To make a pattern or use original piece

[Matt Harwood]

Hi guys,

Holy cow there's a lot to see here! I've been reading for a few weeks and this is my first post. I'm restoring a 1941 Buick Century sedanette, and the right rear wheelhousing is pretty well cooked, as you can see in the photos below.

http://www.harwoodperformance.bizland.com/1941buick/Inner_Trunk_56.jpg
This is the fender from inside the trunk. Note all the rust perforation.

http://www.harwoodperformance.bizland.com/1941buick/Inner_Fender_32.jpg
Here's the inner fender from the outside.

The red area is part of the body that folds down over the inner panel. It has a lot of perforation in it and will be replaced (you can see where I've marked my cut line with black marker). The blue area is where the inner panel (same as in the first photo above with the arrows) will be cut out and replaced.

My plan is to lay a piece of posterboard over the removed wheelhousing and smooth it out, then cut it around the edges. Then I'll flatten the piece on my 18-gauge sheetmetal, trace it, cut it out, and start hammering it with my poly hammer and bag. Is this the proper way to do this, or should I use the tape method I've been reading about to maintain some of the curvature of the panel? Should the cut-out panel be smaller than the original because it's going to get stretched (or will it just be slightly bent?)?

I don't have an English wheel to really get it flat and smooth, however--will that be a problem? I've already replaced a lot of floor pieces, which were admittedly smaller and flatter, so I'm hoping to expand my skills somewhat with this project.

Wow, so much to ask, so much to learn, so much to know! Any advice is greatly appreciated. I'll keep you posted on my progress!

Thanks!

[Randy Ferguson]

Hi Matt,
It's good to see you posting here. It just a few weeks until MetalMeet. Would you be able to get away, even for a couple days to attend? If so, you could bring your panel with you and we'll help you get the replacement made.

Here's the rundown on one way I would go about replacing your panel. Before doing any cutting, make a good flexible shape pattern, following the directions you've found here on metalmeet.com. Before removing the shape pattern from the original panel, make a set of good profile gages to follow after the new panel has been shaped to fit the pattern. This is important to do before any cutting to insure that all information is correct. I would use strips of metal, 3/4-1" wide and use a stretcher/shrinker outfit to make the contour gages. If you search the site, you should find a picture of some contour gages. If not, let me know and I'll post a picture for you. Once you have made gages for the perimeter of the area you intend to cut out, and a few spots through the center region of the panel, (about 6" increments works well) while indexing each one for future reference. To index it properly, you need to draw a line with a Sharpie right along the edge of the profile gages. Number the profile gage and the corresponding line on the shape pattern. All the information you gather at this point, will make the job go much easier and faster later on. You may then pull the shape pattern from the original panel. By the way, I didn't mention this earlier, but I would make the pattern and gages from the trunk side, as it will be easier for you to read what the pattern is telling you.
You may also use a piece of paper to make a pattern, just as you described and this will lay out flat on the metal and give you a god idea of where and how deep to start your tucks. You lay the paper on the panel and cut the paper so that it lays fairly tight against it. You will have to make some slits in it with a razor knife, or make some folds in the paper pattern to make it fit the panel but I think the slits work fine. After you've done all this, you are ready to lay out the metal. Using your paper pattern, lay it out flat and mark 1" outside the perimeter of the pattern, or more if you need it to make up for flanges, etc. Just make sure you cut the metal larger than you need it. It's much easier to cut the excess away later, than to have to add to it!. Once you have the blank cut, you can determine from your paper pattern where you will need to add some tucks and start shrinking the edge. The slits you made in the paper pattern will show you approximately how deep to go with the tucking tool. The flexible shape patterns is actually all I would probably use, but for your first attempts, the paper pattern, coupled with the shape pattern is your safest bet.
You can now begin the shaping phase by putting a few tucks in the proper area and shrinking the edge some. A couple series of tuck shrinking will start putting the panel into shape. You can then start banging away on the center of the panel to stretch it a bit. Using your flexible shape pattern, you will soon start seeing progress. Once the flexible shape pattern starts fitting the new panel nice and tight, you will want to punch some 1/4"-5/16" holes in the shape pattern, centered over the lines you placed for the contour gages. Put these holes every few inches 4-6" will be fine. Now place the shape pattern over the panel, leaving at least 1" of metal around the edges. Take your Sharpie and mark the metal through the holes, making sure the pattern doesn't slip, as this will flaw your information. Once you have marked the panel through each hole, you can continue the shaping process. At this point, you may feel that the panel is getting really tight and in need of planishing. If you had an english wheel, this would take just a few seconds. since you don't you will need a slapper and dolly ( A post dolly would be best) and start smoothing (planishing) the panel out. As it becomes smoother, it will relax and become easy to work once again. After you have gotten it relatively smooth, you can lay the shape pattern back on, lining up the dots with the holes. (This is very important, as the slightest mis-alignment will give you a false reading) It should be getting relatively close by this point and tiny steps will bring it right around. Learning to read the flexible shaper pattern is the key to success here. That information should be posted somewhere, so a search on flexible shape patterns should turn up all the info you need. When you have all the necessary area change (shape) introduced to the panel, you can move on to using the contour gages to properly arrange (form) the panel so that it will fit in the desired configuration. You will now do any more stretching or shrinking at this point, and although it may want to resist your actions slightly, it will go where it needs to be.
You just have to be patient.

Hope this help, and if you need more help, just say so.

[Richard K]

Randy,

Great explanation of the process. I never quite understood the hole punching. You cleared it up. Input such as yours is a blessing to us all.

[Matt Harwood]

Um, wow!

Thanks for the extremely detailed information, Randy. I may give it a try this weekend and see what happens. I have a lot of sheet metal to practice on, so I won't get too bummed if the first try isn't perfect. I know there's a lot to learn and also that the best way to learn is to actually do it. Now that I have a great procedure to follow, all I need to do is teach my hands how to do it...

I wish I could make the Metal Meet this year, but it will unfortunatly conflict with my job's trade show schedule, and since I'm charge of trade shows... I'll get there eventually, I promise! I'm already looking at designs and thinking about building an English wheel--I'm hooked!

Thanks again and we'll see what happens!