Rivets - removal, riveting, tools, etc

[tenuki]

I have some work to do on my boom and mast which will involve removing rivets and re-riveting, etc. I'm looking for advice.

1) How do I remove rivets safely and without messing the holes up?
2) What are your recommendations for rivet guns and rivets?

I have a Ranger 24 that I'm re-commissioning so it's not a huge boat with big loads or anything but I want to do it right. The first project is straightening out the boom control rigging stuff (vang, outhaul, reefing, etc) and I need to get the cap off to re- rig the outhaul. The second thing is taking out a sheeve box at the base of the mast and replacing the broken sheeve (6 riviets hold the current box in)

I searched the forums, but couldn't find advice on rivet removal.

[DeepFrz]

You will have to drill the rivets out. Use a drill bit just slightly larger than the hole in the rivet. Pop rivet tools aren't very expensive. When you are finished riveting take a small pin punch and knock the center pin into the boom (hopefully you will be able to get them out of the boom after). Fill the hole with sealant (Sikaflex 291 or some such). You can use something like Duralac or Tef Gel to bed the rivets to prevent corrosion, although if you are using aluminum rivets there shouldn't be any problem.

[poopdeckpappy]

Working on my boom also and I did the same as mentioned above.......a piece of cake

[sailingdog]

Tenuki-

If you are going to do this, drill the rivets out as suggested... but go down to sears and buy their Craftsman heavy duty pop rivet tool, which is about $25 or so. It is one of the few manual pop-rivet tools that can handle stainless steel pop rivets up to 3/16" in diameter.

If you're going to be drilling new holes for the new hardware, fill the old holes with thickened epoxy... and then sand it flush. If you're going to be using the old holes. Coat the rivets with tefGel, lanocote or some other galvanic isolation compound to help prevent corrosion between the stainless steel rivet and the aluminum mast.

However, if the hardware is stainless steel, you should also use a thin sheet of plastic as a galvanic isolation washer, like the plastic from a plastic milk carton, which is low-density polyethylene.

Finally, I don't recommend using aluminum rivets on a boat for several reasons. First, they are more likely to fail due to corrosion issues. Second, they are much, much weaker than stainless steel rivets of the same size. Third, they are also far more likely to fail due to deformation.

[DeepFrz]

I agree with almost everything that sailingdog says
except do not use plastic as a galvanic isolator.

instead use an adhesive sealant such as Sikaflex 291 or 3M 4200 (not 5200).

If you are riveting high stress items use stainless or Monel rivets and set them in Duralac.

[stevemac00]

Is your mast/boom painted? I'm not sure how long the epoxy will last if it's not painted.

In my opinion Dog's pretty much got it right. I'm removing a behind the mast furler with a lot of rivets. The thing I'd clarify is you don't want a stalactite of epoxy hanging inside. Use a countersink to slightly countersink the holes as a base for the epoxy. You can get aluminum "putty" (epoxy) from McMaster but it's expensive. I'm using standard West 105 but adding sufficient filler to be thick. Use 420 aluminum filler (WEST SYSTEM Epoxy) which has some UV protection and is base for paint.

[sailak]

Hi guys. New here on the forum, learning a lot!! Hope to own a boat soon.

Why fill the old rivet holes? Is it aesthetics? or a structural thing?

Thanks.

Dale

[sailingdog]

DeepFrz-

The boat is a Ranger 24... I don't see any of the loads being all that high on it ever... it just ain't that big a boat.

Sailak-

You want to fill the holes to reduce the amount of water getting into the mast. Also, the holes will have rather sharp edges and can chafe lines or skin that rubs against them....which doesn't happen if they're filled and sanded flush.

[tenuki]

So on stainless vs aluminum rivets, it sounds like here are the pros/cons

aluminum - pro: easier to rivet, no galvanic corrosion, easier to drill out
cons: less shear and tensile strength

stainless - pro: better sheer and tensile strength
cons: hard to rivet, galvanic corrosion, [edited] hard not impossible[/edited] to drill out


Seems like I should be able to find aluminum rivets that are strong enough for my little R24? Stainless seems to have so many disadvantages over aluminum that I'm shy of it. It looks to my inexperienced eye like the factory rivets are all aluminum (but I haven't tried drilling em yet either).

[tenuki]

further research show the following info (please note this is general and out of context info, not a engineering study or anything)

Looks like for 3/16 rivets (varies greatly with brand):

Aluminum - ~300 shear, ~500 tensile
Stainless - ~780 shear, ~1040 tensile

So stainless is clearly over twice as strong. Now I'm wishing I had my good ol' strain gage from my engineering materials class for my next sailing session. Anyone know the size of forces generated on say a out haul block on a 24' sailboat?