Hammock Hanging in a Prius (or other vehicle)

[Marcilla Smith]

The first time I saw someone hang a hammock in their vehicle, I thought it was one of the dumbest things I had ever seen in my life. But the more I thought about it... well, I've now been sleeping in a hammock for the past four years, now.

Unfortunately, the original connection I had in the rear began to tear the sheet metal, recently:


This is an image of the rear hatch, as viewed from the rear, from beneath, when it is opened.

Viewing an expanded version of the same photo, the large rear window is the one at the bottom of the image, and the smaller window is at the top (both are covered with sound-deadening stick-on aluminum). The metal frame running between them was originally covered by a plastic pane, removed while I'm working on this section:


As you can see, the foot of the hammock was originally attached by carabiner to a tie-down, as might be found in the bed of a pickup. When I noticed the sheet metal beginning to tear, I decided to replace the tie-down with eye bolts. As seen in the image, there are already circular holes in the sheet metal of different sizes, and fortunately, two of them were just the right size to hold some 5/16" rivet nuts I have, which in turn could hold the eye bolts.

Previously, I had inserted rivet nuts into the A pillars to hold the head of the hammock:


In this image, the window in the upper right is the windshield, just off screen to the right would be the driver side window, at the bottom of the screen is the window in the middle of the A pillar, and the metal frame is exposed by removal of the plastic panel that originally covered it. The eye bolt with the 550 cord tied to it is screwed into a rivet nut (brass colored part). The rivet nut, in turn, was installed into a hole in the sheet metal that came from the factory.

These eye bolts and rivet nuts are installed in the A pillars on both sides of the windshield, with 550 cord and carabiners running between them to hold the head of the hammock.

In the rear, I ran into a problem when attempting to install the rivet nuts. The void behind the sheet metal was too shallow to allow the rivet nut tool to enter far enough. To overcome this, I had to improvise my own rivet nut tool:




On top is the original tool. because there is a neck near the head without threads, I was not able to use a nut as a spacer to reduce the depth of entry. Instead, I used a 5/16" bolt (bottom of the image) and then added a nut and two washers as spacers before adding the collar from the original tool.

While it still took some finagling - and assistance from a friend - The rivet nuts at last settled snugly into their new homes in the rear hatch crossmember:

 

[bullfrog !]

So are you asking for ways to reinforce the area or did you figure that out already?

 

[maki2]

Why a single point installation? A better way would have been a plate with that had several holes for fastening it to structure and a loop in the middle to hand the hammock from. Or two eyes to string one end of the hammock into instead of a single attach point. That would allow the stress of the weight to be distributed to multiple fasteners in the sheet metal instead putting all the stress onto a single fastener. Sharing the load is a smarter approach in terms of engineering. Single point loading is a lot more prone to structural failure. Rivetnut puller tools are frequently sold in the hardware store in a small drawer, often the same drawer, as the Rivetnut inserts. The screw length on them is designed to be perfect for the task and they are easy to use. They are not expensive tools.

 

[bullfrog !]

lol!!! I just would drill all the way through, use big thick body wasters and a screw on ring as well on the outside! That would give some you a place to mount one end of the hammock outside and the other end to a tree when parking next to one! You could use a heavy duty handles for two point mounting and a better look.

 

[maki2]

lol!!! I just would drill all the way through, use big thick body wasters and a screw on ring as well on the outside! That would give some you a place to mount one end of the hammock outside and the other end to a tree when parking next to one! You could use a heavy duty handles for two point mounting and a better look.

Two point handles are a good idea. One can drill additional holes the right size match for rivet-nuts where one is needed into the stronger structural metal thickness. Being very careful not to drill into electrical wires is important.

 

[Marcilla Smith]

To update, let me start with correction and clarification.

In one of the photos above (reposted below), I misidentified the location of the windows to assist in visualizing its location. The driver side window would be offscreen to the left, not the right:


As for clarification on the set up at the rear, although I mentioned the two holes in which I intended to install rivetnuts, I only showed one in order to show greater detail in close-up. This had the unfortunate effect of leading to confusion on how many I installed, which was two - as seen below:


On the subject of "unfortunate effects," in my first experiment with attaching the hammock at two points in the rear, I decided to try the "button technique" which I've seen recommended for tarps, in which a hangman's noose goes around a small stone or other "button" which is placed into a tuck in the fabric.


This technique was a disaster, as it put too much of the strain on one point, causing the hammock to tear.
Previously, I've used sheet bends successfully, and I suppose I will return to them!

The other issue is that I passed a line through the end loop of the hammock, then tied off the ends of the line to the eye bolts - 2 in the rear, as at the front. The angles weren't good for it, I guess, as the leverage caused the eye bolts to pull the rivet nuts crooked.

Therefore, for my next experiment, I drilled through the outer skin. This required getting under the plastic outside in order to screw down onto the washers - steel for structure and rubber, underneath, for weather-resistance. I still had to drill through the plastic. This is fine, for my purposes, as my plans include building a rack that covers the rear hatch, so I need attachment points, anyway.

 

[maki2]

Maybe you should consider using a hammock that has a solid, strong speader bar at the end with the hatch and two eyebolts. The spreader bar with holes placed in ito for the hangers to engage into the eyebolts that are in direct alignment with the eyebolts will help with keeping the pulling force on the bolts in a more direct alignment instead of the pull being directed sideways towards a single mid point.

You are having a lot of trouble visualizing the effect of force loads. Stop and think much more carefully when designing structures. There are some illustrated basic engineering principles regarding load distribution on YouTube created by Universities including MIT. Those are free lecture series for beginners in the subject. In other words for younger school children as well as older adults. Never stop learning.

The purpose of an education is to keep you to continue learning new skills all the rest of your life. That is why you got assigned so many term papers where you had to do independent research on your own. You have a great opportunity here that has a lot more benefit than just hanging up a hammock in a Prius. The failures are teaching you that you need to learn more about the physics of load and weight distribution. That is very valuable knowledge that you will continue to use the rest of your life.