alexandervdr

The inside of the cabin is completely stripped and cleaned to the bare fibreglass. The surface is not very smooth though. The plan is to install a sound deadening layer (Dynamat or alike). What is the best coating to apply so I can ensure the Dynamat sticks perfectly?

biggd

Dynamat is pretty sticky. If you just clean the surface it will stick. I just painted mine with satin black paint only because I haven't finished off the interior yet.

Nowhere Man

Seems like a waist of paint to me. The only thing that will rust is the bird cage and luggage support. Paint those items with a good paint and carry on

alexandervdr

It's not about rust, it's about making sure the deadening material stays in place (less of a problem on the floor pan, but I am less sure about the roof). The idea of a paint is to create a more sticky surface.

Nowhere Man

Then sand or scuff it down

biggd

I only painted mine as it looks a little better since I'm driving it without the headliner finished. You don't need paint to make Dynamat stick. You will find out when you're working with that stuff that it's pretty sticky as is. As long as the surface is free of oils and dust it will stick. Just try and pull that stuff off after you've got it installed. It's pretty difficult.

alexandervdr

I just ended one year of sanding, scuffing and blocking the exterior of the body. Even just looking at sandpaper makes me feel sick

Gary's '66

Seems to me you would want it to stick to the glass instead of any painted surface if you're worried about adhesion. Paint can come off, the glass won't. I would probably blow all the loose stuff off then just wipe everything down alcohol and let it dry before application.

Gary

DansYellow66

I've used a similar mastic-based, foil surfaced material and I agree - once stuck I don't see it coming off, even overhead. But - to dampen vibration if fiberglass panels you don't need to cover 100% of the surface. I would put a few square feet of the mastic material back where the plastic heardliner halo is. If it were to somehow sag a little, the halo will hold it. Above the headliner, if I put anything, I would install some Be-Cool insulation banket which is very light, insulates real well, and can lay right on top of the headliner without any problems - or you can tack it to the underside of the roof with some contact cement.

biggd

I dynamated the whole inside of my car and it makes for a great sound barrier but does nothing to keep out the heat. For that you need insulation. I used two boxes of Dynamat and that adds quite a bit of extra weight to the car.

Gary's '66

I used Frost King air duct insulation from Home Depot. Insulates, deadened sounds, VERY lightweight and a fraction of the cost of Dynamat. Used 3 rolls with plenty left over. Cost: $60.00.

Gary

Vet65te

I agree with Gary's comment about not wanting to adhere the Dynamat to a paint coat. When the headliner in my 66 Coupe fell apart and sagged, before adding the new headliner I made sure to clean the fiberglas surface thoroughly with Enamel Reducer so the Dynamat would have a good clean surface to make contact with. Did the same to the inside roof surface of my 65 Coupe too. That Dynamat has been up there for about 4 years now and so far they're holding quite well.

Mike T - Prescott AZ

DansYellow66

Yeah - I see a lot of misunderstanding and mis-application of the heavy, asphalt base sound deadener material like Hushmat. It's real purpose is to dampen panel vibrations and resonance and because of that it's popular with the heavy bass, loud music volume guys. But to use it strictly as a vibration dampener to make a car sound more solid and for doors to close with a solid thunk - only a minimal panel coverage is necessary - like 15 to 20%. And contrary to a lot of press, it has very little insulation value and it is really heavy stuff - will weight down a car.

For insulation value it's hard to beat this stuff:
http://ezcool.ca/ezcool/

I mistakenly referred to it as Be Cool above.

The Frost King insulation commonly found at Lowe's seems to be kind of a hybrid stuff. It is heavier and undoubtedly has some dampening qualities, but it also insulates pretty well - that's it's primary purpose.

Gary's '66

Dan, that had to be a typo if you were referring to the Frost King material. That stuff is super light. I'll bet doing a whole car doesn't add more than 5 to 10 lbs.

Gary

alexandervdr

Thanks guys for the much appreciated feedback. Painting may indeed be a bad idea. The difference between heat insulation versus sound deadening is clear too. I'll do both as suggested. I raised the transmission tunnel to allow for extra insulation, and I will put heat barrier foil on the body floor (outside above where the exhaust pipes go)

DansYellow66

Gary - I meant to say it's heavier than the EzCool insulation material - but it is lighter than the mastic based Dynamat and Hushmat type material. I have some of the Frost King material. ERA who manufactures my Cobra Replica, uses it to insulate the fiberglass footboxes on the engine side. It adheres well under heat from the headers that are less than an inch away and insulates just fine. I bought some more to insulate the bottom of the footboxes because I run undercar exhaust instead of sidepipes. It's good stuff, readily available and cheap.

Here is Frost King material:




Some more Frost King on the underside of the footboxes:



This is the EzCool insulation on the floor. I have a mastic vibration mat under it - I think it was called B-Quiet. I bought it in a thinner section to hold down the weight. The stuff on the back bulkhead is the B-Quiet mastic material. A regular salad mix of vibration and insulation materials.

alexandervdr

I was particularly concerned about adding the insulation to the roof of my 64, and how well or how bad it would stick to the rough fibreglass surface. I finally coated the interior with por15 after I read following on the POR site: " ....POR-15 is fully compatible with fiberglass and can be used to repair cracks in gelcoat. It will adhere better than polyester resin and has greater strength. ....." It sealed the inside of the car beautifully and I am pretty convinced the insulation will stick better too

alexandervdr

I finally installed the Dynamat Extreme in the interior. The one thing I can confirm is that the POR15 is a fabulous base to stick the DynaMat to. In my case, substantially better than on bare panel. Trying to pull it off again does not cause the POR15 to come off, it rather tears and stretches the DynaMat.

During the process of installing, I noticed how much of an 'acoustic drum' the rear bottom pannel is. Slap on it with your hand and in returns an impressive drone sound . I would highly recommend to ALWAYS put at least sound deadening there. The difference is huge. The sound frequency is in the same zone of exhaust drone, so the undamped panel may actually amplify it!

As far as DynaMat is concerned: yes it is expensive, and yes it is time consuming to install. But it sticks better than the 2 cheaper alternatives I tried, and it adapts reasonably well to curved surfaces.

Frankie the Fink

I used some Home Depot "Peel and Stick". Already has adhesive on the back and sticks like iron to bare fiberglass. Once its installed you'll tear off fingernails trying to lift it back up.

The only thing 'extreme' about Dynamat Extreme is the price.

alexandervdr

The debate about the value of DynaMat will never end, till there are hard data on the sound/vibration deadening coefficients of Dynamat and all the others (and there are none...). Not saying DynaMat is the best (I don't have a clue), however the way the stuff is made respects the rules of how good vibration deadening panels should be made. So I am quite confident that it does what it should do. The money is an issue, but after all I spent on my restoration I stopped counting (it made me sick anyway) Many replacement parts are way overpriced to the quality they represent, the overspend on DynaMat is only a drop in the total...