Nut and rivet replacement problems - Fiberglass RV
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Old 06-21-2017, 01:41 PM   #1
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Name: Naomi
Trailer: Scamp
California
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Nut and rivet replacement problems

Hi, I posted previously asking about what rivet size to use which people helped out with. But when I tried to replace some rivets with the nuts inside, the nut locked on but I think the nut was too small, so the rivet head couldn't swell up enough and the tip of the pin snapped off with the length hanging out of the roof.
So my question is, what size nut do I need? I'm Australian and don't understand the sizing I've seen. I've seen #12 is needed, but when I try to buy them they're not numbered, they're listed as "1/4-20 Acorn Cap Nuts, Stainless Steel 18-8, Standard Height, Plain Finish, Quantity 50". That's what I used. But what does 1/4-20 and 18-8 mean?

Thanks all!
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Old 06-21-2017, 04:36 PM   #2
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I don't believe the rivet and acorn nuts will work this way.
The rivet would need to be pulled first and then the acorn nut threaded on the protruding end.
To get a better connection a washer the size of the shank slipped over the end ont he inside and then the rivet pulled to pull the washer up against the fiberglass.
Then you can thread the acorn nut on the end.
The washer is not "needed" but the added area will give more pull through resistance than setting on the fiberglass without it.
For full disclosure I didn't use any rivets on the rebuild of my trailer, but in aircraft work on fairings it is a common practice.
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Old 06-21-2017, 07:07 PM   #3
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Oh, everyone else has said the nut needs to be held in place before the rivet is pulled. But ok thanks, I'll try that.
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Old 06-21-2017, 08:56 PM   #4
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1/4 X 20 refers to the SAE standard (non-metric) measurement for 1/4 inch diameter (6.35 mm) by 20 threads per inch. The term 18-8 refers to the stainless steel alloy that they are made from. It is basically 18% chromium and 8% nickel. The term "18-8" is used interchangeably to characterize fittings made of 302, 302HQ, 303, 304, 305, 384, XM7, and other variables of these grades with close chemical compositions. There is little overall difference in corrosion resistance among the "18-8" types, but slight differences in chemical composition do make certain grades more resistant than others do against particular chemicals or atmospheres. "18-8" has superior corrosion resistance to 400 series stainless, is generally nonmagnetic, and is hardenable only by cold working. That being said, they will still rust, because of the high iron and low carbon content. They are suitable for installation out of the weather, but it isn't your best choice for external applications.

I also would say that it is not necessary to "thread" the acorn nuts onto a compressed rivet after it is compressed. A 1/4" X 20 Acorn nut will squeeze up tightly on a 3/16" (4.7625 mm) diameter rivet during compression. It just needs to be held tightly in place against the base of the rivet "bulb" during the compression action. Additionally, if you attempt to thread an Acorn nut, (or any other nut,) on the rivet after it has been compressed, you risk "spinning" the rivet and compromising your sealant which keeps water out. If you want leaks, just spin a compressed rivet, and that rivet will break the bond of the waterproof sealant you put on it before compressing it. (You are using a sealant when installing these, right?)

And, FWIW, the Acorn nuts are just an adornment, and do not serve to add any structural strength to the rivet's holding power. They are purely for decoration, used to hide the ugly "bulb" end of the exposed compressed rivet bottom.
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Old 06-21-2017, 09:14 PM   #5
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Your problem is your rivet is too long. You need to trim your rivet to the proper length. You need this type of wire stripper.

https://www.lowes.com/pl/Wire-stripp...cal/4294722450

Push the rivet through the snap cap base and through the fiber glass shell of the Scamp all the way through everything you want to rivet. Then put the nut on top of the rivet. Note how much gap is left between the stuff you want to rivet ant the bottom of the nut. You have to remove the amount of the gap from the end of the rivet.

To trim the end of the rivet push the pull pin out of the rivet. Turn the pin around and put it back in the rivet backwards. Now take the wire strippers and choose the closest hole in the stripper that the pins shank will fit in. Using that hole put it on the body of the rivet at the spot you want to cut off. Squeeze the handle and it will trim the rivet without cutting the pin. The pin in the rivet will keep the rivet round.

Now pull the pin out of the rivet and place it back in the rivet proper way around. Now put the rivet back in the materials you want to rivet. Now put the nut over the rivet end and it should go all the way down without bottoming out inside the nut.

Now when you pop the rivet it will swell inside the nut and lock the nut to the rivet and pull some before popping. The rivet when set inside the nut will only pull up about 1/16" because it locks up on the threads inside and wont allow the pin head to pull down the tube of the rivet.
the better you compress the materials together and hold the nut in place the better the out come. Setting rivets inside the trim nuts is a 2 person job if you want to do it right.
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Old 06-21-2017, 09:19 PM   #6
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Quote:
Originally Posted by stevebaz View Post
Your problem is your rivet is too long. You need to trim your rivet to the proper length. You need this type of wire stripper.

https://www.lowes.com/pl/Wire-stripp...cal/4294722450

Push the rivet through the snap cap base and through the fiber glass shell of the Scamp all the way through everything you want to rivet. Then put the nut on top of the rivet. Note how much gap is left between the stuff you want to rivet ant the bottom of the nut. You have to remove the amount of the gap from the end of the rivet.

To trim the end of the rivet push the pull pin out of the rivet. Turn the pin around and put it back in the rivet backwards. Now take the wire strippers and choose the closest hole in the stripper that the pins shank will fit in. Using that hole put it on the body of the rivet at the spot you want to cut off. Squeeze the handle and it will trim the rivet without cutting the pin. The pin in the rivet will keep the rivet round.

Now pull the pin out of the rivet and place it back in the rivet proper way around. Now put the rivet back in the materials you want to rivet. Now put the nut over the rivet end and it should go all the way down without bottoming out inside the nut.

Now when you pop the rivet it will swell inside the nut and lock the nut to the rivet and pull some before popping. The rivet when set inside the nut will only pull up about 1/16" because it locks up on the threads inside and wont allow the pin head to pull down the tube of the rivet.
the better you compress the materials together and hold the nut in place the better the out come. Setting rivets inside the trim nuts is a 2 person job if you want to do it right.
Not saying that it can't be done, but why not just buy the right length rivets?
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Old 06-21-2017, 09:53 PM   #7
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What is the best sealant to use ?
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Old 06-21-2017, 09:57 PM   #8
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There are many, but my personal preferences are Sika-Flex and 3M-4200, especially for things like riveting and thru-bolting. For rebedding windows I use Butyl tape.
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Old 06-21-2017, 10:04 PM   #9
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Because there are too many variables in the shell thickness of both the body and the interior fiberglass. There is also variables in the 2 layers of refltic insulation. (New, old, popped) There is also shape form issues with the cabinet and the arc of the body shell. The issue is the trim nuts thel lock up on the pins an you get very little pull up. If you used a standard rivet and a backing washer the rivet would pull down the tube of the rivet untill everything locks up tight and then pop. The nuts dont allow this. I replaced all of my cabinet rivets with the trim nuts and there were a dozen different lengths needed. Some were fine at 5/8 long and some were over an inch and a 1/4 long. With only 1/16 inch to play with thats allot of different lengths.

This is one spot using machine screws with the trim nuts would do a better job but then your dealing with allot of different lengths but you get about 3/16 inch to play with. You could get the assembly much tighter and a better fit. Rivets are easy to install and cut. Cutting screws and installing them is much harder
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Old 06-22-2017, 07:15 AM   #10
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My understanding of what is happening when you pop a rivet is just as STEVEBAZ relates. For my part, if I want to put an acorn nut on a 1/8 inch rivet I use a #8 nut. The nut is held on the rivet by the rivet diameter being expanded into the threads when you set the rivet. Iím not screwing the nut on after setting the rivet.

The #8 nut has a minor thread diameter of 0.130 inch which is just slightly greater than the 1/8 rivet diameter of 0.125 inch. My process is to hold the nut with locking pliers and press the nut firmly against the surface(s). A rivet alone will try to pinch the layers together as the bulb moves down the rivet (sort of the snake swallowing a mouse analogy). With the nut, the rivet will pop pretty quickly without pinching the joint very much, if any, so the compression of the joint has to come from pressing and holding the nut as tight as possible to the joint. Having the proper length rivet is critical. Often, the end of the rivet isn't visible until after I've compressed the joint in preparation.


Generally, with relatively soft materials (such as fiberglass) a backing washer leads to a better, if uglier, joint. Even so, my experience is that itís best to try to compress the joint with the washer before popping the rivet.

The minor diameter of the #10 nut is 0.145 and will work. Iíve never measured the diameter of a 1/8 rivet that has ďpoppedĒ but I know that the interference of the rivet being pressed into the thread of the nut is much less than with the #8 nut. To my mind, this is why the #10 nuts are prone to falling off.
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Old 06-22-2017, 08:54 AM   #11
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Name: Darral
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MY opinion? Forget the blasted RIVETS like I did. I hate rivets/snap caps for the Scamp and always will....because Scamp did/does not know where to quit. Curtain rods with rivets from the outside??? Get real! I know..here we go again jets are put together with rivets; Scamps are 30 yrs old with rivets.... yada yada....so what??

Ok, I posted some pics in my Flickr photos of how I got rid of the closet rivets that LEAKED and went to this lock nut/bolt configuration. People tell me my Scamp is going to crack like an egg (pun intended) and everything else. 4 yrs and counting- no cracks, NO leaks but still holding strong. Scamp also installed the Catalina awning with locknuts/bolts...why not my closet?? I love this fix and wont turn back. If my Scamp shell cracks in half, I'll junk the Scamp and go get an Escape! That's how I feel about it.

https://www.flickr.com/photos/503516...57633366995497

Quote:
Originally Posted by EscapePod View Post
Hi, I posted previously asking about what rivet size to use which people helped out with. But when I tried to replace some rivets with the nuts inside, the nut locked on but I think the nut was too small, so the rivet head couldn't swell up enough and the tip of the pin snapped off with the length hanging out of the roof.
So my question is, what size nut do I need? I'm Australian and don't understand the sizing I've seen. I've seen #12 is needed, but when I try to buy them they're not numbered, they're listed as "1/4-20 Acorn Cap Nuts, Stainless Steel 18-8, Standard Height, Plain Finish, Quantity 50". That's what I used. But what does 1/4-20 and 18-8 mean?

Thanks all!
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Old 06-22-2017, 09:53 AM   #12
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Originally Posted by Steve L. View Post
...
My process is to hold the nut with locking pliers and press the nut firmly against the surface(s). ...
Great explanation in entirety Steve!
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Old 06-22-2017, 12:00 PM   #13
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Originally Posted by Darral T. View Post
MY opinion? Forget the blasted RIVETS like I did.
You DO realize that by NOT using rivets, like Scamp intended, you are risking tearing a hole in the fabric of the universe and dooming us all?
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Old 06-22-2017, 12:39 PM   #14
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You DO realize that by NOT using rivets, like Scamp intended, you are risking tearing a hole in the fabric of the universe and dooming us all?
Fake News: This is not true, you can install a ground rod attached to your Scamp so you will not get sucked out into space. Now if you have poor soils then sometimes you have to add an additional ground rod on the other side and wire the ground rods in parallel.

Watch out if you have permanently mounted solar panels because if you loose gravitational pull the panels are connected to the sun and the heat can warp and blister the fiberglass shell on your Scamp. Adding ground rods here can help too.

Whether you use bolts or rivets when exposed to the outside you should always wear a cap.
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Old 06-22-2017, 01:08 PM   #15
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Do you attach the Cap with a Silicone coated rivet, or a Dicor coated rivet?
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Old 06-22-2017, 01:29 PM   #16
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Typically there are no pop rivets on those jets!
Some homebuilt aircraft use c pop rivets, but most used driven solid rivets.
Pop rivets have held these trailers together for a long time, but lots have had to replace them too.
They are easy and cheap.
Where you might use the Avon nuts I used elastic stop nuts and screws.
They aren't as "finished" but do pull up tight.
Where I needed to mount something outside and the inside didn't show I used thread certs mounted into the fiberglass.
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Old 06-22-2017, 01:37 PM   #17
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Name: Michael
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Rivets

Replaced all of my rivets with SS machine screws and SS lock nuts, all new snap caps. Took my better half & myself all of 3.5 hours to do the whole trailer (Scamp 19). Still waiting for the World to end.
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Old 06-22-2017, 01:59 PM   #18
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When a rivet starts leaking I drill it out, unscrew acorn nut from the rivet, and replace the rivet with 1/4-20 SS screw of appropriate length. So I reuse the acorn nut. I keep spare 0.75, 1 and 1.25 inch long screws.
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