To build small aluminium boats - Need advice

[ronyt]

I run an engineering firm in Southern India which manufactures CNC Plasma Cutters. While looking for a product for our cutters and having had a long standing interest in boats and boatbuilding I'm seriously interested in setting up a Aluminium boat building shop to build boats between 15' and 25'. I do plan to invest in a hull design software package, will be able to get the plates cut by CNC plasma and also have MIG and TIG machines for Al welding. But bending the cut panels I have no idea how to go about. What sort of equipment is required? Presses, rolling machines, Press brakes ??? Also, what other equipment will be required apart from the ones mentioned above. Being new to the field any help would be greatly appreciated. Thanks.

With regards,

Rony Thomas

[marshmat]

Are you thinking of riveted or welded construction? Usually when working with .05 or .10 aluminum in boats you'll rivet the hull; or weld if you use 3/16" or thicker. Hard to define exact values though and I've seen it go either way.

I've never seen any kind of fancy equipment used to bend aluminum for boatbuilding. A lot of the welded-plate-aluminum guys just get a few workers to push the panels flat against the hull jigs as they're tacked in place.

It would probably be very helpful for you to go on tours of a few established builders to see how they do it. Best of luck.

[Thunderhead19]

We have a 12' shear, a 16' hydraulic press brake and a set of bending rolls as well as a couple of band saws and a chop-saw. There are ways to get around having to use any of them though, especially if you're eliminating all your manual cutting. We're not using CNC cutters yet. Check out www.metalboatkits.com I'm sure if you contact them, they'll be able to give you a better idea of what they do. They are pretty much exclusively CNC projects. They might have exactly what you're looking for...who knows??

No, I don't work for them.

[ronyt]

I would prefer to weld as I do plan to scale up the process for larger hulls. My MIG supplier says that his machine can weld down to 2 mm. I'll have to see how that works out. As for rivetted hulls how do I ensure a leakproof joint?

For manual bending, is heating up the plate with a blow torch a good idea during tacking or is there some detrimental effect to it? With bending rolls I suppose the curvature would be in one direction only or is the hull design supposed to ensure that? I've heard that certain design software let the NC cutter mark roll bending lines on the panels. Does anyone have experience with it?

Thanks.

[CDBarry]

1) Don't heat aluminum
2) You don't generally bend metal to form the hull, but you can use tight rolls for certain parts depending on the design. The hull plate should form to the hull curves by just being put in place. If it won't form under it's own weight, unless it is explicitly double backset, the designer made a mistake.
3) A general purpose press brake is needful. A flanging machine might be nice.
4) Double curvature is acheived in aluminum with an "English Wheel". This device can be made in the shipyard, plans are available on line or thru www.lindsaybks.com.
6) Go to www.shipconstructor.com for an idea of what professional level software is and does re bending lines and so on.
5) Aluminum boats are generally designed around the yard's equipment. Since you are starting out, you need to do some high level stuff first - called a "build strategy" and a "build policy", and then bounce it against your marketing plans. Get yourself a professional in the small ship productivity business to help you, subscribe to Professional BoatBuilder and go to IBEX.

[Arrowmarine]

Ok heres the deal with bending. Most of the bending we do here in the Pacific NW lies in forming sheet into structual and/or aesthetic shapes. Also for stiffening flat plate components (such as bulkheads, combing, or the edges of windshields) Two 1" bends do wonders for the rigidity of a 3 or 4 foot plate. I would say the majority of bending we do is in making boxes, lids, end caps, tanks, livewells, etc. etc. These can all be achieved with a simple leaf brake of about 6 to 8 feet capacity. (box and pan style preferably) Now, obviously, the thicker and longer the piece, the more labor intensive the bending. Also it takes some practice to hit your bend angles just by eyeing them. But it can be done(i've done it for 20 yrs)
Now a press brake can do all the above as well as thicker, longer pieces such as stringers, side trays and bottom plates. It also is much more efficient and productive. With a good selection of dies, you can do just about anything with a good press brake.
My former employer has the following: 12' shear 12'press brake 4' box and pan brake a three roll forming machine and a tubing bender. All parts are cut by hand. They produce 1500 boats a year from 15 to 28 feet with 100 employees.
I would say get a good press brake, shear, and some forming eqip(tube bender, roll former, etc) along with a ample supply of hand and power tools, and build from there.
Im rambling again. Sorry, Hope this helps!
Peace Joey

You will have to do some cost anaylisis, but I would stick to welding, especially for 15' to 25' boats.
Dont know who your mig guy is or what machine he has, but welding 2mm(approx .080) stuff is pretty common although it does require a skilled welder and a quality machine. I have welded .050 with a mig gun before but conditions have to be perfect. I have pulse mig welded .050 and that is suprisingly easy. I use .100 extensively with no probs.

[Arrowmarine]

CDBARRY WROTE
"The hull plate should form to the hull curves by just being put in place. If it won't form under it's own weight, unless it is explicitly double backset, the designer made a mistake."

Truer words have never been spoken! In my opinion, the #1 rule and guideline of Aluminum boat design.
Hats Off, CDB

[ronyt]

Thanks a lot for the input. Will hopefully get the project going soon.

[kmorin]

ronyt,
since one of the main incentives is the use of NC cut plates this implies that the hulls will be designed as developable surfaces. As CDBarry notes the cut sheets will lay to the formers without compound shaping. These designs include sheet metal shapes that can be made from flat sheets with some slight 'bulge' or flam.

Hull design software packages, that run on a PC, now does this operation almost automatically. (MaxSurf, ProSurf, Autoship, RhinoMarine, MultiSurf to name just a few) Once the design is created the surfaces can be tested for curvature to insure they will "lay flat" in almost all the leading marine software applications.

In boats smaller than 25' compound curvature is not a very cost effective design and construction feature. The effect of compound curvature as a matter of seakeeping in boat this small is highly debatable.

Since the entry into the boat business is an adjunct to the presense of NC cutting; don't get involved with boats that don't have 'flat sheet' hull panels.

The economics of boat building using NC cut plate is most competitive if plate nesting is carefully combined with the overall parts requirements. This reduces waste, reduces labor to layout and cut parts (NC's real cost savings) and reduces the SKILL level needed to assemble a 'weldable' boat.

The meaning of bend is permanently deform the metal - so that sheet which is laid on formers isn't "bent". Metal bent in a press brake is plastically deformed into a bend while sheet metal that 'bends' along chine to topsides joint is merely flexing along its major axis (well within the elastic modulus of the material) and would return to a flat shape if sawn from the hull and laid flat on a floor or table. In discussing these procedures the distinction can be important and I don't know how these terms translate from one language to another.

The most effective business influence in your circumstance will be to find a competent marine designer who can draw the local boats in metal. In most cases the local builders (for fishing boats) will have found a shape that works the best for those waters and that fishery. It is difficult to convert these boats into metal without loosing their sucessful shapes. This factor justifies close scrutiny and disproportionately high attention in selection of the designs. The NC machinery will cut "anything" so choosing what to cut is most critical

If you will be producing metal boats for recreational and sport market the one main sucess point for aluminum is paint. Paint, Paint and Paint- that's the ticket to sucessful aluminum boat marketing to the sport market; since the general market prefers white and trim color strips to shiny bare aluminum.

My best wishes for sucess

Cheers,
kmorin

[martinmanfan]

Press brakes and slip roll machines will do the forming of your boat components...Rivetting is generally used to fasten materials less than .090"...Remember, welding weakens the tensile strength of aluminum...I am currently building a 14' semi-v that uses overlapping hat channels for the framework...

Michael J.

[williamptrs]

Originally Posted by ronyt

I run an engineering firm in Southern India which manufactures CNC Plasma Cutters. While looking for a product for our cutters and having had a long standing interest in boats and boatbuilding I'm seriously interested in setting up a Aluminium boat building shop to build boats between 15' and 25'. I do plan to invest in a hull design software package, will be able to get the plates cut by CNC plasma and also have MIG and TIG machines for Al welding. But bending the cut panels I have no idea how to go about. What sort of equipment is required? Presses, rolling machines, Press brakes ??? Also, what other equipment will be required apart from the ones mentioned above. Being new to the field any help would be greatly appreciated. Thanks.

With regards,

Rony Thomas

Rony, I am also interested in boat construction in India, please contact me at williamptrs@aol.com

[williamptrs]

Rony, are you interested in building boats of up to 14mtr in length?

[Ad Hoc]

One final point to mention, in addition to the above.

Just because you aqcuire some software to develope your plates (rtaher than the old fashioned way) don't try and think ahhh...design is easy, just press buttons. Be very focused, ergo, are you builders or designers? Stick to what you can do/know...

[williamptrs]

I own a boat and I have the design drawings for the boat.

[Ad Hoc]

williamptrs

If you already have the 'design dwgs' for boat, perfect.