Block sanding ?

Ok I finally got the cover blocked to 320 Lots of sanding.. I do have some sand thru's to the slick sand but overall it not to bad. They may get a little larger when I wet sand to 600. To me the cover is very straight. I know this is a tough question to answer just by looking at the pics, but do you think with these sand thru's I will need another round of epoxy, or will the epoxy sealer coat be enough protection.







I did have a little setback. I scraped the side of it while moving it. ARRGGG!. I sanded the damage with 80 and the surrounding area with 180. Tomorrow night I will spray 2 coats epoxy with my detail gun, and the some glaze, sanding, and more epoxy. I guess I'm glad it wasn't painted yet.



Thanks for the help guys.
 
I got my damage area repaired. Came out ok. Now I'm trying to decide to proceed with 600 grit wet, or spray 2 more coats of reduced epoxy say 20% then 600 wet. What do you guys think? Thanks.
 
As much as you have done to that, I would guess that it's ready to sand and shoot. Honestly I don't think those covers were ever intended to be perfect, and it's somewhat likely you will see some slight waviness return after a season on the hot sun anyway (sorry). Obviously none of us are there with you to say for sure, but it seems like you have already made it better than 99% of shops would ever do. The only question in my mind is if the brand of base you have will conceal the 320 marks. Most of the time, if you are sealing, 320 marks will be covered up, but it's not 100% for sure. Maybe the safest way is to put 2 more coats of epoxy on and this time don't touch it with coarse grits, just smooth it out with 600 and go. If you do this quickly enough, you don't even need sealer because the epoxy will still be "fresh" and the base will bite in and stick good.
 
crashtech;n77397 said:
As much as you have done to that, I would guess that it's ready to sand and shoot. Honestly I don't think those covers were ever intended to be perfect, and it's somewhat likely you will see some slight waviness return after a season on the hot sun anyway (sorry). Obviously none of us are there with you to say for sure, but it seems like you have already made it better than 99% of shops would ever do. The only question in my mind is if the brand of base you have will conceal the 320 marks. Most of the time, if you are sealing, 320 marks will be covered up, but it's not 100% for sure. Maybe the safest way is to put 2 more coats of epoxy on and this time don't touch it with coarse grits, just smooth it out with 600 and go. If you do this quickly enough, you don't even need sealer because the epoxy will still be "fresh" and the base will bite in and stick good.
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Thanks Crash. I appreciate the info. I have went overboard on this little project for sure. I went at it with a restoration attitude instead of a re-spray. lol. I probably should have junked it but I figured it would give me good practice for the Camaro project. It will probably have a few waves after next summer. My base is Prospray from Chad's and its Dark Toreador Red and has some metallics in it so I will go ahead and do the two coats epoxy and then run over it with 600 wet on a soft block. That color is a weird one. The sun has to hit it just right to see the metallics. Some days it looks burgundy and others it looks purple. I need to do a spray out card and see how it matches the truck. I have a trunk lid from my Camaro that I'm going to practice spraying base/clear on with some crossfire base and SPI Universal. I'm sure I will have more questions when I get to that point. Thanks, Russ
 
Getting ready to shoot some more epoxy on the cover to sand with 600. I was thinking about reducing the epoxy say 20% so that It would lay down a little smoother. I'm also trying to catch the lid up to the rest of the cover, I've been working on the repairs to the underside of the lid. Most likely I will still use a sealer because of my work schedule, I don't get much garage time. I have read in the archives that its never good to sand something and let it sit. I'm guessing we are talking about long term say months instead of a week or two? If I go ahead and go to 600 and it sits a week before I can seal it I guess I could hit it with a gray scuff pad?

Also when wet sanding I will be using one of those foam blocks that is double density. One side is softer than the other. I know at this stage I'm just refining the scratch, not leveling. I guess you would still use a cross hatch pattern. In some of the rounded curves I will still use my round durablock . I had some overspray that I wet sanded off with 400 and so far I think I like dry sanding the black epoxy. Its easier for me to see the progress. Thanks for the help guys this has been a big learning curve for me.

 
Some guys would say that if you let it sit for week, you should seal it yet again with epoxy for best adhesion. At our shop, we sand stuff right before it is to be painted, like no more than a day or two beforehand. The reason is because while you can do it like you say and hit it with a gray scuff pad, but you really have to get after it and expose some fresh material, and that takes time! So it's like doing double work.
 
One more crazy sanding question. I shot the cover with some reduced epoxy 20%, I sprayed it a little heavy in a few spots, overall not bad, It was getting sanded anyway. So I blocked all the smaller sections (sides, back, front) with my durablock ( dry 400 grit ) and they did great. I went to block the top with 400 and had problems. I used a 21 inch block (dry) and the paper seem to load up in just one spot or two and deeply scratch the panel. The scratch was definitely more that a 400 grit scratch. Sometimes I could sand several strokes before it did it and then sometimes I would make about 3 passes and it would do it. I would have to do a lot of sanding to remove them and I usually was putting more of these scratches into the panel at the same time. I also changed the paper, still did it. In fear of removing all the material I was trying to block I got aggravated and just grabbed my soft block and wet sanded the top with 400 and it seem to do fine.

I'm not sure If I was doing something wrong or is this why guys wet sand with 400?









I still need to roll the edges with 400, guide coat it white, then wet sand it with 600.

Thanks for the help.
 
Your paper is loading up. The material might be still curing, but you can expect a little of this anyway with finer grits even with cured material. There are several techniques guys use to clean the sandpaper of the little balls of junk that get stuck to it, a brush, a blower. your pant leg, lol.
 
Thanks Crash. I sprayed it about 2 weeks ago, Surface temps have been 70, but I know it takes longer than that for a full cure. I did use a blower to clean the paper, but it did it constantly. I figured it was the fine grit. Hopefully I got it straight enough with the 320 long board. Do most guys use a soft block with 400 or are they still using a long block.
 
It might have something to do with how often you cleaned the paper and the surface, and how often you changed the sand paper.
 
Thanks guys. Come to find out it was my block. I have an afs 21 block that works great with the coarse grits but for some reason with the 400 it loads up instantly. Switched over to a 20 inch durablock and it worked fine. Still had to clean the panel and change paper regularly but it worked. I think I have enough material on there to wet sand with 600, then I'll seal it and bc/cc.

 
Lay a good straight edge on the AFS block to make sure none of the foam is below the metal base and rubbing on your surface. The courser grits may not have allowed the foam to touch the surface, I had to trim several areas.
 
I have a whole set of Durablocks and quit using all of them but the round and teardrop. They have a tendency arch up in the middle after use.
For hand sanding I use this style:
16InchSandingBlock.jpg


I have a 16" and a 9" and then for the finer work a Hutchins inline sander.
 
I have one of those wood handled deals but it turns out it was warped even new. I blocked it down on a big piece of glass then glued a piece of plexi to it, then blocked the plexi. It gets things straighter than I want them, now.
 
I don't think there is anything wrong with the one he has, or the wood one either, after modifications are made. All the sanding on this door was done with the AFS
 
Crash, pretty good idea on putting a substrate layer under the wooden handle sanders to be able to block it straight. A handle sure would be nice sometimes, but I don't think I've ever seen one straight as is .

A harder surfaced block, such as an aluminum base, does seem to not let the sanded material move out of the way as well as a slightly softer block ​ I sometimes use a few drops of dawn dish detergent in my water as a sanding lubricant, but I guess that's kind of a matter of opinion on doing. If you are in a situation where you seem to be resanding the material you just removed, that is definitely counterproductive.

Probably my most used hand sanding blocks are various wood blocks I've made from hardwoods, softwoods, & even high quality domestic plywoods.

But at the end of the day, I think that all tools are just an extension of the hands of the user, & proper tuning of tools & use is more important than any specific type of tool. ​
 
Thanks guys. Chevman mine does have some foam that I need to remove after looking at your pics. I like the afs block because of the removable rods.

I do want to get one of those wooded blocks to try out to.
 
I like the AFS, but you will never go wrong when using advice from Crash. When someone has in depth knowledge about the ins and outs and why things work or fail, then pay attention when they speak, you just might learn something. Thank you crash, and many others on this forum, for the outstanding information provided to us--just for the asking.
 
chevman;n78155 said:
I like the AFS, but you will never go wrong when using advice from Crash. When someone has in depth knowledge about the ins and outs and why things work or fail, then pay attention when they speak, you just might learn something. Thank you crash, and many others on this forum, for the outstanding information provided to us--just for the asking.
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Absolutely. He and others have been a big help to me one this project and my 72 Camaro project. I'm very thankful for this forum. Hopefully one day as I learn the trade I can give back to the forum more.
 
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