Featured Post


Sunday, January 20, 2019

Bonnet Fill Primer and Putty Work | Roundtail Restoration

A good amount of work over the last two+ visit. To the video:

When I left you last, the bonnet was in epoxy following my filler work. The goal of these visit was to get it into build primer and, using that and some guide coat, figure out where else needed attention.

Before I get to that, though, I wanted to share that I acquired an original AM radio for someone on my favorite forum. I have no idea if it works, but it'll look cool, which is what I want. I do have to source some knobs for it, but another guy on the forum is good a 3D printing and he's offered to help me out, so I may go that road.

Now that's "old school".
Also, a while ago I picked up a 3M Orbital Sander, Model 20325. It has a 3/16" random orbit. I was doing some forward-looking research on the SPI forum for what to do with the paint following base coat / clear coat application. This was a recommended sander to use to buff it out. We're talking like 2000-grit and up sandpaper. When I looked at the price, however, I quickly realized I'd be sticking with Harbor Freight, as the sander was north of $200. But, like with my spray gun, I decided to look at Amazon Warehouse for it. They sell used or new, but returned, items in various conditions. Well, there was a "Used - Like New" one for $80. One-click ordered that one!

Hope I can figure out how to use it properly.

Moving on, before I hit the bonnet with build primer, there were a few obvious spots that needed some putty, like deep sanding scratches that I missed and, for the first time using my Rage Ultra filler, two small air bubbles.

Air bubbles just below the "U" letter holes.

There were also a couple of more spots that I filled and sanded down prior to the build primer.

From the RH side.

And from the LH side.

That done, some wax and grease remover to make sure it was all clean and about 4+ coats of build primer were applied. I mixed up more than I needed and I didn't want to waste it. Even so, I still had some left over. This was the first time mixing this much build primer, so I didn't expect a perfect mix. I took notes so I'll know for next time.

It's only about a 5 minute flash time in between coats, but it's a 30-60 minute wait to sand, so in the meantime I revisited some of the fiberglass filler I put on the body and started sanding that down. Contrary to my last post in which I said that I didn't want to use power tools to sand anything, I did in this case. One, it would take me forever to get this stuff sanded down by hand and two, regular filler will go over all of this stuff, at least, so I'm not worried about it being perfect as I'm using it to fill pinholes and irregularities left by weld repairs.

Front buildhead, showing some of the sanded fiberglass filler.

Then, it was on to blocking out the bonnet. Lots of work, but that's how it is with this stuff. I went in with 150-grit sandpaper. Not too aggressive, but enough to cut the stuff down pretty well.

Prior to starting blocking.

I also consistently used the guide coat here. I picked up a few cans of cheap-o Walmart flat-black spray paint. I wouldn't use this stuff to actually paint anything, but as a guide coat, it's great! I'd recommend the flat stuff because the gloss will tend to more easily clog your sandpaper up.

Guide coat applied. Time to get blocking.

Blocked. Dark spots are lows that need to be fixed or filled.

Pretty much rinse and repeat. I used guide coat the entire time and blocked out the entire bonnet. In those areas that I figured the putty wouldn't be sufficient (i.e., I would need to use too much), I tried to hammer the low out. Some I was successful doing, others not as much, but all in all, it went okay. And for some, I had limited or no access behind the dent, so I had to use putty in those cases.

RH side prior to blocking.

And after blocking. You can see the large low spot over the top center of the wheel arch.

The latch area on both sides of the bonnet were a mess, as I expected. I did some more hammer and dolly work on them and was happy with how they turned out.

Trying to show the waviness. This is after working it. Notice the gap below the left screw hole.

Once I worked out the dents as best I could, it was time to apply the glazing putty. To step back a bit, I had thought to use regular filler over top of the build primer for the low spots that I couldn't get fixed with hammer and dolly work. I wanted to minimize using it, though, so I asked on the SPI forum what everyone used, if anything, as a thumb rule to figure if they needed to use filler or if the build primer would fill the low. I'm glad I asked this question because one response was that I shouldn't use regular filler over a urethane primer, like the build primer. I didn't know that. And by the way, it was the owner of SPI that offered that tidbit, so I figure he's right! Thankfully, the glazing putty is fine to use. I assume because it's polyester-based vice whatever-based for the filler, but I didn't ask to be sure.

Because of this, I really tried to get the dents hammered out so as to minimize the use of the putty. It worked out okay, but there were spots that needed it, of course. I tried to spread the putty over a much larger area than needed so that it would feather in nice.

Glazing putty spots.

It was starting to get a bit late and we had some weather coming in. My part of CT was right in the "we have no idea what kind of precipitation your going to get" area so I didn't want to take any chances with having a snowy (or worse, icy) ride home, so I called it a day after getting about half of the glazing putty blocked out.

The bottom of the left-most spot still needs some work.


  1. Looking good!! I've been away from yout progress for about a year. I'll be following more closely in 2019!


    1. Thanks, John. Welcome back. You've got a lot of catching up to do!