Best way to fill threaded holes in aluminum spars?

[BELLATRIX1965]

Greetings all:

I would appreciate any suggestions regarding permanently filling no-longer-used threaded holes in aluminum masts and booms? The boat is 40 years old, and many hardware items have been removed / upgraded over the years. The aluminum is pretty thick (1/4" +-) and most holes have the threads intact. I'd like to clean it up (flush would be really nice) before a full re-paint of the spars.
Thanks in advance, and think SUNSHINE (been raining here in Maine for weeks!)!

[OhioTom]

Unless you can weld aluminum, I'd screw a piece of stainless steel threaded rod or stainless steel bolt into the hole with some red loctite on the threads, cut it as flush as you can with a cutting wheel (dremel), then file/sand it fair.

[poopdeckpappy]

If your spars aren't riddled with holes, maybe something as simple as alu...alumanam.......alumenum........ pop rivets of the same material

can't say suspagetti either

[Windborn]

BELLATRIX1965,

I had the same issue with our boat. You can order various sizes of aluminum threaded rod from McMaster Carr. I put some locktite on the threads, screwed it in about 1/4" then cut of the rod. A bit of sanding and some paint, and you'll never know the holes were there. Just don't allow too much of the rod to stick out on the inside of the mast, or you might create a snag for your halyards.

[j34035]

I repainted the mast and boom on my boat a couple of years ago. When I removed the unwanted hardware, I used a small grinding burr to clean the inside of the holes the used a counter sink to widen the opening. After that, I used a polyester body filler and simply filled and faired the holes. Awlgrip paint and you never know the holes were there.
DD

[sailingdog]

Filling the holes with a thickened epoxy or epoxy putty is probably your best solution. OhioTom's suggestion is unwise, since stainless steel will have galvanic corrosion issues with aluminum and may lead to future issues.

Windborn's idea is a good one, but far more work with little advantage over using an epoxy putty.

[14432]

If your spar is painted white or clear anodized - Marine Tex comes in both white and gray so you may not even neeed to paint.

On that note - has anyone ever tried to color white Marine Tex with gelcoat coloring agents?

[sailingdog]

I would be hesitant to do that, as it may affect the epoxy's adhesion. Of course, you could always call the manufacturer and ask them.

Originally Posted by 14432

If your spar is painted white or clear anodized - Marine Tex comes in both white and gray so you may not even neeed to paint.

On that note - has anyone ever tried to color white Marine Tex with gelcoat coloring agents?