Adjustable raking systems
Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=13713
Printed Date: 28 Jun 25 at 10:31pm
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: Adjustable raking systems
Posted By: iGRF
Subject: Adjustable raking systems
Date Posted: 17 Nov 20 at 9:56am
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One for the technically minded this.
I'd like a single string raking system that adjusts the lowers simultaneously. I'm sure I've seen it in Merlin World and wonder if anyone has some sketches as to how the pulleys line up. My second question is, insteaad of raking the mast back top down has anyone ever come across anyone sliding the bottom of the mast back and forth windsrf longboard racing style, pivoting around the top spreader shrouds? (Obviously the lowers would have to adjust in concert also) ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Replies:
Posted By: davidyacht
Date Posted: 17 Nov 20 at 10:50am
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You probably should delve in the various Merlin Rocket forums, since I believe that there are two types of Merlin one string systems. Look on the main website and also the Merlin Revival Facebook pages. Unless you are a consummate boat bimbler you might look to get one of the Merlin gurus sort it for you. Dick Batt had a ramp system for the mast foot, I think on Danger Bat. This might be less complex. I suspect that you could achieve 90% of this by having a decent forestay tensioning system and a decent and powerful shroud tensioning system, and ensuring that these are carefully calibrated. In National 12s we simply dumped the shroud tension at the windward mark to allow the main to square off, and pulled it back on at the leeward mark. We had three windward rake settings marked off on he control line ... light, medium and windy. ------------- Happily living in the past |
Posted By: Gordon 1430
Date Posted: 17 Nov 20 at 10:53am
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HI Grf I had a 505 which had tracks on the shrouds so you could adjust them fore and aft in conjunction with raking the rig. You have a short length of tack on each gunnel with a car on top which the shrouds attach to and the cars have a control line to pull forward or aft. Mr Henshall might have some images of Grace which may have been one of the first with this system. Good Luck Gordon ------------- Gordon Phantom 1430 |
Posted By: davidyacht
Date Posted: 17 Nov 20 at 10:56am
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Grace ... special boat ------------- Happily living in the past |
Posted By: Rupert
Date Posted: 17 Nov 20 at 11:36am
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A moving mast foot pivoting round the hounds will rake the mast but affect CofE rather differently. Good or bad I don't know. ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: H2
Date Posted: 17 Nov 20 at 11:51am
I think Tasar use a track at the shrouds too? ------------- H2 #115 (sold) H2 145 OK 2082 |
Posted By: Dougaldog
Date Posted: 17 Nov 20 at 12:05pm
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Mr Henshall has indeed pictures of the tracks and of the hydraulic shroud tensioners that were fitted at the time. In the end, Chris Haworth did this best...Merlins and 5o5s! However, with the ready availability of modern, low friction/high load blocks, the complication that the system introduced could be best handled with a merlin style one string. What is really needed here is the Jon Turner 'big wheel of love' but my gut feel is that the cost of doing this will drive the man of Kent into another rage - even a fairly bog-standard one-string system on a Merlin can gobble up a cool £1000+ in hardware and cordage. Sadly, the OP won't accept that this has been done before, albeit somewhat differently - who can forget that Jon Turner (one of our great innovators of things that work) had a system on Dark Star that allowed the rig to be heavily canted to windward. The $64,000 question though.... all that knowledge and expertise in one boat (Turner and Richard Parslow) and a fully functional system - get they didn't proceed to develop it further - which must beg the question...why not! Dougal ------------- Dougal H |
Posted By: Guests
Date Posted: 17 Nov 20 at 12:21pm
| Does your Fireblade need lowers, spreaders or even shrouds? Stick an OK or D Zero rig on it and have a sliding mast foot. Much easier, tidier and cheaper than a Merlin one string system. |
Posted By: iGRF
Date Posted: 17 Nov 20 at 12:47pm
Well, let's see them then? Why didn't they continue? Easy obvious answer to that. 
I came across this Supernova, it was allegedly the 2014 Nationals winner on display at some show or other, but it had some sort of system, wish I'd paid more attention and taken more pics.  ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: iGRF
Date Posted: 17 Nov 20 at 12:49pm
Well I assumed because I want to trapeze from it, it would need additional support, has anyone ever trap'd off an unstayed rig? Is it do-able? I agree getting rid of all that dross would be great but.... ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: Sam.Spoons
Date Posted: 17 Nov 20 at 12:51pm
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Raking the rig moves the CoE aft, useful to balance with a raked centreboard for stronger winds. Moving the foot of the mast while leaving the shrouds and forestay fixed (effectively pivoting the rig around the hounds) would move the CoE forward by a smaller amount. AFAICS there are both similarities and differences between the effect moving the mast foot has on windsurfer and dinghy rigs but in both cases it comes down to balancing the rig CoE to the hulls CoLR. On a Raceboard we move the mast foot aft offwind and retract the CB so the CoLR is wall back under the straps for minimal wetted/planing area, upwind we want as much WL as possible so move the rig forward about 18". ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Grumpycat
Date Posted: 17 Nov 20 at 1:45pm
Re the supersofa . I thought they only have adjustable forestay and lowers . So not really what your looking for . Sure mr spoons will put me right 
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Posted By: iGRF
Date Posted: 17 Nov 20 at 2:14pm
Yep, I know all that, what I don't know and am always weak with is pulley systems. And what the relationship should be for example between the fore stay and lowers/shrouds. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: Sam.Spoons
Date Posted: 17 Nov 20 at 2:26pm
I know you know all of that but I guess others will read this thread who don't. ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Sam.Spoons
Date Posted: 17 Nov 20 at 2:27pm
Dear aunty marge.... We probably need the input of a proper boat designer here But, that Supernova has, as you say, forestay and lowers adjustable, mine had just a forestay, I don't recall but I don't think they are allowed adjustable shrouds.
------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Rupert
Date Posted: 17 Nov 20 at 2:44pm
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There was an unstayed trapeze boat in the late 80s, called the Delta (or Delta4?). The mast was the size of a tree trunk at deck level. I'm sure with modern materials it could be done better, but I see all sorts of rig control problems.
Maybe a mast stump to spread the deck loadings? An adjustable one... ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: Old bloke
Date Posted: 17 Nov 20 at 3:23pm
| I think you need to work out what you want the lowers to do as you rake.If you want the tensions v the uppers to remain the same then the calculation is easy. If though you want more bend as you rake the I would experiment with holes and pins before trying anything clever/expensive. |
Posted By: H2
Date Posted: 17 Nov 20 at 4:10pm
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Do you really need lowers? The mast is deck stepped so the distance from gooseneck to the bottom of the mast is relatively short and could easily be made shorter if you were going to change the rig anyway. On the H2 there was lots of noise about lowers when the boat came out but we soon realised the rig did not need them for this same reason and we have an adjustable forestay to adjust rake / rig tension on the fly. Might be easier to get the boat up and started without them. ------------- H2 #115 (sold) H2 145 OK 2082 |
Posted By: iGRF
Date Posted: 17 Nov 20 at 5:36pm
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Correct me if I'm wrong here but I'm assuming other than use as a rigging aid the key use for lowers is to combat kicker induced lower mast bend. So, following that logic then the desire would be rake with neutral effect on lowers tension which mean as the rig rakes back they need their tension increased. Whereas, if the whole lot were sliding forward (ike someone mentioned back there with forestay sliders) in order to rake the mast fromthe foot then it would seem easier to have an arrangement where they all moved in concert, even leaving the forestay not necessarily needing much adjustment, hence my thinking... ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: Granite
Date Posted: 17 Nov 20 at 7:42pm
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The lower shrouds allow you to controll the lower mast bend. You are correct that they oppose the kicker, and their length and resting tension plays a role in how much the lower to mid mast will bend as the kicker is increased. For the sliding foot I am unsure exactly what you want to acheave and that will alter how you design it. If you want to move the foot fwd change the rake of the mast. Then I think it could be done with a track attached to the foot of the mast and bent to the same radius as the distance from the foot to the hounds. Provided the center of the circle of the track points at the hounds, you don't have spreaders or lowers then you should be able to move the foot without altering rig tension significantly. Adding lowers into the mix as a single string adjustment would be tricky as I don't think the relationship would be linear, so it would be hard to set the ratio. If on the other hand you want to move the mast back and fwd but keep the rake the same. Then I think you would need a Y shaped frame. This would be attached to the hull with tracks at the shrouds, forestay and mast foot. The whole frame would keep the alignment between each part and would slide back and fwd. You could build a raking tension sysem onto that frame provided all the anchor points for the various purchases were attached to the frame. The setup would be the same as for a normal raking system. I think it would be hard to do either without adding a lot of weight or requiring compromise in other areas. ------------- If it doesn't break it's too heavy; if it does it wasn't built right |
Posted By: Oatsandbeans
Date Posted: 17 Nov 20 at 8:05pm
| A commonly held misconception is that the mast foot position is an effective method of adjusting the mast rake and C of E position. It is not but it is really good at changing the mast bend. It works with the deck level or lowers to stiffen or bend the mast. |
Posted By: 423zero
Date Posted: 17 Nov 20 at 10:12pm
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Griff, do you want all this faff? Every time you change tack, you not only have to swap sides, pull on the mainsheet, slacken or tighten the Kicker, you then want to add adjustable on the fly, lowers, forestay, rake etc. ------------- Robert |
Posted By: iGRF
Date Posted: 17 Nov 20 at 10:19pm
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Well to further explain how I'm coming to the conclusion that moving the mast foot is preferable to just plane raking the rig by letting go the forestay and pulling it bacik up again which is pretty much all that's open to me on say the Solution and that Supersofa, and to a limited extent it helps by depowering upwind if it gets a bit blowy and dead downwind with the shrouds slack getting the boom out.
But think about it, if the mast base could be shifted back without moving the shroud anchor ponits then that moves the boom pivot back and accomplishes the same thing, without necessarily having the depower going on upwind unless you moved it a long way forward. Also, and it is a bit of an issue with this Fireblade boat which rides a bit nose up, I suspect because it's actually a cut down Icon (with a bit of a noisy stern), so moving the mast base forward would help keep the nose down and engaged waterline length and all a la Raceboard. It's tricky really, I can't help thinking like this because it's what works and has served well over the stand up years. I guess what I'm really looking for is good reasons not to, other than just the pfaff it's going to cause. I need to have more goes and get some wiring time in before really going hard at it, but I just wanted to know what had been tried down the years and thanks for everything y'all have come up with so far. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: Sam.Spoons
Date Posted: 17 Nov 20 at 10:24pm
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Is there any indication how far forward Mike moved the mastfoot in the conversion from Icon to Fireblade? That said moving crew weight is probably a more effective way of correcting trim than moving the rig, on a RB we had to move the rig simply to allow the sailor to move forward. ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Cirrus
Date Posted: 17 Nov 20 at 10:44pm
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Upwind you should be able to engage about 100mm of the bow in the water . (plenty imo) as speed increases I would adjust the crew position ending up with the bow knuckle just clearing the water. Little impression of speed even then as it barely produces any real wake ... usually a good sign ! Best to get a few hours simple sailing 'as is' before any really radical changes though ! Short term as mentioned already in ref to masts it might be very sensible to use a ligher (carbon) stick if onc can be sourced at a sensible price - particularly if (like GRF) you are lighter yourself. a flexi carbo stick might be worth the early effort whatever comes next then maybe consider more complex controls / adjustments if still looking for additonal controls - I'm not sure they will be needed if the stick issue is addressed. BTW the mast position was moved forward by about 250-300mm as this question was asked and the boat is approx 280mm shorter than Icon (and is quite different in terms of hull freeboard, beam etc) .. but inherits / shares a similarly low rocker shape.
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Posted By: patj
Date Posted: 18 Nov 20 at 9:47am
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The modern Applecore has adjustustable shrouds and jib tension but gets away without lowers by having a hog stepped mast with an adjustable ram at deck level. Add leading back the forestay to pull the mast forward again and there can be an awful lot to do at those marks even for two crew and ensuring you get the same settings twice is probably the hardest bit.
We also have a Zoom - think Laser clone with 2 position stayed deck stepped mast and trapeze - and the current mast is somewhat tree trunk and not original - possibly off an Enterprise. Suggestions welcome for a more suitable mast - can't afford carbon!
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Posted By: Rupert
Date Posted: 18 Nov 20 at 9:49am
And all for a minuscule speed gain in a one design with loose rules concerning rigging. If starting from scratch, surely there are better ways of getting a bigger increase in speed? ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: JimC
Date Posted: 18 Nov 20 at 12:40pm
| It was long a bugbear of mine that certain classes would spend enormous amounts of money on going 1% faster to the exclusion of what might make a boat go 10% faster. These days I'm not so convinced that going 10% faster is necessarily a good thing, at least in terms of popularity, but I can still think of classes where some more vigorous enforcement of the original rules and a determination to avoid what one might call creeping complexity would have kept the sport a lot more affordable. |
Posted By: 423zero
Date Posted: 18 Nov 20 at 1:11pm
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Time in the same boat and coaching, would give you a significant advantage, certainly more than all the gizmos, excepting making it foil. ------------- Robert |
Posted By: The Moo
Date Posted: 18 Nov 20 at 1:14pm
| And if Graeme is hoping to build an active class off the back of this project, I can't help thinking all this proposed complexity is likely to put a lot of punters off. |