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PostPosted: Tue May 15, 2007 4:57 am 
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Location: Carolina Beach, NC
Hi,

Can someone tell me what and how to use the large stainless steel "loop thingy" at the bottom of the mast (I guess it has something to do with rotation)......confused.

Thanks,

Chris


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PostPosted: Tue May 15, 2007 5:28 am 
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Location: 315 N. Hwy 79 Panama City Beach, FL 32413 850-235-2281
sounds like a mast rotation bar. read the H18/20 tuning manual and adapt it to the H17. Our basic rule is upwind have it pointed to the point where the rear cross bar and hull meet, downwind let the mast rotate as far as possible. I am sure you will get some people with better/different opinions than mine.

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PostPosted: Tue May 15, 2007 6:55 am 
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Follow Brad's instructions and you'll be seriously under-rotated.

Base adjustment on the 17 is to have the rotator pointed at the leeward shroud when going upwind. Unless you're racing, I'd leave it alone going downwind.


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PostPosted: Tue May 15, 2007 7:22 am 
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I am still confused.....maybe i need an explanation on what this thing is and how it's supposed to work before I start to figue out how to "fine tune" it.....poss. even in very "basic" terms...sorry


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PostPosted: Tue May 15, 2007 8:02 am 
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The rotation bar at the base of the mast works in conjunction with the forward-most cleat on the boom as well as a piece of 3/16" line, approximately 3' long. Tie one end of the line to the cleat, pass the other end of the line through the loop in the end of the rotation bar and then back into the jaws of the cleat. Tighten the line to reduce mast rotation, loosen the line to increase rotation.

sm


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PostPosted: Tue May 15, 2007 8:09 am 
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The first thing you should do is order the assembly manual for the 17 from Hobie Cat (you can do it from the Support section of this site). It will cost you about nine bucks.

Mast rotator arm / control:
OK, here are a couple of poor photos to go from:
Image
Arrow number 3 is pointing to the mast rotator arm. It goes above the boom. There's a line tied to a cleat on top of the boom (you can see the outline of the cleat just ahead of the green part of the duffel bag in the lower left corner of the picture).

The line goes from the cleat, through the hole in the end of the rotator arm and back through the business part of the cleat. You control the amount of mast rotation relative to the boom by varying the length of the line.

Here's a marginally better photo of the set-up on a Hobie 14:
Image
In this instance, the rotator is under the boom, but everything else works the same. The rotator in this picture is pointed directly at the camera, so you can't really tell it sticks out about 10".


Last edited by MBounds on Tue May 15, 2007 10:51 am, edited 1 time in total.

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PostPosted: Tue May 15, 2007 10:21 am 
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Location: Carolina Beach, NC
WOW...Thanks !!

Now I know how to "set it up" ! Thank you very much!

I'm guessing it's job is to keep the boom and the mast on the same "plane", or "not" if that is what you choose. How do I fuigure out when to let it rotate "off of the same plane" as the boom....I gues what i'm trying to say is..."when and why"....(this is the fine tuning part)

Thank you so much for this forum and your help !!

Chris


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 Post subject: Mast rotation
PostPosted: Tue May 15, 2007 11:34 am 
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If you've ever flown by commercial jet, you'll notice on take off and landing that the FRONT EDGE of the wing rolls forward. Technically, those are known as leading edge flaps, and their purpose is to change the 'chord' of the cross section of the wing, which provides more 'lift' at lower speeds. The rear flaps do the same thing, but I want to use the example of leading edge profiles.

In vessels with rotating masts, you can achieve the same effect (sort of) by allowing the mast to rotate. At lower speeds, more rotation is a good thing as it provides more 'lift'. The higher the wind speed, the less rotation is required. Upwind and downwind are different.

Probably, Matt Bounds, sorry Guru Matt Bounds can give a better explanation, but this is how we teach our new cat sailors. Watch what other cat sailors do, follow their lead, ask questions like you have been, its amazing how much you can learn.

Good winds

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PostPosted: Tue May 15, 2007 2:27 pm 
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Location: Carolina Beach, NC
Thank you.

So low wind speeds, more rotation =/creates more "lift/power"...at higher wind speeds it is not ness....right?

Thank you very much.

Chris


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 Post subject: Holy Grail
PostPosted: Tue May 15, 2007 7:33 pm 
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Location: League City, TX
Chris:

This is the Holy Grail of cat sailing.

http://store.catsailor.com/tek9.asp?pg= ... =jqcmhpjpe

There is a whole chapter on the 17 by Carlton Tucker. Get it from Hobie Dealer is you can or from Rick. Will explain it all and cut three years off learning curve. Thee are the changes I have made.

http://www.thebeachcats.com/modules.php ... _album.php

Doug


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PostPosted: Wed May 16, 2007 9:08 am 
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Location: Jersey Shore
If by in the same plane, you mean, having the rotator bar pointed in line (parallel) with the boom, you never want that.

Mast rotation allows you to control two things- the angle of the mast relative to the apparent wind and the bend of the mast. As a general setting, you want the rotator bar to point in the vicinity of the shroud (sighting along the bar) for upwind sailing. In stronger wind, you can increase rotation (point the bar farther forward) which allows the mast to bend more which flattens the sail to depower (although increasing rotation increases drag because the flat side of the mast is presented to the wind).

Downwind, release the rotator so it will point approximately 15 degrees in front of the front crossbar. The leading edge of the mast will be pointing towards the apparent wind.

If you're not racing and just want a good all around setting, point the rotator at the shroud and leave it set.

sm




>>>I'm guessing it's job is to keep the boom and the mast on the same "plane", or "not" if that is what you choose. How do I fuigure out when to let it rotate "off of the same plane" as the boom....I gues what i'm trying to say is..."when and why"....(this is the fine tuning part) <<<


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