Bigfoot F20DL Overhaul

[Chilliwack Murray]

Well, after about 25 years of camping in the 13' Trillium (apart from about 5 years with a 24' Nash we took to Inuvik) we decided we wanted a trailer with a full size bed that can be left set up and a bathroom. We wanted the larger interior but can't take a large trailer to the type of out of the way places we go so a fifth wheel looks like the best of both worlds.

After considerable research we went to look at one that was advertised as good condition however on inspection - with knowledge of what to look for it was apparent it had all the usual issues. We were disappointed but took it as an opportunity and paid accordingly.









That was last fall and the trailer sat until I had time to install a hitch and get it inside to start working on it this spring. As I write this I am well into the project, actually starting to reassembly. I wanted to avoid posting a lot of trial and error and putting incorrect information out there that others might follow. There are a handful of threads here and info on the internet but most everyone goes about repairs to Bigfoots differently and some, I'm not sure were very successful in the end as the trail just goes cold at some point.

I took LOTS of pictures along the way so I will try to post the most useful here to explain what I've done and why.

I chose this particular model so that I 'could' tow it with the Frontier and it is sitting with full tanks on the hitch sitting in the Frontier to see how it handled the weight. It dropped about 1" on the rear and 3/4 on the front if I recall but I ended up not installing the hitch in the Frontier - I had a 1 ton Dodge I was going to sell but decided to keep so I have installed the hitch in there.

[Chilliwack Murray]

So, the trailer has the usual issues - sagging roof, water damage below the windows and behind the fridge and some bowing of the right side wall. Someone had tried to repair by adding dozens and dozens of screws from the cabinets to the walls - I later determined the mostly just go into styrofoam and did nothing.





There is also a soft spot on the floor in front of the bathroom door. The frame is good condition and has been painted over the years. I was especially wary of the frame and spent about 1/2 an hour tapping all over it with a small hammer but it looks like it was just well cared for.

The frame related issue is the spring hanger which has broken away and is just sitting on the frame. The previous owner was unaware of this and has probably been towing it this way for years. I will replace the suspension so this isn't a big concern, and as a mechanic this is the easiest part of the trailer for me to fix. This suspension arrangement is very unusual though, if anyone can share a photo of how this was attached from the factory I would appreciate it as this looks to have been repaired in the past.

[Iowa Dave]

I have toured one of these trailers. In my opinion the best interior design of a 5th wheel fiberglass trailer I’ve seen. It will be a great trailer for you I’m sure as soon as you get the “wear and tear fixed up. Lots of camping left in that trailer. Best of Luck
Iowa Dave

[CharlesinGA]

Since you plan on rebuilding the suspension, I'd either simply put standard spring hangers on the frame, with double eye springs and shackles, or go all out and get a torsion axle for it.

What is in the picture is the eye end of a spring used as an upper attachment for the "shackle". I'm not sure how that "shackle" stays together, but in any case a more modern setup is in order.

You need spring hangers like these.



Charles

[Chilliwack Murray]

I will definitely replace the springs and shackles with common parts, the axle will stay if it's in good shape. If I do need to replace the axle, I will probably still go with springs so I can adjust the ride height and spring capacity if necessary.

The 'tab' portion was definitely welded to the frame but I was curious if that was original or just a repair someone attempted. It's easy to see why it didn't hold - it's near impossible to get a good weld between that heavy piece of spring steel and the comparatively thin frame material. Not too mention, if that is welded solid, there is nothing to compensate for the change in spring length as it compresses, putting massive strain on that weld.



None of that matters since I will add some material to the frame and install modern hardware but I am curious how it was originally built.

[Chilliwack Murray]

As mentioned at the start, I am already far into this so I have a lot of pictures and details to add before this thread is caught up...

I started by taking many, many pictures for future reference. One thing I have learned over the years is that a lot of the little 'I'll remember this' moments I have when working on things disappear into the ether, sometimes even with the pictures.

I started in the corner where the worst damage was, there was still hope at this point it may just be some spot repairs and leaking from the window:



When I pulled the lower cabinets I could see the dozens of screws that had been added to try to keep the wall from bowing out. They probably worked for a time but the water was coming from higher up - the awning as it turned out. The upper cabinets were actually not that tough to take out without damage - the hardest part was starting to lift the inner floor and sides to access the screws in the frame.





The corners and wall to ceiling joints are attached with various width strips of 1/2" plywood cut at the angle of the joint - not actually 45 degrees. These have a multitude of narrow crown 1" staples and some pieces appeared to have wood glue as well.



I had hoped to work on just the back third and put that back together before moving forward but in the end it wasn't practical. I wanted to ensure whatever repairs I made would last and also improve the strength to prevent future issues so I spent quite a while researching and testing different ideas. There are several videos and posts on various sites where people get to this stage then then nothing more. Some people have built a latticework frame, some double up on the styrofoam and some just add some posts for support.
Also missing is much information on glues that work - some have used construction adhesive, gorilla glue and spray adhesive. There are also videos where some really bad advise is given - like don't worry about getting the old pink contact cement off. I've found a couple good methods to do this by the way.

[Chilliwack Murray]

With the paneling and cabinets out, I started to look carefully at how they built this originally and didn't understand the logic of all the 3x6" pieces of wood they used where the cabinets attached. My thinking was a continuous piece would provide a lot more strength but what I found is that with the contact cement it is nearly impossible to get continuous contact and adhesion on longer pieces. I thought they were just doing this for speed of assembly but it is the better solution, at least for some of the pieces.



I still wanted to add ribs to the roof for strength and after much trial and error for the correct arc and method to do this. Also of note, this works on my trailer because it has a rail around the roof that I can screw to the ends of the ribs. This adds reinforcement keeping the ends in place when the center is weighted down. I am less concerned with the ribs being well glued to the fiberglass as they only need to support it from the bottom.



What I settled on was a 3" wide rib every 24", partly because it lined up with the rail mounting points. I tried a lot of adhesives and settled on Durapro AC3471 latex contact cement. I had initially thought this wasn't working but after several attempts and re-reading datasheets I determined the shop was too cold (about 12C when the product requires above 20C) and not allowing enough time to dry. I haven't worked with contact cement much and it seemed wrong to allow it to fully dry before putting the parts together but as it turns out, that's exactly what it needed. The datasheet says 20-45 minutes but with the thick layer needed for the rough fiberglass surface this takes about 60 minutes. This stuff sticks - I have trial pieces of plywood and foam that have been out in the sun and rain for several months and it would be near impossible to get them apart.

Building the ribs was a lot of trial and error too. I started with the thought that more arc is better however all that does is cause the bottom ends to pull away - I don't need to carry the entire roof, it was already doing that with the original construction, I just want some re-enforcement. I started with two strips of 1/2" plywood and tried several methods of bending and assembling these before I got it right. Construction adhesive tended to creep and allow the rib to straighten, even after curing for 12 days and was also too thick, leaving a gap between the boards. These needed to hold their shape and have the same thickness as the 1" foam board.

What worked in the end was a liberal coating of white construction glue, hold the strips together with a couple wood screws right in the middle, using a cargo strap to bend them about 20% more than the final arc then applying C-clamps every 8" or so. Next I put two screws beside each clamp then took the tension out of the strap and loosened the clamps a little and allowed/helped the rib to reach the desired arc. When the arc was correct I tightened the clamps and let the glue fully cure (I also laid it on its side and marked the outline of the middle and ends on the concrete so I could see if it moved any further). Once I had one perfected, I kept it as a guide, I also drew the arc in crayon on the concrete as a guide for the next ribs.

A couple other items of note. To get a consistent arc, not concentrated in one area or another, don't stack two strips as they were cut from the plywood - they should be flipped end for end, I also used good 1 side (sanded) plywood so I put the rough sides together for the wood glue and the sanded sides out for the contact cement. Whn installing the clamps and the screws, start from the centre and work your way outward evenly. I wasted 2//3 of a sheet getting it right. This was an early attempt with way too much arc:



I also tried numerous methods to remove the old contact cement from the fibreglass as this was crucial to for getting a good bond with the new materials. The only practical solution I found was a variable speed angle grinder with a large wire wheel. I used a knotted 4" steel wheel at about 2500RPM. I would not attempt this with a regular grinder, the fibreglass is very thin and higher speed will burn through or damage the paint and outer coatings. This takes some practice butI found it worked very well using almost no force, barely more than contacting the wheel to the fibreglass and you will see it just peel away. Keep moving at all times to avoid bulding any heat and you will also find the direction of the grain in the fibreglass makes a big difference - if it's not working or material removal slows down, turn the grinder in relation to the material and you will find one or two directions that work much better. For stubborn areas I wiped it down with laquer thinner first which softened up the glue making if sticky so the wirewheel would grab it better. Lacquer thinner will take a long time to hurt the fibreglass but will instantly destroy the styrofoam so use caution... It's also flammable so have plenty of ventillation - I kept a large fan blowing between me and where i was working (and had the windows removed) which also helped blow the fibreglass dust away and kept (some of) it out of my eyes and face. This a a process you just can't hurry, it takes the time it takes and its a lot of work but it works well. A word of advise - even with safety glasses, the small amounts of fibreglass that come off collect around your eyes, as soon as I stopped grinding I blew myself off with an air hose then washed my face and eyes thoroughly with water to get all the fibreglass off... At least after the first time I did. You can see where I have cleaned and where I have not.







For the styrofoam board I tried wire brushing, solvents, scrapers to get teh old glue off and figured I would just have to replace it all which isn't cheap until I noticed that where I pulled the old masking tape off there was no glue left. I tried a few different types of tape and found sheathing tape (call Tuck Tape around here) was by far the best. I found if I rubbed it hard enough to get hot (almost uncomfortably so) then peeled it off it left nearly no glue on the styrofoam. I've tried rubbing it with rags, paper towels and a few different gloves but nothing seems to create as much heat which seems to be key. Using this method, much of the original board can be reused.

[Chilliwack Murray]

Another area of concern was the belly band.

On the Trillium (from what I remember) the two halves are attached with fibreglass resin and the band and screws main cover the seam providing strength and possibly weaather protection in case of voids. On this Bigfoot, the two halves are not attached - the upper shell sits over the lower shell and the metal belly band is screwed through the two pieces into a strip of plywood on the inside. I realized they are not bonded when I was trying different methods to attach materials to the roof - when I tried to prop up one area, the previous prop sticks fell out and I realized I was lifting the entire shell on the side I had removed the belly band screws.



In my case this wood was in bad shape. It's hard to see but the wood (nearly black) is mostly rotted away. The screws were rusted inside and out making them impossible to remove with a screwdriver. They either break off or the screwdriver wont grip.







I ended up loosening them with a small chisel then turning them out with a small Vice Grip and/or a small flat screwdriver inside the Robertson head. This is a slow process and nearly impossible not to distort the aluminum belly band. I was careful and was able to flatten it out and re-use it though.



As mentioned, someone had added dozens and dozens of screws over the years to hold things together and in the process made a number of holes through the shell under the belly band only adding to the water issues. As I discovered at the start, it was easy to lift the entire shell with some prop boards underneath, especially with all the upper cabinets removed. I raised it enough to access the joint and filled all the 'extra' holes with marine epoxy putty.





It should be obvious but just in case, this repair should be done in sections - remove enough length that you can lift the upper shell and separate the joint to clean and repair but don't remove the entire belly band at once unless you have some method of lifting the entire upper shell and keeping it from shifting - it would be easy to cause damage it the whole upper shell shifted or dropped. I have a couple cheap cargo bars I've had for 20+ years that are very handy for this as they are easy to adjust but 1x2 or whatever you have works fine too, you just a variety of material handy to shim it to the right height.

Belly band reinstalled around the rear and rear right side with stainless steel screws and new plywood, I also put a strip of butyl tape between the upper and lower sections to keep water from wicking through the joint. I will continue to make my way around the trailer as the walls are removed and the belly band is exposed.

[Chilliwack Murray]

Something I should mention regarding removing the old contact cement from the fibreglass… As I went I realized that spraying the glue with lacquer thinner everywhere makes it come off much faster and therefore leaves the fibreglass mostly untouched. A quick spray from a squeeze bottle then run the wire wheel over and it leaves very little behind. This is especially important when working on the ceiling as the less time spent holding a grinder over your head the better.

Again, keep a fan blowing between you and your your work, it’s flammable but not explosive and evaporates fast so use in a well ventilated space.

[Chilliwack Murray]

As I continued with the structural repairs I found numerous examples of poor workmanship that led to the leaks and issues with this trailer. Not really a surprise but a little disappointing to see in what is often seen as one of the better built RVs. Of course the same was true for the Nash we had when I rebuilt the front... Good by RV standards but that just means a lot of the others really have terrible build quality.

Wood placement and or lack of wooden supports. They had put two pieces of wood in the back wall to attach the ladder but they either got the spacing wrong or mounted the ladder in the wrong place so only one side if the ladder mount hit the wood... or both. The result was that over the years it broke the bond between the fiberglass and the insulation making the back wall bow in this area.



While working my way around the belly band joint I found that the 45 degree section on the left side had little to no overlap. It's not clear whether they didn't get the halves lined up or it was a mould issue but this is the only place I've seen this issue. Not only did the screws miss the other half, they all nearly missed the wood backer so it ended up with a gap where water could enter. Problem resolved with a wider wood strip, much butyl tape and more care in the screw placement.





Speaking of build quality, would it have broken the bank to use stainless screws on the outside of the trailer?

[Chilliwack Murray]

A few more photos of the belly band repair, as I went I found a few tricks.

Some thin strips ripped from a 2x4 work well to shim the halves apart allowing you to clean out the joint and get some butyl tape between the halves. I had a both thin and thick, about 1/8 and 1/4" so I could slip two thin pieces in then a thicker one between with a hammer if necessary without damaging the fiberglass. I'd scrape it out, wipe clean with laquer thinner then put butyl tape into the joint. Usually it was easiet to leave the backing on the tape, press it into place then peel the backing out thought the joint before moving the shims to the next spot.



Another picture of poor workmanship. This trailer had a chronic leak from battery compartment door as you can see from the floor rot. Clearly they cut the hole wrong and slapped the door over it with almost zero overlap to seal on the upper left corner instead of fixing the fiberglass or even squaring the hole and moving the whole frame up half an inch.



The consulation at least is that when its done it will be "better than new" but that's not a very high bar.

[Larry H]

Good work Murray. A lot of work goes into fixing these things right.

[Chilliwack Murray]

Thanks, hoping the info and the pictures will help someone else down the road. It was a lot of work trying to find pictures of how various parts were constructed to understand how to take them apart and repair effectively.

[Chilliwack Murray]

As I progressed it became clear that there was little point in just repairing things, I should really start from scratch since I plan to keep this indefinitely.

My original plan was to cut out and replace 6-8" of the floor perimeter where there was signs of water damage but without a clear picture of what was under it and the spongy area in front of the bathroom where I suspected the main leaks were, I decided to pull it all up. It turned out the spongy floor was mostly due to being unsupported with only minimal water damage in a few spots. For some reason, most likely careless workmanship, the crossmembers between the main frame rails were all welded in at different heights, only one flush with the frame rails. It looks like they had originally shimmed the fiberglass with rubber to support it but most of that has rotted away leaving a gap and just the heads of the screws they fastened it with digging into the fiberglass. The result was the floor flexing, breaking all the glue bonds and a bouncy floor.





Nothing to gain by trying to salvage what was there so I made a new frame, upsized the wood and doubled up on the centre piece. I used 1/2" stiffer birch plywood instead of the 1/2" fir it had but I think if I did it again I would use 5/8 fir. Weight difference and the extra 1/8" is negligible but it would provide a stiffer floor over time I think. To attach the foam to the floor I used the spray foam adhesive since I could easily hold it down while it cured. I also glued the wood to the fibreglass but I didn't glue the plywood to the foam as I wanted to ability to remove a panel if necessary down the road.







Something I saw on another thread or video, using a support under the floor so I could apply pressure and get a good bond on the adhesive. This is particularly important with the expanding foam adhesive since it keeps expanding for several minutes and if you don't ohold pressure on the pieces it will force them apart leaving you with varying thicknesses of wall or floor.

[Chilliwack Murray]

Been a while since I updated but I've had some time to work on the trailer and got ahead of the thread again.

Going back a bit, I added wood - glued with the foam adhesive anywhere cabinets or benches attach to the walls. The original design had these screwed into the 1/4" paneling however these are what keep the walls from bowing outward. As the glue fails or the roof is weighed down with snow or just bouncing down the road these connection points are critical. At some time in the past, dozens and dozens of screws were added to try and hold the walls in but without anything solid they mostly pulled out.





Also, very important to keep the walls straight when attaching the foam board and paneling or you will have a permanently curved wall. I figured that out on the second attempt. On the roof, the plywood ribs I installed worked well to hold the proper curve when the panels were applied, it was a bit tricky to apply them being curved, you need to start at the middle or end and 'roll' it into place since it won't move once it's touched using contact cement. I did use more foam adhesive as I went but the contact cement definitely gives a stronger, stiffer joint when you can use it. (Sorry for the sideways picture, it's correct when I open it on my pc)







In the mid section of the trailer it looks like the roof had buckled at some point, probably from large accumulation of snow. The foam board was cracked right through and large sections of glue were pulled completely away.




With the rear section walls and ceiling brand new I changed my plan on the bedroom. I had planned to just repair the damage but seeing the broken foam on the roof and the rest being rebuilt the project as always got bigger. No point not going all the way at this point.



One other important point I can't stress enough is to take pictures. Lots and lots of pictures. Before you take it apart, while you're taking it apart and while putting it back together. There's a hundred details you won't remember, especially all the little trim pieces, built up sections required for the curve of trailer etc. I also took photos of the location of all the wood added for attachment points as they are all covered and invisible after the paneling goes on:

[Chilliwack Murray]

I've gotten quite a bit ahead of the posts here so I will try to get a few updates done. Referring back to the floor and water damage, the on real water damage was at the edges, mainly behind the fridge and in the front right corner although without support due to the missing rubber shims and poor alignment of the frame crossmembers the whole floor was de-bonded and weakened.



The most water damage was in the front right but mainly limited to what was the battery compartment under the stairs.



Some of this came down the wall from the awning screws but most came in the electrical passthrough which was basically open and forward facing. Most of the places wiring or gas lines passed though this style of bushing there was no sealer and never had been so it was an easy path for water to enter.

[Chilliwack Murray]

A few pictures to show how the front bedroom is constructed. There was a little water entry from the exit / vent but the main delamination appears to have been from the roof buckling at some point. The front and left windows had water damage under them and like all the windows, appear to have slid down in the opening over the years leaving a gap at the top. The front window had a visible space in the center top where water could run in. This was mainly due to the factory using small pieces of paneling as spacers which just pushed into the styrofoam allowing the windows to slip down. I used larger pieces that landed on the fiberglass and the paneling so they wouldn't be resting on the foam.



The front, like the rest of the trailer has a perimeter channel that I assume collects any water that enters as well as adds considerable strength from the box shape. Seems like a good place for a hidden compartment actually.





The front floor was constructed similar to the rest with larger spacing between the 1x1 framing. They did have a 24" section of 1" (2x 1/2" glued) plywood over the pin to distribute the weight but with the amount of movement in the frame it only concentrates the flex to the area under the window where others have reported cracking.



One other odd thing I noticed was a hole burnt through the fiberglass in the shape of a breakaway switch. It looks like they crushed the switch between the shell and the frame when they assembled the trailer and it shorted when the battery was connected. The moved the switch but never bothered to fix the hole it left. (Black mark near the front)

[Chilliwack Murray]

Like the rest of the trailer it's important to have the walls and roof in proper position and correct arc before and while gluing panels on otherwise they will be forever mis-shapen. I continued with the plywood ribs the rest of the way forward though the spacing was adjusted to land on the divider wall and pickup the edge of the vent.



With the interior removed I replaced the remaining wood strip for the belly band and reinstalled with plenty of butyl tape in the joint and under the aluminum band to ensure road. spray can't work it's way into the joint.

Windows also got a liberal amount of butyl tape. One important step with butyl that I think people often miss it not overtighten in one step. One reason butyl works well is that it doesn't harden but continues to flow and fill gaps as they appear. That also means if you try install something quickly you just distort the window or belly band around the screws. Tighten just enough that you don't distort the frame and leave it for a day. Then you'll find you can tighted it more without any damage. I went around 3 or 4 times getting another 1/4 turn the first time and 1/8 the next times. I think you could keep doing this until there is no sealer left so don't get carried away. I let it sit for a couple weeks before I trimmed the excess. On the rear windows I trimmed it right away and found I had to repeat the process a couple times.









All the screws are stainless steel this time and I got a roll of new insert for the belly band. The aluminum I gave a very quick wipe with lacquer thinner (be careful, it's easy to take the paint off) then the old silicone and other sealers scrapes off with a fingernail. Then a wash with laundry detergent before reinstalling.



The next thing I tackled was the frame which I will add to the thread soon.

[Chilliwack Murray]

I'm getting well ahead of the thread so it's time to get some more photos uploaded...

Probably because I've read other warnings about the fifthwheel frame flex damaging the nose I was looking extra close and did see some stress marks right above the pin and found just moving the trailer in and out of the shop flexes this area. No real damage but it will certainly fail in time. Since it will never be easier than now, pulled the shell off the frame and got to work improving it:





Overall it was in good shape except the broken off spring hangers (which will be much easier to fix now). Some previous owner had put a thick coat of paint on the accessible parts of the frame but even the unpainted top is in good shape structurally, just no cosmetically.



Here's an example of what the shell was sitting on. In most places, some or all of the pads were gone with just a screwhead sticking into the fiberglass:



And the reason for the springy floor... There are crossmembers but they are all welded at different heights, this one has 1/2" gap to the body. Once the rubber pads disappear there is no support and the floor flexes breaking apart the layers. I was pretty sure it was rotted but there was almost no water damage where it was spongy.

[Chilliwack Murray]

Seasons changing... I found I was able to remove much of the black paint that was added to the frame with a 10 degree nozzle on the pressure washer. Kind of a cold job now that summer is over.



I've spent most of my life working outside with little equipment both at home and work so I do appreciate what I have to work with now, especially a separate area I can make a mess in apart from the rest of the shop.



I thought a good deal about how to reduce the flex and not add undue weight but everything comes with added weight. I can take solace in the fact that it was only 3500 lbs to start with so even if I add 500 lbs it's still considerably lighter than most modern trailers the same size. This is what I came up with, swuare off the front frame similar to how the newer models were built and move the propane tanks up front and out of the trailer. I really don't know how you are supposed to wrestle those horizontal 20 pounders in and out of that tiny compartment in the back left corner.



Here's the frame reinforced. Added a second upright and staggered the welding to spread the force on the main frame a little more. I don't see any movement there but if there is, I can add a short piece to distribute the force further back even with the shell on.



It's hard to see how far into the frame the spring hangers had worn but it's probably 2/3 through. I need solid metal to weld new hangers on so a piece of angle will reinforce the frame as provide a solid mounting point.





One thing I hadn't noticed until I started sanding and cleaning up the frame was the back bumper was rusted through in many places presumably from the sewer hose sitting inside wet with whatever it may have had.



Every problem has a solution, this one was cut it off and replace it with something better.



The original bumper was folded sheetmetal to save a few pounds. Since I added all that weight up front including the propane tanks, I wanted to shift a little weight to the back anyway. The bumper and a larger freshwater tank should take care of it.



New bumper painted and welded on:



And, a frame for the premade tank holder:



Everything painted with POR and several coats of Tremclad black. Takes time to cure to full strength so you have to take care not to scratch it for the first month or so but after a few months it's rock hard.



I'll try to get another entry or two before the new year.