No backstay adjuster/tensioner - why?

H

Harry P

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My Moody S31 hasn't a backstay adjuster. I'm reading up on rig tuning etc and the topic of backstay tensioning features a lot. I'm wondering what the thinking behind my rig is and how I should use it to get the best out of it. Btw it's also a fractional rig possibly 9/10ths? Any thoughts, views or advice on this would be appreciated.

Cheers,
H
 
Harry P said:
My Moody S31 hasn't a backstay adjuster. I'm reading up on rig tuning etc and the topic of backstay tensioning features a lot. I'm wondering what the thinking behind my rig is and how I should use it to get the best out of it. Btw it's also a fractional rig possibly 9/10ths? Any thoughts, views or advice on this would be appreciated.

Cheers,
H
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She was designed as a cruiser, dont worry just enjoy
 
Harry P said:
My Moody S31 hasn't a backstay adjuster. I'm reading up on rig tuning etc and the topic of backstay tensioning features a lot. I'm wondering what the thinking behind my rig is and how I should use it to get the best out of it. Btw it's also a fractional rig possibly 9/10ths? Any thoughts, views or advice on this would be appreciated.

Cheers,
H
Click to expand...

The purpose of an adjustable backstay is to bend the mast and so adjust the shape of the main. With a 9/10 rig the scope for this is very limited and would guess that Moody thought it was not worth bothering with.

Suggest you ask fellow owners through the MOA what they have and whether it is worth fitting one.
 
Our boat is also a 90% fractional rig and also came without an adjustable backstay: just twin backstays with a bottle screw.

I had a block put high up on the steel backstay, a dyneema backstay running up to it and back to the other quarter and an 8:1 block system. It quite radically de-powers the main and it’s a control I now wouldn’t be without.

Just change it IMHO.
 
An adjustable backstay on a fractional rig can pull the top of the mast back freeing off the leach of the main sail so depowering the top of the main. Especially good in a gust when hard on the wind. Two different kinds of match racing fleets here (Bakewell White 8 and Foundation 36) have a box in the middle of the cockpit floor with 3 lines coming out for adjustment. The main sheet the vang and back stay. The main sheet hand is expected to operate all 3 to keep the boat with correct power in the main sail when racing. When that back stay is yanked on hard it is dramatic how much the top of the main sail drops away. However that is on a boat with something like 70% fractional. (and raced hard) Boats are all identical and allocated by ballot to crews.
Now if you have a 90% fractional things will be a lot different. Not nearly as much movement back of the top of the mast with back stay on hard so not so much freeing off of the main. You will however get an opportunity to increase the tension on the forestay so flattening the jib. Much better in a blow when beating.
So it is hard to say if you will benefit by an adjustable back stay. Most back stays are split to two chain plates on transom. The split coming from 1.5 metres or so above transom. Essential if you have a transom mounted rudder. If it is split you can fit a sheave at the split point. Run a piece of dyneema or 7x19 wire from on chain plate through the sheave and back down to a tackle (4to 1 typically) to the other chain plate.
The alternative with split back stay is to make up 2 plates with 2 sheaves between them which is set up with the 2 back stay legs running in between the sheaves. This plate is hauled downwards so forcing the legs of the back stay together and so increasing tension on back stay. It may or may not be vital to keep the integrity of the backstay. You don't want tom loose a mast through too much release of the back stay. Although in many fractionals like mine back stay is not essential to rig staying up. (cap shroud chain plates aft of abeam the mast provide tension backwards to hold mast up.
If you have a single back stay to a single chain plate you may cut the back stay short and insert a tackle or even a hand wheel screw adjuster. I would suggest however a clamp up the back stay to which you attach a tackle so that you shorten the back stay so that release of the tackle just reverts back to normal back stay length.
Just for you to think about. Just remember advice on sail adjustment and rig tuning can be a lot different for different boats (like different degrees of fractional rig) have fun ol'will
 
Our recently acquired S31 is masthead but still has a 24-1 cascade on the backstay, 2-1 wire above 2-1 dynema terminating in a 6-1 tackle; overkill, I know but the first and second owners raced her a bit. I do not believe that Moody would have sold a boat without any form of
adjustment and find it puzzling that you do not have any any, surely that was most of the point of the fractional rig option? Is your backstay not split to come down either side of the transom access gate? If it is, surely there has to be some form of adjustment at one end there unless someone has modified it with a longer wire strop.

I had a look but the marketing catalogue is on the boat, but I found the 'Sailing Today' review of Cornsilk, she appears only to have had a bottle screw at the bottom of the stay where it meets the split bridle, not something you could adjust easily or underway so perhaps the standard rig design is even more crude than I had imagined, with two pairs of lowers it was certainly backward for its time but then the Bill Dixon started his career with Angus Primrose so perhaps avoided exposure to modern rig design. Westerly were a bit more open minded?
 
Guys, thank you all for the really sound advice. My backstay hasn't any adjustment on it and has the split to allow access to the opening tailgate. I'm likely to fit a tensioner based around this when I get the chance. Also not rigged was a Cunningham. There's a cringle in the mainsail for it so I'll fit this also. Once again thanks for all your input :-)
 
Harry, if I wuz you, I would fit a block suitable for wire at the bottom of the backstay, shorten or replace the split wire to run from one existing strong point on the transom through the new block and down to a 6-1 tackle on the other side. Use a bit of 8 or 10 mm. multiplait or dyneema, (more for comfort than strength) of a length to reach a jammer on top of the rear coaming. This will give you 12-1 more than enough to straighten the forestay when beating and easy to reach to pull on and off onehanded. The rig is almost too stiff to achieve much bend to flatten the mainsail but it will make some difference.
Of course if you are a gentleman and never sail to windward it is hardly worth the bother.

A cunningham is easy to fit and makes a big difference, well worth doing, if you have a spare clutch all you need is a bit of easily handled rope, thicker is more comfortable but the clutch will determine thickness.
 
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My boat has a divided backstay too; I fitted an off - the - chandlery - shelf ( albeit years ago ) a tensioner which consists of a triangular stainless triangle fitted point down, with brass sheaves on the outside of the backstay wires.

At the downward point there's a simple small single block.

A line ( in my case 6mm is fine ) runs from one backstay chainplate, up around this block, then down to a simple block and cam cleats at the other chainplate.

A pull on the line squeezes the backstay wires together and is very effective on my 7/8ths rig.

And it wouldn't get in the way of your boarding gate.

Sorry I can't put pics here or remember the make, but it's quite a common stock item, or used to be.
 
PeteCooper said:
Yes - you would be surprised how much mast bend you can induce to flatten the main.
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With our masthead S31 and a 24-1 purchase I am surprised at how little, but the OP's is the fractional version (9/10s?) but still stiff. To be honest I knew the rig design was out of date even for the nineties, but not too bothered anymore.
 
ghostlymoron said:
Is there any point in having a backstay adjuster on a masthead rig?
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Yes... Makes a big difference up wind... Cunninghams, good vangs/kickers, flat reefs, out haul, halyard tension, adjustable travler, movable jib cars also make a big difference.

However you can sail without adjusting any of these and still get reasonable performamce from the sails
 
temptress said:
Yes... Makes a big difference up wind... Cunninghams, good vangs/kickers, flat reefs, out haul, halyard tension, adjustable travler, movable jib cars also make a big difference.

However you can sail without adjusting any of these and still get reasonable performamce from the sails
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Couldn't agree more; I love bits of string to pull and tweak, the more the better !
 
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