FWC Hawk, 8 ft Flatbed on 6 ft Truck Owners

[dcoy]

Interested in other owners experience with this setup. I know it is a somewhat unusual application, and it has become clear to me why that is the case. As you can see from the second picture, this rig likes to break the rear window of the camper. This is the second time this has happened to me. Both times we were carrying bikes on the back. After the first episode, which occurred at a small dip or step on the Valley of The Gods road, the rig underwent extensive suspension upgrades. Its a 3500 RAM, so I upgraded to Carli Dominators and a new custom leaf pack on the rear. The rig rides much better offroad now. I "assumed" the problem was "fixed" so we loaded up for a trip with two bikes and a mostly unloaded 1UPUSA tray. The result is the pic above. It is intuitively obvious that so much weight behind the axle is ill advised but the fact that the suspension upgrades did not remediate the problem is a strong validation of this.

So the plan for now (short of retooling the whole rig to a 6 ft bed) will be twofold. First, rather than replacing the rear window with another paper thin FWC rear window, I will pursue a custom, more robust piece of glass. Second, I will put the back of the rig on a diet. Will remove those 85#-when-full Jerry cans and limit the cargo to two bikes and remove the ebikes battey. There is not a good alternative in our setup to the bikes being on the back.

It would be helpful/interesting to hear any other thoughts/experiences regarding this issue.

Thanks

 

[dcoy]

By the way, although heavy, the rig is not technically "overweight" as the rear axle is 6500# which is within GVWR and tire capacities. Some have disparaged it as such. The suspension mods are to improve performance, not an attempt to compensate for the rig being above spec.

 

[kmcintyre]

That is a unique setup for sure.... I don't have any suggestions but since I've not seen or heard of this happening before, something is amiss for sure. Good luck.

 

[Machinebuilder]

I’ve been thinking about this.

It would seem that chassis flex is causing the camper to flex and break the window.

Maybe you are an example of needing to add a floating connection from the flatbed to the truck frame.

I see this discussed on Expedition portal, I really thought mostly it fixing an imagined problem.

 

[JHanson]

I don't think the issue is suspension; I think it's leverage. All that weight out back is stressing and twisting the structure and there's no solid support underneath for it. If the suspension isn't bottoming out forcefully, only flex would do that to the window.

 

[dcoy]

Thanks. Interesting but sorta disconcerting. One observation that would support these last two comments is that I did notice a fairly marked deformity in the now empty window frame after the second window break. It was a divot in the frame that looked like an axe had hit it. I would think twisting the structure would do that. At the time of the second break, there was no noticeable bottoming out, in fact it felt quite cushy. That being the case, the "fix" probably would be going from an 8 to 6 foot flatbed and getting rid of the tunnel box, which I think is the fundamental defect. I assume decreasing weight in the back would band aid the problem, which I might as well pursue for now. I suspect trying to make the flatbed and/or camper more rigid would be more expensive and time consuming along with having unclear benefit.

 

[dcoy]

Need to dig up the discussion on ExPo regarding floating connections as well.

 

[FAW3]

Nice rig...I love flatbeds!

I tend to agree that the back of the Hawk body is simply flexing too much for the window. I think the primary cause is the weight/mass of those filled jerry cans bolted to the Hawk body. The traction mats are likely fine there. If your bike rack is tied into the rear Hawk body and not the flatbed...that is an issue also. The bikes may not weigh much...but when you're doing terrain consider both the static weight as well as the dynamic/shifting momentum that may be adding to the problem.

I have a flatbed and there is flex. If you're not running on a rubber stall mat or similar you may want to try one. I also I run with my clamps just snug, not hard down tight. The clamps and mat allow some minor flex give.

Fix the window and run empty cans or remove them. Run for awhile and test.

If that works I'd rethink the jerry can mounting. Perhaps mounting them sideways (rotate 90 degrees with filler up) right above the flatbed with a rack built into the flatbed, or put them into your pass through cabinet behind the cab.

 

[camelracer]

That window is a brittle shear wall for the cantilevered back of the camper. I would suggest replacing the tempered glass with safety glass and reducing the weight hanging back there.

 

[dcoy]

Thanks for the above input. At least to start, I'll be ditching the Jerry cans, limiting to two bikes, pulling the ebikes battery (which is about half the bikes weight), and getting a decent piece of glass to replace FWCs fragile one (and have a second one made as a spare if I fail).

Beyond that will look into that stall mat reference and am looking into getting the bed to "float". Another question for you all: Does anyone have a recommendation for someone with expertise in flatbeds that could possibly do this mod?

Finally, I'm not beyond reconfiguring the rig for a new shorter bed without the tunnel box. I'd have to move the spare behind the camper but I suspect the net weight shift would be substantially forward and these headaches would not be an issue. Of coarse, the price tag would be painful but I would not have a rig that is permanently hobbled by its current design. I suspect I would benefit from the shorter rig in offroad performance and less rear end sway, which is quite substantial. I am installing a sway bar for that issue as well.

Thanks

 

[PaulT]

You might consider a polycarbonate window. They can be pretty tough to break.

Paul

 

[dcoy]

Yes. Have not ruled out nonglass options but the scratch sensitivity in a dirty offroad vehicle was said to be a reason to avoid that. I do know of some applications where they seem to do well though.

I am having challenges at getting people interested in engaging in producing a replacement piece of glass, mainly due to frame incompatibility (thicker glass would not fit in the original frame).

 

[Machinebuilder]

Yes. Have not ruled out nonglass options but the scratch sensitivity in a dirty offroad vehicle was said to be a reason to avoid that. I do know of some applications where they seem to do well though.

I am having challenges at getting people interested in engaging in producing a replacement piece of glass, mainly due to frame incompatibility (thicker glass would not fit in the original frame).

look into scratch resistant polycarbonate or acrylic. It's use in machine tool windows. There might be an industrial plastics supplier nearby that can cut it to size

 

[pods8]

Just glancing at this its not merely a hawk on a 8' flatbed, its a hawk mounted as far back as possible (which you noted) with ALOT of stuff hanging off the back of it too. You've recognized you had bikes on it both times it broke. The combinations of cantilevered loads (camper hanging beyond an oversized flatbed AND then stuff hanging off the back of the camper) is just flexing things, imho and as others have noted.

Was any of this mounting stuff that far back off the camper discussed with FWC? I'd be worried of the stress busting welds over time, frankly I would suggest inspecting the frame corners as best as you can (take the interior trim ring off and if possible look under the interior paneling. Thinking further out loud and not to be an alarmist but you may have already broken some welds around that window frame. That window isn't screwed to the frame its clamped and the frame opening it's a friction fit, there is some space between the window frame and camper frame (covered by the clamp flanges), to bust the window the rectangular camper opening has to shift out of square enough to squeeze down on the frame to flex the window and break the glass. Some welded joints are flexing a fair amount and if the welds haven't broken yet it probably won't be very long till they do once you've started flexing them that much.

IMHO, move that camper forward AND mount the bikes/etc off the back of the flatbed rather than the camper.

 

[dcoy]

Oh yes. I definitely appreciate the "force" (mass x acceleration) of the cantilevered loads. But the notion of potential compromise of the camper frame is a new and interesting thought that might be challenging to approach given that the the frame is concealed. Frankly, the builder, a FWC dealer at the time, expressed no concern regarding the loading characteristics of the build.

One thing which I should clarify but which I don't think helps that much given what happened is that the bikes are mounted through a receiver hitch to the frame. I think they still cause undue forces that result in frame flex, bed flex/twist, and camper torsion.

As I mentioned above, aside from making the flat bed floating, given the fundamental problem, I have also considered ditching the tunnel box and moving the camper forward on the existing bed. I would have to move the spare back but there seem to be a fair number of people with tires in the back with 6 foot beds without any problem. That would be cheaper than getting a shorter flatbed replacement. It might look sort of funky and there would be unnecessary rear overhang. Might be a relatively easy first step though.

 

[dcoy]

look into scratch resistant polycarbonate or acrylic. It's use in machine tool windows. There might be an industrial plastics supplier nearby that can cut it to size

Thanks. Guessing this would be easier than upgrading the glass too. Have not found a lot of enthusiasm from glass shops for that so far.

 

[pods8]

That’s good the bikes are on the receiver.

Not sure how the new interior paneling is but on the old ones you could remove the interior trim and screws around the inside paneling to peek in under it, just see if any of the welds at the corner are cracked. Ideally not, just something that came to mind of the breakage was from the opening twisting out of square.

 

[dcoy]

That’s good the bikes are on the receiver.

Not sure how the new interior paneling is but on the old ones you could remove the interior trim and screws around the inside paneling to peek in under it, just see if any of the welds at the corner are cracked. Ideally not, just something that came to mind of the breakage was from the opening twisting out of square.

Thanks. Will do some digging.