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New blade for your hacksaw?---what new fashioned nonsense!
When hacksaw blades are replaced only the middle part of the blade is usually worn.
You can get extra life from it by using either end.
(this is from the days growing up in England when everything was in short supply!)

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My Brit mother's saying about anything that went on toast.
Scrape it on and scrape it off!


1970 T120R - 'Anton'
1970 Commando - 'Bruno'
1967 T120R - 'Caesar'
1968 Lightning - 'Dora'
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Originally Posted by slow learner
I have seen a lot accomplished with very little in the way of resources.
It's probably best if I don't post my BSA list ...

Today was the Bondo Day. Again, this is the first time I've ever attempted this sort of cosmetic reconstruction so take the procedure I followed with a grain of salt.

The instructions say the Bondo will remain workable for 3-5 minutes, which may not sound very long -- because it isn't. The transition from liquid-like to useless gummy paste comes without warning. One moment I could spread it, the next moment it was too late. The first photograph shows how far I got when the clock ran out the first time.

[Linked Image]

There was still plenty of Bondo on the tray, but it was useless. The photograph also shows the coarse-grit paper I used to remove the excess. I also used a coarse file, with the result shown in the next photograph.

[Linked Image]

The above photograph reveals where more Bondo was needed. Having learned my lesson from the first batch, I resolved to work faster the second time. The next photograph, after subsequent sanding and filing, shows I still wasn't quite there.

[Linked Image]

The third batch finally did it, as shown in the next photograph before I had sanded and filed it.

[Linked Image]

Further sanding and filing got the profile to what looked right (fingers crossed...), with one curvature along the mudguard and several curvatures across it. I then followed the coarse paper and file with the 180 and 320-grit papers recommended by the instructions. After cleaning the area and taping paper to catch any overspray, and waiting the necessary 45 minutes for the Bondo to fully set, I then hit it with two coats of high build primer 10 minutes apart, as shown in the final photograph.

[Linked Image]

I'm typing this while the primer dries for an hour before it can be sanded, which I'll do with 400 grit that I already have attached to the same sanding block shown in the first photograph that I've used throughout. However, that may be too coarse for the next step, which I'll use to reveal any high and low spots that need attention, so I'll use a light touch (or switch to 600 grit).

Any ripples, incorrect profiles, mismatches at the boundaries with the un-Bondo areas, or other defects in the Bondo will be made all too apparent by shiny black paint, so I won't know how well or badly I've done until the, um, dust has settled.

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After letting the high build primer dry for an hour I used 400 grit paper, but then switched to 320 when high spots became apparent that needed something more aggressive. When the shape of the filler felt like a "perfect" fit to the mudguard I switched back to 400. The first photograph shows the repair after I had finished, including feathering all the edges of the primer for a smooth transition to the unrepaired area.

[Linked Image]

The next photograph shows that I then masked off the smaller area in the center that needed a bit more of the high build primer.

[Linked Image]

The last photograph shows the "final" coat of primer drying.

[Linked Image]

When the primer was dry I used 800 grit followed by 1000 to smooth and blend it without removing very much of the material. I then removed the taillight to do the final preparation of the area with 1500, 2000 and 2500 prior to painting it with a gloss black that, I hope, matches the original black well enough to sneak the repair past any concours judges that happen to see it.

[Linked Image]

The mudguard forms a convex mirror, and the remarkably little distortion of the reflected images of the fluorescent lights at the top and bottom of the photograph, both of which cross between the repaired and original mudguard, shows the curvature of the patch closely matches that of the original mudguard (the "blurriness" is caused by fisheye of the thick paint). But, what is the focal length of the mudguard? I'm glad you asked. As the next photograph shows, a set of drafting curves answers your question.

[Linked Image]

As can be seen, a template with radius of curvature 11.5" fits the central two-thirds of the mudguard, containing the reflected images, extremely well. Since neither 11" nor 12" fits as well, this means the focal length of a 1928 Ariel mudguard is –½ × 11.5"±0.25" = –5.75"±0.13" (–14.6 cm). That's an important piece of information you're unlikely to find anywhere else...

Once the paint is dry I'll use a series of 1000+ grit paper on it to remove the fisheye, followed by polishing and waxing to finish the repair.

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Originally Posted by slow learner
I have seen a lot accomplished with very little in the way of resources. It takes more patience and, maybe, imagination
but just look at some of the things that were produced before any of the devices we now take for granted were even developed.
Hi Larry,
You are absolutely correct.
You might enjoy the biography of John Moses Browning the firearms genius. He imagined, no, I take that back, His mind was continually boiling over with new ideas of ways to build guns. He created things no one else could in his day. He began doing this in the late 1800's on a treadle lathe, did his milling with hand made files and revolutionized automatic weaponry. No matter what anyone might think about firearms, his ability to create world class designs with the crudest of tools was astonishing.

Originally Posted by Magnetoman
I'm typing this while the primer dries for an hour before it can be sanded
Hi MM,
Since it seems you are angling for concourse judge approval, here's where your tendency to distract yourself off in some other direction will come in very handy.

You see, Bondo and primers continue to shrink for some time, months even. The best body and paint specialists give the body filler and the primer plenty of time to release gases and shrink before any final finish work is attempted. Bondo gas pimples and sanding scratches coming up through the finish coats are the pits.

After that, the color coats need time to fully cure before color sanding and buffing. Hope this helps.

Last edited by Stuart Kirk; 06/14/21 4:48 am. Reason: More to say.
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Originally Posted by Stuart Kirk
Originally Posted by slow learner
I have seen a lot accomplished with very little in the way of resources. It takes more patience and, maybe, imagination
but just look at some of the things that were produced before any of the devices we now take for granted were even developed.
Hi Larry,
You are absolutely correct.
You might enjoy the biography of John Moses Browning the firearms genius. He imagined, no, I take that back, His mind was continually boiling over with new ideas of ways to build guns. He created things no one else could in his day. He began doing this in the late 1800's on a treadle lathe, did his milling with hand made files and revolutionized automatic weaponry. No matter what anyone might think about firearms, his ability to create world class designs with the crudest of tools was astonishing.
Then, of course, there was Burt Munro and his Indian Scout. The "Offerings to the God of Speed" documentary included on the "World's Fastest Indian" DVD goes into a bit of detail on that front.

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Originally Posted by Stuart Kirk
You see, Bondo and primers continue to shrink for some time, months even. The best body and paint specialists give the body filler and the primer plenty of time to release gases and shrink before any final finish work is attempted.
Now you tell me. Sigh...

Ah, but there's hope. You wrote what "the best body and paint specialists" do. Clearly, that doesn't apply to me, since my first-time attempt at body and paint work is closer to what the worst do.

In the cold light of day I can see fun-house-mirror undulations in the reflected image. Having had time to, um, reflect on the error of my ways, I think I can do significantly better. Since the motivation for much of what I do is to learn something new, not just repeat what I already know, the mudguard's Bondo hasn't see the last of me.

The one motorcycle book I have with "paint" in the title discusses how to repair tanks with Bondo and primer, but doesn't mention shrinkage or outgassing. However, now that Stuart mentioned it, certainly both of those issues must be present. Unfortunately, after reading reviews of a half-dozen auto body repair and painting books on Amazon I've yet to find one that doesn't sound like it isn't too superficial to be useful. So, I'm afraid there will be more trial and error before I'm done with the mudguard (or I quit...).

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A little late to ask, but what Bondo did you buy? There is a Bondo (3M) version and other brands that are easier to sand. Easier to sand = easier to contour, a least at my skill level. Glazing putty might be of use, again easier to sand, so good for filling those things that magically appear when shiny black paint is applied. Oddly enough, it’s easier to feel any defects when wearing a thin cotton glove. I was forced to do that for a day in QC….. probably punishment for something I said.

I’ve used the easier to sand 3M version, but last time bought this….. and would definitely buy it again, along with their glazing putty.

[Linked Image from live.staticflickr.com]215AF675-DB28-459F-8256-DC7E9E90B9A4 by First Last, on Flickr

I was removing this instead of working on my gearbox.

[Linked Image from live.staticflickr.com]BF9D3A32-18D8-4F4B-A9A6-1CC8F9E64084 by First Last, on Flickr


If it gets too stiff before you level it out (hardener ratio is like voodoo) one of these will knock it down if you catch it before it sets completely….. temperature makes a big difference, so you’re probably screwed.

[Linked Image from live.staticflickr.com]2578F653-0D7A-4F9F-B3D2-58ADE0AC5E95 by First Last, on Flickr

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I think I would leave the mudguard repair as is and see what happens over the next year or so, it might be fine or it might change depending on ambient temp and humidity.

Bondo filler can expand or contract as a result of being exposed to extreme changes in temperature and humidity. The depth of filler used also affects how far it expands or contracts, so the thinner the depth the better.

I imagine that your location being hot and dry is probably favorable for using bondo type filler, which is why I would leave it and see what happens.

If you do need to remove it, I would look into using some panel beating techniques to minimize the amount of filler needed.

Whilst you wait to see what happens you could be getting on with some of the other projects in the pipeline.


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1967 B44 Shooting Star
1972 Norton Commando
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Originally Posted by gunner
If you do need to remove it, I would look into using some panel beating techniques to minimize the amount of filler needed.
That's a very good point. While it's more difficult than epoxy, heat shrinking the dent, followed by lead wiping should give the best result.

At least that's what people who have experience in the area tell me.

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Originally Posted by Cyborg
A little late to ask, but what Bondo did you buy? There is a Bondo (3M) version and other brands that are easier to sand. Easier to sand = easier to contour
When in doubt (and often when not in doubt), I go with name brands so I'm using the genuine Bondo®/3M. Getting the contour sanded to feel perfect wasn't the issue, it's that while it feels perfect to the touch, it isn't optically perfect. If only this weren't a Black Ariel, but instead were a Flat-Black Ariel, I'd be done...

Originally Posted by Cyborg
temperature makes a big difference, so you’re probably screwed.
It's 106 ℉ as I type this, headed for a predicted high of 113 ℉ later this afternoon. If I were doing this outside the Bondo probably would take a full set within a few seconds of smelling the activator, let alone having it mixed in.

Originally Posted by gunner
I think I would leave the mudguard repair as is and see what happens ...
You mean leave well enough alone, rather than see if I can make it worse?

Originally Posted by Shane in Oz
[quote=gunner]If you do need to remove it, I would look into using some panel beating techniques
You mean do it properly, rather than bodging the repair?

I removed the luggage rack and the next photograph shows the curvature of the mudguard is very close to having a 16.0" radius.

[Linked Image]

If you look closely you can see a small gap between the mudguard and the gauge near the center of the gauge. However, the fact the gap isn't actually at the center is probably due to deviation of the mudguard from having a perfect curve. The next larger template I have is 17.0" and the fit is much worse.

The next photograph shows that because of the relatively flat profile, the portion of the mudguard closer to the edge has a radius only ~¼"–⅗" less that the center, which is well within how well I can match the radius anyway.

[Linked Image]

Generations of profession panel beaters and auto body repair specialists will turn over in their graves when they read what follows, but it seems to have worked. As the next photograph shows, I cut a radius of 16.0" in a block of wood and glued a piece of 1/64"-thick rubber to it to make a "tool" for sanding the desired radius into the Bondo.

[Linked Image]

The next photograph shows what the mudguard looked like after 30 seconds or so with 600 grit on my new profiling tool.

[Linked Image]

As can be clearly seen, two low spots in the Bondo are obvious, which were responsible for the fun house mirror effects. After a few minutes with 400 grit the larger of the two low spots appears to be gone, and the diameter of the smaller one has been reduced.

[Linked Image]

However, since I could feel a depression in the remaining low spot some Bondo glazing putty is now filling it. After it has dried I'll hit the entire area with a light dusting of black and then use my forming tool again to see if I've achieved a uniform radius.

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Building a profile tool to get the exact radius is a good idea and should help make the repair invisible, even to the most discerning rivet counter.

Since you're keeping the bondo in place, my only other thought is whether the mudguard flexes or vibrates. If it does it might cause the bondo to crack or loosen in some way. It looks like are plenty of supporting brackets to keep the mudguard in place and rigid, so hopefully its not an issue.


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Originally Posted by gunner
whether the mudguard flexes or vibrates. If it does it might cause the bondo to crack or loosen in some way.
I removed Bondo from near the dent the fire extinguisher had made, which required a hammer and chisel. So, the flexing is small enough, and/or the Bondo is thin enough, that it has no trouble adhering to the steel.

The first photograph shows a tiny modification I made to my forming tool that made a world of difference.

[Linked Image]

The sharp edge at either end of the original tool tore the abrasive paper way too easily, but slightly rounding the ends eliminated that problem. However, as the next photograph shows, I hadn't applied enough glazing putty yesterday.

[Linked Image]

More putty is now filling those depressions and I'm waiting for it to dry.

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I'm getting close. The first photograph shows the present state of the rear mudguard after a few rounds with glazing putty and my forming tool.

[Linked Image]

This morning I applied a thin layer of high build primer.

[Linked Image]

Prior to adding the primer the surface felt perfectly smooth to the touch so, if the forming tool doesn't reveal any additional high or low spots after the primer dries, I'll then have to decide how many weeks (days, minutes) to wait before doing the final painting of it. Cautions about long-term shrinking and outgassing of Bondo and primer have been duly noted and understood, although I can't promise they won't be ignored in the interest of impatience...

p.s. after another round of sanding I can't tell if the area in the center is still too low, the area around it is too high, or if everything is close enough at this point that it won't make any difference.

[Linked Image]

So, I'm waiting for a light dusting of black to dry in order to answer those Goldilocks questions.

Luckily, the shortest route to the garage doesn't take me by the rattlesnake who's coiled just outside the front door.

[Linked Image]

p.p.s. There's still a slight depression.

[Linked Image]

Possibilities are to sand some more, hoping there is a thick enough underlayer of primer and paint to remove the depression before hitting bare metal, filling with more putty, or deciding it's already as good as it needs to be. I'll be the first to know what I decide, when I decide.

Last edited by Magnetoman; 06/16/21 8:50 pm. Reason: p.s and p.p.s.
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Originally Posted by Magnetoman
So, I'm waiting for a light dusting of black to dry in order to answer those Goldilocks questions.
Set it outside in the sun. It's natures own baking oven, but I'm sure you already know that.

Originally Posted by Magnetoman
Luckily, the shortest route to the garage doesn't take me by the rattlesnake who's coiled just outside the front door.
Maybe he thinks there might be a mouse or two around there.

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Originally Posted by Magnetoman
Maybe he thinks there might be a mouse or two around there.
Unfortunately, there are plenty of pack rats to keep him happy, but in this case I suspect it was the shady and relatively cool location on a 112 ℉ day that attracted him.

Originally Posted by Stuart Kirk
Set it outside in the sun. It's natures own baking oven, but I'm sure you already know that.
It wouldn't take long at the 180+ ℉ the metal would reach to cook the Bondo to well-done, but the flaw in that plan is the bike is located two-bikes deep in the garage and I still have the primary side to bolt together. However, "luckily" those pizza-oven temperatures aren't going to go away anytime soon.

I moved to a more aggressive 280 grit paper, the result of which is shown in the next photograph.

[Linked Image]

Unfortunately, with so many layers of reddish Bondo, grey primer, and black paint I can't tell what parts are higher and what are lower. So, I hit it with yellow.

[Linked Image]

As far as I can tell by moving my head around to look at the reflections of the light at different parts of the mudguard, there is no remaining distortion. After the yellow paint dries and I lightly remove it I'll be able to tell what parts are higher and what are lower, even if I won't know by how many microns. However, if I have reached the point where the highs and lows differ by only the thickness of a few layers of paint, there will be no visible fun-house distortions in the final, polished gloss-black paint.

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I'm losing track of the records, but today will be either the fourth or fifth day above 110 ℉ so I'm counting the Bondo as fully outgassed and shrunk (true, that's the outside temperature, and the mudguard has been inside, but don't bother me with trivial details...). So, my patience having run out, I rubbed the surfaces down with a series of papers up through 1000, masked the area that needs painting, and hit it with a fairly light coat of flat black "sandable" primer (the implication being, other primer isn't sandable?).

[Linked Image]

If it seems like a larger area is shown than in previous photographs that's only because it is. What I hadn't mentioned before is during all of this I couldn't stop myself from filling some minor dings and divots further toward the front of the mudguard that I could just as well have left alone.

Once the primer dries I'll smooth it, probably starting with 800 but ending with 1000 no matter where I start, and then hit it with several coats of gloss black. Once that's dry I'll smooth it with papers ending at 2000 or 2500, then buff and polish it.

This exercise with Bondo over the past week taught me quite a bit about the right way to do this sort of work. I'm not saying I actually did it the right way, only that I learned what should be done in the future when I care more about the cosmetics of another project than I do about the Ariel's mudguard. Not that I think the mudguard will look bad when I'm done with it, but perfect is the enemy of good enough.

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Looks like it's coming along nicely MM and you don't seem to have encountered some of the other issues which often crop up with paintwork such as wrinkling, orange peel, Bondo shrinkage, bloom, etc.

I've had a few projects go bad where wrinkling appeared after applying the final gloss topcoat or lacquer, probably caused by applying the paint too thickly and not letting the paint dry enough, probably not an issue with the temperatures you're experiencing at present.

I tend to do any paintwork in the shed these days as I've found that if I try spraying paint in the garage, the overspray seems to get in the air and go everywhere.


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Originally Posted by gunner
I tend to do any paintwork in the shed these days as I've found that if I try spraying paint in the garage, the overspray seems to get in the air and go everywhere.
I've been doing all the painting in the garage, trying my best to minimize overspray. But, this has limited my work time the past week since the fumes cause me to evacuate the garage for some number of hours after each painting session.

When I want to do a proper job in the future, I'll build a pop-up paint booth next to the garage from PVC pipe and plastic sheets, use an actual paint gun, and do the work on a wind-free day.

Unlike what I wrote in my previous post, I only used 800 grit paper on the primer. The goal is to have a final gloss paint surface that is shiny and free from orange peel and there's no need to have the primer base extraordinarily smooth to accomplish that. The 800 grit left the surface quite smooth so I decided to skip the 1000.

Directions on the can say the gloss black paint dries to the touch in 15 minutes and subsequent coats should be applied within 1 hour or after 48 hours. So, I made repeated trips out to the garage every 10–15 minutes to apply a total of five coats. The next photograph was taken while the paint was still wet after two coats.

[Linked Image]

As the reflection of the overhead lights shows, there is no sign of residual distortion from my repair, so all the work with Bondo, glazing putty, and the form tool paid off. Addendum: I realized after posting this that I hadn't positioned the reflection over the worst of the damage when I took the photograph so you'll just have to take my word for the fact that "moving" the reflection all around the mudguard didn't reveal any distortion.

As a reminder, the next photograph shows what the pre-Bondo mudguard looked like.

[Linked Image]

The paint can doesn't indicate how long it takes for the gloss black to "fully" dry. However, the "dries to the touch" time of 15 minutes, and the repaint time of less than an hour or more than 48 hours, is at 70 ℉. I've had the garage at 80 ℉ during the day in the current heatwave, rising to 87 ℉ overnight (the default setting I use for the AC in the summer, to keep sensitive items from getting too hot). Since the paint fumes are pretty unpleasant (not to mention, unhealthy), as soon as I finished the last coat I turned the AC up to 87 since I won't work in the garage again today.

Based on the rule of thumb that chemical reaction times reduce by half for every increase of 10 ℃, one day drying time will be equivalent to two days at 70 ℉. I'll finish the mechanical work (assembling the primary side, timing the magneto, attaching the fuel tank and oil line, etc.) before doing the color sanding of the mudguard, so it will have had the equivalent of at least five 70 ℉ days to dry before I sand it.

I couldn't be more pleased with how the mudguard looks at this point, so it remains for me not to screw it up when I do the color sanding and buffing. Unfortunately, this means I'll now how to polish and wax the front mudguard and fuel tank to keep them from looking out of place.

Last edited by Magnetoman; 06/18/21 7:46 pm. Reason: added some text about the reflection
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All of my Sunnen mandrel racks were full, leaving homeless a half-dozen additional ones I had subsequently bought for various special purposes. So, I ordered another rack that arrived yesterday, and today started reorganizing them. The mandrels you see in the photograph cover the narrow range from 0.106"–0.110" (hey, some day I might want to make my own needle jet having some fine-tuned diameter), and then 0.120"–1.250" continuously.

[Linked Image]

I also have mandrels covering 0.869"–2.000" that hold 2, 3 or 4 stones for longer length holes, and 2.5"–4.2" for cylinders, but they're stored on their sides to save space.

Most of the "adapters" (in Sunnen-speak) that hold each mandrel have the sizes stamped on them, but some don't, which is more of a headache than you might imagine. Each mandrel has a truing sleeve and, although all of those sleeves are marked, when several of them have been separated from their mandrels, re-mating the correct components can be an ordeal if the adapters aren't marked. So, I took this opportunity to use silver paint to mark all the non-marked adapters with their sizes. I also highlighted the stamped numbers of the other ones since being able to more easily see the sizes when they're in the racks will mean fewer times I'll have to remove one, look at the (incorrect) size, replace it, and then remove the next one, until I finally locate the one I'm looking for.

Anyway, at this point I can't imagine needing any additional mandrels that will go in the racks so there's a reasonable chance my reorganized organizational scheme will be permanent (-ish...).

Changing the subject to paint, one of the photographs in my previous post showed the glossy black paint after two coats, with quite a bit of orange peel visible. Today, after the five coats had dried, the amount of orange peel is much less than it was in that photograph. This will make it easier to remove when I color sand the mudguard a few days from now.

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The 800 grit left the surface quite smooth so I decided to skip the 1000.

Just wondering what sort of sand paper and technique are you using? I find the best results are to use wet & dry paper which has been soaked in soapy water for a few minutes. The water helps prevent the paper clogging and you get a better finish than if you used it dry. I usually go all the way up to 1500 paper but you have to be careful not to break through the top coat, especially at the edges.

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Unfortunately, this means I'll now how to polish and wax the front mudguard and fuel tank to keep them from looking out of place

I would try using rubbing compound which will restore old paintwork and can also be used as a final polish on new paint. Various grades are available and you can use a drill mounted mop to assist, but be careful and go gently to avoid breaking through the top coat.

Last edited by gunner; 06/20/21 9:04 am.

1968 A65 Firebird
1967 B44 Shooting Star
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Originally Posted by gunner
Just wondering what sort of sand paper and technique are you using? I find the best results are to use wet & dry paper which has been soaked in soapy water for a few minutes. The water helps prevent the paper clogging and you get a better finish than if you used it dry. I usually go all the way up to 1500 paper but you have to be careful not to break through the top coat, especially at the edges.
I have paper from 180 through 3000, which I've been using dry in the interests of expediency at nearly all times during the past week. The next photograph shows the "holders" I have for backing the paper.

[Linked Image]

Ignoring the form tool I made from a block of wood, the tool at the left is hard rubber so is most appropriate for use on surfaces that are pretty flat. The two rectangular pads at the right are of different thicknesses, but both quite flexible to follow contours. Under them are a set of four round tools of different diameters, none of which will be needed for the mudguard.

The main problem I'll face is blending the step between the new paint and the old, shown in the next photograph.

[Linked Image]

The step looks higher than it actually is because of the paint that wicked up onto the edge of the masking tape to form a narrow raised lip. Once that lip is knocked off the step height will be the height of 5 coats of paint, which is probably ~0.005". The trick will be to sand a "ramp" near the edges of the new paint to make it smoothly meet the old paint without at the same time removing 0.005" of the old paint (which might not even be that thick). However, I'm not the first person who has had to deal with this issue so I'll do a bit of research to see how to approach this.

Originally Posted by gunner
I would try using rubbing compound which will restore old paintwork and can also be used as a final polish on new paint. Various grades are available and you can use a drill mounted mop to assist, but be careful and go gently to avoid breaking through the top coat.
I have two grades of rubbing/polishing compound, the coarser of which says it is for removing scratches and the finer for polishing. The next photograph shows my 2400 rpm pneumatic polisher/buffer with three of the accessories for applying the polish.

[Linked Image]

I have quite a few of the soft foam "finger" pads like the one on the polisher, but also thinner denser and thicker softer cloth pads.

I would feel more comfortable if the polisher had a slower speed, but nearly all the ones sold for this purpose list rpm in the range 2000–3000, with the slowest I've seen, marketed for waxing, of 1500 rpm. Anyway, possibly being overly cautious, to make sure it doesn't "burn" the paint I use it in fairly short bursts of a few seconds each, frequently recharging the pad with fresh compound.

As can be seen from the next photograph, much of the surface of the front mudguard is protected by girders, pedestrian slicer and frame so polishing it will require a lot of tool-unassisted Manual labor.

[Linked Image]

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I reorganized my Sunnen mandrels yesterday.

[Linked Image]

Even though I have the full ranges of sizes covered, from needle jets to Gold Star cylinders, so I'll never need to add any more mandrels, the additional rack I bought allowed me to leave empty slots in each of them in case I add any more mandrels. For what it's worth, Sunnen makes mandrels for holes down to 0.060" (~1/64"). Although no motorcycle use immediately comes to mind, it's not inconceivable that someday I might need one of them.

The reorganization allowed me to confirm I actually have all the mandrels I thought I had, and also allowed me to "discover" I have extras in two of the sizes. I bought one of the extras in pre-Sunnen times, planning to devise some sort of scheme to use it to hone the small end of a rod, but I don't remember where the extra 0.106"–0.108" (i.e. needle-jet size) came from.

It "only" made it to 107 ℉ yesterday, ending a record-breaking seven-day stretch of temperatures above 110 ℉. Although I tried to stay inside as much as possible, a few essential outdoor chores sapped my strength so moving mandrels from one slot to another was the only work I managed to accomplish in the garage.

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A search for 'rubbing compound' on Amazon gave "over 2000 results," with the first four products described as:

"cleans and restores - removes deep scratches and stains"
"professional rubbing compound"
"clear coat safe rubbing compound"
"ultimate car scratch remover - paint & polish restorer"

There's no clue from those descriptions which are coarse (and, if so, how coarse) and which are fine, nor if more than one grade of coarse and fine are needed. Searching for 'polishing compound' wasn't of any help because that gave another "over 2000 results." So, next I tried a major brand, 3M, where on their web site they list 15 coarse and 27 fine "polishing compounds."

Having reduced "over 2000" choices to 42 is progress, but that's still too many to deal with. Thankfully, 3M also included a link to their "Paint Finishing Guide" which is a roadmap to their relevant products. From that roadmap I assembled a list of six of their products to use in the following order:

Defect removal (remove surface texture): 1000, 1500 and 2000-grit discs
Scratch refinement (refine scratches left after defect removal to reduce compounding time): 3000 grit disc
Additional refinement (to further reduce compounding time): 5000 grit disc (n.b. 5000 grit ≈ 3 microns)
Compounding (reduce sanding scratches): Perfect-It™ EX Rubbing Compound
Polishing (remove swirl marks from compounding): Perfect-It™ EX Machine Polish
Swirl elimination (eliminate fine swirl marks): Perfect-It™ Ultrafine Machine Polish

The above compounds/polishes aren't the only ones of their 42 that are made for paint but, thanks to their guide, they are an appropriate set of three in their Perfect-It™ "system" that have the necessary difference in grades. This information is very useful, for me, at least, for any future paint work when I'm concerned with achieving the best possible finish. Which is why I took the time to write this information.

The three photographs in the following composite were taken under identical lighting.

[Linked Image]

The photograph on the left was after manually using 800 grit paper on a semi-rigid block (which was followed by another short session with 800 to hit a few spots I had missed), and the middle after 2000 (in between were 1000 and 1500). While the 800 left a matte finish, it can be seen that the 2000 was fine enough for specular reflections from the fluorescent lights to start coming through the diffuse background. The photograph at the right is the same as in the middle, except with a small patch near the top that I hit for less than 2 seconds with Turtle Wax "Rubbing Compound, Heavy Duty Cleaner" ("Contains powerful abrasives which may remove paint if rubbed on too forcefully") applied with the 2400 rpm pneumatic polisher/buffer. Although the reflection of the light fixture is blurred in the photograph, it's actually quite sharp in real life. The blur is because the paint in that patch is so shiny that the reflection is significantly overexposed.

To apply the rubbing compound I used a wool pad as suggested by 3M at this "compounding" stage. However, they also point out that wool pads are aggressive and leave relatively deep swirl marks that later will have to be removed by additional time spent polishing. As an alternative they suggest using their foam 3000 and 5000 discs followed by applying the rubbing compound on a foam, rather than wool, pad. The end result is the same either way, but overall using the discs makes things "easier and faster." That certainly would be an advantage when having to deal with an entire car, but seems to be of minimal benefit for half of a motorcycle mudguard.

The left side of the next composite shows the mudguard after going over all of it with the rubbing compound for a total of not much more than a minute, and the right after an additional minute with Turtle Wax "Polishing Compound and Scratch Remover" ("Contains mild abrasives").

[Linked Image]

I applied the "Polishing Compound" with a foam pad, as suggested by 3M at this "polishing" stage. Although the image at the right is darker, that easily could be because auto-exposure has a difficult time when dealing with large areas that are either dark or light, so it's best to judge the difference between the two by the sharpness of my reflection (yes, I know, I always look sharp, but I'm referring to the level of detail). It should be clear that the polishing compound made a visible improvement in the detail in the reflected image. I assume something like 3M "ultrafine" compound would make the paint even shinier, but shinier would be out of place on the Ariel, and just waxing it will make it look even better than it does now. However, I won't wax anything until I've used the Turtle Wax polishing compound on both mudguards and the fuel tank.

Maybe I should say again that I'm not necessarily recommending anyone else repeat what I did when repairing the dent in this mudguard, because a professional could well dismiss everything I've written as amateurish nonsense. However, I'm quite happy with how it turned out so these posts over the past couple of weeks are to remind myself how to proceed the next time I need to repair a dent, or just paint a motorcycle part.

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The trick will be to sand a "ramp" near the edges of the new paint to make it smoothly meet the old paint without at the same time removing 0.005" of the old paint (which might not even be that thick). However, I'm not the first person who has had to deal with this issue so I'll do a bit of research to see how to approach this


Instead of a hard taped Edge , which adds a paint build edge .
hold a cardboard template an inch or 6 " above the paint area .
paint overspray will drift and feather around the template , softening the paint blend
and eliminate the hard edge .

you don't want to go to the extreme that the blended overspray drys as eggshell
Before blending , so it pays to practice , the paint , the day , and the distance
that the template is held away from the work .

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