Overboost

I touched on this in another thread, but wanted to start my own to discuss it further. When using my 5" backing plate and 6.5" LC pads, I can stall the pad out with light pressure. I've tried varying my speed from 4-6 on the PC, but it still seems to happen. Going off of the instructions on the polishes I use, such as M105/205, and D300/301, they mention running at a slower speed.

Anyone else experience this, and what can be done to get better correction from the PC with this? I've considered going to a smaller pad size per some recommendations on Autopia, or even picking up a rotary and learning it, while using the PC for wax/sealant application.

Right now, these are what I'm working with:
http://www.autogeek.net/porter-cable...cessories.html

http://www.detailedimage.com/Meguiar...nus-P519/6-S1/

FromZto5

This is correct. The larger the pad, the harder it is to get even pressure all around the surface of the pad, resulting in less than ideal correction on the outer edges.

The best pad size to use on the PC is a 5" pad, with 4" or 4.5" backing plate.

Overboost

That's what I've been experiencing. I'm confident my technique is sound, with proper arm speed, pressure, and pattern, but it just took forever to get mild correction when it seems like others can knock it out much quicker.

FromZto5

Right on, Overboost. So imagine if you will, how much better correcting abilities are on a 5" pad vs a 6" pad on a PC right?

Now multiply that by 2 again, and that's how much BETTER a Flex 3401VG is. That's why I migrated to that tool. It's got the power of a rotary, but the safety of a DA. I can correct in almost 1/2 the time, with MUCH MUCH BETTER results... as in, after an IPA wipedown, surface is 100% swirl/scratch free.

PC is good when starting out... but when getting serious, migrate to a Flex or a Rotary (I just don't like rotaries... personal choice).

Overboost

I'm just wondering if my attempts to get more serious are going to push me away from the PC. All signs are pointing that way right now. I may just bite the bullet and go down to a 5" pad setup for everything. I think my pads are on their end of life anyway, so it's now or never.

FromZto5

You hit it right on the head. Yes, as I got more serious with paint correcting (for my business), the PC just wasn't meeting my needs anymore. It was taking a LONG time and several iterative passes to get the level of correction I truly wanted. And of course, you know, time is money. So I migrated to a Flex. I do want to get a rotary soon too, but maybe someday.

Don't get me wrong, the PC is great, esp for those just getting into the hobby.... but the Flex is just so much better

Right now, I only use the PC for application of glazes and sealants, and liquid Nubas... no correcting. Maybe a very very light correction I'll use it once in a while.

Overboost

Good to hear. I know the Flex is a bit more than the PC, but if it's really that big of a step up, maybe I'll consider it. It has no trouble with the 6.5" pads and getting good correction in time?

Just as a reference, how long would you say it takes to get a one step correction out of a hood on a Mustang?

AlsCobra

Honestly man. The price of the flex will pay for a pro to do my car next time. So if just for a personal vehicle, prob better off contributing to another working man's family instead of stepping up any further than I have done already.

Overboost

I see a FLEX 3401 DA is $320 on Autogeek. Yes, it's expensive, but at the same time you could probably sell your PC and recoup some of the funds from that. Or, if you plan on doing more, keep it for LSP application. I don't need to buy additional pads and backing plates since I have them, so the up front costs aren't as severe as they were with the PC.

Edit - apparently the backing plates are unique to the Flex, so I'd have to buy something other than the 5.5" that comes with the unit.

MarcHarris

It sounds like you need to first and foremost increase the size of your backing plate. If you're in fact using a 5 inch backing plate yet 6.5 inch pads, you're not going to get the results you're looking to for several reasons.

First off, using an undersized backing plate will give you less cutting ability. The effective correction area of your polishing is the same size as your backing plate rotating (a bit bigger than the 5 inches because of the orbiting "throw" length). Additionally, a pad will lose rotational power with an undersized backing plate as the pad absorbs too much of the energy, which is exacerbated by the use of thicker polishing pads.

Using a larger backing plate will not only give you a larger effective polishing surface because you'll have more pressure over a larger area, it will also be more effective as a larger amount of the pad will be properly secured meaning the energy of the machine is more effectively put down to the paint.

To put it in other car guy terms: think of it as using skinnier rear tires on your Mustang. What you really want is to maximize the contact patch while keeping the PSI at a rate that more of the energy is transferred from the engine to the pavement. Throwing some 205 series tires on your rear end doesn't change the vehicle's power output, but it will certainly change your acceleration.


Additionally, if anyone is interested in a very lightly used Flex DA, let me know and you can buy mine.

FromZto5

Yes. The Flex does not use a counterweight for rotation, but uses forced rotation. So it doesn't get bogged down by pressure, etc. It just turns and corrects... if you look at the gearing behind it, it's a gear within a gear. So yes correction is much faster, almost double the time. I wish I had a link to that video showing a side by side correction, one by PC, one by Flex... The Flex was done in less passes, and had achieved 100% swirl free correction, vs the PC which took longer AND didn't remove all the flaws.

To your other question, the darn Stang hood is SO big...lol. From the light correction I did on my hood about 2 months ago, I had to break down the hood into 6 sections, and each section was about 5 passes, and that took about 5 minutes each section maybe??? so like.... 40 minutes total with pad assembly, pad priming, and cleaning? Not too bad. Now remember that's just one step, meaning one type of pad and one type of polish. If you go over that again (which is recommended...usually want at least a 2 stage method) that will be 1 to 1-1/2 hours obviously.

You're right, it's pricey...but as the saying goes, give a man a fish and he eats for a day, but teach a man to fish, and he eats for a lifetime.

So what happens when you get swirls again? or have to do another car? etc etc... having a Flex will just make it that much easier. No wrong answer here... I just love tools. Just like why do we invest in nice Craftsman tools? Because they last forever and get the job done nicely

FromZto5

Flex just recently introduced smaller sized backing plates. I don't have them, as I use my 3" Griots DA for small hard to reach areas...otherwise, 6" Flex does me just fine.

And yes, the Flex backing plates are different from PC's.

Right on...

That's the BENEFIT of using a larger sized backing plate with an appropriate sized foam pad (meaning the difference in diameter between the two is small). It definitely corrects better... but the DRAWBACK is that the chances increase of accidentally damaging paint by inadvertently allowing the backing plate to rub up against paint (I've seen someone do this), esp on severely curved surfaces). So just be careful. If you know what you're doing, no issue of course. Just take your time.

AlsCobra

I hear ya. And the car is good enough that upkeep will be easy and less time consuming. But the fact that I spent an entire weekend on this project. To do it all over again, I would have paid a man. And just went fishing all weekend.

FromZto5

Well said

MarcHarris

True, but the chance of causing damage with a DA is quite slim, and you have to use the machine incorrectly / not be paying attention to hit the paint with a backing plate.

For smaller area, I'd found the rotary to be nicer many times because of the absolute control and smooth nature of how it works. A normal pad doesn't always contour to curves very well, for example look at the gap between the middle of the pad and the paint:




To counter act this, I used a less aggressive pad (softer and more pliable to contour) paired to an undersized backing plate (5.5 inch pad with a 3.5 inch backing plate) and prepped it with polish to include the pad's sides:




Which allows for better control and more thorough polishing:






Of course at times you're just best at using small pads with a "correct" backing plate size as well:

FromZto5

Marc,

Your pictures are PERFECT. Yes, to someone who knows what they're doing and IS paying attention, this should be no issue. I use appropriate sized plates and pads always, despite the contours of the cars I work on. I just thought it was best to warn the guys on here (who are not as familiar with buffing as you and I) to just be careful.

But yes, I agree with you 100%. By the way, the technique you do is EXACTLY what I do, just minus the rotary as a tool... Someday, I will use one. I just haven't had the need, just yet. The holograms worry me. I know when I get good at it, should be no big deal... but for now, I feel I have a very good grasp on my 2 DA's.

AlsCobra

So Marc, answer what I was doing wrong. On a final polish pass, if I let the pad spin kinda freely, I would get some burnish type swirl in it. If I kept spinning to a minimum, it would come out very clean. Wouldn't think that the pad and polish would burnish at all. Dunno.

FromZto5

EDIT: You are SO lucky to work on a Carrera GT!!! lucky SOB

The best I got to work on was a Porsche 911 once.... like a 2001 or something. Still nice... but just a regular 911.

MarcHarris

I agree with your comments fully, though I'd recommend not purchasing a rotary unless you have a need for one. I now use a rotary on less than 10% of cars I do, and even then I don't use it for every step most off. The same way you don't use your Flex DA for every area or step for all cars. It's all about results, and as long as you can get them - you're good


Sounds like more of an issue with the type of polish you were using more than anything honestly. Picking three random polishes and hoping they work perfectly is like picking three random tire sizes and hoping they fit your wheels.
It's not that the products you used CAN'T achieve awesome results, it's more of a matter that not all polishes are equal in cut and finishing ability. What works perfect on one car type might not work at all on yours. The fact that you could see a difference when using different speeds / pressure speaks volumes of your ability to access your paint and make the needed adjustments to get the desired result.


Regular 911? LOL
Pretty nice car to work on - I love their paint quality. A 2001 would be a 996 body style which some Porsche enthusiasts seem to hate, but I know I'd take one if someone wanted to donate

The CGT is from our latest write-up and was a huge PITA. We ended up spending over 30 hours (with two guys working...) on her to get her looking correctly.

Title pic:




Thickness measurements were quite consistent which was nice...




...unlike the amount of sanding scratches combined with ultra hard clear-coat:




Still she ended up nice

Overboost

Marc, what's your go-to polisher right now if you're not using a rotary? Just curious what you find in your hand most.