OK to hoist shell by rack?

I love your explanation, but to test your theory I'm going to try lifting my wife from her toes and bra tonight just to make sure.

 

I would NEVER lift my cap by the roof rack, it just ain't worth finding out.

 

Just got done making my system up in the garage. This will be a little lengthy but hopefully it’ll clear up some stuff.

I did not attach anything to the rack itself but to the tracks that are used to attach the rack. I used anchor points rated to 400lbs with the parallelogram type nuts that attach the feet of the rack. I had to get shorter M6 bolts to attach them. The original from the Thule feet bottomed out in the tracks.
I trusted that but not the connection between the feet and towers (the one that uses the locks) to hold the weight of the topper.

I used a trailer wench from Harbor freight that was rated to 1000lbs and 5/32 cable. The 4 sections of cable to go to the anchor points are 1/8 inch rated at 880lbs. Obviously use thimbles and clamps for the size wire you use.

The weakest point of the whole thing are the carabiner clips thaycwuicjly attach the cables to the anchor points. They are rated around 120. So the top split four ways should be less than that.

I need to work with the lengths of cable to find the balance point of the topper so it lifts level. And change one of the fixed pulleys to a swivel. But it lifted fine from the tracks. But I’m only going to use it for lowering and lifting. When it is stored up I will put two ratch straps under it attached to the rafters to take the weight. But this is a great solution for a single person.

Let me know if ya’ll got any questions.

 

A good start but unfortunatelty it has some significant engineering flaws.
That arrangement will increase the force exerted on the rails since the vertical component is only one of the vectored forces, the other being the side load which given that tight cable angle will be even greater than the vertical force and have a negative effect on the holes in the fiberglass. While the bolts may or may not rip through you also increase the likelyhood of the slot nuts pulling through the track which is only 1/16" aluminum. If you want to do this I'd suggest a large custom slot nut and continuous backing plate like L-track on the inside of the shell. Using a sleeve around the bolts to increase the surface area where the stress acts on the fiberglass would help as well.

It would be much better engineering wise to have the cables run vertically to 4 separate pulleys before joining the main haul cable. I'd still reccomend at least double sizing the slot nuts and adding the backing plate but at least you can minimize the stress instead of maximizing it. You wouldn't need the sleeves then since the side load is gone.

Edit- another added benefit for those with lower ceiling heights is you can bring the cap much closer to the framing since the cable ends at each mount can go right up to each pulley.

 

I think you didn’t get to the part of my post where I mentioned it lifted fine.

If I were planning on storing it like this, then yes I would have put some more thought and money into it. This set up cost about $80. But again, like I mentioned, it’s only for up and down which would last only a matter of minutes.

 

No, I read the whole thing. I'm just suggesting it could be more fine by avoiding those stresses. Even just the time spent lifting more than doubles the strain on the cables, rails, slot nuts, bolts, and fiberglass because of those 4 angles, all of which are completely unecessary. It isn't graduate level engineering, just high school trig. If you're satisfied that's fine by me I merely wish to educate you and others how it might be done a bit better.

 

Just my two cents and your set up looks nice and stout. Me personally,I would not hang a canopy by the roof tracks. The load is designed to go down not up. All the weight is being pulled at just 4 points ,as opposed to being spaced over the length of the track down ward. Most set ups I’ve seen run support under the canopy so its being lifted by the bed rail of the canopy. There are some nice pictures somewhere on here.

 

It’s actually pulled through the entire entire track because of all the bolts that hold it to the top. It’s like 8-10 bolts running the entire length. And that’s fine if you wouldn’t do it. I was just posting on here to say it could be done and nothing detrimental happened. I’m still advising against storing it with the tracks, no matter what high school trig set up you may have.

 

What the hell is ‘more fine’? The whole thread was started to see if it was safe to lift by the rack. I just showed everyone here it is possible and shouldn’t cause harm if you do it by the tracks, still not advocating that you store it like this.

I’ll be more than happy to give you lengths, angles and weights if you want to do the ‘high school trig’ necessary to calculate all of your speculations. (I only hold a B.S. but I’m pretty sure when you start working with vectors it’s actually Physics involved). But in the end is the top was suspended in the air, nothing broke, bent, cracked or otherwise failed. In the end I’ve done this successfully, and you just have your opinion.
Please just return to your bridge.

 

Dont get your panties in a bunch, I actually like most of what you've done. I have the Thule tracks on mine and the opposite corners are exactly 6' apart. My cap weighs ~200lbs so each corner could ideally only have to support 50lbs if the cables were vertical. At anything less than 20" separation between the cap and that single haul point in your set up the tension in each cable becomes greater than 100 lbs, twice as much as is needed and easily avoided. The goal is not to see how badly you can do this and get away with it but how to do it with the least risk to the cap. You made a good start but it could be improved.

I referenced this calculator to get results for my cap. The load and mount points are inverted and "sag" is the distance between the cap and where the cables join.
https://www.ropelab.com.au/two-point-anchor-calculator/

 

I've been trying to figure out how to remove my cap solo just so I can replace the seal - my carport is metal and not very stout, so I might try and find a low enough branch to drive under then attach some ratchet straps to 2x6s under the cap to lift it. Tried lifting it with a helper but the fiberglass felt like it was flexing when we picked it up from the sides so I need to figure how to distribute the weight better.

 

Slide the 2x's under it and fasten them to the cap first. Mine has bolt tabs but a small plate to clamp the edge would work.