Mad4slalom
Well-known user
Well , another epic fix underway Tim , so impressed with the way you just get stuck in and get it done . 
72 Corvette - Restoration Updates
- Thread starter TimP
- Start date
Plenty more episodes to come .....
Many thanks for your kind words - which reminds me I ought to write another one. I find it really enjoyable and highly therapeutic to spend an hour or so in the workshop every day just fixing stuff - and my '72 has given me many opportunities for that . It's also good that I'm not really under time pressures (part from getting older!) to get finished. Happy days.Many thanks - much appreciated. PM sent.
Mad4slalom
Well-known user
Would love a look in mr cricket’s Corvette cave, to see his seemingly endless hoard of corvette goodies
quite a few of us have benefitted from his supply, Myself , a pr of LT 1 valve covers and numerous other bits , all at great prices and even a free nos tyre donated to make a clock. Thank you stuart
ps , still hunting for an LT1 or big block short hood . . Glad 
you are helping move Tim’s 72 along too what a great forum this is ! 
This week has been a bit busy on other things but I did manage to finish the upper patch....
I removed the top of the birdcage bow to get access to the welds for the T-Top longitudinal frame piece thingy. The bow has been acting as a collector for an awful lot of rust flakes - not surprising that there were so many holes.....
Next: to complete the lower patch which attaches to the underside of the birdcage bow...
... and then try it out for a welding dummy run although I probably won't use these weld clamps as the join is curved and the clamp is straight so the clamp pushes the pieces of metal further apart than they should.
It all seems to be going together ok at the moment (famous last words) so the next job is to unpick the spot welds on the birdcage bow and construct a new section to replace the rusty bit..... A 700mm square of 2mm steel arrived earlier this week so I think I have everything required to do this.
I also need to start thinking about how this all goes back together as the positioning and sequencing of the puddle welds is going to be important as I don't want to do any welding up side down....(is it even possible?)
I removed the top of the birdcage bow to get access to the welds for the T-Top longitudinal frame piece thingy. The bow has been acting as a collector for an awful lot of rust flakes - not surprising that there were so many holes.....
Next: to complete the lower patch which attaches to the underside of the birdcage bow...
... and then try it out for a welding dummy run although I probably won't use these weld clamps as the join is curved and the clamp is straight so the clamp pushes the pieces of metal further apart than they should.
It all seems to be going together ok at the moment (famous last words) so the next job is to unpick the spot welds on the birdcage bow and construct a new section to replace the rusty bit..... A 700mm square of 2mm steel arrived earlier this week so I think I have everything required to do this.
I also need to start thinking about how this all goes back together as the positioning and sequencing of the puddle welds is going to be important as I don't want to do any welding up side down....(is it even possible?)
Mad4slalom
Well-known user
Blimey! It's been nearly three months since I last posted on this - how time flies.
When I first started the work on the rear bow I think I said it was going to be tricky but that turned out to be a complete under estimation of the task in hand. It was really hard and when you look at the photographs which look like a nice process from A to Z, please spare a thought for the number of interactions where it went wrong and I started again. The main U-shape that forms the strengthener for the bow is shown here in its third iteration. I also don't show that the number of times the glass fibre section that I cut out was refitted to ensure that it was going to fit back on again when everything was done.
So, carrying on the sequence from last time...here is the lower patch being trial fitted with the existing U-section (at the rear) but with a new front section.
This lower patch was then welded in place to form a platform for the top patch assy that I had fabricated earlier...
I decided to brace the butt weld with a 'bonding strip' reinforcement
.... which was then plus welded in place and coated with weld-thru primer
This upper patch was then welded in place ....
.. and then the old u-section was removed (as was the jig that was holding everything together originally)
Then a new u-section was fabricated... this its bowed so had to be (third time lucky) made up from scratch. The first two iterations were made originally from 1 inch square section bent to shape over a wooden former. These looked perfect to start with but when these were welded in place the residual stresses made their presence felt and the heat of the welding straightened them out again. You live and learn......
Here is the old and new u-section on the bench for comparison...
... carrying on this post in a minute ....
When I first started the work on the rear bow I think I said it was going to be tricky but that turned out to be a complete under estimation of the task in hand. It was really hard and when you look at the photographs which look like a nice process from A to Z, please spare a thought for the number of interactions where it went wrong and I started again. The main U-shape that forms the strengthener for the bow is shown here in its third iteration. I also don't show that the number of times the glass fibre section that I cut out was refitted to ensure that it was going to fit back on again when everything was done.
So, carrying on the sequence from last time...here is the lower patch being trial fitted with the existing U-section (at the rear) but with a new front section.
This lower patch was then welded in place to form a platform for the top patch assy that I had fabricated earlier...
I decided to brace the butt weld with a 'bonding strip' reinforcement
.... which was then plus welded in place and coated with weld-thru primer
This upper patch was then welded in place ....
.. and then the old u-section was removed (as was the jig that was holding everything together originally)
Then a new u-section was fabricated... this its bowed so had to be (third time lucky) made up from scratch. The first two iterations were made originally from 1 inch square section bent to shape over a wooden former. These looked perfect to start with but when these were welded in place the residual stresses made their presence felt and the heat of the welding straightened them out again. You live and learn......
Here is the old and new u-section on the bench for comparison...
... carrying on this post in a minute ....
Attachments
..... Once again coating everything with primer...
Then seam-sealing the inside with er.... seam sealer.
... and then welding the top section on and after grinding the welds smooth...
.. and with a coat of etch primer.
It's not quite as it left the factory but it is strong, functions as it should and everything (at this stage, he adds carefully) seems to fit. Incidentally there was one oddity on the bow section: on my car the 'width' of the bow (front to back) was 5 mm less on the passenger side than it was on the driver's. I had assumed originally that it would be the. same dimension all the way along but it actually tapered quite a bit - just under 10% of the width. Whether they are all like that or whether this was just the hand built nature of the car I don't know. Its was one of the reasons why I had to start fabricating some of the pieces again, once this was realised.
All that needs to be done now is to apply two coats of epoxy primer, drill a hole in the top and fill the inside with Dinitrol or something similar (this car isn't going to rust again if I can help it) and then re-bond the missing glass fibre section.
I'm glad to say that this is the last piece of the birdcage that needed to be redone so that's now all behind me. Next, I need to replace all the bits that have been removed to make sure that everything fits and work, and then remove the body and do all the bits (fuel and brake lines etc) that are beneath.
Onwards and upwards....
Then seam-sealing the inside with er.... seam sealer.
... and then welding the top section on and after grinding the welds smooth...
.. and with a coat of etch primer.
It's not quite as it left the factory but it is strong, functions as it should and everything (at this stage, he adds carefully) seems to fit. Incidentally there was one oddity on the bow section: on my car the 'width' of the bow (front to back) was 5 mm less on the passenger side than it was on the driver's. I had assumed originally that it would be the. same dimension all the way along but it actually tapered quite a bit - just under 10% of the width. Whether they are all like that or whether this was just the hand built nature of the car I don't know. Its was one of the reasons why I had to start fabricating some of the pieces again, once this was realised.
All that needs to be done now is to apply two coats of epoxy primer, drill a hole in the top and fill the inside with Dinitrol or something similar (this car isn't going to rust again if I can help it) and then re-bond the missing glass fibre section.
I'm glad to say that this is the last piece of the birdcage that needed to be redone so that's now all behind me. Next, I need to replace all the bits that have been removed to make sure that everything fits and work, and then remove the body and do all the bits (fuel and brake lines etc) that are beneath.
Onwards and upwards....
Attachments
I forgot to mention in the last update that I had also bonded in two 4 x 1and a 1/4 inch painted steel plates to help brace the butt welds at either end of the bow. I used the same 3M marine bonding adhesive that I used to rebuild the glass fibre front end of the car and to bond it to the birdcage. It's pretty strong stuff - quite a bit stronger than Tiger Seal - and although its probably not necessary, it doesn't do any harm to give the bow welds some extra reinforcement.
There are two bolts on each side of the bow on the inside that secure the castings for (I think) the rear T-Top clamps. Unfortunately during strip down all four bolts had declined a polite offer to be removed and had to be drilled out leaving four stubs to be extracted. Welding a bolt to each of the stubs heading allowed me to get some purchase on them and I expect the added heat of welding helped break the threads....
The piece of glass fibre 'roof' that I cut out was given a given a quick test fit....
..... prior to preparing each end of that section and the sides of the roof where it was going to be joined. Using an electric file I thinned down the glass fibre as much as I dared (from 3mm to about 1mm) to allow for approx 3 inches width of new glass fibre to be let in. The old section was then bonded in place with Tiger Seal across the top of the steel bow and held in place with a fairly Heath Robinson arrangement to make sure that it was properly positioned whilst the adhesive went off.....
... and then this section was glassed in place. Cling film was used as a release agent and then some weight placed on top to give some better shape to the fresh glass fibre. There is a also a length of 25mm box section clamped in place to give the leading edge approximately the right profile...
... and then after it had gone off each side (driver's side shown here) was trimmed down with a selection of files, a DA sander, and a sanding block.
The underside has been glassed in too, in the same way although I haven't got round to sanding that down yet. Hopefully, by the time I have finished it should be difficult to tell that this section was ever removed - that's my intention anyway. The joins will need a thin skim of filler when the body work is in pre-paint and there are a few areas around some of the pre-drilled holes that need to be repaired.
It took about 3 months to get this section of the bird cage done and I am glad to have it behind me (figuratively and literally) now. Come to think of it, this marks the end (fingers crossed) of all the birdcage restoration so a major milestone I suppose.
After a fairly intense clean - there is dust everywhere - I will test fit the rear window ( '72 was the last year of the removable window), all the trim and brackets that join to the bow and make sure everything goes together nicely before putting those bits back in the box and moving focus on to the engine/transmission.
There are two bolts on each side of the bow on the inside that secure the castings for (I think) the rear T-Top clamps. Unfortunately during strip down all four bolts had declined a polite offer to be removed and had to be drilled out leaving four stubs to be extracted. Welding a bolt to each of the stubs heading allowed me to get some purchase on them and I expect the added heat of welding helped break the threads....
The piece of glass fibre 'roof' that I cut out was given a given a quick test fit....
..... prior to preparing each end of that section and the sides of the roof where it was going to be joined. Using an electric file I thinned down the glass fibre as much as I dared (from 3mm to about 1mm) to allow for approx 3 inches width of new glass fibre to be let in. The old section was then bonded in place with Tiger Seal across the top of the steel bow and held in place with a fairly Heath Robinson arrangement to make sure that it was properly positioned whilst the adhesive went off.....
... and then this section was glassed in place. Cling film was used as a release agent and then some weight placed on top to give some better shape to the fresh glass fibre. There is a also a length of 25mm box section clamped in place to give the leading edge approximately the right profile...
... and then after it had gone off each side (driver's side shown here) was trimmed down with a selection of files, a DA sander, and a sanding block.
The underside has been glassed in too, in the same way although I haven't got round to sanding that down yet. Hopefully, by the time I have finished it should be difficult to tell that this section was ever removed - that's my intention anyway. The joins will need a thin skim of filler when the body work is in pre-paint and there are a few areas around some of the pre-drilled holes that need to be repaired.
It took about 3 months to get this section of the bird cage done and I am glad to have it behind me (figuratively and literally) now. Come to think of it, this marks the end (fingers crossed) of all the birdcage restoration so a major milestone I suppose.
After a fairly intense clean - there is dust everywhere - I will test fit the rear window ( '72 was the last year of the removable window), all the trim and brackets that join to the bow and make sure everything goes together nicely before putting those bits back in the box and moving focus on to the engine/transmission.