Alum Cutting and Bending Costs

[GDFL]

I'm in the fairly early stages of designing an alum powercat in the 45ft range. I'm designing it to be easy and cost effective to build as opposed to emphasizing beauty. I'm looking for some very ballpark numbers on the cost of bending and cutting the plate. I'm assuming that I'll probably have it done by the same company that I buy the stuff from. I am familiar with sheet metal forming and I know that what I'm designing is easy to form in a press brake, so the prices I am looking for are for very standard bends. The skins will be from 4' x 8' plate of .375 and .1875 thickness and the frames will be probably of .1875 thickness. Assuming that I can deliver nested files for the cutting and good drawings for the bending, what costs am I looking at? Is cutting a quarter a foot? Is bending 10 bucks per bend? The bends are all straight along the 8' length, nothing conical or difficult.

I have some really good plans for reducing labor on my end if I can get the cutting and bending done at an affordable rate.

For those of you with experience, is it worth hiring the cutting of the bulkheads and transverse frames or is it easy enough to cut by yourself? I've followed builds where it is done both ways and never seen an argument to which way is best.

Thanks,
Garrett

[welder/fitter]

Garrett,
Though I cannot comment on prices, as they'd be different for our areas, consideration of cutting costs would be; the availability of equipment to you, and whether this is a business venture or personal project. If you have suitable equipment, it will always be cheaper to do it yourself, unless the time consideration is of great value. In other words, if you're making more per hour in whatever you do for a living than the supplier is going to charge you for the cutting, of course it would be worth having them do it.

[Red Dog]

Hi Garret
I cannot say what the costs of cutting would be where you are but, my experience on aluminium is the a 45' catamaran would be best plated using looong plates to avoid too many transverse butt welds.

If you are designing the job then you may be able to create sizes that are close to standard width plates or have your supplier cut them to the size.

You can cut aluminium succesful with wood working bandsaws & circularsaws with teeth to suit. Use bees wax to stop 'pickup'.

A 4" grinder with a tungsten tip blade is very hand for cutting shapes, but "BE CAREFUL" they bite.

Bending in a press brake or a wheeling machine is a simple exercise, provided you have a template to bend to.

The availability of appropriate extrusions for chines and keels can be a worry.

Attached a drawing of 37' cat, planing hull, made from 1/4" plate bottom 3/16" sides made in Australia.

Cheers
Red Dog

[GDFL]

thanks for the replies. I understand the money vs time argument, but it isn't quite as simple as that. I only get paid x amount per week whether I work 40 or 80 hours so any time for the boat is time that I wouldn't be getting paid for otherwise. I know that long plates are ideal and that transverse welds are less desireable, but that gives me a slight problem. The way I have designed the bottom of the hulls is to use thick plate with no stringers (only transverse frames). The bends and thickness give me plenty of strength. The problem is that the bends are longitudinal so my plate size is limited to the capacity of the press brake. An 8ft press brake is easy to find, but anything longer is not. This boat is a personal project. I am going to build one for ourselves and then cruise it for several years on a work hiatus. Once done cruising, we will explore the feasibility of selling everything from plans to turnkey boats based on what we learn on the cruise. My design is oriented towards a very efficient boat that is cost effective and relatively quick to build. Right now the design is a combination of 3 different building techniques/methods. It's not quite ready to share. I'm trying to get basic info so that I don't design in something that would be too expensive to be practical.

[Red Dog]

Good luck Garret, let's know how it goes.

Cheers
Red Dog