Welded lifeline stanchions on a steel hull - pipe or flat bar?

Discussion in 'Metal Boat Building' started by pdwiley, May 15, 2012.

  1. pdwiley
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    pdwiley Senior Member

    Basically, what are the pros and cons?

    Flat bar is a lot easier to drill & weld and no worries about trapped water in the tube. Not as resistant to bending with a side load but how often is there going to be a side load on a stanchion?

    They'll be welded to a horizontal 20NB Sched 40 steel pipe that is the capping pipe on the bulwarks.

    I've an open mind WRT a welded pipe top rail or using all wire.

    Just finished welding the 20NB Sched 10 stanchions for the quarterdeck railing which is all pipe so no holes to let water in. This is concentrating my mind as I'd like to get the rest of the stanchions done, it's pretty much the last (hah) welding needed on the hull.

    PDW
     
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  2. Ad Hoc
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    Ad Hoc Naval Architect

    PDW

    Do you have any objections to S/Steel..or is it simply cost?

    FB is ok..but you can bet when in a rough sea and you're making no headway, or little, and the motions are uncomfortable, you'll either slip or get knocked off you're feet and land side ways onto a stanchion.

    Never design a safety feature for a ....well..how often shall that occur....it only needs one overload to fail!
     
  3. pdwiley
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    pdwiley Senior Member

    Ah, sorry, all the stanchions will be 316L regardless of pipe or FB. The quarterdeck pipes are 316L as well. The bulwark cap rail is plain steel, I'm using E309 wire to do the stainless to mild steel welds. This was a cost decision, yes, I would have liked 316 rub rails and bulwark cap pipe but couldn't afford it at the time. I may add a bit of split 316 welded over high wear areas on the bulwark cap pipe.

    Thing is, if there is either a pipe top rail or wire lifelines, I can't see how you can get tossed into the side of a stanchion. The wires have to yield an awful long way first, or the top pipe needs to be severely bent.

    Now, adding some sort of diagonal brace to the stanchions either side of an opening for a boarding ladder etc, sure, but I'd do that regardless of pipe or FB.

    The ships I used to sail on all had FB stanchions but they also had fully welded railings not wire, and the stanchion sections were something like 50x6 or bigger. I'm looking at using 25x6 FB or 20NB Sched 10 pipe. As I said I'd prefer the FB for ease of initial construction and elimination of possible hidden rust pockets.

    PDW
     
  4. Frosty

    Frosty Previous Member

    I think 30 inches is the minimum, but what ever you choose I would make them high.

    Say 4 foot
     
  5. Northman
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    Northman Junior Member

    Peter,
    for what it's worth: My boat has 1 1/2" black painted pipe with ss nipples welded in for the lifelines. I was a bit sceptical to begin with because of the the possibility of trapped water, but so far they seem to hold up fine.
    These stanchions are big, solid and 1 meter high. Some may say ugly, but in that case I prefer function over beauty. I feel safe with them and that is the main point. I attach some pictures. For all I care everything round on a boat is preferable to corners, stanchions included.
    I agree with Frosty, make them high. Sometimes lifelines seem more like tripwires to me.

    I admire your optimism :D

    Walter
     

    Attached Files:

  6. pdwiley
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    pdwiley Senior Member

    Hey Walter, I like that shiny disco ball on your cabin top :)

    I've thought of a way to avoid internal rust - basically, weld the s/steel stanchions on, drill a drain hole low down above the weld and pour in epoxy paint until it comes out the hole. Water can't get to the underlying mild steel capping pipe. In theory.

    However - in theory, there is no difference between theory & practice. In practice, there is. So I think I'll just use FB because a problem avoided is better than one fixed.

    1m high is going to look bad. 750mm is what the designer has drawn. That's what I plan to use.

    PDW
     
  7. Northman
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    Northman Junior Member

    I understand completely. Form over function. After all, you must compensate for the lack of a shiny disco ball somehow :p

    Walter
     
  8. Frosty

    Frosty Previous Member

    High stanchions may not look right but they will feel good and safe which is what they are for.

    A designer has other priorities.
     
  9. Northman
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    Northman Junior Member

    I'm with Frosty on this one. But then, I'm rather pragmatic with a strong lack of esthetic sense. As my wife frequently reminds me.
     
  10. RayThackeray
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    RayThackeray Senior Member

    Looking around my boatyard, I see quite a lot of welded mild steel stanchions. Many are well over 50 years old and very little rust.

    An old hand told me to drill a hole at the bottom and on a dry day after any water is out, shove in a rag soaked with diesel and light it, it'll take out the oxygen. Then weld it shut. That should take care of internal corrosion!


     
  11. CatBuilder

    CatBuilder Previous Member

    Side loads are all stanchions ever receive (athwartships) and that's what they receive when you most need them - when you are about to go overboard.

    Unless, of course, you are talking about positioning flat bar so that they are widest athwartships. In that case, you will be *very* injured when you (or a guest or family member) falls on them.


    I think they make them round for a reason. It's so you don't get hurt and so they can stand up to the side loading, which is the only type of loading a stanchion is ever under - be it from someone falling on the lifelines or a launch driver putting his line around your stanchion to hold in place while delivering your guests aboard.
     
  12. SamSam
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    SamSam Senior Member

    I haven't read to see what your construction is. But.
    I had a use once for car torque tubes (tubular drive shafts) as very large candle molds. I got them from the junk yard and no matter how nasty and rusty they were on the outside (Minnesota road salt mud wore out old car nasty) when I cut the universal joint ends off, the insides were factory fresh metal wise, with just a slight coat of oil. If your stanchions are welded shut air tight, I don't think there would be any problem with rust.
     
  13. pdwiley
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    pdwiley Senior Member

    That's the trouble with the written word, what's in mind doesn't end up posted - I did mean that the long axis of a FB would be athwartships but I didn't say so, thanks for catching that. So the load is (nearly) always on the strong axis.

    The concern about getting tossed into them is a real one and it is the one which gives me the most pause. A pipe will spread impact better. However big ships use FB so is the concern more theoretical than real? I don't know. I did notice that a lot of the racers in the last Sydney-Hobart race had padding over their lifeline wires to soften the impact so does that lead to people using pipe instead of wire? For racing boats at least the answer is no.

    As for internal rust, the issue is the holes drilled through the pipes for the lifeline wires need either to be bushed with a welded in tube to keep water out or the pipes need a weep hole at the bottom to let water out. Welding in a ton of small bushings is such a PITA that I do not plan on doing it. I've seen people use copper pipe flared both ends to seal the holes - what does anyone want to bet that water can't get in? I'm willing to bet that it will.

    I guess I'll have to think about it until I run out of procrastination time then go with what seems like the best idea then. It appears a toss-up structurally with FB offering less long-term maintenance issues. At worst I can always cut them off and weld on the other type, it's only a small area of paint on top of the bulwarks that would get burnt.

    PDW
     
  14. Ad Hoc
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    Ad Hoc Naval Architect

    No, the danger is still there.

    Big ship motions i.e. accelerations are significantly different from sailing vessels. Also the LoadLine Reg's requirement of having the height to be 1000mm and also 3 or 4 (depending what section is used) rails/bars in between. This is for crew protection.

    Also when walking around on bigger vessels, you're walking!...the sides are for walking and getting around the boat. On a yacht the are simple means of getting about from the fore deck to the aft and not for "general walking" around to get a nice breath of fresh air, so to speak.

    So the hazard is very different and must be recognised as such.

    If you're heart is set on an open cell member, then why not a "T". Either extruded profile, or fabricated. But falling onto them is, or should be, your first priority, as this is a very real and potentially daily hazard when caught in a storm.
     

  15. pdwiley
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    pdwiley Senior Member

    The different size, speed of motion and fully welded construction of ships railings is a factor that I'd considered and was wondering at the validity of the comparison with small vessels. I accept your opinion that one shouldn't extrapolate one to the other.

    I hadn't thought of a T. That would seem to offer the best of both worlds. I've never seen a T stainless section but I also haven't looked. OTOH fabricating them from FB would be trivial and with the cross bar of the T inboard there would actually be more area to spread the impact rather than less, also an increase in stiffness fore & aft compared to just a piece of FB.

    As a tube/pipe of 25mm OD has the equivalent of 78mm of FB in it, I could use a 25x5 and a 32x3 welded and end up with the same mass as a piece of pipe, close enough, so no weight penalty either.

    I know that you suggested it as an alternative, but would you actually do it? If so what size FB would you recommend as adequate, if I may ask?

    Otherwise I think I'll just use pipe, drill it for the lifelines, accept that water will get in somehow so make sure there's a weep hole low down, and fill to that level with epoxy of some sort.

    PDW
     
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