching rope (its not a youngster who will be crewing, but someone at the other end of the age-range! Arm pushing muscles have been removed by various surgeons: pulling muscles are still good); but instead of having a retrieval elastic, have a manual retrieval and throw back? There would need to be a way of ensuring the launch rope runs free enough (elastic again!?) to allow the pole to be manually passed back down the boom, but it would reduce the sudden "release the rope and watch-out" of the elastic pull back.

You don't need retreival elastic. The crew just gives it a "nudge" to clear the mainsheet.

Launch ropes have been used in the past, but most find then unnecessery

The great thing about sailing a Merlin is you can try whatever arrangement you want for your spinny pole.  Poles that launch on a bit of string have been tried by several people and it may work well for you with a particular crew on a particular bit of water.  The consensus on this forum is that in general nothing else is as quick or snag-free as the standard twin pole system and that bits of elastic to bring the pole back in are not neccessary and may be dangerous.  But give it a try, the simplest method I have seen has a pair of sheaves mounted at the pole ring height on the mast and string going to a turning block and cleat on the aft face of the foredeck by the mast.  Keep the existing elastic for the pole to run on, the end of the string goes to the end of the pole, pull for up, uncleat and probably pull the pole a bit for down.  Just be careful about drilling too many holes in particularly a carbon mast close to the gooseneck and lowers.

I've seen both Fireballs and Mirrors at Brightlingsea using the "pull the rope tolaunch" method which requires a different mast fitting, something like a ball and socket. Has anyone tried this?

The Fireballs tend to use a single pole, rather than twin poles. But they are restricted to an alloy pole (thicker / heavier). How they get away with injuries with their lower boom and narrower cockpit (less room for the crew / helm to avoid the flying pole) I don't know!

I was wondering whether this (Merlin priced!) fitting would be good: 
http://shop.pinbax.com/index.asp?selection=detailed&uid=35475
But the idea of hanging a couple of ball-bearing sheaves from the current ring sounds much cheaper (and easily adaptable back to standard!). BUT there must be a reason why someone felt the need to develop the fitting, so there must be some advantages to it.

My old smokers from the 70's, had a rope launch system. It worked really well, the main advantage was that the crew did not need to move right up to the mast to attach the pole, keeping crew weight back in the boat (not burying the nose into a wave). This system does tend to knock the mast around a bit by the bracket, which is why I have assumed that it is not used on carbon spars. Would be interested if anyone knows about this. With regards to the pole being released back to the boom, care did need to be taken to ensure pole did not smack (normally the helm) someone in the head. This system sped launching and retreval up for most crews. However the guys at the top generally prefered the manual system. The pole had an eye at the back end which shock cord ran through. the shock cord was attached to the mast about 6 - 8 inches above the pole bracket, and ran back to the end of the boom, the pole only slid on the shock cord, gravity pulled it back. The front end of the pole was as the twin system is now.

One issue with blocks attached to the ring, is that the pole will not pull out to it's full extension. Also with part of thepoles down the side of the mast these can be broken if caught, they will also wear against the mast. If legal the P&B bracket would be best option.

Having once crewed for Danno when he used self launching poles (the system described by Andrew M), I can only say it was damned hard work hauling on the out-haul to get the pole fully out (even with a 2:1 purchase). Furthermore, although the crew could control the rate at which the elastics pulled the pole back along the boom, if you did let go, ther poles shot back at high speed and at eye height.

The twin carbon pole system currently refined on Merlins, when set up to the standard arrangement is really easy to use and does not require excessive muscles.  

Because, on release, the poles roll down the elastic to the boom end, there is not the same spear-like tendency in them, although I do always stand well clear.
 
However, the key is timing the gybe, and steering through a smooth rounding at the mark which allows the crew enough time to gybe the pole, and get control of the new sheet before hardening up onto the reach and fully loading up the kite.  Under those circumstances, the loads on the pole are not as great - always assuming that the helm has released the snodger (downhaul tensioner) of course...

^^ and this was probably with 5ft poles!^^