Sanding grits progression questions

[Svtfreak]

Ok y’all help me out here. I’ve got my seams done. Now it’s time to rough it up for filler primer. There’s plenty of 40 and 60 grit scratches. I’m reading conflicting info on what to scratch it up with for the primer filler. I’ve read 60, 120 and 240. I typically use roberlo multyfiller. What say y’all?

Then, what grit to (dry) block it with to slick it out (which will be followed with sealer).

What grit to wet sand the sealer before base coat? (This I think I have the answer for on the Ppg instructions but I’ll still ask)

Thanks y’all.

[FF33rod]

Have a boo at some of the posts/advice Jeff Miller and Jeff Kleiner on this topic.... I recall a lot of discussion on GoDadGo's build thread for a roadster with step by step info...

Steve

[Svtfreak]

Have a boo at some of the posts/advice Jeff Miller and Jeff Kleiner on this topic.... I recall a lot of discussion on GoDadGo's build thread for a roadster with step by step info...

Steve

Thanks Steve. I’ll check that out tonight.

[Jeff Kleiner]

I've never heard of Roberlo Multyfiller so I gave it a google. Looks to me like it is an acrylic direct to metal primer; not something I'm familiar with using on fiberglass so I can't speak to it's use or even compatibility. For what it's worth my recipe (which is much the same as what Jeff Miller and Ken Pike do) is to prep the body with 80 grit then apply 3 full coats of a polyester high build such as Evercoat Slick Sand (my preference) or similar. This will build enough to bury the 80n scratches and bite hard. Block this to 150 then 3 full coats of 2K catalyzed urethane primer surfacer (I use PPG MP282/Shopline JP202). The urethane is blocked with 320 dry then 600 wet prior to 2K sealer (PPG MP23*/Shopline JP33*). The sealer is just nib sanded as necessary to remove debris before immediately moving to the basecoat.

Good luck,
Jeff

[Svtfreak]

I've never heard of Roberlo Multyfiller so I gave it a google. Looks to me like it is an acrylic direct to metal primer; not something I'm familiar with using on fiberglass so I can't speak to it's use or even compatibility. For what it's worth my recipe (which is much the same as what Jeff Miller and Ken Pike do) is to prep the body with 80 grit then apply 3 full coats of a polyester high build such as Evercoat Slick Sand (my preference) or similar. This will build enough to bury the 80n scratches and bite hard. Block this to 150 then 3 full coats of 2K catalyzed urethane primer surfacer (I use PPG MP282/Shopline JP202). The urethane is blocked with 320 dry then 600 wet prior to 2K sealer (PPG MP23*/Shopline JP33*). The sealer is just nib sanded as necessary to remove debris before immediately moving to the basecoat.

Good luck,
Jeff

Thanks Mr Jeff! I’m not against changing what I do. I did the roberlo on my mk4, and immediately followed with Ppg dplf reduced as a sealer . And it came out great and stuck well but it’s a bit brittle. I think that’s the clear though.

Is there a reason not to go straight to sealer over the slick sand? I was taught as long as the filler was covering everything (no break through when blocking) that sealer next was fine. Keep in mind, I was not taught by a professional lol.

[Svtfreak]

Ok Mr Jeff. I think I’m going to follow your recipe or similar. Including the catalyzed primer before sealer. Did a little reading and now I understand why.

One question. What is the difference between a urethane primer like you use or an epoxy primer like the dplf?

What grit do you nib the sealer with? I actually plan on wet sanding the sealer (I did on my firewall to get it just perfect before I did the base coat).

Could I give you a call Monday sometime?