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Author Topic: height of backstay split  (Read 7389 times)

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Ed Shankle

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height of backstay split
« on: May 09, 2007, 07:06:14 AM »

As mentioned in earlier posts, I'm replacing the standing rigging this season. Work is about to get underway, but a thought just struck me; I should redesign the backstay split!
Currently, I have an adjustable split that is about 7 - 7.5 ft up from the cockpit sole.
I don't think the adjustable is really necessary, since the rig is not fractional, and additional height would make the stern entrance easier (no walk thru on Tail Wind).
So, who has a high backstay splitter and what height is it? Is there any rule of thumb or recommendation?

thanks,
Ed
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Ed Shankle
Tail Wind #866 1989
Salem, MA

Steve Sayian

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Re: height of backstay split
« Reply #1 on: May 09, 2007, 07:24:37 AM »

Hi Ed,

I just checked my MKII owners manual and the backstay bridal is 1X19 - 1/4" wire and is 15 feet long.

Don't know if this helps.

Steve


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Steve Sayian
"Ocean Rose"
1999 Mk II
Wing, Std Rig, Kiwi Prop
#1448, Hingham, Mass

steve stoneback

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Re: height of backstay split
« Reply #2 on: May 09, 2007, 08:19:01 AM »

I too have an 89 (#918) with the low position backstay split and would like to have more headroom when boarding from the stern.  The stern chain plates are mounted at an angle that allows a straight pull with the low split.  My question is, will pulling on them at a higher angle cause any problem with the chain plate?.
Steve
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Steve Stoneback
Grasmere
1989 #918
Lake Oahe Pierre, SD

Ken Juul

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Re: height of backstay split
« Reply #3 on: May 09, 2007, 10:05:02 AM »

I still have the old rigging on my garage floor.  I'll measure it tonight, Mk 1.5 split is about 15-18 feet off the cockpit sole
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Ken & Vicki Juul
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dave davis

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Re: height of backstay split
« Reply #4 on: May 09, 2007, 10:45:09 AM »

I also have had a split on my 1988 that the CY designed that was very much in the way when sitting in the normal hump. I am 5'8" and it came down around my ears. I had the split moved up about 2' for two reasons. I wanted to install an adjustable back stay so that I had a better method for taking the sag out of the forstay when racing. The slight change in the angle at the attachment has not been a worry for me. The new design which has the split about  15-17 feet high would be OK but it is very poor if you also want to add an adjustable rolling device. It just does not work.
Good Luck, Dave
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Dave Davis San Francisco, 707, Wind Dragon, 1988, South Beach

Stu Jackson

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Re: height of backstay split
« Reply #5 on: May 09, 2007, 11:05:04 AM »

Here's Dave Davis' sketch for the raised backstay.
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Stu Jackson

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Re: height of backstay split
« Reply #6 on: May 09, 2007, 11:12:26 AM »

Here's a picture of our raised backstay with the Garhauer adjuster and a Garhauer vang.  The height, as Dave mentioned, shouldn't be too high.  We used his dimensions for the added height.  There are new large D shackles at the chainplates and both of the backstays at the transom incorporate new tangs (toggles???) for flexibility in the fore and aft dimensions.  These tangs were suggested by our surveyor, who noted that the chainplates and the backstay did not line up, which put added stress on the chainplates without the tangs.
« Last Edit: May 09, 2007, 12:23:28 PM by Stu Jackson »
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Ed Shankle

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Re: height of backstay split
« Reply #7 on: May 09, 2007, 12:15:03 PM »

Stu and Dave,
I guess that fact that you use the adjusting harness means you find it useful. I was under the impression that if the forestay is not fractionally rigged, then an adjustable backstay really isn't needed. Can you give me more insight?

thanks,
Ed
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Ed Shankle
Tail Wind #866 1989
Salem, MA

Stu Jackson

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Re: height of backstay split
« Reply #8 on: May 09, 2007, 12:20:39 PM »

Ed, the concept is to tighten the forestay by cranking in (a bit) on the backstay.  It's NOT a huge amount, but does somewhat tighten the forestay when going upwind.  Going downwind, one lets off the adjuster.  The masts are telephone poles, but the fore and aft trigonometry allows this to happen.  It does nothing to the mainsail shape, which is what the fractional rig backstay tensioning is designed to do.  But that's for "bendy" rigs anyway, on smaller boats or rigs specifcally designed for that function.  Ours are not.
« Last Edit: May 09, 2007, 12:22:13 PM by Stu Jackson »
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Steve Sayian

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Re: height of backstay split
« Reply #9 on: May 09, 2007, 12:58:21 PM »

Hi Ed,

The picture of the MK II on the Home Page shows the relationship of the split backstay to the helmsman. 
Could you fit an adjuster to that type setup?  You get the headroom you want as well as the adjuster.  (I'm thinking about that too)

Steve
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Steve Sayian
"Ocean Rose"
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Stu Jackson

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Re: height of backstay split
« Reply #10 on: May 09, 2007, 01:56:40 PM »

Steve and Ed, the point that Dave Davis made was that height is NOT workable for an adjuster.  It is too far up, so that pulling down on an adjuster would not provide adequate tension (unless the line was very long and you pulled WAY far down on it).  You'd end up with miles of line in your cockpit from the vang.  As the triangle piece is lower in Dave's arrangement, the split backstay parts are further apart and permit more tension to be applied in a shorter distance, and make it workable.  Dave recommends that the super high backstay shown in that photo will not work with an adjuster.  Sorry, it's just trigonometry, again... :cry4`
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Ken Juul

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Re: height of backstay split
« Reply #11 on: May 09, 2007, 02:38:56 PM »

The backstay pin to pin measured 34'3" on my old backstay.  The bridle legs measured a little over 15' (left the turnbuckles on the boat so I don't know exactly).  That would put the junction of the legs 15' above the lower attach staps or about 18' above cockpit floor level
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Ron Hill

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Re: height of backstay split
« Reply #12 on: May 09, 2007, 07:22:15 PM »

Ed : I've written this before!!!!  I'm surprised that the PEs haven't mentioned it.
You might want to check with the factory before "acutely" changing the height of that back stay split (and the angle of pull)!
Look at the bolts that are thur your transom that hold the "chain plates" for the split back stay.  They were drilled and embedded for a particular angle (based on the height of the split). 
I don't know how much you can deviate, but think that you might want to check before you deviate too much? 
A thought!    :roll:
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Ron, Apache #788

rirvine

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Re: height of backstay split
« Reply #13 on: May 10, 2007, 04:35:21 PM »


I assume that the MKII being discussed is Crew’s Nest.  I found that the traditional type of split backstay adjuster arrangement did not work all that well.  The angle between the split is too narrow to force the blocks back up the stays when to adjuster is released.  The blocks on the stays tended to bind and then had to be pushed up with a boat hook. (No, I did not try ball bearing blocks).

I solved the problem using the arrangement show in the attached:

The idea is to pull the 2 part of the split backstay together to increase the tension in the forestay when going up wind. The blocks attached to the stays are about 6 feet above the cockpit floor.  When pulled in hard (block to block), they do interfere with the driver’s head but that is not an issues as he usually sit on the leeward rail to get a clear view of the jib.  Becasue of the 12:1 purchase, it is easy to adjust with one hand.    Hope this helps.

Ray
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Ed Shankle

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Re: height of backstay split
« Reply #14 on: May 11, 2007, 11:14:14 AM »

Stu,
I assume the hardware you referred to in your (and Dave's design) was intended to deal with the angle variation that Ron discussed. I'm looking to do what you guys did, that is, go up a couple of feet; not go up as high as Ken described and as the picture on the home page illustrates. I like the idea of still having the option to tighten up the backstay with an adjuster. I'll also discuss the chainplate angle with our rigger.

Ed
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Ed Shankle
Tail Wind #866 1989
Salem, MA
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