[watercamper]

I know that many of you used Great Stuff as an adhesive for the polyiso foam board. I'm thinking of using the RMax from HD which has the foil on both sides. Has anyone tried and/or had good luck with the 3M 90 for this application?

What is your opinion of the sound deadening qualities of the polyiso? Has anyone been able to test the difference between the Thinsulate SM 600L and the polyiso? My Google searches say that it has no acoustical properties.

 

[RDinNHandAZ]

I am not sure but the RMax may be the same thing as the Polyisocyanurate as it goes by different names like that and Tuff-R. It is foil on both sides and whitish or yellowish inside. I guess after so many have done it with the great stuff and a pro-gun applicator I can’t see why experimenting with a different bonding system makes sense? I just glued some carpet to the styrofoam blocks with Home depot’s spray which I was told is just as good.... now I have to get the other glue and redo it! Gr-rr-rr. the 1” Polyisocyanurate seems good for sound. I did a decibel test before and after on the same road and it reduced the sound level by 10 decibels, which is a LOT. I plan to retro-fit sound deadening to the wheel wells next summer. If you decide to be an experimenter let us know how it goes.

 

[GaryBIS]

HI,
According to the product description RMAX is polyiso. You can check for sure by looking at the sheet -- it will say Polyisocyanurate somewhere on the sheet.

I've used Great Stuff (pro and regular) to glue polyiso sheets of insulation to a lot of things, and it works very well. I agree with RD that it does not seem worth taking a chance on another adhesive. If the adhesive does not work well, you could end up with a lot of squeaking between the insulation and the van skin.

I tried earlier to find a noise reduction comparison and found a little bit on the thinsulate, but nothing on polyiso. This is not very scientific, but just playing around with a sample of Thinsulate its hard to imagine that it does a lot of noise reduction -- its very open. It would be nice to get a good engineering comparison.

You will need to make some spring sticks to hold the insulation sheets against the van skin while the Great Stuff cures.

Gary

 

[watercamper]

Yes, the RMax is polyisocyanurate. No problem there.

I was just wondering about an easier method to attach it. The Great Stuff method requires the insulation to be held in place until it cures. And I have to buy a $54 gun.

The 3M90 works more like contact cement. Fast and easy as long as it is compatible with the foam and will stop squeaks. As much as everyone seems to use the 3M product, I figured someone had tried it on the polyiso to see if it melts or pulls the foil off.

I agree with you, there isn't much NVH info on the polyiso. And, only a little info in the form of a couple of graphs on the Thinsulate none of which gives me any real world understandable info. As you once said somewhere, you would think that with all of the DIY conversions, there would be some real world info, testing, data, etc on insulation. I liked one guys take on insulation (thermal or acoustic) - for every 40 people there are 50 ways to do it.

 

[johnnybesurfing]

.02 cents

Thought I should weigh in and give my .02 cents worth. I just finished my head liner and now the van is totally insulated all with Hiens thinsulate! Application was so easy. I measured and cut with good scissors the material, then applied a thin spray of 3M 77 to the white side of the thinsulate. I then took the sprayed cut section and pressed it to the van walls and ceiling, black side facing away from the van walls. By the way this works great to hold the material in place. I then screwed the paneling over the thinsulate and done!! I also stuffed the material between the stock headliner in the driver and passenger area.
As for sound deading I used Fat Mat for the wheel wells and door panels. The van is as quiet as a cadillac! Well maybe not as quiet but very close! Cheers

 

[watercamper]

That's good info. So, only Thinsulate and no polyiso? What did you use on the floor? I'm not after the sound of a luxury car but quiet sure sounds good (pun intended).

 

[Roblee]

I installed 1.5" and 2" polyiso with 3M 90. Sprayed both sides, let set for a minute and pressed on. Filled gaps and edges with Great Stuff. No bracing needed, no problems. Because walls curve don't try to use big pieces because they don't bend well and there will be spaces that don't adhere to van wall.

Noise level when parked is outstanding but all the wall insulation in the world won't reduce road noise from tires. All four wheel wells are inside so they all add significant driving noise. I'm not happy with my driving noise level.

Thinsulate is marketed as acoustic. It mates well with the walls and should dampen vibrating panels very well, but I can't see how it could be better than polyiso if applied correctly. However, I'm not convinced it really matters; these are big noisy vehicles.

 

[Zoomyn]

3M90 on both metal & poly-iso surfaces - while that dries to slight finger-drag tacky be putting a ring of window/door great-stuff foam around the edge of the flat face, not the thin edges, of the foam board - then press the board in place and massage it against the contact cement until the cricks and pops stop and the contact cement has welded the board in place, no prop sticks required - then the foam will harden and provide a o-ring style seal to prevent humid air from drafting between metal & foam plus be a forever-adhesive if ever the 3M90 should part. Follow up with a 'grouting' bead to fill the gaps around the periphery... Fun & satisfying too.

I did that on every panel insulated in my 159" window wagon - the 1"-thickness 15"x15" section I had to remove to install the Maxxair MaxxFan fought like mad to stay attached and only came away in 4" or 5" chunks.

I just looked on Amazon, $15 buys a precision applicator gun that works with great foams according to the Q&A ... https://www.amazon.com/dp/B01C9Q9X8M/ (edit: beware some negative reviews)

 

[Roblee]

Zoomyn,
Best method description I've seen.

 

[TedV865]

I have used 3M 77 and 90 on motorcycle seats, car interior, door panel and headliner kinds of things. The 77 failed fast. The 90 held a little longer but it failed to hold. I tried specific headliner adhesive since it is supposed to handle the heat better. It lasted longer than 90 but failed also.

The only contact adhesive that has not failed from the heat down here in the south has been Weldwood original. The environmentally unfriendly, careful to have good ventilation or you will kill brain cells kind. I use cheap chip brushes to paint it on per the instructions. Once it grabs, you will destroy whatever you try to take apart. Great stuff and Gorilla glue seem to stick things together as well as long as you have moisture to let it kick. The foam of the great stuff is a little easier to rip apart than the Gorilla if you have a large gap. The great thing about great stuff is it will fill larger gaps. Almost like it was designed to do that.