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Spreading "good" bulkhead apart for cleaning

June 10, 2015, 10:13:59 pm

For those that have done bulkhead work and spread the joint apart for cleaning, how difficult was it?

We all have our opinions, but I am of the opinion that this things were not painted well enough during manufacturing to prevent rust. My bulkheads are in pretty darn good shape and no sign of spreading (maybe one spot that is slightly swelling, but not sure). I do have a couple broken roloks, that are rusty and likely have been that way for a long time. I want to clean the joint and clean/treat it and then paint it with Rust Bullet. Then I will choose my desired method to re-secure (that's not what I want to discuss in this thread).

How hard would it be to spread a "good" bulkhead that is in good shape? I'll get it back in the same place using the existing holes to line it up.



(fixed typo in topic title - Michelle)

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Re: Spreading "good" bulkead apart for cleaning

Reply #1 – June 11, 2015, 12:24:21 am

Krush,

Ours looked to be in great shape with only a couple missing. I left the coach on short blocks as I started. I used two or three flat chisels and with the fairly short distance to the ground, a single jack (type of hammer) was used on the chisels. I started on the right rear, removing the bolts that didn't fail for about a two foot distance. With the bolts removed, a small gap appeared. I spread the gap with the chisel until I had about a quarter to half an inch to work with. I then used a Sawzall with a long medium coarse blade to work up in the gap. An incredible amount of rust particles fell out. As I worked across, I used another chisel to spread ahead of the Sawzall blade. Once clean, it can then be painted or using a small, inexpensive sandblaster like HF sells, further clean the back of the angle iron with care so the sand does not get up into the engine compartment. Once cleaned and painted, the bolts at the end where work started can be replaced but not tightly until you have done a few more inches. The same procedure can be extended across the coach until getting to the opposite side. Bolts can be tightened or replaced a foot or so behind the work as it progresses. Most of the damaged bolts will be found on the right side in line with the tires. The left side may have some that are broken but a lesser amount. The same procedure can be repeated in the front. Care must be taken so not to remove any more bolts at one time than necessary as it could cause the angle iron to try and separate on it's own. See my photos from posts several years ago for the amount of rust that was behind the "clean" angle iron.

This is a good time to figure out what type of bolt and repair you want to do. The Roloks will break just inside where they enter the rectangular tubing. They can't be remove and will have to be sistered with either full length plated, galvanized or stainless bolts. Drilling the new holes requires a pilot hole to be drilled with special length bits and then a larger size bit used. Drilling straight through difficult without creating a bit of an angle even when extremely careful.

Pierce

Pierce

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Re: Spreading "good" bulkead apart for cleaning

Reply #2 – June 11, 2015, 02:27:03 am

I have mine spread out. Almost all the bolts failed as Pierce mentioned, when put  load on it.
Whats the best way to close the gap when I install the new through bolts?
I don't think I can draw the front angle iron and the box beam together by just tightening the new bolts, or can I?

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Re: Spreading "good" bulkead apart for cleaning

Reply #3 – June 11, 2015, 09:24:34 am

Lon,

How wide is the gap? If the rectangular tubing is in good shape, you can install a 3/8" grade 8 with a flat fender washer under the nut and torque to grade 8 specs without deforming the tubing. I tried it just to see how much strength the .125 tubing had. I have been installing 316 stainless with nylocks as I have time and inclination. They require less torque than the grade 8s

So, if you have a one inch gap or so, you can just buy longer bolts, progressively tighten them down and the big angle iron will pull down flat. Then replace the long bolts with the proper length. If the gap is too large, use a couple of chains to the front with a Come-Along close to the back where you can watch as you pull it back into place (one chain to the front, the other hook to the back angle iron with the hooks on the Come-Along on the chains). If you have a couple of bolts through the angle iron, they will make sure all holes line up as you close the gap even if not connected at the far end.

Naturally, this is assuming there is no damage to the rectangular tubing from tank leakage, etc.

Pierce

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Re: Spreading "good" bulkead apart for cleaning

Reply #4 – June 11, 2015, 10:29:26 am

After a couple of PMs, I thought I would add a couple of things for those who have never done the bulkhead bolts.

The big angle iron has no threads, just a hole a little larger than the fastener.

There is a thin metal sheet between the angle iron and the rectangular .125" wall tubing.

The Roloks are fully threaded and cut threads on the near side (next to the angle iron) as well as the far side. This is why they can't be removed if their heads break off. The big angle iron and tubing are only separated by the thin sheet metal (for lack of a better word). If you look at the broken Rolok, you will see the remainder is recessed a tiny amount into the tubing with nothing sticking out to be able to grab onto even if you could get a pair of Vice-Grips between the angle iron and tubing after spreading them apart.

When the fasteners fail, it is almost always about one thread into the rectangular tubing leaving about 95% of the fastener in place. Not that bad as the tubing is still sealed so water can't get inside and rust it out. A $20 borescope can check the inside for rust.

There are special fully threaded galvanized fasteners that cut thread and are used under salt water. A pilot hole could be drilled and the new fastener could tap both sides eliminating the access hole that is normally needed in the foam belly. Not as good as a nut and washer on the far side in my opinion.

If using an acid etch to remove the rust and protect the surface, check the label on any old stuff you may have. Some etching solutions had hydrofluoric acid along with the phosphoric and can penetrate the skin. It can destroy the eye cornea if splashed.  The newer etches should be just phosphoric. It will require frequent applications to remove any light rust left after mechanically scraping.

Quote: "Owing to its low acid dissociation constant, hydrofluoric acid as a neutral lipid-soluble molecule penetrates tissue more rapidly than typical mineral acids. Because of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident, and this can provide false reassurance to victims, causing them to delay medical treatment. HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury."

Pierce

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Re: Spreading "good" bulkead apart for cleaning

Reply #5 – June 11, 2015, 10:34:42 am

Adequate impact gun on the bolts will draw the 2 sides togeother...

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Re: Spreading "good" bulkead apart for cleaning

Reply #6 – June 11, 2015, 11:34:19 am

I have written quite a bit on my method for controlling the gap of the bulkhead joint, both on opening it and closing it. I will try search out one or more relevant threads and post a link later this morning. It is quite simple, but you must realize that there are precautions to to undertake so as not to over do it. There are also possible negative consequences that may not be obvious, so I recommend doing this only if you trust your own assessment of the process and you have thoroughly examined the entire affected area, have raised the coach as high as possible and have the appropriate safety stands.
Don
Edit to add links;
BULKHEAD repair parts checklist
Bulkhead Separation - Planning for the Worst

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