Bulkhead Joints through the years...

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Bulkhead Joints through the years...

December 24, 2012, 03:06:40 pm

I know there are some on the forum who are justifiably sick of hearing about bulkhead joints... this thread however, it's not a plea for help, a complaint, or a wow-as-me sort of thing. It is just informational, and really I would hope just a discussion about the various methods which for travel has used to join the monocoque section of the coach framing to the traditionally framed chassis portions of the coach. In spite of a few often discussed weak points, which are honestly mostly owner preventable maintenance issues, I am quite sold on the Foretravel design. For the most part, I am blown away by the design choices which Foretravel company made. From the suspension design to the powertrain components and brake system... All top-notch. And that does not even discuss the often acknowledged quality of the cabinetry and the interior bits.
So that said, this thread is about the design of the bulkhead joint in different model years... Raymond and Michael who were staying in 1000 trails park nearby, we're very gracious in showing Tyson and their beautiful 2009 Nimbus coach. Man, I will tell you this is one beautiful machine! While there, I took a picture of the rear bulkhead joint area... And was very interested to note some significant design changes from our 99' U270. I also had downloaded a picture from somebody's classified add of a 2003 U270. And of course, I have many pictures of the bulkhead area on our coach

So here are three pictures of three slightly different approaches to the bulkhead joint area. Of course, there may well be significant additional internal and therefore invisible changes in the basement substructure as well. I thought it would be interesting if anybody from earlier generations of Unicoaches or Unihomes would post their pictures as well. I would also appreciate any commentary from the engineering types on the forum about the differences in this structure. One thing that can be seen is, that Foretravel was not completely stagnant on the design aspect of this part of their coaches.

Re: Bulkhead Joints through the years...

Reply #1 – December 24, 2012, 03:17:31 pm

Hey Don how can we get bored on something so important to us with this design. You have over the period given us all a new perspective of the repair and maintenance of this area, as has Brett W
John H

Re: Bulkhead Joints through the years...

Reply #2 – December 24, 2012, 10:06:42 pm

I just had my rear bulkhead repaired by Wayne @FOT a couple of weeks ago. I thought you guys might want to see the official FOT repair.

Instead of through bolting they used huck bolts. I'd never heard of them before but Wayne said they come out of the aircraft industry and are what they use to attach the bulkheads on the new coaches. It's basically a large rivet. They use a special air tool to secure the huck bolts. You can see a portion of the tool behind Wayne in the images below.

I talked with Wayne a little before the repair. Told him that I had relocated the freshwater overflow to spill out the bottom of the coach. He said I didn't need to do that. The overflow doesn't cause a problem. It's the dirt that accumulates on top of the angle iron that traps the water that causes problems. He took me over to the drivers side of the coach and showed me the dirt on top of the angle iron there. (see picture below) He also said the freshwater overflow actually helped since it keep the area clean(er) and that he sees more problems on the drivers side as a result. He did advise keeping the top of the angle iron clean.

As part of the repair he removed all of the rolocks, opened the area between the angle iron and the frame , cleaned it out, sealed it, reattached the angle iron, drilled out new holes for the huck bolts, installed the huck bolts and sealed the whole thing. Says I should never have a problem with it again. My coach is 20 years old if I get another 20 out of it I'll be happy!

Wayne also said not to try to seal up the hole the old rolock came out of. He said it would trap water and cause more damage.

I'm not sure how much the repair cost as I had some other frame repairs done. The entire section under the wet bay had to be replaced. The bill was a little over 2K for a total of about 2.5 days work.

It was wet out when I drove back from the shop so the bulkhead is wet in most of these pictures.

Enjoy the pics and have a Merry Christmas and Happy Holidays!

see ya
ken

Re: Bulkhead Joints through the years...

Reply #3 – December 24, 2012, 11:54:10 pm

Ken,

I am really reluctant to jump onto this one, but there are two things I really disagree with.

First, water in the wet bay is a PRIME cause of bulkhead failure-- have seen it from stupid little things like the $.10 gasket on the fresh water inlet, same gasket on a tank flush, leak from the water pump and most recently, a bad water heater drain plug. Water in the wet bay really has no way to escape other than down into the grid/bulkhead area. I have done too many inspections that have revealed this as a common (and easily preventable) cause of bulkhead issues.

Second, while I am very familiar with huck bolts (long used in airplane construction, HD equipment construction, RR construction, used on Alpine coaches frame construction, etc, I don't see them as ideal for repairing a failed bulkhead. Remember, we are dealing with THIN WALL (1/8") box beams. Rather than spreading out the load on the top and bottom (i.e. horizontal portion of the box beam) that happens when you thru-bolt with large rectangular washer, a huck bolt focuses all its load on the center small area of a (likely) compromised thin wall.

I know that is the factory fix, and very much like the rest of the details of the factory fix, but do question these two parts. And, if the top of anyone's angle is not sealed, invest $5 in a can of automotive undercoating and an hour with a wire brush and seal that area as well as the heads of the Rolocks (as discussed in my write-up back in November 2009): Bulkhead Repair-- A Comprehensive Look

I have seen 20 year old coaches with zero bulkhead issues and 10 year old coaches with major issues. Just paying a little attention to some easy details really helps.

Brett

Re: Bulkhead Joints through the years...

Reply #4 – December 25, 2012, 09:22:42 am

Quote from: kenhat – December 24, 2012, 10:06:42 pm

Wayne also said not to try to seal up the hole the old rolock came out of. He said it would trap water and cause more damage.
ken

My two cents.

Correct me if I'm wrong but I think if water gets into the tube via those holes, there is no way for it to escape thereby rusting the tube from the inside out. The aircraft industry uses "tube seal" to squirt into the tubes of tube and fabric aircraft. (addt'l reading see below) I think this would be an excellent addition to the repair. Squirt some in all the holes and close the holes up with some pieces of eternabond tape, etc. See below.

TUBE SEAL LINE OIL from Aircraft Spruce

"Prevents rust and corrosion inside aircraft tubing structures. Tubeseal is a blend containing a very fine preservative oil (MIL-L-21260) which has a characteristic of climbing the tube wall and spreading over the entire surface to provide lasting protection. Penetrates and reveals very small pin holes in a weld and in time, due to exposure, congeal and seal the hole. 1 quart will treat 2 light aircraft fuselages. Complete instructions on label."

Poly-Fiber Aircraft Coatings - Tubeseal Internal Tubing Corrosion Inhibitor

"TUBESEAL INTERNAL TUBING CORROSION INHIBITOR

USE:

Tubeseal is a blend containing a very fine preservative oil (REF: MIL. SPEC. L-21260), which has a characteristic of climbing the tube wall and spreading over the entire surface to provide lasting protection. Prevents rust and corrosion inside aircraft tubing structures.

Tubeseal will penetrate and reveal very small pin holes in a weld and, in time, due to exposure, congeal and seal the hole.

One quart is sufficient to treat a 1- to 4-place aircraft fuselage and miscellaneous tubular components.

INSTRUCTIONS:

1. Drill a No. 30 (.128) hole on top side of tube approximately 1.5" from an end. Holes are usually drilled before welding is completed for venting purposes.

2. Insert into each tube section the following quantity of inhibitor:

5/8" dia. or less - 1.0 cc per ft
1.0" dia. or less - 1.5 cc per ft
1.5" dia. or less - 2.0 cc per ft
2.0" dia. or less - 3.0 cc per ft

3. Close all holes with pop rivets No. AD-41H (closed end type).

4. In order to insure complete internal wall coverage, rotate fuselage or other welded tube assembly to assure all tubes are cycled from upright thru 90° to side, then 90° to inverted, then 90° to opposite side and finally 90° back to upright. A minimum of 5 minutes waiting period should punctuate each 90° arc. Room temperature during application should not be lower than 60°F.

Process approved by FAA during certification of Stits Skycoupe Model 9A. TC No. 4A-31.

SHELF LIFE:

Infinite, in sealed containers in protected storage Not affected by freezing.

PACKAGING:

One-pint and one-quart cans. "

Good luck,
Merry Christmas and happy new year to all,
Rick

Re: Bulkhead Joints through the years...

Reply #5 – December 25, 2012, 11:32:13 am

Water intrusion behind the angle iron both from above and below along with lack of corrosion protection on the angle iron and Roloks is the #1 reason for the failures. Roloks were not the best choice to begin with other corrosion resistant fasteners available. But no bolt can resist rust jacking. Bulkhead area close to the tire spray, front and back is the most likely to be in the worst shape.

I am 100% in agreement with the factory removing ALL the Roloks, removing ALL the rust, applying a corrosion inhibitor to the angle iron as a complete, long lasting fix. Installation of washers/bolts on the far side of the square tubing is a good way to check tube/foam condition when you go up through the foam.

Checking with a torque wrench is also a iffy proposition with placebo results possible.

It takes a bit of work with a Sawsall but an incredible amount of rust can be trapped behind as the angle iron is eaten away. Bolt replacement without a total cleanup is a band aid fix.

Boiled linseed oil is the same as the Tube seal packaged products sold by Stitts and Aircraft Spruce. You can get it at a paint store, Home Depot, etc. Works better than any synthetic (ask Folker Aircraft). Remove one Rolok and inject a few ounces into the tube. Rick says it well.

Pierce

Re: Bulkhead Joints through the years...

Reply #6 – December 25, 2012, 12:49:02 pm

Quote from: Pierce & Gaylie Stewart – December 25, 2012, 11:32:13 am

Checking with a torque wrench is also a iffy proposition with placebo results possible.

Boiled linseed oil is the same as the Tube seal packaged products sold by Stitts and Aircraft Spruce. You can get it at a paint store, Home Depot, etc. Works better than any synthetic (ask Folker Aircraft). Remove one Rolok and inject a few ounces into the tube. Rick says it well.

Pierce

Pierce,

Would respectfully disagree with your first statement. If sufficient rust jacking has occurred that there is separation of the bulkhead, there WILL be broken Rolock bolts. Same if there is extensive rust in the 1 1/2" square tube into which the Rolock is torqued-- if the walls of the beam are substantially compromised, the Rolock will not hold torque. If it holds torque, I agree it is not a guarantee that there is no problem, but if there is no separation and all bolts hold torque, I am comfortable with that.

Totally agree on using some corrosion protection, but you MUST make sure that there is no water/moisture in the beams before using them.

Brett

Re: Bulkhead Joints through the years...

Reply #7 – December 25, 2012, 12:57:23 pm

I will have to do my bulkhead soon but I am not clear on something.
IF I removed all the bolts from the angle Iron what holds the assembly together then ? Is there a risk that the parts will separate and then really be hard to get back together ?
Gary B

Re: Bulkhead Joints through the years...

Reply #8 – December 25, 2012, 01:32:51 pm

Gary,

I was worried about that and did read Don's post about what happens when the bulkhead bolts are removed.

My solution was to remove from 1/4 to 1/3 of a row, separate the angle iron from the tin and rectangular tubing by wedging a flat chisel between and forcing the angle iron apart until I had about a half to three quarters of an inch separation. This was plenty to allow the sawsall to do it's job followed by my sandblaster (optional). This also allows your favorite coating to be applied. Just repeat the procedure on the next few bolts until you get to the other side. If any break off, you will need to drill next to the broken bolt and then run a new fastener through, either tapping or going all the way through and adding a washer and nut. Fasteners are optional with original Roloks, galvanized all thread, grade 8 or stainless. I chose 316 stainless.

Pierce

Re: Bulkhead Joints through the years...

Reply #9 – December 25, 2012, 02:31:57 pm

@Gary Wayne said "they open the joint, clean it out and seal everything up". I didn't see the procedure so cannot comment on how they did it. They did install a fresh piece of metal between the angle iron and the box frame. I'm sure it's sealed to the box beam to keep water out. You can see it in the picture that shows the removed rolock hole in the angle iron.

Since this is a factory fix they will stand behind it. I will of course inspect it regularly and also have FOT check it every few years. I will post if I notice any degradation. Of course that goes out the window if FOT goes under.

I made a substantial contribution to help with FOTs survival while at the factory.

You're welcome!

see ya
ken

Re: Bulkhead Joints through the years...

Reply #10 – December 25, 2012, 04:00:34 pm

Quote from: kenhat – December 25, 2012, 02:31:57 pm

@Gary Wayne said "they open the joint, clean it out and seal everything up". I didn't see the procedure so cannot comment on how they did it. They did install a fresh piece of metal between the angle iron and the box frame. I'm sure it's sealed to the box beam to keep water out. You can see it in the picture that shows the removed rolock hole in the angle iron.

Since this is a factory fix they will stand behind it. I will of course inspect it regularly and also have FOT check it every few years. I will post if I notice any degradation. Of course that goes out the window if FOT goes under. I made a substantial contribution to help with FOTs survival while at the factory. You're welcome!

see ya
ken

Ken,
Us DYI'ers are just trying to formulate our own plan for this patch/repair so we appreciate your posting the details of your repair.
Rick

Quote from: kenhat – December 25, 2012, 02:31:57 pm

I made a substantial contribution to help with FOTs survival while at the factory. You're welcome!

This gets you a KARMA point from me. Merry Christmas!!

Rick

Re: Bulkhead Joints through the years...

Reply #11 – December 25, 2012, 04:58:03 pm

I have a question here. On my 02 there are 4 bolts, one on each end and two in the middle and under these bolts end on the bottom there is a cap about the size of a silver dollar. I figured so a nut could be reached. Rolox bolts are spaced through out also. Both front and back are the same way. So i figured it had been repaired at one time. Living in Nac., I decided to go over to MOT and look at others. All 02s and 03s, which were 4, were the same as mine. The 98s and 99s were not. So my question is did FT do this as a factory fix? Chappell

Re: Bulkhead Joints through the years...

Reply #12 – December 25, 2012, 07:18:17 pm

Quote from: wolfe10 – December 25, 2012, 12:49:02 pm

Pierce,

Would respectfully disagree with your first statement. If sufficient rust jacking has occurred that there is separation of the bulkhead, there WILL be broken Rolock bolts. Same if there is extensive rust in the 1 1/2" square tube into which the Rolock is torqued-- if the walls of the beam are substantially compromised, the Rolock will not hold torque. If it holds torque, I agree it is not a guarantee that there is no problem, but if there is no separation and all bolts hold torque, I am comfortable with that.

Totally agree on using some corrosion protection, but you MUST make sure that there is no water/moisture in the beams before using them.

Brett

OK, if there is any separation visible from underneath, the fastener has failed and the head may or may not still be in place. The closest fastener head to the failed bolt may be intact but will probably be frozen in place. I do use the torque wrench on remaining bolts but start by turning in the counterclockwise direction. If they turn OK, I reset the torque wrench in the clockwise direction and torque to specs. This does not mean that they are up to the required torque for the strength of that fastener. Age and water/chemicals/rust will have caused a certain degree of embrittlement with accompanying loss of strength in the non-protected factory fastener.

If they don't release in the counterclockwise direction, I keep going until they break off. Just because the torque wrench clicks in the clockwise (tightening) direction does not mean that they are up to strength. They may be frozen in place and WILL have lost some original strength from not only embrittlement but also from the increased load they are under from rust jacking as well as having to take more load if the adjoining fastener has failed. I had several bolts break off when trying to remove them in a location with no indication of rust/separation. That's why I only give the torque test a partial success rating.

If you do break any off, you should be ready to drill and install replacements at least on a temporary basis until a more complete repair can be done.

By removing two adjacent Roloks, you can put a bright light source like a CREE flashlight up to one hole and eyeball the other to check for interior rust. When I drilled my replacement holes, I stuck a tiny camera with a led light in and with it connected to my laptop, was able to see the interior condition. Nice to do but the light/eyeball does the trick also. When the Roloks break off, they usually break between the fastener head and the rectangular tubing so water generally does not get inside. Will all my failures, both front and back were dry and rust free inside.

Bottom line is that even if all bolts pass any test, the total strength will not be up to the level when your rig left the factory and any failures combined with rust jacking will further weaken the remaining bond at the attachment point. All this is without considering any other damage from tank filler leakage into the foam/steel below.

As far as water leakage into the wet bay goes, most of my Rolok failures were on the forward bulkhead (passenger's side) where there is no possibility of water from the wet bay. The fuel/propane tanks sit close but no source of coach water, just spray off the tires.

As far as why it may strike some coaches more than others even when from the same environment, I found that differing steel suppliers supplied steel with different coatings and characteristics. At the time (1980's) most of my steel except for DOM or seamless tubing came from Korea.

Pierce

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Bulkhead Joints through the years...

December 24, 2012, 03:06:40 pm

Re: Bulkhead Joints through the years...

Reply #1 – December 24, 2012, 03:17:31 pm

Re: Bulkhead Joints through the years...

Reply #2 – December 24, 2012, 10:06:42 pm

Re: Bulkhead Joints through the years...

Reply #3 – December 24, 2012, 11:54:10 pm

Re: Bulkhead Joints through the years...

Reply #4 – December 25, 2012, 09:22:42 am

Re: Bulkhead Joints through the years...

Reply #5 – December 25, 2012, 11:32:13 am

Re: Bulkhead Joints through the years...

Reply #6 – December 25, 2012, 12:49:02 pm

Re: Bulkhead Joints through the years...

Reply #7 – December 25, 2012, 12:57:23 pm

Re: Bulkhead Joints through the years...

Reply #8 – December 25, 2012, 01:32:51 pm

Re: Bulkhead Joints through the years...

Reply #9 – December 25, 2012, 02:31:57 pm

Re: Bulkhead Joints through the years...

Reply #10 – December 25, 2012, 04:00:34 pm

Re: Bulkhead Joints through the years...

Reply #11 – December 25, 2012, 04:58:03 pm

Re: Bulkhead Joints through the years...

Reply #12 – December 25, 2012, 07:18:17 pm

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