Rivets or machine screws for mast steps?

[BAD ORCA]

The solution to halyard stretch is to pretension the halyard with the winch to more than you body weight plus live load. Then there can be zero stretch. Even with polyester halyards, I've done this many times. You should get right to the top. Really. The material of the halyard should play no part if it is pretensioned correctly.

You hands go on the mast, not the ladder. That also helps. Wear shoes that slide into the steps easily (no tread). Roll the ladder the correct way for storage and the rungs will fall open.

(The ladder is at the top of the mast. Keep your weight in and arms around the mast. Most of the steps are nicely open, as you can see, but one got squeezed by the spreader.)
View attachment 230883

It's all in the tricks.

(Note that the ladder is only about 4 inches down. I could have done better, but this is enough. Polyester halyard.)
View attachment 230882

Ah ok I will give that a try. I was not putting any tension on the halyard, just cleating it off. That might make all the difference. The 'bouncy' stretch as im climbing is what is making me uncomfortable. This might help with that then.

 

[dLj]

Ah ok I will give that a try. I was not putting any tension on the halyard, just cleating it off. That might make all the difference. The 'bouncy' stretch as im climbing is what is making me uncomfortable. This might help with that then.

I'm trying to wrap my head around a halyard with that kind of elasticity. What kind of line are you using for your halyards?

dj

 

[BAD ORCA]

I have to disagree DJ.
The heel should look like this.
There also should be something to at least to resist the foot slipping sideways.

View attachment 230888
I know that there are reasons for foldaway mast steps but for safety, nothing beats the stirrup type.
Your foot cannot slip out sideways.

Back to the OP.
If you are going the (monel) pop rivet route try to beg, borrow or steal a power riveter.
As I mentioned 60 holes and rivets suspended is no fun.
A power riveter won't make it more enjoyable , but will cut the time aloft dramatically.
$50 on Ama###
Gary
View attachment 230886

The steps have a nice upward angle when open about 5 degrees give-or-take.

If the mast is down, drill and tap.
If the mast is up, pop rivets.

You say that there are 30 steps. ($1860).
That means 60 holes to tap and drill while hanging from a bosun's chair.
Not my idea of fun.

RE: are probably the best I've ever seen...

Take a good look at the pivot point. No support below, (blue arrow)
View attachment 230881


gary

The steps have a nice approx 5 degree angle up when open. They are pretty chunky piece of aluminum. Holding one in my hand, I would absolutely be more concerned with the attachment to the mast failing.

 

[BAD ORCA]

These are good looking steps but I see a few misconceptions/problems.

1. The attachments (screws) are not just in shear. In fact, the top screw is clearly in tension as the pivot point acts as a fulcrum and tends to "pull out" the top screw. Even the bottom screw is probably in some tension depending on the geometry and when where the foot is on the step but it looks like it would be in some tension. Do an experiment. Screw the step into some wood (not very deep or big to you don't have to strain too hard) and then pull down on the step. I'll bet dollars to donuts that the top screw will pull out easily followed by the bottom screw. I'm not saying it is a bad design, but the top screw is clearly in tension.

2. I have folding steps (three). I frequently go up on these to secure the sail when it is down. I find that sometimes if my foot "catches" on one of the steps as I step up and it folds up. When it does that I can get down okay, but if it were to happen up high on the mast I'd be hard pressed to get to the next step down without some gymnastics. Of course, I assume you'd be going up higher on the mast with some sort of secondary way to lower you. If not, you might be up the creek without a paddle.

I agree partially. The outer tip of the step is about 1" above the bottom edge of the backing piece when its open. It angles upward when open. It seems to me like most of the force will be pushing hard directly behind the pin and the very bottom portion of the backing plate directly into the mast. It feels like the upward angle of the step forces most of the energy directly into the bottom section which is the beefiest area of the step. It seems like the bottom screw/rivet would be under the most tension load in this circumstance. If the step was 90 degree to the mast when opened, i feel like the top screw/rivet would be instead. I'm not sure if that was the engineering behind the step or not? Im not an engineer though, just my opinion holding it in my hand... The angled upward step feels like it changes the fulcrum pivot point to the bottom fastener. Not sure if that better or worse

 

[BAD ORCA]

I'm trying to wrap my head around a halyard with that kind of elasticity. What kind of line are you using for your halyards?

dj

No idea. Its what was on the boat when i bought it. Its 7/16 or possibly 1/2" with the common blue specs you see on most generic halyards. The ladder is nylon so also stretches some. My guess is that it stretches a couple feet or more but could be because as Thinwater pointed out, it may be too slack when i tie it off and some of that stretch is just slack being taken up. Add in the natural stretch in the rope and ladder, and i guess thats whats causing so much stretch. I will have to try winching it down a bit. I dont know how much 70' of rope like this stretches under tension normally. The rope is 10+ years old as well...

 

[thinwater]

Just offhand I suspect that you would be able to support yourself by standing on the outside end of the step if the top screw ONLY was screwed into the mast. It wouldn't matter how many threads were attached to the air inside the mast as long as the screw was torqued down properly. However I suspect their insurance company would not accept that as proof of concept but would instead expect engineering diagrams.

That is a curious question.

An engineer would tell you that the loads are statically indeterminate, because the extent to which they share shear loads (and to a lesser extent pullout loads) depends on the flexing of the materials and how snug and well fit the screws are. In principle, if strong enough, the lower screw could also hold the load (but we both doubt that would work). In practice, the lower screw sharing the shear load allows the upper screw to handle the pull out a little better. More importantly, it prevents rotation and lossening of the upper screw.

These sorts of things are actually tricky to accurately evaluate; the easiest way is to break one. I'm pretty sure the step breaks in some way before the fasteners.

 

[thinwater]

Ah ok I will give that a try. I was not putting any tension on the halyard, just cleating it off. That might make all the difference. The 'bouncy' stretch as im climbing is what is making me uncomfortable. This might help with that then.

Hoist it to the top, lower a few inches and anchor it down using the Cunningham tackle (or a lashing), and then winch the halyard tight. That will fix it. It also makes the ladder much more stable. Hoisted in this way, you can actually climb it without the slugs in the mast; it won't bounce, but it will move and you may find it unnerving. I've done it that way under sail, and it felt much safer than a boson's chair or steps, to me (a boson's chair can swing and your feet can come off the ends of steps).

It took me many uses to learn all of the tricks. Now I love it and find it feels very safe. I use a harness and I have a special rope grab (Camp Goblin) that rides another halyard as a safety.

 

[thinwater]

My main concern with machine screws would be breaking a tap or several. Some A-hole is going to come by and rock the boat. Getting a broken tape out of a hole at the bench can be tricky, up the mast you might find you now have a hole you can't use and need to move the step.

a. If you have not tapped dozens of holes, try the first few in a similar scrap of aluminum.
b. Now, visualize doing that hanging in a harness with your legs falling asleep while someone shakes you by the shoulder.

It is going to be very hard.

That is why we suggest rivets. Still hard. If you have the mast down, then either way.

(I also hate stuff on the mast. At the very most two for masthead work and two down low if needed to work on the boom (larger boats)).

 

[jssailem]

Hanging in the harness can get old. There were times in my youth, but the older I got, the less I liked the dangling.
If I were to add steps, they would be while the mast was about 4 feet above the ground. This means greater control and better results, in my opinion.

 

[dLj]

That is a curious question.

An engineer would tell you that the loads are statically indeterminate, because the extent to which they share shear loads (and to a lesser extent pullout loads) depends on the flexing of the materials and how snug and well fit the screws are. In principle, if strong enough, the lower screw could also hold the load (but we both doubt that would work). In practice, the lower screw sharing the shear load allows the upper screw to handle the pull out a little better. More importantly, it prevents rotation and lossening of the upper screw.

These sorts of things are actually tricky to accurately evaluate; the easiest way is to break one. I'm pretty sure the step breaks in some way before the fasteners.

I actually started to look if I could set up the free body diagrams for this earlier today but the step design is actually pretty complicated. Of course there will be both tension and shear loads on the screws. However, given the layout of this step the principal loadings on the screws would be more shear than tension. At least that's what it looks like to me. If someone wants to go through all the calculations and is willing to put them up here - I'd be happy to say I am wrong...

dj

 

[thinwater]

The simplest way to put any of your fears to rest is to attach one to a test plate (scrap of the same thickness), fix it vertically, and jump on it HARD a dozen times. The engineer way! If everything looks good, move on. A hard jump is probably a good safety factor, since climbing is belayed. As a sole means of support, it probably would not meet any building code. Consider how strong a stair step or ladder rung must be.