So on my trailer sailer I removed about 15 rivets per side of the riveted on aluminium mast track into which the bolt rope of the sail feeds. This is at the top of the mast and only accounts for roughly a quarter of the luff length but it includes the very thin portion of the 7/8 rig at the top so probably contributes considerably to its rigidity and strength.

Anyway it was riveted on but I think I used too big a bit to drill out the heads so have decided to epoxy the holes and redrill in between.
The rivets I removed appeared to be stainless steel but as its aluminium on aluminium I'm thinking of replacing these ones near the top with aluminium rivets with aluminium shanks to minimise any corrosion problems.

I have read all sorts of advice including punching out the centers once fixed if the centres are steel although this doesn't make much sense as they will then be trapped in the mast. Consequently I'm proposing to use aluminium shanks and not punch them out as I think they contribute to the strength. I'm a bit worried about the strength aspect however as I know that one of the uses for these aluminium on aluminium rivets is to rivet plastic articles together.

Has anyone got any ideas as to whether this is what I should be doing or perhaps whether I should just go with stainless steel rivets again. Some of the original rivets show a little corrosion in the 27yo surrounding aluminium but not much. They have 316 stainless rivets in Bunnings but I'm not sure if the shanks are 316 stainless.

Always use" Monel" rivets when fastening to aluminum particularly mast /boom fastening.
Monel is a nickel-copper alloy that is highly resistant to corrosion and oxidation. Never use stainless steel rivets on aluminum ... the result will be over time..... corrosion. Alternatively, if you have to use a stainless fitting against aluminum cover with DURALAC Anti-Corrosive Jointing Compound

wear protective gloves when doing so

As above, just use monel with Tefgel. As for the shanks, you can pop out the mast base and then re-rivet it back in again, (which leaves two shanks at the end).

Select to expand quote

Whirlybird3 said..
Always use" Monel" rivets when fastening to aluminum particularly mast /boom fastening.
Monel is a nickel-copper alloy that is highly resistant to corrosion and oxidation. Never use stainless steel rivets on aluminum ... the result will be over time..... corrosion. Alternatively, if you have to use a stainless fitting against aluminum cover with DURALAC Anti-Corrosive Jointing Compound

wear protective gloves when doing so

Thank you yes that is what I was always taught to do and there is some discussion as to whether this is in outdated solution in light of the fact that 316 stainless is now quite cheap. There is then the issue as to whether the shank - part of which of course gets left in there - is also monel. Additionally in the past I have always been fixing stainless steel fittings to an aluminium mast and was wondering whether monel was perhaps specific to this and maybe halfway between stainless steel and aluminium on the activity scale.
Now more confused than ever. I thought aluminium with aluminium shank might be the safest solution especially on a trailer sailer where the mast comes down regularly and can be inspected for signs of failure - not that I relish the thought of doing the job twice.

Thanks guys. I still wouldn't mind knowing the reason because looking at the activity doesn't give the answer.

Anyway I found some specs on the strength of aluminium versus stainless steel rivets and it seems that stainless steel is nearly four times as strong with the sheer and tensile strength for stainless steel being in the low four thousand Newtons and lowish 5,000 Newtons respectively with aluminium in the low to mid one thousands (according to the NPX Fastenings site).
Don't know about monel but it's probably closer to stainless.

Of course I wouldn't have a clue what strength is really necessary.

Bunnings have stopped selling monel rivets and Whitworths can't tell me what the mandrels of their monel rivets are made of (if that even matters of not punched through) didn't really want to remove the mast base plug but might have to. Of course there are also sealed rivets but that doesn't seem to present much advantage. Aluminium on aluminium would solve a lot of problems if strong enough. Might try one and see how hard I have to pull the tool to set it to get an idea of strength.

I have only just searched and found this product so offer zero advice but am curious if anyone has tried these rivets?
www.amazon.com.au/Tri-Grip-Rivets-Decorative-Waterproof/dp/B0C7VGMMXP?th=1
So aluminiun coated with paint (I assume, it doesn't seem to say how the colour is applied) with an o-ring.
What got me wondering is after witnessing the longevity of colourbond guttering vs unpainted if the paint survives the application process it is a nice galvanic barrier with an o-ring?

That's very interesting Sparau.

Meanwhile NPX Fastenings was extremely prompt with the order that I placed with them for some aluminium on aluminium rivets which I may or may not use.

I like these type of pop rivet, they form a large mushroom/ washer profile on the blind side so they don't pull through,,, good for oversized holes.
They also contain the fractured stem within the rivet .
They are great for riveting PVC electrical conduit to the inside of a mast. .

huckaerobolt.com.au/products/allok-rivet-stainless-steel

Here's an example in 1/4" stainless