Broken spinnaker crane

[ANDY_W]

I recently approached a rigging company to organise the supply and fitting of an extended spinnaker crane. The idea was to be able to use a light airs sail which could be furled after use without any chance of it fouling the roller reefing foresail.
My initial concept was of a horizontal ' u ' shape made from stainless steel tube projecting forward from the top of the mast with two legs running down from the outboard end and bolted to the mast to take the vertical loads.
Their view was that my idea projected too far forward and could apply too high a turning load to the top of the mast ( despite the effect of the forestay and backstay ). They suggested that a custom made top hat section with a base as wide as the masthead and not projecting as far forward would do the trick.
As you might guess from the heading, their fabrication has bent vertically down in the direction of the bow instead of sticking out at a right angle from the top of the mast. This occurred on the second time that I used the sail, in conditions which were generally light with mild gusts with the boat on a close reach. A sudden stronger gust came which heeled the boat to between 10 and 15 degrees, this with the mainsail and light airs sail up together. At this point I saw that the luff of the light airs sail had become much more slack and found the reason.
The boat is a Westerly Longbow and the light airs sail is about 360 square feet and designed to have some windward ability.
The problem is that I am uncertain as to exactly how I stand.
Can I reasonably act on the basis that the professionals should have known what was required?
Was the sail larger than could reasonably be expected?
Obviously I need to have a conversation with the riggers but need to decide how to approach the matter.
Any advice or suggestions would be gratefully received.

 

[Neeves]

I recently approached a rigging company to organise the supply and fitting of an extended spinnaker crane. The idea was to be able to use a light airs sail which could be furled after use without any chance of it fouling the roller reefing foresail.
My initial concept was of a horizontal ' u ' shape made from stainless steel tube projecting forward from the top of the mast with two legs running down from the outboard end and bolted to the mast to take the vertical loads.
Their view was that my idea projected too far forward and could apply too high a turning load to the top of the mast ( despite the effect of the forestay and backstay ). They suggested that a custom made top hat section with a base as wide as the masthead and not projecting as far forward would do the trick.
As you might guess from the heading, their fabrication has bent vertically down in the direction of the bow instead of sticking out at a right angle from the top of the mast. This occurred on the second time that I used the sail, in conditions which were generally light with mild gusts with the boat on a close reach. A sudden stronger gust came which heeled the boat to between 10 and 15 degrees, this with the mainsail and light airs sail up together. At this point I saw that the luff of the light airs sail had become much more slack and found the reason.
The boat is a Westerly Longbow and the light airs sail is about 360 square feet and designed to have some windward ability.
The problem is that I am uncertain as to exactly how I stand.
Can I reasonably act on the basis that the professionals should have known what was required?
Was the sail larger than could reasonably be expected?
Obviously I need to have a conversation with the riggers but need to decide how to approach the matter.
Any advice or suggestions would be gratefully received.

I thought to refresh your thread.

Go and buy a mobile phone, they all have cameras now. Take some pictures, showing all the facets and you might engender useful replies. Some of us, not me, are really clever but sometimes we, me, are slow to understand.

Apparently a picture, or maybe a photograph is worth a 1,000 words - especially if its a complex or novel problem.

The other way to solicit comment is to mention anchors - and then you will be buried with replies.



Jonathan

 

[Ingwe]

Assuming that you told the rigger that the sail was designed to have some windward ability I think a more experienced rigger would probably have said no to the whole idea as the torsional loads on the top of the mast are going to be hideous - I am sure it would be possible to reinforce enough with a lot of stainless steel or carbon fibre, but I could envisage if you did that it causing issues using the backstay.

If you need more seperation bewteen the spinnaker and the foresail do it at the bottom ie with a small bowsprit, but again if you intend to fly any sail that iss capable of going slightly to windward it needs to be stronger than the charts will say and will need a bobstay.

 

[Neeves]

I am sure it would be possible to reinforce enough with a lot of stainless steel or carbon fibre, but I could envisage if you did that it causing issues using the backstay.

Stainless steel, 316, is not particularly 'strong'.

Jonathan

 

[ProMariner]

Had it been strong enough to resist the massive luff loading of a tight luff sail going to windward, it would probably have broken your mast instead. There is a big difference on the load a spinnaker sailing downwind in the kind of wind spinnakers are usually used in puts on the halyard, and the load a tight luffed sail puts on the halyard, which is kind of like a halyard and a forestay combined.

I wouldn't use a big new code zero on your old mast at all, something's going to give, and it'll be expensive. Just accept the rig was designed to be used with a huge overlapping Genoa, and stick with conventionally hoisted spinnakers or cruising chutes for a little extra fun. Snuffers are vastly under-rated for these sails, and modern furlers on loose luffed sails are vastly over-rated in terms of ease of use and reliability.

 

[ANDY_W]

Many thanks to all who took the time to respond.
To cover points raised in the responses:
I have a detachable bowsprit with bobstay, I was trying to get more clearance at the masthead to eliminate potential fouling with
the foresail roller reefing gear.
I did discuss the torsional loads with the rigger. His construct failed downwards, not sideways.
There are polar diagrams showing the range of use of four common light airs sails, which are code 0, gennaker, asymmetric
spinnaker/cruising chute, and spinnaker. Of those the first three have some windward ability ranging from 50 to 70 degrees off the wind. I have not seen any recommendation for re-inforced mast/rigging in relation to their use although I am quite happy to be corrected if such advice exists.
My original purpose for starting this thread was to perhaps glean some ideas for dealing with the rigger. I am in the position of being a moderately knowledgeable amateur having to deal with a professional in his trade. I don't have enough depth of knowledge and experience to know what may or may not be a reasonable position to take by either side.
Any advice or observations in that respect would be most helpful.

 

[Ingwe]

By all means try and get some level of refund from the rigger as it wasn't fit for purpose.

It doesn't surprise me that your crane failed vertically as I am assuming you have some form of anti-torsion cable on the sail - if you have that taught enough to do a good furl it is acting as your forestay and almost certainly has nearly zero stretch so everything it is attached to has to be able to take the shock loads that occur when the mast moves backwards and forwards when you hit a wave / go through a big wake.

Boats regularly need to make changes to their setups to accomodate Code 0 sails, it's quite common to add some form of running backstays setup if the spinnaker halyard exits well above the shrouds, the spinnaker halyard often needs uprating to cope with the loads - sometimes hvae to go 2:1 to get enough halyard tension and clutches again often need uprating. Some of these problems are now partly being solved as there are now "Cable less" code sails available which signifficantly reduce the loadings.

 

[ANDY_W]

Ingwe, thanks for the lesson about beefing up for code 0's etc; every day's a school day!
I thought about a top down furler but opted to have a sail built with a dyneema luff rope mounted on a straight luff furler.
It's made from heavy duty spinnaker cloth so that I can just stuff it into a sail bag if necessary.
I've only used it three times but it seems to work. It does require a certain amount of luff tension but hand tight seems to be enough.
I understand about the shock loads but am not planning to use the system in anything more than F3 so the probability of catastrophic shock loads should be small. I'm a coastal sailor not in the first flush of youth so would only use this type of sail in conditions which allow me to cope if the handling system failed to work.

 

[doug748]

At one stage I extended my spinnaker halyard about 6in forward of the mast and it proved ok for light work. I used c1in alloy square section tube into which I drove a square of teak so it was effectively solid. The masthead casting was flat so it was easy to through bolt it.

I think the best you can do with your rigger is to ask him to beef the job up or redo it. You will probably just have to put up with the annoyance factor

.

 

[ANDY_W]

Doug, it's annoying that the fitting has failed, but what's really annoying is that my original concept included vertical braces which would have prevented what has happened, but was discarded for the " professional " solution.

 

[dunedin]

As noted, some pictures would help a lot.

But also if specified for a “spinnaker” would be very different from if specified for Code 0 or similar sails.
Some yachts with integral bowsprits (often those without support stay) have instructions that the end can be used for an asymmetric tack line but the Code 0 needs to be attached closer to the bow.