Boom end fitting

[Ian_Edwards]

I need to take the boom end fitting of my Seldon boom to replace the reefing lines. The boom end fitting is the usual cast aluminium.

The Seldon Website shows the boom end fitting is retained by four M6 CS set screws, however the previous owner has replaced the set screws with pop rivets.

I'd normally drill the head off the pop rivets and punch the old rivets out, but I'm wondering if the pop rivets will have expanded into the original M6 threads, making them difficult to drift out.

Can any one make a guess as to whether this is likely to have happened?

The alternative is to drill the rivets out and then use a Helicoil inserts. Is this likely to be successful?

I don't want to put the boom end fitting back with pop rivets I really need to be able to access the single line reefing system without having to resort to a drill.

 

[sailorman]

drill em out & replace with same

 

[Martin_J]

or drill them out and put stainless Rivnuts in...

 

[duncan99210]

Drill out the rivets. If you're lucky, the threads will still be there in the boom end piece. If the threads are knackered, drill out to the next size up and tap in new threads with a tap set. The boom end piece is alloy, fairly soft and should be easy to tap.

 

[vyv_cox]

When I did exactly the same job, although on an older Selden boom that was pop riveted from new, I replaced them with Rivnuts. It is not normally necessary to maintain in-boom reefing systems but if an enthusiastic crew member pulls all the lines out at the end of the season it is useful to be able to get inside fairly easily.

 

[Deleted member 36384]

I need to take the boom end fitting of my Seldon boom to replace the reefing lines. The boom end fitting is the usual cast aluminium.

The Seldon Website shows the boom end fitting is retained by four M6 CS set screws, however the previous owner has replaced the set screws with pop rivets.

I'd normally drill the head off the pop rivets and punch the old rivets out, but I'm wondering if the pop rivets will have expanded into the original M6 threads, making them difficult to drift out.

Can any one make a guess as to whether this is likely to have happened?

The alternative is to drill the rivets out and then use a Helicoil inserts. Is this likely to be successful?

I don't want to put the boom end fitting back with pop rivets I really need to be able to access the single line reefing system without having to resort to a drill.

It will not have expanded in the threads. The pop rivet mandrel expands the rivet that is in free space, as the two sections are clamped together the end being forced apart by the mandrel expands against the outside of the material, the mandrel should not enter the section of rivet in the hole. At some point the mandrel head shears off and falls into the space on the inside i.e. it never gets to expand the section of rivet passing over the threads.

Now, if the wrong size of rivets have been used, then perhaps the mandrel did pass through, but then the rivet would not have clamped the boom ends to the boom firmly at all. The force would have been insufficient to force the rivet metal to flow into the thread space. I would aim to partially ream away some rivet material and then try to knock them out by folding up and edge after you have filed the head off. I think you find the threads are OK unless trapped water has corroded the hole.

 

[Ian_Edwards]

Thanks BlowingOldBoots, I very useful reply, it reflects what I thinks. I'll try the drill the head and punch the rivet out first, then see if the thread in the casting is usable and try running an M6 tap through it. If it's too corroded or stripped (and that may be the reason why pop rivets were used by the previous owner), I'll probably go the helicoil route, simply because I already have a M6 helicoil kit. I could use Rivnuts, but I don't have the insert tool or Rivnuts.
Thanks for your help.

 

[wklein]

Only the newest selden booms have machine screws as standard on the outboard end, these have a recess for a nut so there will be no tapped thread. The older kemp style ones are riveted both ends generally but this partly depends on who puts them together. They will be quarter inch rivets which are monel which is far less prone to corroding the alloy. if you have access to a rivet gun which will pull quarter inch rivets i would re rivet them. Otherwise you will likely need to go up to m8 or helecoil / rivnut them which is unneccisary unless there is play in the holes. I am assuming it is an older boom with single line reefing, when its open check the plastic wheels on the stainless cars as these falling out is a common cause of problems.

 

[Ian_Edwards]

Thanks for the info' about the Seldon booms, I wasn't aware of the possibility of captive nuts, I've just looked at the diagrams on the Seldon website and noted the M6 CS bolts, item 46 on the diagram. I can't see any captive nuts, nor are the listed in the parts list.

I'm not sure what you mean by newest?

This boom dates from 2007 or 2008, is that new?

I'm aware of the plastic wheel problem from previous post on this forum, so I was going to check them when I take the boom end fitting off.

I'm keen to get a relatively easy way to access the single line reefing, The only way to access one end of the leach/roach reefing pennant is to take the boom end fitting off and I like to take the reefing lines off to clean them at the end of each season.

I've got a Lazy Tongs Riveter, so 1/4" rivets aren't a problem if I need to resort to pop rivets and I wouldn't use anything other than Monel rivets on a Aluminium boom.

 

[duncan99210]

My Selden boom dates from 2000 and has threaded holes in the boom end piece, 6mm I think. I'd just drill out the rivet heads and drift out the rivets: as others have said, the threads will almost certainly be there waiting for you to use.

 

[rob2]

I can't see that there is much load on these rivets, so even if they are gripping in the hole rather than against the back/inner face of the end casting they will do the job so long as they stay in place. Once the outhaul is applied, they are redundant. So long as there is enough thread left for the screws to grip, it would be adequate to fit them with some Loctite. I'd suggest using socket head screws if you can get them so as to provide a good grip to break the Loctite's grip when next disassembling. Bearing in mid the boom and casting are both aluminium alloy, I'm not entirely convinced that Monel rivets are neccessary as opposed to standard aluminium ones, though. More of a corrosion problem with screws, which will be stainless into aluminium and can be expected to seize in as the aluminium corrosion products exert great pressure with expansion.

Rob.

 

[Ian_Edwards]

A quick update.

Just back from the boat, we took the boom end fitting off, by drilling the head off the pop rivets and punching the old rivets out.

The original tapped holes where there, but the previous owner had drilled new holes for the pop rivets. so the aluminium casting know has 2 sets of holes in it.

We used 6mm Helicoils to provide a threaded hole for the cheese head set screws, and all that worked OK.

I checked the condition of the wheels of the single line reefing sliders, and as I suspected the are knackered, as you can see from the photograph.

I know I can buy 8 of these from a Selden agent, but they'll be expensive for what they are, and in my opinion, a very poor design.

Has anyone out there sourced a better alternative? Preferably a set of wheels which has a better bearing surface than "plastic" on a very thin (2mm?) aluminium sheet.

 

[eddystone]

Thanks BlowingOldBoots, I very useful reply, it reflects what I thinks. I'll try the drill the head and punch the rivet out first, then see if the thread in the casting is usable and try running an M6 tap through it. If it's too corroded or stripped (and that may be the reason why pop rivets were used by the previous owner), I'll probably go the helicoil route, simply because I already have a M6 helicoil kit. I could use Rivnuts, but I don't have the insert tool or Rivnuts.
Thanks for your help.

I am in the same situation with a Kemp boom; you say rivets will be quarter inch (4.8mm?) but they also come in different lengths -I wonder what length to use as I want to buy the rivets in advance rather than have to take off the boom and then make a trip to the chandlers

 

[nigelmercier]

When I did exactly the same job, although on an older Selden boom that was pop riveted from new, I replaced them with Rivnuts...

I doubt that my Selden boom from 2000 has been opened before, and it has rivets. I like the idea of Rivnuts, as I would like to replace my furling lines and check the internal mechanism for problems. As above, any idea what size to get?

 

[vyv_cox]

I doubt that my Selden boom from 2000 has been opened before, and it has rivets. I like the idea of Rivnuts, as I would like to replace my furling lines and check the internal mechanism for problems. As above, any idea what size to get?

The bolts in mine are 5 mm. As above though, if I was doing it now I would tap the aluminium casting and screw bolts directly into it. The bolts/pop rivets do very little apart from stopping the cap from falling off, all the load is taken in compression between the boom extrusion and the shoulder in the end cap casting.

 

[Ian_Edwards]

I've been talking to Allspars, who are very helpful. My boom section is a B250 from 2007, the outer boom end casting is about 10mm thick at the lower tang and 8mm thick on the upper tang. the pop rivets were 6mm or perhaps a little bigger, the drill proved with the 6mm helicoils was a loose fit in the hole. But when we tapped it, the threads didn't seem to have much of a "flat" on them and the helicoil inserts fitted just fine. As vyv_cox says they just hold the end fitting in place all the loads are in compression.

I'm also about to order 2 new composite sliders to replace the old SS ones with wheels, they are marginally more expensive than replacing 8 wheels (and how Selden can justify £7.24 plus VAT for each small plastic wheel, I just don't know) and I hope that the new sliders will be more robust than the wheels.

I'd like to lubricate the new sliders as they are installed, but I'm unsure what to use. I'm tempted to use GT85, which is a dry chain lubricant used on bikes, I don't want to use anything sticky that will trap dust and grit, that will just wear the sliders out very quickly. Any opinions on using GT85, or other options which might work?

 

[Hypocacculus]

I'd like to lubricate the new sliders as they are installed, but I'm unsure what to use. I'm tempted to use GT85, which is a dry chain lubricant used on bikes, I don't want to use anything sticky that will trap dust and grit, that will just wear the sliders out very quickly. Any opinions on using GT85, or other options which might work?

The problem with dry lubricants is that they get rubbed off the mating surfaces very quickly so need frequent re-application. You may as well leave them dry. I do use a silicone based lubricant on our mast sliders though - it's called Tescos Value Furniture Polish and it's 38p a can.

 

[Ian_Edwards]

GT85 is £2.25 a can and is PTFE based, so just a little bit more expensive than Tesco's best, but point taken that it'll get rubbed off. However, these are reefing slides, so they don't get used that often, so it may take awhile before it get rubbed off.

 

[nigelmercier]

I use WD-40 Anti Friction Dry PTFE Lubricant: http://amzn.to/1nZGa3L

GT85 is great stuff (love the smell) but leaves a residue that will attract dust, still worth having though: http://amzn.to/1gjc450