Tooling Up

We're kicking off a new project here to do a sizeable run of 20' aluminum hulled runabouts. We use the pull-up method of hull construction and are hulls are basically logitudinally framed. We're setting up the prototype so that her hull is perfect/sweet, and we're taking cutting templates off of her. I need some advice on two things.

1. An Accurate way to create CNC files from the cutting templates. (if someone says measuring tape I'll reach through this screen and slap them)

2. A method for assembly jigging that will hold all the plates together and allow seams to be welded with one pass.

The way I have the jiggs worked out, somebody will have to climb on top of an upturned hull and weld the keel, not my favorite idea. We have been building hulls using the contemporary pull-up method for some time, but they are a bit floppy during assembly. It is a pain to pull them square and straight, and even then every hull comes out a little different.

 

Can you elaborate on the "pull-up" method? Also, what thickness of aluminum are you using?
Creating cnc files from templates is something that I have a lot of experience with.
We have had dafters come in with years of experience and complex digitizing equipment ( the little roller thing that you just roll around the template and it draws it for you on the computer screen.) Well, after a week and three proof cuts the side template they were working on still was up to 1/4 off in some areas! I persuaded them to let me give it a try. 2 hours later I sent the file to our cnc cutter and by that afternoon we had a cnc cut part to match to our hard template. My accuracy? within 1/32" around the entire perimeter. My measuring device? Stanley Leverlock 25' !

 

**SMACK**

When I refer to "pull-up" I mean that the hull is welded together without the benefit of internal frames. Tension in the metal and the welding technique determine the shape of the hull. Framing is installed afterwards. It is the fastest, most inexpensive way to build metal hulls, and has been the prevalent method for building small aluminum craft out here on the pacific coast since I've been aware of. The term Pull-up seems to come from the fact that you're pulling the plates up off the shop floor, as opposed to "pulling down" over frames. I want consistency, so I plan to build the hulls over temporary frames. The trouble is that that's a big piece of tooling to have around.

Our hull bottoms and transoms are .2500" and our side plates are .1875". I looked at those digitizing equipment, I even contemplated making my on XY table with it's own "teach" function so I could digitize and cut with the same machine, but I haven't been involved in robotics and automation in six or seven years, and I'm very rusty, and the accuracy I'd expect wouldn't be good enough. I'm looking at photomodeler, it should be handy for all kinds of things. The error, from what I've seen has been around .125" or less on a 60' hull. I want to do 24' long templates, and while I have used a tape and a square before, I've found making perfectly parallel scribe lines a tweak dificult under the conditions. (plus I like to triangulate points for accuracy and it winds up taking me all day).

 

Thats what I thought you meant. Thats the same as we do around here, just never heard it called that before. I can fully understand not wanting to use a tape and square on a 60' hull. Thats over twice as long as I'm used to. I guess if you have the money and time to learn it, the new hardware and software out there would definately be worth the effort. As soon as something comes out that is faster and more accurate then my trusty tape measure, I'll be all over it! Just out of curiosity, what program do youy use to create cnc files? I am using autocad2002 right now. It is a little limited in 3D, but for 2D stuff such as template drawing I dont think it can be beat.
Do you really think your accuracy/consistency level would improve by pulling down over frames rather than using your current method? Also, whenever possible, I like to install my keel and strakes on an upturned formed bottom. Before the sides ever go on. Much easier to roll than an entire hull. Especially one made of the size and thicknesses you are talking about.
Joey

 

The boss has a copy of autoCAD 2000. I have completed an upgrading course for autoCAD 2002, and have my own licence of rhino3D. I want to get my own licence of intelliCAD (it's cheap). I use AutoCAD for practically everything though.

The Boss (Andy) made his first hulls from scale models, and they work OK, but I want to get more involved in using Rhino. We did a 19' jet boat at the end of last year using rhino. Without using jigs, it turned out reasonably well, but it could have been better.

We pull the hulls up into shape with them upright, weld it all up, put in the longs, 2 frames, the dashboard, the cap-rail and a number of other goodies, flip the whole works, back-grind and continuous weld the outside. Then we put our hull bottom goodies on like strakes, chine and keel guards, lifting lugs.

JD

 

Just to keep things updated, I have plunged ahead with the whole tooling program. I am getting involved with Canada's National Research Council, and they're helping me out.

 

Good Luck, Bro. Keep us informed.

 

In the aero space industry if we need to get the dimensions of a big irregular shape we use surveying equipment. Targets are light reflecting stickers that are placed on each curve or transition. A theodolite shoots a laser at the target and records its exact location in 3-dimensions. The theodolite downloads data into most standard cad programs. Once in CAD the shape can be flattened and fine tuned then sent directly to plasma table or cnc.

Total time ~ 2hours. Theodolite can be rented from most construction supply houses for $65/day. Targets cost about $1 ea in sheets of 20

 

There is a gadget specifically for measuring 2D patterns that is advertised in the classifieds in Professional Boatbuilder. You can also trace them on to Mylar and run the Mylars through a big scanner (local blueprint services or through ads in various CAD magzines). Then import them to Acad as raster images and trace them. Google "estes" and "baseline" on the web and you will find a lot of sources for help.

The professional software for doing metal boats is ShipConstructor www.shipconstructor.com . If you contact them, they may also be able link you up with firms that can help you if you don't want to get your own software. They are in Victoria BC, by the way.

 

I'm starting to get involved with people in the aerospace industry now. The theodolite is a fantastic idea. I had been contemplating buying Photomodeler to do the same thing, but it's expensive. I'm getting hooked up with contract tool and jig makers from an aircraft repair facility. I think I met one of the ship constructor developers, I think he's also involved in 3d scanning technology development.

 

Just to keep people informed, lines drawings and structural arrangement drawings have been sent out to the toolmakers at an aircraft re-manufacturer, and they will soon be presenting us with cost estimates for single purpose hull jigs and for multi-use jigs.

 

Mr.

Hi ,
Was wondering if you could provide me some details on how I could get the light reflecting stickers you mentioned. Company, online website ?etc. Tried running some searches but to no avail

 

You can actually rent a theodolite or transit from any tool supply and rental centre. They should have the stickers (targets) there. I do some checking.....since I'm such a nice guy.

 

Anybody out there have experience with building jigs?

 

Boat Design