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if there's any panel beaters amungst us i'm after some opinoins on using a slapper
i know they shrink and tighten the metal, i have a section in the side of the van where the wakkers that used it as a bash car had an extra fuel neck, where we welded the hole it sunk in we just bogged it (not alot) but it keeps cracking, do you think this could be the solution usind a slapper and dolly
my panel beater mate says it should just after other opinoins thanks

where it shrank you can heat it up cherry red then using a hammer handle push it out while someone spaps a wet rag ova it.
be carefull as this is a quick and effective way to stretch metal.
tom

Hey Mick, does the sunken area also push out from the other side then form a high spot?If so it will be stretched too much and the metal sort of hinges around a spot or spots that need to be shrunk.The technique Munro describes is part of the shrinking process but you need to tap the metal (with a dolly behind it) that has been heated cherry red to pull the surrounding metal into that spot which will then shrink that area.You will probly only need to do one or two shrinks to fix it.

The slapper might fix it but could also make it worse, go the shrink first!

Hey RB,

Pretty much as the others say, if the section oil cans, then it needs to be shrunk, but only in small areas at a time. Start in the middle of the section you welded in or the area that goes boing when you push on it. I use a slapper on all my panel work, for lifting and shrinking dints, but only cold. The slapper by it self won't solve your problem if the metal needs shrinking.
When you shrink a section, heat the metal in a small section about a quater inch round (the tip of the oxy) heat it quickly and then while still red hot, with a dolly behind start lightly hammering around the heated section draging the hammer intowards the red heated area. You can use just about any panel hammer to do this, not a slapper. Once finished hammering around the heated section you can use a wet rag to cool the area. If the area feels tighter but is still low or uneven (not straight) in areas then use the slapper and dolly to bring the areas up or down.

If you haven't done shrinking before be careful or you'll fcuk it.

Oh yeh, if the panel you welded in isn't butt welded (its overlapping) it may be harder to shrink.

Id think its not the depth of bog making it crack but possibly the metal was contaminated with fuel residue ,just my 2c