Separating Bonnet Skin And Frame

[gav240z]

The shrinking disc did more damage than it fixed I'm afraid. So had to do a whole lot of heat shrinking to re-work the panel. Chalk that up as another mistake while working on this part. LOL...

 

So only minor updates..

 

1. I filled in the holes where the badge was, because someone had elongated them too large. So we used body solder - which is much like using a soldering iron with flux/lead.

Video here shows the process. Although instead of a butane torch, we used a soldering iron (electric) to melt it onto the bonnet. A bit tricky with a larger hole, but managed to fill it, then file it down. In the photo below you can see 1 side has been filed and the other not yet.

 

 

2. Next step is to get some kind of panel adhesive to bond between the frame and skin. I might actually weld it into place first, then squirt the adhesive in afterwards to prevent the chance of creating a high spot (if the adhesive is too thick) or low spot if the adhesive pulls the panel "in" too much.

 

I'm not sure what material the factory used, but I'll likely use something like this Lord Fusor stuff.

https://www.lord.com/products-and-solutions/adhesives/fusor-121124-flexible-foam-(super-fast)

 

3. How it's sitting at the moment (photo before the holes were soldered up).

[gav240z]

So... I had painted the bonnet frame with KBS rust seal. The plan was to use the anti flutter foam adhesive between the frame and skin, but the stuff I bought Monday from Autolac was unfortunately just past it's ideal 24 month use-by and as a result had gone hard.

 

So that was a good waste of money and time... make sure if you buy these products you buy them right when their going to be used as they expire and go hard and then are useless.

 

So plan B was to weld and join bonnet frame and skin together and then add in the adhesive through gaps later.

 

The good news is now the bonnet sits nice and flat. When trying to align it before the fact that the skin wasn't fixed in place just made things harder.

 

Now that the skin was welded in place I could fold the rear lip back over the frame.

 

This allows the bonnet to sit flush all around (rear side also).

 

I realise the photos don't show a huge difference, but trust me each step in the process has been significant but not necessarily easy to convey through a few images. You kind of need to see the panel in person and feel it with your hands to see high / low spots etc..

 

My favorite new view, looking down the bonnet from the driver seat and no flutes! All the years I've looked down my 72 bonnet at the flutes and wished they were not there. My first car was my 73 240z and I just loved peering down that long smooth bonnet.

 

 

Some final minor adjustments to the front edge are required and it's not welded to the frame along the front edge yet. I'll be doing that with it on the car to make sure I get it right.

 

 

 

[garvice]

Wow, perseverance has paid off Gav, well done! Looks great.

Edited September 7, 2017 by garvice

[HomeBuiltByJeff]

Just finished reading through this. That is a whole bunch of perseverance for that one part of the car. I know my bonnet definitely won't be that straight, but I am going to try to make it as good as I can. I am mostly worried about welding in a strip at the top and all of the warping that I know will happen. 

 

I have looked at those shrinking discs, so it is interesting to hear that you don't rate it. I don't have access to an oxy torch, but I have a smaller lpg torch which I should be able to use for shrinking. 

[gav240z]

I personally would be careful using MIG on a panel like the bonnet, it's a very long skin and so distortion is easy. Oxy or TIG would be better - although I can't use TIG yet myself, but from what I can see it seems you have far more control over the heat.

 

I think the shrinking discs are good for smaller high spots if used very conservatively (not too much heat), the problem for my bonnet is that the metal has already been work hardened. Before I stripped it down it had already had someone messing with it and so the metal has been stretched, shrunk several times and that's hardened the metal to the point where parts of it just won't budge the same as a fresh skin would have. So it created more work than it reduced.

 

I didn't intend to spend this long on the bonnet, I actually thought I would finish it quickly and move on, but I made several mistakes, and fixing rust is 1 thing, but accident damage is another altogether.

 

Oxy or LPG torch doesn't matter for heat shrinking.

 

I ended up buying another bonnet out of sheer frustration but told myself I'd at least see this bonnet to completion and see how it turns out. I may use it on my other 240z, but haven't decided for sure yet. Still waiting to see if this other bonnet I bought fits well or not (I think it's a NOS part, but could be a reproduction also!).

[HomeBuiltByJeff]

I know my bonnet has been messed with a lot so it very likely has been work hardened. This week I plan on making my own DIY version of a stud puller so I can pull out that dent in the nose (and others I can't get to from behind), so we will see how I go. 

 

I am quite impressed with how your corner patch came out. Was that welded in with a Mig or a Tig?

Edited September 24, 2017 by HomeBuiltByJeff

[gav240z]

I am quite impressed with how your corner patch came out. Was that welded in with a Mig or a Tig?

 

The corner was oxy welded in, only really possible because I had separated the frame and skin and was able to hammer and dolly from both sides. If you don't have access to the rear then Mig might be your only option.

 

The advantage of Oxy is that the weld is not hard like with a MIG so you can hammer and dolly it after welding to dress it up and then only require a very light skim of filler.