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Can rivnuts fix my mast?

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Post Options Post Options   Quote Wobble Quote  Post ReplyReply Direct Link To This Post Topic: Can rivnuts fix my mast?
    Posted: 16 Jun 14 at 5:01pm
I have a Flying Fifteen mast (Selden, about 10 years old) on which the holes for the spreaders rivets have enlarged, leading to wobbly spreaders with (potentially*) unpredictable consequences. 
The holes aren't huge, but they are big enough so that the head of a rivet capable of getting a grip in them is too big for the awkwardly shaped spreader attachment fitting, even after filing down the fitting.
Determined not to shell out for a new mast -- I'm tight, unlike my spreader -- I'm wondering if anyone has had experience of and, hopefully, success in using rivnuts or even rubber rivnuts in this situation, and would welcome any advice on going about the task, especially without having to buy a rivnut tool for the sake of two fixings. 

* The amateur engineer in me actually is not convinced that the spreader moves when the rig has tension, as this tends to force the fitting back into place in the mast. Two other rivets on the opposing part of the fitting (not the opposite spreader) are sound. Maybe I'm being too optimistic, but the boat performance hasn't been affected, yet... If there were an effect, I would expect the boat to beat better on one side than on  the other, and that hasn't happened. 



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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jun 14 at 5:38pm
Can you not simply ream/drill the spreader bracket out for the next size up rivet?
Don't understand what you mean about the rivet head.

Edited by JimC - 16 Jun 14 at 5:39pm
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Post Options Post Options   Quote Wobble Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jun 14 at 6:07pm
Nope. I've already opened it up as much as I can. There's a part in the way... a raised section that connects to the adjuster screw. This is the part which I have already filed to well below original thickness. If I ream/file any more, that will be compromised. 
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Post Options Post Options   Quote craiggo Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jun 14 at 6:41pm
I would say a rivnut would work but the external flange would need to be large enough to seat in the bracket but small enough not to clash with the bracket features you mention. I haven't used any for sailing, but you'd need to be pretty careful with material selection.
I've had a few boats where the spreaders have been bolted on. You need to thread some line through the bolt holes in the mast, then tie the line to the end of a bolt and pull it through. Make sure the bolt is overlength put the bracket on then add the nuts. Use some mole grips to hold the bolt and torque the nuts up. When done cut the bolt down to length. This would work on your boat assuming you can get the nut to fit. It's bloody fiddly though.

Edited by craiggo - 16 Jun 14 at 8:42pm
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Post Options Post Options   Quote piglet Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jun 14 at 7:43pm
What material rivnut? Stainless will erode the hole further, ally might be too soft and plated steel will make 'orrible mess.
Are you already on 1/4" pop rivets? Will they fit in the space?
Craiggos suggestion of mousing bolts through might work, bloody fiddly though.
I've effectively repaired Laser booms by cutting a segment piece from another tube, sliding it inside, then drilling & riveting through the old holes into the new patch piece.
But that sounds worse than bolt idea.
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jun 14 at 7:46pm
You can't cut back part of the rivet head to miss the raised section I suppose? Bearing in mind its larger than the original you could probbly get away with some lost area. I've not come across these rivnuts before: they look intriguing for some tasks, but like craiggo I worry about electrochemistry. Reckon you may be stuck with trying his bolt on a string trick. Arm yourself with lots of patience!!
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Post Options Post Options   Quote timeintheboat Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jun 14 at 9:00pm
When I had the same problem it was as per Craiggo. Mast up against the side of house, up a ladder up next to the mast, very fine thread tied into the bolt thread, pointy nose pliers and a fair degree of swearing. The mast broke elsewhere later, it is in my garden with the spreaders still very securely bolted to it.
Like some other things - sailing is more enjoyable when you do it with someone else
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Post Options Post Options   Quote Wobble Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jun 14 at 12:49pm
In reply to JimC...

No -- it's not just the rivet head but the rivet gun that won't go in there. This isn't such a problem for soft rivets but I have found that the harder ones (can't remember their name) are much more inclined to snap off before fully closed in. Also, the rivet size is limited by the hole in the fitting, smaller than that in the mast. 
Rivnuts would get around that problem as the rivnut size would  be bigger than that of the bolt going into them.




Edited by Wobble - 17 Jun 14 at 12:50pm
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Post Options Post Options   Quote Wobble Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jun 14 at 12:51pm
I think that the cautions outlined above probably are pointing in the direction of Craiggo's bolts and a long-noser. Otherwise it looks as if I might be pioneering the use of rivnuts for this purpose, and I'd prefer someone else to do that experiment!

I can do fiddly stuff as I have been know to lose halyards etc up there before -- just resign to taking an afternoon to do it -- and I can do ffluent swearing too, so it seems I am well-armed to take on this task. I assume the bolt also takes a washer on the inside? 
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Post Options Post Options   Quote transient Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jun 14 at 1:18pm
....some Duralac might be good as well. It'll add the extra frustration of messiness.
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