Cavity Protection

Now that the underside of the chassis is fully painted with satin black chassis paint I wanted to add further protection to the cavities that lurk within the MG Midgets monocoque chassis. For this job I turned to Bilt Hamber's Dynax S50 (Other cavity protection waxes are available) because it also comes with a very useful lance that evenly sprays the wax all around the cavity walls.

The main areas requiring treatment include the whole rear bulk head that is very easy to access with the chassis on its side. MG very kindly left these holes behind to make this job so easy! 😉 I also applied a coat up inside the spring hanger area.

Other areas that need a coating include the cross member, between the inner and outer sills, front chassis legs, behind the foot plate, insides of the triangular supports, inside the a and b posts, inside the doors, under the front lip of the bonnet. or wherever the car is likely to rust, so basically everywhere! However don't spray this until you have painted that section as the paint will not stick to the wax and you'll have to thoroughly degrease everything!

I watched a couple of YouTube videos on how to do this to make sure I didn't waste too much of the product. 

The idea is to insert the lance right to the back of the cavity, start to release the wax and then fairly quickly pull the lance out of the cavity. The Dynax S50 is quite runny initially to allow it to settle into all the cracks and joints. I choose to apply two coats as I can still remember how badly rusted this whole area was.

Once dried the wax does have a tacky feel to it. So hopefully with the new metal, primer, chassis paint, seam sealer and now cavity protection this will last for a good few years.

Once I have completely finished the car I will probably apply underbody protection.

Painting Chassis Underside

Having completed the seam sealing on the underside of the chassis it was time to apply some paint. I wanted to use black chassis paint with a satin finish. 

Before spraying on the paint you need to remove any dust, grease and dirt. There didn't seem much to clean as the primer looked so fresh, but the blasting did leave the surface covered in very fine dust which needs to be brushed off first. I then rubbed it down with surface preparation cleaner which helps to remove any left over contaminates which might affect the paint from taking to the primer.

I have applied two coats to make sure the metal is as protected as it can be.

I am really pleased with how it turned out. You can hardly see the seam sealer, but I know it is there underneath doing its job.

I'm going to be getting some cavity spray to add a final protection to the cross member and the rear bulk head which always seems to get hit by rust. Hopefully not anymore!

Seam Sealer

Having had the chassis blasted and primed it wanted to finish the underside of the MG Midget in preparation for fitting the suspension. 

There are only two jobs really that need to be completed and first up was seam sealing all the joints on the underside of the chassis. 

The seam sealer is a thick glue like paste that seals the joints between two metal panels. It can also be used on welds that have some pin holes left behind. Once applied it drys hard and can be painted over.

I wanted to make sure that every seam and joint was carefully covered whilst not spoiling the freshly blasted metal, which looked so nice and clean with its coat of primer, but it is so important to stop any moisture from entering the gaps as I don't want to be doing any more welding for a good many years to come.

I soon realised there are quite a lot of joints on a monocoque chassis! Here are some photo's of the work, although it isn't that easy to see the seam sealing as it is also grey like the primer.

Now that has all been completed on the underside it is time to prepare for painting the underside with black chassis paint which will protect it from moisture, stone chips and general usage better than standard paint.