Mast structural integrity - pop rivet removal

dylanwinter

dylanwinter

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www.keepturningleft.co.uk
The top of my Centaur mast looks like this

S1620016-mast-view.jpg


the roller main is as flat as a board so I thought I should at least offer it a clean feed of air.

So if the steps and the rader reflector go that is 26 rivets removed. 26 holes revealed.

What impact will this have on the structural integrity of the mast?

and

Should I fill the holes with more rivets or just let the wind blow in and out of them?

What tune will she play?

If I were to remove the roller main track that would be another 120 rivets to be drilled out.

Does anyone want to swap masts?

more snaps of new centaur here including one of the rig while under way

http://www.keepturningleft.co.uk/blogs/first-sail-2/
 
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You can probably remove the rivets safely,I don't think they do anything to replace the strength lost from drilling .
I would never have the courage to make so many holes on a mast but as long as they're not aligned horizontally around it you should be ok.The fact is the mast is still standing....
 
Essentially once the holes have been drilled the integrity is lost. So it does not make much difference whether you remove the attached device or if you fill the holes with rivet epoxy or any thing else.
The track of the, in mast roller main would however add to the strength of the mast itself. I would think.
I don't think I could agree with your removal of any of that other gear on the mast. Mast steps have their uses and of course a radar reflector might be useful one day and you will never know it.
The flat main might be induced to have more camber with less halyard tension and less outhaul tension. This is good for light winds. However the flat main would be good when it blows a bit.
Dylan you are thinking too much (obsessing) just sail and think what a lovely boat you have. Taking gear off the mast will not improve performance noticeably. good luck olewill
 
William_H said:
Essentially once the holes have been drilled the integrity is lost. So it does not make much difference whether you remove the attached device or if you fill the holes with rivet epoxy or any thing else.
The track of the, in mast roller main would however add to the strength of the mast itself. I would think.
I don't think I could agree with your removal of any of that other gear on the mast. Mast steps have their uses and of course a radar reflector might be useful one day and you will never know it.
The flat main might be induced to have more camber with less halyard tension and less outhaul tension. This is good for light winds. However the flat main would be good when it blows a bit.
Dylan you are thinking too much (obsessing) just sail and think what a lovely boat you have. Taking gear off the mast will not improve performance noticeably. good luck olewill
Click to expand...

you forget though.... I have to film the sails.... and I can hardly bare to look at that junk. It going that is for sure. All I need is a small man with a cordless drill.

Any volunteers?
 
Re structural integrity of the mast. The mast will be stayed (suported) at the top and the middle. This means that the most vulnerable parts of the mast when hit with column compression are the areas mid way between the bottom of the mast and spreaders and between the spreaders and the top.
The mast can crumple sideways. Usually the smaller dimension. This would entail a hole opening up on one side and or the crushing or crumpling of the mast on the other side. So for this the sides are most critical.
The mast can also crumple fore and aft. Less likely due to larger dimension and more material in the front and track part of the mast. Again an openign up and crushing failure mode.
Or of course the mast can crumple partly sideways and partly fore and aft. (Corner wise)
In each case however the area near the major supports base mid and top are less vulnerable. So while the mast has a constant section from bottom to top you can more safely have holes near the spreaders and top and bottom.
As said it is also desirable that holes be not in a line or too close together. good luck olewill
 
To cover the bare holes, mount some foam pads on discs slightly larger than the holes and set them up on levers running down the mast, like they would on a huge clarinet or other woodwind instrument. With a good wind you can play what you like; have a go at Brothers in Arms!

Alternatively, leave the holes open and fill the mast with peanuts for the birds or any passing Marine Squirrels.

But seriously, I would definitely fill the holes with the proper sized rivets. They don't cost much, they will ensure the integrity of the structure (even if we can't agree whether or not it's necessary), they will stop things living in your mast, keep the weather out and you (or one of your minions) will be up there anyway.

Good luck
 
You are obliged to deploy a radar reflector if practicable. It will be difficult plausibly to claim impracticability if there used to be one but you removed it.
 
alan_d said:
You are obliged to deploy a radar reflector if practicable. It will be difficult plausibly to claim impracticability if there used to be one but you removed it.
Click to expand...

I would rather hang a rain catcher when visibility is bad rather than than look at that thing on a sunny day up the Fal

I am afraid it is going.

Not going to practice archery on sundays either

D
 
I would keep the lot; I turn to jelly at the top of a ladder but someday the steps will be useful.

Radar reflector-well it goes without saying.

If you have to remove stuff, yes I suppose big monel pop rivets better than nothing - and you can get little tapered plastic plugs to fill the central holes if you wish; Sailspar are as always the people to ask, supremely helpful.

MOST important; any aperture in the mast MUST have rounded corners, ir round and / or rat tail file.

Otherwise it's asking for crack propogation.

Remember the high fatality tragedies with the early Comet airliner ?

Basically due to windows being square edged not rounded off at the corners of the alloy skin...

Also remember zinc chromate Duralac paste when sticking on new rivets, blanking plates etc, but the rounded corners in holes are the really important bit.

Seems to work as I built my mast from a Bowman kit 39 years ago and have fitted lots of bits on other people's rigs - as the makers of parachutes say, ' I've never had any complaints ' ! :)
 
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If it can wait until you get up to Skye, I will happily go up the mast for you,bveing a relatively diminutive sort who rock climbs, owns a cordless drill, and lusts after a set of mast steps.

But think of the shots you could get from even half way up your mast! I would keep them.
 
Radar reflector - keep
Steps - keep
Roller reefing - dump
Rivet holes - fill with cheap alloy rivets and plastic bungs (cosmetic only)

You'll need a new main and reefing system.
 
ghostlymoron said:
Radar reflector - keep
Steps - keep
Roller reefing - dump
Rivet holes - fill with cheap alloy rivets and plastic bungs (cosmetic only)

You'll need a new main and reefing system.
Click to expand...

I don't know what the steps are for though.... they only start above the spreaders so you still need to dangle from some rope to get there

the radar reflector is an ugly blimp

the roller reefing can wait for a bit and I will see if I want to live with it.

A replacement main should be fairly easy to find.... there are a lot of second hand Centaur mains lurking in people's garages

all I have to do is to find the blokes who have them

D
 
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