Tag Archives: aluminum spars

Naked Boom Gets Primed

I sanded Madsu’s boom down to bare metal yesterday as I get ready to paint it.

After removing all the hardware I sited all the new/changed hardware and drilled and tapped the holes. I’ll use stainless machine screws instead of the self-tapping screws the previous owner loved. I’ve filled all the old holes with Star Brite aluminum epoxy.

The spar’s in great shape. I used a rotary sander to get the mast stripped down then use my Makita sander with 220 paper to prep it.

I used PPG DX 533 to etch the boom, then quickly followed up with PPG DX 503 conditioner. I got both at my local Lordco auto parts store – way cheaper than trying to find the marine version of same.

Once the DX 503 was rinsed and the boom dried, I immediately got the first coat of primer on. You can’t let the aluminum sit for any length of time after treatment because of oxidization (so I’m told).

I’ve opted for the tried-but-true-but-messy-and-smelly 2 part primer.

The Interlux 2 part is a lot more trouble – it’s really 3 part because even after you mix the 404 base with the 413 reactor, you still have to thin it 20 to 25%.

I wasn’t really sure how to work with the base – it’s the consistency of pudding – and you can’t pour it. I just stuck a mixing stick into the can and pulled it out, about an ounce or so stuck to the stick and I was able to use this ‘honey stick’ method to measure out what I needed.

I first tired a small foam roller – that was useless. Next I tried a disposable foam brush – that worked better. But a regular paint brush works best of all – the paint is thick and spreads beautifully, and there’s no worry about brush strokes showing up.

(boom after 1st coat of primer)

I left it overnight and sanded with 220 paper and got a 2nd coat on this morning. The weather’s been cold and I’d prefer it was a bit warmer to make sure the primer is really baked – I’ll give it a couple of days then do a 3rd base coat.

Now that I’m confident with is all going to work (!), I’ll strip the mast and get it primed, then I’ll topcoat both the boom and the main at the same time. I’m using Interlux Perfection, another 2 part, for the topcoat.

A quick survey of my mast hardware turned up a few issues. I was hoping to replace the spreader brackets, so last fall I ordered a stainless set from Catalina Direct.

Turns out my spreaders are 1 1/8th inch in diameter but the new brackets are 1 inch. Ugh. I’m thinking I’ll either leave the old brackets (which Catalina Direct claims are prone to unexpected breakage) or visit my new best friends at the metal store and pick up some 1 inch aluminum tubing and make my own ‘new’ spreaders.