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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I'll make this quick. Our own Ron W. has done some great work over the years documenting actual cockpit dimensions of homebuilt aircraft. I like the VP-2, but pretty much everyone agrees that it's a bit too small even in open-cockpit mode and even worse if enclosed. So, for light two-seat homebuilt (think LSA or European microlight), how wide should the cockpit really be?
 

TFF

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46-48”. That’s two seat plane 150, RV7, Grumman AA1. I’m broad shouldered. I usually have to put one arm behind the other seat if not flying. 52”would feel like a king. Aero will Is another story. If you are building for anyone who might want a ride, it can’t be tighter. Even if everyone is 150 lbs, room makes people happy.
 

TFF

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I correct my self. 150 is 37 at the top and 35 at the hip. AA1 is 40. Just did a quick measure. For me 44 is the only way I’m not touching shoulders. I will fly a 150 with someone; not much fuel if legal.
 

Toobuilder

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Not enough information. Is this dimension bounded by cost, producibility, market penetration or is it a one off for you.

In other words (as always), what are the requirements? Define that and you have your answer.
 

cluttonfred

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Deliberately left open, Toobuilder, just trying to a get a sense of perception. I did say that we are talking about LSA/microlight here, so relatively light and small with modest power.

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?
 

Toobuilder

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But you can't leave that "open"... My answer for something to appeal to the mass market will be different than if I was looking for speed, or light weight, or manufacturing efficiency... You are asking the philosophical equivalent of "how long is a piece of string?".
 

cluttonfred

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Not really, like I said, just trying to get a sense of what people perceive as "wide" in a two-seat, side-by-side light plane.
 

Pilot-34

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5 knots ?
In a heart beat !
Where are the real numbers ?
56 is crowded 60 is the bottom end of comfortable.
If I’m going to build it for me it’s gonna be comfortable
 

mcrae0104

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I could sacrifice some width in a two-seater if I knew I would only be taking a (skinny) passenger occasionally, if I could do the drag trade-off calculation to see how much speed and/or range it would buy me. I think this is what Toobuilder is getting at. 42"-44" is pretty good for cruising, though, if that's the most important consideration. I've not flown a Cirrus, but the listed 49" sounds downright luxurious compared to what I'm used to.

Have you set up a couple of chairs and sat down next to a "passenger" with a piece of cardboard leaned up against your shoulders to measure a comfortable width? Seems to me a crude mockup is in order.
 

Vigilant1

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Just to mention it: Frontal area doesn't need to be a predominant factor in total drag in cruise if we pay attention to the shape of the airframe. Autoreply posted some pix of a sleek but spacious side-by-side sailplane when I was ribbing him about the sofa-width cabin he was specifying for his version of the Beetlemaster.

And a small gripe for Cessna: Okay, you made this C-152 cockpit 39" wide to reduce weight and frontal area. Got it. So why is the cabin so tall? I'm 5'11" and I could wear a top hat in here. How about moving about 4" of this height to the cabin width?
 

Hephaestus

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48" for two, unless I'm riding with a beanpole who doesn't mind getting very friendly... I'm taking at least 25-26" of that - however 23-24ish is possible if sidestick, ergonomics are well thought out and I'm not reaching around a bunch to grab carb heat, mixture etc (think HOTAS)
 

Mad MAC

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Looking at this list there are a number of production GA that are 48" wide Piper Saratoga, Piper Seneca & Cessna Corvalis . There are some GA aircraft that went faster when the cabin was widened.


As for cabin height I get sick of banging my head on the canopy, some of us have short legs & a long back.
 

lear999wa

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My design is for a 3 seat/semi staggered 138cm 54.5” wide at the hips. The canopy does bulges out slightly to allow for a few extra inches elbow room on either side. It should be cosy inside with all seats filled.
 

Grelly

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If you are designing something, you could always stagger the two seats enough that shoulders, elbows and hips don't need the same space.

To answer your question, I guess I am about medium width-wise and I find a C172 adequate. So 42 inches would be my design goal.
 

Pilot-34

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If my son and I are sitting in the 172 we have to sit staggered I can’t imagine designing something from the get-go with the word adequate involved.
 
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