Wall "studs" attachment

[Tikvah]

About ready to prepare, or at least plan, the exterior wall framing for the conversion.  I understand running wires, insulating, and so on.  But, how do you typically fasten the wall "studs"?  Do you simply use self taping screws into the side sheet metal?  All I see inside the bus is the thin sheet metal.  Obviously there is some kind of structure behind it.  I don't expect to remove that sheet metal.  So, how and where do you fasten?
Second, How thick do you usually make the walls?

[belfert]

I didn't use anything on the exterior walls other than plywood over the walls.  A stud wall would just make the bus narrower than it already is.  Some busnuts place 1x2s on the walls to add more insulation.

[JohnEd]

Are those typos?  Exterior should be INTERIOR?  And by "studs" do you mean "firing strips"?

You must remove the metal skin inside the bus.  The framing ribs are often rotted of at the base/floor and must be replaced in part. You need to inspect the inside of the wall for rust etc.  Even if you studs are pristine you must insulate the wall and to do that the metal must be removed.  The metal sheets don't get reinstalled.  Plywood gets fixed to the wall with self tapping screws OR better is to attach firing strips to add 3/4 inch thickness to the wall so you can spray foam deeper. 

Visit Gumpydogs site for detailed instruction and pics and examples.  My best advice with that.

John

[Tikvah]

Interesting.  I was told once, I don't remember by whom, to never remove the inner metal skin because that is a structural part of the integrity of the bus. 
Also, if I remove the inner skin, then use spray foam insulation, the foam will be pressed directly against the outer skin.  Is that right to do?

By the way, by "exterior" I mean something other than the inner partitions.  Firing strips (3/4") seem fine, although I had imagined 1-1/2".

Since I'm new to the forum, when I see:

Visit Gumpydogs site for detailed instruction and pics and examples.

, How do I know where and how to find that?

[Timkar]

Here you go....http://bus.gumpydog.com/

[robertglines1]

several years ago I built a MCI 8 that I owned for 10 years. I removed the interior skin and foamed the space and put 3/8 plywood in place of original metal that was inside bus. I ran it many a mile and 10 years it did not sag or fall apart. I have talked to many others that have done the same. Really don't think those few 1/8 pop rivets have more structural value than the 3/8 plywood screwed to the wall structure.   The prevost I'm doing now had masonite 1/8 on it-It's gone now.   Bob

[JohnEd]

Tik,

You are absolutely correct.  Many, many people consider the inner skin on a MCI to be an integral component of the structure.  They believe, and rightly so, that removing the inner skin will weaken the total structure.  The point is that the weakening is not sufficient to cause a problem....on the MCI....so we have been told and has been demonstrated.  You need to remove it to do the requisite inspection of the underlying frame.  That isn't open to serious discussion.  Putting the skin back may or may not be required.  I don't think there are many that have done so and you are hearing from those that didn't that they have not experienced any problem.  be sure that if any of those guys even heard of a problem developing in a MCI that was attributed to the removal of the skin they would certainly have spoken up on the issue.  We do however strongly support trail blazers, every one here being one, so do it your own way and we will help in any way we can.

Whenever you get a term you don't understand you should go to the menu bar at the top of our page and click on search.  "GUMPYDOG" is a prime example.  There are others that have recorded a lot of their conversion work.  Lots of them.  But Gregs site has no peer that I have ever seen and I have been a member and enthusiastic supporter for many years.  Look up "skinner valve" for a starter.

Be well and happy and know that this is the home of helpful and fully supportive fellow bus Knuts.

Your Friend,

John

[artvonne]

Tik,

You are absolutely correct.  Many, many people consider the inner skin on a MCI to be an integral component of the structure.  They believe, and rightly so, that removing the inner skin will weaken the total structure.  The point is that the weakening is not sufficient to cause a problem....on the MCI....so we have been told and has been demonstrated.  Your Friend,

John

  On my MCI 5B I'm now down to the inner metal sheet (skin) that is riveted to the frame tubing and have removed one panel (right front over right front wheel) after drilling out seemingly 100 rivets. Almost every rivet was loose and spun, and/or showed signs of working (smoking rivets). However, it also appears that particular panel had been off before. If I find anymore of this as I work my way through, it would seem those inner panels are much more structural than suggested/surmised. And if I find more loose rivets in the other panels, they are going back in with additional rivets. In fact ive already more or less decided thats what I'll do.

  As an aside, I was working at an airport when a Cessna 210 with retracts came in for an annual. I was down on the floor and used the prop as a handle to get up, when I heard a clunk. As soon as I let go, I heard an opposing clunk, the telltale sound of oil canning. That plane had had the nose wheel collapse some years before and had extensive structural repair to the nose and firewall, and showed a lot of smoking rivets. I brought it to everyones attention, we had half a dozen guys including anIA looking it over, they all concluded it was safe but that float kit wouldnt be a bad idea. I had a lot of confidence in those guys and their opinions, but I wouldnt ever wanted to go up in that airplane

  Metal structures like Buses and airplanes and cars do flex. Stiffening, while seeming the best approach, can have the opposite effect one might think, making the structure so stiff it fails through fracture. Contrastingly, taking out stiffeners, without some kind of engineering to determine the reduced strength and flex, can also have harmfull effects. In this case it may be best to take the oath of Doctors to heart, to wit " first, do no harm." That many have done things to structures and not seen failures is not exactly the best way to answer the question. But on the other hand, sometimes its all we have to go by. Buses are so much more overbuilt than an airplane, considering the intended use, most are unlikely to ever see problems no matter how they go about alterations. As weve seen so often in aircraft, engineering doesnt always pan out as expected, and too often with catostrophic results.

  No rust found in the tubing though, so far.......

[demodriver]

what are smoking rivets?

[artvonne]

what are smoking rivets?

  When rivets loosen up in aluminum they get dirty oxidation around them, like black soot running off of them. Sometimes on aircraft youll see whole sections or rows of rivets with little rings of black around the heads. Especially in high stress areas like wing spars, firewall, landing gear boxes, empenage.

  On an MCI with stainless skin and rivets I dont know if you would ever see it. But a Bus is built like a tank and wouldnt ever flex like an airplane.

[artvonne]

 A better description.

  http://www.mechanicsupport.com/smoking_rivet.html

[Jriddle]

All will have to decide for themselves on removing those interior panels. I choose to remove mine and am very glade I did. I had no rust issues and was able to clean everything to MY standards. I removed floor also. I added cross bracing in the wall in place of the panels. I used foam kits to put foam back into the walls. I used 1"x3/4" pine boards on the metal ribs. Then I put 1/2" pink board on top of the foam. This did two things for me I have extra insulation and allowed me to put wires into the wall. On top of all this I put 1/2' plywood. We have not noticed any problem with the structure of the bus.

In a different post someone mentioned doing it right. I don't really know what is right for others but have my own ideas for myself. I would like to have some of the time back that I have spent converting my bus but it is nice to drive down the road and have people look at the work that has been done thus far. I would not sleep at night if I left the walls and floor intact knowing what I know now about the crude that lurks in those walls and floor.

MY Take

John

[Jriddle]

Here are few more pictures. you can see crude to clean to geting almost done.

John

[JohnEd]

John,

Great job on the spray foam.  Great fitting on the foam board.  Great pics and I hope you are putting together a "Home Page like Gumpy dog".

Why didn't you install the firing strips first and spray foam to their depth?

Did you drill the ribs and inject foam to hold down internal convection air?

Thanks for sharing your work.

John

[Jriddle]

John Thanks
Not sure about the web site like Craig has. I use his web site all the time though. I didn't spray the foam to full depth because I didn't  have the full vision of the project till it was at hand. (I planned as I went.) In hindsite that would have been better. Cost and my location is a factor also. I did put some foam in bus metal structure but not a perfect 100%. I am working on getting the roof done now. I have to say it will look good but I have made mistakes and will have to live with them. (I don't do this for a living and I am developing new skills) I wonder if we all should have our Heads examined for taking on a projects like these. My bus hit my driveway in December of 2007 for the first time.


John