Mast Stub Rivet Failure - replacement questions

[jplevens215]

Hi All

I had posted a bit ago about the lower part of my tabernacle being riveted to the mast stub that protrudes out of the cabin top. (see post: http://www.daysailer.org/forum/viewtopic.php?f=2&t=4594)

During a recent storm, the rivets holding the mast in place failed (probably in combination with the starboard side stay failing).

I want to refasten the tabernacle to the mast stub, and I was wondering if I could use self tapping stainless steel screws to do the job.

I can reuse two of the holes from the rivets but will need to two new holes. Do you think 4 screws are too many, or are 2 enough? There were 4 rivets, so I was just going to try to replicate this even distribution of load.

So my question is around the need to drill. I am assuming the mast needs to be drilled, but any tips about the casting? Can I use self-tapping to re-use the existing holes, perhaps enlarging them a bit? Any tips on the bit type I should use?

Any advice would be appreciated. I’ve seen in several threads where folks said self-tapping was done, but I want to get some more input, just so a have a well-rounded perspective of the pros and cons.

A bit of a gloomy start to the season, but at least the rivets didn’t fail while I was sailing....

[rnlivingston]

Personally, I wouldn't use self tapping screws on the casting. I think they would rip out too easy. I use aluminum rivets on all my mast and boom fittings and never had a failure.
If the old holes are too mangled to use new rivets, you can drill new holes using any good high speed drill bit. I would use four rivets to hold it.

[Mike Gillum]

I would suggest either Stainless Steel or Monel Rivets as you need something stronger than aluminum Rivets for those kind of connections.
You'll also want to look around for a heavier duty Rivet Gun as both SS & Monel Rivets are harder to set than aluminum Rivets.

[klb67]

I installed new cheek blocks at the base of my DSII mast this winter using stainless steel rivets and a manual rivet gun. I got them in, but I had to squeeze as hard as I could to get the final pop. I'd therefore say it is doable with a manual gun, but if you have access to something better, then use it.

[Alan]

I've used one of these on stainless rivets and it worked fine.

http://www.amazon.com/Stalwart-Long-Arm ... ords=rivet

[jeadstx]

I worked on a DSII last weekend that instead of an aluminum casting it had a stainless steel piece with the hinge plate welded to it. The SS piece had 1/8" thick walls. The hinge plate was a little smaller than I have seen before also. Looks like the jib sheets wouldn't get hung on it as easily.

John