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MG MGB Technical - Front wing drain hole

I'm in the process of repairing the bottom of the front wing of my B. The reason it's failed is water has obviously settled in the bottom of the wing causing it to rust from the inside. There doesn’t appear to be a drain at the bottom of the wing to allow any water/condensation to escape, is this correct? I'd thought about putting a drain in the bottom of the wing but am concerned as this is an area that will be sprayed with water from the tyres, would this allow water in and make matters worse.

Bob
R.A Davis

Bob, when I bought my first B in 1980 I was aware of this rust trap. I did a simple mod to provide some drainage in this area.

On each front wing there are 3 screws and bolts with oblong washers which secure the bottom of the wing to the sill. I removed these and refitted them, adding four 2BA brass washers to each screw to act as spacers between the wing and sill. This creates a 3mm gap to allow drainage. It is also a good idea to replace the screws and nuts with brass 2BA's.

The car is still my daily runabout and the original wings are rust-free. I do an occasional clean-up under the car and remove the screws and the wing splash plates to check this area, and re-apply waxoyl.
Brian Shaw

Brian

That had been one of my thoughts, I like the idea of the brass screws as well, one of the heads broke off when I removed them. I assume you don't use mud flaps (I don't) and I take it you haven't had a problem with water ingress.

Bob
R.A Davis

No, I don't have mudflaps. Whenever I've checked behind the splash plates the wing has been dry inside, but I expect a bit of water does get in from time to time; waxoyling (or similar) is essential. Although the spacer washers provide a gap of about 3mm, the effective gap for water ingress from the tyres is less than 1mm, due to the bottom edge of the wing being folded back and covering most of the 3mm gap. Attached sketch shows section of sill (blue) and wing (red).


Brian Shaw

I had in mind (although I have no hard evidence for it)that the bottom edge of the sill is not straight - ie when the screws are tightened, some sections between the screws have a small gap remaining to allow drainage.
I think I read somewhere that a regular poke with a plastic drinking straw can keep the gap clear.
Am I right?

Anyway, using some washers may be useful as long as the gap isn't too big

John
John Minchin

Be careful Waxoyling behind the splash-panel, or the similar section at the rear of the sill accessed from behind the B-post trim panel. There is only a very narrow gap between the sill and the wing panel covering it, and Waxoyl will bridge that gap very easily, which prevents the Waxoyl protecting the panel and can actually accelerate corrosion as it traps moisture below it more readily, see here http://www.mgb-stuff.org.uk/sill.htm. I squirt clean engine oil in those areas and slide a pieces of card around to distribute it. It does drip of course, but only for a short while afterwards.
PaulH Solihull

Paul is right about this design asking for trouble. There is a similar arrangement behind the "dog leg" panel in front of the back wheels.It had rusted despite being sprayed with engine oil. When I replaced that I tapped the inner sill in a little way so there was a gap to allow somw airflow. At the front I agree letting water out is a good idea, but I just fitted some mini mud flaps I made from some DPC black plastic which has nylon reinforcing threads in it. This was to take the force of the water thrown up by the wheel and it also keeps mud out. The fitting of the splash plate/wing/wheel arch is so vague that it is nver going to be watertight if you keep it clean
Stan Best

Having already some rust in the bottom of the wings both sides, but in comparison to the full wing it might total @ 5-10%. I don't therefore feel inclined to re-new the whole wing, with the attendant problem of wing mis-match and door shut lines going askew. What in the members view would be the very least repair I could do? Note, I have no welding experience nor do I want to 'farm' this out.I am happy for a compromise that allows me to set a date for a permanent solution. Thanks Mike
J.M. Doust

Update

Over the weekend, I replaced the bottom 5 inches (approx) of the driver's side wing. I used a wing repair panel I got from MGB Hive. The fit was pretty good requiring only the edge by the driver's door being folded a bit further and the profile adjusted to suit. The bottom flange where it folds under the 3 mounting screws isn't a right angle but more like 45 degrees, but this could make it better from a drainage point of view allowing any water to run straight off. The interesting point about the panel is there's a drain hole at the front edge. The fitting went better than I'd expected so I'm now contemplating doing the other side which I'd planned to put off until next winter.

Bob
R.A Davis

JM - do what Bob has done and get a repair 1/4-panel. This usually is quite a bit bigger than needed, only replace what needs to be, it is usually only the part adjacent to the sill and a little above.
PaulH Solihull

Sounds like the way to go, but I will have to weld? Or get some-one to do it for me once I have it all offered up and ready? Thanks Mike
J.M. Doust

Yes repair panels do usually need welding, only the complete panel would be bolt-on, and only for the front wing. However it's not structural so I suppose you could get away with a line of recessed pop-rivets, the joddled seam usually needs filler anyway.
PaulH Solihull

At greater cost, I used panels that joined at the "chrome strip" position, so the strip covers any welding repairs and there is less work overall to get a good result
John
John Minchin

John,

I'm about to fit the same panels, how did you weld them? I'm minded to seam weld along the back so that any distortion is kept to a minimum, then tack along the front to stop flexing?
Pat Gregory

Update

Both repair panels now fitted and in process of being painted. A bit of background on the problem may be of assistance to others. At some point in the past the car had been extensively refurbished and the car is still very solid having most of its original panels with virtually no rust. The exception to this was the lower front wings.

The reason I hadn't spotted this earlier was that in an attempt to keep water out of this area the splash panels had been sealed around the edges. Whoever did this did a very good job which is why I hadn't removed these panels for inspection. Unfortunately this appears to have been the downfall, although they were doing a really good job of keeping water out, any water that did get in couldn't then get out.

I've now (hopefully) remedied this situation by allowing drainage using Brian's method in conjunction with the drain holes in the new panels. I've also only used the rubber seals so the splash panels are easily removable.

The expression that best sums this up is "the enemy of good is better" in trying to make this better the PO actually made it worse.

Bob
R.A Davis

Pat
Sorry for the poor response!
I didn't do the work but they were welded - you couldn't see the join but in any case it was behind the strip
John


John Minchin

This thread was discussed between 14/03/2012 and 02/04/2012

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