Is it really that hard to block a 55 Chevy laser straight????

[DocHarley]

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.

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.

[chevynut]

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]

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]

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]

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.





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]

And after primer tonight....

[LEE T]

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.

[DocHarley]

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]

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]

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.