Gooseneck fitting

[Stemar]

Jissel's a 1970 vintage Snapdragon 24.

A new main means I need to adust the height of the boom, which I'd raised as far as possible on my old slightly underheight but saggy main to allow it to clear the sprayhood. The gooseneck fits in an ally slide on the mast. Getting it without dropping off involved removing several rivets and a fair amount of brute force to remove the slide, and refitting it looks like having entertainment value for those sitting at a safe distance, so I'd like to make it more easily adjustable so I can keep the boom as high as possible while still keeping the luff under the right amount of tension as the sail stretches over the next few years.

I'm thinking of drilling and tapping the gooseneck so one or two 4 or 5mm SS bolts could be screwed into it to jam it in the slide. It's bronze and, where the bolts would go through, about 6mm thick. One bolt at the bottom would be easy, a second at the top would require surgery on the pin that holds the boom on, so I'd prefer to use only one if it's going to be enough.

It seems to me that sailing forces on the goosneck are almost entirely lateral; the biggest forces involved in trying to make it slide are the weight of the boom when the sail's down and the luff tension when it's up, neither of which is enormous on a small, modestly rigged boat. Would one be enough to keep it from sliding? If not, would would two work? I'm assuming I should use something to fight corrosion and keep the bolts from seizing, but chromate paste could lose it's efficacy if I slacken the bolts to move the slide, so I'm thinking of a good dose of ACF50 over everything. I could use copperslip, but I'm leery of introducing yet another metal into the equation.

Thanks in advance for your thoughts.

 

[winsbury]

Not the same as your boat admittedly but our early Wayfarer has a sliding gooseneck - its a right royal pain - the idea was that it could be raised to provide extra space when using a boom tent and pulled down when sailing as a kind of crude cunningham. What actually happens is that in a stiff breeze it almost always slips upwards in a big gust with the result sail shape suddenly becomes even more powerful. Modern Wayfarers all have a fixed gooseneck and most older ones have been changed to a fixed one.

As for strength, it doesn't need to be outrageously strong except in an accidental gybe when the forces suddenly transferred to the gooseneck are enormous shockloads, it is this that you should consider for engineering purposes and for that reason alone I would not drill the fitting or weaken it unnecessarily. If you really must have an adjustable height, rather than alter the gooseneck itself, could you not put a locking device into the track above and another below the gooseneck to fix it at whatever your desired height is ? If you make these in stainless and they simply clamp to the track in a similar fashion to boom slide fittings then you wont have much in the way of corrosion issues to worry about.

If Ive understood correctly the underlying problem is that you now have a proper (larger) sized sail which needs the boom lowering to set properly but that will then foul on the spray hood. Other ideas to consider -
* remove or alter the sprayhood;
* part-reef the sail;
* have the foot of the sail altered to suit the existing current boom position,
* install a cunningham to control luff tension.

 

[PetiteFleur]

If I read your post correctly, your goosneck is similar to the sliding goosnecks on sailing dinghies, which are usually fixed with a single thumb screw, which is sufficient to hold the gooneck in position(with the help of the kicking strap) I would fit the largest stainless screw you can fit in position. I assume you are tightening the luff by the halliard and not lowering the gooseneck & boom. I would lubricate the stainless screw with a marine grease which should make it easy to move when required.

 

[NormanS]

Not sure if this is entirely relevant, but many years ago when I had a Folkboat, the luff tension on the main was achieved by hoisting the sail, cleating the halyard, and then pulling the boom down with a tackle. Maybe instead of locking the boom you could use a small tackle?

 

[VicS]

Jissel's a 1970 vintage Snapdragon 24.

A new main means I need to adust the height of the boom, which I'd raised as far as possible on my old slightly underheight but saggy main to allow it to clear the sprayhood. The gooseneck fits in an ally slide on the mast. Getting it without dropping off involved removing several rivets and a fair amount of brute force to remove the slide, and refitting it looks like having entertainment value for those sitting at a safe distance, so I'd like to make it more easily adjustable so I can keep the boom as high as possible while still keeping the luff under the right amount of tension as the sail stretches over the next few years.

I'm thinking of drilling and tapping the gooseneck so one or two 4 or 5mm SS bolts could be screwed into it to jam it in the slide. It's bronze and, where the bolts would go through, about 6mm thick. One bolt at the bottom would be easy, a second at the top would require surgery on the pin that holds the boom on, so I'd prefer to use only one if it's going to be enough.

It seems to me that sailing forces on the goosneck are almost entirely lateral; the biggest forces involved in trying to make it slide are the weight of the boom when the sail's down and the luff tension when it's up, neither of which is enormous on a small, modestly rigged boat. Would one be enough to keep it from sliding? If not, would would two work? I'm assuming I should use something to fight corrosion and keep the bolts from seizing, but chromate paste could lose it's efficacy if I slacken the bolts to move the slide, so I'm thinking of a good dose of ACF50 over everything. I could use copperslip, but I'm leery of introducing yet another metal into the equation.

Thanks in advance for your thoughts.

A picture would have helped to understand th problem


You have a goose neck fitting which will slide in a track on the mast ?

You want to fix the gooseneck in position in such a way that it can be adjusted fairly easily as and when necessary?

How about a couple of track stops. One above and one below.

http://www.force4.co.uk/1749/Davis-Sail-Track-Stops.html

 

[Poignard]

Not sure if this is entirely relevant, but many years ago when I had a Folkboat, the luff tension on the main was achieved by hoisting the sail, cleating the halyard, and then pulling the boom down with a tackle. Maybe instead of locking the boom you could use a small tackle?

That's the arrangement I still have. it's a relic of the time when my boat had roller-reefing.

I like the arrangement. It's very quick and easy to hoist the main right up to the stop without needing a winch and then haul down the tack with the tackle to tension the luff, ie gravity is helping.

It's big advantage comes when getting away under sail. You can get the main up very quickly with the tackle eased right off, then when you're in open water, and have more time, you can go and tension the luff.

BTW I don't know why the goosenecks of roller-reefing booms were usually mounted on a length of track. Can anyone explain?

 

[William_H]

Almost as an aside I have made a connection to the head of my mainsail which gives the sail the max height. I am guessing that you have a halyard with a shackle onto the head board of the sail. If it is a rope halyard you could go for just a knot (bowline) of halyard to sail. This should give min lost height at the top.
In my case with a wire halyard with thimble in the end I put a bolt through the thimble that then goes through the headboard. Now this would give a lop sided pull to the headboard so I made a piece of stainless steel plate which has a slot in one end. The slot allows the thimble to pass through then when it turns sideways the end of the slot rests on the swage or end of the thimble. On the other end of the plate is a hole to match the through bolt. The end effect is like a shackle but with min lost distance between the sheave and the sail top. A simple thing that gives me 3cms more sail hoist.
Also as said if you have a cunningham to flatten the main in a blow you can cope with a slacker luff in light winds so gain yet more ability to cope with an over sized luff length. good luck olewill
Back to the problem of clamping the sliding gooseneck. Obviously it must have or had a lock which is usually a simple pin onj a spring. So I reckon one bolt should do the job.

 

[winsbury]

The slot allows the thimble to pass through then when it turns sideways the end of the slot rests on the swage or end of the thimble.

There is indeed usually space at the head to gain an inch or two by attaching the halyard differently but I would strongly advise against putting any pressure on the sides of a swage - the metal will deform and the swage will fail, Ive had it happen on a wire halyard that was pulled up tight in an F6 so that the swage rested on the masthead sheave, the result was a spectacular bang as the rig exploded followed by the genoa lying in the water on leeward side as we struggled not to be thrown overboard the windward side (only a dinghy so not as serious as a similar failure on a yacht might be but it surprised us all the same !)