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MG Midget and Sprite Technical - Frogeye Bonnet

I am having trouble with my bonnet. The bonnet rear stiffener panel has become distorted so much so that the front locating pegs are forward of the locating holes. I have purchased a new panel but before having it fitted I am seeking some advice. I appreciate it has to be welded on the ends but how is it fitted where it joins the back of the bonnet. Is it welded? If not is it worth fixing it with adhesive to strengthen it? The same applies to the front edge which is not fixed to anything. I would appreciate any advice from anyone who has had the same problem and managed to cure it.
mrm goslin

Hi,
That stiffenning panel is welded at either end where it meets the flange joint between bonnet and wing, and also joins to the top of the vertical stiffening panels at the rear edge of the wings. It is spot welded to the downward pointing flange of the rear edge of the bonnet. It is NOT welded along its forward facing edge. Even spot welds there would distort the surface of the bonnet and prevent it lying to a 'natural' curve. There is likely to be a variable gap along that edge between about 1/8" and possibly as much as 3/8" where it curves downwards at the ends.

The rear flange is bent through rather more than 90 degs. so that the bottom edge points forwards slightly. Adjustment of this bend has some effect on altering the curve of the bonnet to match the scuttle and also some fine adjustment fore-and-aft of the panel gap to the scuttle as hat edge locates in the notch in the top of the channel rubber insert.

Its a tricky panel to get right as any irregularities will immediately show up where it meets the shape of the scuttle. If the whole bonnet is sitting too far forwards have the hinges themselves distorted? The sides of the channel stretch in time, causing the V -shape of the hinge to open out and that would move the bonnet forward.

Other possibilities, if with the bonnet in place, the scuttle panel gap is OK but the front locating pegs are still too far forward then have the 'dumb irons' been replaced wrongly? Is the airbox area OK? and if the bonnet has been stored off the car or even been media blasted the whole curve towards the front can flatten, extending the overall bonnet length a bit.

My experience is ONLY with researching and fettling my bonnet fit over the last 4 or 5 months. Other advice may differ, but I would be cautious about replacing that stiffener until all the other areas have been checked. But then, I assume you will have done so! Good luck!
GuyW

I'd be very reluctant to change the existing one, if in good condition, as you'll likely lose the accuracy of curve against the scuttle (assuming it's good at present). Also, replacement panels are (in my experience) not that accurate and need work to make them fit so maybe it's better to try to address the problem by modifying the existing panel/ bonnet edge etc.
Bill Bretherton

I agree with Bill and Guy. The panel determines critically how the bonnet fits on the car. Its best to retain it and work on other options.
Bob Beaumont

When I restored my bonnet I drilled out the spot welds and removed the stiffener, the side brackets (for the stays) and the air intake. This was the only way to derust the interior of the stiffener. I then checked the stiffener against the scuttle, and it fitted. When the whole lot was welded back together the bonnet still didn't fit properly (it never did before), and was too flat so the sides stood up about 5mm. The problem was the hinges, and I could only diagnose that by removing the headlamps and peering inside with a light. The hinges had distorted with age, and I had to cut V slots and keep trial fitting the bonnet until the hinges adopted the right shape. I then welded up the V slots and the bonnet now fits better than it did in the last 40 years.

There was a similarly tedious exercise with the front locating pegs, which involved trial fitting the air ducting while assembled with screws, until I could weld it all together. The Frogeye bonnet may look pretty, but it's an engineering nightmare.

Les
L B Rose

This thread was discussed between 10/12/2018 and 13/12/2018

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