bulkhead blues

Topic: bulkhead blues (Read 9760 times) previous topic - next topic

bulkhead blues

July 02, 2012, 02:24:13 pm

I have been visually inspecting my bulkheads for several years, and have not seen any sign of failure. I have not put a torque wrench on any of the bolts. I have decided that this fall, while passing through nac I will have
an expert deal with this nagging, impending doom type of worry.

my question is: if some of the bolts are broken, is it better to replace with larger diameter roll locks or to put in through bolts with nuts? grade 8 bolts with nuts would seem to me to be more of a permanent fix, but I
would like to know what others have done? would you recommend the factory, extreme or m.o.t. for this surgery.

Re: bulkhead blues

Reply #1 – July 02, 2012, 02:54:03 pm

Wayne,

I think a lot of the "bulkhead issue" has been blown well out of proportion.

Bulkheads do not just up and "fail". They fail one bolt at a time which puts more stress on the bolts on either side of the failed one. Sure, if neglected long enough that 5-8 bolts in a row fail, you can have a bulkhead issue. More related to owner neglect than a "doom and gloom" failure.

The method I like better is to either:

1. Remove the broken bolt (usually penetrating oil and then double nutting makes removal from the inside (access hole in bottom/coach underbelly), over-drill and thru-bolt with 3/8" grade 8 bolts with large washer on box beam side (as I outlined in the bulkhead article).

2. "Sister" the broken bolt. In other words drill and through bolt on either side of the broken bolt.

My suggestion is to not fret over it, but to use safety stands and take an inch/pound torque wrench and 15 minutes of your time to VERIFY the status of the bolts as well as to look for possible separation or evidence or rust in the two bulkhead areas.

If considered as a part of your annual maintenance, it takes very little time or dollars to keep your coach bulkheads in good condition.

Brett

Re: bulkhead blues

Reply #2 – July 02, 2012, 03:34:16 pm

Quote from: Wayne Macauley – July 02, 2012, 02:24:13 pm

I have been visually inspecting my bulkheads for several years, and have not seen any sign of failure. I have not put a torque wrench on any of the bolts. I have decided that this fall, while passing through nac I will have
an expert deal with this nagging, impending doom type of worry.

my question is: if some of the bolts are broken, is it better to replace with larger diameter roll locks or to put in through bolts with nuts? grade 8 bolts with nuts would seem to me to be more of a permanent fix, but I
would like to know what others have done? would you recommend the factory, extreme or m.o.t. for this surgery.

I never liked the factory method of attachment for the bulkheads. I contacted Linadapter for their advise. They use the blind bolts on skyscrapers to underwater installations. I bought a set of HB Hollo-Bolts at Lindapter - USA and Canada in the optional galvanized finish @$9/each. There site has a lot of engineering PDFs and videos on how the Hollo-Bolts work. My pit will be ready for the weight of the U300 in a week so will post photos of my installation. Here is the page for the size I bought along with videos, prices for zinc, galvanized and stainless: 1/2" Box Bolt Size 1 - Box Bolt? / Hollo-Bolt® - Connectors - Simplified The center bolt is 1/2" but the total size is quite a bit larger. A couple of box ends and a torque wrench are all that is needed to install (after the hole is drilled).

Slide show at: Box Bolt - Expansion Bolt for Structural Steel Tube - Steelwork, Cavity Fixing

Pierce

Re: bulkhead blues

Reply #3 – July 02, 2012, 03:36:12 pm

As I do not have the tools, skill nor the competency to perform this job I had Xtreme re-do the front & rear bulkheads in my 97 U270 this past June. You having a 98 coach should also have this type of inspection & repair done by professionals like Brett W.

, or MOT, FOT or Xtreme. BTW Xtreme will do either Grade 8 or SS through bolts/nuts/washers.
Peter

Re: bulkhead blues

Reply #4 – July 02, 2012, 05:03:40 pm

Pierce, That looks like a good solution that any of us could use.
Question, Does install require drilling a larger size hole than is already in the bottom member ?
Does the thickness of the materials to be attached matter ?
Please let us know how process works. I would much rather do this than drill or cut holes in the fibreglas and than have to reseal them.
Gary B
Pierce, On Edit
I read the brochure and see that a 13/16 hole is required. Gary B

Re: bulkhead blues

Reply #5 – July 02, 2012, 05:20:34 pm

I believe that whoever said "it's not a question of if, it's a question of when"
was correct regarding bulkhead failure. I have seen plenty of coaches with
the plugs in the underbody, which I think indicates that they have been
through bolted. the failure rate may very well be overblown.
It would be nice to know how many coaches have been treated prior to
having a problem vs. how many coaches have had problems and also
those that haven't been treated and have no signs of problems.
perhaps someone with more computer savvy than me could start a poll
that would shed more light on the issue.

Re: bulkhead blues

Reply #6 – July 02, 2012, 05:28:16 pm

13/16" hole size for the 1/2" bolt is getting pretty large.

Re: bulkhead blues

Reply #7 – July 02, 2012, 05:36:21 pm

I like the idea of the bolts you are using Pierce but question the strength of using just one wall (cross section) of the sq tubing that I believe is used behind angle iron. The combined box section of the sq tube is stronger going all the way thru it and using a plate that is the same size (or bigger) as a backing, in my opinion would be much stronger than just using one wall thickness to hold on to!! It all depends on the thickness of the box wall as to how much strength and "holding capacity" that sq tube has. The bolts are fine but if there is not much to hold onto they will just "rip out" Having said this I am only going by what I presume the build up of the framing is like. I would be interested in seeing a cross section of the make up of that area if anyone has a drwg or knows what it is like and can post a sketch.
John H

Re: bulkhead blues

Reply #8 – July 02, 2012, 05:37:21 pm

Dave H, That is why I was asking, that is a very large hole for this area. I believe that Brett W recommends a 3/8 bolt which would be about 1/2 the size of this bolt.
Gary B

Re: bulkhead blues

Reply #9 – July 02, 2012, 06:00:12 pm

I also seem to remember that the square stock is light duty - say conduit type grade? Wasn't the torque spec in inch pounds? Even the 5/16" assembly calls for 18 ft-lbs which could crush the square stock.

I think the concept is cool! It may be heavier duty than called for. The question is what happes if you don't meet the torque spec - would it back off?

Re: bulkhead blues

Reply #10 – July 02, 2012, 06:47:37 pm

Rolok Torque values for their 5/16 18 tpi bolt with a 0.290 hole are 10 ftlb to drive (make threads), 21 ftlb to tighten, 45+ ftlb before failure, 15 ftlb to loosen.

Wayne
I will bring my Jet 250 inch pound torque wrench to Qualicom Bay in July and you can check your bulk head bolts then.

Re: bulkhead blues

Reply #11 – July 02, 2012, 07:04:40 pm

John et. al. I don't have time at the moment for a long post, but since I have some experience with this issue, I feel obliged to respond with my thoughts and some first hand knowledge about the bulkhead design.

When I first encountered the issue on our coach, I felt like the joint was under engineered and that the Roloks were like a glorified sheet metal screw merely designed to make assembly easier and quicker. Although I still feel that the joint is somewhat under engineered, the Roloks grip both vertical walls of the tubing because they cut their own threads while being installed (or rather roll their own threads... an important distinction which you can read about if you do a search on rolled threads). Since the threads are simultaneously engaged in both walls at the same time, there is no crushing force brought to bear on the tubing. Since this bulkhead joint tube is an eighth inch thick, both walls of the tube add up to 1/4" worth of thread bearing surface. According to ARP (American Racing Products) product info which you can easily find online, increasing the thread contact area more than the diameter of the bolt has very little effect on the strength of the joint, so the method used by Foretravel is a theoretically sound one given the number of fasteners involved (17) in our coach) in the joint. Also, the Roloks are very high strength fasteners (140,000PSI if memory serves me).

That said, I believe that through bolting with appropriate 3/8" bolts (In my case, I chose ARP 170,000PSI Stainless steel fasteners) and the fact that my entire tubing assembly in contact with the bulkhead joint is doubled up with 1/8" square tubing mostly backed up by 3/16" angle iron and secured with weld nuts for future removal if necessary, should preclude any future need to be concerned with the joint. I am attaching a picture of my coach after some of the rusty metal has been removed. I have posted many other pictures of the area in question, both before and after my repairs. This shot is taken from the street side with the right side being towards the rear of the coach. You can see the opening for the sewer hose compartment in the lower right side of the picture. The square tubing that bolts to the bulkhead is one continuous 1/8' thick walled piece of square tubing. Most all of the rest of the tubing is only 16 gauge.

The reason I still feel that this joint is still a bit under engineered is that this joint represents the transition from the traditional heavy framing that carries the engine and trans assembly, as well as the suspension (at least in coaches up to and including my year and possibly a few years newer), I feel that there should have been some more steel connecting engine side of the bulkhead and a few more gussets to take the load from the rear locating arms which pushes and pulls on the bulkhead joint with quite a bit of leverage in the area where the shackles are welded to the 1/4" angle iron. That said, I do feel like the Roloks are up to the task when they are protected from moisture and corrosive elements.

:Edited for clarity
Don

Quote from: John Haygarth – July 02, 2012, 05:36:21 pm

I like the idea of the bolts you are using Pierce but question the strength of using just one wall (cross section) of the sq tubing that I believe is used behind angle iron. The combined box section of the sq tube is stronger going all the way thru it and using a plate that is the same size (or bigger) as a backing, in my opinion would be much stronger than just using one wall thickness to hold on to!! It all depends on the thickness of the box wall as to how much strength and "holding capacity" that sq tube has. The bolts are fine but if there is not much to hold onto they will just "rip out" Having said this I am only going by what I presume the build up of the framing is like. I would be interested in seeing a cross section of the make up of that area if anyone has a drwg or knows what it is like and can post a sketch.
John H

Re: bulkhead blues

Reply #12 – July 02, 2012, 09:39:33 pm

So the engineering was ok. Just not sealing the area for corrosion.

I told Triana in oct 87 I did not like the fasteners but he swore they were fine. They were. Just not the installation.

If and when I get to Nac I will remind him of that original unihome tour I was given as the california sales manager along with my brother managers and my comment. I absolutely think he would remember. I remember the room like yesterday. Cursed with a good memory. I tried.

Bob

Re: bulkhead blues

Reply #13 – July 02, 2012, 10:49:57 pm

I always thought that good engineering/design had to take into account the operating environment of the vehicle including but not limited to moisture and chemical exposure, temperature, stress, vibration and design lifespan and should not be limited to a single item but all components of that assembly.

If these failures/separations had happened in an aircraft, the FAA would have immediately issued an air worthiness directive (AD note), required the manufacture to come up with a fix and notified all owners. Guess a bunch of retirees rolling down the road don't rate.

Not all Foretravel owners should be expected to have the mechanical expertise to determine if they are suffering any bulkhead deterioration and can't be faulted for not being able to crawl underneath and inspect it. Age with accompanying stiffness has limited many of us to the role of an armchair mechanic. Without my new pit, I have been very limited to the time I could spend under the beast. Owners may however, want to have a knowledgeable person occasionally check this area visually and with a torque wrench, perhaps when the chassis is greased or the brake pads checked. This is particularly important for coaches operating in northern states with salt used on the roads.

In a couple of weeks, I will post photos of my modification with borescope shots of the tube interior condition and what the installation looks like from inside.

Pierce

Re: bulkhead blues

Reply #14 – July 02, 2012, 11:14:52 pm

There is a 1-1/2" square tube running side to side inside the rear of the bay floor. But what is not being mentioned is that there is a second (or third) 1-1/2" square tube against part of the length of the main side-to-side square tube.

Using a 3-1/2" or longer bolt to fasten the rear angle iron to both of the square tubes offers a secure repair.

Cutting backing plates from 1-1/2" steel flat metal will force the bolt & nut to put compression on the edges of the square tubing which helps reduce crushing the tube.

RoIocks with our bay floor design are KNOWN to fail over time. Using any other blind fastener will not work either. The problem is the tube in the floor is too weak to start with, and further weakens from rust as coach gets older.

In some situations, the rear tube is also know to break loose from the rest of the inner floor structure, so even bolts & nuts will not work when that happens.

New Foretravels have a better design in their inner floor structure and use blind fastener HuckBolts. I heard that Foretravel is now repairing older coach's bulkhead problems with HuckBolts, which I think is not a good choice because all blind fasteners can pull out of rusted, weakened inner-floor tubing. Foretravel has also used new Rolock bolts to repair bulkheads. I think some solutions are designed to pacify owners, speed up repair time and satisfy attorneys, rather than be the best in the long run. For a while we heard that bulkhead problems were caused by owners.

I have seen repairs that cut through the bottom of the floor to the rear of the rearmost 1-1/2" square tube and use 2" bolts & nuts to hold things together. This method cuts through a second square tube and removes the support the second tube offers.

Also some use stainless steel bolts, which will not rust, but are not as strong as grade 8 bolts. Stainless may be better though, as a rusted grade-8 will weaken over time.

There are many different solutions to bulkhead problems and many opinions offered by coach owners. And professional's solutions seems to change from time to time.

It does not help that fresh water tank overflows onto bulkhead, insuring it gets wet. Bulkhead repairs should also include strengthening the vertical steel braces, like was included in later designs.

Re: bulkhead blues

Reply #15 – July 02, 2012, 11:50:14 pm

Quote from: acousticart – July 02, 2012, 07:04:40 pm

Although I still feel that the joint is somewhat under engineered, the Roloks grip both vertical walls of the tubing because they cut their own threads while being installed (or rather roll their own threads... an important distinction which you can read about if you do a search on rolled threads). Since the threads are simultaneously engaged in both walls at the same time, there is no crushing force brought to bear on the tubing. Since this bulkhead joint tube is an eighth inch thick, both walls of the tube add up to 1/4" worth of thread bearing surface. According to ARP (American Racing Products) product info which you can easily find online, increasing the thread contact area more than the diameter of the bolt has very little effect on the strength of the joint, so the method used by Foretravel is a theoretically sound one given the number of fasteners involved (17) in our coach) in the joint. Also, the Roloks are very high strength fasteners (140,000PSI if memory serves me).

Barry's post in this thread: My bulkhead experience, indicates that the hole in the angle iron should be of a slightly larger bore so that the rolok bolt passes freely through the angle iron allowing the rolok to clamp the two members together. Step 4 (d).

Page 4 of the "Rolok, Thread Rolling Engineering Standards" document: http://www.semblex.com/files/Rolok-Semblex.pdf, specifies an optimum "nut material" thickness for the 5/16-18 Rolok of 5/16ths of an inch - this would be the optimal wall thickness of the square tubing which the angle iron is being clamped to. 5/16th inch thick material is required to achieve 4 full threads of engagement, or approximately the diameter of the bolt. To me this raises some questions over how the fastener was used in this application.

David Brady, NC

Re: bulkhead blues

Reply #16 – July 03, 2012, 12:04:14 am

In Barrie's comments he mentions (as has been done many times before) that overflow from the water tank migrates into this joint area and promotes (along with other things) rusting and weakening of this assembly. This too me is an issue that can easily be prevented by not filling the tank to overflow. I have never allowed the tank to be more than 3/4 full and unless you have a faulty sensor find this a simple thing to do, and it keeps weight down and mpg up. I do not see a reason to have it that full as water is available in many places if needed.
I agree that moving the location of overflow line away from the Bulkhead is a must, but after looking at mine I decided the easiest way to protect that area was to just put a simple deflector at the exit so no water actually flows onto it and also seal the joint with bitumin which I did when I first learnt of this possible problem. I gather I am lucky that I have not seen any hint of a rust jacking problem, even though we have gone thru' some really wet and snowy conditions on our trips south.
John H

Re: bulkhead blues

Reply #17 – July 03, 2012, 12:04:44 am

Curious, did they do sister bolts or replace the existing Roloks?

Quote from: Peter & Beth – July 02, 2012, 03:36:12 pm

As I do not have the tools, skill nor the competency to perform this job I had Xtreme re-do the front & rear bulkheads in my 97 U270 this past June. You having a 98 coach should also have this type of inspection & repair done by professionals like Brett W. , or MOT, FOT or Xtreme. BTW Xtreme will do either Grade 8 or SS through bolts/nuts/washers.
Peter

Re: bulkhead blues

Reply #18 – July 03, 2012, 12:59:51 am

Barry,
You can see in the picture I posted where the second 1.5" square tubing was before I cut it out. This material was only 16 gage, or about 1/16" thick. It is not sturctural in nature, but is there where to make the utility compartment framing fit different floor plans (my conjecture). This 16 gage material was very rusty because of fresh water leaks, perhaps caused by something as simple as a $0.25 hose washer... I cut it out and welded in 11 gage tubing in its place and extended it all the way accross, as well as adding diagonal braces. The rusted out area was where plywood was inserted between the frame members, probably to provide support for hose reels and such. This plywood was completely decimated and turned into soup which in turn held moisture against the metal causing it to fail.

Regarding the vertical supports you mention for the engine side of the bulkhead... when I am done with the re-skinning and I close the gap for the last time, I am welding some 3"X5"X3/16" rectangular tubing to the vertical angle iron bulkhead supports which go on either side of the two horizontal suspension/powertrain back bones with added 1/4" gussets between same. This will support the push/pull of the drive train and suspension so that the bulkhead is not the (nearly) sole support for the rear axle location. Attached is a mockup made out of the two supports and some triangular gussets. There will be two of these just inside of where the shackles meet the suspension. I believe this will offer adequate backing for the bulkhead joint, at least more than what it came with...

Edit for added content:
Regarding the Stainless Steel fastener option; if you are talking about the typical 18-8 stainless, then you are correct. They are roughly equavalent to grade 2 bolts. But there are options that are much stronger. The ones I chose from ARP ARP 623-4000 - ARP Stainless Steel Bolts - Overview - SummitRacing.com are stronger than grade 8 bolts and will not rust.
Don

Quote from: Barry & Cindy – July 02, 2012, 11:14:52 pm

There is a 1-1/2" square tube running side to side inside the rear of the bay floor. But what is not being mentioned is that there is a second (or third) 1-1/2" square tube against part of the length of the main side-to-side square tube.

Using a 3-1/2" or longer bolt to fasten the rear angle iron to both of the square tubes offers a secure repair.

Cutting backing plates from 1-1/2" steel flat metal will force the bolt & nut to put compression on the edges of the square tubing which helps reduce crushing the tube.

RoIocks with our bay floor design are KNOWN to fail over time. Using any other blind fastener will not work either. The problem is the tube in the floor is too weak to start with, and further weakens from rust as coach gets older.

In some situations, the rear tube is also know to break loose from the rest of the inner floor structure, so even bolts & nuts will not work when that happens.

New Foretravels have a better design in their inner floor structure and use blind fastener HuckBolts. I heard that Foretravel is now repairing older coach's bulkhead problems with HuckBolts, which I think is not a good choice because all blind fasteners can pull out of rusted, weakened inner-floor tubing. Foretravel has also used new Rolock bolts to repair bulkheads. I think some solutions are designed to pacify owners, speed up repair time and satisfy attorneys, rather than be the best in the long run. For a while we heard that bulkhead problems were caused by owners.

I have seen repairs that cut through the bottom of the floor to the rear of the rearmost 1-1/2" square tube and use 2" bolts & nuts to hold things together. This method cuts through a second square tube and removes the support the second tube offers.

Also some use stainless steel bolts, which will not rust, but are not as strong as grade 8 bolts. Stainless may be better though, as a rusted grade-8 will weaken over time.

There are many different solutions to bulkhead problems and many opinions offered by coach owners. And professional's solutions seems to change from time to time.

It does not help that fresh water tank overflows onto bulkhead, insuring it gets wet. Bulkhead repairs should also include strengthening the vertical steel braces, like was included in later designs.

Re: bulkhead blues

Reply #19 – July 03, 2012, 10:37:09 am

Quote from: Benjie Zeller – July 03, 2012, 12:04:44 am

Curious, did they do sister bolts or replace the existing Roloks?

Sister bolts (using SS components)...but there's more to it than that. I had a complete rear bulkhead repair which included holding up the entire rear structure with bottle jacks so the remaining roloks could be cut off. This enables the acid wash (Ospho) and sealing of the remaining structure. Then the SS thru bolts are inserted in place after the structure is compressed together with clamps to ensure a tight seal and not crush the tubing by just torquing the bolt/washer/nut combination at each position. Not too technical, but that's the best I could do. A call to James Stallings will clear up any other questions you may have. He is very accessible by phone.

Peter

(edit) A long piece of fiberglass is used to seal up the underside of the floor structure to seal all the holes made to complete the process. I loved the result and how it looks.

Re: bulkhead blues

Reply #20 – July 03, 2012, 11:18:16 am

A couple of observations:

1. I am not a fan of mixing metals, as galvanic corrosion is one of the causes of bulkhead issues. Said another way I would not favor stainless steel mixed with mild steel beams. And, yes I use a LOT of stainless steel on the boat.

2. There are several causes of bolt failure/bulkhead failure:
a. Leaks in the wet bay-- could be from something as simple as bad gasket in the fresh water fill fitting.
b. Rust jacking from salt up north or parking long-term on the beach and not washing it off.
c. Water that gets in around the head of the Rolok bolts. This one affects ALL OF US. Remember, the 1/4" front of front bulkhead and rear of rear bulkhead is OVERDRILLED so that the Rolok will thread into the 1 1/2" box beam inboard of it. Water can enter the bulkhead area around the threads. When I re-did mine (just replacing a few broken bolts), I wire brushed the 1/4" angle, completely cleaned inboard to just a 1/2" or so onto the fiberglass center panel, masked off just the head of each bolt so it could be checked with a torque wrench later and then used 1/2 a can of undercoating to seal the area between 1/4" angle and the Rolok bolts. Bulkheads have remained perfect.

Again, if caught early, the fixes are simple and inexpensive.

Brett

Re: bulkhead blues

Reply #21 – July 03, 2012, 11:34:17 am

My bulkhead was also done by Rance at Xtreme as per the specifications of James Stallings.

One would do himself a favor by talking with James about the pros and cons of the several offered repairs. Once you hear his learned thoughts, you will join Peter and I in knowing his repair is the preferred choice.

Re: bulkhead blues

Reply #22 – July 03, 2012, 11:59:24 am

Brett,
I had my concerns about the possibility of galvanic corrosion, but my research indicates that for this application, it won't be a problem. As well as the fact that Stainless fasteners are used in steel (and in aluminum as well) in automotive applications quite frequently. Now, I have wondered to no end whether or not the use of the thin aluminum trim piece that is inserted in the bulkhead joint at the factory that wraps around the edge of the fiberglass sheet may have contributed to the deterioration of the bulkhead joint, but that is history now! Following is an excerpt to the guide "Stainless Steel Fasteners Designer Handbook" found at this link http://www.ssina.com/download_a_file/fasteners.pdf.
Excerpt:
"It is also important to have an understanding of the relative areas of the two different materials that are in direct contact with one another (the fastener system will normally represent the smallest surface area for materials being joined). Consequently, the fastener system should be cathodic to the materials being joined. This can be seen in the photographs showing the bolting materials used in the construction of the Thames River Barrier on page 14. In the aircraft industry, designers depend on this area-relationship principle when they specify stainless steel fasteners in aluminum structures. The greater the relative area of the anodic (aluminum material), the less severe is the corrosion. By comparison, steel or copper alloy studs for joining stainless steel would accelerate corrosion of the fastener system, although the extent of the galvanic attack would depend upon the relative area of each material.
The area relationship depends not only on the relative area of the materials in the structure, but also on the number of fasteners. Sometimes an acceptable balance of incompatible metals may be achieved by adjusting the number of fasteners to distribute them more uniformly to avoid a local condition of low relative area.
A general rule to remember is to use the more-noble metal for the part with the smaller surface area. This makes a good case for using stainless steel fasteners for joining metals that are less corrosion resistant... "
Of course, this all just my opinion based on what I have read and some experience working on various mechanical things over the years... but what do I know, I am just a musician! In the end, I have to do what I feel will work best to let me rest easy that all the work I have done will have a good result, and on that account, I am satisfied that my Foretravel basment will last as long as the rest of the coach and then some.
Don

Quote from: wolfe10 – July 03, 2012, 11:18:16 am

A couple of observations:

1. I am not a fan of mixing metals, as galvanic corrosion is one of the causes of bulkhead issues. Said another way I would not favor stainless steel mixed with mild steel beams. And, yes I use a LOT of stainless steel on the boat.

2. There are several causes of bolt failure/bulkhead failure:
a. Leaks in the wet bay-- could be from something as simple as bad gasket in the fresh water fill fitting.
b. Rust jacking from salt up north or parking long-term on the beach and not washing it off.
c. Water that gets in around the head of the Rolok bolts. This one affects ALL OF US. Remember, the 1/4" front of front bulkhead and rear of rear bulkhead is OVERDRILLED so that the Rolok will thread into the 1 1/2" box beam inboard of it. Water can enter the bulkhead area around the threads. When I re-did mine (just replacing a few broken bolts), I wire brushed the 1/4" angle, completely cleaned inboard to just a 1/2" or so onto the fiberglass center panel, masked off just the head of each bolt so it could be checked with a torque wrench later and then used 1/2 a can of undercoating to seal the area between 1/4" angle and the Rolok bolts. Bulkheads have remained perfect.

Again, if caught early, the fixes are simple and inexpensive.

Brett

Re: bulkhead blues

Reply #23 – July 03, 2012, 12:27:30 pm

If you want to do some reading on galvanic corrosion, then start here:
Corrosion, stainless steel
Peter.

Re: bulkhead blues

Reply #24 – July 03, 2012, 01:51:21 pm

Don,

Good point about having the fastener be the cathode and larger area being the anode, IF you have to have dissimilar metals. I guess my take is that I don't see an advantage to introducing a dissimilar metal as grade 8 steel bolts work very well.

Agree that we are likely splitting hairs on this-- either will make a great end-product.

I do feel strongly that one needs to spread the load on the box beam as I did with the mild steel rectangular "washers" I had made. With many kinds of fasteners it would be easy to crush the box beam before achieving adequate torque if the load were not spread to the top and bottom of the box by the rectangular washer. Can't see how a huck bolt would work, as it has no ability to spread the load sufficiently to load the top and bottom of the box vs just crushing the middle. If anyone has measured the spread of the huck bolt, would be interested to see exactly how far it does spread the load.

Clearly the extent of the repair depends on severity of the problem. Mine had a couple of broken bolts, zero rust, zero separation (Our coach has been in Texas all it's life and most of its time stored indoors when not in use). VERY different from some I have seen with long-time water leaks into the wet bay or coaches from up north where salt corrosion and rust jacking are issues.

Brett

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