What should I use to fill cracks & LIGHT-PROOF my cab?

I'm planning to use regular ol' tub caulk, but just want to double check for better ideas. I'm hooking up the shell of an old portable air conditioner -- so I have a few lil nooks & crannies to seal.

This is of course before I go in with the mylar. Should I try something other than caulk?

Good forum post, I'm interested as well. I used duct tape and more mylar. You can use cardboard as well but maybe we'll see some better answers.

Duct Tape...

I found white duck tape. Where i went wrong was not putting a layer of black or normal tape down first. Otherwise you will have to put like 4 layers down.

I was thinking more along the lines of something to fill really small cracks, screw holes & such, from where I removed the guts of the air conditioner. I'll probably just use caulk or silicone gel. I'm gonna line the whole innards with mylar too.

But this board is always good for new ideas, so I thought I'd check here.

Buy some project board from the store. Glue it and put glue or caulk around holes.

Or just plain hot glue. Its odor free and dries in five mi.utes

first use electrical tape, a couple layers side by side over lapping, then use duct tape, i found some white duct tape to be good they also have a chrome kinda looking one if you have mylar

have you seen the info-mercials for the spray on black sealant? Looks like a good alternative.

that rubber in a spray can? flexseal

Mr Skunky Haze said:

that rubber in a spray can? flexseal

Click to expand...

Yeah that's the stuff. Investigate the product first though before possibly light proofing your cab with possibly toxic materials.

yeah i personally wouldn't use that, who knows whats in it. but it could be safe and if so a very reliable fix for light leaks

Thought id post what I've done recently. Go to walmart, home depot or a similar store. Go to tools and hardware section. Look for tubes of wood filler. I've used it to fill in the cracks and it hardens like wood. If your covering a bigger hole use that graph looking tape and use caulk or wood willer overtop of it like how you fix drywall.Goodluck. Stay frosty.

I volunteered for a politician who lost big time and was not going to run again so I collected a few dozen of his big 4x8 lawn signs and have been using them for all types of projects including lining the interior of stealth cabs. They are white on one side and made of durable corrugated plastic. I use a heat gun to soften along bending lines and it cuts easily. If you measure it and bend it correctly, you can minimize edges that need to be joined or filled.

I glue or staple it onto plywood or sheet rock walls too. It makes for a nice reflective and waterproof surface. The politician was dickhead who was against mmj, so I love using his signs!

You can always use GREAT STUFF to fill cracks, that stuff is awesome. It is spray foam that expands and dries hard.

Aluminium tape and mylar should do the trick.

Can you post a pic of the A/C unit being modded?

Is it an old vertical window banger, or a newer portable unit?

ATL HYDRO said:

You can always use GREAT STUFF to fill cracks, that stuff is awesome. It is spray foam that expands and dries hard.

Click to expand...

This would be a decent idea if you have weird shaped pockets that would be hard to tape over.

And you could trim it to shape when it dries.