Raking Rigs

   Why do you get more mast bend when you rake? You've obviously measured the effect, so I'm not suggesting you are wrong, just trying to figure out the relationship.

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Rupert Send Private Message Find Member's Posts Really should get out more Joined: 11 Aug 04 Location: Whitefriars sc Online Status: Offline Posts: 8956	Post Options Post Reply Quote Rupert Report Post Quote Reply Topic: Raking Rigs Posted: 02 Nov 13 at 4:16pm
	Why do you get more mast bend when you rake? You've obviously measured the effect, so I'm not suggesting you are wrong, just trying to figure out the relationship.
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Do Different Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 26 Jan 12 Location: North Online Status: Offline Posts: 1312	Post Options Post Reply Quote Do Different Report Post Quote Reply Posted: 02 Nov 13 at 4:24pm
	As you lean the mast back the change in geometry means spreaders push more hence more mast bend, assuming you keep the same rig tension. Edit. Oh yes and if you don't reset the lowers, chocks or strut they will ease as well giving more low down bend. Edited by Do Different - 02 Nov 13 at 4:33pm

Do Different Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 26 Jan 12 Location: North Online Status: Offline Posts: 1312	Post Options Post Reply Quote Do Different Report Post Quote Reply Posted: 02 Nov 13 at 4:29pm
	BTW. A friend of mine sails a 505 with light to medium crews and he says it's a must have. If the wind gets up and it's all getting a bit much he just dumps the rig back, eases the board and hey presto, well mannered and flying again.

JimC Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 17 May 04 Location: United Kingdom Online Status: Offline Posts: 6662	Post Options Post Reply Quote JimC Report Post Quote Reply Posted: 02 Nov 13 at 5:04pm
	The stuff about centre of effort is obviously a nonsense: the sums demonstrate its minimal. Think, by jamming on the downhaul, blading out and twisting off the top of the rig (assuming a reasonable rig) you drop the effective centre of effort by feet, so why on earth would moving it at best three inches down make a happorth of difference? Similarly the actual effect on the sail chord isn't going to be that great either. On the other hand the posts on SA from SHC seem to actually provide some sort of rational explanation - the first I've seen, because I must have missed that thread. I don't doubt that for many types of rig there are secondary effects due to the way other bits of the rig interact though. Edited by JimC - 02 Nov 13 at 5:05pm

iGRF Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6499	Post Options Post Reply Quote iGRF Report Post Quote Reply Posted: 02 Nov 13 at 5:14pm
	The other point you have to consider with a raked back rig, the foil section of the sail is no longer acting as efficiently as it's designed parameter, there is also an element of vertical lift, obviously we get this more on racing sailboards as we rake our rigs much more, to reduce the 'railing' (you'd call it heeling)effect. the obvious benefit to us is we can hold onto bigger rigs and can balance the heel exactly by multiple options in the rake. Honestly a good dose of sailing a long race board makes it easier to comprehend if only by anecdotal 'feel' evidence as to what happens. I wish it could be organised on a dinghy as easily as it occurs on a board with one push to a foot pedal. A Merlin dude walked me through their system at the Dinghy show, it does what I need, but jeez how complicated the ropes and had I forgotten how it worked within yards of leaving the stand? Edited by iGRF - 02 Nov 13 at 5:16pm
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Mike Holt Send Private Message Find Member's Posts Groupie Joined: 29 Nov 09 Location: United States Online Status: Offline Posts: 58	Post Options Post Reply Quote Mike Holt Report Post Quote Reply Posted: 02 Nov 13 at 5:33pm
	I am sure every boat is different, but on a 505 when you rake, it is firstly a considerable move of the rig. The boom at the outboard end moves more than 3 feet between fully upright and fully raked, the mast moves aft 4 to 5 inches at deck level. We also maintain mast bend as we rake, but importantly move where the bend is. We "ram down" hard, this moves the point of max bend up the mast helping to flatten and twist the upper 1/3 of the main. You are also opening up the slot between main and jib. The result is dramatic. In 18-20 knots of wind you would not be able to sheet the main inside the quarter of the boat and it would be back winding dramatically with the rig upright. The boat would be triply and slow. Drop the rig back, board up slightly(not much though with the very high aspect foils we now use) cunningham on hard and the main will be back in the boat, no back winding and the boat will now go fast forward and easy to control. Edited by Mike Holt - 02 Nov 13 at 5:34pm

Do Different Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 26 Jan 12 Location: North Online Status: Offline Posts: 1312	Post Options Post Reply Quote Do Different Report Post Quote Reply Posted: 02 Nov 13 at 5:47pm
	Thanks Mike. Stuff I can relate to and use.

Oatsandbeans Send Private Message Find Member's Posts Far too distracted from work Joined: 19 Sep 05 Location: United Kingdom Online Status: Offline Posts: 382	Post Options Post Reply Quote Oatsandbeans Report Post Quote Reply Posted: 02 Nov 13 at 5:48pm
	I think that Mike ( and GRF!) have a good point regarding the effect of rake changes on the balance and feel of the boat. As the rig is raked back and the board is raised you then feel the boat "lighten up" and you lose the feeling of being overpowered and it tripping over itself. You can now sail off marginally and go for a fast mode getting speed without sacrificing too much height. The 505 sailors have this well sorted as they have a very well defined set of numbers to work to ( have a look at the the articles on the web on this-they really know how to get the most out of the rig through the wind ranges). GRF will also intuitively know about this from his long board sailing. Here the effect of knocking the rig back on the track 2" or raising the board by a similar amount can really be felt and the board will change completely. So more rake will all help to make a dinghy faster and easy to sail in a breeze, from both the balance and reduced heeling force from the increased mast bend.

ChrisI Send Private Message Find Member's Posts Visit Member's Homepage Posting king Joined: 09 Aug 10 Location: United Kingdom Online Status: Offline Posts: 143	Post Options Post Reply Quote ChrisI Report Post Quote Reply Posted: 02 Nov 13 at 6:57pm
	I'm keen to understand this one - still don't properly. Some questions for you Mike: - 3 feet is huge. Can you get under the boom when it is raked? Or do you have a flattener? - would a carbon mast on a 505 depower better with this technique, or is the design of the current alu one such that it is almost as good as a carbon one would be? - would there be any difference between a pin-head and a square-top main in terms of the extent to which they depower from mast-raking?

Do Different Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 26 Jan 12 Location: North Online Status: Offline Posts: 1312	Post Options Post Reply Quote Do Different Report Post Quote Reply Posted: 02 Nov 13 at 8:50pm
	I found this article a while back. http://northsails.com/RADUploads/How-Sails-Work.pdf Reading it is easy. Understanding it, hhhhhmmmmmmm. Remembering to put it all into practice, aagggghhh. But then if was easy............................