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Sagging Tanks

RamblinAnne
Explorer
Explorer
So I'll spare you the unfortunate details of WHY I need to take the camper off the truck tomorrow, but I do. Only for a few hours but it has to be done. It's been a few months since I've taken her off the truck. Not since I've completed the reno and filled the tanks and moved in. Needless to say, she's a lot heavier now than she's ever been. I have total confidence in my jacks. That's not the issue. However, when looking at the underbelly of the camper, I see what appears to be sagging tanks. So much so that it seems to have cracked the thick plastic support structure. (I don't know if this piece of thick plastic actually supports anything or if it's just meant to cover the tanks to shield them from the elements and create a flat bottom).

Anyway. I'm super paranoid that I'm going to lift the camper up, drive forward, and the tanks are just going to collapse to the ground, dumping grey (and possibly black) water everywhere. Is this possible?? Is this plastic membrane the only thing keeping my tanks up?? If so, I'm afraid I'm in trouble. How do I go about reinforcing this support structure?
2013 Ford F350 6.7L Powerstroke Diesel DRW Lariat Crew Cab 4x4
2004 Bigfoot 25c10.6e
Full-timer
34 REPLIES 34

bcbigfoot
Explorer
Explorer
My 2005 and several other years of Bigfoots used hdpe, hmwpe is extra cost and not needed. By the looks of your picture Bigfoot must have used a plastic product similar to hdpe (hdpe won't crack like that), I don't remember the name of the plastic in the picture, some hardware stores carry it, sort of a poor man's hdpe, Bigfoot must have used it for some time, it's half the price and with age will get brittle and crack like the product in your picture.

The product that you linked to is what my Bigfoot came with from factory 1/8 thick, In Canada most Lowes or Home depots would carry it for approx. 40$ for 4x8 sheet. In US not sure?
2002 Dodge 3500 2wd dually, cummins, 4.10 gears, 10500gvwr, Rancho 9000's shocks
2005 Bigfoot 259.6E, 80watt solar, eu2000 Honda gen., 2x group 31 AGM bats., 7100 btu aircond, electric rear step.

RamblinAnne
Explorer
Explorer
SidecarFlip wrote:
Farm Teck sells individual sheets in white and black. Been buying it from them for years. I make a couple products from it. I buy it by the roll but they sell cut to size sheets as well in any thickness you want.


http://www.farmtek.com/farm/supplies/ProductDisplay?catalogId=15052&storeId=10001&langId=-1&division=FarmTek&productId=278386

is this the stuff you're referring to? I didn't realize it was flexible enough to come in a roll! Do I want the HDPE or HMWPE? Any idea which thickness? I image the thicker the better. This is really a suitable product to install underneath my camper? I always imagined it would be some kind of hard flat plastic.
2013 Ford F350 6.7L Powerstroke Diesel DRW Lariat Crew Cab 4x4
2004 Bigfoot 25c10.6e
Full-timer

54suds
Explorer
Explorer
"Has the OP said the tanks are falling out? " no they did not
But as I noted " a word of precaution " information was shared that might be of use or interest now or later :S
2021 Chev 6.6 duramax ltz DBL cab,drw,4x/torklift tdn's,
1999 Bigfoot 1011

bigfootford
Nomad
Nomad
54suds wrote:
a word of precaution years ago i talked to one of the engineers at Bf and he expressed the opinion that the (soft) design of hanging tanks that flexed reduced hard shock/ stress on the attachment points when stressed by road hazard impact ,ect if you look, these are not very impressive usually either they use short 1/4 or 3/8 lag bolts screwed into 1/2 ,3/4 plywood flooring or 1/2 to 3/4 braces in the sub floor in ,in the past I had one tank drop because the the wood spit releasing the lag bolt


Has the OP said the tanks are falling out?

I think we need to wait see what the OP provides us...

I too have had support screws that were screwed into the wood and cracked, but are still holding really good.. No tanks have fell down... 17 years. I run with the fresh water full all the time... almost 200,000 miles.

I have measured the distance of the tank bottom to the bottom of the camper. The distance the tanks are suspended is enough that when the foam insulation is in place it causes the tanks to sit on the foam thus supporting the fresh water tank. The Gray tank is another story.

Jim
2000 2500 9.6 Bigfoot,94 F250, Vision 19.5, Bilstein shocks, air bags/pump, EU2000, PD 9260, Two Redodo 100ah Mini's, Aims 2500 Conv/Inv, 200W. solar, Morningstar Sunsaver 15A/ display panel, Delorme/laptop for travel, Wave-3 heat.

54suds
Explorer
Explorer
a word of precaution years ago i talked to one of the engineers at Bf and he expressed the opinion that the (soft) design of hanging tanks that flexed reduced hard shock/ stress on the attachment points when stressed by road hazard impact ,ect if you look, these are not very impressive usually either they use short 1/4 or 3/8 lag bolts screwed into 1/2 ,3/4 plywood flooring or 1/2 to 3/4 braces in the sub floor in ,in the past I had one tank drop because the the wood spit releasing the lag bolt
2021 Chev 6.6 duramax ltz DBL cab,drw,4x/torklift tdn's,
1999 Bigfoot 1011

TxGearhead
Explorer
Explorer
Please wear eye protection when you are working under the camper and looking up. Be sure it is well supported.
Safety first.
2018 Ram 3500 CC LB DRW 4X4 Cummins Aisin Laramie Pearl White
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2008 Bigfoot 25C9.4
2014 NauticStar 21 ShallowBay 150HP Yamaha
2016 GoDevil 18X44 35HP Surface Drive

SidecarFlip
Explorer
Explorer
Farm Teck sells individual sheets in white and black. Been buying it from them for years. I make a couple products from it. I buy it by the roll but they sell cut to size sheets as well in any thickness you want.
2015 Backpack SS1500
1997 Ford 7.3 OBS 4x4 CC LB

Grit_dog
Nomad III
Nomad III
RamblinAnne wrote:
bigfootford wrote:
Grit dog wrote:
Find a local plastic shop and see about getting a sheet of HDPE or umhw.
That or aluminum.
If it's not needed to hold anything up structurally then I'd also consider using the plastic/fiberglass paneling used in shower surrounds, from the hardware store. It would be more prone to cracking but it's cheap and easily accessible.


Excellent suggestion!

Jim


Awesome. Gonna try to get my hands on some of this stuff. Is it easy enough to cut with a handsaw? I'm assuming the rounded corners are a luxury and a square cut will suffice just fine? Thinking I'll just want to sand down the sharp edges a bit, yes? And how about the old screw holes? Should I fill with marine epoxy and just make new holes? I hate the idea of making new holes but I'm thinking it needs to be done. I assume the underbelly is not as big of a deal as the roof where lap sealant is needed to assure no leaks, correct? I can just screw the new piece on and be done with it? Or do I need to seal it up in some way?

Sorry so many questions.. Just want to make sure I am doing this right the first time.


As mentioned, it will cut easily. Straight cuts you could score with a utility knife and snap. I'd seal the seams after installing rather than "gluing" it on. But if the original stuff isn't sealed or water damaged then skip that step. Bottom doesn't really get wet in the back of the truck, but I'd absolutely seal the back portion where it overhangs. This catches road spray.
Pre drill the frp or plastic for screws. You can fill the old holes or not.
How close you match the corner cuts is up to you, but a coping saw, hack saw or jigsaw will cut the corners easily however you want them.
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SidecarFlip
Explorer
Explorer
bighatnohorse wrote:
FRP - Fiber Reinforced Plastic - available in sheet stock a big box home stores. You'll probably want two sheet and laminated them together for additional thickness.
I don't remember how to cut it but I think it scores with a utility knife and then snaps. Make the cuts before laminating them together.


It cuts very well with a table saw or hand power saw using a fine (many tooth) plywood finishing blade. Just wear a particle mask, it's dusty.
2015 Backpack SS1500
1997 Ford 7.3 OBS 4x4 CC LB

bighatnohorse
Explorer II
Explorer II
FRP - Fiber Reinforced Plastic - available in sheet stock a big box home stores. You'll probably want two sheet and laminated them together for additional thickness.
I don't remember how to cut it but I think it scores with a utility knife and then snaps. Make the cuts before laminating them together.
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'15 F350 6.7 diesel dually long bed
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HMS_Beagle
Explorer
Explorer
I don't know this particular model, but on a Bigfoot typically the tanks are held up to the floor above the basement my straps. The covers you see cracked are just covers and have no structural function. I would not attempt to make them have a structural function as there is nothing very solid to tie them to. The structure is all in the sides of the lower box and in the floor that you walk on, above the basement compartment.

Reinforcing the tank mounts would mean better straps or hanging something off the floor. The foam that you sometimes see under the tanks I do not believe is for support, it is for insulation to keep them from freezing in the winter.

Replacement covers could be made from any this, suitable material. The best would be real fiberglass panels like G10 material from McMaster or others. This will not crack nearly as easily as the chopper gun stuff used by Bigfoot (which is similar to shower enclosure stuff). Either will cut and drill with ordinary tools. You may as well drill new holes, through you could use the old cover as a template to match the new one. The screws merely attach the cover, they do not hold up the tank.
Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear

TxGearhead
Explorer
Explorer
If you do remove the cracked panels, I think while they are off you might consider adding some support for the tanks. Maybe some galvanized or even nylon strapping. Use some lag bolts or self drilling/self tapping screws into something solid...probably the same thing the factory screwed into.
Others may have better ideas on supports, or if they are even needed.
2018 Ram 3500 CC LB DRW 4X4 Cummins Aisin Laramie Pearl White
2018 Landmark Oshkosh
2008 Bigfoot 25C9.4
2014 NauticStar 21 ShallowBay 150HP Yamaha
2016 GoDevil 18X44 35HP Surface Drive

bcbigfoot
Explorer
Explorer
I have a 9.6 2500 series, I replaced the hdpe (puck board) with 5/8 painted marine plywood across the entire bottom of camper. Bigfoot chopped out huge areas of structure and then used 1/8 hdpe to cover the holes. This is one of the reasons why the overhang is sagging. The overhang and wings are being crushed or pushed upward by the weight of the camper above, they are just limp noodle without any bottom structure. The plywood gives the bottom structure again and it eliminated 90% of the sag in my camper. I also laminated 1/2 inche plywood along the basement walls. With the plywood in place I was also able to put some extra thickness of foam insulation between the plywood and the grey tank, this removed some of weight from the problematic seat belt straps.
2002 Dodge 3500 2wd dually, cummins, 4.10 gears, 10500gvwr, Rancho 9000's shocks
2005 Bigfoot 259.6E, 80watt solar, eu2000 Honda gen., 2x group 31 AGM bats., 7100 btu aircond, electric rear step.

RamblinAnne
Explorer
Explorer
bigfootford wrote:
Grit dog wrote:
Find a local plastic shop and see about getting a sheet of HDPE or umhw.
That or aluminum.
If it's not needed to hold anything up structurally then I'd also consider using the plastic/fiberglass paneling used in shower surrounds, from the hardware store. It would be more prone to cracking but it's cheap and easily accessible.


Excellent suggestion!

Jim


Awesome. Gonna try to get my hands on some of this stuff. Is it easy enough to cut with a handsaw? I'm assuming the rounded corners are a luxury and a square cut will suffice just fine? Thinking I'll just want to sand down the sharp edges a bit, yes? And how about the old screw holes? Should I fill with marine epoxy and just make new holes? I hate the idea of making new holes but I'm thinking it needs to be done. I assume the underbelly is not as big of a deal as the roof where lap sealant is needed to assure no leaks, correct? I can just screw the new piece on and be done with it? Or do I need to seal it up in some way?

Sorry so many questions.. Just want to make sure I am doing this right the first time.
2013 Ford F350 6.7L Powerstroke Diesel DRW Lariat Crew Cab 4x4
2004 Bigfoot 25c10.6e
Full-timer