Wing gap of the Biff?

[ST_Catchov]

I saw these skins and thought I rather like 'em, garish as they are, but surely they are fictional. But no, they seem to be based on historical paint schemes. This place is full of surprises. And so it got me thinking about the gap between the lower wing and the fuselage. It's very distinctive of the Brisfit and I'm not aware of any other ww1 kite with this particular wing configuration? Although I haven't looked hard. What was its purpose? I've always thought there must be a certain biplane wing gap measurement for maximum lift/efficiency, and in order to improve visibility (I presume), her top wing was set low necessitating the lower wing to be set beneath the fuselage. Was this the general idea or were there other reasons?

 

She was also renowned as a pretty tough old bird but you'd think the lower wing was a weakness? Looks can be deceiving I guess as she had a long distinguished career. A unique old crate.

 

 

 

[Trooper117]

 

Text book answer mate...

''The lower wing is fitted slightly below the fuselage so, with the standard biplane gap, the upper wing is set closer to the fuselage than it would normally be. This puts the average pilot’s eyes in line with the upper wing, which allows minimum impact of the wing in the field of view from the cockpit.''

[AndyJWest]

4 hours ago, Trooper117 said:

 

Text book answer mate...

''The lower wing is fitted slightly below the fuselage so, with the standard biplane gap, the upper wing is set closer to the fuselage than it would normally be. This puts the average pilot’s eyes in line with the upper wing, which allows minimum impact of the wing in the field of view from the cockpit.''

 

I can't help thinking they'd have done better to simply make the fuselage deeper. You aren't going to get any appreciable lift from that bit of wing, just extra drag.

[ST_Catchov]

Yeah, if it was all about better visibility then they should've just plonked the lower wing flush with the fuselage and raised the seats. 

[unreasonable]

No - because wings flush with the fuselage top are terrible for vision below. eg Bristol M1c: massive blind spot. (Unless you can get them behind the pilot as in a modern jet).  It is just geometry: to minimise the area the wings block from vision they need to be either far away from the eye, or oriented so that the eye is looking at the edge.

 

Hence almost all WW2 monoplanes are low wing. 

[ST_Catchov]

2 hours ago, unreasonable said:

No - because wings flush with the fuselage top are terrible for vision below. eg Bristol M1c:

 

Correct. However I meant the lower wing being flush with the bottom of the fuselage as per a normal biplane. This of course would mean the top wing would be higher than it is (according to the "biplane wing gap formula") thus negating the visibility advantage of the original design. But would it perform better? 

[Todt_Von_Oben]

Having another Chuck Yeager Moment here.  

[Cynic_Al]

I would say the lower wing positioned away from the fuselage may have been to prevent interference with the undercarriage mounting points.  Another possibility is that it was done to make the work of the armourers easier/safer by lowering the bomb-loading height.

 

I don't think it was an inter-plane distance issue, as that would be more easily addressed my increasing the stagger.

[unreasonable]

5 hours ago, ST_Catchov said:

 

Correct. However I meant the lower wing being flush with the bottom of the fuselage as per a normal biplane. This of course would mean the top wing would be higher than it is (according to the "biplane wing gap formula") thus negating the visibility advantage of the original design. But would it perform better? 

 

Oh I see - misread your comment. The pilot discussing flying the Bristol  (below) goes with the keeping the wing gap to avoid interference theory: that does not prove it but it seems plausible to me. I can see that the gap under the fuselage might be a bit of a drag trap, but given how draggy all these crates are, would it make much difference? 

 

https://haa-uk.aero/document/flying-the-bristol-fighter/

[ST_Catchov]

12 hours ago, Cynic_Al said:

I would say the lower wing positioned away from the fuselage may have been to prevent interference with the undercarriage mounting points.  Another possibility is that it was done to make the work of the armourers easier/safer by lowering the bomb-loading height.

 

I don't think it was an inter-plane distance issue, as that would be more easily addressed my increasing the stagger.

 

Interesting input as always Al.

 

10 hours ago, unreasonable said:

Oh I see - misread your comment. The pilot discussing flying the Bristol  (below) goes with the keeping the wing gap to avoid interference theory: that does not prove it but it seems plausible to me. I can see that the gap under the fuselage might be a bit of a drag trap, but given how draggy all these crates are, would it make much difference? 

 

Thanks for the link. I tend to agree. She had a pretty powerful engine so fast enough for the day. And thus I guess the drag was considered secondary in favour of good visibility and robust construction.

[unreasonable]

I suppose the engineers could have got rid of the gap entirely without moving the wings relative to the pilot, just by extending the engine/fuselage fairing down to the lower wing, giving a more tear drop shape. Perhaps they did and found it less aerodynamically efficient? Or perhaps they just assumed that the narrowest possible fuselage to contain engine, pilots etc was necessarily best without checking?

 

I cannot find anything about that  in J.M. Bruce, but since I can hardly find my own <insert body part here>  these days, that is hardly conclusive.  

[ST_Catchov]

1 hour ago, unreasonable said:

I cannot find anything about that  in J.M. Bruce, but since I can hardly find my own <insert body part here>  these days, that is hardly conclusive.  

 

You'll find it somewhere, somehow.  

 

 

But I think Troops pretty well nailed it. I had never really thought about or been aware of a "standard biplane gap" before. So it makes sense what the Bristol boffins did. And it worked pretty well with the Biff being in service with the RAF until 1932. Jolly good record. The Empire was secure.

 

On 7/28/2021 at 9:42 PM, Trooper117 said:

 

Text book answer mate...

''The lower wing is fitted slightly below the fuselage so, with the standard biplane gap, the upper wing is set closer to the fuselage than it would normally be. This puts the average pilot’s eyes in line with the upper wing, which allows minimum impact of the wing in the field of view from the cockpit.''

 

[Avimimus]

Other aircraft had this gap, including one of my favourites:

 

Honestly, I wish the community and the devs would lower their standards - their standards for amount of documentation, aircraft performance, and general 'common sense' - in order for us to have this spectacular plane. At its peak at least 32 of these single-engined twin-turreted gunships were in service.

 

The last Pfalz fighter to see production also had this layout (Probably at least 180 ordered, at least 74 fuselages captured, possible purchase by Austrio-Hungary contemplated):

 

 

 

 

 

[ST_Catchov]

I knew there were others Avimimus I was just too lazy to do the research.  That Salmson is amazing! But the gap between the upper and lower wings on both pictures appear larger than the "standard biplane wing gap" which has again got me intrigued as to the purpose of it all. Or is it an optical illusion?

[=IRFC=Gascan]

The spacing between the wings may be related to the cord from leading edge to trailing edge. A larger cord requires a larger space between wings to efficiently produce lift?