Air dam and grill block design

[Smurf]

I tried doing some clear covers for my bucket-style S10 lights. It was rather thick stuff, but I took an old toaster (it fed me many-a pop tart) and held the plastic inside the toast slot. Took it out before the paper liner started to smolder, used towels to hold it and bent it over the edge of the counter top.

Slowly, slowly, very very slowly, it came to shape. Just a basic curve though, any extra curving angles would be tough.

[SCNTN]

I started work on the grille block. One nice thing about the design of the grille on the Sonoma is that it just pops right off the truck. And thanks to my wonderful wife, I was able to work on it inside where it's nice and warm.

Basically I built a form from bits of a pizza box, aluminum foil, and painter's tape. I first attempted this with plastic wrap, which was a lesson in failure. I left a partial opening at the top above the logo and sank two bolts into the form so that it can be secured (and removed later for the summer if necessary).

Now I'm just waiting for the foam to cure... directions say four hours but I'm guessing it will be closer to twelve because of the thickness. I'm planning to check it much like a cake - stick a toothpick in and see if it comes out clean.

[SCNTN]

So after about four hours I checked on progress... the top is firm, but the foil on the bottom was easy to push in. I flipped it over and poked about 200 holes in the back of the foil using a sharp toothpick. My thought was to give it a little air to cure. The foam in the bottom was still liquid. It is slowly expanding again, but not sure if my bolts will have enough "bite" now in the soft foam at the bottom. We'll see...

[CigaR007]

Expanding foam requires a warm temperature for proper expansion and hardening; usually in the 70F-80F range. Below that, the process will take longer and the foam will not expand as much.

[wmjinman]

Good job, SCNTN!!! So you're leaving it open for the GMC logo to show? What a great idea!

When I was forced to cut the 6" diameter hole in my cardboard grille block (which got rained on, ruined, & is now long-gone), it exposed PART of the GMC logo. I thought, "yuck - that doesn't look too good" (as though solid cardboard does, eh?).

But that's also part of what's making me think of doing it out of clear plastic. Right now I have a couple smaller pieces of clear plastic there - a "partial" grille block - and in most cases, it's almost "invisible" (at first glance, at least). So if the whole thing was clear plastic, I'm thinking it will be very "low profile" looking. Not as much as a true "stealth" block behind the grille, but far better aero .... the "aero stealth" design. HAH!!

[wmjinman]

Originally Posted by CigaR007

Expanding foam requires a warm temperature for proper expansion and hardening; usually in the 70F-80F range. Below that, the process will take longer and the foam will not expand as much.

I know some of the expanding foams require a certain amount of humidity to properly cure, too. I don't imagine that would be an issue in Tennessee, but here in Nevada is sure can be!!

[SCNTN]

Originally Posted by wmjinman

I know some of the expanding foams require a certain amount of humidity to properly cure, too. I don't imagine that would be an issue in Tennessee, but here in Nevada is sure can be!!

Yeah it's nice and muggy here today with rain rolling in, so humidity is not an issue. The grille is currently sitting on the kitchen table, so it's around room temperature. Hopefully it'll cure up tonight enough to start sawing and sanding tomorrow morning.

As for the GMC logo, I couldn't bring myself to cover it up. Plus, it is solid plastic behind it so it's an integrated partial grille block to begin with, right?

[SCNTN]

And here's the foam I used:


MAXFILL Expanding Sealant - Fills large holes and gaps - Spray Foam Insulation

Supposed to be eco-friendly versus the Dow stuff. I used the entire can for the grille block. I'll probably need two cans for the air dam...

[SCNTN]

Making progress...

After about 30 minutes of cutting and rasping, here's the latest. I filed a radius on the edges leading into the opening. Now I just need to fill and skim coat it with something and paint.

The mounting bolts are secured quite well. I don't plan on torquing them down to tightly, so they should be fine.

[nbleak21]

Looking great! Any ideas on the filler?