Its the length of arm of my standard person who is 6' 9" tall. Since 99% people are shorter, it covers 99% of cases.
Uses in Widths
It keeps coming at all places where some width is occupied by a person:
- on bed
- on chair
- on desk when working
- on dining table while eating with others
- in corridor or door when walking or standing
It also keeps coming at all places where something is directly in front of a person:
- Depth of cabinet directly reachable by arms without stretching
- Depth in dining table directly reachable by hands without stretching
Uses in Lengths / Heights
Whenever we have to pass / put some person into something, we encounter this number:
- Length and Width of Mattress
- Height and Width of Door
- Height of Ceiling
Mattress
Width For A Person
A person laying on a mattress would occupy 27" unsqueezed. He would be comfortable but not most. He is laying straight with chest up and arms on side with a little distance from hips. No pain in this position. So 27" is the minimum width of a comfortable mattress (not bed, more on this later in this article).
The maximum width of a comfortable mattress, without any wastage, is 54". There is a principle, if 1 unit meets the basic needs, then 2 units is the most the person would use without waste and without saving. Anything beyond 2 units is either wasted or used as a saving. The saving thing is significant in money matters but we do not need it in mattresses.
The person can use a 81" wide mattress. More and its hard to use all of it. It can be used readily but is still a waste.
The 45" width is enough for:
- Comfortably laying down, with arms stretched at most comfortable angle i.e. 60 degrees.
- Turnings during sleep.
- Putting books, files, laptop at side.
- Having another person comfortably fit in, but only for a short duration.
- Having a child of age 10 or less, comfortably fit in, for a long duration.
If the mattress is to be shared by two people routinely then 81" width is fine. Not excessive, not miserable, just fine. Its because each person gets the necessary 27" and the remaining 27" is shared. For example one person stretch legs while the other stretch arms, thereby sharing the space.
Two people sharing bed, however, bring more problems than benefits. The turnings in sleep, lighting up to read a book, using laptop, getting out of bed to go to toilet etc unnecessarily disturbs the sleep of other. If two people have to share a room, then each of them must have a separate bed, with enough space in between the beds for each of them to get out and walk comfortably in dark without hitting anything. The in-between space can be used by a third person in emergency.
Length For Single Person
Pillows are usually about a foot long and 2.25 ft wide. Heads are usually 8" long i.e. palm-length. Therefore, about 4.5" top length of pillow is unoccupied.
4.5" must be left below feet for a good sleep.
Therefore, 9" extra length is needed in mattresses beyond person's height.
So for a 6' 9" person we should have 7' 6" or 90" long mattress.
Conclusion of Mattress Discussion
From the above, we have concluded that ideal mattress is for a single person and it is 7.5 ft x 4.5 ft.
Wood Thickness
Lets talk a little about the remaining portion of bed, the wooden structure.
The bed I am using since 11 years has a structure of 1" thick wood except at four corners where its 2" thick.
Ideally a bed should have 2" wide structure. The corners must be 4" thick. This is how beds used to be constructed till 20th century.
We can cut some corners by making corners 3" thick. With that altogether the bed would be 5' x 8'.
Further Thought About Mattresses
The above calculation was intentionally made large enough to fit in 99% of population. Infact for a general case, we do not have to go to that extreme. We can have a case for 93.75% with comfort that still fit in the rest (with decreasing comfort and the last one, the 6' 9" case just fit in with no comfort ).
Looking at my habit of using mattress, I notice that I never use more than 33" width at a time. If one hand stretch then other contract a bit etc. Also files, books and laptops are not meant to be put on bed, so we do not have to plan room for them.
My 5' 10" (= 70") uses 33". May be 36" is the real need.
I have tried 36" spaces and noted that they met all of my needs with one or two extra inches left.
5' 9" or less is height of 75" of men. Ofcourse women are shorter. Children are even shorter.
Length-wise 81" leaves the necessary 9" for even 6' tall people.
Only 6.25% men are taller than 6'.
May be the right dimension is 36" x 81".
Sometimes when people sleep, they stretch an arm to its full extent below pillow at side. On a 36" wide mattress, it has to go out of the mattress to hang in air. In 54" wide mattress we can guarantee that it would not happen in most of the cases.
An idea is to have two beds in each room, opposite to each other, fixed tightly with a side wall. Beds in this case are 1 meter or 40" wide (36" mattress + 4" structure). A 40" wide space is left in middle. Enough space to stretch an arm.
On the topic of stretching of arm, I have noted that when the arm goes outside the mattress, it seldom stretch more than 9", and atmost 12". Its because after 12" the part of arm still on mattress is unable to comfortably support the hanging part so the hanging part start to go down. So, atleast 12" space at each side is a generous thing for stretching arms.
If we do have to add 12 + 12 = 24 inches in the mattress width (not bed width because arms start hanging as soon as out of bed, not care how wide wooden structure is) then we get 36 + 24 = 60. Same number we have got before when we planned for wider mattress. If we add 9 + 9 = 18 inches, then its 36 + 18 = 54 inches, the previously proposed width of mattress.
So, no matter how we put it, we have to give each bed 5 ft x 8 ft space. Its better to have most of this space covered with mattress, as proposed before, than to have body parts hanging in air.
On Even Further Thought
Seems like a loop, got through many iterations but still don't find a dimensions that feels optimum.
81" length of mattress seems optimum. Fit in comfortably 6' or shorter. This covers 93.75% men, 96.875% women and 100% children. Altogether about 97.66% population.
Hard to decide about width, though some things are well-decided. Below 36" is pain. Above 54" is waste.
One advantage of 36" width is getting out of bed is one step, in 54" its two steps because the person have to move on side first. Another advantage is no waste, there is some built-in wastage in 54" width. Another advantage is killing of choice, a mattress is exactly for one person, no sharing (not even with a child), less choice means less headache.
Now about stretching of arms while sleeping. First of all very few people do this, and those that do it can be trained out of necessity to adjust. Second, my experiment showed that maximum 8" open-air space at each side of mattress is needed. We have to leave this space anyways at one side to walk out of bed. I am not planning for a system in which one can get out of bed only by the end because its a lot of pain.
About width of wood, I think 1" for structure and 2" for corners is enough. After all, my bed has not shown slightest sign of breaking up in 11 years.
So width wise: 36" mattress + 2" left corners + 2" right corners = 40" = 1 meter. Length wise: 81" mattress + 2" top corners + 2" bottom corners = 85".
Mattress = 36" x 81". Bed = 40" x 85".
Now about open space. At one side 8". At other side 16". The other bed would have its own 16" space, making the middle space 32". So, 36" + 8" + 16" = 60".
Some space have to be left at top of bed near wall. This have to be 8" as at minimum side. Since this gives an odd number 91", lets make it 7". So 5" between bed and top wall, 7" between mattress and top wall.
Final: Mattress = 36" x 81". Bed = 40" x 85". Total Space = 60" x 90".
No comments:
Post a Comment