Folding mast steps.

[Allan]

Do any fat blokes have experience of folding mast steps? In particular the nylon ones. I have the physic of a professional athlete, unfortunately it's a 6 foot prop forward! I think I weigh about 110kg!
Allan

 

[rogerthebodger]

I have the glass reinforced nylon folding steps pop riveted to my mast and have used then quite a lot. I an not quite as heavy as you at 80 Kgs . I normally go up by climbing and SWMBO tailing a winch of a bosun's chair.

I am in the process of changing the pop rivets to stainless screws as I and concerned with the strength of the pop rivets, otherwise no problems.

 

[NormanS]

I fitted s/s folding steps some years ago. They are excellent. IIRC they were drilled to take 5mm rivets, but I drilled them out to take 6.4mm (1/4") . I used monel rivets, and would not use stainless screws if they were merely tapped into the relatively thin wall of a mast. Sorry, no experience of the nylon steps.

 

[macd]

would not use stainless screws if they were merely tapped into the relatively thin wall of a mast.

For that sort of loading, plus the consequences of failure, +1, big-time. I'd want a thread depth at least the diameter of the fastener and preferably 1.5x

 

[Resolution]

MMmmm
I have the plastic folding steps to aid reaching up to the boom and attaching the main halyard etc. Two on one side, three on the other. Mine are screwed in with s/s screws, so I read the engineers' comments above with anxiety. On the other hand we have had ten years frequent use so far, and the only casualty was when I stupidly left one of the steps down while sailing and a flailing genoa sheet formed a close attachment. (easily replaced due to the screws of course!)
I was a wing, not a prop forward, but even so my weight is 90+kg. The steps do creak alarmingly and I try to keep off the outer ends.

 

[Allan]

For that sort of loading, plus the consequences of failure, +1, big-time. I'd want a thread depth at least the diameter of the fastener and preferably 1.5x

Yes, my thoughts exactly. Also if threads corrode the bolt comes out. If the hole around a rivet corrodes there should be enough of the swaged part of the rivet to hold but the step will become loose, thus giving some warning of failure.
I've always thought the name of the correct rivets for masts was mondel. I now know I was wrong! Do you still need to use the while grease like stuff to reduce corrosion?
The nylon steps I've just found on the net say they're OK for upto 310lbs. Even I'm not 140kg!
Allan

 

[macd]

I now know I was wrong! Do you still need to use the while grease like stuff to reduce corrosion?

There are a few alternatives, but the one most commonly found in UK chandlers etc is Duralec, a sticky yellow goo.

 

[prv]

I've always thought the name of the correct rivets for masts was mondel. I now know I was wrong! Do you still need to use the while grease like stuff to reduce corrosion?

There are a few alternatives, but the one most commonly found in UK chandlers etc is Duralec, a sticky yellow goo.

Not mondel and duralec, but monel and duralac

(I too would use rivets over machine screws for loadbearing things on aluminium spars.)

Pete

 

[Yngmar]

I'm nearly your weight and have glass reinforced Nylon steps (these ones). They flex a little and I take a halyard up as backup, but haven't needed it yet. I installed them properly, that is with Monel rivets and Duralac (the yellow gunk - keeps seawater from getting in between the dissimilar metals and causing corrosion).

Yes, three rivets are sufficient (I've confirmed this with Calibra and that's how their riggers install them) - avoids a bunch of extra holes in the mast.

 

[macd]

Not mondel and duralec, but monel and duralac

Woops

 

[rogerthebodger]

For that sort of loading, plus the consequences of failure, +1, big-time. I'd want a thread depth at least the diameter of the fastener and preferably 1.5x

Some interesting comments but I think the mode of load on mast steps need to be considered and what happens in real life when stainless steel screws are threaded into aluminium with and without Duralac.

Ok the major loads on the screw and threaded hole are

1) Shear of the bolt due to the downward load on the step.
2) Shear in the thread due to tightening of the bolt
3) Shear in the thread due to the pull out load due to the downward load on the step
4) the tension in the bolt due to the downward load on the step
5) the tension in the bolt due to the tightening of the bolt.

Now 2 and 5 can be reduced by being careful when initially tightening the bolt
Now 3 is affected by the friction on the step on the mast due to the tension imposed by the bolt tension but this load will never be greater than the weight of person and my be a dynamic loading it the step is jumped/fallen on.

Now 1 and 4 load will be due to the leverage of the load step and with the foot being say 100 mm wide so effective load point will be 50mm. The top hole in my steps are 100mm from the step so the effective pullout/tension load will be 50/100 there for half the load applied say 50/55 Kg on one bolt. Mine has 2 and the one in the pic above has 3, yes the lower 2 could between then have a little higher load but IMHO each bolt will have a load of 25 kgs giving a total effective load on the step higher than the load proposed.

Pull out/striping load on aluminium is more complicated that steel as plastic deformation tends to take place in threaded holes in aluminium so you cannot just look at the thread depth as you can in steel and I have seen research the considered that you will not get a higher stripping load with increase thread depth much beyond 1.5 x dia.

I have seen info for zinc that suggests that a striping of something like 800 to 1000kgs per bolt with a dia x depth of 30 (6mm dia 5mm depth) The dia of my bolts and 5 mm thick mast wall.

Now with regard to corrosion we all know how difficult it is to remove a stainless screw from a taped hole in aluminium and I tried to hammer out a 8mm dia bolt from a 5mm thick aluminium plate and failed. I just left it and re-drilled

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