How wide for a side-by-side?

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How wide should a side-by-side cockpit be in a light, two-seat homebuilt?

  • 34" / 86 cm

    Votes: 0 0.0%
  • 36" / 91 cm

    Votes: 1 2.1%
  • 38" / 97 cm

    Votes: 0 0.0%
  • 40" / 102 cm

    Votes: 3 6.4%
  • 42" / 107 cm

    Votes: 12 25.5%
  • 44" / 112 cm

    Votes: 8 17.0%
  • 46" / 117 cm

    Votes: 5 10.6%
  • 48" / 122 cm

    Votes: 14 29.8%
  • Other (explain in a post)

    Votes: 4 8.5%

  • Total voters
    47
  • Poll closed .

cluttonfred

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Off on a tangent...I’ve always been fascinated by utilitarian design and would love to see a homebuilt mini cargo plane designed for this sort of challenge. How about a 4’ x 8’ compartment under the floor for sheet goods, a reinforced box spar in the wing with integral tie down straps to allow long items to be loaded through a hinged wingtip, and a main cargo area capable of carrying the volume of, say, four empty 55 gallon drums and the weight one full 55 gallon steel drum (500 lb if water)? And let’s make it a Flying Flea to boot! ;-)
 
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Pilot-34

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OK, now I am confused. blane.c, how much sheet rock or plywood do you think folks transport in two-seat light aircraft? I would have gone the other way for a wood and fabric design...a maximum overall width just under 48" for efficient use of plywood sheets with the minimum number of scarf or butt joints.
I don’t think they transport very much at all.
But I think they want to!
Sheet goods are really handy for that cabin in the wilderness
 

Pilot-34

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Seems like the most practical way to design a cabin to transport those sheet goods would be standing on edge between the seats.
Of course having at least one removable seat would be very convenient
 

cluttonfred

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I was thinking that an underfloor arrangement would with the “plywood bay” approximately centered on the CG would be safest for weight and balance and leave the cabin unencumbered.
 

wsimpso1

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I am curious about folks replying with 48" since that's far larger than even typical factory-built aircraft until you get up to something like a Cherokee 6/Seneca/Saratoga. Are folks really willing to give up, say, 5 knots of cruise speed for those extra inches?
Yes.
 

Vigilant1

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I'd think sheet goods would best go under the cabin, flat against the floor. Secure with pins and a cable you pull from inside. Rig with a 'chute and drop it on the construction site.
If you are using an airplane to get cheap, bulky, heavy supplies to a remote construction site, the only explanation is that there's no servicable road to it. Sheetrock and OSB--fuggedaboudit, too heavy. Just light-gauge plywood.
 

Pilot-34

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I was thinking that an underfloor arrangement would with the “plywood bay” approximately centered on the CG would be safest for weight and balance and leave the cabin unencumbered.
What would you do with the space when you weren’t hauling plywood?
 

Pops

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Cabin about the size of my Dodge Mini-Van would be nice. Front 2 seats and room for a 4' x 8' sheet of plywood behind the seats and close the rear hatch.
Also sleeping room for 2 people for camping.
 

Toobuilder

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I am glad to see that I have found another topic that folks are passionate about...
I submit that this thread is posing as an engineering requirements discussion. "Passion" is found on Facebook.

...Well, a good portion of my career has been in public relations in a proactive sense, seeking to understand, inform, and influence target audiences. And this conversation is going exactly the way I wanted it to go. ;-p...
You have indeed influenced (also known as "corrupted") your data. It's worthless. For a good view of the difference between "proactive public relations" and "engineering requirements", check out the Raptor thread. Good stuff there.
 

Topaz

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There seems to be much made of the drag of a wide cabin for cruise. What about for takeoff performance?
@ScaleBirdsScott - Since nobody answered your question, takeoff-distance performance is most affected by power-to-weight ratio and the rolling friction coefficient of the landing gear wheels on the type of surface involved. Climb-out performance is most affected by power-to-weight ratio and span. In both situations, speed is generally low enough that parasite drag is a minor factor.
 

ScaleBirdsScott

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Climb-out performance is most affected by power-to-weight ratio and span. In both situations, speed is generally low enough that parasite drag is a minor factor.
Thanks for responding. That's pretty-much what I thought but, always curious if I was missing something.
 

cluttonfred

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Wow, somebody needs to cut back on the caffeine. This is a discussion forum not Lockheed Martin.

You have indeed influenced (also known as "corrupted") your data. It's worthless. For a good view of the difference between "proactive public relations" and "engineering requirements", check out the Raptor thread. Good stuff there
 

RogFlyer

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Ahhh, anthropometry - a vexed subject.

Here is a study of US military personnel from 2012, with many body distance measures. It is perhaps not representative of the entire US population as it selectively avoids very small (height and weight) and very large people (height and weight), and the elderly - they simply don't get recruited.


A short extract from the Bideltoid breadth table, p65, and reference to the statistical info p66.

Percentile Female Male
5 40.6 45.9
25 43.0 48.9
50 45.0 50.9
75 46.9 53.1
95 49.9 56.7

These dimension sets are close to normally distributed. Given one knows the mean and standard deviation AND the two people are selected randomly one can calculate statistically the percentage of the population that will fit a given cabin width. This is left as an exercise for the reader 🙃

Now we move into psychology. Clearances between people in various positions are a much more vexed and contentious subject. Quietly sitting people prefer to sit with a minimum of 3.5cm of clearance from a wall, and with about 5.5cm of clearance from another person. Allows a little wiggle room without frequently touching. If each person has something to do, then particularly the inter-person spacing increases. For instance, diners report a comfort distance between shoulder widths of approximately 18.5cm, rather than the 5.5 used here. Plant operators minimum is approx. 80cm and preferably of the order of 100cm and that is "to wall" as well.

People will sit jammed against a wall so as not to touch another person, particularly if they do not know them very well. So the minimum distance between a hard surface and the shoulder width could be considered to be zero. Equally, two people will sit with their shoulders touching (0cm), or indeed interfering (-1cm) . But this is tolerable only in the short term. Interestingly, there has been a study - but not peer reviewed - which indicates that, given no other issues - bo, sweatiness, bare skin - total strangers will tolerate this level of proximity for longer than people who know each other socially. Don't aske me how they defined the level of knowing! Also, if people know that there is a physical, practical reason for the space being cramped, they will tolerate a smaller spacing for longer, as well.

A cabin width of 106.2 cm (two 95 percentile males) will be wide enough to fit around 99% of randomly selected pairs. Adding "comfort" spacing of 12.5 cm gives a cabin width of 118.7 cm (or 46.7") - call it 120cm or 47.25".

A cabin width of 81.2 cm will fit two 5th percentile females, or around 1% of randomly selected pairs. Adding the comfort spacing of 12 cm gives a cabin width of 93.7 cm (or 36.9").

A cabin width of 114.3 (two 50th percentile males plus comfort) will fit approximately 93% of randomly selected pairs. (Or 45").

Please note that family members do not meet the randomly selected requirement. Friends typically do not, either (birds of a feather is a cliché for a reason).
 

Toobuilder

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Wow, somebody needs to cut back on the caffeine. This is a discussion forum not Lockheed Martin.
And once again, someone who wants to play airplanes/engineering impugns the experience of someone who lives airplanes/engineering. If you want to entertain yourself with endless opinions, I hear Facebook has that.

Just be advised that your pool of technically knowledgeable future participants has now been reduced by one.

Fool me once...
 
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