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Update: my cardboard dog ramp held my 70 lb lab but snapped where I didn't expect, and of course it was the bottom flap
So last week I finally got tired of my lab Ranger limping up the couch, and I built him a cardboard ramp out of two Amazon boxes and a tube of hot glue. I drew it up, cut the side rails, glued the deck on, and tested it with a stack of books first, which held fine at around 40 lbs. Ranger walked up it like a champ on the first try, tail going the whole time, and I was feeling pretty smug. Then I sat on it myself for like two seconds and the bottom flap folded under the deck and the whole thing pancaked. Turns out cardboard is way stronger when you push down on the middle of a span than when the load sits right on a flap joint. I had no idea the failure point would be the flap and not the deck, and honestly my 6 year old thought it was the funniest thing she's seen all week. Should I double up the bottom layer, or just add a couple of wood dowels under the deck and call it a day?
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val_taylor15d ago
What made you test with books instead of something that actually puts weight right on that flap, like a bag of dog food or a dumbbell? Books spread the load out, so they never really stressed the joint that failed. The flap folded because all your weight hit the hinge where the bottom meets the deck, and hot glue has almost no strength when it gets peeled that way. Dowels would help the deck, but they won't fix a flap joint that pulls apart. Have you thought about running a strip of wood or even a folded cardboard beam along the inside corner where the flap meets the deck to stop that fold from happening at all?
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