MERLIN ROCKET FORUM

Topic : One string system length of travel of Special block

"Hi Rocketeers \r\n\r\nDoes anyone have measurements... Or ... would anyone be kind enough to measure the length of travel on their special block, the back to back one that comprises the one string system.\r\n\r\nI would be very very keen to know what the the difference between full rake and 0 is from your mast tip to a position. (I know transoms are all different but the difference between one extreme and the other will be regular or at least comparable).\r\n\r\nI would also be hugely keen to know what the difference in length on your forestay, shrouds and lowers are between full rake and no rake...\r\n\r\nIf anyone has this all written down I am sure it will be of huge use to not just myself but many bimblers, jiggers and boat breakers out there."



Posted: 23/08/2013 16:36:04
By: Gareth Griffiths Notting Hill Rigging Co
"If no one has any of these details but would be kind enough to measure them... Be great to see the difference between a variety of boats, compare notes on each others system travel etc...\r\n\r\nMiles especially, with the canter lever system... Andy Hay who has the 8:1 in the king post system, vs the one design Guy Winder stuff....!!!\r\n\r\nI hope these generate some interest and that we can get a few measurements written down.\r\n\r\nCheers"



Posted: 23/08/2013 16:36:04
By: Gareth Griffiths Notting Hill Rigging Co
"Just been checking my measurements on the Niane design I have... I have 460mm from the deck down to the Hog at the base of the King post...\r\n\r\nI have a high Hog, it carries straight through from the level of the centreboard case."



Posted: 23/08/2013 16:36:04
By: Gareth Griffiths Notting Hill Rigging Co
Also has anyone got readings from No rig tension to full rig tension with a loos gauge or load cell...?



Posted: 23/08/2013 16:36:04
By: Gareth Griffiths Notting Hill Rigging Co
"Thanks Chris and KM\r\n\r\nGreat reading and very helpful stuff.\r\n\r\nThe original rig tension, not one-string, ran forwards from the mast frame bulkhead to the bow along the top of the forward tank and the tensioning was down the middle leading back to the Kingpost.\r\n\r\nThere is plenty of room here to set the one string system with plenty of room for travel and i am sure that this part of the boat is strong enough to take the loads as it was designed to do so originally.\r\n\r\nWhat got me thinking was having re-roped Terabyte for Andy recently, it was important to range the controls to the points most used. e.g. you need to be able to easily connect and disconnect the shrouds lowers and jib halyard when rigging up, but you also need to be able to get enough travel to get the maximum rig tension needed.\r\n\r\nI am at the point with my boat where I am about to trial rig the rake and tensioning system and trying to alleviate too much trial and error.\r\n\r\nTo rig Terabyte I constructed several strops with adjustable splices to get the rig both straight and also pulling the right bits at the right time.\r\n\r\nThe system for moving rake with one string is well noted on this forum, but the lengths of strops controlling each part vary from one canterbury tales to another... My boat is a one-off that is similar to a Tales but cant be rigged in the same way."



Posted: 23/08/2013 16:36:04
By: Gareth Griffiths Notting Hill Rigging Co
"people don't set the boat up to a specific rig tension and go sailing, it's dynamically adjusted as we go around the course to keep the leeward shroud tight.\r\n\r\nI suspect we sail with far less rig tension than most classes, as kieron says I don't think i reach 27 on the loos gauge (400lb/180kg) except in seriously strong winds.\r\n\r\nTravel on the rig control car: your limiting factor is the distance between your bottom block attachment points and the underside of the deck. You want the blocks as low as possible at the bottom of the boat to maximise travel. \r\n\r\nIf for any reason you can't get the blocks to the bottom of the boat some improvisation is required to maximise your rake range:\r\n\r\n1) The easiest and most elegant solution is to have a double loop at the end of the jib halyard. Light winds starts bolt upright, strong winds at approx 12"" rake measured off the gooseneck/main halyard with the transom vertical. The disadvantage is that if the conditions change while out on the water its not that easy/safe to alter the boat!\r\n\r\n2) On 3402 a frame was constructed out of titanium to effectively elevate the bottom of the deck and move the rake travel above the foredeck. The way this boat was constructed restricted the rake travel, even though the deck hump is very high. The boat was originally case stepped so going below the centreboard case was not an option. This works very well, and if anything there is more travel than you need. The disadvantages with this are aesthetics, and it makes it a little more awkward step the mast. But if the boat was case stepped originally this is the way to do it, just don't go quite as high with the frame - this one is about 6 inches we'd have got away with 3 on that boat IMO because of the deck hump, but Rob also wanted the mast to be capable of leaning forwards. You'd need to measure up 3450 and compare it to the hog/under deck travel on a winder.\r\n\r\nThe final limiting factor is where the jib halyard exits the mast."



Posted: 28/12/2013 17:59:06
By: Chris M
Hi Miles.\r\n\r\nYes having done a few measurements 7:1 is about right. But I am more interested in the lengths of travel and the loading...\r\n\r\nHow much rig tension is being applied and what does it take to achieve that tension.



Posted: 24/02/2014 23:06:54
By: Gareth Griffiths
Hi \r\n\r\nThanks for the replies and the info. All good stuff.\r\n\r\nHas anyone measured their rig tension with a loos gauge to find out what tension they are using at full and minimum rig tension?



Posted: 24/02/2014 23:06:54
By: Gareth Griffiths
"Gareth, 3646 has a lever movement ratio of 7:1 between tail end of jib halyard (on a 2:1) and the shroud movement through deck i.e. halyard hook moves 14 inches for every 2 inch movement of  the shrouds.\r\n\r\nThis is really all you have to measure and then work out purchases etc. accordingly."



Posted: 19/04/2014 17:32:02
By: Miles 3646
"Hi Gareth, apologies if this may be telling you stuff you already know, but on a Winder the strop from the one string block goes up through the foredeck and connects to the jib wire by a hook, so above the deck there's a thimble (usually, or a dyneema splice)and a hook.  Supposing the hook and thimble were as low as possible, the distance from the top of the hook to where the wire disappears into the mast is the full  range of rake adjustment which is available - you may not need all of it, and at some point your boom may well bottom out on your hoop if you're using one, especially when combined with a hefty amount of kicker.  Where it starts at the bottom of the range will be determined by your mast upright position (zero) which in turn will depend on the length of your jib wire and 2:1 strop if you're using one. The amount of movement below the foredeck for the one string block is equal to the amount of movement you need above the deck.  The distance between the foredeck and your goose neck may be shorter than on a CT due to the lofted foredeck so you may have less room for rake adjustment and therefore need less room on the kingpost for vertical adjustment.  I would guess that the best thing to do is to get the mast calibrated with the lowest possible zero point by tweaking your jib wire and strop, and work back from there - assuming that your kingpost height isn't infinite your range of adjustment and length of the strop from the one string block will just have to be whatever your dimensions allow it to be. \r\n\r\nThe limit of your rig tension may well be whatever the boat will stand before it folds. The rig tension for set up, according to Taxi's tuning guide is 27 on a loos gauge. That was more than we usually sail with but probably not the most we've ever had to put on to stop the leeward shroud shaking. I think around 20 is our normal 'both sitting out' setting but we just put on whatever the conditions dictate and don't often thing in terms of absolute values.\r\n\r\nHope some of that helps....."



Posted: 20/04/2014 10:39:18
By: K.M.
"Hi Gareth\r\n\r\nlength of travel 14 to 16 inches, tension is 12:1 (6:1 onto jib halyard)"



Posted: 20/04/2014 10:58:59
By: Miles
Hi guys

Just bimbling today...

So in the various tuning guides the experts say about having the travel of your rake from fwd of upright to the other extremity which is approximately the main halyard sitting 12inches from the mast at right angles to the gooseneck.

And I was wondering about the forward of upright... Does anyone use it?

I guess it is for downwind use.

If so how much...?


Posted: 27/11/2014 18:20:04
By: Gareth Griffiths NHRC
Gareth Steppenwolf and Wuthering Heights rake can be as much as 34" from vertical  (halyard behind gooseneck)
 
The mast automatically goes just forward of vertical (just) off wind, unless you set it not to.
 
There are lots of photos in the gallery on this site of boats with mast vertical or forward downwind, 


Posted: 27/11/2014 22:49:22
By: Miles
Gareth Steppenwolf and Wuthering Heights rake can be as much as 34" from vertical  (halyard behind gooseneck)
 
The mast automatically goes just forward of vertical (just) off wind, unless you set it not to.
 
There are lots of photos in the gallery on this site of boats with mast vertical or forward downwind, 


Posted: 27/11/2014 22:54:33
By: Miles
Cheers miles

34" is a lot of rake.

A hell of a lot. I have enough travel to do that I'll see how it looks.

Really happy with the whole system, spliced up all the strops plugged it all in and it measured straight first time job halyard length was spot on too.

Considering the quantity of variables, 1mm here or there could off set by up to 10mm elsewhere I was pretty impressed.

All that one design string production for the Volvo boats this year has brought an almost scientific element into the traditionally "rough as guts" black art of rigging boats.


Posted: 28/11/2014 11:40:07
By: Gareth Griffiths NHRC
Your issue Gareth may well be with space for the various blocks to run, particularly betweeen top of bow tank & underside of deck on the kingpost.  Heaven Sent has the standard Turner set-up of the era and your boat would probably have been identical.  I can get 20" of rake, maybe a little more on max but the limit is imposed by the boom going block to block on the hoop.  Downwind at my end of the fleet when it is howling the rake I worry about is keeping the thing pointing at the sky and don't touch the rake, when it is light I will pull the mast vertical & take off almost all the rig tension.  Are you afloat yet?

 

Andrew


Posted: 28/11/2014 14:24:51
By:
PS in fact on max I am well over 20" I was thinking 20" of travel from my light wind upwind setting.


Posted: 28/11/2014 14:27:53
By:
Hi guys

I made two adjustable strops that are the ones that 2:1 through the special block. I can now adjust the amount of rake I want.

I guess sail trailing it will make the final decision. I'll st it up for 20"s tomorrow and give it a go.

Cheers for all the input..


Posted: 28/11/2014 17:54:01
By: Gareth Griffiths NHRC
All working well. Really happy.

I had a look at Richard Domony's Winder this morning and my strop lengths, though laid out differently, (Special block runs for-aft on the bouyancy tank, rather than in the king post), all seem to be about the same length. Can get a huge amount of rake... Very happy.



Posted: 30/11/2014 20:34:28
By: Gareth Griffiths NHRC
20" of rake... hmm... tugs beard...
 
I know its a bigger boat, but on the FD we had four eyelets at the genoa clew, one above the other, for the sheets to attach to; you'd decide which clew the conditions called for and then rake the rig to keep the slot about right.  Going from clew 1 (lowest) to clew 4 (highest, reserved for hurricane force and above!), the tip of the mast would move back 5ft...   ...and the board pivot point would have to move back in the slot to keep the weather helm from ripping your arm out of its socket.  Happy days!


Posted: 04/12/2014 22:56:08
By: Derik Palmer
The clew on a Merlins jib is pretty high cut. But the turning blocks need to be moved or sheeting changed when you add or remove rake.


Posted: 05/12/2014 12:43:14
By: Gareth Griffiths NHRC
Though fortunately as you tip the mast back you are increasing twist in the jib matching your flatter more twisted main.


Posted: 05/12/2014 14:04:20
By:
Hi Andrew

Yes that's true. I thought about incorporating the fairleads into the one string adjustment, but have opted for independent car adjustment instead.


Posted: 08/12/2014 17:29:12
By: Gareth Griffiths NHRC

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