Bulkhead: Separation

Problematic coach years used roll-lock bolts which are just self-tapping bolts that thread in from outside. They hold rear and front side-to-side bottom frame steel to steel frame inside the bottom compartment floor. Over time, the inner steel may rust or otherwise lose strength and the self-taping bolt is just not a strong positive connection.

Coaches with 400-450 HP engines produce lots more torque than 300-325 HP engines and may put more stress on the bulkhead bolts. Towing heavier trailers or cars may tend to pull bulkhead apart.

Keeping water out by preventing water tank leaks, etc may help to keep inner steel from rusting. Sealing the exposed bulkhead with spray undercoat material may help keep water from getting up into bulkhead.

Later year coach manufacturing used better fastening techniques and separation is no longer a potential problem. This problem is probably unique to Foretravel’s construction design, which allows for more space with less vehicle weight.

A fix that has been used, although a lot of work because several new holes are drilled into the outer frame continuing through the inner floor frame. High-strength bolts 7/16″ by 2/1/2″ grade 8 bolts are inserted into the new holes from the outside. Access to the end of the bolt so a Lock washer and nut can be attached, is accomplished by using a 1 3/4″ hole-saw to drill up through the thin fiberglass of the bottom of the bay floor.

The large bay floor is a one-piece structure that has metal framing and metal cross pieces at points where bay vertical walls exist.  Additional metal is used to support tanks contained in bays. The space between the metal frame pieces is filled with solid Styrofoam and thin one-piece fiberglass panels are sealed to the bottom and top of the floor.

Round plastic caps may be used to close off the hole drilled for access to the end of the bolt. Or a thin piece of fiberglass may be sealed to bottom to cover lots of holes. Original roll-lock bolts do not come out so there is just so much space between bolts for new holes. And if too many holes are drilled the cross member strength is weakened.  

Also, the inner floor frame may have extra steel strategically located that is not visible, so one may not know how long a bolt to use or where to drill for access to the end of the bolt. One solution for a coach with most of the roll-locks broken may be to cut off several inches of the thin bottom fiberglass floor covering fully from side to side so they could see the back of the steel cross member from under the coach. Then after tightening all the nuts & bolts, a wider fiberglass sheet could be sealed over the side-to-side opening.

The roll-lock bolts in many coaches are holding up just fine.  Keeping undercoat material may be the only periodic maintenance needed.  Most problems are in the rear, although the front is constructed the same. Don Hay – U-280, 36′ Grandvilla

Towing has nothing to do with bulkhead separation. The bulkhead(s) is forward of the rear-drive wheels. When accelerating with a heavy trailer, the rear-drive wheels are forcing the bulkhead together. When braking with a heavy trailer, the trailer is forcing the bulkhead together. So, what tries to separate the bulkhead, especially the rear one? It is the retarder.

The retarder is slowing the rear wheels but not the front wheels as would the brakes. So the rear bulkhead transfers the slowing effort to the front of the coach. This is the force that tries to open the bulkhead joint. The only way a heavy trailer could apply the same type of force is to slow the coach by using trailer brakes only, no retarder and no coach brakes. I hope this helps you all understand the way forces are applied to the bulkhead and what might be the source of those forces. Rudy Legett 1995 U320

I have been investigating the “do-it-yourself” approaches to repairing the separation of the bulkheads (actually, angle iron and a 1 ¼ 1 1/4 inch square tube).

I learned that FOT Parts sells a “kit” to fix the bulkhead separation, so this afternoon, I went over to Parts and found out the contents of the kit:

  1. There are 8, 3/8”, 2 ½” long, grade 8 bolts with flat and lock washers and nuts.
  2. Also, at least an equal number (I think there were more like 10) of “roll-lock” bolts. These look like lag bolts and are what was installed originally. They are 3” long, 5/16” diameter, black steel. The inside head of the bolt has grooves in it that dig into the angle iron, preventing the head from vibrating/backing out.
  3. 8 plastic plugs for the nuts on the through-hole bolts.
  4. No instructions included, so parts put me through to Mark Harvey, who patiently explained to me:
    a) For the 3/8” bolts, holes must be drilled large enough for the bolts to pass cleanly through both angle iron and square tubing.
    b) Square tubing is not the heavy-duty tubing used for the side frame, but a thinner tubing used for internal support.
    c) It would be possible to crush this tubing if too much pressure were placed on the nuts. Therefore the recommended torque on these heads is 20 ft-lbs, or for a “mechanically inclined” person, ‘firm but not excessive’ was the description.
    d) When drilling the holes for the “roll-lock” bolts through the angle iron, the holes have to be a larger diameter than the 5/16” bolt, so it passes freely through the angle iron.
    e) In between the angle iron and the square tubing is a piece of “sheet steel” (I couldn’t detect any in my coach); I must also drill the larger hole through it.
    f) The hole in the square tubing should be 9/32” or smaller, for the roll-lock bolts to grip into. He said smaller would work to grip better but would be harder to torque into the tubing. No mention of torque limitations for the roll-lock bolts.
  5. Mark said that the 3/8” bolts and nuts are designed to pull the angle iron and square tubing together.
  6. Then, the roll-lock bolts are installed between through-hole bolts to firmly connect the components together. The kit sells for $35. If Wayne is using huck bolts, then I doubt that he is even using this kit. That would indicate that it is intended for us do-it-yourselfers That’s about it. Don Hay – U-280, 36′ Grandvilla

In my discussion with Wayne, before he did my repair, he explained that the most important part of the repair is cleaning the surfaces between the steel pieces at the joint. He said the joint had to be spread 3-4″ apart so all oxidation could be removed and a rust preventative be applied. He said that without this work the rust in the joint would just keep expanding, breaking any fasteners. The spreading process is definitely beyond the capability of most of us (with the risk of sidewall delamination!) Brett Harrison 99 42′ U320

Another point to remember is to remove the drill from the hole saw after the hole is started on the underside so that the water tank is not perforated. I remember James Triana emphasizing this when discussing this on the phone some time back. Felix Mathieu

It usually starts as a single or pair of broken bolts. If replaced, no big deal. But if two in a row are broken it puts more stress on adjacent bolts and it progresses from there. If you go under your coach and (looking at the rear bulkhead for example) look where the white fiberglass floor for the basement ends, there is an angle beam with bolts going straight forward. THOSE are the ones that we are talking about. Very easy to see and put a torque wrench on. If you don’t have a torque wrench, apply only reasonable torque (like you were installing a spark plug in an aluminum head) on the bolts. You will likely find that they either are OK, or the bolt head falls off in your hand with little more than hand torque.

I have yet to “break” a Rolok in checking a bulkhead. The bolts have either been good (torque up) or they were already broken. The way you can tell they have been broken for a while is that the surface where the bolt is broken is rusted. And they usually break 3-4 threads in from the bolt head. THAT is where the Rolok torques into the “near side” of the box beam.

After extensive discussions with Rolok Corp, it was their considered opinion that if the bolt held proper torque, they are doing their job and no further action is needed. And, what I have found is that the will either hold that torque or if not, be already broken. I know there are some who advocate removing them to check, but in the absence of bulkhead separation or another indicator of a problem, if they hold torque, that is where I would quit.

And, the torque values are for DRY. Using an anti-seize or otherwise lubing the threads would change torque.

Let’s look at what you are drilling into to access the inside to the box beam where you will install the washer, lock washer and nut (bolt comes through from the “outside”). There is a very thin layer of fiberglass on the coach bottom. Inside (above) that is foam insulation with a few steel box beams (like the one you will be through bolting the angle to). Above that is another layer of fiberglass that serves as the floor for the basement/wet bay.

So to determine where to drill (let’s use the rear beam in this example), use a magnet or “tap” to define the front of the 1 1/2″ box beam you will be through bolting. The 1 3/4″ hole will be forward enough so that the back of the hole just clears/is forward of the box beam (you don’t want the hole saw to cut into the beam!). And from side to side is lined up with the horizontal hole you will put the bolt through.

Set the hole saw up so the pilot (center bit) touches perhaps 1/8″ to 1/4″ before the teeth of the hole saw. It just needs to protrude enough that it anchors firmly in the bottom fiberglass layer before the hole saw’s teeth hit the fiberglass. Drill through the lower layer of fiberglass and into the foam insulation. DO NOT DRILL TOO DEEP. Much safer to use a razor knife or other tool to remove the foam than to take a chance on drilling up into the basement floor.

And when I get a little time, I will likely just to some preventive maintenance, installing a few on our coach. Unless the beam is badly rusted (from water leak in the wet bay), lots of road salt, etc. or there is significant separation, reinforcement with 5-6 thru-bolts may be all that is needed to make this bomb-proof. Brett Wolfe 1993 U240

Foretravel Bulkhead Repair– A Comprehensive Look

THIS IS A SLIGHTLY REVISED/UPDATED information to above describing a few new tricks/suggestions

This is on a 1993 U240, but it is my understanding that most apply to Unibody and Unicoaches.

I am not sure bulkhead is a descriptive term here. The center part of the coach is built on a strong grid system with 1 1/2″ box beams with 1/8″ walls at the ends (front and rear) where they attach to the 1/4″ angle that is part of the frame holding the drive train (rear) and front end (front).

The Rolok’s go through the ¼” angle and torque into 1 1/2″ box w 1/8″ walls.

After talking with Mark Harvey at Foretravel and an engineer at Rolok, I went under the coach. First, I looked for any separation in the area of attachment. NONE– just some light superficial rust.

Next, I put a torque wrench on each of the Roloks. Check torque to 250 INCH (repeat INCH) pounds. Check torque CW and CCW. If they don’t hold you need to know that. If it loosens, use that hole (drilled to 3/8″) to install a thru-bolt.

What I found was that 5 Rolok bolt “heads with 4 threads” broke IMMEDIATELY—at less than 20 inch-lbs. All the rest did not move at 250. In inspecting the failed Roloks, all had been broken for a long time– light surface rust on the sheared surface. The “4 threads” mean they were broken where they started torquing into the 1 1/2″ beam. Could have been broken at installation or from sheer stress afterward– not sure it matters.

Two fixes: Either remove the broken bolt (soak with penetrating oil, double nut and back out from the INSIDE), drill to 3/8″ and thru-bolt OR drill a new 3/8″ hole and install 3/8″X 3″, Grade 8 bolts and nuts on either side of the “failed” Roloks. Yes, you can use shorter ones, but the 3″ ones made the job a little easier. Because I wanted to be able to torque the thru-bolts to 275 in-lbs without taking any chance of crushing the box beam, I made some 1 3/8″ X 1 3/8″1/8″ plates to install next to the beam (cost me a piece of steel and $10 at a machine shop). So on the rear, from the rear: the 3/8″ bolt, washer, 1/4″ angle, 1 1/2″ bulkhead, 1 3/8X 1 3/8X 1/8″ plate, washer and pinch nut. All hardware grade 8 (except plate). Torque 275 in-lbs.

I used good quality Cobalt bits, progressing up a one-bit size at a time, using plenty of cutting oil and keeping the bit cool. Then, to access the “inside” to install the plate, washer, and nut, I used a 1 3/8″ hole saw to cut through the very thin fiberglass bottom of the coach. The hole was centered on the bolt left to right and the closest edge of the hole was approximately 3/4″ in from the inboard edge of 1 1/2″ beam. This allows access with a screwdriver to easily remove the foam core, exposing the beam and also access for the 9/16″ wrench to tighten the nut. When locating the thru-bolts, use a magnet to locate the other beams in the fiberglass “floor” to the basement. Since you need access to install the plate, washer, and nut, obviously, avoid areas with beams on the floor.

I wanted a water-proof plug– driving through rain could “challenge” plugs not designed to keep water out unless sealant, etc were used.

Clearly, one of the causes of bulkhead separation is a leak in the wet bay.  The water WILL get down to the bulkhead area and can cause rust and in severe cases rust jacking, broken bolts, and bulkhead separation. So, if you are conscientious about not allowing water to leak onto the wet bay floor, definitely seal the bottom with undercoating as the other source of water is from the road.

The other suggestion is that at least on the coaches I have seen, there is nothing keeping water from migrating in past the head and threads of the Roloks– i.e. the 1/4″ beam is drilled larger, so the Rolok threads will torque in the 1 1/2″ beam. That leaves room for water to migrate in along the side of the Rolok where it goes through the 1/4″ beam. I filled the holes where the broken bolts were with Bondo. Then wire brushed the beam and short metal “skirt” just inboard of it. Then put masking tape on the head of the Roloks (where a socket would fit) and use automotive undercoating to seal the area, making sure the Rolok to beam joint is protected.


Periodically new bulkhead participants stroke the alarm bells and create new theories and tangents to the bulkhead issue.

It’s always possible (in the making mountains out of molehills?) to lose sight of what is important to the general Foretravel population!

We could certainly make the well-documented bulkhead issue into something weird enough to COMPLETELY scare away ALL potential future Foretravel buyers and cause ALL current owners to suffer irreparable sleep deprivation.

OR, we could logically, review the body of evidence and reasonably conclude that we have 99% or more of the information that we need to be perfectly comfortable.


1. The bulkhead issue is easy to detect, should logically be a part of any pre-purchase body of wisdom, and that routine inspection (250 in-lb. torque with a qualified tool) must be a part of each UNIHOME/UNICOACH owner’s ongoing periodic maintenance inspection.

2. We have heard from Foretravel, and their guidance is reasonable and perfectly understandable. [Bulkhead Separation] Can we or should we reasonably expect any more?

3. What’s ROOT CAUSE IMPORTANT? We know that:

a. moisture/water aggravates the issue,

b. chlorides in the form of (from most to least severe) liquid deicers, rock salt, and salt air aggravate the issue.

c. That dissimilar metals aggravate the issue (galvanic corrosion)

d. Any coaches ever operated north of I-20 are automatically suspect and bear closer inspection/watching, especially if they were operated there between the months of October and May.

e. If iron oxide (rust swelling) is present in the joint, the loose iron oxide must be removed and the surface area must be neutralized (eg. with phosphoric acid to turn the red iron oxide to black iron oxide (stable). This stops the oxidation prior to preserving and protecting the area prior to undercoating or otherwise preserving the bulkhead joint.

4. Then, thanks to Brett Wolfe’s experience and wisdom above, we know that once a bulkhead fastener failure is detected, there exists a comprehensive, tried and proven set of guidance on how to address the failure. Owners that have done so (or have had FOT, MOT or Xtreme address the bulkheads) have peace of mind and VERY SOUND COACHES.

It isn’t any more daunting than that and the bulkhead design should be a strong Foretravel selling point instead of the negative mystery that seems to be pursued in repeating cyclical fashion.

But reinventing the issue every few months doesn’t create any improvement in the root cause understanding nor the action plan to address the presence of the issue.

As Brett has said, “It wasn’t a fun project, but neither was it mechanically challenging nor expensive.”

I would contend that it was a fun (DIY) project (for me), the repair has been easy to periodically re-inspect and the repair has been perfectly stable since 2009.

Just my perspective and I’m sure that it will not be universal, but I hope that this helps to tone down the severity of the alarm that is being created. Neal (& Brenda) Pillsbury 1998 U270, 36′