rear wing patch

[RaceDiagnostics]

Guys, I plan to weld in a patch to the rear wings on this XK8 from a pair of clean donors. It will be my first welding job on a visible part of the car, all my other welding has been underneath.

Anyway does anyone have any tips for how to get the original wing and patch panel to match up closely. I was planning to put a paper template over the donor once cut then transfer to the wing to make the mark and cut.

I was also thinking that maybe I should go for a rectangle shape rather than a triangle and then have an overlap if I could joggle the wing along the flattest side?

Any help will be most appreciated.

 

[shed or dead]

Template from thin card is the way to go indeed. Cut the replacement section oversize (I'm sure that's the plan but always worth a mention) then secure behind the original to allow the excess to be marked, then trimmed with the patch away from the vehicle. I realise this will be tricky with the rolled arch.

Personally I'd raise the top line of the triangle so that the line runs in the crest or trough of any major curve on the panel. Leaving the other lines where they are, this would a 4 sided shape (non regular equilateral, or not quite a rectangle). It's tricky to cut a neat triangle out of compound curves using most hobby metal cutting equipment.

Is the panel a single layer? Are you confident to butt weld this considering the rounded edge of the wheel arch?

 

[RaceDiagnostics]

Am I confident, not really, but there has got to be a first time. Parts are double skinned, I plan to also use at least an inch of the other side of the wing.

 

[Jan]

Use an offcut of the same material to practice on until you can get a good, even weld with absolutely no blow throughs every time before you go anywhere near the car. Do not do any of the practice pieces flat on a worktop, but only in 'real world' circumstances as you usually only get one chance to do it right before you turn the replacement panel into just so much scrap and make the subsequent repair even bigger.

 

[BrokenBiker]

I mark out clearly where I am going to cut on the rotten panel, then offer up the donor to ensure I have plenty of material. then I cut rotten bit out as cleanly as possible, sticking to the cut lines closely. offer that up to the donor until you get it to sit properly, all curves and contour lines matched up. then I draw around it, cut it about 5mm outside the cut lines then offer it up. not where it needs to come down and take down gently with a flap disk, checking regularly by offering it up again

 

[RaceDiagnostics]

As suggested I did a bit of practice, looks like I need a lot more.

I decided to try on this part of the donor, the left hand half of this is double skinned with a foam filler you will see in the pics below.

Chopped off.

Cross section.

First mistake, I held the two parts together with magnets and not clamps.

Now I set the welder up and had practiced on some scrap 1mm plate and was getting nice welds, but the first one on the donor went like this.

The next one like this, at this point the foam lit up and flamed till I blew it out.

The third tack looked good but by then the two sections had deformed and overlapped.

Backside of the 3rd weld.

I the impatiently tacked up the rest after turning th voltage down a notch, had a few blow throughs.

Ground it down, too much on the bottom left which was proud till the metal was wafer thin.

I'll chop off another inch tomorrow and have another go.

 

[BrokenBiker]

yep, you need more practice. you also need to get rid of that foam too. it doesn't matter how you try to weld that section, you will always set fire to the foam and contaminate the weld.

using magnets isn't an issue, I use them all the time to align bodywork. just don't weld right next to them, the magnetic field screws around with the arc.

I find tacking an inch either side of the magnets is good enough, then remove the magnet and tack where it was. I generally get decent tacks every inch or so, then stitch weld from one tack to the next, then skip a tack, and start again until its all fully welded. flat back and then fill in any pinholes if there any.

 

[AndyStobbs]

When did they switch to the aluminium chassis - out of interest?

 

[RaceDiagnostics]

It was in 2006 or 2007, mine is a 2002 car.

Ok had another play around. These 7 tacks were identical, I guess the ones that exploded were directly on top of the foam and the good ones were not! I'll need to find a way to get rid of that before the proper job.

The new section which was clean on the back, except fpr paint.

Tacks went on cleanly.

Stitched up between the tacks.

The back.

Ground down.

That feels a bit better.

 

[the snooper]

those welds in the 3rd from last pic look a little cold I would try turning the wire speed down a touch and try to keep your hand steady

 

[RaceDiagnostics]

Thanks all for the comments.

I wish they all looked like my initial tack welds, for those I pulled the trigger a bit to get the gas flowing first, but kept forgetting about that and did notice my hand moving a bit, I will need to get a better rest position.

Ill cut out a few more chunks and keep practicing.

 

[the snooper]

Thanks all for the comments.

I wish they all looked like my initial tack welds, for those I pulled the trigger a bit to get the gas flowing first, but kept forgetting about that and did notice my hand moving a bit, I will need to get a better rest position.

Ill cut out a few more chunks and keep practicing.

that shouldn't cause a problem either your gas flow is to low, should be around 10 Lpm, you are welding in a breeze or are you holding the gun to far away

 

[Wendelspanswick]

those welds in the 3rd from last pic look a little cold I would try turning the wire speed down a touch and try to keep your hand steady

They also look like you were holding the torch at 90 deg to the work, try lowering the angle.

 

[RaceDiagnostics]

I did a lot more practice last night with different settings on the welder (a Clarke 105EN), there are only three voltage settings 1 & MIN, 2 & MIN or 2 & MAX.

I was getting the best welds with the setting "2 & MIN", but got an occasional blow through , "1 & MIN" just did not feel hot enough although that is what is recommended for the steel thickness which is about .8mm, I felt I needed a 2 second tack on the lower setting whereas the higher setting looked good with a 1 second tack and gave a nice flatish tack.

Every now and then I get a wire slip as the motor spindle is bent, the pinch roller is up pretty tight so I think I will just need to live with that.

For the time being I think I will stick with the 1 & MIN setting which will give me more more grinding work but less chance of blow through.

I also bought a set of these intergrip clamps http://www.ebay.co.uk/itm/380557012272?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 they set a weld gap of 1mm, what are your thoughts on the correct weld gap?

 

[Wallace]

Intergrips can be fiddly to setup and you need a good fit on the sheet to keep a consistent 1mm gap, not difficult with clean sheared sheet but used vehicle panels can be hard work. On 0.8mm sheet with a 1mm gap you need to avoid any heat build up firstly to prevent blowing through and secondly to keep distortion to a minimum. Cooling each weld or tack completely with compressed air before starting the next weld is one method I use. Have you looked at the thin metal tutorial on this site?

 

[Robotstar5]

I did a lot more practice last night with different settings on the welder (a Clarke 105EN), there are only three voltage settings 1 & MIN, 2 & MIN or 2 & MAX.

There is a fourth setting - 1 & MAX maybe the one you're looking for?

 

[RaceDiagnostics]

There is a fourth setting - 1 & MAX maybe the one you're looking for?

Yes, I tried that, I think it gave the same power as 2 and min.

 

[RaceDiagnostics]

Intergrips can be fiddly to setup and you need a good fit on the sheet to keep a consistent 1mm gap, not difficult with clean sheared sheet but used vehicle panels can be hard work. On 0.8mm sheet with a 1mm gap you need to avoid any heat build up firstly to prevent blowing through and secondly to keep distortion to a minimum. Cooling each weld or tack completely with compressed air before starting the next weld is one method I use. Have you looked at the thin metal tutorial on this site?

Yes, I watched the video and tried that method of regular stitching and got good results, but the general recommendations seem to be to skip back and forth between the different tack and I lost the rhythm a bit and was not so tidy.

I am fairly worried about getting good gaps on the fairly complex shape, I think I will finally start the cutting on Saturday morning.

 

[tflnemesis]

If you can get behind the work, you can clamp scrap copper behind it as a heatsink. I have used some flattened water pipe, hammered as flat as i can get it. It helps prevent distortion but i would still stitch it as per the tutorial because car bodywork is always thin stuff.

 

[Wallace]

Are you just doing the outer panel or that whole lower section?