Sayre32 said:
However, I would think 1/16 would be pushing it pretty far. It feels weak to me, but you have much more experience.
Take a look at the Yazoo in my sig. All the tube in it was 1 x 1 x .063. Also, the decking was all .090, as opposed to the commonly used .125. That was my personal boat for a few years, and never had any issues with 300 pound coanglers, nor did I ever have any problems stacking 500 pounds of concrete block in it, for service projects on Allatoona. It does depend on deck design. I have a handful of times that due to the desired designs, larger spans and thicker material is more desirable.
I use .125 primarily these days primarily due to availability in my area, and the fact that a 21' stick of the stuff is often within 2 bucks of the thinner.
The way to make it lighter is to loose the angle and tube, and work instead with formed sheet (thinner stuff). Not to say that the extrusions should be eliminated in entirety, but instead of building a frame with extrusions, then sheathing them with sheet, use a combination of sheet and extrusions. Take a look at many factory built boats. Many of them have entire decks and all built with just brake bent sheets. On a factory boat, this is very cost effective, as once the designs are made, and the specific tooling (various brake dies, etc) acquired, it is pretty simple to shear and brake the same part over and over, and a decent deck can be built quickly in mass production.
However, unless weight savings are the primary goal, it isn't necessarily cost effective to make the patterns for one off boat builds, and the equipment needed to properly form such often costs much more than the small shop can afford, and is too big to be practical in a small shop.
I've been getting a local shop to do some brake work for me these days. When I finally get the shareaproject page made for a customers 1648 Alumacraft I'm working on. In certain places, I've used formed sheet as opposed to building up extrusions. In this particular case, even though it was a one off, the simple design did allow for time savings, and eliminated about 40 inches of welding, which results in cost reduction for the customer, even though the weight probably remained the same.