Braze or solder non-structural body panels?

[safe]

I have a 931 that I need to replace the lower 2-3 inches on the left front fender.

I have another fender that is in good nick in the lower parts. I'm a bit hesitant to cut and weld, both from the warpage and that the 931 fender have some rust on the backside so the metal is probably thinner than stock. (I'm confident the rust isn't so deep that they are scrap.)

Can cut the fenders with an overlap and solder them together with body lead or braze them together? I'm thinking less warping, less chance (which is really guaranteed...) of a blow through while welding...

If you ask why I don't use the other fender all together or get a new one: the other fender isn't that good and its from a 924 that doesn't have the mounting for the sill covers of the 931 and complete 931 fenders in good shape are rare.

[962porsche]

sadly it's not the best idea to braze or solder the piece on .
you need to weld it to have the repair come out properly .
if the metal is so rusted that your worried about blowing thru from welding this tells you that you need to move the splice higher to get into clean good metal to weld to on both pieces .
you will have to clean both pieces so they are 100% rust free both front and back sides . sandblasting is best for this .
when it comes to your welding it's very important to take your time and let each spot weld cool back down . if you feel any heat at all from your last weld it's to soon for the next weld to be done .
when welding a lower patch piece in on a fender you should have no distortion at all as the piece has some natural strength from it's shape . it's not at all like welding a flat piece of metal .
if your really worried about screwing it up get every thing ready and have a person that knows how to weld do the welding part for you . the cost should be very low cost and it could save you in the long run not to ruin the repair .

[safe]

Originally Posted by 962porsche

sadly it's not the best idea to braze or solder the piece on .
you need to weld it to have the repair come out properly .
if the metal is so rusted that your worried about blowing thru from welding this tells you that you need to move the splice higher to get into clean good metal to weld to on both pieces .
you will have to clean both pieces so they are 100% rust free both front and back sides . sandblasting is best for this .
when it comes to your welding it's very important to take your time and let each spot weld cool back down . if you feel any heat at all from your last weld it's to soon for the next weld to be done .
when welding a lower patch piece in on a fender you should have no distortion at all as the piece has some natural strength from it's shape . it's not at all like welding a flat piece of metal .
if your really worried about screwing it up get every thing ready and have a person that knows how to weld do the welding part for you . the cost should be very low cost and it could save you in the long run not to ruin the repair .

Hi and thanks for your answer.

Could you expand on why brazing ore soldering would not be a good option? Its plenty strong and an overlap would be filled by the solder so no moisture could get at it.

Moving the weld higher would mean I could just scrap the fender and try to find a better one, but that's not easy...
The 931 fender is pretty flat so not much strength from shape, I'll have to clean up the rust on the inside properly to see how bad it is.

[962porsche]

2 to 3" up from the bottom edge is about were the body line is and that is a pretty strong area so you shouldn't get distortion from welding it .
that's if you know how to weld and you let the welds cool between your tack welds .
any thing can be ruined by bad welding but your in a good area to weld.

as for why braze or solder isn't good there are a number of reasons . the 1st is strength .
it's not going to be near as strong as a weld . is it structural ? well no but in some ways you still want your repairs as strong as a solid panel is . one reason is impact if the car ever gets hit .
now over lapping two panels is never the right way . you could step one panel they will be kind of even then when you over lap them . but still not the best way to do the repair .
thinking no moisture will get between the two panels because you melted braze or solder your only guessing and hoping you have it completely filled in between the two panels .
now what are you going to do with the inner fender part that bolts the fender to the A piller ?
the sheet metal will be twice as thick there from the over lapping of the two panels .
i guess you could cut away some of the inner panel ?
seams like lots of needless work for a sub par repair ?
lets look at the amount of heat needed to melt the braze or solder over a large area as to the heat needed to burn in a good clean spot weld . a good weld will heat a much smaller area and again if done right you will not warp it at all from the heat .
there are good reasons why a top quality shop wouldn't braze or solder in a patch .

[safe]

Thanks, your arguments makes sense.