Ooops! -- Maybe

[Dennis M]

I have been working on the masts for the CS 15. Got the snotter attachment points bolted on. Got the collars made up and plugged the bottom ends and capped them. Good progress, I thought, until I was looking at John Turpin's launch pics (very nice job, btw) and realized I forgot to attach tack points and put a cleat on each mast for the snotter belay.

Since the caps are glued in, bolting these on seems out of the question. Long reaches in narrow and dark tubes militate against it. So, can such things be riveted on? Would sheet metal screws be enough? If they can be riveted, besides needing a rivet gun, is there a particular type of rivet I would need? I know there is an alternative to run these attachments to the deck, but I've misplaced my building CD. So, if anyone has any pics to share, I would appreciate it.

Thanks,
Dennis

 

[Ray Frechette Jr]

you can drill and thread the masts  for bolts or screws.

[wkisting]

One addition to Ray's comment: It's best to use fine thread screws for this. The aluminum is thin and course thread hardware doesn't get nearly as much of a bite, so it more likely to pull out over the long term. But yes, you can thread directly into the aluminum, and the aluminum should be soft enough that you won't need to use a thread cutter. The threads of the stainless screws/bolts will cut in securely and hold if you drill the hole the right size to begin with.

[Scott Dufour]

I made a similar mistake, and I unfortunately didn't think the aluminum would have the holding power for threading.  (I should have asked here like you just did.) I ended up drilling a 1/2" hole on the opposite side of the mast to fit a homemade tool through to hold the nut.  It was only after drilling this hole that I thought, "Duh!  Threaded Rivets!"  Would those provide better holding power than just tapping the aluminum?  Anybody have experience with these things?

http://www.rivetsinstock.com/rivet47.htm

[Ray Frechette Jr]

I would second Wes on the fine threads,  But I would personally still tap them as opposed to self tapping with the bolt or screw...

I would also apply teff gell to the threads and a lock washer.

[Dennis M]

Thank you, gentlemen. This is the first I've ever "worked" aluminum for masts.

I'll be using #8 ss screws to mount the tack point and cleats for snotter and halyard. I reckon those are finely threaded enough. Would it also be the case that tapping for this size screw will be the same as for wood?

Also, what type of paint have folks used to coat their masts.

Thanks,
Dennis

[wkisting]

Dennis,

Just to clarify: #8 SS screws can be found in both fine and coarse thread. I'd make sure yours are the fine thread variety (the threads are closer together). In my experience, most local places such as our West Marine store and the hardware store only carry coarse thread in stock. So we ended up fishing a nut up through the mast and actually fastening all the hardware the hard way. Took a long time, but worked. Since you're only threading into the aluminum wall, I think it's very important to make sure you have fine-threaded hardware.

To isolate the stainless and prevent galvanic corrosion with the surrounding aluminum, we dipped our fasteners in 3M5200. The tefgel Ray recommended is probably a better (less messy) choice, but be sure to use something.

For paint, I used Systems 3 WR-LPU on top of the SilverTip Yacht Primer that Systems 3 recommends. I was disappointed to see that it flakes off easily, so the next time I touch up the masts, I plan to rough up the aluminum lightly with 80 grit, then paint on a thin coat of epoxy, then rough that up with 120 grit when it cures, and apply the paint on top of the epoxy. I know the paint will stick better that way, since I've had no problems with the Systems 3 paint adhering to epoxy, and I know the epoxy will adhere pretty well to the roughed up aluminum. Another solution would be to use a proper etching primer on the aluminum.

[hokeyhydro]

When I paint aluminum I use a cleaner and "conversion" prep.  Available at your nearest real deal auto paint store.  I seem to recall the cleaner etched the aluminum a tad, and the conversion coating sometimes turn the AL a faint purple shade, depending on the alloy.  Paint stuck after that.  Did a 10' john boat and several outboard midsection units.

[Bikermouse]

I've used the threaded rivets to great effect on Harley fenders often in the past.  They have a tendency to spin loose when you install and remove the bolt several times, but for a permanent installation like a cleat, I'd think that they'd work well with some blue Loc-Tite on the bolt

[Craig]

Loose rivnuts (acft term) can sometimes be tightened by staking the flange with a center punch. 

[Richard Whitney]

From my experience - thread the screw for anything that is important or has variable pressure on it.  I riveted the attachment points for the snotter  on my CS17 and in a strong gust first the main and later that day the mizzen rivets pulled out.  Changing over to taping (fine) a hole for each screw worked well from that point