Forming compound curves in heavy aluminum plate

[BillyDoc]

Does anyone have experience forming compound curves in 1/2” aluminum (5083) plate? I'm assuming I will have to build some machine to do this with but can't decide whether to pursue a “wheeling” approach or some form of “hammering.” I understand that the big shipyards use Eckold machines, and these certainly seem nice . . . but the price is a little (ahem!) beyond my budget!

Speaking of the Eckold machines, has anyone used one? And what is the operating principle? They look like they would be a “hammer” with a limited and precise stroke. Is this correct?

Any thoughts greatly appreciated!

BillyDoc

[Dagvald]

You need to investigate "english wheel". We hand formed compound curve sections on 53' round bilge aluminum hull. I
have photos. You could build one yourself. For forming aluminum I don't think you'd need hardened steel rollers. Industrial "caster type" wheels would do. It's surprising how little pressure is required on the wheels.

[BillyDoc]

Thanks for the info Dagvald. You're right, I could easily build an english wheel and even have a preliminary design for one cobbled up. And "wheeling" looks like it would be easier to actually do than the other approaches as well.

Do you remember how thick the plate was on that hull?

[Dagvald]

1/4" & 3/8". I think that the 3/8" may have been only in the twin keels which had a hydrofoil shape. I realize that you're concerned that 1/2" 5083 may be too "stiff" to hand form on the wheel. My opinion is that it can be done. My work partner on this job was a not particularly robust 76 year-old man. We made masonite templates of the hull curvature at at closely spaced stations on the hull and checked our progress with them as we worked the plate back and forth on the wheel.

You may want to look into the issue of work hardening of 5083 and the technique of annealing. We never found it necessary to anneal though.

On the assumption that you're talking about hull plating, the design of the hull framing may have some bearing on your approach. If the framing is both transverse and longitudinal you may have a structure stiff and fair enough so that you can "mold" the flat plate to the hull. In this case you'd use the fitter's repertoire of dogs and wedges, clamps, come-alongs and temporary fixtures to coax the plate onto the framing. An oxy-acetylene torch with a "rosebud" heating tip is hand for judicious warming to make the aluminum conform to the frame. Generally you'd start tack welding in the center and carefully work you way out as you simultaneously apply heat and tighten your clamps or whatever. By carefully I mean don't overheat an area - remember the torch can easily bring aluminum up to
its melting point!

You may be concerned about fitting this section of plating to plating already in place. I wouldn't try to pre-cut the whole piece and expect it to fit. If for instance if it was along the garboard I'd just transfer that line onto masonite and then onto the piece. I'd leave a couple of inches extra on the other sides and let them overlap. Once the garboard is fitted and you've tacked it appropriately then you can trim the overlap with your saw - set to cut just deep enough to make the trim cut.

What are you planning on building?

[BillyDoc]

Dagvald that is exactly the kind of information I was looking for. And your first guess was right, I'm planning on plating with half-inch over transverse and longitudinal framing. A twin-masted schooner, of sorts, of about 44 feet. I can foresee the possibility of sailing where there is the occasional iceberg, and I just plain like "sturdy" far more than I care about "fast." I also think that I can come up with a much more seaworthy craft with the extra weight to play with.

It should also be easier to control distortion using the heavier plate, and as I intend to TIG weld all seams this is definitely an issue.

As for the wheel itself, I was toying with the idea of substituting a reciprocating flat bed (picture something like a vertical milling machine table) for the larger (usually upper) wheel that can be powered back and forth with (perhaps) a foot control, and "anvil" wheels that come down from the top and apply pressure. This way the curvature will cup upward at the edges rather than the usual downward direction with a conventional wheel. That upward curvature will make it easy to suspend lines to the edges of the plate with counterweights to partially support it. It doesn't take much half-inch plate to get a little awkward to handle!

My understanding is that 5083 is quite workable with wheeling, and presumably the extra thickness won't make too much difference if I just scale the wheeling machine up proportionately. With a suspension system and a powered wheel I think I can make it all work without breaking too many muscle fibers. I'm getting old and I'm not as strong as I used to be . . . but I AM getting near to having the time to build and go off a sailing! And I've been dreaming of making my own yacht for years now.

Thank you very much for the information!

BillyDoc

[Dagvald]

Hi BillyDoc,

Thanks for telling about the 44 footer. My first thought on the idea of 1/2 bottom plating on a vessel that size is the cost. If your concern is icebergs, why not think about the design of the bow, keel, skeg and rudder to give you the best chance of avoiding damage in the event of a collision. Yes, 1/2" plate is extra weight, twice as much as 1/4" and twice as expensive. Put the weight down in the keel as ballast. Spend money you save on good radar, extra heavy rigging, storm sails, SSB, sextant, charts and a reliable cabin heater!!!

You could put some extra framing in bow area, watertight bulkhead foreward, nicely slope to front of keel and bow. These types of things. Alum is super tough stuff! It'll stretch quite a bit before it lets go, compared to steel. I believe this is called "modulus of elasticity".

A note on welding 1/2" plate: I think you're going to spend three to four times more man hours welding if you try to TIG all those hull seams. Have you done much TIG welding? Man, you are talking a lot of work, electric bill, argon. I spoolgun MIG is the way to go. Use the TIG for tanks, fussy stuff on light gauge that you want to look good to impress the landlubbers. If you are working by yourself how are you going to tack and hold a piece or a tool and push in the TIG filler rod at the same time? There's a way to do it (weld a little pea of filler by the place you want the tack) but that's time consuming and a pain in butt. I could go on but I think you get my point. I love TIG but not when I'm climbing around inside a boat. I recommend 1/4" plate on the hull, 3/8" plate in the bow sections for peace of mind and 3/16" deck and house.

I'd worry more about getting trapped in a floating ice pack than smacking into an ice berg. Where are you planning on building? -Dag

Attached photo SV Setteroses (Seven Roses) I sailed many miles on her with her lovely Captain Laura Zolo although not up north when photo was taken as I hadn't met her yet. She from Scotland, Orkneys, Shetlands, Iceland, Greenland, the Northern Route. Seven Roses is steel hull, an abandoned shipwreck when Laura found her on Cape Verde beach, purchased for one French franc from insurance company.

[BillyDoc]

Hi Dag,

One franc?!!! That has to be the bargain of the century!

The bit about the ice was because I keep wondering what it would be like to give the Northwest Passage a try. And I live in Florida and hate cold weather with a passion! I think I'm losing brain cells at a rapid rate as I age.

I'll be building a building to build the boat in on a tree farm my wife and I own near Pensacola. 160 acres of pine forest with springs and flowing clear water over snow-white sand. We spend most weekends there, and I can really see "camping" out there while building (we have an old Airstream trailer out there for our weekends). The building plans are for a 40' by 60' building with 18' clearance . . . and with heavy steel beams holding the roof up that can be used to hoist and manipulate the hull. I've been TIG welding for seven or eight years now (Miller Syncrowave 350) and I love the quality of the welds you can do with that machine. You are definitely right about the time involved though. My plan is to minimize the "crawling around" part as much as possible by doing most of the interior welding first while standing on the floor reaching between the frames, doing the plating and deck last.

I also really hate to weld upside down, so I plan on being able to rotate the entire hull as needed to avoid this. Lots of strong points overhead and several chain hoists attached to them should facilitate this. I'm also going to go ahead and pay a CNC shop to waterjet-cut just about everything so that I'm basically putting together a “kit” just like I used to do as a kid with plastic models.

I'm very fortunate in that I already have a wide assortment of tools to apply to this project, including a CNC computer-linked milling machine. The only tool I lack is the means to bend those compound curves, and from what you have said I don't think that will be too much of a problem.

Being somewhat demented, I'm actually looking forward to days and months of building! It will be in a very nice environment, peaceful and quiet with nobody to disturb me. Almost like sailing, but with green stuff all around. And watching something come together under my own hands has always been a thrill for me.

As for the cost of the aluminum . . . well yes, it will probably double the way I'm planing to build, but the cost of the material is actually a fairly small part of the overall cost of a good yacht. And besides, I have to be able to show my wife the hull and say “Look at this, Honey, you'll be safe in here! Even if we do get another one of those nasty hurricanes while we're way out at sea.” The point about the hurricanes being one that has been raised . . . often. We had an interesting year in that regard two summers ago. We both also get pretty seasick sometimes, and a heavy boat can be much more comfortable than a light one.

BillyDoc

[Lyle Creffield]

Unfortunately the North West Passage will again be navigatable as it was in 1420 CE due to gloabal warming!

I have researched the time to weld 10 mm 5083 (12.5 = 1/2 inch) plate (Mig), 3 passes, sonic test - work on arround one hour per metre

Eckold machines? who or where?

i once looked at designing a machine which was feed flat plate and pushed out a compound curved plate

[BillyDoc]

Hi Lyle,

I'm actually looking forward to the Northwest Passage . . . for some stupid reason. And I am well aware of the disaster it portends. Oh, well, our species just insists on consistently doing the stupidest things possible, like in this case destroying our collective home for individually selfish reasons.

But you asked about the Eckold machine. It really looks like a fine piece of equipment, but I found a used one for a "mere" $45,000! And I don't have that kind of "spare change" at the moment. You can see what they can do at their web site here: http://www.eckold.ch/umformen/e_um_Homepage.html (I'm referring to the big Kraftformer).

I can't tell just from the pictures, but I'm guessing that the working principle is a very well controlled reciprocating "hammer" with various specialized dies. By this I mean that the force applied with each stroke is very high, but the stroke distance is precisely controlled, and the dies may have built in "tricks" like parts that expand laterally when force is applied (for shrinking or expanding a compound curve). I would really like to learn more about this machine, as I could design something similar fairly easily if it is as I imagine.

Your welding time estimate is very useful as well! I will probably need to double that for TIG . . . which means I'm going to be REALLY OLD before I do any sailing.

What approach were you thinking of for producing compound curves?

BillyDoc

[Lyle Creffield]

Hi Billydoc

Today my aim is hard chine and more sailing time

cheers

[john frater]

Have a look at this site:www.radford-yacht.com/wheel he has plans for a wheeling machine available

[BillyDoc]

Thanks for the link, John. You need to edit it to add .html at the end though.

The pictures of the large "commercial" machine are very interesting. I am becoming more convinced than ever that this is the way to go . . . and building a wheeling machine doesn't look that hard to do at all!

Compared to building a yacht building the machine to use seems downright simple, actually.

BillyDoc

[john frater]

Hi Billy Doc

There is actually a wealth of information on similar machines if you search 'English Wheel' or 'Planishing Wheel' but I think that the one designed by Graham Radford is best suited to boat building. I would be really interested to know how you get on with the machine. I have heard of using very hard rubber compound for one of the wheels to avoid leaving lines in the plate.

John Frater

[jmac]

Graham emailed me the plans for his english wheel. All I did was ask him for some information on it and he sent me a dwg. of the plans.

[BillyDoc]

Hi John,

I've heard about the hard rubber myself, and some people apparently buy large industrial grade castors with urethane treads for this purpose as well. It apparently works quite well!

Hi Jmac,

I understand your surprise. When we watch our "leaders" run through their evil plots, or listen to the constant deluge of scare-garbage from the mass media, it's easy to forget that there are many, many very nice and helpful people out there, and I think you just found one. Good to know and start the New Year with, isn't it.

BillyDoc