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Coil ILD Rating/Equivalent 20 Mar 2021 17:15 #1

hey all

building a diy twin for a guest bedroom, sort of using it as some level of experimentation as well

i often see a:

(bottom --> up)
1" foam
6/8" bolsa springs
3" latex topper (still on the fence about talalay v dunlop, but another topic i suppose)

as a standard hybrid recommendation

however, i can't find the bolsa springs in a twin format anywhere. so looking at foamfactory, they have 35 and 50 LB (1.8 and 2.8 density) available

what would be the spring equivalent in the foam size? please recommend a density, thickness, and firmness. ie 6" of 35lb 2.8, or maybe it's a combo 3" of 50lb under 3" of 35lb both 2.8? maybe a split density (although i feel like density = longevity based on my readings, so should always snag up the higher one for a foam base)

just trying to get a simple 2/3 layer twin bed for a spare bedroom, and to give the diy thing a shot. shooting for medium firmness that sort of helps a wide range of potential guest sleepers

thanks!

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Last edit: by datrumole.

Coil ILD Rating/Equivalent 21 Mar 2021 07:38 #2

Couple things here. First, I would try APM to see if Ken could actually order you a twin Bolsa coil setup for your DIY.

www.mattresses.net/quedelbo.html

Second, I think there is some confusion about how foams are characterized. The two main characteristics to distinguish foams are density (how much it weighs per unit of volume, often you'll see something like Lbs/ft^3) and load deflection (how hard it pushes back for a given area and deflection, often denoted as ILD or Lbs/inch). The density tells you the quality of the foam (higher density means the cell structure is more robust and thus it will likely continue to push back at it's rating for longer than lower density foams). The load deflection rating tells you how hard it pushes back as you press further into the foam. It's this second stat you are looking to compare to the springs since the springs also have a rating of Lbs/in but most manufacturers don't provide these on coil layers so you'd have to test it yourself (or have someone that had one test it) to figure this out. The other issue is that the foam response will likely be very different than the springs (graph of springs is straight line versus foam is curved) so I suspect you will find they don't act the same at all even if you can find ones with a similar ILD ratings since the rating usually comes from a specific deflection amount (like 40% compressed) whereas the response at other deflection amounts will not match at all. I know it's a a bit technical but I hope this makes sense why the comparison doesn't work.

If you are tied to the idea of using polyfoam then I'm sure some of the member manufacturers could recommend something that would work well in your application.

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Coil ILD Rating/Equivalent 21 Mar 2021 11:33 #3

thanks!

so i think i'm clear on the ILD v Density now, appreciate it. that said, sounds like you should always opt for a higher density when budget allows pending it's offered in the ILD you were shooting for

and also, sheds some light on foam v coil. coil being linear and foam not in it's firmness

i think for simplicity for it being a spare, i'd like to shoot for foam. less layers i suppose to deal with

i'm thinking a:

(bottom --> up)
6" 35lb 2.8 poly

with either

2" memory foam + 2" 20ILD dunlop latex (SOL)
or
1" 14lb 1.5 poly + 3" 20ILD dunlop latex (SOL)

trying to shoot for 10" since the cover comes in 8 or 10 hence the 1" filler foam

i had a chance to lay on talalay at a local spot near me, i've got an order of dunlop on the way as a topper to check out the differences to feel for myself if the talalay is worth the extra premium

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Coil ILD Rating/Equivalent 21 Mar 2021 11:36 #4

weird, edit seems to be missing?

correction above: 1" 12lb 1.2 poly

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Coil ILD Rating/Equivalent 21 Mar 2021 16:29 #5

thanks!

so i think i'm clear on the ILD v Density now, appreciate it. that said, sounds like you should always opt for a higher density when budget allows pending it's offered in the ILD you were shooting for


Yep, exactly.

I'd go with a poly foam that was at least 2.8lb/ft3 or better density and in the 35-36 ILD range would probably work well as a base layer. Depending on what feel you're going for then you can add dunlop as a mid support layer and then poly or memory foam (4-5lb/ft3) is fine to top it off or you can use talalay latex if you want a more springy supporting feel on the surface. You can play around with different foams to see what you like best since everyone has their own preferences on that.

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