Aluminum Recommendations For Helm

[boatnamesue]

I'm custom fabricating an elevated center console/helm control.  I will be elevating the standing platform approx. 12" off the deck.  This structure will bear at most 500lbs of weight.  And I want to use the lightest possible AL pipe without comprising structural integrity. Nominal size pipe of 1.25" preferred, 1.5" at most.

I have read 6061-T6 is most commonly used for this marine application, as well as 6063-T6. 6061 being more resistant to corrosion than 6063, but not taking to anodizing or powder coating as good as 6063.

The picture below closely resembles what I'll be doing.  Only the horizontal piping will not wrap around, composing 1 supporting platform pipe.  Instead, there will be 2 horizontal pipes that are welded to the vertical pipes.  The aft end of horizontal piping will bend down to deck, secured with mounting flanges.

Appreciate your thoughts or other options I did not mention.

[love2fish]

I have a tower on my boat that is made of 6063 and it maybe weights 125lbs. the legs on mine are 2.5" and the rest is 1.25 for the sun shade and ladder steps.
I would not suggest 1.25 for your main support bars as it will require more support gussets to firm it up, and an even bigger factor- its a pain in the A$$ to get wires through. 2 hydraulic lines will fill up 1.25 pretty quickly. 

[Blue Agave]

1.5" minimum.

[boatnamesue]

I want the same size pipe as my leaning post.  I measured it's circumference today, which when divided by 3.14 gives the diameter.  It's diameter is 1.75" O.D.   And most likely its wall thickness is 0.25.  So it turns out that a 1.5" pipie is the size I want, not 1.25". 

Re: Running wires in the pipe-
I'll run cables/wires outside of piping through flexible corrugated tubing, like you see in the picture.

[wingtime]

6063 is used anywhere you want to bend the tube. 6061 is used for straight sections since it is a harder alloy. Remember sizes pipe are measured by nominal ID where tube sizes are measured by OD.

[boatnamesue]

6063 is used anywhere you want to bend the tube. 6061 is used for straight sections since it is a harder alloy. Remember sizes pipe are measured by nominal ID where tube sizes are measured by OD.

Referencing the picture I posted of the tower....are you saying that all the curved/bent sections of the aluminum are 6063 and the straight sections 6061?  Cause I don't see a welded junction anywhere on that tower except at the terminal ends.  Unless this particular tower is constructed totally of 6063.