2-Part Polyurethane Foam by the Gallon

[Buzz Nichols]

The thought crossed my mind, but...how much do you reckon that hunk of metal weighs? I think it'd take a lot of planning, a winch, a high platform and probably a couple of buddies.

All of which I suppose I could come up with.

[o1marc]

Originally Posted by Buzz Nichols

The thought crossed my mind, but...how much do you reckon that hunk of metal weighs? I think it'd take a lot of planning, a winch, a high platform and probably a couple of buddies.

All of which I suppose I could come up with.

You are a glutton for punishment, aren't you.

[Buzz Nichols]

You keep supplying the bad ideas, I'll keep runnin' with 'em.

[Native]

Originally Posted by ol trunt

Lots of ways to skin a cat. Here is another "out of the box" idea. Perhaps we could start a skoolie Go Fund Me and raise enough money to buy a big auto rotisserie like this<link removed> and a spray foam system that we all could share--------------------
Jack

My dad has a rotisserie like that, He is currently restoring our 1967 Datsun SPL 311 sports car. When he got it, I said jokingly that I need one for our bus. He said they make them to handle railroad cars!


I believe the one he has cost around $2,000.00.

[rossfree]

I love the idea of saving money like the rest, but I think the general consensus is that the time required of mixing many small batches of foam, along with the temporary forms, and the precise mixing requirements, under possibly varying temperatures, varying flow characteristics and difficulty of placement in vertical or ceiling conditions, not to mention tool cleanup and likely some spills... my personal conclusion is that the risk / reward of saving money here just doesn't stack up. I'm retired, with unlimited time at my disposal, and still... the idea of foaming the entire bus in a day or two would seem like the better way to go. Sometimes spending a little more just makes since.

Best wishes!

Ross

[Brewerbob]

Originally Posted by o1marc

They have already tried everything you have mentioned and they have perfected the system. It's called Spray foam. It mixes at the end of 2 hoses and sprays where you point it. At this point I'd like to see it go forward on the tests, I'm curious to the outcome.

Not limited to what's in the books, but common sense goes a long way. You're not going to reinvent the wheel.

What is "best" and most economical on a commercial scale isn't always the best on small scale. I know you're mostly busting his balls but leave him be. Maybe we'll get a new idea out of it.

Originally Posted by dan-fox

When it comes time for me I'm going to look long and hard at kerfing flat pieces of foam, gluing them up, and then filling the cracks and crevices with either one small DIY kit or a handful of spray cans of Loctite foam which is advertised as closed cell.

I think I've mentioned this approach before (and have since forgotten it again myself). This would certainly work for the floors and walls. Everything flat stays flat with rigid foam and then "skim" coat it with spray foam. It ain't going anywhere after gluing and then a complete airtight skin of 1/2"-1" thick coat as a final layer.

So, here's another stupid question, using the regular 2 part DYI kit, how THIN of a layer can you spray? Hat channel is ~2.45". Use 2" board and spray 3/4" thick? Or 2 1/2" board and 1/4" thick?

Originally Posted by gclarkv

As a money-saving measure, one could insert rigid foam board into the wall space and pour liquid foam on both sides of it.

The pour in place foam will fill voids, cracks and crevices better than even spray foam. It can be installed with very little waste and almost no mess. Most important to me: It forms a powerful bond between inner and outer wall and ceiling skins, resulting in the strongest, most rigid and quietest structure.

It's (not even) a foot tall but 80 feet long, that would certainly work behind the chair rail.

[Brewerbob]

Anyone think sound deadening is worth the effort/hassle/cost? $14.28 a sheet (1/2"x4'x8'). 10 would do the length of the floor. 30 if you're doing the floor and walls. $500 total.

https://www.homedepot.com/p/Sound-Ch...7008/202090237

P.S. Randomly grabbed this product. This is NOT meant as an endorsement for the product itself, Home Depot, or the price but $500 (or possibly far less) for sound deadening might be worthwhile tho. Thoughts, opinions, nasty comments?

[peakbus]

Originally Posted by Brewerbob

Anyone think sound deadening is worth the effort/hassle/cost? $14.28 a sheet (1/2"x4'x8'). 10 would do the length of the floor. 30 if you're doing the floor and walls. $500 total.

https://www.homedepot.com/p/Sound-Ch...7008/202090237

P.S. Randomly grabbed this product. This is NOT meant as an endorsement for the product itself, Home Depot, or the price but $500 (or possibly far less) for sound deadening might be worthwhile tho. Thoughts, opinions, nasty comments?

I bought a sheet of that when building a cover over my dog house. I ended up returning it as I was skeptical that it would do enough to quiet the beast. Used elsewhere, it could help BUT I feel like it would absorb water like a sponge. Of course you probably won't be hosing out the remnants of 84 little passengers on a regular basis.

[ol trunt]

BB, what kind of noise are you trying to attenuate and under what conditions? As a "rule of thumb", high frequency noise is well controlled by foam rubber while low frequency noise (like the throbbing of a generator or a bad a$$ boom box) requires a dense barrier like lead or heavy rubber or bitumen.

As to the material you are considering, in a residential setting it helps with neighborhood noise but does nothing to dampen the low rider stereos the local adam henerys so love to subject us all to.
jack

[Brewerbob]

Originally Posted by ol trunt

BB, what kind of noise are you trying to attenuate and under what conditions? As a "rule of thumb", high frequency noise is well controlled by foam rubber while low frequency noise (like the throbbing of a generator or a bad a$$ boom box) requires a dense barrier like lead or heavy rubber or bitumen.

As to the material you are considering, in a residential setting it helps with neighborhood noise but does nothing to dampen the low rider stereos the local adam henerys so love to subject us all to.
jack

I'm thinking some of both I guess. Driving down the road, you've got a diesel engine turning at 2200 RPM so a LOT of that would be low Hz. Then it's also a school bus and regardless of skill (or in my case the lack of) it's going to squeak, rattle, and roll going down the road.

My bus is RE so it's not terrible. I've driven distance once as literally an empty metal can. And "not terrible" is subjective. I turned 50 this year. The trip was the first year I had the bus ('17). Any kind of white noise and I can't hear much of nothing else.

Anywho, I guess what I was really thinking was for road noise while driving. Don't really need to keep the bird whistles out.

Originally Posted by peakbus

I bought a sheet of that when building a cover over my dog house. I ended up returning it as I was skeptical that it would do enough to quiet the beast. Used elsewhere, it could help BUT I feel like it would absorb water like a sponge. Of course you probably won't be hosing out the remnants of 84 little passengers on a regular basis.

Yeah I was wondering the same. Maybe as the inside layer so as to not soak up any condensation against the skin of the bus? I'm still thinking spray foam as against the skin to seal any holes and prevent condensation from forming.

The gf is looking forward to grand snot lickers. I am not. That reminds me, I should stock up on burlap bags and cinder blocks. No one is preggers yet but it's not too early to plan.

[Brewerbob]

I'm also waffling on which way to insulate. Spray first (seals) and rigid over that? Or rigid nice and flat then cover with spray? I'm worried that wherever the metal is bowed (and there's a lot), it'll be a puddle from condensation. The floor is riddled with nail holes from the OEM plywood. Road spray alone will find its way in there.

Hence the question on the thinnest layer possible of spray foam. Spray, rigid, spray. is what I'm thinking. Rigid to take up the bulk of the volume thus reducing cost. Doesn't really matter too much if there are pockets of air between the first coat of spray and the rigid. As long as the rigid lays flat and even enough not to have a corner sticking up above whatever the overall height is.

[family wagon]

Maybe lightly spray a small area (1-3 square feet) and press a piece of foam board into it? The light spray could adhere the board into place, and after it was all done, another topping coat of spray could fill in the gaps and seal the whole thing.

That does sound like a process for a person who has more available time than money. It would be a lot of trouble, and would probably require very good coordination between two or more people to get the spray applied and foam boards placed before it set too much.

[o1marc]

Originally Posted by family wagon

Maybe lightly spray a small area (1-3 square feet) and press a piece of foam board into it? The light spray could adhere the board into place, and after it was all done, another topping coat of spray could fill in the gaps and seal the whole thing.

That does sound like a process for a person who has more available time than money. It would be a lot of trouble, and would probably require very good coordination between two or more people to get the spray applied and foam boards placed before it set too much.

The problem with that is if it's still soft enough to press on and hold rigid board, it is still expanding and your finished surface may not be where you want it.

[family wagon]

Originally Posted by o1marc

The problem with that is if it's still soft enough to press on and hold rigid board, it is still expanding and your finished surface may not be where you want it.

Yes, the method definitely has problems. The foam board would have to be thin enough that expansion of the sprayed layer wouldn't lift the foam board beyond the desired finished thickness of insulation. The topping coat of spray would finish the fill over the foam board.

So, supposing a person could actually make the technique work, how much would it save? Maybe 50-70 percent of the volume of spray foam would be replaced with rigid foam. That cuts the spray materials cost but increases the rigid materials cost. What would be the net savings? It would have to be at least $1000 net savings for me to go for it.. but I'll guess the figure is lower than that. To me it wouldn't be worthwhile.

[Brewerbob]

Originally Posted by family wagon

So, supposing a person could actually make the technique work, how much would it save? Maybe 50-70 percent of the volume of spray foam would be replaced with rigid foam. That cuts the spray materials cost but increases the rigid materials cost. What would be the net savings? It would have to be at least $1000 net savings for me to go for it.. but I'll guess the figure is lower than that. To me it wouldn't be worthwhile.

Let's make some assumptions, round some numbers, and do really bad math!!

Spray foam is $600 for 620 bd ft. Let's call that $1 a foot.

Well there goes that theory... Home Depot has R-Tech 1x4x8 R3.84 at $12.58 a sheet. They also have Owens 1x4x8 R5 at $23 a sheet. Apples to apples, we should use R5 since it's closer to the spray foam's R value.

To "make" a sheet it would cost you $32 in spray foam. You need 2 full kits of spray at only one inch deep to do a 40' bus. That's 300ft per top, bottom, and sides (ignoring end-caps entirely) $1200. Double for 2" deep. $2400.40 sheets at $23 each...$920 + 1 kit = $1420 vs $2400 gives you the same depth as a 2" spray.

The 2" rigid is $21.65 for R7.7 and $35 for R13.1, 40 sheets @ $21.65 = $866 + 1kit = $1466, 40 @ $35 = $1400 +1 kit = $2000 for the same as a 3" spray. Just foam at 3" is $3600.

Personally, I think I'm for the combo tho as you point out, spray and done would be nice. Before playing math major I was kinda with you on this. Not so sure now. Feel free to poke holes in anything I did here. I honestly didn't know what the numbers would say before doing this.

So yeah, looks like your numbers are spot on. 50% exactly at a 2" overall depth and 66% at a 3" depth. And that savings is $1000 and $1600 respectively.

[o1marc]

That combo sounds labor intensive. Have you figured a price for your labor, deducted from the savings?

[family wagon]

Hmm. Home Depot lists different pricing for the foam board depending on region -- it's more expensive here in Utah! Note that the R-Tech product is EPS "bead board" while the Owens Foamular is XPS and is more comparable to closed-cell spray. The 2" rigid you mentioned must be EPS, and I suspect the 3" is also.

I was following along OK as far as needing 2400 bd ft to do the job, spray foam costing about $1/bd ft, and Owens Foamular XPS board costing about 23/32=$0.719/bd ft. Kinda lost track when you switched to the 2" EPS board.

If we suppose we're pretty talented and can embed 1.5" XPS rigid foam in that 2" thick wall with spray in front, behind, and around the four edges of each piece of rigid foam, then maybe 65% of the job could be filled with rigid foam instead of spray. So we'd have 0.65*2400 bd ft = 1560 bd ft of rigid foam at a cost of $0.719*1560=$1121. Add to that the 0.35*2400 bd ft = 840 bd ft of spray foam at a cost of $840, which comes to a total of $1961 to mix-and-match 1.5" XPS with spray, compared to $2400 for spray-and-done.

The above assumes:

• zero waste as the rigid boards are cut to size
• we can buy exactly 840 bd ft of spray
• we can work quickly enough to avoid the spray nozzle clogging every time we pause spraying to place a piece of rigid board

Those are semi-bad assumptions, which tilts the analysis further in favor of using spray alone, right?

[Buzz Nichols]

Originally Posted by o1marc

That combo sounds labor intensive. Have you figured a price for your labor, deducted from the savings?

I think this approach to any built-not-bought stuff is pretty much a deal killer out of the gate.

Sure, there's a point when the labor intensivity of a given approach stops making sense, but if you were paying yourself by the hour to build a skoolie (or a cafe racer, or a boat, or whatever you want to build instead of buying it), you'd end up with a pile of money big enough to buy 2 built by somebody else.

...And that somebody else would gladly take your money so they could start wasting their valuable time on the next project.

What I'm trying to say is, if it made sense to monetize your time for building these machines, most of us probably wouldn't have day jobs.

[o1marc]

Originally Posted by Buzz Nichols

I think this approach to any built-not-bought stuff is pretty much a deal killer out of the gate.

Sure, there's a point when the labor intensivity of a given approach stops making sense, but if you were paying yourself by the hour to build a skoolie (or a cafe racer, or a boat, or whatever you want to build instead of buying it), you'd end up with a pile of money big enough to buy 2 built by somebody else.

...And that somebody else would gladly take your money so they could start wasting their valuable time on the next project.

What I'm trying to say is, if it made sense to monetize your time for building these machines, most of us probably wouldn't have day jobs.

I agree, now if you were to ask me to add this labor intensive process on top of it I think the ROI is negligible.

[peakbus]

Money aside, and having only read about others experiences (in other words take this with a serious grain of salt), I feel like it would be challenging to end up with an even layer of spray foam onto which to stick a piece of rigid. I just think about the times I've cracked of a can of Great Stuff foam and suddenly it's everywhere but where I want it. Now multiply that, add finessing in rigid foam while setting down the gun as it continues to ooze. Sounds like a S**! show. Please set up a camera before you start
No offense, that's just how I envision it going in my world.