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Old 06-14-2021, 03:38 AM   #1
Skoolie
 
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Year: 1981
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Engine: CAT 3208 Marine Diesel
Question Structural Anchoring to Walls and Ceiling?

Before my bus gets professionally sprayed foam insulation, I want great structural attachment points to the metal skeleton. I was thinking of drilling holes 1 foot apart throughout every s-channel, and threading through Grade 5 (Grade 8 if I can swing it), 3/8” bolts with nuts, then acetylene weld in place. This would give me structural anchor point to mount cabinets, appliances, fixtures to. The only problem I see with this is having threaded rods protruding into my living space, especially on the ceiling. Even half inch bolts in the ceiling will mess with headroom or ceiling trim.

I then thought about a method where I drill a hole, secure a nut to the backside of the s-channel using a bolt and a lot of washers to secure the nut tight against the s-channel, and then puddle weld the threaded nut to the backside of the s-channel. Then I could have recessed anchor points I could thread bolts or rods into where needed, almost the inverse of the bolt idea. I was concerned about nut warpage making it difficult to thread, and nuts breaking free years down the road. I then thought about making square holes, slotting through short carriage bolts, and welding those in place. I then thought I don’t have enough information and domain experience, so I searched “structural anchor” with the skoolie.net forum search. I then did not find a post or a thread about it so I created this thread.

I want to see what you did. Share photos or a detailed description of your skoolie wall or ceiling structural anchoring solution, and how you secured heavy things to it.

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Old 06-14-2021, 05:49 AM   #2
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By "s-channel" I assume you mean the hat-channel ribs?

I used a variety of anchoring methods in my bus, including some that (I think) are similar to what you're describing. For my subfloor, I welded wood screws upright to the steel floor, then spun 2" lengths of 1.25" oak dowel rod down onto the screws through matching holes in 2" thick XPS foam board. The 3/4" plywood layer was then secured into these dowels with decking screws.

I also did one of these screw/dowel things in the middle of each rib on the wall underneath the windows, although this was less valuable than I had thought. My primary way of anchoring the walls was to attach galvanized c-brackets to 2" deep pieces of 2x4 with wood screws on the backs of each; these c-brackets (which at 1.5" wide fit perfectly over the ribs) were then screwed into the ribs with Teks self-drilling sheet metal screws. I fit pieces of 2" XPS around these 2x4 blocks, into which my 3/16" paneling was then screwed.

My ceiling used 1x2 furring strips running front-to-back every 16" or so, attached to the ribs with Teks wood-to-metal screws (two in each rib or four at the furring strip joints). Insulation was 1.5" XPS packed into the cavities between each rib, then 3/4" XPS over the ribs between the furring strips. The same 3/16" paneling was used for the ceiling, screwed into the furring strips.

For very heavy things attached to the ceiling (like my hammock hooks and the hooks for holding up my hinged desk and table) I attached blocks of 3/4" oak to the ribs with Teks wood-to-metal screws. These oak blocks lie under the ceiling panels at the same level as the 3/4" XPS foam board, and my ceiling hooks are then screwed into them through the paneling (so they look from underneath as if they're not secured very substantially). My overhead storage bins are attached to the furring strips rather than to any oak blocks; if I had my ceiling to do over again, I would make sure I had these oak blocks underneath the paneling for securing the bins, but I did the ceiling long before I had any clear idea of where these bins were going to go so it wasn't possible. As it is, I can hang my full body weight (200 pounds) from these bins so I think they're adequately secured.

All of this in my build thread which is unfortunately very long at this point. Sorry, I'm heading off on a road trip this morning so I don't have time to dig up any relevant pics.

I think using 3/8" Grade 5 or 8 bolts as you describe is probably serious overkill, especially if your interior objects ultimately rely on wood fasteners. The wood fasteners will determine the overall strength of your attachments as they will fail long before 3/8" bolts welded to the ribs will.
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Old 06-14-2021, 10:47 AM   #3
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The airline seat track, aka L-track is great for flexibility later on.

Beware cheap under spec knock offs, you want genuine rated for heavy weights.

Can be mounted vertically or horizontally, all kinds of inserts, female threads, male studs, strapping fixtures

Can DIY, anything with 1" centers

e.g. hinges https://www.mcmaster.com/11175A12/
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Old 06-14-2021, 10:54 AM   #4
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Just use wood-to-metal screws. Easy.

https://www.homedepot.com/p/Teks-12-...E&gclsrc=aw.ds
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Old 06-14-2021, 11:58 AM   #5
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You may be over thinking it a bit. For giggles, I just hung from my ceiling cabinets last night to see if they were going to hold weight. They are framed with 2x2s... faced with 1x4s.. wood screws and glue... anchored in using #12 stainless TEK screws. They didn't even squeak with my 220lbs hanging on the bottom of them.



Good quality screws and construction grade adhesive. The glue is stronger than the wood when cured.


Many ways to skin a cat. Good luck bud!
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Old 06-14-2021, 01:17 PM   #6
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Quote:
Originally Posted by Inner Love View Post
I then thought about a method where I drill a hole, secure a nut to the backside of the s-channel using a bolt and a lot of washers to secure the nut tight against the s-channel, and then puddle weld the threaded nut to the backside of the s-channel. Then I could have recessed anchor points I could thread bolts or rods into where needed, almost the inverse of the bolt idea.t find a post or a thread about it so I created this thread.
Ever hear of Nutserts/Rivnuts? Save you a bunch of labor.



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Old 06-14-2021, 07:26 PM   #7
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A 30 mph frontal crash results in 30G..

That 100 lbs fridge becomes 3000lbs.

Good luck

Johan
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Old 06-14-2021, 08:51 PM   #8
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Take a look at what overhead bins do in a 35 mph front bus crash test.
.

Watch a bunch of 'em before you chose sheet metal screws.
Jack
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Old 06-14-2021, 08:53 PM   #9
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Quote:
Originally Posted by joeblack5 View Post
A 30 mph frontal crash results in 30G..

That 100 lbs fridge becomes 3000lbs.

Good luck

Johan
Yes, good point. Iím using heavy duty D rings and a heavy duty ratchet strap holding my fridge in place.
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Old 06-14-2021, 09:15 PM   #10
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Quote:
Originally Posted by joeblack5 View Post
A 30 mph frontal crash results in 30G..

That 100 lbs fridge becomes 3000lbs.

Good luck

Johan
RVIA uses an 8X loading factor for propane racks. 30X is a bit excessive.
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Old 06-16-2021, 03:26 PM   #11
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I have been working on Inner Love, including myself these last few days and I don’t want this thread to turn into a debate about safety ratios.

O1marc, I haven’t heard of Rivnuts or Nutserts, awesome stuff. With those, even 1/4” looks to be plenty strong.

I’m also curious about how to anchor to the fridge. Is there a way to detect where the refrigerant lines are in the fridge walls for fasteners? Since I’m using a residential fridge, I’m thinking of adhering steel strips to each side with a minimum 2”x4” contact patch (using metal to metal adhesive), fasten it to the studs directly or square tubing, use 1/4” bar stock to spread the load and fasten self tapping metal screws in a grid 1/4” apart. Unless there’s already a product for this.
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Old 06-16-2021, 05:46 PM   #12
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Quote:
Originally Posted by Inner Love View Post
I have been working on Inner Love, including myself these last few days and I donít want this thread to turn into a debate about safety ratios.

O1marc, I havenít heard of Rivnuts or Nutserts, awesome stuff. With those, even 1/4Ē looks to be plenty strong.

Iím also curious about how to anchor to the fridge. Is there a way to detect where the refrigerant lines are in the fridge walls for fasteners? Since Iím using a residential fridge, Iím thinking of adhering steel strips to each side with a minimum 2Ēx4Ē contact patch (using metal to metal adhesive), fasten it to the studs directly or square tubing, use 1/4Ē bar stock to spread the load and fasten self tapping metal screws in a grid 1/4Ē apart. Unless thereís already a product for this.
They make floor clips to keep the fridge from scooting around. I bolted a steel bar high on the back of the fridge and then bolt the bar to the ribs. It ain't going anywhere.
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Old 06-21-2021, 12:55 AM   #13
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2003, we converted a 1997 Ford CF8000 commercial truck to our concept of an ExpeditionVehicle.
.
We bolted through the exterior walls to stabilize our interior -- acoustic insulation against the inside of the exterior walls, then inch pink-board, then two-inch foil-sided poly.
Our visible interior is bright matte Maple 4x8 sheets of veneer.
.
Our bolts are three-eighths diameter, coarse-thread, standardized.
Some are hex-head bolts, some are 'eye' bolts with a loop.
.
A tiny pump of Vulcum 116 at the outside hole.
Nearly two decades full-time live-aboard, summers up rough logger tracks to remote mountain lakes, winters on isolated Baja beaches, and everything is tight and square.
.
Your system may function better for your purpose.
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Old 06-21-2021, 01:30 PM   #14
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In the "new Crown" I installed 4 pieces of Unistrut to surround the fridge. At the bottom of the fridge I installed 2" angle iron (steel) that the fridge rests upon. At the top I am installing adjustable angle iron clamps, that hold down the fridge on the bottom supports. The bottom of the fridge has rollers and feet that are just barely off the floor. The rollers at the rear are mounted to a bracket across it and that bracket and the brackets at the front prevent the fridge from moving front or back. The ones at the top will prevent the fridge from any other movement. There will be plywood covering the sides of the fridge so all should look good. The space above the fridge will also be used. I don't have any good pictures of the completed installation to post yet. Later today perhaps.
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Old 06-21-2021, 04:13 PM   #15
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Quote:
Originally Posted by ol trunt View Post
Take a look at what overhead bins do in a 35 mph front bus crash test.
.

Watch a bunch of 'em before you chose sheet metal screws.
Jack
Wow, never knew they had videos on bus test crashes! Yay! A new topic to watch on my smart tv with my wife (who would rather watch some sappy romance movie on Amazon!) I get the remote tonight dammit!!!

Thanks for the post Jack!
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Old 06-21-2021, 04:21 PM   #16
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Wow, never knew they had videos on bus test crashes! Yay! A new topic to watch on my smart tv with my wife (who would rather watch some sappy romance movie on Amazon!) I get the remote tonight dammit!!!

Thanks for the post Jack!

Yeah watching that... a relatively slow speed crash just took out the driver, and anyone sitting in the first 3 rows behind the driver at best. In my case, that's everyone on board. At that point, I think the fasteners retaining my cabinets would be the least of my concerns. Lol


I'm also building a toy hauler... with how much force was caused by that impact, my jeep will be in the front seats as the chains will most definitely fail. Pretty sure it'll bring all the cabinets and such with it... fridge included.
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Old 06-21-2021, 04:34 PM   #17
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Yep. If as a driver you somehow survive the frontal crash, the refrigerator or TV will do you in from behind! I am a big fan of nuts, bolts, loctite, and Rivnuts. Even more favorable to just welding everything in place but that’s not practical in all applications. Blows my mind when people depend on self drilling screws to hold shite together. It does loosen up over time.
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Old 06-21-2021, 06:51 PM   #18
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Even if your fridge is attached firmly enough to the bus walls that it doesn't come loose in a crash, it seems like people have enough other loose stuff around to provide all the injuries and death you could want in case of an accident (like my personal favorite: kitchen knives on a magnetic block directly behind the driver's head). Just having people riding in the back unsecured (which many skooliers and nearly all RVers do) makes those people into deadly (and possibly dead) missiles themselves.

I have a steel bulkhead wall behind my driver's seat welded to the floor, walls and ceiling, and this makes my bus the only one I've seen that I would want to be driving in a crash (even taking into account the fact that I built it).
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Old 06-21-2021, 07:25 PM   #19
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Quote:
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Even if your fridge is attached firmly enough to the bus walls that it doesn't come loose in a crash, it seems like people have enough other loose stuff around to provide all the injuries and death you could want in case of an accident (like my personal favorite: kitchen knives on a magnetic block directly behind the driver's head). Just having people riding in the back unsecured (which many skooliers and nearly all RVers do) makes those people into deadly (and possibly dead) missiles themselves.

I have a steel bulkhead wall behind my driver's seat welded to the floor, walls and ceiling, and this makes my bus the only one I've seen that I would want to be driving in a crash (even taking into account the fact that I built it).

I plan on doing the same thing. A bulkhead dividing the driver made with steel welded to ceiling and floor along with additional cross supports welded in ceiling. Anything helps. My luck, will be some piece of road debris entering the windshield and impaling me to the seat...
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Old 06-21-2021, 07:44 PM   #20
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I plan on doing the same thing. A bulkhead dividing the driver made with steel welded to ceiling and floor along with additional cross supports welded in ceiling. Anything helps. My luck, will be some piece of road debris entering the windshield and impaling me to the seat...
I'm worried about the rivnuts holding my seat base to its pedestal failing, since I accidentally pulled one out with a screwdriver when I removed my seat temporarily. I assumed the rivnuts were some half-assed post-factory repair, but nope - they make (or made) these buses like that brand-new. Fingers crossed that the forces necessary to fail all eight rivnuts will be enough for the seatbelt to slice me into three pieces anyway.
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