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Vertical Positioning of the Wing in the Fuselage

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EvilC5719/12/2019 16:41:32
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In my post entitled 'Black 5 twin IC from Sarik Hobbies - Anyone Know it?' here - which I'm planning to build, I wrote about the Black 5 having a bit of an ugly slab-sided fuselage.

This being the case, I've located a plan for a similar twin IC model called Fifty Caliber, by Dick Sarpolus. This has a much prettier fuselage, which I'm hoping to be able to re-scale & redraw, and transplant onto the Black 5 plan instead.

My question regards vertical positioning of the wing: The Black 5 (the one with the ugly fus) was designed as a tail dragger, with the wing positioned half way up the height of the fuselage. The Fifty Caliber (the pretty one) was designed with a tricycle undercarriage, and the wing is nearer the bottom of the fus - albeit with the usual small box fairing underneath.

In other words, what is the vertical positioning of the wing in the fuselage a function of? If you look at (for instance) a DC3, it's a tail dragger, yet the wing is underneath the fus.

Presumably the tail needs to be kept up clear of any turbulence coming off the wing, but other than that is wing vertical positioning important?

Edited By EvilC57 on 19/12/2019 16:43:15

Edited By EvilC57 on 19/12/2019 16:44:55

Jon - Laser Engines19/12/2019 16:59:17
5067 forum posts
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Usually it depends on what stuff you have in the fuselage. If its people or cargo you put the wing above or below the cabin so its not in the way. if its bombs you can put it in the middle with a space above for the crew and below for the weapons like the lancaster did.

In the case of full size the wing will usually go where it is most efficient and least in the way. In a model it can probably go more or less anywhere.

kc19/12/2019 17:38:55
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The curved looks of the Fifty Caliber seem to be achieved by bending the side in a little at the top and using a 1/2 thick top sheet. Almost any fuselage can be rounded by using triangular balsa at the corners and shaping with a razor plan. Anyone who has built an AcroWot or simlar construction model knows how the basic box is transformed into a shapely fuselage by the razor plane. It's a basic aeromodelling skill - needs to be done evenly on both sides and in an arc.

Easier to round the Black 5 fuselage than rework the wing position! Or just build a Fifty Caliber.

EvilC5719/12/2019 18:11:10
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Hmm.

As you can see from the pics below, the Fifty Caliber and Black 5 fuselages are very different animals. I am aware of the facilty to round turtle decks etc. by adding triangular stock inside a fus and attacking it with a razor plane and perma-grit block (I've been at this game a while). However I think the Black 5 fus would need more than just a little reshaping here and there to make it look attractive. The other way of looking at this, is to just build the Black 5 'as is', put up with the ugly looks (to my eyes), and just revel in the sound of those two RCV 4-strokes burbling away! wink

fifty caliber.jpgblack 5-3.jpgblack 5-2.jpg

Peter Miller19/12/2019 18:26:58
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Well ypou could always do a planked fuselage

des flt4.jpg

kc19/12/2019 19:05:00
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The Fifty Caliber's elegant looks come from having a longer sleeker fuselage and a tapered wing. Also the colour scheme and stripes affect the look.

The Black 5 could have the fuselage top sheets come apart a bit at the top blended into a thick top sheet and use triangular in the corners. Then rounded. A glazed cockpit could be fitted instead of the Hots style wood 'cockpit'. More work! But a sleek colour scheme might change the stumpy fuselage looks. Putting sunburst colour on a straight wing can make it seem more elegant rather like a tapered wing. It's common to see squarish models looking better than they are by clever colour schemes.

EvilC5719/12/2019 19:14:18
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Some food for thought there...

kc19/12/2019 19:18:38
6206 forum posts
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A prettier 62 inch twin is Doublet.

Much easier to build exactly to the plan than modify, depends whether you like redrawing plans and working out all the new former shapes etc.

Nigel R19/12/2019 23:23:54
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Dido sarpolus magnum 80 is already the right scale for two 45 two strokes or two of your rcvs.

The Black 5 has a utilitarian charm of its own.

Denis Watkins20/12/2019 06:47:33
4054 forum posts
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Posted by Nigel R on 19/12/2019 23:23:54:

Dido sarpolus magnum 80 is already the right scale for two 45 two strokes or two of your rcvs.

The Black 5 has a utilitarian charm of its own.

yes Agreed

And structurally, that fuselage is very rigid, designed for quick build and stable tailfeathers

Simon Chaddock20/12/2019 10:03:05
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In pure aerodynamic efficiency terms it is better to have the wing approach the fuselage surface at 90 degrees. This is particularly important if the fuselage is rounded or circular.

In many cases the vertical wing position is set by the need to keep the undercarriage short even if this means complex wing fairings as in the Spitfire.

A 'bent' wing, as it the Corsair, is a solution that gives both 90 degrees approach and a short undercarriage.

In general wing turbulence only becomes a serious control problem at 'stall' angles of attack by which time the nose high angle of the fuselage means the tail plane is likely to be below it.

A "T" tail is a solution to keep the tail plane above the turbulence but it may require a really tall fin if the wing has big turbulence inducing high lift devices as in the Boeing C17.

On the other hand models tend to be aerodynamically inefficient and relatively powerful compared to full size so any benefits of wing position may not be apparent. wink 2

Nigel R20/12/2019 10:31:55
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Forgot to mention, the Magnum 80 is a download from Aerofred.

The successor design, Big Apple, is on Outerzone. This is similar size and area to the Magnum, but the wing is slightly swept, has flaps and retracts are shown.

Another Sarpolus twin is Lotsa Watts, electric this time, about 80" span again, but maybe gives a different style fuselage idea:

**LINK**

Bob Cotsford20/12/2019 11:55:16
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Posted by Simon Chaddock on 20/12/2019 10:03:05:

In pure aerodynamic efficiency terms it is better to have the wing approach the fuselage surface at 90 degrees. This is particularly important if the fuselage is rounded or circular.

In many cases the vertical wing position is set by the need to keep the undercarriage short even if this means complex wing fairings as in the Spitfire.

A 'bent' wing, as it the Corsair, is a solution that gives both 90 degrees approach and a short undercarriage.

In general wing turbulence only becomes a serious control problem at 'stall' angles of attack by which time the nose high angle of the fuselage means the tail plane is likely to be below it.

A "T" tail is a solution to keep the tail plane above the turbulence but it may require a really tall fin if the wing has big turbulence inducing high lift devices as in the Boeing C17.

On the other hand models tend to be aerodynamically inefficient and relatively powerful compared to full size so any benefits of wing position may not be apparent. wink 2

Certainly with the Corsair the bent wing was as much to accomodate a large enough prop to absorb the engine power while keeping the u/c struts short. This applies to a lot of prop powered multis where a high wing allows for prop tip clearance on wing mounted engines while allowing easy access to the low slung fuselage. The Liberator is a good example of this.

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