|
|
Post by barbaraeuser on Sept 14, 2019 14:52:47 GMT
I recently bought a used Sunfast 20. The boom vang was held in place by a stainless steel strap that had been riveted into the boom. The rivets have popped out. Can anyone tell me if this is the way the boom vang was originally intended to be installed? Is there a better way?
|
|
|
|
Post by so36idavid on Sept 15, 2019 16:22:41 GMT
I don't know what was intended but it's clearly not working. I would recommend tapping the holes and bolting it back in place. Be sure to use some kind of isolation compound to reduce electrolysis between the stainless machine screws and the aluminum boom. I would recommend Tef Gel.
David
|
|
|
|
Post by MartyB on Sept 15, 2019 17:05:00 GMT
My swag, installed that way. A majority of the items on my mast and boom shaved been install with robots, including baboons bang!
Marty
|
|
|
|
Post by rene460 on Sept 15, 2019 23:24:51 GMT
Hi Barbaraeuser, congratulations on your purchase and welcome to the forum. Many great adventures ahead of you. You will find this forum a great place to hang out and discuss boating.
In my experience, all mast and boom fittings on boats of that size range are pop riveted on, nothing unusual there.
However, stainless steel and aluminium is a combination that results in the aluminium sacrificially protecting the stainless steel if it ever gets wet. I have even see a mast break at the spreader fitting.
A sound installation procedure requires an insulating barrier separating the metals as David mentioned. On my previous boat, a 24 ft trailerable, I watched the mast-maker assemble it all, which was most instructive. He drilled all the holes, removed the fittings and painted the mast, then when the paint had hardened, fixed all the fittings with pop rivets, dipping each rivet in an insulating paste before setting the rivet. That mast was 20 years old when I sold the boat, and not a single issue.
I would suggest drilling out any remaining rivets so you can completely remove the fitting, and completely clean away all the corrosion products. You will have to decide whether to put the strap back in the original location, or move it a bit to have sound metal for the rivets. Pop rivets have to be a firm fit in the holes, don’t be tempted to try and set one in a hole that is too large. If you have to move it, you can either leave the holes after cleaning away all the white powdery aluminium oxide or again after cleaning, fill them with epoxy for a cosmetic repair.
You may be able to fit larger rivets, though that requires drilling the fitting, more likely relocate it a bit one way or the other, or buy a new fitting with different hole locations. The vang is a heavily loaded fitting so don’t put on something smaller than the original.
The friend who had the mast break had expert help to rejoin the mast, and I was fortunate to be there to lend a hand, though I did more learning than anything. They used a clear polythene sticky tape to make an insulating barrier behind the spreader fitting (after repairing the mast of course, but that is another story). And again, every rivet hole was drilled the correct size and dipped in an insulating paste before fitting. Your chandler will have an appropriate paste if the one David mentioned is not available.
With a small boom section, bolts may not be too easy to use, it’s not easy to bolt to a curved section without distorting the tube, but no reason not to go with good sized pop rivets if you are careful with that insulating layer. I am guessing 3/16 SS rivets, which tend to need a man sized pop riveter to set, either quite long handles or the concertina type. Worth buying one so you can do the job in the future, you are bound to need it again. The little hand riveters more commonly available are just not up to the job. Large SS rivets need real force to set.
Please keep us all posted with your progress.
rene460
|
|
|
|
Post by johannes on Sept 16, 2019 8:31:57 GMT
I don't know what was intended but it's clearly not working. I would recommend tapping the holes and bolting it back in place. Be sure to use some kind of isolation compound to reduce electrolysis between the stainless machine screws and the aluminum boom. I would recommend Tef Gel. David A monel pop rivet, correctly installed, is stronger than than a tapped hole + bolt. Jeanneau have been known to use aluminium pop rivets on some boats, and they don't hold well. What size are the rivets that popped out? You can drill larger holes and use larger monel rivets. Monel rivets are stronger than SS 316. Also more expensive, but we are only talking of about 3 euros per rivet or so. |
|
