Making Flexible Shape Patterns

Metal shaping discussion such as this, from Metal Shaping Master Wray Schelin can be reviewed online at the MetalMeet Forum.

From: By Wray E Schelin Date: Fri Apr 28, 2000 6:17 am Subject: new quick paper shape pattern method

Ok as promised here are a series of pictures that I took today when I made a paper shape pattern of a XK Jaguar headlight pod. This improved and new method I have been searching for quite some time now. If you make plain paper patterns, they are a real pain to get them to lay down nice on the part or shape that you are copying. Magnets to hold the paper down are of no use when working with aluminum, and they do a poor job even with steel. I tried many different methods, but nothing is as quick , cheap, and easy as this.

Last summer Jonathan Clowes ( a sculptor from NH) called me and asked if I would help him in building an aluminum sculpture. In the process of working with him I explained the problems and drawbacks of the plain paper shape patterns. The next time he came to my shop he showed me the solution to the problem. He and his helper ( Mark Goodenough) have extensive molding knowledge,having worked previously together on many sculpture projects made of fiberglass. They came up with the idea you see here of using a special tape that is used by lettering companies today called transfer tape. The neat feature of this tape is that it has a diminished stickiness to it very similar to Post It notes. It looks like thin masking tape and comes in 4' long logs that you have the supplier cut to the widths that you desire. The cost is about $70.00 for a four foot log and any sign painters or lettering supply house will have it available. It is used to transfer vinyl letters off of the sheet they are cut from and then transfers the letters to the surface ( truck door etc.)

The two pictures you see below are two views of the headlight pod and the tape.

pod1.jpg pod2.jpg
pod3.jpg The third picture is of the pod covered with the transfer tape alone.
The fourth picture is of the reinforcement tape used over the transfer tape. The reinforcement tape is fiberglass lined shipping tape ( very strong). On this pattern I chose to completely cover the transfer tape . pod4.jpg
pod5.jpg The fifth picture is of the shape pattern peeled off of the pod. This must be done carefully, making sure that the transfer tape stays stuck to the fiberglass shipping tape. After the pattern is off you then dust it with plaster to kill the stickiness on the inside.
The last picture is of the shape pattern laying on the bench with the edges held down with magnets. You can see from this picture that the interior of the shape needs about two inches of stretch and the outer edges need lots of stretching. pod6.jpg

If you follow the patterns information you will have the pod. You will be able to work the metal in the folded open position, which allows you access. Working a panel out of shape is one of the fundamental "secrets or tricks of the trade".


A Reader Questions Wray

>>>>The last picture is of the shape pattern laying on the bench with the edges held down with magnets. You can see from this picture that the interior of the shape needs about two inches of stretch and the outer edges need lots of stretching.<<<<


Thanks Wray. I think I follow everything up to this point. What I don't understand is how you "see" where stretch is needed. What indicates this?

And, could you elaborate on the following paragraph a little more please?

>If you follow the patterns information you will have the pod. You will be able to work the metal in the folded open position, which allows you access. Working a panel out of shape is one of the fundamental "secrets or tricks of the trade".<

Also, I just thought of a material that I used back when I was a technical illustrator. It is called frisket paper. the spelling is probably wrong -- but it's close. This is a somewhat clear paper with an adhesive back. It is used to place over a photo or illustration so you can cut out an area to be airbrushed. It is quite expensive -- but might come in handy.

Wray Answers:

After you have the shape pattern made, you then flatten it out on top of a piece of sheet metal . You then cut out the sheet metal following the flattened pattern as your guide, leave at least 1" extra all around the perimeter . unflatten the pattern ( sort of let it fill with air). the metal will still be flat on the bench, it must grow ( stretch) to fit the pattern. if you have a power hammer , you go over and wail the metal with it , if you have a beater bag, you have to wail the hell out of the metal . you have now begun the growing process ( the early stages of metalshaping are not pretty, lots of lumps and bumps) . After wailing on the panel for a few minutes check the pattern again, you will notice that the patterns fit to the metal has improved. Some areas will still need extra "growing" so you concentrate whacking the hell out of them showing then you mean business. Check the pattern to the panel again...hhmmm , it's fitting better and better. You might at this point smooth out some of the lumps to better assess the pattern to shape fit. You can do this by running it through the English wheel or the planishing hammer ( if you have used a power hammer to get to this point you won't have to do this because the panel will already be smooth). After smoothing out the lumps and bumps you will notice that the panel has shrunk a little ( it really hasn't the lumps just gave you a false reading). So then you go and beat the panel up a little more, or if your a real patient type you can finish raising the panel on the wheel or the planishing hammer.

I usually raise the panel to 90-95% of it's finished shape by bashing, then I planish it on my wheel to a finished fit for the last 5-10% of the shape.

In the example of my headlight pod the edges need lots of very concentrated stretching I do this concentrated edge stretching in my Erco shrinker/stretcher, but you can also do this with a narrow headed body hammer, holding the metal tight against an anvil or other heavy hard block of steel.


Reader Questions:

> Also, I just thought of a material that I used back when I was a technical illustrator. It is called frisket paper. the spelling is probably wrong -- but it's close. This is a somewhat clear paper with an adhesive back. It is used to place over a photo or illustration so you can cut out an area to be airbrushed. It is quite expensive -- but might come in handy.

Wray Answers:

I'm not sure of frisket paper I am sure of the lettering transfer tape, give it a try. I've tried many different combinations and formulas, I have yet to find one as good as the transfer tape.

Desirable characteristics of the transfer tape.

1 -inexpensive
2- easy to get
3 -very thin
4 -extremely strong when reinforced with the fiberglass shipping tape
5 -reversible
6 -long shelf life
7 -easy to do
8 -quick very accurate results
9 -peels easy because of its reduced stickiness
10 -doesn't shrink

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