Boom Connections

[Sandy]

The mast is coming down in January for a major overhaul.

While it is down I am looking at changing the way the boom is connected to the mast. It is currently a cylinder with two holes drilled in it and two pins through the holes.

While it works I am not 100% comfortable with the set up.

What do others use?

 

[dansaskip]

I use a standard Seldon gooseneck arrangement. I think it is type 508-040-070 if you look at the Seldon catalogue. Might give you some ideas for alternatives:
Aluminium booms : Seldén Mast AB

 

[DanTribe]

A few more details, such as; size of boat / rig. mast manufacturer or even a photo may help you get some helpful suggestions.
The Selden catalogue is often a good place to start. www.seldenmast.com. Don't be put off, they don't only deal with superyachts.

 

[ridgy]

I once replaced a broken gooseneck on an older mast with a z-spars standard part and it fitted well.

Unless the current arrangement is showing signs of failure it seems an odd thing to worry about. Presumably whatever is there has been there for a long time and was put there on purpose.

 

[Sandy]

The boat is a French Gib'Sea built in 1986. The mast manufacture is a French Z-Spars.

It is nothing complicated in engineering terms. The mast has a hinge with a hole in it, the boom has a fitting with a gap between two bits of metal with a hole in them. You place the boom level with the hinge and pop the 'pin' through. The pin is held in place by two split pins. I am less than impressed, but she has been out in a F9 and I am still here to tell the tail.

I theory a bolt with a nyloc nut or a big clevis pin with a split pin will do the same. I wondered what others were using as I don't have a habit in inspecting everybody's masts when I clamber onboard, I'm more interested in getting the kettle on.

 

[Tranona]

If you did inspect other masts you would find that arrangement pretty common, However I agree having a split pin top and bottom is maybe not as good as a clevis pin with its solid head at the top and split pin at the bottom. That is what is on my boom

 

[Sandy]

If you did inspect other masts you would find that arrangement pretty common, However I agree having a split pin top and bottom is maybe not as good as a clevis pin with its solid head at the top and split pin at the bottom. That is what is on my boom

Thanks @Tranona. The arrangement is horizontal not vertical. I'll look at what I can see off the shelf or have a chat with a few fabricators.

 

[Daverw]

Ours is exactly the same Z Spars France, never gave us any concern, again a pin with washers either side with split pins to hold. It’s a fairly loose fit but thats the same as I’ve seen on many other boats.

 

[colind3782]

Likewise, we have the same fitting on our Furia 332. The hinged part was worn after ?35 years so I sourced a replacement from Z Spars for £150 and replaced it. I really don't see a problem with it.

 

[Stemar]

That setup has survived since 1986, and seen you through some nasty conditions, so ISTM that the design can't be too bad.

I'd actually be more concerned with a nut and bolt, even a nyloc not as there's an, admittedly small, risk of it working undone because it needs to be loose to allow the boom to move. That isn't going to happen with a washer and split pin. If you're concerned about the strength of the arrangement, put a clevis pin with its washer and split pin in a vice and see how much force it takes to push the washer off.

 

[Blue Seas]

Palm fronds work quite well, use a bit of pig-skin to absorb the friction. Oh, and if going south of Drake's Island be sure to wear a Lei.

 

[Sandy]

Thanks for all your comments. While the pin and two split pins have worked for some time I am not happy with the arrangement.

 

[Tranona]

Without saying WHY you are unhappy with the design it is impossible to suggest any alternative that will remove the unhappiness. Surely as an engineer you should have little difficulty in articulating what the deficiency is?

 

[RunAgroundHard]

Gooseneck bracket on the mast with two lugs each drilled vertically. Boom has vertical cylinder that can articulate longitudinally on the boom, the cylinder fits between lugs. Pin with rams horns drops through the lugs and cylinder, with nylon and stainless washers at the top and nylon and stainless washers at the bottom, nut on pin, split pin back up on the nut, which is a Nyloc.

It is E170, second from the bottom. Boom brackets : Seldén Mast AB

One thing you could do, if you have doubts, is to have the fittings NDT with dye penetrant. There are DIY sets, or if there are NDT inspection companies near by, maybe low enough cost. That could put your mind at rest.

 

[dunedin]

Thanks for all your comments. While the pin and two split pins have worked for some time I am not happy with the arrangement.

Why not post a photo of your gooseneck. Might reduce the guesswork.

 

[Sandy]

Without saying WHY you are unhappy with the design it is impossible to suggest any alternative that will remove the unhappiness. Surely as an engineer you should have little difficulty in articulating what the deficiency is?

In my humble opinion two small split pins holding a 50mm by 5mm diameter cylinder of metal in place is just not secure enough.

Personally, I'd like this part to be seriously over engineered.

 

[RunAgroundHard]

They are well secure but like everything else need to be checked periodically, as stuff does wear. Split pins are stated in Reliable Securing manual and part of a good dropped objects prevention scheme. Unless there is something that you see that is untoward, I would believe that the pins are good enough.

DROPS Reliable Securing Booklet Rev 04 › DROPSOnline

Over engineering isn't always good, as additional mass can lead to stiffness for example, that causes undue wear or strain. Then again, it may be no big deal to oversize or convert to a threaded arrangement and nuts.