250 Monza seat shell repair

[phiba]

Hi everyone, great board here! I've had a 250 Monza in boxes since the 80s and am finally getting around to building it up. It won't be a full-on restoration, just want to go clean, lightweight, and reliable enough for bopping around town. The frame and frame bits are at the powdercoater getting done in muted silver. I had the wheels rebuilt at Buchannons with Akront rims and stainless spokes. My question today is about the metal seat shell. It is pretty badly pitted on top, pretty clean underneath. I cleaned it up with a wire brush, and it is still pretty solid, although it has rusted through in a few places. I was thinking of strengthening it with a layer of fiberglass before sending it out to be refoamed and recovered. But I don't know if I can get a good bond to the pitted steel. And if I go at it with the grinder to get down to bright metal, I am sure it will break through in a lot more places, possibly to the point of being unusable. I'm thinking a good coat of rustoleum, followed with the fiberglass wrapped around the lower edge so even if it comes loose, there is no way for it to come off. Or should I bite the bullet, make a proper plug using the old shell as a model, and make a whole new fiberglass shell? Or buy one? Anyone else have related experience I could learn from?

[Jordan]

Could strips of new sheet steel be welded or brazed to the damaged seat?
I've seen very rusty seat bases come up well with this method.

Jordan

[JimF]

Isn't there some paint-like product that bonds with rust and solidifies?

I like the idea of using the seat pan as a "plug" but first and foremost it has to be structurally solid enough to hold your weight (hence the original steel base.) If you make a seat pan out of fiberglass fab it with a wood base and then glass and resin over the wood to make it waterproof.

[ecurbruce]

How about sandblast the steel pan, if there's enough left of it when finished, then fiberglass both sides for preservation and strenth. Fiberglass will stick best to the raw steel.

Bruce.

[phiba]

Thanks for all the suggestions. They give me hope.

I have seen approaches similar to Bruce's suggestion in a few places, that is, sandblasting to bright metal and applying the fiberglass with a lip that wraps around the bottom edge to prevent separation. One warning I've seen is that over time, the bond will separate, moisture gets in between the two layers, and the metal shell starts rusting again.

Per JimF, I did find a product called Rhino Rust Bond that is a 2-part epoxy primer designed specifically to bond to rusted metal, and it contains corrosion protection too. Although intended as a primer for painting, since it is an epoxy, it may also serve as a base for a fiberglass overlayer. I will probably write them to find out more.

I think I will try Jordan's approach first, welding reinforcing pieces of sheet steel to the existing shell, followed with a good anti-rust primer. The weakest area is on the top surface - the sides are in better condition so could support the welds if I am careful. I have a MIG welder that might be just the right tool for this job. Since the whole thing gets covered with foam and leather, it doesn't have to be pretty.

If I blow it, I can always go to Plan B.