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View Full Version : Is it really that hard to block a 55 Chevy laser straight????



DocHarley
07-23-2015, 04:52 PM
YES IT IS FOR ME!!!!! :(

I'm having a hard time blocking my 55 Chevy doors and quarter panels laser straight. I've finished the fenders, hood, trunk lid, roof and they look great IMO but just can't get the rest. I'm starting to think maybe I'm sick of sanding and have no patience left. :sad:

I have every size long block available but no luck using the same technique as the other panels, which like I said look great so I must kinda know what I'm doing. I'm now trying to use a long piece of 1/2 PVC the width of my doors, the problem I notice is, when I apply pressure on the ends it makes the center bow out therefore no contact with the panel in the center, guide coat will sand off only where I apply pressure on the PVC which is on the ends. One of my friends whos never sanded a panel is his life said try sanding vertical to remove the waves. Hum??

So my question is, have any of you pros used PVC or any other tool/trick you might want to share to help me, specially on the looooooooooooooooong quarter panels? It would be greatly appreciated. :geek:

chevynut
07-23-2015, 05:26 PM
The doors and quarters aren't straight to begin with. They have a crown to them. I measured the crown on my Nomad doors once and I think it was around 3/16". My sedan doors are a little straighter, but still around 1/8". I think using anything longer than a 16" block in them is wasting your time. Bock at a 45 degree angle with the sanding block level with the floor. If the guide coat is gone, it' straight. Don't block vertically!!! And also, don't press too hard or you'll deform the panel when you sand, and you'll never get it straight.

Rick_L
07-23-2015, 05:47 PM
You are probably trying too hard.

If the ends of the block are digging in, you are using too much pressure on it - you are bending the block. You also may be using too fine a grit on the paper. What you should be doing is applying less pressure and letting the paper do the work. I usually do my long block sanding with either 120 or 180 grit.

1/2" pvc pipe is probably too small. Try 2".

I use one of those soft foam blocks with the rods in it, 17" length. Forget the name of them. Or the harder foam "Durablock" will work. I do use pvc pipe for a block sometimes but normally only for leveling filler, rarely for any "finish" sanding. When I have a concave area to sand, I usually wrap pipe insulation over the block and use a psa type paper applied to the pipe insulation.

Good luck, hope this helps.

Edit: I looked up the name of the block that I use. It's called an "AFS" block. Adjustable Flexibility Sander. Google it.

Maddog
07-23-2015, 05:54 PM
Good advice from Rick, especially about trying too hard. Experience and technique is all it takes, they come with time. I would forgo the "trick" items and just get good with a 12"- 16" or so block.

MP&C
07-23-2015, 08:20 PM
We did a couple sessions of priming/blocking the door to the quarter and to the fender, all installed on the car. After this, more primer and put a perimeter of tape on the door skin. (don't need it on the window frame, door skin only. I was a bit unclear for Kyle....)

Now block again, and the tape allows you to block the door and keep off the edge.


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%202995.jpg


I don't stick with 45* angles, if you want to keep a long direction flat, you need the long block to better follow that direction. So change up to some sharper angles, about 30* off the long direction every now and then. Work one end to the other, consistent spacing, consistent angle end to end. Then change to opposite, etc.

Once done, and the inner part is good and blocked, now remove the tape and GENTLY block to the edge, taking care to not pull down at the edge and round things back off again. Whatever hand is holding the block make sure it is minimal pressure and stays on the door skin. In other words, no pressure pulling down past the edge. One other point, to keep the inner end of the sanding block from sanding out all your hard work in the center of the door, put a wrap of tape around the end of the sanding block that is towards the center of the door. This helps that end to glide across the center of the door without cutting primer there.


Now, see the red AFS block sitting on the shear? I believe it is a 27". I wouldn't block one of these doors or quarter for that matter with anything less. Smaller is going to follow any waves and not get rid of them as easily. Put a rowboat in the Atlantic Ocean and it follows the waves. Now compare that to an Oil tanker, and you have something that stays straighter. When you get things blocked "crown flat" to your satisfaction, change to shorter blocks when you start wet sanding..


You've brought it this far, keep at it!

MP&C
07-23-2015, 08:40 PM
And after primer tonight....


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203013.jpg

LEE T
07-24-2015, 07:04 AM
I also like the AFS block, it is made of foam to conform to the surface, and a metal plate on the bottom for hard block performance. You just have to trim any part of the foam that may not let the metal plate lay flat. This door was epoxy primed, sanded, and reprimed with SPI black epoxy.

http://i747.photobucket.com/albums/xx119/from7/Nomad/6e6af092-e570-497d-910a-8ce62027bc78_zps9e46681c.jpg

DocHarley
07-24-2015, 07:06 AM
I think that's my problem (keep the inner end of the sanding block from sanding out all your hard work in the center... I never thought of that)(applying too much pressure) because after blocking i'm always low in the center.

Thanks so much for all the great advise, I will post my results.

Robert, doors look awesome, What's your address so I can ship mine to you, or fly you, Rick and Chevynut down here so you guys can do my quarter panels, bet it would only take two days, then after your done we all go deep sea fishing in my boat. :) You like Tuna?

DocHarley
07-24-2015, 07:08 AM
Lee T, I'm using the AFS 28" sanding block, what do you mean "trim the foam"?


Update:

Never mind, I got it and yes I did need to trim some. Thanks!

chevynut
07-24-2015, 08:08 AM
I have a 24" K-Block that I've never used. I always felt that too long of a block was too hard to apply uniform pressure to and that seems to be what DocHarley is struggling with. I may have to give it a try though, keeping sharp sandpaper on it.

On another note, the next car I do (if I live long enough) is going to have a 1-step sandable epoxy like SPI or similar. The 3-step stuff is just too much work.

LEE T
07-24-2015, 08:48 AM
The gloss on the black provides all the guide coat you need, but I like to put white epoxy on first, so I know how close I'm getting to the metal---and I want to break through the black on all the panels so I don't get it too thick.

http://i747.photobucket.com/albums/xx119/from7/Forum%20photos/26eb5448-2f26-4375-898a-f2a997c9d155_zpso9yufcns.jpg

chevynut
07-24-2015, 08:59 AM
Lee, that's a good idea to put white first. Is that also SPI epoxy? I put PPG DPLF down first so it helps me know when to stop. I then put Slicksand over that and blocked everything flat. The final coat is K36. If I accidentally go to metal, I put epoxy on again but I actually think that's overkill for small spots. K36 can go directly over metal too. The SPI seems to make it so much easier. I still have to finish blocking my Nomad with the K36 primer. Soon, I hope. ;)

My painter uses a Clausen product that's a zinc-enriched, waterproof, high build polyester primer. He uses only this primer from bare metal to topcoat and he's painted several $1 million+ cars. He's been using the stuff for many years and he says he's never had an issue with it and it won't shrink, crack, or cause other problems.

LEE T
07-24-2015, 10:10 AM
Yes, white is SPI epoxy. I can't comment on the Clausens

DocHarley
07-24-2015, 10:29 AM
Door is done!

Robert, you were correct I was removing 2k from the center the whole time while doing the left, center and right end of the panel resulting in a dip/wave in the center, if that makes any since. :confused: So I used your trick and it worked great! I was also appling too much pressure. Thanks Robert, Rick, Chevynut and LEE T for the great advise!!!

Here a pic that's not too good, the water I used to make it shine was heavy making it look like waves but trust me it's laser straight!!!! :rolleyes:

http://i206.photobucket.com/albums/bb214/DocHarley/IMG_0234.jpg (http://s206.photobucket.com/user/DocHarley/media/IMG_0234.jpg.html)

MP&C
07-24-2015, 08:04 PM
looks good!

DocHarley
07-25-2015, 11:02 AM
Thanks Robert!

MP&C
07-25-2015, 04:08 PM
I think that's my problem (keep the inner end of the sanding block from sanding out all your hard work in the center... I never thought of that)(applying too much pressure) because after blocking i'm always low in the center.

Thanks so much for all the great advise, I will post my results.

Robert, doors look awesome, What's your address so I can ship mine to you, or fly you, Rick and Chevynut down here so you guys can do my quarter panels, bet it would only take two days, then after your done we all go deep sea fishing in my boat. :) You like Tuna?

Where does the fishing boat leave out of?

DocHarley
08-01-2015, 05:22 AM
Where does the fishing boat leave out of?

Fort Lauderdale, Florida

Do a weekend trip to the Bahamas, catch lots big game fish. Only "catch" is, my quarter panels have to be perfect, just one imperfection and I use you as bait. lol

MP&C
08-04-2015, 07:15 PM
Just to add some more insight to this thread, we had done some blocking with the 27" AFS and seemed to have two high spots with a low in the middle of the door..

Note the high areas marked by the green tape...


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203024.jpg


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203026.jpg


Now we can see that as the sander is moved to the left, the left portion of the AFS is over the high spot on the left, and a bit more movement and the right portion of the AFS will start dropping into the low void. Effectively, this is still cutting material out of the low, keeping it low.


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203028.jpg


Looking at the next size up, a 36" AFS....


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203019.jpg


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203020.jpg


Here we can see this one does a much better job of spanning the high spots and staying up on top, for a more effective job of knocking down the highs and leaving the low in the center alone...


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203029.jpg


After a few horizontal passes at slight angles, like so with the 36".......


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203018.jpg


We follow up with some vertical passes at slight angles with the 27".... all rods removed to better follow the contour.


http://i5.photobucket.com/albums/y167/rmccartney/1955%20Chevy%20Wagon%20Restoration%20Album%204/Picture%203030.jpg

chevynut
08-04-2015, 08:32 PM
I didn't think you were ever supposed to sand vertically. Do you have a 48" block too? :) :)

MP&C
08-05-2015, 04:44 AM
I'm certainly no expert and I'm sure there's someone somewhere that can provide valid reasoning to support that. But these door skins, much like most of the other body panels, have a noticeable crown in the vertical direction. Sand enough in the horizontal direction and you will be adding flat spots, despite the overlap you may use. The other point to consider is the angle of your cross hatch. Here is a sample of a 45....


http://i5.photobucket.com/albums/y167/rmccartney/Misc/Cross%20hatch%2045.jpg


In this example let's go on the assumption that the spacing is approx. 1" apart. Now if we use a 30* angle on the cross hatch, and maintain the same one inch spacing in the horizontal direction, it gives us a closer overlap in the vertical direction for a more effective blocking session to remove those "flat spots" being added by a flat sanding board.


http://i5.photobucket.com/albums/y167/rmccartney/Misc/Cross%20hatch%2030.jpg


Where this has a better overlap and does a better job of getting rid of those flat spot issues, you can still feel the ridges in the primer after a session of horizontal only blocking. By performing a few vertical blockings, it cuts those ridges down, but also now look at the overlap... which should give the best results in blocking the panel.








http://i5.photobucket.com/albums/y167/rmccartney/Misc/Cross%20hatch%20horiz%20and%20vert%2030.jpg


Perhaps this method isn't suitable for all panels, but for the door removed from the car, it did well in removing the ridges..

chevynut
08-05-2015, 05:18 AM
Robert, looking at your crosshatches I think I sand more at 30 degrees than 45 degrees. I think the point is you should sand at an angle, not straight.

DocHarley
08-05-2015, 05:49 AM
I never sanded vertical and may be the reason it took so long to get my doors straight. Will give it a try on my quarter panels, hope it helps cause these dogs are fighting me big time. Thanks Robert!

MP&C
08-05-2015, 05:51 AM
Robert, looking at your crosshatches I think I sand more at 30 degrees than 45 degrees. I think the point is you should sand at an angle, not straight.


True. And even though the sanding blocks in the pictures are shown as parallel to the edge, they are pulled at a slight angle to kinda sorta match the 30* cross hatch pattern shown. But in some instances, I have also turned the sanding block at a slight angle to parallel and pulled it straight to the panel. All depends on the shape of the panel that you have to contend with. As long as your "cutting edge" is at an angle to the pull, all is good. I should also point out that the vertical blocking was using minimal pressure, only enough for the sanding block to match the contour. Then, it was only used enough to smooth the ridges we could readily feel..

Rick_L
08-05-2015, 07:55 AM
To my way of thinking, as an extensions of the thoughts already said - it seems to me that if there's more crown vertically than horizontally, which is the case on most doors and quarter panels on any car, especially a 55-57 - then sanding vertically is the most likely way to create low spots because you have to get the block, especially if it's a long one to conform to the contour. So from that line of thinking, the 30º horizontal crosshatch is also better than a 45º crosshatch.

The other half of this is that you never want to make too many consecutive strokes in one place (maybe none), no matter what your pattern is.

The hardness and flexibility of the sanding block also plays into this.

MP&C
01-10-2016, 08:10 AM
Here's a video taken yesterday using the 36" AFS sander. Note how the sander is grasped and the fact that this promotes letting the sandpaper do the work without "leaning" on it. Applying downward force through your palm to get the job done more quickly runs the risk of deflecting the sander downward at that point, causing low spots...



https://www.youtube.com/watch?v=tZwM1m1h09I

Rick_L
01-10-2016, 08:49 AM
I think your point about letting the sandpaper do the work without a bunch of pressure is very important. No matter how you build it, a flexible long block won't sand evenly if you push hard on it. And if it's rigid, it only sands in the center or on one end. Pressure may work when you're first leveling the filler, but not as you get closer to the finished contour.

DocHarley
01-12-2016, 03:25 PM
I apply way more pressure then in your video. Maybe why it takes me so long to make a panel straight. Thanks for the info.