** ON TO THE NEXT BIT ** Nose to Tail - 1972 Spitfire MkIV restoration upgrades!!

[Brooky]

Use a touch of loctite they wont come undone whatever you use 👍🏻😎

[Badwolf]

Thanks..knowing my luck, they might never come undone again..even if I want them to!!

[Badwolf]

Right, now here's unusual.  What is the best way of removing an area of POR-15 from a piece of metal plate, without paint stripper. I am trying to go back to bare metal but what I have put on is like armour plating. I have already tried rotary wire brushes and sanding discs. Even tried scraping with a craft knife.  It is coming off, but ever so slowly.  Tried a slitting disc but extreme care needs taking not to cut through the metal.  I have an old fashioned metal plate sanding disc somewhere... after that its a grinding disc or one of those vicious rotary brush wheels that pepper everything with bits of wire at high speed, like grapeshot. This stuff either peels off on its own or sticks like sh*t. Guess which one I've got??

[Brooky]

Heat gun and scraper?

[Badwolf]

Thanks Brooky, but its painted on both side and I don't want to have to redo the other side. Great idea though.

[Badwolf]

As I mentioned earlier in the thread, a very kind acquaintance of mine in the trade obtained for me a tube of Kent 2K panel bond.  This is very similar to the other adhesives that I have tested (see https://forum.tssc.org.uk/topic/2623-back-to-the-bonnet-the-last-words-nose-to-tail-1972-spitfire-mkiv-restoration-upgrades/?page=39)  ..except that this one is 'trade only' but the important thing is that it is 'Thatcham Approved' for car bodywork. It is also only available in 200ml tubes, which at £55.00 per tube is somewhat expensive for the odd job. You will also need the special mixing tubes. One advantage is that it does not need a special dispenser gun, a standard builder's mastic gun is perfectly adequate.

I have now had a chance to test some joints to destruction using the same procedure as before. The results were similar to the others (Which I include below)...

Kent 2K Epoxy Panel Bond (Thatcham Approved)

https://www.kenteurope.com/automotive/product/detail/seam-sealing-panel-bonding-c29807244en/2k-epoxy-panel-bond-p20814024en/show/

Peel/Cleavage... the joint broke when the 50lb bucket of metal reached 20" along the bar. 

Sheer... The joint was still strong with the bucket 42" along the bar. The addition of the 10lb house brick made little difference, but with the addition of another brick (8lb), the joint fractured with a bang.

Fast Mover Panel Bond 20

Peel/Cleavage... 10"

Shear...26"

Fast Mover MMA

Peel/Cleavage... 30"" 

Shear...Did not break with the extra 10lb brick (Did not try with the 2nd brick for this test)

Scotch DP490

Peel/Cleavage... 16" 

Shear... 26"

So what does this all mean. Firstly, it means that I now get on with the job of repairing my bonnet using the Thatcham Approved structural bond. What it means in the way of strength of joint I will pass this over to those of you with degrees and things, but I think that the shear test on the Kent means that it fractured with 238ft/lb of force on the joint (Please correct me if I'm wrong).  Whether this is good or not, please discuss!!!

 

[Brooky]

What parts of your bonnet are you using this  method of bonding?

[Badwolf]

Brooky - I have a few on the bonnet. Primarily the repair plates under the headlight cowls and also small sections where the bolts which locate the cowls pass through the bonnet. These were butchered during the first refurb. I am also going to do the windscreen side rain gutters which are just spot welded in place and a couple of small repair pieces at the top of the door edges opposite the B post. These are currently just fibreglassed

 

[Brooky]

I think the Kent stuff will be more than adequate for stuff like that 👍🏻

Ive taken panels off this GT6 where the spot wels have literally just peeled off lol

[Badwolf]

The plate that the original repairs were made from was double overlapped. The welds came apart with the flick of a screwdriver to reveal that the back of the plates were badly rusted. It was probably the rust action that was holding the plates together in the end. I will be documenting the work over the next few weeks, but even trial fitting the new panels with temporary self tappers made the whole structure more secure.

[Brooky]

You could leave a few self tappers in and grind the heads flat maybe 👍🏻

[Badwolf]

Brooky - Thanks for the thought but I will stick (sorry, no pun intended) with the sealed rivets for a variety of reasons.

No sharp point on the reverse side, better grip.. rivet rather then the fraction of a mm thread grip of a self tapper

No danger of stripping the self tapper thread due to over tightening

The rivets I'm using are countersunk, so a quick flash over with a sander should smooth them off quickly even though the rivet head hole will be finished with a little bond. The result should look very similar to the original spot weld when painted but with the strength of the continuous full width bond between the plates which also excludes moisture and air so should minimise the chance of rusting from the inside out. Even though I will finish off with seam sealer.

When I stripped out the old 'repairs', the inside of the plate was very rusty and, as mentioned earlier, the welds were probably no stronger than the bonding effect of the rust. Ironically, I started the replacement because the edge of the bodged repair was knife sharp and santed something a little less dangerous to the fingers.

[Badwolf]

So here we go.  You will remember the state of my poor steel bonnet from these photos:

The plan was to just strip off the paint and re-paint, until I looked underneath and saw this...

The original repairs of 30 years ago, with very doubtful welding and a razor sharp edge. Poking around with a screw driver gave the following results...

.. and the metal came away very easily. Probably only held in place by the rust underneath the replacement plates.  So.....

... off it all came.  Both sides, just as bad. The underside of the bonnet was treated to a liberal treatment of Starchem Synstrip paint stripper and off came the paint and crud as well.

Rubbed down to mostly bare metal and treated to the full works cleaner, rust treatment and two costs (as per spec) of POR-15... yes I know, the Marmite paint. You either love it or loath it. I had bought it some time ago so decided that I might as well use it.  The parts that I have done appear to have stuck on well, hence my enquiry previously about how the get back to bare metal..the answer being a very new 40 grit stripping disc, which bunged up fairly quickly but did what I needed.. Sorry, no pictures of the paint job.

 

[Badwolf]

Well... for better or for worse, the job is done and the structural adhesive is quietly curing - I hope

A moment of panic when I found that I was short of 5 rivets but a temporary fix of self tappers saved the day. I will post some photos tomorrow so you can all say.. 'he should have known better' or 'that will ever hold'!! One thing that I have noticed from my fibreglass bonnet is the microscopic amount of fibreglass that is actually used where there is a full pressed plate for the steel one. I will post some photos of this as well for comparison. Just hope that the adhesive cures properly now. The test pieces set like.. well, steel!!

[Badwolf]

So, as mentioned, the bonnet was painted and prepared for fitting the repair panels. Old mats were put on the bonnet to protect from tools etc. Originally, I wasn’t going to treat any of the metal, but some of it was pitted with some rust so it was given two coats of Bilthamber Hydrate 80, which was allowed to cure and then sanded back to give a key to the bond…

I prepared a couple of angle pieces to run along the back of the headlight plates to replace the metal that had disintegrated and had not been properly replaced when the previous work had been done (not shown in the pictures).  All the plates were then put in place and cut/bent as needed to get a decent fit considering the state of the remaining plates and the fact that I didn’t want to cut away too much metal. Holes were drilled though and countersunk to accommodate the recessed sealed rivets that I was using to hold everything in place while the bonding cured..

Then everything was trial fitted again using self tappers and the bonnet tubes fitted to make sure that everything went where it should without any problem. Everything was measured and checked against my fibreglass bonnet, including running a bar through the holes in the hinge boxes to make sure that they lined up…

When everything was adjusted, it was taken apart, yet again, and the panel bond applied where it was needed. This panel bond has a fairly short working time and is messy so I’m afraid there are no photos of the actual bonding going on.  Everything was then aligned and riveted in place, squeezing the excess bond out. Amazingly, it looked very much like a seam weld in places….

A couple of clamps were used just to add a little extra in places where a rivet wasn’t suitable. You can see the self tappers where I was short of the four rivets. This panel bond is ‘Thatcham Approved’ for body work and contains .25mm glass beads so that it is not possible to squeeze out all the bond when riveting/clamping up, ensuring that enough bond remains to hold the joints together.

That was it. Now left for the bond to cure. It will be sanded back and painted in due course.

Sorry that there is a lack of progress photos with this. Black sticky panel bond and heavy duty rubber gloves (marigolds !!!) are not really condusive to handling a camera and keeping it clean.

On checking measurements of my fibreglass bonnet, I was amazed to find that the areas of fibreglass that the bonnet tubes were bolted to was very small compared to the metal repair plates. Thankfully this should be coming off soon.

So that is it for the moment. After all the testing of various products, the plates are now in place ready for painting. Whether the bond will hold when the bonnet is fitted, time will tell. I will of course report back, good or bad.
You can now tell me it was a bad move and I will regret it!!!

I would like the thank Karl (Bordfunker) who put me on to Chris at Flat Cap Classics who has helped and advised me with this particular project.

[Pete Lewis]

watched the production process of the new hybrid london TX taxi cab  on TV   

thought of you  as the whole thing was held together with adhesive , not a single weld on the whole body 

and they do test pieces to ensure its cured ok  samples are on each cab body and stress tested  after curing 

pete

 

[Badwolf]

Never been a trend setter before.

The joints do appear to have cured well. Up to now I'm very pleased with the result. Trying to pick up the whole bonnet with the bonnet tubes doesn't appear to cause a problem, except with my back.

[Bordfunker]

That sounds like a good outcome, particularly on a non-structural element like bonnet, where the risk of heat distortion from welding is high.

No thanks required though, as Chris’ posts on Retrorides are a master class in how to do the job properly.

Karl

[Badwolf]

Thanks Karl.

To finish off the underside for the time being...

.. the rivets were filled with panel bond and when cured flashed over with the sander...

Then the remains of my 'Marmite' paint (POR-15) was used on the bare metal after doing the prescribed 'prep' work..... and finally....

.. the bonnet tubes were fitted with suitably black painted bolts.

All in all it has taken an awfully long time to test the structural adhesives and choose the final one (Kent 2K Panel Bond), but hopefully it was worth it. The somewhat rough replacement panels that you can see on some of the photos, especially the one directly above were done on the original restoration 30 years ago. These proved to be secure and in a good state, which is more than I can say for the ones featured earlier!!

The bonnet has been turned over ready to work on the top. At one point the full weight load was put onto the hinge boxes for quite some time. There was no damage to the joints, not even a bit of cracked paint, so we will see how good this job really is as time goes on.

Having used up all the POR paint, and not now wanting to buy any more, I now have 3/4 of a gallon of POR 'Metal Prep' and half a gallon of POR 'de-greaser'. Can anyone advise me as to what I can use this for (sensible answers please.. I am too tight fisted to simply pour it away!!).  The de-greaser, I can probably use for washing down paintwork prior to re-painting, but I am not sure of the 'Metal Prep' as I'm not sure exactly what it does.  Scientists... help please!!

I hope that some of you have found this of some interest. I know that some will say, only welding will do, some say, move with the times... we will see. The rest might be more straight forward, but with a Triumph... who knows.

[Pete Lewis]

you have made a giant leap and we all await the reports in time .

this is the sort of stuff we need rather than the must haves thats consistently cause headaches 

all you need now is a few hours on belgium pave'   to advance the testing time  Ha !'  or some local  Cobbles  

upward and onwards 

Pete

[Badwolf]

Thanks Pete. This now opens the flood-gate to replace several bits of fibre-glass around the door edges with metal. I was never happy with the job that was done at the time due to the thickness of the F/G. Bonding plate there would be a much better solution while I have the doors off (cue Michael Caine impressions around the country??).

[Paul H]

42 minutes ago, Badwolf said:

Thanks Pete. This now opens the flood-gate to replace several bits of fibre-glass around the door edges with metal. I was never happy with the job that was done at the time due to the thickness of the F/G. Bonding plate there would be a much better solution while I have the doors off (cue Michael Caine impressions around the country??).

Yes I’m interested in the bonding application for my Vitesse , both sides of bonnet where the locking mechanism is are poor . Fibreglass cracks appearing . Bonding in a new stepped section and skimming with filler is now worth investigating 

Paul 

[Brooky]

But........................

 

 

 

 

 

 

 

 

 

YOU'RE ONLY SUPPOSED TO BLOW THE BLOODY DOORS OFF!

😂🤪

[Badwolf]

14 hours ago, Brooky said:

But........................      YOU'RE ONLY SUPPOSED TO BLOW THE BLOODY DOORS OFF! 

😂🤪

I know.... I really should have known better!!!

[Badwolf]

So after a little while, the bonnet was flipped over.

.. and a sorry looking state it was in. Thankfully it doesn't appear to have suffered too much while I had it upside down to work on the inside.

Three days later having gone through two stripping discs,  and making the dust extractor, which is attached to the garage (well now in the shed) vacuum cleaner...

and we now have this....

.. the DeLorean style Spitfire bonnet.

Amazingly short on rust after being stored for oh so long in the shed. You can clearly see where the repairs were done prior to the first paint job. most of the filler was still solid, but, just to be on the safe side I will take as much of it out as I can, if only to check the state of the metal underneath (if any), repair and treat as needed.

Next job is to wipe it over and treat with Bilthamber Hydrate 80 to get the rust pits that are around in some places. Mostly where the top coat had flaked off leaving just the primer. I will then leave it for a couple of days before flashing over with the sander and then treating it to two coats of 2K primer applied by roller.