Bonnet Repair.

[lanciatomcat]

May I pick the brains of the learned folk on this forum as to their experience with repairs to a rusty leading edge to the bonnet. I see this as a problem area trying to weld in new metal without distorting the line of the bonnet.
Comments appreciated please.
Thanks.

[Andrew S]

Hi Tom,
If you can post a photo of the rust it would help me to advise the best repair. If not, all I can say is this type of repair is extremely difficult to execute successfully, especially if the rust extends up the skin of the bonnet. If it's the full width of the skin and a few inches into it you may be better off replacing it. The problem is, as you say, heat distortion from welding. For repair to this kind of panel gas welding is really out of the question. Mig is generally the way to go but this still has major heat issues involved. Small welds, many minutes apart is the way to do it so the metal recovers slowly and gently. (If the panel only has surface rust and no holes or perhaps just pinholes then a good session with the grinder to remove EVERY trace of rust and some lead loading can cure it totally.)

There are methods of repair that don't involve welding at all of course. There are some amazing glues available that can be utilised to join metal repair panels together. Yes, glue! Non-structural repairs can be made using this kind of method and it can be very successful. I've even seen a full strip repair right across the front of a Monte bonnet (including the dropped edge) that was rivetted onto the skin around an inch into the panel. Obviously this was around 1.5mm too high at the front so the panel was realigned by dropping the hinges slightly to line it up with the noseband. Lead loading the join and then a skim of filler going around 4 inches up the bonnet to disguise the drop and blend in the join and you couldn't tell. Rivets are generally aluminium and can of course react with the steel. I'm no expert in the chemistry involved in this but I will say if the whole repair is completely encased in the lead loading/filler and subsequent paint (in other words- air tight) then I think the reaction is less likely to happen. The repair described here was carried out 7 years ago and is still immaculate. (When doing any kind of repair to a panel like this you must pay just as much attention to the invisible side of the panel too because moisture will find it's way in anywhere it can.)

Anyway, I hope this has been of some use to you.

Andrew.

[lanciatomcat]

Andrew
Thank you for your extensive comments.
I will study what you have said and will post some close-ups of the offending edge area for review.

[lanciatomcat]

I ahve taken some pictures of the offended corner to give some indication of the extent of damage. Intend to clean back the whole of this edge to see if 'rust' is just below the top surface or not.
Hope they are of some use.

[SubGothius]

Another option to consider, if the existing panel can't be saved and if a rust-fee stock replacement is impractical to obtain:

I seem to recall having seen some sort of fiberglass replacement hood panel, something in the style of an 037 Rally Stradale, or at least with Integrale-esque louvers moulded in that could actually be cut to open the louvers and made functional with some homebrew ducting behind the radiator.

Just an idea. 8)

[lanciatomcat]

Hi there,
I had a 'mobile welding' guy around yesterday looking at work on my Project S1. He was of the opinion that the leading edge could be repaired with some care. He estimated 3 to 4 hours of work cutting out the existing and stitching in a repair panel. He gives confidence in his general welding ability although he had not worked on a Monte before. He was only able to slot me in for work in 10 weeks time! Maybe some indication of his ability!!?
I do in fact have a very good alternative bonnet that I would use if this did not work out but I appreciate your comments. Thank you.
Regards
Tom

[Andrew S]

Absolutely every panel for the Montecarlo is available in glassfibre, exact replicas of the original steel.

Andrew.