shaping and blocking on convcave surfaces

[AmadeusCharger500]

I have a 73 se. I am making the car a hard top. It used to be a vinyl top.  I puttied in the spacers for the louver windows and I am having trouble getting a smooth block pattern on the concave surface just behind the window. How do I get this to match the curve back to the quarter panel?

thanks

[Patronus]

I prefer dura-block boards, although there are some others we use with different properties. If its the area I'm thinking I would choose the small 1/2" thick rectangular size block. Even pressure, all the way across from one side to the other. I cannot stress that enough. If you're doing spots of bondo it's imperative to sand only on the bondo. Even then you will create a low around your work area. High-build primers now available make the final blocking a pleasure now-a-days. When color sanding I find it just as important to sand the panel in its entirety. One side to the other, back and forth, back and forth. All 17'-2" of her..

[sanders7981]

dura block all the way!  I used them on just about every contoured surface on my 69.  They work awesome!

[Dino]

What they said.

If you want to play McGyver, a smooth rubber hose is a good substrate for your sandpaper as well. 

[71green go]

Sure would like a better picture of the area you are doing...You say "puttied" in .....does that mean you just bonded in the area?........filled the gap ?.....tell me more of how and what you did as it sounds like huge potential for cracking later...would be a huge waste of time trying to make it look pretty now
steve

[b5blue]

A pack of "Soft Sanders" from Eastwood really helped me in some of tricky areas.     http://www.softsanders.com/

[el dub]

I use a 4 inch paint roller .

[sgt72charger]

I have a 72 im in the process of blocking too.
Just bought the complete set of durablocks from Eastwood along with a set of soft blocks.

My car used to be a vinyl top also.  What ive noticed sence ive started blocking it is there are "ALOT" of surfaces that you would expect to be flat that realy are rounded, thats where the soft block and lots of guide coat and a few layer of high build come in handy

[Dino]

I have a 72 im in the process of blocking too.
Just bought the complete set of durablocks from Eastwood along with a set of soft blocks.

My car used to be a vinyl top also.  What ive noticed sence ive started blocking it is there are "ALOT" of surfaces that you would expect to be flat that realy are rounded, thats where the soft block and lots of guide coat and a few layer of high build come in handy

There are no real flat surfaces on cars or any other vehicle for that matter as it would make the metal too weak and susceptible to 'fluttering'.  All panels have at least a slight curve to it so the metal has more tension and keeps its shape (or better yet goes back to its original shape, panels can flex quite a bit).  That's why on certain cars you cannot block the sides front to back and expect a smooth, uniform result.  They will show low spots at the panels edges because of the curve so the best way to sand those is one panel at a time.  The better cars (and most modern cars) have panels which curves complement the panels neighboring it.

[AmadeusCharger500]

I have a set of Dura Blocks and I was using the 7inch and also the cylinder shaped one, which I can't find for my picture. I substituted a small piece of conduit but for some reason this area is just boggling me.

[b5blue]

Had the same issue with my 70, that's when I gave up and ordered soft sanders.  What a difference in the odd curved parts of the body! 

[AmadeusCharger500]

Also here is a better pic, I have tons of pics from the work before and after just cant figure out how do downsize files to 200k.

Both sides were puttied in when I bought the car as a hard top, I am just installing the same way I found it.

[b5blue]

Yup even though different the same area on a 2nd gen. is tricky, a transition blend. I had a fairly large repair for my 1/4 windows area and could not get it smoothed proper.

[Canadian1968]

The area you are working on does not seem to be that difficult.  The concave area does not appear to be bad.  Careful if using a soft block as, a soft block can roll over high spots instead of knocking them down.

I don't think a soft block is need for that area, I would using a 6" hard/ dura block and just take your time.  Long even strokes, always on an angle remember ! You never want to go straight with curve, or concave area. YOu will create flat spot on a curve and ridge in a concave area.

YOu want to make an "X" with your sanding marks. Make your strokes as long as you can and work with the shape very little pressure is need , you should concentrate more on following the contour than anyhting. There is a bit of finess to it no doubt. 

[AmadeusCharger500]

Yes I agree, I think I did a few strokes from top down tilting the long block, I was using the 10 inch one. This left the curve with a high spot that I could feel but not see. So I wrapped a heater hose and did it again this time with an x pattern. So either it was the soft heater hose backing or the xpattern is finally making a difference.
Im also interested in how does a person know what is exactly the correct depth of curve in this area. I feel like Im making it up as I go along sometimes.

[Dino]

For those shapes I always have used a concave wooden block, not a soft block.  But you really need to look at how the panel flows and get the best fitting block.  Trial and error.  The X pattern is a guide, you need to go in every direction possible and never ever exert pressure on the block.  Let the sandpaper do the work.  If you exert force that makes the panel flex, it'll never be right.

[Canadian1968]

How deep it should be? I think looking harder than you need to . You just want to make nice even transition . The body is ultimately goin to decided how deep you can go of course .

You just want it flow and look natural. Get it blocked to where you think your happy . Have a can of spray primer and spray the area so it is uniform colour this should like see what it will look like. If there is not enough shine wet a rag with some soapy water and wipe down the area that will give you temp. Gloss to look for any imperfections