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Joining fiberglass to metal
Dale - 12/4/07 at 06:02 PM

I need to add some glass to make the sides of my bonnet - the top is cut from the donor mgb and I have three options for finishing it- one would be to make the sides of the bonnet removable seperately and brace the top. The second would be to make the sides out of glass and try to join them to the metal top piece without the seem being noticeable. Third would be to make the glass sides and glass under the edges and one thin layor over the top piece as well. I intend to keep the top of the bonnet as metal as I am keeping a certain degree of original sheetmetal to conform in a sort to the very vauge licensing laws here.

Thanks
Dale


RazMan - 12/4/07 at 07:26 PM

Its always tricky to join disimilar materials like GRP and steel because they will behave differently, bending and flexing and changing shape with differing temperatures.
If the bonnet is going to be completely rigid you might get away with grafting the grp onto the steel. You will need to rough up the steel first and apply stranded fibreglass, feathering out the edges but keeping a generous overlap for strength. Then finish off the surface with body filler and smooth the whole lot down to the required profile.
With luck you won't separate the two materials during your prep work but at best it is a fragile join so I would think of another way to achieve the shape you need.


Tralfaz - 12/4/07 at 08:58 PM

Rather than trying to join dis-similar materials, why not make a glass "hood" first, you should be able to simply do an overlay on the steel hood you have, might take some effort to get a good surface finish, but much better than having a bond fail later on.


T


Chippy - 12/4/07 at 10:00 PM

The bond to steel, as long as it is absolutely clean, and well keyed, should be good. It will be a mechanical bond, rather than glue type bond. If you apply a coat all over the top, fill and fair it, and ensure that the underneath has a good wide overlap, job should be good. HTH Ray


Angel Acevedo - 12/4/07 at 10:53 PM

There are kits for installing fiberglass parts, you have to make a crease on metal for the fiberglass to set in, attach with rivets then body filler to smooth


Dale - 13/4/07 at 02:32 AM

considering puttin an inch or two ledge of 1/8 or so depth on the edges and have that drilled with holes. Glass over that and under it. I supose putting ribs under the hood would stiffen it and help prevent cracking. I intend on having the hood hinged at the scuttle as the mgb was.
Dale


locostv8 - 13/4/07 at 06:38 AM

Since you will be well versed in making bucks by the time you do the fenders I would use the original as a basis for a buck and make a glass hood. One of the problems you will face otherwise will be the constant heating and cooling cycles which will lead to cracks.