Knowing there are a few engineers on here I have a question. I will be adding a roof rack to my camper shell, canopy, topper (whatever it is called in your neck of the woods). I understand static and dynamic load (down force) for a rack but my questions is in regards to lift. I plan on installing an automatic boat loader and will be carrying a 12 ft semi v boat upside down on the top of the rack. Have a few ideas but would like to know how critical hardware size is to counteract "lift from a rack and contents. Of course I am not asking how small hardware should be as I plan on a minimum of 5/16. Not asking about through bolting and backside reinforcement. Looking for the question of does cargo (in this case a boat) and a rack impart "lift" that should be considered when tackling this project.
Roof racks
- Thread starter Cammy
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trasko
Member
You seem to be asking for engineers' input and not mine, but I'm going to give it anyway since no one has taken the bait. It sounds like you're rigging some stuff and you have some idea of what you're doing. I'd say go for it and build it as safe as you can. That's what I'd do.
To directly answer what I think your question is: Yes, you need to resist movement in an upward direction. Significant bumps and who knows what else will cause the boat and rack to exert an upward force on the shell. Will the boat exert "lift" like an airplane wing? Maybe? Kinda like someone typing a mattress to the top of their 1992 Corolla with some twine and going down the freeway. Seems like I see that at least once a month when I lived in the city.
To directly answer what I think your question is: Yes, you need to resist movement in an upward direction. Significant bumps and who knows what else will cause the boat and rack to exert an upward force on the shell. Will the boat exert "lift" like an airplane wing? Maybe? Kinda like someone typing a mattress to the top of their 1992 Corolla with some twine and going down the freeway. Seems like I see that at least once a month when I lived in the city.
pabearhunter
Well-known member
Most manufactures of pickup caps VOID the warranty if YOU put cargo bars on.
If they are ordered with the cap it is built that way for support. At least that is what I was told.
If they are ordered with the cap it is built that way for support. At least that is what I was told.
trasko
Member
I hope (and think) this is not true. I put my Yakima track system through the thick part of my ARE and it's stout. I wouldn't use it for lots of heavy, long lumber but short of that it's been great. Also, despite being a bit iffy, I do lift the shell of my truck with a hoist by the rack. It's not iffy because of the track (that's not going anywhere), but the feet attachment to the track that worries me. It's held up fine thus far but I'm always well away from it while it's up in the air.
My Snugtop came from the factory with the Thule rack rails installed,garunteed. 750lb load capacity. Lumber rack to fit the Tacoma had 850lb capacity.
It also came insulated and carpeted.
I've had the rack on for 20 years,usually with a Yakima basket. I carried lumber,canoes,plywood,etc in windy conditions. Yeah you can get bounced around by semi's & gusts. Never worried about the shell holding the rails/rack. Shell to bed fastening is more important,IMHO.
It also came insulated and carpeted.
I've had the rack on for 20 years,usually with a Yakima basket. I carried lumber,canoes,plywood,etc in windy conditions. Yeah you can get bounced around by semi's & gusts. Never worried about the shell holding the rails/rack. Shell to bed fastening is more important,IMHO.
pabearhunter
Well-known member
Then call and ask the dealers ! When you install them yourself WHY would the dealer be responsible for any damage that MIGHT happen.
Thanks guys for the input. Have been scouring the web and find that most people who install racks on their camper shell are more concerned with static load weight ratings. Static weight being truck standing still how much weight can you put on the rack. Very few consider dynamic weight which is a shock load when hitting a bump. Often times these two weight ratings can differ several hundred pounds.
As for "lift" nobody seems to care. Not even manufactures of baskets and racks discuss the potential "lift" issues. I talking with an neighbor who used to haul a small boat in the same manner he commented that the boat "sucked down" to the rack when he was hauling it. Kinda like NASCAR cars who try to get air out from under that car to create downforce. Might look at some spoilers for the boat to create downforce and counteract the lift potential LOL!
As for "lift" nobody seems to care. Not even manufactures of baskets and racks discuss the potential "lift" issues. I talking with an neighbor who used to haul a small boat in the same manner he commented that the boat "sucked down" to the rack when he was hauling it. Kinda like NASCAR cars who try to get air out from under that car to create downforce. Might look at some spoilers for the boat to create downforce and counteract the lift potential LOL!
Everybody is an engineer we just don't have the education to prove it. Appreciate your input.
elkhnter
Well-known member
Reminds me of my aunt’s neighbor down in Clearlake when I was going to college in Houston. He was out mowing his yard in a t-shirt that said “As a matter of fact, I am a rocket scientist.”
He worked for NASA.
I’d just call the manufacturer of the camper you’re dealing with. Too easy?
Philthyphil
Member
What? Seems fine.
3855WIN
Well-known member
That’s @wilm3113 moving to Boston
OntarioHunter
Well-known member
- Joined
- Sep 11, 2020
- Messages
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I throw a 40 lb 17' kevlar canoe on my Jimmy's roof racks. You will very much notice the wind drag, especially a boat with a transom. Wind goes flying up over the windshield and gets trapped in the boat cavity. You'll also really notice the gas mileage goes to hell ... bad! Driving into a headwind is horrible. But I hardly notice it if the Thule enclosed cargo carrier is up there. Too bad someone doesn't make a snug fitting sock for canoe. That would probably bring gas mileage back up to near normal.
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