Mast rake: explain please!

   Hi all,Could someone please explain how raking the rig back in strong winds affects the feel/performance of a boat? Is it another way of depowering the rig, analogous to lashing on more kicker and cunno? I've yet to come across a satisfactory explanation of this...

Thanks,
Peter

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dohertpk Send Private Message Find Member's Posts Posting king Joined: 28 Sep 12 Online Status: Offline Posts: 172	Post Options Post Reply Quote dohertpk Report Post Quote Reply Topic: Mast rake: explain please! Posted: 27 Nov 14 at 7:02pm
	Hi all, Could someone please explain how raking the rig back in strong winds affects the feel/performance of a boat? Is it another way of depowering the rig, analogous to lashing on more kicker and cunno? I've yet to come across a satisfactory explanation of this... Thanks, Peter

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: 27 Nov 14 at 9:16pm
	That's a big question, there will be lots of different theories. I would say many small things happen which on their own don't seem that major but do add up to something that certainly does. Of course the effect it is not the same for all boats, different rig setups you see. Hopefully Mike Holt 505 World Champion will step in and explain. Probably the most relevant class to routinely use the method.

zippyRN Send Private Message Find Member's Posts Far too distracted from work Joined: 14 Sep 06 Online Status: Offline Posts: 437	Post Options Post Reply Quote zippyRN Report Post Quote Reply Posted: 27 Nov 14 at 10:16pm
	some of the factors mast rake effects : moves the center of effort depending on the rest of the geometry can open the slot

dohertpk Send Private Message Find Member's Posts Posting king Joined: 28 Sep 12 Online Status: Offline Posts: 172	Post Options Post Reply Quote dohertpk Report Post Quote Reply Posted: 27 Nov 14 at 10:18pm
	Yes the reading material out there paints a very confusing picture. I suppose my question is if raking the rig noticeably reduces the power in the same way as pulling all the control lines on tight does?

chris_wht Send Private Message Find Member's Posts Visit Member's Homepage Groupie Joined: 12 May 04 Location: United Kingdom Online Status: Offline Posts: 50	Post Options Post Reply Quote chris_wht Report Post Quote Reply Posted: 28 Nov 14 at 12:12am
	on your 600? I found it really helps stop the submarining in big wind / waves.


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: 28 Nov 14 at 1:30am
	The mysteries of rake, I wish I knew for sure! But it is certainly very effective on a 5O5 and many other dinghies I have sailed. First what we do, between all the way up with the rig (max power) to all the way back (max de-power) we move the tip of the mast back about 14 inches. While doing this we try to maintain a reasonably consistent mast bend, however as you rake it gets harder to do so. We also move the shroud bases aft by 3 inches. We have a set up where the mast ram (strut) comes on automatically as we rake. We also increase shroud tension and rake the board aft slightly to maintain balance. We have High Aspect foils so you cannot go very far with them. Now, why does it work? These are my observations, nothing more: 1. You open up the jib leech and open the slot. 2. You are lowering the center of effort. But not that much 3. The rig becomes more automatic in it's gust response. Less support from the forestay and shrouds 4. Less drag in the rig, sails are flatter, leeches more open The difference for us is enormous and I just gage where the boom is in relation to centerline and the inside edge of the seat tanks. If the boom is too far out, rake until it comes back closer to centerline. Always on centerline, pull the rig forward. We also sail with lots of cunningham and jib cloth tension in breeze and aim to sail the boat in fast forward mode and let height take care of itself. Mike

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: 28 Nov 14 at 7:39am
	My take on this is that there are a combination of factors that all help make the boat go faster in a blow with more rake, but the most important is the effect that rake has on mast bend. If you rake back the rig 1/2 a hole on the shrouds it gives 10mm more mast bend. So if going from a 10knot setting to a 25 knot setting you rake the rig back 1 1/2 holes this is 30 mm more bend. ( if you want to know what this does to the main it takes out 3% of camber, which is a big deal when you need to get the sail as flat as you can in a breeze -down to a heavy wind setting of 8% camber from a med weather setting of 13%, the rest can be done with vang, cunn, and strut changes).

jaydub Send Private Message Find Member's Posts Far too distracted from work Joined: 06 Jan 07 Online Status: Offline Posts: 267	Post Options Post Reply Quote jaydub Report Post Quote Reply Posted: 28 Nov 14 at 8:45am
	O&B, Interested in the logic for increasing mast bend. Logic tells me that the more you rake the mast back, the more impact the spreaders will have in terms of straightening the mast. Or have I got that wrong?

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 Posted: 28 Nov 14 at 8:56am
	Unless you are keeping the mast locked at deck or lowers level, I can't see the mast bend thing either. And as the mast rake we are talking about involves that movement (the whole point, in fact) I must be missing something too.
	Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686

Null Send Private Message Find Member's Posts Really should get out more Joined: 11 May 14 Online Status: Offline Posts: 745	Post Options Post Reply Quote Null Report Post Quote Reply Posted: 28 Nov 14 at 9:24am
	I'm not sure i understand this Mast bend thing either? Surely thats something very different to Mast rake? If you 'Drop' holes and retain the same rig tension and spreder deflection then i can see how prebend or mast bend would change. But this is not what i would define as mast rake. I class mast rake as dropping the tip of the mast further back. Rightly or wrongly? Good question Mike Holts description is great, he sure knows his eggs and apples (Current 505 World Champion) We were lucky enough to be buddied up with Mike at the 505 Nationals a few years back, he has an excellent knowledge of how rigs work. I learnt so much!