Changing the Designs of Boats We Sail - A New Backstay...

[langstonelayabout]

This month’s (Feb 14) PBO has a case in point and one for which I’m just entering into an email discussion with my insurer…

The practical projects section has an item about a reader’s interest in a design of improved backstay adjuster used and shown within July 13’s PBO. Coincidentally, I’m about to update and improve the backstay on my Eolia 25 with a similar design…

However, will my design (or any other changes made to my boat away from those supplied by Jeanneau) automatically be acceptable to my insurer? Judging by the ratings of the fittings used for their 32 footer’s update, I over-engineered all 3 of my previous backstay upgrades to previous boats.

But what happens if it goes wrong? Will the insurer simply write to me and state that as I don’t have any documentary evidence of the upgraded design’s adequacy for the task (or any maintenance performed upon it) ‘they are unable to help me on this occasion’? (Effectively: I’m the design authority for the updated backstay, it failed so I take the rap for it)

Having already received one of these ‘insurer’s standard letters’ for a claim for which the design of the hull was inadequate, I’m still a little sore and wary on this subject.

What are your thoughts please? So we have to let our insurers know for each and every change we make to our boats? (Yes, this opens a real can of worms)

 

[JumbleDuck]

What are your thoughts please? So we have to let our insurers know for each and every change we make to our boats? (Yes, this opens a real can of worms)

If I was making a major change, like a new backstay system, I'd get a surveyor to approve it and send the approval to my insurance company with a note saying "How about this, chums?" If a surveyor wouldn't approve it, I wouldn't do it.

 

[prv]

Must admit that it wouldn't occur to me to consult our insurers before or after any changes. Albeit I haven't so far done anything major and structural to hull or rig. I suppose I did fit new shackles at the top of Kindred Spirit's shrouds (rigger cut them slightly too short, so I bought long-dee shackles) which could have brought the mast down if they'd been made of cheese. But they weren't, and they didn't.

I suppose one should check whether they're interested, and it's a matter of judgement what level of change it's sensible to ask about. Sure they're not interested if your missus buys different colour curtains

Pete

 

[Seajet]

The snag with this is unless the insurer is sympathetic and knows one end of a boat from the other, when asked about making the slightest change they're bound to say ' get a surveyor to approve it ' which is not cheap.

 

[William_H]

I guess much depends on the age of the boat. My little boat is on it's 4th mast several changes of rigging sails etc. Furhther with my kind of boat still in production after 35 years it is said no 2 Castle 650s are identical. ie the design details kept changing. So I would be surprised if any insurance man or surveyor could say it was not as built. Almost everyhting has been replaced anyway. Not so easy on a new Juneau.
However there are standard design ways of doing things. So they would be hard pressed to argue against a standard design. (as an excuse to decline a claim)

Anyway backstay tensioners for a 25 fter would come in 2 styles. Both assume a split backstay so that tiller can operate unhindered between the backstay legs. They usually join (fork from one to 2) about 1.8 metres above the transom. So usually for a mast head rig these 2 legs will be pulled down so distorted together by a pair of plates containing sheaves. This box is pulled down by a small tackle. Any failure of this box will leave the backstay naked but still intact.
Perhaps more common on a fractional rig where more range of adjustment is needed )and perhaps the backstay is not so critical to mast staying upright) The single backstay is terminated with a metal sheave pulley about 1.5 metres above the transom. A flexible wire (or dyneema) runs from one side of the transom up through this pulley down to a tackle (4 purchase) to the other attachment at the transom. A safety strap may be fitted to limit the release of the backstay in case of failure or release of the tackle.
If you have a single backstay to a single attachment on thetop of the transom you might consider calmping another wire 2 metres iup the bbackstay and adding a tackle to tighten by shortening this section of backstay.
IMHO all these methods would be failsafe and standard design so acceptable to insurers. But then who knows. good luck olewill

 

[lw395]

It should be fairly easy to show that the backstay fittings are adequate.
Take the SWL of the wire and calculate the load on the adjuster components.
You can always put a loose wire from the rigging wire to the transom fitting, so that failure of the tackle does not lose the mast.

If we are talking of a fractional rig, putting in too powerful a tackle and breaking the mast may be more of a concern.
Or of course distorting the boat or overloading some other part of it.

I'd be more concerned about a boat where nothing had been upgraded or replaced since it left the factory.

 

[langstonelayabout]

I'd be more concerned about a boat where nothing had been upgraded or replaced since it left the factory.

I must agree: the existing backstay setup is poor and not in good condition: even the surveyor said so! It is a single backstay from the masthead with a block and then wire running from one quarter, through the backstay block, to a 4:1 rope purchase on the other quarter.

I'm looking to shorten the wire backstay by a metre or two and make everything below it 6mm dyneema and running through a cascade to make it 12:1.

I suppose in principle that the design hasn't changed, has it? I don't want to put any fail-safes on the new backstay system as the system is stronger than the current 4mm 1x19 wire used over the rest of the boat and the boat's designer didn't rig fail-safes for the shrouds or forestay, did he?...

 

[lw395]

The shrouds and forestay don't run around blocks.
If you make the first stage of the cascade plenty strong, and arrange it so it will keep the mast up after a fashion if the rest of the cascade disintegrates, it should be OK, provided the block is suitable for the dyneema.
Personally I would have a high safety factor on that bit of dyneema, it does not cost much more, in either cash or windage.
Possibly still best to change it every few seasons though.

 

[langstonelayabout]

The shrouds and forestay don't run around blocks.
If you make the first stage of the cascade plenty strong, and arrange it so it will keep the mast up after a fashion if the rest of the cascade disintegrates, it should be OK, provided the block is suitable for the dyneema.
Personally I would have a high safety factor on that bit of dyneema, it does not cost much more, in either cash or windage.
Possibly still best to change it every few seasons though.

My old E-Boat was the first backstay I upgraded. I used Rutgerson blocks with SWLs of >1 tonne and 12-strand 6mm Zylon (breaking av = 4360kg). The Zylon was changed it every 2 years (got it cheap in an end of reel bin!). The rest of the rigging was 4mm 1x19 wire.

No way did that mast come down whilst in use: even with the slightly-oversize quarter-tonner spinnaker in use on an exciting day or the old 18-foot skiff asymmetric in use on a reasonable day...

I'm sure that I can use similar maths and loadings for my Eolia; after all, it too has 4mm 1x19 wire rigging as standard... Anyone agree/disagree?

 

[William_H]

Hello Langstonelayabout. As suggested if the you use cascade system then it can be made at least partially fail safe by carefully choosing the lenght of the line that runs from one quarter through the pulley back down to the final tackle. ie if the final tackle is let go then the pulley of the final tackle will not go through the pulley on the end of the line going through the block on the backstay. ie set it up so the loosest the backstay can be is still tight enough to hold the stick up.
My concern might be the life of the rope in UV and especially how insurance company might view just that. good luck olewill

 

[wklein]

It is fairly unusual to see a boat with in line spreaders and a masthead rig with a block and tackle for the backstay. I guess as its a fairly small boat its prob well within safe limits.

I would not be at all concerned about changing from 8:1 to 12:1. (not sure how you got 12:1 if you add another cascade you get 16:1)