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Separating Bonnet Skin And Frame


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#1 gav240z

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Posted 31 July 2014 - 02:01 PM

Hi Everyone,
I tried to see if there was any tutorials on the net about this, but couldn't see anything on any of the big Classic Z websites. So I decided to start documenting my method. Although I have a spare non fluted bonnet in Melbourne - I had originally purchased it with the intention of putting it on my 72 240z (which currently has the later flute style bonnet).

The bonnet that came with the Safari Gold (1970 model 240z) has had a bit of a mishap. As can be seen here:
2013-12-09.jpg

The problem with many Z bonnets I see is that they have all had a slight (or sometimes slightly harder) knock at the front. Often I see this repaired but not to the standard I like.

Here is an example (admittedly not the best) of my 72 240z - when it had an earlier non-fluted bonnet, which had been modified with E-Type style slat flutes in it.
1316gavin240z5.jpg
You might not be able to see very clearly but there is a slight 'droop' in the line at the front of the car - it had been previously repaired after a slightly knock at the front. (This bonnet has since been replaced with the later fluted bonnet below).

1316Gav240z1.jpg

Note how it sharpens the front of the car up? There is a very defining line at the front of the bonnet that is often lost when repaired incorrectly.

The reason for the poor repair is often due to access to the front part of the bonnet. The frame itself makes it nearly impossible to beat it into correct shape from behind. So instead you need to reply on body filler and using a slide hammer or similar to pull the dents out of the front of the bonnet. Which is less than ideal.

Of course you could try and find a good second hand bonnet, but these are getting harder to find in good condition for the above mentioned reasons. Also if you do find what appears to be a straight bonnet there is no guarantee it hasn't been filled with bog etc.. once you strip it. So I'm going to attempt to repair this 1.

To start, here is the basic tools I'm using.
IMG_20140730_194336.jpg

1. Basic multi-speed hand drill
2. Thin Sharp Chisel
3. Hammer - doesn't have to be a soft rubber mallet as pictured.
4. Spot Weld Cutter (see pic below)
IMG_20140730_194342.jpg

I got my spot weld cutters from eBay store http://stores.ebay.com.au/ozmestore1
http://stores.ebay.c...d&submit=Search

The actual drill attachment you only need 1 of, but you can get the cutters separately and when they go blunt just throw them out and replace with another 1. I ordered a bunch at the same time since I'll be undoing a few spot welds.

Cutting out spot welds.

Along the edges of the bonnet is a bunch of spot welds like this.
IMG_20140730_193202.jpg

It might be hard to find them if there is rust, paint, crap covering them. So look carefully to make sure you know where they are.

Start by drilling a small pilot hole in the middle of the spot weld. Then once you've started the pilot hole you'll put the spot weld cutter locator into the middle of this and start to slowly drill.

IMG_20140730_193930.jpg

The idea, is to cut the top skin layer around the spot weld, freeing up the skin from the frame. As far as I can tell the spot welds on the skin are under the front of the bonnet and along the edges and the rear has a lip folded over the frame.

Unfolding lip
I put the bonnet on the grass to prevent damaging the skin or denting it anywhere else.
IMG_20140730_212227.jpg

Using a screwdriver I slowly start to undo the fold at the rear, gradually lifting it up as you go along the rear edge of the bonnet.

IMG_20140730_212254.jpg

I'll update this thread when I finally get the skin off, but for now that's all I've done.

#2 PeterAllen

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Posted 31 July 2014 - 03:15 PM

Gavin, I recommend you drill a small hole in the top layer of the spot weld you are trying to remove (in fact it doesn't matter much if you drill through) rather than rely on a centre-punch mark. It aids the stability and alignment of the cutter.

#3 gav240z

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Posted 31 July 2014 - 03:32 PM

Gavin, I recommend you drill a small hole in the top layer of the spot weld you are trying to remove (in fact it doesn't matter much if you drill through) rather than rely on a centre-punch mark. It aids the stability and alignment of the cutter.


That's what I'm doing, the pilot hole with a small drill bit. As you suggested :)

#4 PeterAllen

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Posted 31 July 2014 - 04:48 PM

Okay, I've just made an appointment with the optometrist.

#5 gav240z

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Posted 01 August 2014 - 10:58 AM

So apart from removing the spot welds along the sides of the bonnet, I also discovered after racking my brains for a few minutes that there is a few 'hidden' ones at the top (the end near the driver) of the bonnet also.

So that's along the sides, at the front under the fold part (where the grill is) and at the rear where the folded lip is. These are by far the hardest to spot (as I discovered).

Posted Image

Separation after that point is relatively straight forward. The frame looks like this.
Posted Image

Skin like this:
Posted Image

The frame is relatively straight, to my surprise I expected to find it bent (from the surface damage) but it was actually pretty straight. Just the top right edge is slightly bent.
https://lh4.googleus...1_=w623-h830-no
Ignore the oily residue (probably from the engine / oil breather?)

To my pleasant surprise the bonnet has almost 0 rust, there is some surface rust here and there etc.. But it's relatively solid - even where it took the hit. I did notice about half-way down the bonnet though on the underside is a bit of a ripple (perhaps from some form of dent?) on the top side it's not obvious, but there is some cracked paint (yep the bog monster nikki*).
Posted Image

I guess just another example of the previous panel master using bog instead of a dolly and hammer  ;D - Each time I find this stuff I'm like this.

* The guys at the tafe course kept referring to filler as 'nikki' and I thought it was quite funny - you know just a nickname. Till I discovered there is a product called nikki.
http://www.paintandp...-a-new-concept1

To be honest after finding the frame isn't that bad and very little rust, I was thinking to myself I really didn't need to separate the skin and frame, but I don't know how I could possibly get the damage out to a level I'd be happy with if I left them together. I guess my tafe course teachers probably would have had some techniques - but at least now it will be easier with access to the rear.

I don't know if it's better to patch the metal that is there and re-shape it, or create a new section and weld it in? Alternatively someone might have a bonnet that is damaged on the driver side in which case I'd be interested in making 1 good bonnet out of the 2?


#6 Brabham

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Posted 02 August 2014 - 12:58 AM

Hey Gav,

you should be able to straighten it relatively easy with the skin off, if that doesn't work you can patch it, I was making up patches for a heavily rusted one at TAFE. I was going to suggest the way to remove the dents with the skin still on is with an "Ezy Beat" machine they have at TAFE. It welds a stud in the bottom of the dent, and you can then exert a pull on it, and twist the stud off to break the weld. No holes, no slide hammers or other bodgery is necessary! ;D The Tafe teacher will be able to help you straighten it and get it back on. Was hoping to tell you about the Ezy Beat before you had the skin off, but you work too fast! :) Looks like a pretty good bonnet though, it is a lot harder when the frame gets bent from a front hit.

Cheers :)

#7 gav240z

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Posted 27 August 2016 - 07:46 PM

Wow 2 years ago I started this thread!

 

So last week at my tafe course I started to hammer and dolly the bent area of the bonnet. However as I was trying to beat it into shape I discovered quite a thick layer of bog/filler and this made it hard to know exactly where I needed to hammer up the bonnet to get the right profile.

 

So I spent the afternoon stripping the old paint using a heat gun because it's likely the paint was lead based and I didn't want lead dust going everywhere using mechanical action, I considered paint stripper but it's messy and I wasn't fond of using chemicals while my dog was around me watching on.

 

I wore a mask because the paint does burn and you can get fumes, which again isn't ideal so I tried to avoid breathing any of that crap in. It's still got a small layer of filler on there, but I'll use a 'seaweed' wheel to strip all that gunk off.

 

You can see I made a template or profile of the bonnet from the other side to see how far up the left hand corner needs to come compared to the right hand (driver side) where I got the profile from.

 

I only found a couple of other minor dents that had been filled in with body filler but thankfully NO rust! Except minor surface rust.

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#8 gav240z

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Posted 27 August 2016 - 07:47 PM

Here is the profile/template, hard to photograph the gap but it doesn't sit flush on the left hand side. Compared with the right.

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#9 jeff43

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Posted 27 August 2016 - 09:45 PM

Your a braver man than me Gav!!!!! I don't mind a bit of body filler provided there is no rust. Good on you for giving it a good go and trying to panel beat the damage out.



#10 CBR Jeff

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Posted 27 August 2016 - 09:52 PM

I looked at my bonnet today....it's far for perfect... Another day.
Looking good Gav, 2 years is probably excessive but completely understandable.
Jeff

Edited by CBR Jeff, 27 August 2016 - 09:53 PM.


#11 gav240z

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Posted 27 August 2016 - 10:17 PM

Your a braver man than me Gav!!!!! I don't mind a bit of body filler provided there is no rust. Good on you for giving it a good go and trying to panel beat the damage out.

 

I actually have a spare bonnet in primer but I bought it for my 72 240z originally because I don't like the fluted bonnets very much. The thing is I am pretty sure if I strip the front edge of it I'll find filler / repair work anyway. So I may just remove the flutes in the bonnet on the 72 and weld them up.

 

At least this bonnet has no rust! I also kind of like the idea of having the same bonnet on the car that it left the factory with when she gets back on the road.

 

I'll be relying on a lot help from my tafe teacher but so far just plodding along trying to figure it all out. I may need to fabricate a small section but the metal on these is quite thin so even using the heat gun it would oil can a bit and then pop back into shape.

 

Good thing about separating the frame and skin is I can get some KBS rust seal into all those areas that wouldn't usually be accessible, which should help protect it from any rust in future.

 

Still a bit annoyed I missed out on a NOS bonnet that was on eBay a while back, but that's cheating anyway ;).



#12 gav240z

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Posted 28 August 2016 - 12:51 PM

Your a braver man than me Gav!!!!! I don't mind a bit of body filler provided there is no rust. Good on you for giving it a good go and trying to panel beat the damage out.


I also figure if it's good enough for this Toyota 2000GT, (hammer + dolly and a little bit of lead filler) it's good enough for my S30Z bonnet.

http://www.studiotim...s_toyota_2000gt

I'd say the 2000GT 1/4 panel repair was also due to scarcity of finding another.

Kind of surprised they didn't fabricate an entire 1/4 panel by hand, but I guess everyone has to make a decision on the best repair method for themselves.

#13 Brabham

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Posted 28 August 2016 - 03:41 PM

Good work Gav. I didn't think they ever used lead based paint on car panels though, I thought they only did that for house paint. I did my bonnet with a crumpet wheel, working around so as not to put too much heat into it. Many hours were spent crumpet wheeling! Will be interesting to see how you go, I may try separating the skin on one in future.

Edited by Brabham, 28 August 2016 - 03:44 PM.


#14 gav240z

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Posted 30 August 2016 - 11:28 PM

Well this has come up better than expected.. There is still a lot of detail work to be done, but I've somewhat surprised myself as to how much improvement has been made.

Spent a lot of time with hammer / dolly and dolly and slapper re-profiling the bonnet.

There is a couple of splits along the leading edge that I'm going to use the Oxy welder to patch up and should give it an even more 'true' look.

Using a slapper helps 'shrink' the metal so it's not really oil canning or anything at the moment but if there is areas that need to be tightened then a quick heat shrink might do the trick.

At some point I'll test fit it onto the car to see how it looks and get a better sense of how it will sit. Not in these photos but the template I was using to determine how much work would be needed (based on the left side) now sits very close on the right side.

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#15 CBR Jeff

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Posted 31 August 2016 - 07:00 AM

It's always hard to pick up detail from photos but it's looking good from this side of the screen.
Understanding shrink and stretch of metal and how to induce control and reverse each is a true art that takes time to master and is easy to get wrong. It looks like you are getting a good grasp of the art Gav!

Jeff

#16 EJ101

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Posted 31 August 2016 - 07:59 PM

Gav

 

what is the TAFE course you're doing?



#17 gav240z

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Posted 31 August 2016 - 08:24 PM

If you're interested have a read through this topic.
http://www.viczcar.c...eorge/?p=166128

But the best thing to do is call the Tafe and ask for the automotive and bodywork department.
http://sydneytafe.ed...hnology#results

Speak to them on the phone about an opening in the night class next semester. A lot of the same faces are there each semester working on their projects.

#18 jeff43

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Posted 01 September 2016 - 07:10 AM

Really nice work there Gav!!!!!!!!!!     Your like a Tafe poster boy!!!!!!!!!!


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#19 gav240z

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Posted 01 September 2016 - 08:36 AM

Maybe some day they will put my face in glossy brochures and I'll be a model a part time model. That's when I'll know I've made it.

 



#20 gav240z

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Posted 07 September 2016 - 05:27 PM

So bit of a mixed update.

Before heading to Tafe I decided to try and mock up the bonnet on the car, given that the skin was not attached properly to the frame it's difficult to get a true sense of how everything will look.

Since I had removed the bonnet latch mechanism I couldn't completely shut the bonnet.

You can see the front right side was about an inch short of the headlight scoop (only roughly placed with fender not fastened down etc..).

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