fixing an oil canned hood

[WagonCrazy]

Here's the hood i'm starting with (for my 57 Nomad). It's been thru a carb fire at one point, and has oil canning in the center.

https://youtu.be/dMHMtEs31iQ

Been watching youtube videos on how to fix oil canning, by basically heating with a torch, then rapid cooling. Seems to bring back stiffness.

Any clues from you guys before I start this process?

[Rick_L]

A couple of comments while we wait for the master, MP&C, to step in.

1. You don't need rapid cooling to shrink with a torch, the heating only will shrink a stretched area. The only effect that rapid cooling will have is it will let you see your results faster.

2. That said, I don't think I'd be doing this one with a torch. It heats too big a spot at a time, and it's imprecise. I think I'd attack it with a shrink attachment on a stud gun. I'd draw a grid of where I'd apply the shrink attachment, maybe on a 2" grid.

That said, I'll stand aside for some thoughts and comments and hopefully Robert will chime in soon.

[Custer55]

If the oil canning was caused by the carb fire that spot on the hood may have shrinkage already. Maybe just needs some hammer and dolly work.
Robert would be the one who should know what to do with it.

[MP&C]

First, let's add the reference material here so you can have it in one place...




Before I suggest to someone how to fix an oil can, it is best to find out what kind of oil can you are dealing with, first and foremost.
I consider there are two kinds, a tight oil can and a loose oil can, each will require a different method of repair.

Tight oil can

This is almost exclusively caused by body damage, whether a dent, glancing crease, or media blast damage, and is especially noted by displaced metal that will oil can when considerable pressure is applied, and may or may not forcibly spring back. When the body damage occurs, it stretches the panel throughout the dent or crease. A typical dent, whether straight in or a glancing blow, will have direct and indirect damage. The direct damage goes inward, stretching the panel as it goes. The indirect damage, is a much lesser amount of spring-back, compounded by the internal stretch pushing outward circumferentially, and you will see an outward bulge around the perimeter of the dent/damage. Although the initial inclination may be to shrink this outward bulge, for the most part this adjacent area is relatively damage free, it is mainly being spread outward by the stretch forcing outward.

Shrinking the center damage will start the process of relieving the stresses pushing outward, relaxing some of the bulge surrounding the dent.
After a bit of shrinking, using the shot bag against the outside of the crease/dent and some light taps with a flat body hammer or slapper from the inside will help to start manipulating the crease/dent back into it's original place. I would add that too much shrinking all at once may give you the loose oil can, so profile templates are highly recommended as they work well to let you see how the panel is reacting so you don't go too far too quick.

Tight oil can, part two

Where some tight oil cans from dents may be challenging to determine where to start your shrinking (if it doesn't have an obvious sharp crease to show where to work from) the following process will normally find the area that needs shrinking.... Cycle the oil can in and out a couple times in order to find the outer perimeter. If it helps to mark it with some painters tape, a sharpie, so be it, use whatever works. Now using your thumb from one hand apply slight pressure on a point on this perimeter. Use the other hand to cycle the oil can again, using the same pressure as before. Keep moving your pressure point around the perimeter and cycle the oil can for each spot until you get to a point on the perimeter where the pressure will keep the oil can from cycling, it locks it from moving. This should identify your sweet spot that needs shrinking, and be aware that there may be more than one sweet spot needing attention.

Loose oil can

This is typically caused by welding, over-eager torch shrinking, or shrinking something when you should have stretched, (or fatigue over the many years that has caused a larger panel/hood to settle). Any panel will shrink from heat, causing the crown to draw in from the surrounding area. This is especially noted by a loose, easily flopped back and forth oil can. This is fixed by stretching, typically in the area of the weld and HAZ.

Loose oil can part two

In some cases we'll see that a dent (or tight oil can) has actually caused a loose oil can in the outer reaches in the adjacent area. The direct force
(dent) may have caused displacement of the inherent stresses of the panel (crown) such that it pulled at the adjacent metal elsewhere, resulting in a loose oil can outside the area of the dent. Here the loose oil can should be left alone and focus on removing the stretched area (dent) that moved the panel. Once the dent is removed, this action alone should correct the loose oil can in the adjacent area.




Now, with that done, the lack of paint suggests where the damage occurred, the heat from a fire would have shrunk the metal in the area of the surface rust. PAY NO ATTENTION TO THE OIL CAN IN THE FRONT!!!! That is secondary to a shrink at the rear pulling low and pulling that down as well. When you get the back fixed, it should fix the front.

IN your video, the initial push you did showed an oil can affected the surface rust area and nothing else. Try to focus on that, see if you can cycle that from the center of the damage where you should be able to see the outer perimeter of the oil can... the part of the sheet metal that cycles inward and then outward. Although what I'm going to suggest is normally used on stretched oil cans, try it to see if it points to an area to address first. This means it may or may not work. If it doesn't report back.

Look at the instruction under "tight oil can part 2" above. In it you find the outer perimeter of the oil can and apply thumb pressure on a spot (any spot) on that outer perimeter. (perimeter does not mean it has to be round) With pressure applied, cycle the oil can again. Move pressure point, cycle again. Repeat until you have gone all the way around the perimeter. You are looking for any and ALL areas where thumb pressure either locks the oil can from cycling or decreases it's amplitude. If you find any such locks, mark them and continue around the entire perimeter. IF this method works and does show any such spots, I would start by planishing the areas that completely locked the cycling first, and any that decreased amplitude next. I would suggest that the locks would need more planishing than the "limits". Also, don't think that the first round of ANYTHING in addressing oil cans is an immediate fix. You may go through many evolutions of this to get things back where they should be.

Disclaimer: Don't get overzealous and beat the shit out of the hood, even though it may look bad now, it doesn't take that much planishing to overcome the effects of shrinking. too much in one place and you'll have a nice pucker sticking up... Also, some profile templates (side to side, front to back) from a good hood would help to read what you have, and let you see sooner that perhaps you're using too much force.. The video is your friend, take more as you go...

[Rick_L]

Excellent point on the fact that the original damage shrunk the metal, didn't stretch it.

[WagonCrazy]

This afternoon I removed the paint from the front.
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And based on the amount of rust on the back, I'm considering cutting out all the underbracing (removing spot welds) so that I can media blast everything and put a coat of epoxy paint on it.
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But before that, I'll do another video of the oil can spot so you can confirm that I have a loose oil can situation here. Thanks Robert.

[MP&C]

That bottom view shows where most of your heat took place, and where most of the shrinking occurred. I would almost work the oil can before media blasting so you don't lose track of exactly where the damage occurred. Removing the brace will definitely give you more room to work.

[WagonCrazy]

Today I managed to get the inner brace removed (spot welds drilled) and started to media blast the brace. It's slow going with a little pot blaster outside. Have to keep scooping up the media, sifting it, and reloading it. Its just so friggin' s_l_o_w....

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Here is the backside of the brace (sits against the inner hood). Think it needs a little clean up and epoxy primer?

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Tomorrow I hope to finish the media blasting and then go after that hood oil-can with some heat...

Robert, should I heat the bottom side? (right where the previous carb fire occured) OR heat from the top side?

The hood only flexes when I push down on it (from the top), and oil cans right back into position when I release the pressure. There are no obvious dents or creases in the hood. It's just weak right there in the middle.

[MP&C]

Heat is what caused the problem to begin with. Not sure what you're reading that tells you to heat it more, but believe me, you have quite enough shrinking that has taken place, you don't need more...

[Rick_L]

WagonCrazy, you need to read Robert's initial reply very carefully again. No heat yet.

[WagonCrazy]

OK, so no more heat. Go with Planishing... I don't have a pneumatic planisher. So will try this by hand with hammer & dolly I guess. But before I do that, I'll try to get another video moving my thumb around and pressing with the other hand to determine the perimeter. Following Roberts advice on Tight Oil Can- part 2 from above. Stand by for that maybe by tomorrow afternoon. Thanks guys. :)

[WagonCrazy]

Here's a video of the hood all stripped down, with the braces removed.
Where do I start planishing?
(there are no obvious dents...the profile is OK as is now...just oil cans when putting pressure all over the center...

https://youtu.be/FtcRtJ4RB6c

[WagonCrazy]

So its these 2 videos that have me thinking about applying heat before lightly planishing...
Are these guys full of it?

https://www.youtube.com/watch?v=K5MVVnsERqc

https://www.youtube.com/watch?v=DU5jfu7uals

[MP&C]

The big difference between yours and those two videos.... yours flops easily, a LOOSE oil can. Both of those videos show a very tight oil can, likely cause by body damage or someone getting too happy with a hammer and dolly.


Heat is what caused your issues.. Why on earth would more heat be the fix? It will cause it to shrink even more, make it more floppy.


So when you are pressing around the circumference of the oil can, you are doing the entire hood. You have more than one oil can, one should be the perimeter of the heat mark, the other (front) is secondary to that, so leave the front alone for now. Basically the shrinking above the carb fire has pulled the crown of the hood downward, and this disrupted the crown front to back on the hood that supports the entire hood. Leave the front alone. Focus on the oil can in the back of the hood.

[Rick_L]

Echo what Robert said about heat causing the oil can, and not to heat it in an attempt to fix it.

Also, in the first video, the idiot took a pick hammer to the spot that was heated. This created new damage. And again the use of wet rags or air won't affect the results when you use heat. All it does is it lets you inspect the area sooner to see if you made progress.

[MP&C]

At 50 seconds is the only area you should be concerned with. Find the perimeter of that oil can alone. Then thumb pressure around the perimeter while cycling the EXACT CENTER of that oil can so we can see what occurs.

[WagonCrazy]

Take a look at this video. I'm having trouble determining the exact place to start the planishing. The oil can area is large...

https://youtu.be/D7KZX-brbro

[MP&C]

So looking at what you are doing and the reaction, it does not appear this "trick" works on a loose oil can. Sorry for the runaround, but it's not often you run across a loose oil can to try it out. To clarify though, the center of the oil can should be the center of where that heat mark is located. When you cycle the oil can, that means push in and out on the exact center of the oil can. And stay there. All of the cycling is done on that one oil can AT THE CENTER. The pressure is applied on the perimeter, and cycling the oil can never changes location, only the pressure point on the outer perimeter does. Oh well, practice for you for a tight oil can.

Now, if you still have the heat spot location on the bottom side visible, the spot that we were looking at needing planishing is where the paint was burned off. But this has me worried:



The oil can area is large...


Get that front area out of your mind, it does not need anything done to it. The ONLY area you should be touching should be where the paint burned off underneath, maybe about an inch more outside of that, but then only if profile templates show it as low..

So what do you have in body hammers, anything with slight crown, like the face on this one?


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[WagonCrazy]

A bit embarrased to say my bodyworking hammer selection is nearly non existent. I have one round & square - flat metalworking hammer, and the others are ball peen type hammers, framing hammers, finish hammers, etc. Nothing that is as rounded as the one you showed. I may be needing one though, eh?

[MP&C]

Do you have a dolly with a similar crown that matches the underside of the hood without the perimeter of the dolly touching ?

[WagonCrazy]

Yes I do. I'll snap a pic of those in the morning and post. Thank you Robert.

[WagonCrazy]

Here's my arsenal of metal banging tools.
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And here's a couple of pics of the hood (with no back bracing...just the sheet metal) sitting in the hole. (sorry...all these pics get rotated 90 degrees and I can't figure out why)

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[MP&C]

So you will need something that closely matches the crown from the underside. I'd suggest that toe dolly on the bottom. Make sure it's close and that the outer perimeter of the dolly doesn't touch.. Otherwise you will be leaving marks that you don't need. And you'll need a flat large faced body hammer or a spoon/slapper that is near flat. Fucks sake, an Estwing? We're not building a shed here.. :D

[markm]

I have seen quite a few decent 57 hoods at swap meets reasonable, afraid I would end up going that route.

[WagonCrazy]

Fucks sake, an Estwing? We're not building a shed here.

Bwa ha ha :D I put that one in there for humor and it apparently worked. ;)

I'll pick up a flat bodyworking hammer today and work this thing over a bit later. I might also make a cardboard template of several areas of existing profile, so that I have that for a baseline to compare.

Thanks Robert.

[MP&C]

I would start only addressing the area that was scorched from the underside. Try to get the dolly-on PING sound when you are striking. I would do a grid or pattern within the scorched area about an inch apart, work the entire area and see the results. If it needs more, offset your strike pattern 1/2” so tou’ll Strike fresh spots, and then reassess. With each successive pattern planishing effort you should start to see the area become less floppy.

[WagonCrazy]

Its working. Still in process though. I'll post more later. Thank you!

[MP&C]

And leave the front alone!! :p

[WagonCrazy]

So I managed to get the driver side area to stiffen up by planishing it (That was the side with the carb fire). And I left the front alone, and it's stiffened up.
But Im having a challenge getting the rear passenger side to stiffen up with all the planishing I've done there too. Check this out...what should i be doing next?
Keep lightly planishing there? It does feel like its stiffed up ever-so-slightly since I started, but I've hammered 2x more on that passenger side without the same result as 1x on the driver side.


https://youtu.be/T06rDnmiQnU

[MP&C]

Have you used a profile template or 3’ ruler or ?? To see how the front to back looks? Is the spot you planished a high spot now, is it a gradual crown front to back as it should be? Now check the loose area the same way. Now check across, left to right in various positions to see if that loose area is dropped any. More importantly, was the “center” planished too much that it’s pulling the low? So the trick with a 3’ ruler is to lay it over at about 45 to 60 degrees so it will tend to follow the contour. If you don’t have one, a 1” wide x 1/16 thick piece of aluminum 3 or 4 foot long from the hardware store serves as a good straight edge and will likely be cheaper than any metal ruler the same length. Use that to see how the panel looks, have a light set up behind so you can look for what light shines through

[WagonCrazy]

Let's go thru your questions one at a time:


Have you used a profile template or 3’ ruler or ?? To see how the front to back looks?
Yes, I have a metal 3' ruler that I'm using in the video below.


Is the spot you planished a high spot now, is it a gradual crown front to back as it should be?
Drivers side...It doesnt' appear to be high. It DOES appear to be a gradual crown from front to back as it should be.
The very center of the hood is now strong (no flexing when pushing) and (using the ruler) it appears to be the same gradual crown from front to back as the driver side (see video below)


Now check the loose area the same way.
The loose area (passenger side of hood) is slightly lower. It doesn't have as much crown as the center or drivers side does.


Now check across, left to right in various positions to see if that loose area is dropped any.
Loose area (passenger side) is definately down a bit (lower than the driver side area)


More importantly, was the “center” planished too much that it’s pulling the low?
I havent planished the center at all. only the driver and passenger sides in about a 8 inch diameter area (each) where the carb fire would have occurred.

Take a look at the video below and tell me if I should be planishing in the center next...to spread the steel towards the passenger side (to tighten that up more)?


https://youtu.be/rR0ztmq93bA

[MP&C]

On your ruler, if you lay it over flatter (not on the edge) at about a 45* angle, it will lay down naturally to follow the contour of the hood. With it in this position you can better determine high spots or low spots, over using the "rolling arc" technique. Then, you'll need to do this same "lay it over" in the side to side orientation at various locations, I'd suggest 6" increments. If it is low on the passenger side, stretching the middle won't fix it. Can you do the ruler test again, laying it over?

[WagonCrazy]

Lets try this again...

Overall, the contour is within 1/16 inch of where it should be, but there's just such an obvious soft spot on the passenger side. How to stiffen this?

I laid the straightedge over flat as you described in your last post. But I dont' have a short enough straightedge to do the side to side lay-flat test.

Take a look:


https://youtu.be/XxKXfK8Guoc

[MP&C]

To clarify...



On your ruler, if you lay it over flatter (not on the edge) at about a 45* angle


You've gone from one extreme to the other. Up on edge will not match the profile of the crown, laying flat does not support the ruler, so it will fall into the low spots and not show them effectively. At a 45* angle, the ruler has some support and will follow the profile of the hood.


Now, before doing anything else, we need to check left to right, Drivers side to passenger, whatever you'd like to call it. I understand your ruler will not fit between the bullet "tunnels?" but go to your nearby hardware store and get a piece of 1" x 1/16" x 4' aluminum flat bar. Before buying, sight the length just like you're buying 2x4 lumber, make sure nobody has bent it. You need it perfectly straight. When you get home, cut it to fit between the bullets, and check the profile left to right. Start at the back of the hood, LAY IT OVER ON A 45* ANGLE, and check for light shining under, indicating a low spot. Come towards the front of the hood every 6" and re-check.....

[WagonCrazy]

Gonna have to get a shorter straight edge, and gonna have to have my wife hold the camera (closer) while I do the 45 degree slide trick across the hood with the straight edges.
Got to see if Lowes or Home Depot has the straightedge material. Back at ya later today. Thanks Robert (for your patience). I'm intriqued to see if I can get this flexing gone.

[WagonCrazy]

Try this one...


https://youtu.be/JLArdyiRSbY

[MP&C]

OK, how about another video... This time take your right hand and move it all the way to the right end. Where you have your hand does tend to push down, so LIGHTLY holding it down on the end should show a more accurate reading of where and how much the low is... Next, move the light to the far end of the hood so the light coming through the gap is more visible (if this doesn't blind the camera)

[WagonCrazy]

Try this...

Almost seems slightly high right down the center, but definately lower on the passenger side as we slid the straightedge towards the back of the hood...


https://youtu.be/wTkrW2TJraM

[MP&C]

Looks like it's low on both sides, or perhaps center it stretched too much. Go back to the front to back orientation with your ruler and check the center for any low areas. If that looks ok, I'd say leave the center front to back alone. I have a feeling it's good based on how well it got rid of most of the oil can.


In your latest video, if that is light I'm seeing on drivers side as well, you may need to stretch both sides, but using a more open grid as you won't need that much. It doesn't have the focused shrinking like what the carb fire produced. I'd use about a 2" grid and see where that leads you. Don't focus on any one area lest it produce an isolated bulge. Keep your planishing here moderate to light so you can SNEAK UP on the proper crown. If it needs more, offset an inch to planish new metal. Keep checking as you just did using ruler at 45* angle, side to side as well as front to back to verify where any lows remain.

Having the light toward the front but hanging up and aimed downward may help eliminate blinding you.. With the ruler leaned toward you (the direction you are standing) the ruler will cast a shadow so any light will be easily seen..

[WagonCrazy]

Been planishing in various spots as you mentioned above, but it doesnt remove the generally weak steel-low spot on the passenger side. After working it as you suggested, it didnt really raise itself up or stiffen the metal enough. So I got curious and frustrated at the same time, and tried a little heat from above and it raised it right up and stiffened it when cooled. So I did that in several places around the passenger side weak spots and its now within 1/16" of where it should be and no longer oil canning.

I know this is counter to what you've suggested all along. But the metal seemed to be stretched downward so much that it needed shrinking to raise itself back up and stiffen it. So don't be frustrated with me here, as I am learning as I go and figured this hood may need to be replaced at some point if I can't get this fixed, so I tried the heat...

I'm going to spray 2K primer on it now, and then put the inner brace back on (spot welds around the perimiter) and then put it on the Nomad for now.

Later on when this car goes into the final disassembly and paint prep mode, I may end up replacing the hood with new sheetmetal if I can't get it straight enough for final paint.

This was a good exercise though, and taught me alot about properties of sheet metal and its movement. Thank you for your patience Robert. Greatly appreciate that.

[MP&C]

Good to hear you got it sorted. About the hardest thing to do is give directions on how to fix an oil can over the internet. Sometimes it works better to hammer in the direction the panel needs to go, ie: flip it up side down and planish.

[WagonCrazy]

Sprayed 2K primer on the individual pieces a couple of days ago. Then put it back together and welded the hood skin to the underhood brace (where I drilled the spot welds to separate them earlier).

Then cleaned it up and sprayed it with another coat of 2k primer today.

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That will do it for now. I'll mount it soon and leave it like this until it's time for the whole wagon to go thru bodywork and final paint.

Thanks again for your help. Appreciated!