color sanding concave body lines.

[DanMcG]

I was wonder the best method for concave body lines. I've read using a 3" sander and doing it by hand. Is there a reason you can't double up on soft interface pads or get a thick one?
I'm dealing with a 85 chevy truck and the horizontal bodyline is a fairly large radius, but I'm still uncomfortable running my orbital sander into it.
I'm using the Ultra buflex 2000- 3000 with their soft pad at the moment and if it was a little thicker, or had more flex I'd be more comfortable.

 

[Lizer]

What I use for this is a 1" diameter PVC, cut to whatever length you want (though I use about a 6" piece), and then take an old trizact pad and wrap around it, holding it with my fingers, to use as an interface pad. Then I put my wet sanding paper over that, also holding it my fingers (because the trizact pad and sand paper wrap almost all the way around). Then the entire thing can just be dunked in your bucket to rinse.

 

[Dean Jenkins]

What I use for this is a 1" diameter PVC, cut to whatever length you want (though I use about a 6" piece), and then take an old trizact pad and wrap around it, holding it with my fingers, to use as an interface pad. Then I put my wet sanding paper over that, also holding it my fingers (because the trizact pad and sand paper wrap almost all the way around). Then the entire thing can just be dunked in your bucket to rinse.

@123pugsy gave me similar idea of using 3" ABS pipe in same fashion.

 

[ksungela]

I've used PVC pipe or this https://www.amazon.com/Dura-Block-AF4404-Black-Round-Sanding/dp/B004BBAMVQ
No bucket of water. Squirt bottles only.

 

[MikeK]

double up on soft interface pads or get a thick one?

Their not for this. More 'minor' difference planes. Way too much radius at the bottom of it for a DA. Maybe for bodywork roughin.
The pvc pipe works, just use Sch 40 and make Sure It's Flat/True because I've seen even Sch 40 bowed.
I used a Dura Teardrop on the 85 I did. Love this one. Great block.

https://www.amazon.com/Dura-Block-AF4406-Black-Sanding-Block/dp/B007VTSVTA/ref=asc_df_B007VTSVTA/?tag=hyprod-20&linkCode=df0&hvadid=309813767497&hvpos=&hvnetw=g&hvrand=10116236292133289646&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9025852&hvtargid=pla-557445563239&psc=1

 

[Chris_Hamilton]

Sand up to the line, never on the line or you run a big risk of cutting through or burning through when you buff.

 

[RosharonRooster]

Concave....yeah, pray for me. I'll be buffing this thing in about a year...

 

[Lizer]

I've used PVC pipe or this https://www.amazon.com/Dura-Block-AF4404-Black-Round-Sanding/dp/B004BBAMVQ
No bucket of water. Squirt bottles only.

I use a large sponge that I hold above the work area and slowly let water run down from it. I have a squirt bottle I use too, but the constant trickle of water from the sponge keeps the work area cleaner and paper cleaner so it doesn’t load up and start making bigger scratches.

 

[DanMcG]

Thanks for all the suggestions but I don't think I want to use a hard block in the 1500-3000 grit range, do I? I'm only refining scratches.
I have the 1 1/4" round Dura-Block that I used on the primer up to 320-400 and a soft block with 1000 to flatten the peel and trash, but I'd rather not use it for this step, I think I'd want something soft.

 

[Lizer]

Thanks for all the suggestions but I don't think I want to use a hard block in the 1500-3000 grit range, do I? I'm only refining scratches.
I have the 1 1/4" round Dura-Block that I used on the primer up to 320-400 and a soft block with 1000 to flatten the peel and trash, but I'd rather not use it for this step, I think I'd want something soft.

Why not? I use Durablocks for all sanding all the way up to 2500, but it’s the small ones, and I would not consider it a hard block.

You wrap an old trizact pad around PVC pipe to act as an interface pad so it’s not a hard block, it is quite soft with the interface pad.

 

[MP&C]

What is the radius of the concave? I’ve used pool noodles for the larger areas.

 

[DanMcG]

It's at least a 6" radius but only a small arc segment, maybe 2".

 

[theastronaut]

Very thin plexiglass/lexan; it'll flex to match the curve. The hard surface works great to cut all the texture flat. Soft blocks will let the paper flex, it won't put pressure on only the high spots so you're not flattening the texture as much as possible. Once it's cut flat you can go to soft blocks for the finer grits since you're only refining the scratches at that point.

Concave areas magnify texture and ripples so blocking the clear flat precisely is extra important in these areas.

 

[DanMcG]

I guess the consensus is to stay out of the radius with a sander and do it by hand. Thanks for the guidance.

 

[MikeK]

Why I have 2 tennis elbow armbands. 1 for each elbow.
Funny how something so so ridiculously looking can actually work. Been wearing Them again now.

 

[Toolin]

What is the radius of the concave? I’ve used pool noodles for the larger areas.

I have used pool noodles with a 1/2" ID PVC pipe slid inside to stiffen and keep it straight.

 

[Lizer]

I have used pool noodles with a 1/2" ID PVC pipe slid inside to stiffen and keep it straight.

Crush two pills of viagra, put them in a bucket of water, soak pool noodle in it for 30 min.

You won’t have a limp noodle anymore. Trust me, I used to work for Pfizer.