Forming compound curves in heavy aluminum plate

Korvello, I have built or rebuilt at least 20 boats in life. My first boat I believe was when I was 12. My trick is following successful designs and just tune them to my liking. I am not putting down many architects or designers, but many dont have the time to do a good design from scratch. I rather get a hull from bertram, chris-craft or whoever and make it better for my use. Then I spend alot of time fine tuning weight distribution, propulsion, etc... I dont get things right most of the time the first time. But neither do the guys with all the computers either. I treat boats like race cars, alot of trial and error.

I will not buy a new boat any more. I look at them and get upset. They are all lacking engineering, strength, ease of access, reliability , are inefficient and have too much power and don't carry enough fuel or water.

So seriously, I would buy a old good hull cheap, And work from there. You have a baseline. Then improve the boat to your needs. I leave interior layout and design for almost last. I just build interior as needed to fit things like electrical panel. I try to optimized boat design to usage. I work in broad strokes first and then work into detail as it goes.

Sure this method is not very efficient, or commercially viable but allows me to fix design mistakes in real world. Why build a design in computer then to realize the bathroom door wont close. I never know where I am going to put toilet until bathroom is built. Sounds simple but in boat bathroom an inch is alot.

Your probably asking, what does this have to do with boat design.
Unless you have built a 100 boats in your life from start to finish, it is hard to predicate boat weight. And if you cant predicate weight, then how can you predicate how your boat lays in water? Can you predict how much fiberglass is going to weight? Computer is starting tool but when you put boat in water that is reality. Same goes for props, rudders and heavy items like fuel tank.

Of course, the smaller the boat the easier. I would start by building a 12 to 14 ' Skiff type boat. It will teach a lot. Copy a simple design like the original Carolina Skiff. One of the things your going to learn fast, it is cheaper to buy a used Skiff and fix it than laying glass yourself...

I would love to see your design, and I will give you a honest opinion.... for free... lol

 

As already stated, the northwest passage has been open before, without any help from 'evil' humans. Is it not at least possible that it is opening for the same reasons today?

When the earth was considerably warmer than today (within recorded history) it was a time of peaceful weather, abundance and prosperity. But of course, this is not as newsworthy as doom and gloom

Jimbo

 

thank you TONY,very interesting aproach ,i've used the same before while remodeling or building houses ,now i can just tell what works or not without building it but it sure took a lot of trial and error and continuous last minute changes..................i'm building "my boat "not an experiment or learning cannoe i intend to go away for large periods of time , it will be a catamaran minimun 26 by 52 with a few original ideas; i will have some basic renderings hopefully soon and i'll submit them to you and maybe the open forum ,quite a lot of experienced guys here on the forum and i love debate and explore new points of view i'm sure i'll have a lot to learn and bugs to fix, that's why i'm picking your brain can't beat hands on experience of guys like you, once again thank you for your time.

 

I agree with that man, yeah industrial caster type wheels would be...




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blanchard grinding

 

TIG weld the seams?????????? wot on earth

 

lot of funny stuff being written here, one big no no, never tig seams butts, distortion is immense, mig at high speed
i use poly formers for forming, thats why there are no marks outside, the stretching is on inside where the heavy marks are
these are part of my book so scuse text

 

Jackphilps
Just read your comment had to laugh, and so I looked back. I agree...but which is worse, TIG welding the seams, heating the plate or forcing into place...unbeliveable what seems to pass as "acceptable ship/boat yard practice" for many!!!...and they wonder why aluminium gets a bad name!

 

Wheeling Machine

BillyDoc, I know your post is pretty old (from 2006)... Did you ever make a heavy duty wheeling machine? I am looking for help on building one. I want to form very heavy stainless steel plate (3/8" or even 1/2") and the wheeling machines I have found availible so far are too light duty. I would appreciate any help you could give me as far as plans you may have. I would have my engineer buddy help me beef up the specs on plans to handle the load I would need.
Thanks,
SteveFid

 

Hi Steve,

I still haven't been able to build that machine, the little economic downturn we seem to be experiencing here has made it darn near impossible to sell property . . . which is how I need to pay for that project. So, I'm basically waiting and polishing my boat plans. I did get some contract work recently, stimulus money from NASA actually.

Anyway, let me share my thoughts on the subject, in case they help.

I will (I hope) be rolling out 3/8" aluminum, so I did an experiment to try and get an idea of how much force would be required between the rollers. Once you get that number the rest of the design follows pretty easily. For the experiment I modified a hydraulic shop press by tapping into the high pressure side in the bottle jack that it uses for power and adding a pressure gauge. I measured the jack's piston diameter and did the math to see how many square inches were there, and as it turned out my particular jack had exactly 3 inches of piston area, so the pressure I read on the gauge times 3 is the pressure the shop press is applying. I next made a tool with a surface similar to the upper roller I intend to use and applied pressure to a scrap of aluminum similar to what I wanted to form. I say similar because this scrap was 5052, and I will ultimately be using 5083 . . . but I doubt there is much difference for the purposes of this experiment. When my tool indented the aluminum to a level I guessed would be sufficient for rolling, I noted the pressure. In my case that came out as 6,000 pounds. So, now I know pretty much all I need to know to design an English wheel. My roller bearings have to be able to support at least 6 thousand pounds, but I will add a safety factor to that of at least 2, so 6 thousand on each side of the axle.

Your engineering friend will be able to calculate the stresses in your frame, or you can download a copy of "BeamBoy," which is free, and do it yourself and just make it as strong as you like using conventional structural members like "I" beams, etc.

I do think you are going to have some special problems with stainless steel though, depending greatly on the particular alloy you are using. Most stainless steels "work harden" very rapidly. This is why when drilling SS you are better off drilling slowly, but with an aggressive bite (a lot of pressure) so you can get below the hardened area when the cutting edge comes around a second time. When trying to roll the stuff you are going to make a hard surface on the first roll, which will probably crack on the second. On the other hand, I know it's possible to do it, just not the technique. The reason I know it can be done is that I occasionally use large SS tank heads to make things out of and these are often rolled to shape, "spinning" them over a form actually. Since I can purchase these in 304 and 316 with no problem, it would seem you can at least shape these. The last one I used was 3/8" thick, by the way. This is a total guess, but I think the trick is to apply enough pressure on the first pass to not need a second. You might try Google or youtube with "Tank Head" and "forming" or "spinning" and see if you get any clues from that.

As for the actual design, take a look at Whoosh's post above and you will see a nifty design where the rollers are oriented so that the metal goes between them vertically. This makes it possible to hang the metal from something and swing it back and forth between the rollers, getting the weight off of your own personal muscles. Another thing Whoosh does is use urethane-treaded castor wheels (or something like that) for one of his rollers, and avoids messing up the surface that way.

Finally, I plan on using hydraulic motors for power, possibly driving the lower roller with the ring gear and pinion from a scrapped truck differential. This, of course, depends on what you can find when scrounging.

Hope this helps, I can't think of anything else at the moment.

BillyDoc

 

Compound curves in heavy plate

BillyDoc, Wow this is great information. Thank you so much for taking the time to give me this info. That is pretty cool how you did your test. I know I can wheel the stainless steel. I know there are companies that do compound curves in 1/2" thick stainless steel. I called a company to have them roll some stainless for me and they told me they were booked out five years and could not help me. Attached are some pictures of compound curves in stainless steel. Thanks again for the help. Steve

 

Not cheap for low quantities, but hydroforming would do a good job.

 

jonr, how do I use hydroforming when I do not have a cavity for the fluid?

 

The mold creates an entire cavity. But it could well be that it isn't applicable to the design (welded plates) you have in mind. Or that a brake press makes more sense.

 

1/2 inch plate is much too heavy for what you need if you are putting in transverse and longitudinal frames. no need, and harder to work with.

You should consider getting Tig out of your process. Tig imparts much too much heat into the HAZ, heat affected zone, weakens the joint and will put permanent deformation into the hull. Ie you pour on the heat, the aluminun expands from the heat, deforms, then you glue it together with the filler, and in essence you have welded in the deformation.

I know of no aluminum builder in the northwest that would consider tigging an aluminum hull due to this issue as well as speed.

If you decided to use 1/2 inch plate, you may have to make multiple welds which imparts even more heat.

In 1/4 inch plate, when we build our hulls, we start in the center of the boat and work out. Alternating side to side to allow for cooling between welds, start a weld, weld say 16 inches, the go to the other side of the boat, opposite location, weld that, then go kitty corner, do the same.

We have a manufacturing facility and I have about 5 guys using tig 8 hours a day, but we never would ever, did I say ever, put a tig torch onto a full sheet of aluminun on a hull.

You say quality of the weld is better with tig, sort of, it looks better, but there is no porosity in a mig welded weld, unless the operator is bad.

summary, 1/2 inch is too heavy, others say the same, follow their advice and leave the tig process out of the equation for the hull,

and consider 5086 h112 as the material for the skin,

 

Low tech compound curvature to the people

Take a look at these boats, one built in 1/4" Al 5083 and the other built in 4mm Domex 550 MC high strength steel. The steel hull was built by a builder who had never built in steel before. Only if you look at the hull very well will you even recognize that she is a radius chine design and not a round bilge. Advantage is that you only need a normal rolling machine. There is really no need to go thicker than 6 mm on Al 5083 but if thicker plate is preferred, go thicker. If you can roll it, you can build it.
Too much welding on a radius chine? Do the maths and you will see that the amount of welding required is very similar to what is required on a multichine hull.
On welding: If Mig is good enough for the pro who builds to Lloyd's, it's good enough for the home builder.
Here one of the best and most detailed metal boat building sites I have ever come across . http://www.odysseyyachts.com/Odyssey_Yachts/BUILDING_BLOG/Archive.html
What Brian's pictures prove is that with a pre-cut kit a home builder can achieve outstanding results within a reasonable time frame.