S2 Bonnet is Warped - Remedy?

[CG901]

Trying to decide on how best to straighen my early S2 bonnet as it clearly doesn't align well with the body. It almost appears to have risen in the centre a few mm. Would this be the result of engine heat? Anybody else have this occur? I do believe it is the original piece. Since it is reinforced with steel rods, I am wondering if some pressure applied at the top centre would correct the warping with the negative result likely to be stress cracks in the gel coat. Any suggestions?

[Grizzly]

I've seen a similar bonnet quite recently that was brought into work to be repaired, we played with it for a week but in the end a second hand bonnet came up and that was used.

I don't know if this is true or not but i believe that is the result of the Bonnet spring pulling the front edge down over time (seems worse on the twin spring early cars). May also be sun/heat related (wouldn't surprise me) but as the car i saw it on had come from warm climates too.

[Geoffers71]

I remember my first S2 in the 60s suffered from this too, although I think it was worse than yours. IIRC I cut slots in the vertical side bits so that the bonnet splayed out and flattened enough to remove the bulge. I then glassed in over the cuts on the inside. I may have glassed over a metal reinforcement bar to help hold it, not sure. From memory I don't think it was totally successful as I remember having to do it at least a couple of times, but then I was young and impatient whereas now I'm old and impatient

[bill308]

Hi CG901.

The two previous responders got it right. The deformation is due to a modest spring load, over a long time, in a hot environment. This is classic creep.

As far as I know, there is no metal embedded in the bonnet fiberglass. The underside H-pattern is a light weight rope covered with glass matt and resin. Slitting and re-glassing the sides is what I did to reconture my S2 bonnet. An embedded aluminum framework or the addition of carbon fiber or unidirectional glass in the side web, might increase stiffness and lessen the creep induced distortion. An underside heat shield might minimize the creep process.

Bill

[CG901]

Bill, Geoffers, and Grizzly,
Many thanks for this information. good to know I am not working with any metal, just fiberglass, so snb a big job.
CG901

[david.g.chapman]

I have a +2 so I am not sure if you have a flange at the front and back of the bonnet.

If you do then I would try a rectangular steel bar fixed to the front and rear of the bonnet running down the centre. The bar would be spring loaded so it is trying to flatten the bonnet. This could be done by making the bar slightly too long for the distance between the flanges. If the bar is rigid in the vertical plane (vertically deep) then the bonnet will flatten out as the bar is fitted. Use steel plates to spread the load on the flanges at each end.

You could use a nut and bolt arrangement to give adjustment, perhaps.

Dave Chapman.

[nomad]

I'm facing the same dilemma on my S1. I planned on slitting the sides and glassing in some stiffener. The question is what? I was thinking an aluminum tube but then began wondering about different rates of expansion due to heat. Would use a glass tube but that sort of reinforcement hasn't worked all that well for Collin!

Kurt
26/3754

[gjz30075]

The S4 bonnet has conduit running around the perimeter. Maybe you can incorporate something like this?

[Craven]

Hi,
I have used a thick Polypropylene rope, shaped around and held temporary in place with tape.
Using resin soaked the rope, when cured this formed a rigid, perfectly contoured core to bond in with glass mat.
This idea seemed to meet the high strength, low weight and compatibility of materials etc.
Ron.

[CG901]

I like Ron's idea in the spirit of light weight and simplicity. I am going to use this method. Will report back when complete. Thanks to all for great ideas.
Scott

[Famous Frank]

You don't by any chance have a tall block 1600 installed do you? Is there clearance between the top of the motor and the bonnet?

Frank

[CG901]

Frank, don't think so. It is the original engine. seems to clear with room to spare.