Convertible sag , can it be corrected ?

supersix

hi , my 1951 Commodore six convertible seems to have sagged in the middle over the years. The doors are tight at the top and have a wider gap at the bottom. The underbody is sound , no rust issues. It seems to me it would have to be jacked up across the center , side to side to get that gap correct again. Of course I’m scared to do that. How have others corrected this problem ? 

ken1962

Seems a few 1960s car brands suffer the same thing and it may be resolved by checking the floor panel strength. You may need to have a professional structural car engineer confirm the cars stress points requiring replacement/support. Probably not a home repair job. Some metals suffer metal fatigue due to use over time naturally eg plane wing supports. Not all cars have the same life, environmental area, etc 

Best of luck ken

Ol racer

FYI

Yes, other old classic Unibody convertibles have that problem as well. Most convertibles get their strength thru the rocker panels and shouldn't be jacked with the doors open.

However, the sag can be corrected as you described by jacking the center, then reinforced at key points by a local frame Shop. 

KustomKreeps

Have helped on a few ragtops that have had similar issues. Not Hudsons mind you.

first one the guy didnt have the wedge to get it sorted correctly straight away and was after a quick fix. Porta power here and there helped the gaps. more than likely  stuffed the underlying problems but hey it made it look straight. at a glance.  the bloke latter sold the car at a heavy lose and brought a Mustang and was kicked from the club.

Second one on a level garage floor we checked its measurements at 300mm gaps along all the chassis. wrote these in chalk on the floor then of course on paper. Using a plumb bob. Now this was before I got into cad & Solidworks- otherwise I would of used all this to quickly see what was happening digitally. Was the drivers side mainly so was more twisted than sagged.  Any way once we could see how true everything was we droped some bolts on the concrete here and there to anchor this and that (technical terms i know) then rig up a bit of frame work above and around the car with chains that we welded on to the chassis.

from memory it went something like. corners bolted down to the floor. then a say a quarter way along the frame  (front to back) winch at 1 click. half way spot 2 or 3 clicks. 3/4 1 click and rear corner zero.
loosen off check measurements repeat.
then it was just off true so had to be pulled forward at one corner.

took some time. many brews. and checking an old 60s hot rod mag who went into the process many times.

Old hotroders use to do this with sweet fek all.
All very nice and nostalgic but you need space, winches and patience. then a heap of hours. 
send it off to a chassis shop who has a rig and get it sorted. bring the shop manuals cos they say all the measurements for these old cars in em generally. Oldfamer no doubt has links to them on his site otherwise oldcarmanule web site has a heap... that is if you are like me and not a HET member then I guess there is the hidden library and im sure it has all you need.(if you are not a member you can still access it if you know how web works)

if they break glass then they are doing it wrong.

take some pics and post them.

interested in seeing how bad it is and the process you went through to fix.

Alex

supersix

Oh boy a big job. Thanks,Dave

bent metal

Kustom Kreeps, once you have it all in about the correct position, then you reinforced the rocker rails?  Or something else?  What makes it stay there?  Could you draw this up on solidworks then stress test it digitally to have the computer show where the weak point is?  Please excuse my ignorance about the computer stuff.