Do I Need a Backstay Tensioner ?

[MarkJ]

I still think a pro needs to see this boat.
Its a racing boat of the highest order of its time.
Ben Lexan (previous name Bob Miller) the designer of Australias sucessful Americas Cup winner in 1984.
Ben Lexcen - Wikipedia, the free encyclopedia

He then went on to design a one design racing class of which the 40 is/was part. There was also one called the Olympic 40 and I think, but don't remember/konw if its this desing with the name change to bens (assumed) surname.
They were built in the 1980's.

So this is an extreme racer (or was by design or build - we dont know the specifics). If it is the mast might be a spaghetti string that actually needs special considerations... or indeed a previous owner may have changed the setup oor changed masts etc.... or I might just be talking crap

So akio.kanemoto might need to tell us its full history, iof available or show the problem to a person who is expert in these boats - and theres plenty in Sydney.

[Sparohok]

Originally Posted by Stillraining

Im mast head and I can put a foot of bend in my mast with back stay tension alone

OK, I stand corrected....

Can you explain how that works for me? What is the backstay working against to bend the mast?

On a fractionally rigged boat, as you add backstay tension, the masthead moves back, the midpoint of the mast moves forward, and the headstay attachment is more or less stationary. The backstay is working against the forestay to bend the mast.

On your Irwin 41 the shrouds should keep the midpoint of the mast stationary, so I don't see how the mast could be bending in compression. Is the masthead moving back? How is that possible with the forestay attached at the masthead?

Martin

[Stillraining]

Dosent look all that radical to me by today's standards but what do I know..

photo gallery popup with enquiry

[akio.kanemoto]

You really know your boats.

Not sure that it's an Olympic 40 - the only pic of that I could find is here:

OLYMPIC 40 boat details - BoatPoint Australia

...and that's not it. I've attached a pic of mine to this post.

OK, history as far as I know is it was built by Keith Revell in 1985. I believe it was called "Leverage" when launched, but am unsure. I bought it as "Kylie Jean" from a fellow who clearly didn't like maintenance... for luck/superstition, I've renamed it back to Leverage.

Hull is foam sandwich and so is the deck - not bad for '85...

Keel is a moderate winged keel. ~8ft draft.

Mast is not the original - I have no idea what the original was..

I'm pretty sure though that the hydraulic backstay adjuster was on the original.

Interesting fact - maybe this is normal - but the forestay chainplate tang is 12mm thick, whereas the backstay is only 6mm.. go figure.

Oh, forestay tang which the toggle attached to is visibly distorted... I'm thinking that the PO was obviously having too much sexytime with the backstay hydraulics or doing silly things in too much wind.

Boom is pretty stupidly long/low @ 4.5m long.. gotta raise it..

PO had whizz bang sails.. but didn't bother to have a (working) bilge pump... or bow roller... or anchor...

Shrouds are very close inboard for silly sheeting angles, a little bit scary thinking about the physics/leverage involved... (although those chainplates are about 1.5m long and very solid(!))

Hull shape is pretty sleek, not very beamy at 3m max.. IOR shape, zero buoyancy at the stern.. reverse transom... huuuuuuge deep spade rudder with a 75mm solid post (not a modern foil though...)

...

err... more about the boat's history... no idea.

Before I started the refit, I did sail it a bit and it was v.fast... too fast for my liking... Could have had to do with the stupid sized sails it has... but I can certainly remedy that.

On the "pro seeing the boat"... the boat is currently not moving.. mast currently out and engine "out of action" for the moment (new tanks coming...)

I'm up to the backstay only because I've more-or-less finished up inside and am fairing the cockpit floor and will be up to deck painting soon... which means that in a few weeks, I hope to FINALLY have the mast back in... which means I need to decide what to do with the tensioner.

Originally Posted by MarkJ

I still think a pro needs to see this boat.
Its a racing boat of the highest order of its time.
Ben Lexan (previous name Bob Miller) the designer of Australias sucessful Americas Cup winner in 1984.
Ben Lexcen - Wikipedia, the free encyclopedia

He then went on to design a one design racing class of which the 40 is/was part. There was also one called the Olympic 40 and I think, but don't remember/konw if its this desing with the name change to bens (assumed) surname.
They were built in the 1980's.

So this is an extreme racer (or was by design or build - we dont know the specifics). If it is the mast might be a spaghetti string that actually needs special considerations... or indeed a previous owner may have changed the setup oor changed masts etc.... or I might just be talking crap

So akio.kanemoto might need to tell us its full history, iof available or show the problem to a person who is expert in these boats - and theres plenty in Sydney.

[akio.kanemoto]

That one is another Lexcen 40... which was one that he designed as a cruiser - it is WIIIIDE and was quite popular with the charter fleet. Not mine though..

Originally Posted by Stillraining

Dosent look all that radical to me by today's standards but what do I know..

photo gallery popup with enquiry

[MarkJ]

Originally Posted by Stillraining

Dosent look all that radical to me by today's standards but what do I know..

Are you trying to say the designer of the boat that won the Americas cup off YOU just designs run of the mill non-radical boats?

Then it must have been the better sailors that won the Americas Cup!







It beats the better legal team winning the cup...

[Stillraining]

Originally Posted by Sparohok

OK, I stand corrected....

Can you explain how that works for me? What is the backstay working against to bend the mast?

On a fractionally rigged boat, as you add backstay tension, the masthead moves back, the midpoint of the mast moves forward, and the headstay attachment is more or less stationary. The backstay is working against the forestay to bend the mast.

On your Irwin 41 the shrouds should keep the midpoint of the mast stationary, so I don't see how the mast could be bending in compression. Is the masthead moving back? How is that possible with the forestay attached at the masthead?

Martin

The forward shrouds basically do the same thing as far as keeping the center of the mast from moving back. Not to the same degree of a fractional of coarse..but a fractional rig can get more then a foot of bend for sure.

What allows the mast head rig to come back is simply taking the belly out of the fore stay as much as you dare...This is where tweaking can be of great advantage from fully slacked for light wind performance allowing the head sail to power up, to bar tight for heavy weather pointing ability with as tight a luff and inboard sheeted as you can get.

The taller the rig the more you have to play with.

[MarkJ]

Originally Posted by akio.kanemoto

Keel is a moderate winged keel. ~8ft draft.

err... more about the boat's history... no idea.

The CYC website has a list of all the Sydney Hobart entries, etc. You could have a look and pice some more history together
Check with RPAYC too as it raced in the Coffs Harbour race from there in 2002/3 as Kylie Jean.

I'd still pay a rigger $100 for an hour to look (but they charge traveling time too, so depends where you are etc)

[Stillraining]

Any boat will sail with or with out back stay adjustment..I just wanted to show you that big pig condos can benefit from that ability as well...Even mast head....And IMHO it can be safer in some instances.

We we out in 47 knots with just a sliver of the 135 showing...the for-stay was trashing around like a line caught bass...I would have applied back stay in a heartbeat if I could have....crawling around on hands and knees with wrench and srewdriver adjusting turnbuckles aint happening in that situation.

Seems to me if your boat was designed with the ability it should retain it....it aint all just for racing is the point I'm trying to make.

[Sandero]

Before deciding what sort of control you need, you need to have the rigging plan. Where are the spreaders, the shrouds connected, how many are there, are the swept back or not, is the rig a fractional or masthead, is there an inner forestay and so forth, not to mention the type of sailing you will do and in what conditions.

Tensioning a backstay will do different things in different rigs, so there is no one size fits all answer here.

Can you at least provide a plan and elevation view of the boat (rig)?

[akio.kanemoto]

Originally Posted by defjef

Before deciding what sort of control you need, you need to have the rigging plan. Where are the spreaders, the shrouds connected, how many are there, are the swept back or not, is the rig a fractional or masthead, is there an inner forestay and so forth, not to mention the type of sailing you will do and in what conditions.

Tensioning a backstay will do different things in different rigs, so there is no one size fits all answer here.

Can you at least provide a plan and elevation view of the boat (rig)?

Unfortunately I have no pics of the rig.. didn't think about it at the time..

But, no inner forestay, standard masthead sloop, single backstay. Two sets of spreaders, only very slightly swept back (almost not really)..

Sailing - cruising, all around the world... slowly.. can't guarantee weather, but I will certainly be appropriately cowardly.

[Jimbo2010]

Wow I didn't expect this much resistance for the need for a backstay adjuster. Sailing for 35 years I assumed everyone used them.

When the wind is us up say 15-20+ with waves, go stand at the side of the mast and watch the mast center pump back and forth with a soft backstay. That is a big risk, older boats used baby stays to stop it.
NOw better designed rigs use the backstay adj.

Each time it pumps ie; out of column, the mast is shorter overall, the result is the headstay sags off to leeward, the lee shrouds get slacker. ( all wearing the connecting parts unnecessarily) The mast head also falls off to leeward, resulting in excess heel.
Go to the bow and take a spare halyard to the tack fitting now sight up and see how far the headstay is sagging, this produces more heel less forward thrust the draft in the jib is moved aft. Most sails depending on the size of the boat are designed to sag 6-15", lets use 12" as an average.

I bet some of you guys advocating no need to adjust would show 24" plus.

So your stick is pumping, the loads are be transferred all over the boat rather than being in a stable locations all bad for the hull flex & rig, I guess you guys never saw a stick go down, it is due to one of those parts not being stable rather wiggling around wearing and failing.
This is to say nothing of the strains on the spreader tip to shroud and spreader attachment point on the stick.
When the stick pumps also look at the main the draft is pumping fore and aft wearing/flexing for no reason.

These masts were designed to remain stiff in column that doesn't mean straight it means with bend fixed for the wind and sea conditions.

Now all this in practical use is simple, 4 settings will suffice.

U can use the pressure gauge on hydraulic rigs.

But those with a cascading or other mechanical means just mark the line or attach a small stick or rod with 4 points to measure quickly.

0-8
9-15
15-22
22+

In each of those wind speeds check pumping and headstay sag, not the pressure or measurement otherwise.

I surmise that many of you are reefing do to excess heel way too early, before U reef,
crank the backstay, the boat will stand up by depowering the main, tightening the headstay will move jib draft forward and the entire rig to windward.

I know you're not in a rush, if your stick crashes to the deck just pray no one gets hurt or worse.


Now should I ask how you set the mast up to begin with?
How do U find if the stick is centered port/star?
How is the initial rake in the stick checked?

I know you're not in rush but since you're not in rush & have soo much time set the boat up right.

I hope I didn't waste my time,
I saw 3 sticks go down over the years, don't know Y but it isn't pretty. If you're off shore it must be ugly.

Ps: NO turnbuckes can not do it they weren't designed to turn under these types of loads the threads will gall and fail.

[Sandero]

Surely mast pumping is a not something you want. Slack rigging is the rigging which will fail at the swages or connections to the end fittings.

The issue is how to tension your rig and under what conditions you need to consider doing this.

Shiva is a fractional with swept back spreaders and uses a 12:1 block and tackle to apply back stay tension. We also have runners.

Tensioning your mast will remove slack in the forestay and flatten your main which will ease weatherhelm and heel.

You can find a few alternate means to tension (block and tackle, Dermac type adjuster or hydraulic) your backstay and it is advisable to have that option.

[barnakiel]

A word of warning - a mast alloy extrusion, no matter how fat, is NOT designed to take lateral pull. In well designed rig, the forces are balanced and converted to compression (mostly). Any load carrying stay must be balanced.

Do not look at your stick and say 'doh, it is very fat, it will take some side load' . For it will NOT.

b.

[Sandero]

In fact it is interesting to understand how the force of the wind is transferred to hull resulting in motion through the water.

The wind forces acting on the sails are transferred to the hull via:

standing rigging (chain plates)
the spar (mast partners or step)
boom
gooseneck fitting
vang
the sheets
turning blocks
lead blocks
winches
halyards

If you examine the head sail forces... they enter the hull via the mast, the fittings where the forestay connects to the hull, the genoa car, the turning block and the winch.

The headsail forces coming into the mast at the top of the forestay are then transferred to the hull via the partners or step and the windward standing rigging to the chainplates and backstay.

YIKES