Hood Warpage Help Please !!!!!!!!

[coreysiebert]

Hey I am building a 1961 impala and I have some issues with my hood. First off I soda blasted my hood, but had to use a little sand to get the deep rust out of the pits but I used very light pressure and was very carefull, but like always the stinking thing is now warped, and I have had the same problems on a number of hoods that I have worked on. The warpage is in between the two style lines that are on either side of the hood where the panel acutally drops down about a half of an inch. The area is now low in the back and high about half way down the hood and it will oil can somewhat it's not that bad I think it should be an easy fix but in the past I have tried using a torch and heating a spot, but it has never worked well enough to suit me. I now have a shrinking disk from john kelly would that possibly work and where would you start, please help !!!!!!! Hoods have always given me trouble I never can get the panel to stop oil canning.

[Pedalcar]

Hi Corey,

start practicing on an old hood with the shrinking disk you will be amazed.

Hit he high spots and cool down with a wet cloth.

This is the only thing to go start doing it because nothing fixes itself.

have a nice weekend

Ben

[anders nørgaard]

Hi Corey,


Ben just gave you good advice, (as always) but.. actually it's not sure, that the sandblasting STRETCHED the hood. The small amount of heat, caused by sandblasting MAY have SHRUNK the metal. I read this in an earlier post from a guy with dents in a rear fender... Just can't find it... might have been in the period just before coming to the new site. Post could be lost.

To get back to my point; You could try stretching the sandblastd spot instead of shrinking it and see, how it turns out. If the oil can goes awy, then that's it.

http://smileys.smileycentral.com/cat/26/26_23_1.gif

[tvand]

In my limited experience what causes warping from sandblasting it the metal surface is "pounded" by the sand and causes local stretching because the metal is worked on one side, I've seen tractor hoods sandblasted and the outside grows and the hood closes up on it's self. This tells me that the sandblasted area needs to be shrunk but since I can't see the panel I'm only guessing.
Ted

[Gregg Hooper]

Hi
I am the guy that Anders was referring to with the rear fender. And yes the post was lost when the forum was updated.

I would have to say if you have done this before you should no better. I had a bonnet (what we here in Oz call a hood) sand blasted I ended up buying a new one. I will never do that again. Use paint striper and hand sanding to remove the paint and rust.

I would agree with Ted and say that the metal would be stretched on the out side of the skin.

I only have a small amount of experience with a shrinking disc but what I have done so far shows it works. Take your time and as I leaned working on my rear quarter panel that the metal that was stretched was not right in the middle of the oil canning area.

Hope this helps

Gregg Hooper

[coreysiebert]

Well if you shouldnt blast it how do you get the rust out of the pits I have tried it all and blasting with sand is the only thing that works. I have a soda blaster but it will not take off heavy surface rust it doesnt warp panels though.

[CASPER]

Corey,
What kind of sand are you using & how much rust are we talking about?
CASPER

[John Kelly]

Hi Corey,

Here is an excellent thread that Randy did on the subject:

http://hotrodders.com/showthread.php?t=55679

John www.ghiaspecialties.com

[anders nørgaard]

Hi John,

Don't need to go to the hotrodders site to find that post. It's right here on our own site too.<LOL>

http://206.125.208.236/forum/showthread.php?t=2257&page=1&pp=10


http://smileys.smileycentral.com/cat/26/26_23_1.gif

[kustomizingkid]

My neighboor does plastic media blasting and that really seems to be the way to go for warp free results with blasting. Sand blasting really isnt the best for sheet metal its just too hard on it.

Brandon M.

[coreysiebert]

Seriously though, like I said in my earlier post I blasted a hood warped it now I have to fix it. I have tried using a shrinking disk it has seemed to work to a degree, if nothing else I can eliminate the oil canning, but it has the same low spot no matter what I do. The low spot is in the middle right in between the inner crossmembers that come in contact with the outer skin that I am working on. There is about 20 inches between these crossmembers and there is little support in that area. If I shrink in the middle where my oil can is it gets stiffer but remains low, if I take a hammer and dolly and hammer on the dolly to raise this area then go back to the disk to finish it off it just goes right back down. I have read in other posts that you are supposed to work around the oil can but with those crossmembers touching the panel I dont think that would work. Could I have possibly shrunk it too much? I have went over it dozens of times and beat on it countless times I keep ending up with the same thing, How do you get the low spots in a wave up, this is not like a dent it is a wave (Most body men would just mud it but I have my mind set on doing this one right)


Thanks For the Help Next time I will use Naval Jelly

[toolmanMike]

It's definitely possible to shrink it too much.

Mike

[John Kelly]

Hi Corey,

Some full size templates from another hood will tell you what you need to do. You may have perimeter areas out of place without knowing it. If this is not the case, and it is low and not oil-canning, you must stretch it to get enough surface area to get the crown you desire. How low is it over what size of an area.. 20" X? Are you sure the hood was perfect before you started? This is a tough one with the inner structure in the way. All other things considered and discarded, it is possible that you need to stretch more than you have been before using the shrinking disc.

John www.ghiaspecialties.com

[anders nørgaard]

Seriously though, like I said in my earlier post I blasted a hood warped it now I have to fix it. 1) I have tried using a shrinking disk it has seemed to work to a degree, if nothing else I can eliminate the oil canning, but it has the same low spot no matter what I do. The low spot is in the middle right in between the inner crossmembers that come in contact with the outer skin that I am working on. There is about 20 inches between these crossmembers and there is little support in that area. 2) If I shrink in the middle where my oil can is it gets stiffer but remains low, 3) if I take a hammer and dolly and hammer on the dolly to raise this area then go back to the disk to finish it off it just goes right back down. I have read in other posts that you are supposed to work around the oil can but with those crossmembers touching the panel I dont think that would work. 4) Could I have possibly shrunk it too much? I have went over it dozens of times and beat on it countless times I keep ending up with the same thing, How do you get the low spots in a wave up, this is not like a dent it is a wave (Most body men would just mud it 5) but I have my mind set on doing this one right)

Thanks For the Help Next time I will use Naval Jelly


Hi Corey,

John Kelly just gave you some good advice!:
Hi Corey,

Some full size templates from another hood will tell you what you need to do. You may have perimeter areas out of place without knowing it. If this is not the case, and it is low and not oil-canning, you must stretch it to get enough surface area to get the crown you desire. How low is it over what size of an area.. 20" X? Are you sure the hood was perfect before you started? This is a tough one with the inner structure in the way. All other things considered and discarded, it is possible that you need to stretch more than you have been before using the shrinking disc.

John www.ghiaspecialties.com (http://www.ghiaspecialties.com/)
__________________
DVD: Custom Metal Bodywork #1 Stretching, smoothing, and shrinking with special emphasis on using simple hand tools to flare fenders using the existing sheet metal. Roll-forming, checking flow, design, ideas for simple inexpensive tools. ghiafab@msn.com

I think the area is (over)shrunk. The way you describe it I picture it as a flat spot, that should've been a low crown!
1) Shrinking the area makes the oil can disappear because
2)you are decreasing the area and thus putting more tension into it.
3) Stretch the area more with your hammer and dolly, before you finish it off with the disc!!
4) YES you could. In my opinion the surface is to small. You have to stretch it more.
5) THAT'S THE RIGHT SPIRIT!!!

Might be able to use a thin spoon (piece of leaf spring) betwen the panel and the inner structure

Just my 2c
(no smileys on this computer)