So, there’s a wealth of information already in this forum about the plywood/foam/Homasote debate. I know this, I’ve read a lot of threads… but one thing that never gets mentioned is my question above. There’s plenty of discussions about Homasote on ply, or using any of the three by themselves. But I’ve never seen a comparison of whether plywood or Homasote is better to put the foam on.
What I’m trying to avoid is the “drumming” effect that is known to occur with foam, which I’m going to use due to the hilly terrain cut with creeks and gullies I’ll be modeling. I want to hear wheels on rails, not all manner of strange reverberations coming from “underground” (no Graboids here…). I’ve read several threads that say you should glue the foam to a substrate to help avoid the drumming, but I only ever see plywood mentioned. I’m wondering if it might be worth putting it over Homasote instead.
My trackwork will be Code 83 flex glued to cork roadbed, which itself will be glued to the foam. No nails. I will use a 1" and 2" layer of foam, glued together, for the topography I plan to model, and this will be set up on L-girder benchwork.
Based on a number of interesting and highly technical posts (looking at you, Hornblower), I know that a key part of the equation is using a flexible adhesive like caulk between layers. But I’m not sure if I should lay my foam onto Homasote or plywood. Both are available here and within my price range, so those aren’t considerations. However, testing both would be cost-prohibitive. So what would be the recommendation? Or is it more to-may-to/to-mah-to considering how I’d be using it (under foam)?
Frankly, I thought my last layout, which had a layer of plywood under the foam, was LOUDER than the one before, which simply had foam glued on top of an open grid frame.
Some say that the ballast glue makes a difference.
Somebody could study this, Model Railroader set Cody on this project.
Homosote is great to stick track nails or spikes into. It is miseably dusty to cut and heavy. It is what I used in the 80’s for my first big layout and back then, I had no sound issues, that I recognized.
Thirty years later, my hearing is not what it used to be. 2" of foam on 1/8" plywood and I don’t hear the druming. YMMV
IMO, the drumming happens when trains vibrate the subroadbed. I think there is less drumming when the material is denser and better supported. Its harder to vibrate, theoretically.
My new layout with have half inch ply sub supporting sheet homasote attached by caulk spread evenly by a roller, then cascade products homabed on top of the homasote sheet attached by rolled caulk. Then track caulked onto the homabed.
I’m hoping with two layers of homasote and everything separated by a layer of caulk, vibration will be dampened before it can drum the plywood against the benchwork support.
This all makes sense based on what I’ve seen elsewhere, and Homasote is supposed to be denser than ply. Perhaps that would be best then, with the layers of subroadbed, roadbed and track joined by layers of adhesive caulk…
[(-D] True that. But this is why designs in the real world are tempered by practical concerns. Actually, didn’t you make a similar point in another thread? [;)]
Joking aside, I also recall something in one of those threads (perhaps a comment by Hornblower) saying that while the material density itself was important, it was more the difference in density that regulated sound transmission between materials.
If that’s the case, I’d be fine with the ply base, and could use the savings to get better quality wood. If it’s not, and the extra density would factor in for improved acoustic nullification, then my earlier surmise that Homasote would be better still holds.
Frak…
Maybe I’ll just go to the Big Orange Box near me, grab a sheet of each, and hope my old boss doesn’t yell at me for messing with the merchandise…
My instincts tell me foam over homasote should be quieter than foam over plywood, just based on rapping my knuckles on homasote versus on plywood - homasote is softer and transmits fewer vibrations, which are of course the essence of sound.
I also suspect, however, that the differences are not likely to be huge.
One thing to keep in mind is if you ever envision trying to remove the foam. With a spatula and some elbow grease you can do a pretty good job of prying foam up from plywood, even if it was well fastened with adhesive caulk, but homasote tears away in ways that plywood does not: the top layer of homasote pulls up and away from the rest of it. What’s left is often too irregular a surface to be usable again, in contrast to the plywood which can be scraped and re-used.
Someone who saw my benchwork (a box like grid of 1x4s with plywood on the top) speculated that it was built like a guitar and might even amplify the sound. In other words their concern was not what the top was, but what was below the plywood or the homasote or whatever.
I have not tried this (which – heh heh – doesn’t prevent me from urging you to give it a try) but I wonder if the strategic use of rubber washers in the construction of the benchwork would dampen the sound amplifying effects. I can’t speak about guitars but know that string instruments such as violins or cellos are considerably quieted if a rubber “mute” is placed on the bridge that transmits vibrations from the strings to the wooden “box” body of the instrument.
On my layout, I have track on cork on foam, track on spline mounted to plywood, track on spline mounted to open grid, track on cement, track directly on foam and track on a steel stud. The sound changes noticeably as it goes from one to the other.
I have found that what is on the floor under the layout is the biggest determining factor as to the noise level. I had the same 9’ x 5’ layout over porcelain tile, cement floor, and carpet. The noise level and sound frequency level changed dramatically over each.
Cement taught me one thing that I was not expecting, the most noise comes from steel wheels on steel track. Railroading is a loud and noisy business, on cement board all you hear are the wheels on the track, the cement board removes any other noise. You can also cut and drill through the cement board.
I think using foam over plywood is somewhat of a redundant exercise, use one or the other, it certainly makes working through it easier.
My layout has large areas of homasote over 5/8" plywood and large areas of 3/4" foam over 5/8" plywood. The foam may be slightly louder but not significantly so. Noise wise, I was astonished how much louder trains are after the flex track is glued down to foam. When the track is just laying on the foam they are nearly silent, but MUCH louder after the track is glued.
But that doesn’t answer the OP’s question: I don’t think homasote is nearly rigid enough to be used as a viable base under foam.
Advantages of Homasote as subroadbed: Very slghtly quieter than foam. Great for spiking track. Doesn’t dent if you rest elbow/etc on it. Much tougher surface than foam. Foam is VERY easy to accidentally puncture/dent/etc.
Advantages of foam as subroadbed: Lighter and easier to cut than Homasote, Available in thicker sheets than Homasote. Easier to create negative terrain profiles (ditches, cuts, etc), Normally perfectly flat surface (However I got a couple 1" thick foam sheets that had noticeable bends/swales that were challenging to flatten).
Yeah, I do need the foam to do some negative terrain, so that part’s non-negotiable.
But the rigidity factor is something I hadn’t thought about. I’m not too worried because I do have a dehumidifier for the train room, but still, it’s something to consider. But I wonder how big a factor it would be if I have three inches of foam above it (that’s what my topography calls for to do the creeks and gullies), and it’s all glued together with latex or PL-400 adhesive. Also, if it was possible for the stuff to buckle and heave in any less than a few decades (barring a flood or an unduly humid environment), I doubt it would be as popular as it is. Who would want to have to redo their trackwork (or entire layout) every few years?
Still, plywood just gained a point or two after these past few comments.
I use a homosote over plywood subroadbed and I like the way it takes nails.
I am not as convinced of it’s sound deadening properties though. We laid a layer of Homosote along with other sound deadening material while remodeling the apartment that I eventually moved the layout into and the deadening effect on the downstairs apartment was somewhat marginal at best.
Use whatever you like, of course. Note that folks used risers with plywood cookie-cutter roadbed to create terrain below the track for decades before extruded foam existed. Including that John Allen fellow.
Wow. That’s mighty impressive. So much for worrying about moisture damage.[:)]
At any rate, the concern is less about structural integrity/reinforcement and more about neutralizing non-wheel sounds. Any divots I put in the foam will just turn into landscaping opportunities. The area I’m basing on is anything but flat.
I know I should have SOMETHING under the foam to eliminate stray noise, but I’ve alternately heard that plywood helps or that plywood exacerbates the problem, which is what drew my curiosity to homasote, which everyone seems to swear by for noise deadening and reducing the ambient sound.
Ok, for those of you that have not studied sound, when you use 1x4 or whatever to build a box and cover it, you have basicaly built a drum, period. The only way to stop this effect is to fill in the space though you can midigate the sound by using a sound absorbing material under the layout, like carpet and putting a skirt around it to assorb sound and keep it in the space. Yes you can eliminate most sound but it is very expencive to do, I mean true sound blocking or absorbing material will make most of your engines look cheap. I did experiment once with filling in the space and it did help but not as much as carpet and skirt but this was a fast experiment done without a sound meter, just a test.
I’m going to attack a big myth! Homasote does not have to make a big dusty mess when being cut!
Our club has recently cut a lot of Homasote for our new layout and I have to say that the mess was minimal. The key is the type of blade that is being used. Most blades have a set to the teeth so that the tips of the teeth stick out sideways from the core of the blade. We used blades that were ground to a taper instead of having the teeth bent outward. The resulting mess was easily contained and easily cleaned up. The taper ground blades don’t tear at the Homasote. Instead they cut the edge smoothly. There is very little airborne dust and what falls on the floor is easy to vacuum up.
My 30’ X 16’ layout is all L girder benchwork with 1/8" - 1/4" plywood with 1/8 clean corrugated cardboard glued to the top of the plywood with 1/2" to 2" foam glued to that. My track is glued to the top of that. The layer of cardboard acts as a vibration dampener. My layout is very quiet.
