Foam filled sills

[2311Jethro]

Hello, I have been an observer for a long time, but as I didn't have a car of suitable pedegree I kept my distance. I am now about to take ownership of a true Mk1, in kit form! However it has very few identification marks, other than foam filled sills. Does anyone know when these 'solutions' were applied, so that I can get a better picture of when it might have been built? Mark F suggested between 1960 and '61 but is there any way of nailing this down a bit better? Thanks.

[Sceptre123]

My December 1960 built Morris Mini car had foam filled sills.

[Benny]

My April '60 car has its original foam-filled sills.....and not a rust blister to be found!

[InimiaD]

My March 61 Morris has the foam.

[2311Jethro]

Thanks, have any of you had to put A-panels on? If so, what did you do about welding near the foam?

[InimiaD]

Have you got access to a BMC service manual.? There's a section regarding repairs to foam filled sills which states that the foam must be scraped out from behind the intended repair section where any heat will be applied; gas welding etc.

I'll try and find it you need more details.

[InimiaD]

Here's the info you need. I suppose the same method should be used for the Apex panel repair.
The text also shows the body numbers of when the foam sealing was introduced and ended. Should be able to pinpoint a start and finish date with those body number details.

Bodywork Foam001.pdf

[2311Jethro]

Thank you, that is brilliant, I will read with interest.

[rich@minispares.com]

the foam absolutely honks if it catches fire when your welding


ask me how I know

[2311Jethro]

I'll bet it does, the BMC manual only suggests clearing a 9mm gap behind the panel to be welded. That seems a bit tight, but we will soon see!

[Chalkie]

Can you foam fill any sills? like expanding foam or what?

[Tim]

I foam filled the sills (aka the "Bermuda Triangle") in my old Moke. I had to cut it up later and it seemed to have done the job very nicely.

Tim

[mk1]

Make sure you have the doors of your workshop WIDE open when you start welding!

M

[andy1071]

You can fill any sills, Ridinglow.

The usual is to use polyurethane foam (available from fibre-glass suppliers).

You do need to be careful though:
don't get it on your skin, as it burns!
And don't put it into a "closed" box-section, there must be room for the foam to expand, otherwise it will easily distort or push the sill panels off completely.
And of course, there are then the problems of welding in the area in the future (the fumes are poisonous...)

On the plus-side, it sticks like you-know-what to a blanket, and really improves the structural strength/performance of the body (I think BMC said 8% increase in torsional stiffness for each pound of foam added, -I think modern foams would be better).
-You could argue that the crash performance of the body will be improved (but when you think that the side-impact protection is only the door-skin, trim panel, and door-pocket, I wouldn't want to test it! )

In fact, it sticks so well, I reckon you could fit the sills without welding, just using the foam (not sure what the MOT man would say -or your insurance company though).

The foam absorbs moisture during its reaction, so any damp in the sill section won't be a problem.

The PU foam is usually supplied as 2 liquids, that you mix 50/50 (not in plastic containers -heat remember!), and after 15-30 seconds it starts to expand "1950s science-fiction film" style.
You need to raise one end of the body, so the foam fills from the end, and you don't get air-pockets. And you need to drill some fill/vent holes (at least 20-30mm dia) along the sill, and fill the sill in stages (say 2 or 3), allowing the foam to cure at each stage.

I haven't filled any Mini sills (I was tempted with my S, but in the end didn't bother, and used wax injection instead), but I have done it on composite chassis and bodies.

[mk1]

Although it can be done as described above, there is a very definite risk of blowing off a sill & seriously distorting your bodywork if you cock it up.

Not something to be tried on the spur of the moment.

Extra ventilation holes to allow the foam to expand without getting trapped are pretty much essential to be absolutely safe.

M

[rich@minispares.com]

Although it can be done as described above, there is a very definite risk of blowing off a kitchen cabinet & seriously distorting your kitchen fittings if you cock it up.

M

edited for accuracy eh mark.......