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Mast rake: explain please!
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NHRC View Drop Down
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Posts: 102 		Post Options Post Options   Quote NHRC Quote  Post ReplyReply Direct Link To This Post Topic: Mast rake: explain please!
    Posted: 23 Dec 14 at 1:30am
Originally posted by Time Lord

NHRC

In the Merlin one string systems that I have come across, the lowers are incorporated into the system. Have you set yours up differently?


Mine are incorporated too but they are adjustable as well, separate to the rig tension that controls the shrouds and forestay. You can use your lowers in the same way that Mike was saying that he uses his mast strut.

Edited by NHRC - 23 Dec 14 at 1:33am
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Time Lord View Drop Down
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Posts: 301 		Post Options Post Options   Quote Time Lord Quote  Post ReplyReply Direct Link To This Post Posted: 18 Dec 14 at 4:42pm
NHRC

In the Merlin one string systems that I have come across, the lowers are incorporated into the system. Have you set yours up differently?
Merlin Rocket 3609
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Do Different View Drop Down
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Posts: 1312 		Post Options Post Options   Quote Do Different Quote  Post ReplyReply Direct Link To This Post Posted: 18 Dec 14 at 4:04pm
Thanks Sawman. Now installed Firefox; missing images have appeared.   

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Posts: 102 		Post Options Post Options   Quote NHRC Quote  Post ReplyReply Direct Link To This Post Posted: 11 Dec 14 at 6:36am
Cheers for your post Mike.

The only difference between what your doing and I'm doing re de-powering is that your 505 is hog stepped with a strut and separate controls my Merlin is deck stepped with lowers and has a one string adjustment.

I wonder if the way the one strong increases lowers loading as I rake, is about the same amount as your floating stru adjustment.


I think most merlin sailors with a one string system rarely alter their lowers. Though easing them a touch in light wind and very big breeze does happen a bit to get a controlled lower mast bend.
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Mike Holt View Drop Down
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Posts: 58 		Post Options Post Options   Quote Mike Holt Quote  Post ReplyReply Direct Link To This Post Posted: 10 Dec 14 at 8:57pm
In my head I am going from a high power setting to a low drag setting so it is a bunch of incremental steps with a few considerations to make.

1. Is it flat, choppy or rough? The flatter the water the quicker you can go to a low drag set up.

2. Is it gusty? Do I need to set up for the top or the bottom the wind range?

As I rake I will also go down on ram, trying to keep the mast shape the same. We calibrate the settings so that as we rake the ram comes down at a "neutral" rate. If you set a boat up with the ram unloaded, mark where it goes at each calibration point as you rake. We do it in 1 inch increments. We "take up" the shrouds at the same rate. However, this actually translates to a gradual increase in shroud tension, which also results in extra static mast bend. I have my set up automated, so I only have to release forestay and take up shrouds.

At the same time I will increase outhaul and cunningham. At a certain point, for us around 18 knots I will also start to move jib leads outboard.

As I go through the range I repeat these steps. At some point we pull on a flattener in the main, takes out about 6" of leech length and enables us to get under the boom easily.

There is also a point where continuing to pull kicker on is adding drag so if the boat is tripping I will stop pulling that on.

This continues until the wind has become to strong to handle!

Hope that all makes sense.

Mike
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Posts: 102 		Post Options Post Options   Quote NHRC Quote  Post ReplyReply Direct Link To This Post Posted: 10 Dec 14 at 6:07pm
Hi mike,

When going through the de-powering gears, how does take compare to pre-bend?

Do you use full rig tension before you get to raking...?
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sawman View Drop Down
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Posts: 205 		Post Options Post Options   Quote sawman Quote  Post ReplyReply Direct Link To This Post Posted: 09 Dec 14 at 7:13pm
Originally posted by Do Different

Tried to post a sketch but been all around the houses and nothing works. For that matter it's a lottery if I can see the recently posted photos by others, sometimes they flash up for a fraction of a second and then vanish leaving large blanks.
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I get this when using chrome or safari browsers - try firefox, this works for me with Mac OSX yosemite
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Posts: 84 		Post Options Post Options   Quote AlanH Quote  Post ReplyReply Direct Link To This Post Posted: 09 Dec 14 at 4:26pm
Thanks Mike. I move my ram back on Osprey too as I rake, so glad to see your confirmation. Its quite an art trying to avoid losing too much pointing when you rake/ otherwise depower. Having ram and rake on one system sounds good. I have 4 ropes to adjust rake/ ram, so sometimes opt for just opening slot with barbers instead when it blows up, rather than faff with 4 ropes. But that crude method loses height.
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Posts: 1312 		Post Options Post Options   Quote Do Different Quote  Post ReplyReply Direct Link To This Post Posted: 09 Dec 14 at 2:38pm
Thanks Mike.

I'm all out of conversation on this one.

Your's sounds like a good plan and fairly transferable to my rig, I'm sticking with that.  Beer  
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Mike Holt View Drop Down
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Posts: 58 		Post Options Post Options   Quote Mike Holt Quote  Post ReplyReply Direct Link To This Post Posted: 09 Dec 14 at 2:28pm
This is an interesting topic and as it wanders around different parts I think you need to look at each one in isolation to truly understand what is going on. 

As an example, mast ram(strut), lowers or chocks. For the longest time I thought that they increased or reduced mast bend. But really they don't. The mast bend is induced by other factors, spreaders, shroud tension, differences in height between shrouds and forestay on mast etc. In reality they control where the bend is. More ram low down straightens the bottom of the mast BUT increases bend higher up, the reverse will happen if you reduce ram, the bottom will bend more but the top section will straighten. I now think of it as a "bubble" that I can control.

So, straightening a lower mast, bends the upper mast, opening the upper leech, enabling more twist up high for an easier groove and higher speed through the water and if all else is right, a reasonably tight lower leech helping to maintain height.

Combined with rake, fast.
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