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Old 28-10-2006, 06:25   #16
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Originally Posted by hellosailor
Slowshoes-
IIRC the density of foam is measured or rated on a "durometer" scale. 20 would be the stuff that flattens under you right away, 90 would be too stiff to sleep on. IIRC the 40-60 range is for more durable upholstery, and when I picked something higher than recommended for mattress foam...All I can say is resist that urge.<G>
A good foam supplier will be able to make up laminates for you, too. They commonly will take an inch or two or the softer foam, and glue it onto twice as much of a thicker foam, so you get more conformity on the top but more cushioning from the whole. They glue the stuff up in 6' rolls, etc., in minutes.
If you don't specify closed cell foam--you won't get it. IIRC most upholstery foam is open cell on purpose, so it can breath. Of course boats aren't most places.<G>
Hellosailor,

So is the recommended 40-60 range for foam a closed cell foam then? Is the laminate that you mentioned typically made up of open cell laminated to closed cell? I had the impression that you were recommending the softer open cell foam, until I read the last line in your post. Thanks for any further info.
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Old 28-10-2006, 08:01   #17
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Foam comes in a wide variety of density and compression IFD (Indentation Force Deflection).

Density - Affects foam durability & support. Typically the higher the density the better the foam. A higher density foam will retain its original properties and provide the support and comfort it was originally designed to have. Densities range from 1.0 lb per cubic feet to 5lbs per cubic feet.

IFD-Indentation Force Deflection is a measurement of foam firmness. Foam can have a high density and be soft, or have a low density and be firm, depending on the IFD specifications. IFD range from 10 to over 100.

Although there is no industry standard for characterizing firmness, follows some general guidelines:

Soft: IFD 14 - 34 ~ Density 2.0 - 2.5 lb/ft3

Medium: IFD 19 to 40 ~ Density 2.8 to 3.0 lb/ft3

Firm: IFD 28 - 45 ~ Density: 3.0 - 3.2 lb/ft3,

Very Firm: IFD: 36 - 50 ~ Density: 3.2 lb/ft3,

Rigid: IFD 60-70 ~ Density over 3.2 lb/ft3
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Old 28-10-2006, 14:12   #18
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So Gord, outside the lab and inside the upholstery and foam store...if you ask them about how cushiony the foam is, which of those words are they going to use, and which ones will they slap your face for?<G>
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Old 28-10-2006, 16:24   #19
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Cushions

I put two layers of carpet underlay down covered with two layers of thick carpet ,covered by the pvc coated 3 oz dacron ,which is the same price as naugahyde, but much tougher , on my berth cushions. I wrapped it around the foam and stapled it to the plywood bottoms. No more back problems.
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Old 29-10-2006, 04:08   #20
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\Polyurethane Foam Specifications:

Foam mattresses are made mainly of materials such as latex foam, viscoelastic (memory) foam and polyurethane foams. The primary properties, that affect design considerations, and with which distributers should be familiar are:
Density
Firmness (IFD)

Compression Modulus (Support Factor)
Flex Fatigue
Resilience

Density is a measure of weight (pounds per cubic foot) and it is unrelated to firmness. Generally, as foam density increases, comfort and durability also increases.

IFD is the measure of foam firmness, and is independent of density.
IFD is measured by indenting a foam sample 25% of it's height. The amount of force (in Lbs) required to compress the foam is it's 25% IFD.
Even high density foams can be soft. For upholstery, 25 percent IFD can range from five pounds (super soft) to 80 pounds (super firm). Softer foams may be laminated to firmer foams to provide surface softness.
Surface Firmness is the resistance to compression near the surface of a mattress. It is measured by the surface Indentation Force Deflection (IFD) measurement.
Deep Firmness is the IFD under severe compression.
Support Factor is another IFD measure, taken by indenting the foam 65% of it's height. Typically, the greater the difference between a product's 25% and 65% IFD (the Support Factor is the ratio of the two), the greater ability to support weight. Support Factors range between 1.5 to 2.6

Compression Modulus is primarily a function of the type of foam. Conventional foams have compression modulus in the range of 1.9 to 2.1; filled foams 2.1 to 2.4; and high resilience grades 2.2 to 3.0. Within a foam grade, the modulus is typically a function of the foam density. In most cases, the higher the density the greater the compression modulus.
Laminating hard and soft foams together can also increase compression modulus for the composite cushion structure. However the firmness of the laminated foams cannot be too far apart or the cushion may seem to "bottom out" on the firmer portion.

Flex Fatigue is an important measurement of durability, and an indicator of a cushion's long term ability to provide the proper cradling and TVM (Total Vertical Motion). Foams that have good flex fatigue values will tend to retain their original firmness and support levels, which means that the cushion can retain more of its original characteristics.

Surface Resilience also affects comfort an design. Foams with high resilience feel springy and provide a good "hand" for cushioning.

HTH,
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Old 29-10-2006, 10:38   #21
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Slowshoes-
They can laminate up anything to anything. What I'd seen was for home use, which is all open cell foam. Closed cell foams are, from what I've seen of them, always much stiffer.
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Old 30-10-2006, 14:43   #22
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Cushoins

I think what really counts is how your back feels the next day, regardless of what numbers and theories may say.
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Old 31-10-2006, 04:22   #23
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Originally Posted by Louis Riel
I think what really counts is how your back feels the next day, regardless of what numbers and theories may say.
Brent
I agree - and that is what has me considering open cell foam over closed cell foam. Many years ago, I had a dockside neighbor who had cushions made up in closed cell foam, and they were so firm it was to the point of being uncomfortable. If closed cell foam is no more comfortable today, then I will go with open celled foam and settle for less durability.
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