[Fitzee's Cut and butt method] - Comments on 1st attempt and advice on project.

[Evripidis]

Hello all,

I am going to attempt patching a sunroof panel on my car and was thinking about how to do it. I am a self-taught welder having read numerous posts of this forum and watched endless youtube videos. I got several projects under my belt, DIY but still holding up strong after many years. But this is my first attempt at auto-body welding and at such small thicknesses.

The roof panel is 0.8mm thick and the sunroof panel has been cut off the donor roof (rather crudely) and will be trimmed to a reasonable size before attempting the actual process.

I have investigated the following:

1. to use a joggler, but I soon found out that the curvature of the roof panel might get distorted by the clamping action of the joggler. Then do a lap weld.
2. to weld a thinner piece under and around the existing roof panel after cutting the hole and make a seat for the sunroof panel. Then weld on the top.
3. to attempt a butt weld like the one in Fitzee's video here (

) which has been discussed before many times on here.

After watching other professionals on youtube I decided that the butt-weld is the way to go. I also read on this forum on how to weld thin sheet metal. So far I have done/practiced the following:

0. I purchased a sheet of 0.8mm sheet metal. Galvanised but it was all I could find here in Cyprus. I remove the galv. using a flap disc before welding. I cut small rectangular pieces and start practicing.
1. Set the welder (GYS Smartmig 162) at the lowest voltage setting and began cranking the wire speed up until I could get some penetration without blowing through. I attempted butt welds, etc. until I got the hang of it.
2. I got a piece of copper pipe and made a thick heat sink to use underneath.
3. I use compressed air all the time to cool the panel down.
4. I use a 3mm cut-off disc to grind the welds down and then a flap-disc and an air file. I do this slowly as not to overheat the panel.
5. I do continuous tack welds every 1.5 inch or so.
6. I try to cut at a 45 degree angle as best as possible. You have to cut your patch piece as straight as possible, which could be one of the reasons I am not being so successful.

I am getting distortion in my attempts as you can see in the pictures below (front, back and sides). This is my 5 or 6th attempt. I am guessing that this is because I am doing this at the end of the piece and not in the middle.

I would like to ask the pros on here to give me some pointers and advice.

Cheers,
Evros

 

[Matchless]

I would joggle the edge of the repair panel, you can do that with a bead roller, I would also consider spot welding the joint with Sikaflex 221 between the layers. you would need a big set of spot welder arms, and a spot welder though!

 

[keithski122]

I did a similar repair on a vw beetle years ago, this is how I did it.
Removed sunroof from car to find roof went all floppy so cut wood panels to roof shape and braced roof into position. Used a rolastep to joggle an edge on the body.Cut spare roof section to fit joggled hole. Clamped using clecos (I think). Spot welder with very long arms to spot weld panel in place.Lead loaded around join. Loads of filler applied with car number plate and shaped with long block.
I did do a thread on the forum on how I did it but I'm not sure if it still exists.

 

[chrismac]

I cant say for mild steel, but certainly on stainless steel a small gap ( guess 2-3mm) all the way around give the metal somewhere to shrink, the results on stainless steel was impressive, nearly no distortion, if I was in your position I would give it a go, I would probably use the heat sink you have to save blowing through too.

 

[Evripidis]

Hi all, thanks for the responses.

I only have a hand joggler, the type that punches holes too. Not sure how else to describe it. No access to a spot welder either.

So @chrismac you are saying that I should leave a gap rather than trying to minimise it. I think I read on here that for thinner sheet metal the gap has to be as small as possible but, if I am adding metal I suppose it has to go somewhere. I will try this tomorrow.

I am using a 0.8mm cut-off disc maybe I should use a 1.2mm cutoff disc? Or maybe I should go straight in as opposed to doing a 45 degree cut?

In all honesty my original idea was to joggle the body but joggling the repair panel, @Matchless, I would have to feed the panel from the underneath right?

If I joggle the body am I going to get too much distortion by doing so, i.e., flattening the roof panel?

@keithski122 Seems like an awful lot of work! I hope it don't end up like this! There are roof braces out of which I am going to have to remove one for the panel to fit.

Thank you all for your answers.

Evros

 

[ian f]

never done it but knowing how distorted it could get i'd fix the panel in from underneath with panel bond and fill the outside. i plan on doing this on my mates nissan vanette camper where he wants the hole filling in where the pop up roof was

 

[Nomad]

I've been putting new floors into an older ford using your video above - it works

My routine
Cut the patch slightly oversize, straight edges not curves ( no need for square - many sided is ok if that fits best).
Lay the new on top of the original panel, scribe around the edge, remove new panel, cut original to leave a 1" lip of spare metal.
Cut 1 edge exactly, tack new panel at a few points on that edge to hold it in place (I leave a small gap 0.5mm - the weld will fill the gap)
Use 2 hammers to level the joint you have just tacked.
Angle grinder with 1mm slitting disk at 45* on the next edge, tack, check in all edges are flush.
Repeat for the next edge.
When tacked all around and flush, more short tacks. I weld 2" at most then move 6" to avoid localised heating.

My welds are often high so then lots of grinding high spots / primer / repeat... repeat lots

Some background https://www.mig-welding.co.uk/forum...s-replace-rust-with-solid-metal.128066/page-3

 

[Evripidis]

@ian f I thought about joggling the body edge, plug welding some spots around using panel bond like @Matchless suggested. This might be the better way to do it but I don't know how much distortion the joggler would put in the panel.

@Nomad Thanks for the input. So when you say "Cut 1 edge exactly" you mean 90 degree cut instead of 45? I saw your post, lots of work! The floor pans are 2mm if I understand? slightly thicker than 0.8mm I am trying to patch in? This is my problem I think.

 

[Craig-SM]

If you’re intent on welding it in instead of bonding then drop the continuous bead and just do a series of spot welds, no more than 3-5, overlapping each on. Move to the opposite end of the panel before doing the same do you minimise the heat build up and prevent the distortion

 

[Domdom]

I used Fitzee's cut and butt method quite a bit when welding up the Sierra HERE

With the thin stuff you need to be much more patient. Weld a spot, let it cool. Then weld another spot about an inch away from the first one and let that cool. Don't be tempted to try and spot all 4 corners at once as the metals invariable shrink at different rates so you get distortion. If you have those thumbscrew butt weld clamps they give a nice 0.5mm gap which will help prevent the panels distorting when they get hot with the weld. That's when the worst distortion happens, if the patch cannot expand without causing mayhem. Clamp one of the long edges completely, every 2 inches of so. Weld in between the clamps.

In terms of time taken to do something like a sunroof, expect half a day at least. They are long edges and need time to cool between each weld. I also found compressed air cooling the panel rapidly was not "always" a good thing. Sometimes yes, other times it was not helpful. It also oxidises the weld which is not good. Something I found which helped was to get some thick microfibre cloths, make them wet and wring out lightly and place them strategically on the panels being welded. No closer to the weld line than about 4 inches.

The copper heatsink will help a lot. It allows you to get a well penetrated weld without blowing holes. Keep it in place a few seconds after the weld is finished to draw out heat. But remember, the key is in having a gap, not performing "cold" welds. Look back at some of the old timers who used to do this with oxy-acetylene, heat is not the enemy. You just have to ensure the metal can expand without causing distortion and you do this by controlling the heat, not trying to eliminate it.

 

[MetalMonkey]

On a large floppy panel, I would say your chance of "oil canning" is going to be pretty high, almost unavoidable.
Other than tacking very, very slowly to avoid heat buildup, I don't think there is much else you can do.
The bodywork masters will dolly it afterwards to shrink the metal and pull any buckling stresses out - but that takes a lot of practice and experience to do.

 

[Evripidis]

I am beginning to realise that panel bonding is the way to go with this one. I have done another 4 attempts and still get distortion no matter what the gap or the tacking distance, etc.

I am wondering how to make the flange and on which piece.

 

[zzr1200]

Panel edge joggler:-

https://www.zoro.co.uk/shop/automotive/automotive-specialised-tools/joggler-flanging-tool/p/ZT1228362P?gad_source=1&utm_source=awin&utm_medium=affiliates&utm_campaign=unknown&utm_content=0+%7C+0&pub_a_id=259955&awc=27732_1742306199_e33f323a7686aed6689990a319b0e278

 

[Evripidis]

@zzr1200 That is the one I got. I am already experimenting on how to do the edges. I quickly realised that you have to make them rounded.

 

[zzr1200]

@zzr1200 That is the one I got. I am already experimenting on how to do the edges. I quickly realised that you have to make them rounded.

You can do square patches, I put the "lipped edge" on the repair section, that way you can square have corners.

Some people will say that the lipped section will cause a rust trap, if at all possible fully weld the joint, then if you wish grind off the lip back to form a flat sheet finish.

 

[Evripidis]

You can do square patches, I put the "lipped edge" on the repair section, that way you can square corners.

Some people will say that the lipped section will cause a rust trap, if at all possible fully weld the joint then if you wish grind off the lip back to form a flat sheet finish.

I've cut a rounded rectangle from a piece of sheet metal using an air nibbler. This put a nice lip but I'd like to test your method too.

Have you got any examples to show maybe?

 

[Morrisman]

Every weld you make will pull the material in, so if you peen them afterwards it helps spread the weld out a bit and removes the shrinkage.

 

[Evripidis]

OK, I figured it out. I have to bond this in place with panel bond adhesive.

It has been good exercise with the welder though, pretty interesting. Got close but I am sure I will buckle the roof panel as soon as the torch touches it.

Now I have to find a way to get the bonding adhesive to Cyprus or find a retailer. Always a pain.