67 Mustang door help, blocking stage

[cstrom72]

So I'm on my second round of 2k on these doors. They look smooth as glass after i spray but as soon as I start blocking I find the same low spots. My main areas of concern are the front lower corners. There were patches done by someone else at some point but I'm having a hard time getting it perfect.
If I need to add some filler at this point should I just hit the area with a 80 grit on a DA? It shouldn't take much filler I don't think. But maybe another couple coats of 2k would do it? I guess I don't know- starting to really get frustrated. Once step forward = 2 back lately.

 

[DATEC]

Putting filler on now would depend on just how many coats of 2k you have on and how thick (mils), if it were Epoxy I wouldn't be concerned about putting it over top. How long has it been since you primed each layer?
You might have to remove the primer in the low spots and feather back the primer and fix it properly if it's that bad.
Primer is only ment to aid in getting things straight not to replace the need for filler and if 2coats and it still isn't straight then more filler should have been used unless you are block sanding too much. How does it feel? How does it look when you wet it down with wax and grease remover?

 

[MP&C]

I don't know if this applies to your situation exactly but maybe my lessons learned will help out...

I was having some issues in blocking, and needed to kinda step back and try to figure out why I consistently had a low in the center of the doors...

We had already done a couple sessions of priming/blocking the door across to the quarter and to the fender, all installed on the car. After this, with the next session of primer we put a perimeter of tape on the door skin. Now with blocking separate from the body, the tape allows you to block the door and keep off the edge to prevent losing your match to the fender/quarter.

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 alternate to passes in the opposite direction.


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 to show the importance of the long board, and what was part of our problem..


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.. No matter what we did.

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

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 with a bit more movement that direction and now 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.

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

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...

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

We follow up with some vertical passes at slight angles with the 27".... all rods removed to better follow the contour. Then alternate back to the 36 and another horizontal session..

Hope this may spark something to help out...

 

[Bob Hollinshead]

sometimes it is best to make your first strokes in a straight line with the length of the panel making it straight in relation to it's length, this is what you see when you sight down the side of the car. Then switch to an consistent X pattern from one end to the other to remove all the little flat spots that are created. Different contours require different techniques for sure.

 

['68 Coronet R/T]

Make sure you are not pressing too hard on the sanding block and flexing the panel. You will know if you keep putting filler on and sanding it off and the low spot is still there.
Use coarse grit when getting the panel straight and change the paper as soon as it quits cutting - it makes you feel like you're wasting paper.
Another thing I will do is use an inline air sander and just let the weight of the sander do the work.

 

[Bob Hollinshead]

Most of your blocking should be done with the panel on the car if you are after perfection-things sometimes change when they are laying on the stand. I block the car as a complete assembly then blow it apart for final prime.

 

[Chris_Hamilton]

I don't know if this applies to your situation exactly but maybe my lessons learned will help out...

I was having some issues in blocking, and needed to kinda step back and try to figure out why I consistently had a low in the center of the doors...

We had already done a couple sessions of priming/blocking the door across to the quarter and to the fender, all installed on the car. After this, with the next session of primer we put a perimeter of tape on the door skin. Now with blocking separate from the body, the tape allows you to block the door and keep off the edge to prevent losing your match to the fender/quarter.

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 alternate to passes in the opposite direction.


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 to show the importance of the long board, and what was part of our problem..


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.. No matter what we did.

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

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 with a bit more movement that direction and now 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.

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

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...

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

We follow up with some vertical passes at slight angles with the 27".... all rods removed to better follow the contour. Then alternate back to the 36 and another horizontal session..

Hope this may spark something to help out...

How do you control the center of such a big block? I've tried the "marine" style durablocks and had a set of the same ones you are using and I found the when I blocked it would remove more material where my hands were and less in the center. With such a long blockI found it impossible to get even pressure across it. IMO they are more trouble than they are worth. I have found that the longest (for me at least) block I need is a 17 inch durablock. I also like the 3M Yellow plastic long board that I slightly "modified". I use a 36" machinist's surface plate that I cover with sandpaper and occasionally true my blocks (especially durablocks) with. You'd be surprised how the durablocks will warp/deform after some use.

 

[cstrom72]

Putting filler on now would depend on just how many coats of 2k you have on and how thick (mils), if it were Epoxy I wouldn't be concerned about putting it over top. How long has it been since you primed each layer?
You might have to remove the primer in the low spots and feather back the primer and fix it properly if it's that bad.
Primer is only ment to aid in getting things straight not to replace the need for filler and if 2coats and it still isn't straight then more filler should have been used unless you are block sanding too much. How does it feel? How does it look when you wet it down with wax and grease remover?

I don't think I'm blocking too much. It's just the front corners where the patches were. I think I'm going to add a little filler down there. Would the best procedure be to hit that while area with 80 grit? It's been over a week since I sprayed thev last coat of 2k.

Lots of good info there as well Chris-

I don't need much filler, just a skim coat would do it. Just was not sure how to prep it at this point

 

[Chris_Hamilton]

@cstrom72
best general piece of block sanding advice I can give is to be fanatical about blocking evenly. Meaning starting at one side working your way over covering the entire panel with approximately the same amount of strokes and then crossing that and working back. Don't make the mistake of staying in one spot for any longer than you stay any other area on the panel. Initial blocking always goes much easier if you use coarser sandpaper. I like 120 grit to start then I'll switch to 150 or 180 and then finally 220-320. Then I'll wet sand (scratches in one direction only) with 400-600 grit. Just kinda depends on the situation. Most of the time you won't get it in one shot. Usually it will take anywhere from 2-4 applications of primer, just depends on how rough it is.

 

[Bob Hollinshead]

How do you control the center of such a big block? I've tried the "marine" style durablocks and had a set of the same ones you are using and I found the when I blocked it would remove more material where my hands were and less in the center. With such a long blockI found it impossible to get even pressure across it. IMO they are more trouble than they are worth. I have found that the longest (for me at least) block I need is a 17 inch durablock. I also like the 3M Yellow plastic long board that I slightly "modified". I use a 36" machinist's surface plate that I cover with sandpaper and occasionally true my blocks (especially durablocks) with. You'd be surprised how the durablocks will warp/deform after some use.

That 3M yellow board will bow like a banana after a few years unless they changed the material, I drilled a hole through the handles on mine and inserted some allthread so I can adjust the straightness, but even then I just use it for roughing. I generally try to use a block that is at least 1.5-2X longer than the contact surface-how much crown the panel has dictates how much surface area of the block will make contact. If it's a long straight bedside or quarter panel a 36" block works really good. jmo

 

[cstrom72]

So where im down to epoxy/bare metal and first coat of filler in the front corner, can I hit that area with 80 Grit on a DA and do a skim coat of filler? I guess that is where i need to figure out before I can block anymore

 

[DATEC]

To prep the area that would be fine after that DA nothing I would block sand only. With a DA you can create more work and waves then needed without knowing it. The primer is softer then the putty and will sand away faster and easier if your not really careful. So I say hand block everything at this point.

 

[cstrom72]

So just hand block it with 80? Just want a good bite with the skim coat of filler

 

[DATEC]

You can prep with a DA if you want too or just ruff up that area with your hand using 80grt. Then spread your skim coat of filler and use a block by hand to get it straight.

 

[cstrom72]

Right on- Thanks!

 

[MP&C]

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...


[video=youtube;tZwM1m1h09I]https://www.youtube.com/watch?v=tZwM1m1h09I[/video]

 

[shine]

anytime you see a round spot of filler you sanded too far. you have created a crater. meaning you sanded down into the dent. try to keep all your filler square .

 

[Chris_Hamilton]

Don't forget the most basic, yet most important thing when blocking a panel or sanding filler.....your hand. You should use your entire hand not just your fingers. Your hand can feel even the most minute low or high spots in a panel. You can use a rag or cloth to help accentuate with feeling the lows and highs.

 

[true65mustang]

How low are your areas on the door skins? Are they with in an 1/8"? If not then I'd be posting close up pictures so that we can assist you better. There was a guy at a body shop I was looking at working at. He was working in a 65 mustang door. The doors were going to need 3/8" filler that's ain't gonna cut it!! I asked him if I could cut in and help him out. He was happy for my help and so was his boss. As they both knew that you couldn't use that much filler. I ended up using a grinder with a good backing pad and 50g disc. If you hold in up right and go up and down and let it float then it will start to sand and show you where contour is. Then after getting a metal picture you can do your rough body work and get it from there. A good hammer and dolly are a must don't cheap out and get a POS. The only Dolly's I like are Martins they are made in texas. I use the general purpose dolly all the time. For hammers you don't want a flat hammer. A low slight crown hammer is the most common. I love my vintage plumb 1427 cross peen. If you can find this or a 1427 proto on eBay I would snag them. Other things that will help are heat you may want to grab a map gas torch as well as a body spoon. If you get behind those doors if they are really low if would heat up that low area around the damaged area. Don't heat up a spot! When you do this you can then try spring hammering on the panel so light taps around the area an some times this will pop the panel into contour. If not heat it up use your dolly on the back side and press on the low area till you bring it up. Then tap around the area not on the low spot. if it's to hot and you hit the low area you will cave it! If you get the panel raised up to where it needs to be then have wet rag handy and quench the panel while still keeping pressure on the back side. This should lock that area in place. Also if you don't know this already don't tap on the dolly when your working on the panel that will make it fat. IF you do it hopefully you notice and stop or you can make it hard on yourself. If you listen to these few things you can make that panel nice! I went to nationals for auto collision repair and refinishing.

 

[true65mustang]

Don't forget the most basic, yet most important thing when blocking a panel or sanding filler.....your hand. You should use your entire hand not just your fingers. Your hand can feel even the most minute low or high spots in a panel. You can use a rag or cloth to help accentuate with feeling the lows and highs.

True use your less dominate hand also. Your less dominate hand is more sensitive to the above and below contour areas. When sanding let the sand paper glide and cut the filler and do the work for you. Also if your paper isn't cutting well get another sheet this will help you out with making less work for your self. Not always but some times when you sand and you hit filler when youve sprayed even coats of primer. That usually shows you above contour areas (high spots). This is because your block is hitting these spots first before the surrounding areas. When feeling the panel feel both directions. Most people fill a low area but they don't realize that there is a buckle in the panel. What some amatures do is fill the area anyway not knowing. And then sometimes the have happen to them what could be happening to you. You also want to make sure your base lines styl line and flanges are in proper shape other wise this will make fixing a small dent really a pain if you don't notice. Also using a dolly you stick it where it's low hit it where it's high.