Forming compound curves in heavy aluminum plate

[Lyle Creffield]

Hi Billy doc

i seconded your comments that there are many helpful persons who use boatdesign net

research shows that a little help to understand something goes a long way in the learning process

thank you to all those highly tolerent persons for their most imformative responses

lyle

[lazeyjack]

Originally Posted by 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?

you cant wheel to the edge of a plate, allow 60--75 mm in topsides first run you can use most of the plate as there is lil shape, but anywhere else alow that much see my gallery
Eckold squeeze recipricating presses have ltd .use and are two man operation, you can form pretty much all using small v wheels, once gain see the nose in my gallery Up to 8mm with not excessive shape you can use urethane wheels leave sno marks but then the marks are all inside except on a clipper bow when the forming is other way

[lazeyjack]

and anyone who heats a plate is an amatuer, you NEVER heat alloy, ever. it is possibel to form a plate so close to the desgned shape that only light pressure is necessary to bring it home

[BillyDoc]

Lazyjack,

Thanks for the info. I've pretty much settled on a bloody great wheel with a hydraulic drive so I can control it easily, and not use my own muscles for power. I know it seems crazy, but I have become convinced that half-inch plate is the way to go.

Here are some reasons:

Heavy aluminum plate is much less subject to heat distortion during assembly.

Given that the density of aluminum is roughly 34% of steel, the equivalent steel plate to half-inch aluminum (by weight) would be 0.172 inches thick, which is not unreasonable for the hull of a steel boat of similar length. The aluminum is much stronger though.

Butt welds have much more area, so are stronger (assuming a complete fill, which is easy enough if you first saw out the area right through to just short of the other side)

I will be using frames every 18 inches, longitudinals every 12 inches, so individual plates will not be too large to handle.

Expense aside, my very limited experience is that heavy plate is actually much easier to handle for a project like this than the light stuff. And besides, I want a real brute of a boat. The preliminary calculations for my half-inch thick hull give me a hull weight of 5,404 lbs, which doesn't seem too unreasonable for a 44 foot hull. I don't care about speed, I want seaworthiness above all other qualities.

The downside of a heavy hull is certainly welding time and supplies and initial material cost, which in this case will add roughly $7,500 compared to quarter-inch plate. But I don't see any other downside at all! That is, assuming proper equipment to handle that plate starting out, which I intend to have.

BillyDoc

[lazeyjack]

well wait and see, you are a stubborn bugger, If I was building a rocket I would listen to you,
no one asked you to build in 6, 8 is ok, have you ANY idea how hard it will be to stretch that 13 plate ? you have to stretch before you even start to form, the stretch in the centre of the plate, makes it go AROUND LENGTHWISE, the forming makes it go around bodywise Do you still have the draft of my book?
It should give the wheel speed in ft per minute Best is a planetary gear, driven by a fractional hp elec motor with a chain driving the wheel, pressure is applied through a screw Still what do i know I only personally built 32 alloy boats, If you think I,m getting cross you are right Stubborn bugger!!)

[BillyDoc]

I hear you Lazyjack, and your words have made me very cautious about whether or not it is possible to form plate this thick! So, I'm going to build the wheel and try it before proceeding with the boat plans. That way I'll know for sure. I certainly prefer to go with the heavy stuff, but if it can't be done . . . then I guess it can't be done!

And If I put together an oversized wheel and find I still can't work half-inch plate . . . I bet it will work the thinner stuff just fine!

Thanks for the info! I really appreciate your experience and input.

BillyDoc

[lazeyjack]

Originally Posted by BillyDoc

I hear you Lazyjack, and your words have made me very cautious about whether or not it is possible to form plate this thick! So, I'm going to build the wheel and try it before proceeding with the boat plans. That way I'll know for sure. I certainly prefer to go with the heavy stuff, but if it can't be done . . . then I guess it can't be done!

And If I put together an oversized wheel and find I still can't work half-inch plate . . . I bet it will work the thinner stuff just fine!

Thanks for the info! I really appreciate your experience and input.

BillyDoc

ok, normally on the top run would start anything from 4 foot wide pl at bow and finish maybe .9m or 36 in at transom
second run narrower and and tapering maybe to 20 inches at transom
because you a re doubled ended, your plates are going to get very narrow at stern, your trim waste will be 40% = of the pl width here, as you will need that extra width that you cant wheell
You will make a pattern at every frame. for every plate you may have 10 by your side by the wheel as you work, the plate must fit that pattern exactly right out to the end of the pattern which will look like a slice of new moon
its not so crucial in flatter areas BUT any boat with shape, needs wheeling no matter how small the curve, because if you force the plate, when you weld it, it collapses in that area, Of coarse there is an alternative, BOG, thick red microballons,
you see that default hull in delft? well look at the grey lines in the body and that is something like your plate scheme would be Except the line would drop at the bow , in other words the top run at bow is the widest plate nearer the time I will draw your plate plan for you

[lazeyjack]

oh I did not say it was impossible , I said becuz your yacht is short and with much compound, it would be very very difficult If you look at that keel in my gallery(which I did not build) you will see anything is possible with skill, they built a very complex press for this, and the plate was THICK

[BillyDoc]

Lazeyjack, The nose of the Millennium 55 in your gallery . . . how thick is that? Looks like it was a pure bitch to do!

[lazeyjack]

no it was fun, took 5 hrs, we layed the machine down, I built littel former wheel, and a girlfriend worked the fwd reverse switch, I had a pattern for every waterline
was 6mm, and boy once its formed it as strong as a pipe, the the painters bogged all over it!!(

[lazeyjack]

very slender up there and I welded permanent backing bars to the inside of the nose edge cos there was no room from inside to get to it. At the forefoot, 8mm, is so strong 5083 that once formed you can not move it with a 15 lb hammer, this is why I cant get to grips with the 13 pl idea

[lazeyjack]

this is the best (fairest yacht) I have ever seen, built in Holland , unpainted there is some sort of preservative sprayed on the plate, the owner tell me she is built over frames only In that case it is quite exceptional, all weld penetrations have been removed and , well it just impresses so much.
the house is timber as is the deck, joined at the deck edge , timber is bolted to a shelf which runs around the sheer,
i have built same principle but used alloy deck and joined the house to it , by screwing to the flange the boat is in Mooloolaba at mo, on world cruise

[SkipperSki]

You might want to check out, Grizzly Industrial, Inc. their catalog is free.
www.grizzly.com

Every Metal or Woodworking Shop, should have this catalog on the book shelf.
If you go to the web site, enter in the following model #'s

Casters; H0655
English Wheel; G0496
Planishing Hammer; G0497
(while both these are for light gage (16 ga.) mild steel) and would be suited for lighter metal boat builder, but give you an idea of each form.

I hope this is useful info !

[BillyDoc]

SkipperSki,

Thanks for the link! I've got it bookmarked.

BillyDoc

[Lyle Creffield]

Hi BillyDoc

12mm is thicker than most
Firstly, i am not a naval architect
But I am a strong believer in thick skinned ally for 12m plus sailing vessels
One of the more capable Australia designers Graham Radford who trained under David Adams said to me when discussing his Radford 14 #47 that the first boat that was built had a 6mm hull - he described this as "very strong" considering the overall design
For practical purposes i consider 8, 10, 12mm as thick in comparison to the excepted norm
Advantages: Most can weld to and join such plate without distortion, corrosion will always be an issue but with thick plate it can be reliable repaired, and last a very long time

Here i would like to clarify my design parameters if you will so allow

Blue water-ocean going vessel, that will remain water tight providing there is keel to ground clearance, a hull that has the highest resale value by way of an almost indefinite lifetime (we only think we build for ourselves), and ease of construction - too many hulls never get completed primarily because of the excessive hours caused by construction design, fit out is a big job in itself

I am guessing we are on similar paths save that i intend to mass produce after the my prototype is completed

Can 12mm plate be bent (compound curvature i assume)to your design without such deformation as to cause lost of strength and possible corrosion problems (from external radius stretch) as to defeat the original aim of strength and resistance to corrosion?

Life is about balance and so to is vessel design (most call it compromise)

I believe that parking a 10mm hull on a reef would have similar consequences to doing so with a 12mm both would likely survive with some dents and scratches why do 12mm when 10mm may do?
A similar argument could be raised for 8mm but not 6mm in my view

I have long had an idea (and many sketches) of a large multi wheeled machine computer driven that can feed 6m by 2.4m plates back and forth to arrive a a desired compound curvature and once trimmed become part of a section of preformed hull - but have not located the entrepreneurial capital required

So without such a machine 12mm plate and tight compound curvature will be very time consuming or ... consider single chine, frameless initial construction, then fit frames, upright construction, estimate hull construction less keel, rudder and skeg of less than 400hrs, arround 1000hrs is more often the norm - food for thought?

I have built a 1.5m model of my CREF15, 15m LOA, 15t, 4.2m beam, hope to build a 3m 1/2 hull over Christmas before having the design checked by a naval architect and NC file produced


good luck and best wishes