Filling Old Rivet Holes

[SF Bay Dude]

Some lively debate and ideas going on here. Love it! I think I'll go the thickened epoxy/JB Weld (my first choice) route. It's a pure cosmetic job that will prevent anything from turning structural down the road. Since it's getting 5-6 coats of paint, Awlgrip 545, Awlquick, and Awlcraft 2K, the surface will be fair and smooth, and unnoticeable.

[a64pilot]

Originally Posted by Terra Nova

They still have to taper them, weld them back together, fabricate and weld on winch and spreader bases, boom fittings, etc.

Compared to manufacturing a windlass, or an engine or well lots of stuff, it’s still not a whole lot to do.
We used to have our spar caps cad plated in Macon Ga, spar caps were I’d guess about 26’ long.
Guy who powder coats our fuselages and does chrome and other plating, anodize etc is in Moultrie Ga.
At least in the US, there is more of that kind of thing than you would imagine.
However hot dip galvanizing isn’t as common as it used to be, but I think that is due to a collapse of manufacturing in the US, it’s not as common as there isn’t as much demand now. (My theory)

[Jim Cate]

Originally Posted by Terra Nova

They still have to taper them, weld them back together, fabricate and weld on winch and spreader bases, boom fittings, etc.

And the important bit: for a custom rig, there is a LOT of engineering to be done. I know when we had our mast done I saw several iterations of finite element analysis done with variations in spreader position, number, etc.

If you are just replacing a stock rig in a production boat, not so much to worry about...

Jim

[RaymondR]

Originally Posted by Terra Nova

I like this. Except you can buy aluminum screws or all-thread, rather than threading a rod.

We're a little restricted in what we can buy off-the-shelf down here in Oz and it's getting worse as we lose our industrial infrastructure. I'm going to machine some new sheaves from alloy and am having a devil of a time finding alloy balls to use in them rather than the Delrin balls they usually have in them.

I have used the threaded alloy trick to repair holes where stainless screws have corroded them out. I drill the corroded hole out to about twice the diameter of the screw, do the threaded rod thing then drill and tap the plug for the original screw.

[Bill_Giles]

(Ex-aircraft metal man says All holes in a stressed component concentrate the stress around the hole (stress raisers). It is important that there are no defects at all in the holes, ie nicks, corrosion, etc. Best ensure that the holes are smooth and free of defects. Ensure that they are kept clear of corrosion by sealing. Examine the mast for corrosion and cracks at every opportunity, especially around rivet holes, whether they are filled or not.

[AuroraGH]

You can have an aluminum welder fill them before painting. They will be completely gone and undetectable.

If you are going to repaint, you might as well have professionals do it with AWLGrip and those people will be able to do the fill and fair before painting. I did this with my mast some years ago. I removed all the hardware and the yard took it away for the welding and painting. Came back like new.

[Boonzajer]

A simple and cheap method I used when I removed the maststeps on my Swedish 35 ft cruiser. Just buy yourself a bag of round plastic covering plates for SPAX screws. Choose the right size, push them in the hole - ready. Or even simpler: buy the glue on type. Remove protective cover, push onto the hole, ready. I did this 10 years ago, and ever had a drop of water coming in. Looks neat too. Name of the company is Sencys (here). Three dollars for a hundred of these nifty little things. Get an idea on this link: https://www.praxis.nl/IJzerwaren%20/...kkappen/c/f621
In Dutch, but I am sure you will find similar stuff all over the world. Of course this system will add nothing to the strength of the mast, but neither will filling these holes with epoxy or polyester. All in all, took me less than an hour to cover 88 holes.

[dcorbert]

Originally Posted by Jim Cate

Aww, come on...

Ream? why?

Chamfer INSIDE? How to do that twenty feet up the tube?

These holes are small, not concentrated on one area and in general, not likely to "grow into a crack" causing mast failure. In a typical alloy mast there are dozens of other holes, many concentrated in high stress areas; these are inconsequential in comparison. Don't frighten the horses or the OP with needless worry.

Using a sealant will help keep water out of the mast, and as such might be a good idea, but again, comparing their area to all the other holes, not a big deal.

Jim

holes that small are not going to cause a crack, especially round holes. Square holes are more likely to cause cracks starting at the corners, Had this experience with SS external chain plates because of square holes for carriage bolts. I know carriage bolts look better but avoid square holes where possible.

[a64pilot]

Originally Posted by dcorbert

holes that small are not going to cause a crack, especially round holes. Square holes are more likely to cause cracks starting at the corners, Had this experience with SS external chain plates because of square holes for carriage bolts. I know carriage bolts look better but avoid square holes where possible.

Probably the most famous “square hole” failure and one of the coffin nails in the British Aerospace industry.

However it should be understood that a corner is a stress riser, a place that concentrates stresses, and therefore accelerates fatigue.
A scratch, or other defect and or corrosion are stress risers, just like a corner is.
In explaining what a stress riser is, I like to use the ragged edge of a candy bar or cookie wrapping as an example, it has stress risers intentionally so that it’s easy to open.
Try cutting off all those ragged edges and opening a candy bar wrapper. It’s very difficult to do.

https://aerospaceengineeringblog.com...d-comet-crash/

[Souzag818]

Originally Posted by hellosailor

There are "closed end blind rivets", pop rivets that leave a piece on the mandrel inside the rivet so it has no hole after installation. That would be the easy way.

You could use short self-tapping screws, but the pointy ends might chafe wires or halyards inside. Or tap the holes and insert machine screws, which would be a lot of work but leave you the option of reinstalling steps at a future date without more drilling.

Or chamfer the edges of the holes a bit with a wider drill bit then fill with the epoxy of your choice. (JBWeld just being a filled epoxy.) You could probably fill epoxy with aluminum dust so it looked more like the mast metal when set. If you're painting the mast, epoxy filling might disappear the old holes.

Or even put a neat circle of "roof and gutter" stainless steel metal tape over each one. Reasonably permanent, really cheap and fast.

I'm with a small chamfer with a counter sink bit, and filling with thickened epoxy. Sanded smooth, and painted, you'll never know there were holes. Did it on previous boats...

[Souzag818]

Originally Posted by SF Bay Dude

Some lively debate and ideas going on here. Love it! I think I'll go the thickened epoxy/JB Weld (my first choice) route. It's a pure cosmetic job that will prevent anything from turning structural down the road. Since it's getting 5-6 coats of paint, Awlgrip 545, Awlquick, and Awlcraft 2K, the surface will be fair and smooth, and unnoticeable.

Be sure to chamfer the holes first. Increases the surface area for epoxy to stick...

[grahamb]

on our Admirals Cup contender we had an especially bendy …… tapered stick....capable of having a eight foot bend wound in......to de-power the main.....when required.....to avoid reefing...and to have the full main area available instantly for when running downhill....we gave it heaps....and often....and even when the boat was bashing to windward heavily...….with the main flogging.....seconds count.....our hole fix was only to etch prime....tape over.....paint...done...….and mast was inspected before every race......still stands 20 years later.....and has a new life as a 'cruising' yacht.....worked for us...….

[hpeer]

Why not just keep the mast steps? I would not be without them.

[Cherod]

Welding with TIG is very easy and quick with bare minimum heat in put ,,smooth off , job done

[clockwork orange]

Originally Posted by Cherod

Welding with TIG is very easy and quick with bare minimum heat in put ,,smooth off , job done

The best way for sure if you have a tig welder and know how to use it. If you need to bring in a mobile guy to do it, it can get a bit spendy for a simple job. Still, if money were no object, probably the beat solution.