Is there a chart somewhere that lists wall thickness vs. weight capacity? I'm beginning to get good beeds so I'm fixing to start my first project - modifying my trailer to hold my kayaks.

Basically I'm going to build two removable "uprights", one front and one rear, that I need to hold about 500 pounds (there will be a 4' span between all uprights). I'm planning on using 1" square tube.

I have no idea what wall thickness to buy, I'm thinking .120 will be overkill, but I'm not sure if .083 will do the job.

Thanks!

Structural strength is partially do to wall thickness, but mostly due to the design and cross sectional area.

A soda can will support a lot of weight in the vertical direction but almost none when laid on it's side. The thickness hasn't changed only the way the load was applied. There are a lot of complicated formulas thet take into account, material strength, member design ( pipe vs square tube vs channel), general location of loads and there relationships to the member ( think lever or childs see saw). This is why engineers get paid big bucks to design things.

A simple thing might be to think of it this way. I can support a lot more weight from a 2" tube of .083 than I could the 1" tube you are thinking about. It's not the wall thickness its the member shape that makes the difference.

Basic rule of thumb is when in doubt go heavier. For your application most of this is unimportant. A good basic design will go a long way to making it work. Can you build it as a A as opposed to a T, The A will have better side to side bending strength when only one side is loaded. If you use a T how tall will it be? The taller the T the weaker it will be in bending. 4 kyaks high would need thicker or a larger dia tube than one for only 2 high.

My guess is that the 1" is too small unless it stays under about 3' tall. I would go with a larger size tube with a thinner wall if I could.

Not the best explanation in the world, but I hope it makes sense.

Another way is to look at similar designs already on the market.

For example, if current commercial designs use 2" square tubing and you plan to use 1" square for a similar design configuration, you may want to rethink the materials for your design

There are many books that have the charts, but Machinery's Handbook is probably the easiest/cheapest one to find. They go for $10-75 on Ebay depending on what edition you want. I have the 15th edition (1956) and it has all the charts & formulas to figure it out. I think 28th is the newest edition.

they are only kayaks. just brace it the right way.

Good info, thanks.

Here's the design I had in mind. This is not to scale, if I need I will crack open SolidWorks when I get home and get a better drawing, I threw this together in a couple of minutes with Paint.

http://gallery.jmcbroom.org/d/14303-1/upright.bmp



The kayaks weigh probably 150 pounds together, the 500 pound capacity was very generous. These will be removable so I can use the trailer for hunting and general hauling too. There will be two of these "uprights" 5 feet apart.

So, 1" .120 wall tube will be ok, right?

Back when I kayaked alot, before wheelin', and before my welding skills got more practice, I built 4 kayak racks for my own and friends rigs. I'd use 3/4" Sch40 pipe and 1" .120 wall square tube. Similar design; some braced, some not. None have ever broken. Go for it.

1"x.120"wall will work fine. to hold up kayaks.