Foamie damage

[dancam]

This is a video of the damage to our foamie. I wouldn't call it a failure but a design flaw on my part. I am hoping to have a discussion on how to prevent this on pop-ups. Am I the first one to make a pop-up foamie or are there others?
Our trailer worked just fine for the 30,000km cross-Canada trip even with the cracks. The large split inside got a lot worse sitting over the winter. The trailer has done 35,000km total. I forgot to video some other big cracks but you'll get the idea.
https://youtu.be/YXvr3wtJR4A

This video shows the lifting and lowering of our trailer, how its works and the inside better if you are interested: https://youtu.be/vjKTVDBH20g

My build thread is here if anyone is interested in what I did: [URL]https://r.tapatalk.com/shareLink/topic?url=http%3A%2F%2Ftnttt%2Ecom%2Fviewtopic%2Ephp%3Ft%3D66816&share_tid=66816&share_fid=39727&share_type=t

Pop-up foamie for Cross-Canada trip[/URL]


My design required wood for support for lifting and holding up the top half of the trailer. The wood added mass so there was more flexing, my frame wasnt rigid enough I dont think so I got paint cracking from the flexing, the worst being at the joints in the wood. Some of the roads we travelled were incredibly rough in Alaska, the Yukon and Quebec. I dont think we noticed cracking on the top half until maybe 20k into the trip.

Do you guys have any suggestions or tips for anyone who wants to make a pop-up foamie in the future?
-A design with no wood would be idea I think but I have no idea how you would do that.
- to make it with wood i would suggest starting with a very rigid frame, even if that means its heavier. Have as few wood and foam joints as possible- i should have just gone and bought 12ft 2x2's. Try to build some sort of fixture or something that the top half comes down into when lowered and it cant flex side to side (but don't forget about keeping out water and dust). I don't think that would be enough to have it not crack but it would be better.

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[tony.latham]

Do you guys have any suggestions or tips for anyone who wants to make a pop-up foamie in the future?

That open-box design as you know, is a problem. But if anything would work, fiberglass/epoxy instead of PMF. You could reinforce the stress points with extra glass.

But hey, you guys had a grand adventure in it.

Tony

[Pmullen503]

Big plywood gussets in the corners. Like 2x2 feet, glued to the roof and screwed to the embedded wood framing. Repair the exterior with canvas patches.

[pchast]

How about different door latches............. Cam locks.
Like a double hung window latch in design to hold things
stable?

[GPW]

How about a better design … ? (You guys are Brilliant !!! ) Although 35,000 km is pretty GOOD in anybody’s log book !!!

[GPW]

Hey Dan , maybe we can all put on our thinking caps and help out with your dilemma ..??? For instance … Do you think the wood bracing made it too rigid when it might have done better if having more flexible … ??? We saw those videos of Rigid trailers coming apart , when a little flexing would have saved them … ( Just a thought )

[RJ Howell]

I came to this group to learn about foam construction and see how I could implement it into my Ultimate build. I also will have a lift top.



Your build concerned me as it did not have a full connection. Open ended.. My first thought is: Do you think the damages were caused when traveling? Or storage and snow weight on the unit?

Traveling, I would think bracing, like a flip-up or removable brace at the door openings to add something structural. Possibly doing the same inside, side to side. Outside, my mind goes towards a 'French cleat' or z-clips to secure wall to wall.

On my build I'm thinking a aluminum 'U' channel on the foam edge to give it support. No sure what you did along those edges.

I'm certain that you will come up with something! You have the ability to design and build this, you certainly have the ability to work through this!

As a new member here, yet feel part of the foamie family, anything I can do to assist, ask (well short of driving up there..LOL).

[tony.latham]

Do you think the wood bracing made it too rigid...

I'll argue that it's the flexing that caused the failure. It wouldn't have happened if it wasn't made from two open boxes which of course wasn't an option. The only way to make something like that work is to prevent flexing. Stiffen it up.

Torsion boxes are strong because they don't flex.

Tony

[Pmullen503]

Watching the video of the top lifting, I wonder if the air cylinders on four corners isn't part of the flexing problem. It looked pretty easy to rack the top from unequal lifting.

It should be possible to have it securely clamped in the down position to eliminate flexing it that's a problem. Maybe a removable brace to tie the back together while traveling and set/take down.

[John61CT]

Yes, the lifting points' loads must be well distributed IMO with a rigid metal profile.

The way the cracking radiates from the lifting points makes it very likely that was the cause?

[Pmullen503]

Yes, the lifting points' loads must be well distributed IMO with a rigid metal profile.
.......?

Or a mechanism that guarantees all four corners lift together like the cable system in a pop up.

[John61CT]

Even then, lots of point loading stress there.

If the usual 5x8 foamie sure, but that unit is so long. . .

Maybe 8 lift points would work?

Personally I need heavy load-bearing rack up top anyway, so I plan to just hang the top half from that,

completely independent metal exoskeleton, the living pod within can be removed when in work / utility / hauling mode.

[RJ Howell]

Yes, the lifting points' loads must be well distributed IMO with a rigid metal profile.
.......?

Or a mechanism that guarantees all four corners lift together like the cable system in a pop up.

Sorry, but I dis-agree with both you. Most of the lifts are done with spring loaded arms and no way are they 'balanced'. Look at the RTT's and see how they work. Granted most are angle lifts, yet some are still full lifts. No way can you release a clamp and even think it will go up equally. I don't see that as the issue here.

This lift-top looks like a 50/50 lift. Most are 75/25 or less. That makes them work well. With this, we're far beyond that and what can we recommend as a solution?

He has a pneumatic lift. My thought is it's under powered and requires regulators to balance the lift. How to do that with what he has? Come on folks.. We have a ME here that can assist in a add-on for him?

[Pmullen503]

In this case (lifting a box that fits over another) lifting the box straight, without racking is important. RTTs and most pop ups have soft sides so lifting evenly is less important.

In terms of something to fix the problem (assuming the problem is uneven lift) maybe a cable system at the corners that constrains the top as you lift it to keep it straight. So, pressurize the pistons and slowly crank out the cables to allow the pistons to lift. Crank down against some air pressure to lower.

[RJ Howell]

Do you think the wood bracing made it too rigid...

I'll argue that it's the flexing that caused the failure. It wouldn't have happened if it wasn't made from two open boxes which of course wasn't an option. The only way to make something like that work is to prevent flexing. Stiffen it up.

Tony

To this I agree.

Too many areas of too much flex. Structural elements are good, yet how they are used is important (this I'm learning). Curious what was used and where in portion to the cracks. I already see in my build were I could have done better (as do we all as we build).