Filling Old Rivet Holes

[GordMay]

Originally Posted by Jim Cate

Well, I'm sure you airplane guys live by a different standard, but I've looked at a hell of a lot of masts and don't recall seeing stress cracks around holes like those from mast steps...

And, stress cracks are highly unlikely to develop around round rivet holes.

[clockwork orange]

Applying aircraft standards to boats makes no sense as aircraft have low factors of safety whereas sailboat rigs do not. If you applied the same fos that spar builders used to aircraft they would not get off the ground so the use rigorous maintainance schedules instead. There is obviously no requirement to fill the holes structurally but corrosion around holes is a real possibility, I would probably clean the holes out and chamfer, then fill with thickened Gflex epoxy since you are painting. That said I used aluminum tape this spring to cover some holes in my mast from a radar mount I removed but this is in fresh water and on an anodized mast.


Steve.

[Pete7]

That would be a huge amount of work. If its for aesthetics, we have something like this on board to hide the screws holding up the ceiling panels. Hardly noticeable until one falls out. Cheap and cheerful solution perhaps?

https://www.amazon.co.uk/5mm-DRILL-H...s=screw+covers

[rognvald]

JB Metal Weld. Works for aluminum, metal, fiberglass and other surfaces. I used it for the same purpose on my boom twenty years ago. Still perfect, no corrosion. I hope this helps. Best, Rognvald
https://www.jbweld.com/collections/metal

[aa1bflyboy]

Originally Posted by Jim Cate

Well, I'm sure you airplane guys live by a different standard, but I've looked at a hell of a lot of masts and don't recall seeing stress cracks around holes like those from mast steps. After all, the holes were already there and putting a rivet or epoxy in them does not restore strength.The OP does not report any cracking around the subject holes so far.

As to the corrosion issue, not so many masts are anodized these days. Dunno about this one... But on my now 28 year old painted mast, I don't see corrosion around empty holes. Those with s/s attachments or screws are not so lucky!

I'm curious about the means of chamfering the inside of such holes. How do you do that on airplane spars? And the idea of reaming a drilled hole to eliminate stress risers... well, I've not seen this practice in marine usage. Perhaps in top end racers (if any are using alloy spars these days), but despite hanging around rigging shops and spar manufacturers shops, never encountered the reaming practice.

I'm pretty sure that the mast on a Skookum 47 is more of a telephone pole than a bendy noodle and can likely suffer the crude marine standards without much risk... been standing for a while now!

Jim

Spray with corrosion X or LPS2

That’s what I’ve always done with my aluminum flying machines

[captlloyd]

Originally Posted by Ecos

Sure, it's sloppy. At least put some sealant in the holes. At best ream and chamfer each hole both inside and outside and then treat for corrosion. Every one of those holes could grow into a crack and your mast could break off.

I too am very curious about the tooling it takes to chamfer a hole from the inside 20 ft. Up ? Can you elaborate?

[FionaJC]

Originally Posted by SF Bay Dude

Any harm in leaving them unfilled?

I had a mast with holes and they corroded and one got bigger and bigger then one day a small crack. I drilled it out filled it in before it wordened. Only spotted it because I sent our son up for another task, well he spotted it.



I would make sure they are clean and then seal them with something inert like chemical metal and polish down to a small blip.

[model 10]

Originally Posted by captlloyd

I too am very curious about the tooling it takes to chamfer a hole from the inside 20 ft. Up ? Can you elaborate?

I have several from being an aircraft mechanic. The factory jobs are a piece of rod that has a spring loaded steel tang which pops out when you stick it through the hole. Then you run it with a drill and it cleans up the edge. You can also make your own with a piece of piano wire.

[Fore and Aft]

I removed the sail track from my mast two years ago and installed a new one. All the old holes I simply filled with epoxy and microballoons then painted with epoxy paint. Two years later it still looks perfect and no sign of corrosion I have a feeling there was even a couple of 10mm diameter holes from old cables I filled as well.
Cheers

[clockwork orange]

Originally Posted by Pete7

That would be a huge amount of work. If its for aesthetics, we have something like this on board to hide the screws holding up the ceiling panels. Hardly noticeable until one falls out. Cheap and cheerful solution perhaps?

https://www.amazon.co.uk/5mm-DRILL-H...s=screw+covers

Ive tried these type of product outdoors and the UV killed them pretty quickly. That's not to say there are not UV stable ones available though

[a64pilot]

Originally Posted by captlloyd

I too am very curious about the tooling it takes to chamfer a hole from the inside 20 ft. Up ? Can you elaborate?

This will do a better job than you might imagine, you use the piece that looks like a U sort of, stick it through the hole and it deburrs both sides, it sort of scrapes and it rotates on its own


However I assume a mast is in compression more than not, and being in compression it’s not really subject to stress fatigue, plus of course almost all are externally braced.
They don’t anodize masts anymore? What do they do, mine is old, but is most certainly anodized.

[a64pilot]

Originally Posted by captlloyd

I too am very curious about the tooling it takes to chamfer a hole from the inside 20 ft. Up ? Can you elaborate?

You do these things, because you know to, it costs no money and you have the ability and knowledge.
It’s sort of like flaking lines and neatly storing them as opposed to stuffing them into a bag

[a64pilot]

Originally Posted by GordMay

And, stress cracks are highly unlikely to develop around round rivet holes.

They really are not. They are way more unlikely to develop around a smooth, polished hole.
Jim, I know you were once a racer, so therefore I’m certain you have polished the beams of connecting rods, you did that to remove stress risers.

Remember this? Well the cabin roof unzipped right along rows of fasteners, rivets most likely. Corrosion, and fatigue was the cause

[Jim Cate]

OK, I guess I am confused by your use of the term "chamfer" when you are really referring to de-burring. To me, a chamfer is like the countersink for a flat head screw, and I couldn't see how you could do that inside a tube. But de-burring, well sure, there are many designs of de-burring tools that will do that job.

None the less, I'm not convinced at all that anything needs to be done to remove stress risers from such holes in masts. De-burring is always a good idea, just from the safety from snagging skin aspect.

Jim

[a64pilot]

I’m no saying you have to, but it’s not a bad idea.
Like I said I don’t think the mast actually carries much of the load in a mast with wire rigging, the wire does.
However there are of course internal chamfering tools. Here is a picture of one, stick it through the hole and the cutting edge sticks out, chamfer, retract the cutter and go to the next hole.


Drilling a hole and then running a reamer through it to remove any tooling marks (stress risers) and the deburring is just good practice.
Anyone wondering exactly what a stress riser is, look at a candy bar wrapper, those cut edges that concentrate the force when you open it and cause the paper to tear, those are stress risers.