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 .

Pilot-34

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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.
That sounds like A wonderful improvement over most planes.
But why measure at the hips? Except for a very few women that’s not a persons widest point.
 

wsimpso1

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Wide enough for the folks to be adequately comfortable. Our Archer II is 42" wide inside and it is bit crowded with myself and wife in there. I designed the homebuilt to be 46" inside and it is definitely better sitting in it with her. The Mazda Miata is 53" inside, and it is wide enough for all but the really big folks.

If you and the other half are skinny minnys with narrow shoulders and so are your ancestors, then maybe a 40" wide cabin is OK, for those of us closer to 200 pounds, I would not dare go less than 46, and my ship would be full Miata is I were doing it again. Doors that go down to the wings too.

Then there is the staggered seating or Catbird approach, where hips and shoulders are offset fore and aft. That can take down cabine width while leaving shoulder room for everyone.

Billski
 

Pops

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Minimum is 42" . Anything over that is great.
Before the Bearhawk article came out in Sport Aviation in 10/95, I was doing drawing on a similar airplane. Steel tube fuselage, taildragger, Lyc-360, C- 175 wings and tails. Fuselage 48" wide at the cabin. 2 front doors and a sliding cargo door on the left side.
My old flight instructor called and said " stop your work on the airplane and buy these plans ". I did. I today's world, the FAA would never approved it.

Dan
 

Mark Schoening

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The 47 inch cabin in a Navion is really comfortable. Social distancing, ya know!
 

BJC

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My Sportsman is 44 at the hips, and 46 at the shoulders. Wide4 at the shoulders is a big plus.

I passed on the purchase of a pristine RV-6 slider because of inadequate headroom.


BJC
 

robertl

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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.
Just throwing my 2 cents worth in. Two years ago, I was checking out a C 150 to buy, the owner agreed to give me a test flight around the patch. I weighted 225 and he weighted 325 lbs. I had to let him get in the left seat first, then I squeezed in, and I mean squeezed ! He said we only had 16 gal of fuel so we should be alright and we flew with both windows open. It took a while to get off the ground but I was supprised at how well the plane flew. That being said, I would fly a C 150 anywhere, solo, and often do unless my passenger is small, other than that, the C 172 will fly me and most of my friends comfortably. I would love to have a VP II as a single seater though.
 

Toobuilder

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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.
I'm a proposal, contracts and engineering guy. Words matter. The title of this thread is very different (to me) than your stated intent above.

Given your clarification, to me, most instances of a cockpit more than 48 inches at the shoulders is "wide".
 

jedi

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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?
What I was thinking -
When the only criteria given is width and no trade off is required 48 " is a good number. No trade off was specified. Could be a facetmobile, flying wing, blended wing body, or other former examples with a wide airfoil shaped body.
 

Victor Bravo

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If the main question is "what do you think is wide", then my answer is 48 or above. If the question is "what do you think is wide enough" then the whole thing needs to have more information.

I've had a few B series Taylorcrafts, and their steel frame measure 39 inches across the shoulders a the door opening. Some of the post-war T-crafts had wooden formers that mounted the doors a little further apart, giving you a little more shoulder room, but without changing the tube frame. By most everyone's agreed definition, the T-craft is somewhat cramped, more so in the pre-war airplanes, and you definitely wouldn't want to be in there for four hours with another large guy. But in return for this discomfort, you have just about the most efficient of all the 1930's tube and rag airplanes.

My current airplane is an early C-172, which has more room in it for sure. Both width and height, and far far more "open and airy" feeling. The actual difference in width compared to the T-craft may only be a few inches but whatever it is... that makes a significant difference.

Sitting in a friend's NAvion raises the comfort level noticeably higher, partially because it is wider, and partially because you don't have the wing root right in your face like you do in a T-craft or even the 172.

Sooo.... the T-craft is "wide enough" for Young Eagles, or to take someone of average size flying for a quick lunch, and that's fine with me because I'm used to it. If I had a defined mission to fly a 500-1000 mile cross country, for business or to visit relatives every month, then the T-craft would not do it for me, the (early, narrow) 172 would be marginal, and I'd be looking for something the size of a NAvion to feel like it's enjoyable.

But with all of that drivel having been spilled out, I'm 100% with Toobuilder on the underlying issue: The question realistically HAS to be whether it's wide enough for my purposes - I have to figure out where on the comfort/efficiency/speed/cost curve I'm trying to be.
 

Richard Schubert

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My Rockwell Commander was 47" wide and it was just about perfect.
I do imagine that the opinions will greatly depend on the gross weight of the person responding.
 

Riggerrob

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I learned to fly in a Cessna 150 and always felt cramped. I stand 6 feet tall, broad-shouldered and weighed 180 pounds back then. I weigh closer to 200 pounds now. The C 150 always felt cramped with me and a similar-sized instructor. Wide-body Cessna 172 is the smallest "comfortable" airplane for me.
Cherokee 140 and GA Cheetah are also wide enough to be comfortable.

Staggered seats help with shoulder room. ... or just sling your inboard arm across the back of the other seat.
Hip width can be comparatively narrow, but I need elbow room to control an airplane. Perhaps the silly little elbow bulges from a Bolkow Junior ??????
The bulged side windows on a Feisler Storch also help with elbow room.

I suspect that Cessnas have such tall cabins to help pilots see - sideways - under the wing. I always hated that blind spot - obscuring the runway- as you turn a Cessna onto final approach. The pinched wing roots of Bolkow Junior and Zenith STOL help reduce the size of that blind spot.
 

cluttonfred

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I am glad to see that I have found another topic that folks are passionate about. A couple of replies...

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.
In the early and mid-1930s, Miles was having good success with their cutting-edge Falcon low-wing monoplanes including the 200 hp, four-seat Falcon Six. When a small air taxi service ordered a five-seater, they basically widened the fuselage to fit three across in the rear seat and added a little bit to the wing span and fuselage length. The result was the M.4 Merlin with the same Gipsy Six engine. It's interesting to compare the two:

M.3B / M.4

35' / 37' wing span
174 sq ft / 196 sq ft wing area
25' / 25' 10" length
2350 / 3050 lb gross
1550 lb / 1700 lb empty
800 lb / 1250 lb useful
180 mph / 155 mph max
160 mph / 140 mph cruise
1000 fpm / 900 fpm climb

I'm a proposal, contracts and engineering guy. Words matter. The title of this thread is very different (to me) than your stated intent above. Given your clarification, to me, most instances of a cockpit more than 48 inches at the shoulders is "wide".
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

From the reactions here, I get a sense that the "VP-21" concept I have been kicking around could benefit from a wider cockpit which should also actually simplify the construction in some aspects. In particular, I was thinking of "hip-width" cockpit with a bulged "shoulder-width" Malcolm hood canopy. If I push the cockpit width to something like 46-48" then I could eliminate that and go with simple, flat-wrap canopy design.
 

blane.c

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I voted other so here is why. If you are going to build wide anyway like 44 inches or 48 inches then you may as well just make it wide enough to put sheet goods in, so a 48 inch wide piece of material like plywood or sheetrock and in order to make that fit the outside dimensions are going to have to be in the neighborhood of 52 inches.
 

Vigilant1

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In the early and mid-1930s, Miles was having good success with their cutting-edge Falcon low-wing monoplanes including the 200 hp, four-seat Falcon Six. When a small air taxi service ordered a five-seater, they basically widened the fuselage to fit three across in the rear seat and added a little bit to the wing span and fuselage length. The result was the M.4 Merlin with the same Gipsy Six engine. It's interesting to compare the two:

M.3B / M.4

35' / 37' wing span
174 sq ft / 196 sq ft wing area
25' / 25' 10" length
2350 / 3050 lb gross
1550 lb / 1700 lb empty
800 lb / 1250 lb useful
180 mph / 155 mph max
160 mph / 140 mph cruise
1000 fpm / 900 fpm climb
They apparently changed a lot more than the cabin width. The wing has at least 45 additional sqft of wetted area, the tail should have gained some, too, and the additional wetted area of the fuselage was at least 40 sq ft-- all of it subject to scrubbing drag from the turbulent high speed flow from the prop. And, based on the change in allowable useful load, that new guy in the back seat weighs 450 lbs (so, more induced drag).

Let's take an apples to apples comparison: RV-7A (SbS) vs RV-8A (tandem). Same wing, same gross weight, same 200 hp engine.

Cruise speed at 75% power, 8k MSL:
RV-7A: 204 mph
RV-8A: 210 mph

About 3% difference, pretty much a wash.
 
Last edited:

Jay Kempf

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Last two projects I worked on both ended up 48" OML and 46" IML at the shoulders. Seems to be pretty comfy. Raptor went a bit over in many respects. More is always better until the cost weight and drag count optimization spiral slaps you back to reality.
 

cluttonfred

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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 voted other so here is why. If you are going to build wide anyway like 44 inches or 48 inches then you may as well just make it wide enough to put sheet goods in, so a 48 inch wide piece of material like plywood or sheetrock and in order to make that fit the outside dimensions are going to have to be in the neighborhood of 52 inches.
 
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blane.c

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I know lots of people that transport sheet goods all the time for cabin building. In two place aircraft the sheet goods are generally ripped in half so they are two foot wide and in both the two and four place planes the sheet goods are bolted together with usually all-thread rod and numerous methods abound for attaching to the fuselages. And of course there is the trip to the FAA to get your external load permit. It would be easier just to stuff the material in under the seats and close the lid.

 

TFF

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I think the question is what is the smallest cockpit you would get into with someone who is not your best friend or wife? Or best friends wife. You want it as wide as you can make it. That is the answer. Anything designed before 1945 is not really relevant. Different set of life rules. 1945 brought a lot of pilots who never would have been pilots without the war. They want Cessna 170s and Original Bonanzas as the smallest reasonable airplane. Each decade has added requirements that were thought not possible the decade before. No one thought a 170 would turn its self into a 206 or 210. You get into a Cirrus and all you say is this is how much room I want. No less. I could live with a 150. Takes an evolved person to say the same thing riding along. 30 min hops as a treat is no big deal in a tight cockpit. Don’t expect return customers. If you want to use the plane for going somewhere multiple times with the same people, they want room. They are going along for the tool aspect, they really are not digging the ride, just putting up with it. Personally not to worried about an over gross 150 as long as it’s off a paved runway.
 
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