Fitting a rope clutch to the mast

Skylark

Skylark

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I'm thinking about adding a rope clutch to the mast of my 36 ft AWB to keep tension in the 12 mm dia headsail halyard.

Can I successfully drill and tap M6 threads into the mast and expect to have adequate holding power or is this a job for a rivet?

Many thanks for sharing your wisdom and experience.
 
davidjackson said:
I'm thinking about adding a rope clutch to the mast of my 36 ft AWB to keep tension in the 12 mm dia headsail halyard.

Can I successfully drill and tap M6 threads into the mast and expect to have adequate holding power or is this a job for a rivet?

Many thanks for sharing your wisdom and experience.
Click to expand...

I would use neither, but both.
Try using a monel rivnut, available in M6
Use a bit of Duralac......

http://www.powerfuluk.com/products/...4-m5-m6-rivnut-selection-pack-(-80-pcs-).html
 
No, a tapping in the thickness of a mast wall won't be man enough for the loads imposed by a clutch on a headsail halliard. Apart from anything else the threads will start to corrode and weaken from day 1.

The strongest way to do the job would be to bolt through - not as impossible as it might at first appear but you need to get the mast down and remove the heel casting then use a spanner on a long stick. Failing that go for pop rivets or rivnuts as has been said.
 
If I had the taps already, I would thread the mast. It looks poor practice to me but seems to be standard.
I like the look of the rivnuts but it's a dear do, just for one fitting. However, my mast will need to be refurbished in the near future, rivnuts looks just the thing for a larger job.
 
Depends on the wall thickness of the mast. Some bigger extruded masts are thick enough to tap a thread into but if the thickness is less than the diameter of the machine screw thread it is likely to pull out with big loads on the clutch.
I've seen large self tapping screws used but of course that endangers a reaction between the SS and the alloy mast.
Monel rivets are probably favourite but you need to check that you can get your rivet gun into the space available around the hole in the clutch body and that your rivet gun is 'man' enough for the job.
 
Last edited:
Scotty_Twister said:
Depends on the wall thickness of the mast. Some bigger extruded masts are thick enough to tap a thread into but if the thickness is less than the diameter of the machine screw thread it is likely to pull out with big loads on the clutch.
I've seen large self tapping screws used but of course that endangers a reaction between the SS and the alloy mast.
Monel rives are probably favourite but you need to check that you can get your rivet gun into the space available around the hole in the clutch body and that your rivet gun is 'man' enough for the job.
Click to expand...

Large self tapping screws may also provide a really good chafing and cutting point on internal lines or electrical cables.....
 
I'm sure that 99% of all fittings atached to alloy masts are riveted with monel rivets. Why not just do the same?
 
Why not bolt it on? No need to take the mast down.
Drill the bolt holes. Push a piece of string thru each hole (from the outside obviously).
Fish the ends of the strings out from the bottom of the mast (assuming there is some sort of access hole)
Now the important bit ... glue the tail end of the bolts to the ends of the pieces of string (I used Areldite Rapid). Make sure that the end of the string is only attached to the end of the bolt.
Pull the string gently back up the mast and out of the bolt hole.

Voila, you have a bolt sticking out of your mast from the inside.

Fix your cleat or whatever onto the bolt and apply the nuts.
(you may have to hold the protruding end if the bolt with a mole wrench to tighten the nuts)
Cut off any surplus bolt length.

NB dont drill a hole in your Radar Cable.

Good Luck!
 
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