Ladder Mounting Pop Rivets Causing Cracks

[VinceB]

As many of you know, I had my coach painted recently (12 months ago to be exact) and I’m still working thought the final punch list.

The ladder was removed, repaired, and then remounted to the rear cap using the factory holes with S Steel pop rivets. 2 weeks ago I noticed that the fiberglass has a small crack where one of the pop rivets is. The crack is new since the ladder was R&R'd.

I can feel from behind that the pop rivets did not go all the way through the fiberglass and thus expanded inside the hole instead of outside of it. 

I’m thinking that the pop rivets are too short and I’ll eventually have cracks in all the mounting holes.  The paint shop owner says no; that’s the way the factory did it originally.

What say you all?

 

[Ivan K]

I don't know how the factory did it since my ladder is screwed in but I would have used backup rivet washers so that the expansion stop right there and consider redoing it. It just sounds like an expected outcome.

[VinceB]

9 minutes ago, Ivan K said:

I don't know how the factory did it since my ladder is screwed in but I would have used backup rivet washers so that the expansion stop right there and consider redoing it. It just sounds like an expected outcome.

 Yes, that is what I suggested. The problem is that I don't see how one could possibly get backup washers on all of the rivets at the top. You have to be the size of a 4-year-old to climb all the way up inside the cap.

I am wondering if just much longer rivets would simply stop at the fibreglass?

[Ivan K]

3 minutes ago, VinceB said:

 Yes, that is what I suggested. The problem is that I don't see how one could possibly get backup washers on all of the rivets at the top. You have to be the size of a 4-year-old to climb all the way up inside the cap.

I am wondering if just much longer rivets would simply stop at the fibreglass?

Yeah, that is an unfortunate truth up top. I don't know if there is a rule how much longer the rivets need be but certainly would think long enough to be all the way through like you mentioned, to prevent cracking. Or a different method of attaching. 

[Martinvz]

I agree with Ivan in the use of the washers, especially with the ss rivets needing much more force to install, possibly the cause of the cracks, jmho

[Tom Cherry]

Allowing stress crack to propagate will only damage things further.  The cracks need to be stopped.  The only way to do that is to drill tiny holes at the end.

Without pictures, it is tough.  The rivets being too tight, as SS rivets require an ungodly amount of clamping force may not, since the issue is deteriorating, the best method.  Fully understand the constraints of getting behind the cap for a conventional SS nut & bolt.

Perhaps, thinking out of the box…. Fabricating a wooden block that would cover the holes.  Then use a toggle bolt or something to hold or clamp the new mounting block in place.  Lightly grind or sand the area where the block would fit and then extend outward maybe 3/4” in all directions.  Mask off the area.  Then put a coat or fiberglass cloth and resin over the block on the bottom.  Resin coat the body and attach the block to the body and tighten snugly, the recessed toggle bolt screw and let it cure.  Then use FG cloth and overcoat the block and extend the cloth out to the 3/4” mark.  Thus, the block is physically or mechanically (toggle bolt) attached as well as “glassed” on.  Sand and clean up the area.  Use a spray paint (color or flat black) and paint the block and the 3/4” outer band.  Then mount the hardware directly to the block.  The cracks would have been drilled out and stress relieved.  

My concern is that coming up with ways to mechanically attach to the body is going to result in more cracks….the tighter the clamping force, the quicker the area will crack.

[FLynes]

17 hours ago, VinceB said:

As many of you know, I had my coach painted recently (12 months ago to be exact) and I’m still working thought the final punch list.

The ladder was removed, repaired, and then remounted to the rear cap using the factory holes with S Steel pop rivets. 2 weeks ago I noticed that the fiberglass has a small crack where one of the pop rivets is. The crack is new since the ladder was R&R'd.

I can feel from behind that the pop rivets did not go all the way through the fiberglass and thus expanded inside the hole instead of outside of it. 

I’m thinking that the pop rivets are too short and I’ll eventually have cracks in all the mounting holes.  The paint shop owner says no; that’s the way the factory did it originally.

What say you all?

 

I have to agree with your paint shop owner, as the holes on ours are like yours. I was able to take the tail light out on the curb side and visually see that the original rivets never punched all the way through. I'm not saying it's right by any means, but I have no doubt that that's how Monaco did it.

[dl_racing427]

I'd remove the offending rivets, and make an L-shaped probe with small wire to measure the thickness of the bracket and fiberglass, replacing with proper length rivets.

Agreed, if you could access it, backup washers would be best.

Also, drill a 1/8" hole at the end of the crack to stop it spreading.  Hopefully, it's a white area and you can just fill the hole with white RTV to make it less noticeable.

[Tom Cherry]

6 minutes ago, dl_racing427 said:

I'd remove the offending rivets, and make an L-shaped probe with small wire to measure the thickness of the bracket and fiberglass, replacing with proper length rivets.

Agreed, if you could access it, backup washers would be best.

Also, drill a 1/8" hole at the end of the crack to stop it spreading.  Hopefully, it's a white area and you can just fill the hole with white RTV to make it less noticeable.

Gave an opinion prior…. But SS pop rivets can do more harm that good.  Were the original rivets Aluminum?  If so, then try to replace with Aluminum.  I and many others, ask some techs, have created issues by thinking “SS is Better”.  I have a lower slide bracket pop riveted in many spots…a long “brace” if you will.  One or two of the original OEM Monaco aluminum 3/16 pop rivets sheared.  Had a supply of SS.  Popped in those suckers…maybe 2.  OPPS, then I realized that the higher, much higher,  clamping force on the joint had actually bulged or distorted the outside trim piece…. The fix.  Drill out the SS rivets…and then put in some washers to shim or hold the joint uniform…as Monaco installed it.  Then replace with Aluminum…so, just be careful with SS rivets….especially in curved or critical areas.

The SS rivets on the vertical surfaces of the slide wall, the part that moved in and out are FINE for SS….just be aware that the SS will or can distort and there was a reason, in the first place, for the lower clamping or holding power aluminum.

[dl_racing427]

4 minutes ago, Tom Cherry said:

Gave an opinion prior…. But SS pop rivets can do more harm that good.  Were the original rivets Aluminum?  If so, then try to replace with Aluminum.  I and many others, ask some techs, have created issues by thinking “SS is Better”.  I have a lower slide bracket pop riveted in many spots…a long “brace” if you will.  One or two of the original OEM Monaco aluminum 3/16 pop rivets sheared.  Had a supply of SS.  Popped in those suckers…maybe 2.  OPPS, then I realized that the higher, much higher,  clamping force on the joint had actually bulged or distorted the outside trim piece…. The fix.  Drill out the SS rivets…and then put in some washers to shim or hold the joint uniform…as Monaco installed it.  Then replace with Aluminum…so, just be careful with SS rivets….especially in curved or critical areas.

The SS rivets on the vertical surfaces of the slide wall, the part that moved in and out are FINE for SS….just be aware that the SS will or can distort and there was a reason, in the first place, for the lower clamping or holding power aluminum.

What you say is true.
However, for a ladder that will be supporting a human being, I'd want to be sure the attachments are strong enough.
If there's room on the brackets, I'd consider drilling for additional rivets if using aluminum.
Another option could be adding a thin stainless or aluminum plate running cross-ways under the top brackets, with a few additional rivets holding the plate to spread the load.

I've always been a bit nervous when climbing the ladder on my coach. 😱

[Tom Cherry]

30 minutes ago, dl_racing427 said:

What you say is true.
However, for a ladder that will be supporting a human being, I'd want to be sure the attachments are strong enough.
If there's room on the brackets, I'd consider drilling for additional rivets if using aluminum.
Another option could be adding a thin stainless or aluminum plate running cross-ways under the top brackets, with a few additional rivets holding the plate to spread the load.

I've always been a bit nervous when climbing the ladder on my coach. 😱

DITTO.  But did Monaco use SS originally? Are the mounts flush or against a flat end cap surface or on the curve?  I totally feel the same about climbing up mine…but if the mounts were flat against curved and had aluminum before and the fiberglass was stressed by using SS, then odds are….that area needs repairs and building up reinforced FG with no rear access is next to impossible.  We had an expert “yacht” repair guy a few years ago and he taught some of us his tricks…and i have a crack in a curved area that I drilled and filled with sealer…no issues.  But, if it had been a load bearing or mounting surface, cutting it wide open and glassing or putting in a backer plate was the only solution.  This member fixed gaping holes in million dollar yachts…It is a tough job to recreate the original surface.  I built boats as a summer job snd watched our repair folks work miracles ….been using pop rivets for 60 years.  Also the engineer in me says bigger and stronger is better….but sometimes not with Fiberglass…learned from my mistakes 

Not a good situation.  Hope it can be salvaged, but the out of the box way to put on a plate or a wooden mount may be  the only solution.  I guess we see.

[VinceB]

Got the coach back to day and now can post a pic of the crack. 

 

Edited September 2 by VinceB

[Tom Cherry]

13 hours ago, VinceB said:

Got the coach back to day and now can post a pic of the crack. 

 

OK…just my take.  First, were the original pop rivets SS or Aluminum?  Second, that is a long and worrisome crack.  Having had a crack like that on the curved portion of the roof as it transitions to vertical since 2009 and measuring and monitoring…my GUT says….it is gonna get worse.  I would drill a hole in the end…not a biggie…use letter drills and would go below 1/16”.  I did that.  Stopped it dead…for the last 5 years or so.

Cause?  My guess…and only based on what you posted, if the rivets were too short, then you did not get deformation along the body and therefore the shank actually enlarged and stressed the FG.  What to do?  Depends….if there is any way to get behind the mount, then replace the pop rivets with back up washers and a SS bolt.  If that is impossible then I’d replace the rivets.  I would ask others if their factory Pop Rivets are Aluminum or SS.  I don’t have mine at home and never noticed or took note.  

My long handled HD hand tool comes with metric “noses”.  I think 4, 5 & 6.4mm.  That will supposedly handle 6.4 mm or 1/4”.  That would give you 0.065” or so larger hole….so that might overcome the stress on the FG.  Don’t know how large the mounting holes in the flange are….or if you can enlarge.  I’d think about running a sharp drill bit and getting a clean hole….then have a lot of shank or body left and then start to pull down and be prepared to quit and trim off the mandrel.

Once the mounts are back on, seal the crack OR get a “mix your own” resin color kit.  Marine suppliers have them.  You mix the resin with a little pigment (all colors) and then touch up the crack with a toothpick or a wooden match stick….that is how the pros’s do it.

NOW…get other opinions…but that is one method.  You will have to search to get smaller diameter (the flange head) rivets…. OR, chuck up the body of the larger rivet in a drill and spin it and use a file to reduce the diameter to fit or match the flange diameter of the 3/16”.  All sorts of ways to be creative…

[FLynes]

I would think that Monaco was smart enough to know to avoid galvanic corrosion,,,SS and AL don’t mix well at all. My money is that they used AL rivets.

[Tom Cherry]

14 hours ago, VinceB said:

Got the coach back to day and now can post a pic of the crack. 

 

https://www.irv2.com/forums/f258/rivets-that-hold-ladder-on-have-came-out-on-a-1996-holiday-rambler-592918.html

good discussion.  Still gonna need to drill the crack end and touch up.  I had forgot about these…obviously strength needs to be looked at….

Just keep googking and learn from others.  I used “motor home ladder mount pop rivet”.  Maybe someone will look at their mount and do a scratch test and determine the rivet material….

[dl_racing427]

Nice find Tom.  A little pricey, but they look like they'd have a wide grip range, which would work well with the varying fiberglass thickness likely to be found in chopper-gun layups.

[Robert92867]

The inside pass. side of my RV has a 8"x8" inspection cover just below the ceiling over that very same area.  I used it to chase added cables into the ceiling.

[VinceB]

14 hours ago, dl_racing427 said:

Nice find Tom.  A little pricey, but they look like they'd have a wide grip range, which would work well with the varying fiberglass thickness likely to be found in chopper-gun layups.

What am I missing? The grip range looks to be about .787 (20mm). I think we need 2 to 3 ".  Longest I can find is 2.002"

https://www.hansonrivet.com/rivets/blind-pop-advel-rivets/extra-long-blind-rivets/

[dl_racing427]

27 minutes ago, VinceB said:

What am I missing? The grip range looks to be about .787 (20mm). I think we need 2 to 3 ".  Longest I can find is 2.002"

https://www.hansonrivet.com/rivets/blind-pop-advel-rivets/extra-long-blind-rivets/

They shouldn't need to be anywhere near that long.
The fiberglass layup is probably in the 1/4" to 3/8" range, more or less. Ad another 1/8" or so for the bracket and a 5/8" to 7/8" rivet should work well.

I think the tri-fold rivets would be less likely to expand inside the hole and stress the fiberglass.

[VinceB]

17 minutes ago, dl_racing427 said:

They shouldn't need to be anywhere near that long.
The fiberglass layup is probably in the 1/4" to 3/8" range, more or less. Ad another 1/8" or so for the bracket and a 5/8" to 7/8" rivet should work well.

I think the tri-fold rivets would be less likely to expand inside the hole and stress the fiberglass.

It feels thicker but I can't be certain without drilling one out and measuring. I'll do that at some point.

[dl_racing427]

41 minutes ago, VinceB said:

It feels thicker but I can't be certain without drilling one out and measuring. I'll do that at some point.

Bend a short L on a piece of wire, and you can hook it on the inside of the hole to approximate the thickness in that area.
The only way it'd be much thicker would be if it were a cored area, meaning wood or foam with fiberglass on either side.

[Tom Cherry]

Pardon the formatting…..this might be interesting.  It also makes one think that the clamping force needed for the presently instslled SS rivets resulted in the stress crack in the picture….admittedly my conclusion…..

Maybe the simple solution is to drill out and replace with larger 1/4” “tri arm” aluminum rivets and then use the same technique of controlled cinching and not letting the mandrel elongate enough to final “fail” or normally break off.

If you watch the video, the butyl (?) tape/sealer on the back of the mounting plate seems like a good idea….

Look at the screen shot below.  Didn’t know there was a repair kit for the standoff mounts….

 

 

[FLynes]

8 hours ago, dl_racing427 said:

They shouldn't need to be anywhere near that long.
The fiberglass layup is probably in the 1/4" to 3/8" range, more or less. Ad another 1/8" or so for the bracket and a 5/8" to 7/8" rivet should work well.

I think the tri-fold rivets would be less likely to expand inside the hole and stress the fiberglass.

I can't remember if I posted the pic or not, and I of course deleted it from my phone, but I have roven woving on top of the sprayed chop in the areas where the brackets are supposed to attach...I'm pretty sure it's thicker than 3/8".

[Tom Cherry]

55 minutes ago, FLynes said:

I can't remember if I posted the pic or not, and I of course deleted it from my phone, but I have roven woving on top of the sprayed chop in the areas where the brackets are supposed to attach...I'm pretty sure it's thicker than 3/8".

That would gave been my guess.  The boats we made, up to 23 ft and designed for offshore as well, had a layer of Cloth…occasionally special oeder, two.  Then heavy on the chopper gun….then a layer or Roven Woven….different cord sizes like you would expect.  Maybe then a second chopper and finally one or two thicknesses of mat.  But, the interior of the hull was visible.  Can’t remember my MH, BUT, putting in Roven Woven would make sense in critical area where stuff was mounted or curved.  Remove, explore, measure….and if there were support blocks for ladder, they should be visible with a flashlight from inside the engine compartment on the vertical run.

Then, make the call…except no SS, UNLESS carefully cinched and cut off.  Drill and touchup and find your next project.

[Paul J A]

Perhaps a CALL to Stromberg Carlson may provide what they recommend. 

The correct mounting hardware has to be addressed during the design of the product.