Hang 16 lbs on a skinny inner wall?

[S Sato]

HI All,
I’m hoping to hang a Mr. Heater Big Buddy on an interior fiberglass wall in our 1999 17’ Burro. We’d like to hang the heater on the outside of wall our shower. The challenge is that the shower stall liner is on the opposite side, so we do not want to drill through and destroy the integrity of the shower liner. So I’ll can make blind holes and maybe ½” space between the outer wall and the shower stall liner for anchors. Furthermore the Mr. Heater has a couple “keyholes” for mounting it on the wall. Any suggestions for skinny wall anchors and how to create permanently protruding screw heads for the keyholes? Since the unit weights 16 lbs., am I better off mounting a ¾” plywood board to the wall with 4+ wall anchors and sinking a couple machine screws into the board for the heaters’ keyholes? I'd appreciate any suggestions you'd have.

Steve

[Suz]

Casita uses a corner shelf for TVs that is mounted on the back corner wall. There are two brackets on the top where the shelf hooks in and one on the bottom for a brace. They are all riveted through the wall of the trailer. Although some do, they recommend not traveling with it in place, but it is easy to remove and put up.

Something like that might work.

My worry would be having the heater up where it could fall off.

[Donna D.]

Since heat rises, I'd put the heater down low. Otherwise you're liable to have a hot head and cold feet. And since you won't be using the heater in the summer months, I'd make certain it was a quick-in, quick-out mod.

My 2 1/2 cents.

[Suz]

I'm with Donna. These eggs heat up pretty quickly.

[Harvey Craft]

I set my heater just in front of th closet. It was a little to tall and hampered the closet door from opening so i removed th handle and now it fits just fine.

Harv in Colo.

[S Sato]

Ooops forgot a few background details...

re: putting heater down low rather than up high
We've got dogs and we're concerned that if the dogs brush against the heaters, their coats will singe. So our solution is to mount the heater up high, thus we are looking at using only propane heaters with fans, so we can place it up high and still get heat down low. An alternate is to use a heater without a fan and use a seperate fan (higher hassle factor). When we have AC power, we will use a cube heater, and since the heating element is so well guarded, are less concerned about the dogs.

re: concerned about the heater falling down
I'm concerned about having so much weight permanently mounted too, so we plan to unmount and stow the heater when we move the trailer.

[Steve L.]

These might work for you. The top row. Perhaps the AR series. All seem to use a threaded insert to collapse the rivet behind the wall. The AR are(!) interesting, but the smallest size is 1/4-20. The AK goes down to 10-24 which seems to be a more reasonable size.

Threaded rivets

The AR appear to be easiest on the fiberglass. I can't tell from the video exactly what's going on with the AK. You want the rivet to collapse from the back. The AK's might expand the hole although there appears to be some sort of sleeve.

Don't know the cost. Perhaps too much.

[Steve L.]

http://www.hweckhardt.com/avk.pdf

Hmm. the 44 page PDF file suggests the AR style is best for plastics and it doesn't need special installation tools. However, its a fairly large bolt size and it needs about an inch of back space, less as it collapses.

Interesting, something to file away for the future but perhaps overkill for your application.

They make some fairly short hollow wall fasteners. Maybe they'd do the trick. I'm thinking of the ones that mushroom open behind the wall and use machine threaded fasteners instead of wood screw types. Hollow Door Anchor

[Jackie]

I don't know what type of fasteners you should/could use, but possibly a shelf like this might be the answer. You would have hooks underneath for coats, towels, etc. You could use heavy-duty velcro or some type of clamp (like those used to hold brooms to walls) to hold the heater when in use, and remove it for transit.

[Benny K]

The problem with the hollow door/wall anchors is that they have to be all the way in before you collapse them and the space between the wall and the shower stall liner may be too shallow....Maybe if there was enough deflection in the stall material to allow for the length of the anchor before tightening it would be great because they grab on a fairly large area behind the fiberglass and also would have to be careful to shorten the screw a couple times while tightening because it`ll protrude thru quite a bit and possibly push thru the shower liner......the threaded rivets, which I used to use under the brand Rivnut, have a very small OD in behind, when collapsed, and work best in metal but think that they may work in fiberglass as long as you didn`t forget about the heater and drove off....the bumping would probably pull thru the fiberglass in short order.......am wondering if some sort of non porous mount, stainless possibly, with bent hooks along the bottom edge, about maybe about 8x8" or so could be stuck to the fiberglass with silcone caulking and then mount the heater to that....silicone caulk makes an excellent adhesive on an area of 2 flat pieces together......running out of wind....Benny

[Byron Kinnaman]

I've seen a number of schemes for attaching stuff to the fiberglass walls. This product is an adhesive tape. It seems to me that this stuff would work quite well. Not to scare you all, but it used on airplanes.
We use it to hold a 2" round gauge to a truck mirror. After it's been on there a few days you'll break the mirror before the gauge will come off. You can find out where to purchase here!.

It's something to consider, or at least look into.

[Gina D.]

VHB tapes are indeed wonderful stuff.

We use it here for modifications in some pretty high heat areas and after initial set (In our appliccation, about a minute) you cut lift an entire amplifier (40 to 80lbs) by just the small part you have attached.

I walk directly across the street to Aircraft Spruce and Specialty and pick it up when needed, but it is NOT cheap.

If you choose to go this route, make sure you read the specs, there a foam backed ones and double sided ones. Choose the right one for your application.

In this case, straight double sided is what you want. The foam will fail eventually if you use it in a "bouncy" trailer, but guarranteed the sticky stuff will still be on your walls and heater when the foam rips away!

[S Sato]

The tape sounds like great way to go! I'll need to make sure I really, really have the shelf positioned right and that I want it permanently there!

Steve

[Pam Garlow]

I also would worry how much the fg wall will flex when this unit is attached. Say you bump it when you are carrying in supplies before a trip, the fiberglass could crack at the mounting holes. Maybe you can combine a 'backer' of 1/4 " plywood, attached to the wall with anchors/cement. Then you attach through it. If you make a larger panel than you need, the additional wood surface can provide more wood backing for other uses. "Spreading the load' out would reduce the strain on the fiberglass. (I assume this is a zero clearance with a heat shield since you are considering attaching it directly to the fg wall.) If you are concerned about the heat, a shield can be installed between the back of the furnace and the wood panel.

[Byron Kinnaman]

One of the good things about using VHB is the weight distribution. Stresses aren't concentrated in a couple spots.
If you're thinking about using VHB you might want to try and find a local 3M rep. One of the links about should lead you to a local rep. If you talk nice to the rep he might even be able to get enough sample material to do the job.

[Steve L.]

In the category of “the same thing, but different”, the top of the inside pull handle on the entrance door pulled out on my last trip. The pull handle, separate from the actual door handle, is screwed into the door. I don’t slam the door, but rather pull hard and quickly and it catches the lock.

I was pretty distressed. I popped the plastic screw cover and found a fairly long wood/machine screw. I screwed it back in and it seemed solid. I was afraid it had stripped the hole but apparently it had only backed out. If I were building the trailer, there would be a wood backing glassed inside the door for better (longer) grip.

Because of that incident and this thread I’ve been looking more closely at attachment schemes for hollow walls.

The hollow wall anchor is still an option, although I’d have been happier to find one in stainless steel as it’s a potentially damp area. Still looking. Also, the ones with beefier bolts seem to be pretty long. I figure I have about an inch of back space. They do make fairly short hollow wall anchors in the smaller bolt size.

The rivet nuts are still attractive to me but I feel the crush strength of fiberglass is not that great so I wonder if I would enlarge the hole in the fiberglass while trying to collapse the back of the rivet. They make a polynut rivet that has a plastic sleeve that does most of the swelling but I’m concerned about the pull out force. Good for hanging a heater on the wall I’m sure, but a door handle? I believe they come in both steel and aluminum sleeves. I suppose aluminum would be okay since there are (much smaller) aluminum rivets all over the trailer. It does seem to need a special rivet gun (of course I’m always open to a new tool). Lastly, they tend to be fairly large bolt sizes. I have a limit to the size I can make the countersink in the door handle.

Oh well, the search continues.

[Brian B-P]

...does seem to need a special rivet gun (of course I’m always open to a new tool)...

My manual rivet nut insertion tool works like a regular blind rivet puller, but instead of jaws to grip the rivet mandrel it has a threaded stud to go into the nut. It looks like this one: Wicks - RIVNUT TOOL 8-32, 10-24, 10-32. As with rivets, there are a selection of nosepieces with different screw sizes which interchange on the same tool. Compared to power tools, this is a cheap device, which could possibly be justified by a single use if it did just what's needed.

Aircraft Spruce and Specialty - Tools - Rivnut Tools and the Wicks page shows some strange tools for this purpose. I think the weird wedge-based tool at the top of the Aircraft Spruce page is about the price I paid for my squeeze-handle style tool (approx $20 Cdn, or maybe more, but it came with a bunch of nuts).

Today I found this interesting link: Pulling Rivnuts without a Rivnut Tool I have not tried this, but at a quick glance it makes sense to me.

...Lastly, they tend to be fairly large bolt sizes.

I don't know what other people consider "fairly large bolt sizes", but my tool has sizes including #8, #10, and 1/4" (and one or two more). I find that the smaller thread sizes don't have enough threads in the nut to work well in aluminum: that is, it is too easy to strip the rivet nut threads by squeezing the tool just a bit too hard when setting the rivet nut. I have even had this problem with the 1/4" size, but the solution in some cases is just to use steel instead of aluminum.

The large required hole size is a problem with almost any hollow-wall fastener, as the hole needs to clear the fastener thread plus some more working space for the rest of the hardware - in this case, the nut thread plus the surrounding wall of the nut body.

I have only installed one item in the Boler with these fasteners; I bought it for an automotive job.

[Gina D.]

If you are still thinking about the tape, the link above for Aircraft Spruse and Specialty will be useful. They sell it.

It is across the street from where I work. I have walked over there and bought it off the shelf before.

OK, on particularly lazy days, I drive across the parking lot....

I also see samples on eBay all the time

[Steve L.]

FWIW, here's a few photos of the rivet nuts. The front shows the styles that came in the sample kit with a 3/16" dian x 1/2" (uncompressed) rivet for comparison.

From left to right is 6-32, 8-32, 10-24, two 1/4-20 and a rivet. They're installed in 1/16" brass as that was all I had that was less than the 0.80” for these particular rivet nuts.

You can see the flush mounted head and the flanged head. With high torque, I believe the flanged head would be better. They also make a ribbed body that is better for torque resistance for which I'm looking about a local supplier.

As I mentioned, these samples are intended for 0.80” gauge maximum. I’m getting 0.130 gauge max samples which I believe will handle most thickness in the Casita. More checking of wall thicknesses to come when it’s not so cool outside.

The A and S's scratched on the material are aluminum or steel. I wouldn't use the aluminum ones for much. Like Brian, I was a bit of a gorilla on the 6-32 aluminum thread and pretty much pulled/stripped the thread right out.

[Steve L.]

This back picture just shows the bulge that forms during installation. I don’t believe these are intended to hold layers together.

The last picture is more in profile. The maximum height shown is 3/8” after crimping.

On the (w)hole, I’m feeling optimistic about this as an option for the door bolt replacement assuming the extended thickness rivet nuts are suitable.