How much flex will there be when I remove I/O rocker panels

[sailchef]

I'll be starting soon to do rust repair on both side rocker panels. The outer panel, kidneys, and a portion of the lower latch panel will need to come off but not sure yet about the inner/middle panel. I'll be doing one side at a time. Finishing one side before moving to the other.

I don't have a jig or frame rack, so I will be bracing the car with jack stands 2 front and 2 rear, and by adding a little lite support using 2 or 3 smaller jacks placed at different points to keep the car balanced fore and aft and to prevent any twisting.

Question: If the middle rocker panel needs to come out should I weld in a brace across the door opening to insure the chaisis / door opening doesn't flex, or is the tub stiff enough without it. And where should I attach it so I could still work on door/rocker gaps fitting correctly. I've done a search thru the archives looking at just about every thread that has done this procedure and maybe, only one, mentions using a brace of some type.

Its a 1980 sunroof coupe.

[Porsche_monkey]

Are the doors on the car?

[tabasco]

I'll have to do the same sometime soon, my jack tubes are in bad shape.

I thought bracing was only needed for cabs and targas.

It's hard to effectively use 6 or 7 jack stands. Garages (and sometimes cars) are not straight, and it would take lots of shimming to get all the jack stand to have some load on them. So maybe bracing is better after all.

-Guillaume

[sailchef]

Porsche_monkey

The doors get in the way during the installation process and will be taken off for the removal of old panels. They would then need to go on and off a few times to get the gap fitted properly between the door and sill (new panels) before welding in place.

[Tim K]

Originally Posted by tabasco

It's hard to effectively use 6 or 7 jack stands. Garages (and sometimes cars) are not straight, and it would take lots of shimming to get all the jack stand to have some load on them. So maybe bracing is better after all.

-Guillaume

+1

I think that where you place the jack stands is key.

Three jack stands (one front and two rear) and a brace in the door frame could be the way to go. With simple means, if you were to use four jack stands (presumably a pair up front and a pair at the rear), it is not possible to determine that the front/rear pairs are sharing the load equally and therefore applying a twisting force to the tub. As for their location, I think it would be ideal to locate them such that there would be no bending moment between the front/rear jack stands (i.e. the area you are working in). As far as I know this is not possible to calculate without having all of the parts in CAD and performing an FEA (finite element analysis).

It might even be best to leave the car on the (flat) floor. Yes the car has four wheels, but the suspension is compliant and, assuming the corner balancing is close, the weight should be pretty well distributed between the left and right sides.

As for distributing the weight front and rear (leaving the car on the ground vs. jack stands), I think that a coupe would not be too sensitive considering you would be doing one side at a time and even possibly using bracing.

Tim K

p.s. I think I've seen x-braces temporary welded between the hinge post area to the b-pillar/latch area.

edit: Might there be room just inside the door to weld x-braces in???

[Porsche_monkey]

Originally Posted by sailchef

Porsche_monkey

The doors get in the way during the installation process and will be taken off for the removal of old panels. They would then need to go on and off a few times to get the gap fitted properly between the door and sill (new panels) before welding in place.

Then I would X-brace each door opening with 1" square tube. I did that on my rotisserie build and had no issues. Doors went right back on.

[berettafan]

ooh fun! glad to hear you've made a decision on the car. let me know when i can come up to hand you tools and open beer!

[robmog]

with my coupe, inner and out sills were replaced w/o bracing.
i did level on 4 jackstands beforehand.
doors fit fine.
now its up on a rotissarie for bottom repairs.

[sailchef]

Originally Posted by robmog

with my coupe, inner and out sills were replaced w/o bracing.

This is what I have been reading in other threads.

The local shop that I spoke to has me concerned that the car might sag if I need to remove the inner rocker panel.

I have checked out several threads where other guys have replaced these panels and they don't mention bracing. I'm looking for a concensus before I begin. Adding a brace isn't that much more work, but if it isn't neccessary it would be less work.

[Zeke]

Some points:
The doors do have to go back on at some point before welding, so bracing is not a good idea. Well, it's a good idea, but won't work here.

I level the jack stands with a laser before the car goes up. I use metal shims and/or plates at the bottom. 5 stands will do it, 4 leveled and the 5th under the engine just to take up the slack. You'll know how much when you do it or you shouldn't be welding on your car. 3 stands is not enough.

One simply cannot do this work with the car on the ground. There is welding on the underside to do.

Do not remove the doors by removing the hinges. Pull the pins as difficult as it may seem. If the doors lined up at the b pillar before, they will and should line up at any point in the process as you work. I like them on as much as possible for this reason, but the cutting and welding of the furthermost forward point can't be done with the doors hung.

[sailchef]

Originally Posted by milt

The doors do have to go back on at some point before welding, so bracing is not a good idea. Well, it's a good idea, but won't work here.

This is one of the issues that had me stumbled. The door won't go shut if it's braced, and you need to have the door back on, and shut, to check the gap between the sill and lower edge of door skin.

[Jagshund]

I used bracing (although I was faced with the task of replacing a wee bit more than just the rockers. If I were going to replace just the inner rockers, I now have faith that the cars are solid enough to resist twisting with the longitudinals and pans providing the support. That being said, I would still weld in braces- but only because I'm paranoid.

[sailchef]

Scott,
I have been following your progress. It has provided considerable inspiration.

I think I will take a look at my interior and install a modified version of the supports you have in place. I don't want to disturb the interior to much if I don't have to.

The photo you provided just became the background on my computer.