Folding Wings, Aircraft Trailers, and Portable Hangars for Inexpensive Storage

[cluttonfred]

One of the Fauvel motorgliders was mentioned earlier, with the nosecone and rudders removed or folded 90° to the side to fit on a trailer sideways. I have often thought that a powered Backstrom-style straight plank flying wing would make a great trailerable plane.

The idea would be to keep the fuselage length under legal towing limit, preferably closer to about 7' 4" (2.25m) or so (more on that later). I'd use a tractor engine installation with the pilot (and passenger in a side-by-side two-seater) sitting on the wing spar to minimize CG travel, so a low wing. You'd need an engine installation which was compact in length--maybe an HKS for now, though someday an electric motor would be idealThe bane of pure flying wings is often directional stability, but it would be easy to rig up a rudder on a boom, in fact, it could be a fixed fin if you wanted to use drag rudders on the wingtips, or it could be an all-moving fin or a fixed fin and a conventional rudder. The boom could be secured by a couple of pins, plus another one for the pushrod to the rudder if needed, a two-minute job disconnect and remove or fold to one side, or the reverse.

The reason for that draconian length limit of 7' 4" (2.25m) is that it would allow the aircraft to be stored in an unmodified ISO shipping container--a light single-seater in a 20' containers or two of them in a 40' container, or one two-seater in the 40' container with room for some storage at the end. All you'd need is a simple trolley, it could just be a wooden platform on wheels and some 2x4 planks nailed to the floor of the container.

To go flying, you open the container doors, pull out the plane on the trolley, attach the boom and rudder, push it off the trolley, wheel the trolley back in the container, closes the doors and finish your normal pre-flight. When it's time to go home, you do it in reverse, easy-peasy. For trailer storage like a gilder, you'd wouldn't even need the trolley, just ramps for loading on a trailer that opens down one side like a Coca-Cola truck or maybe tips to the side like an eyeglasses case.

What do you think?

PS--Hot Wings, your folding fuselage sketch also brings to mind some interesting options for planes to fit inside an ISO container or long narrow trailer.

 

[autoreply]

After a lot of messing around, I've concluded that it's pretty much impossible to get a fuselage that's shorter as 2.50 meters, let alone 2.25. Even the Mistral (engine above feet) doesn't come close if you cut off the fuselage behind the pilots.

 

[Rienk]

Take a look at the U-2 and the Dyke Delta fold. The U-2 could be modified so that the folding hinge point is completely separate from the attach pin. Add the captive auto-connect mechanism (they aren't all that heavy) along with sliding pin to join the 2 halves and your basically there.

But don't forget about folding the fuselage as well. There is nothing wrong with an asymmetrical fold line. The same captive auto-connect mechanisms for the ailerons can be used for the rudder and elevator as well. Here is a quick sketch to give a visual:

For my Ultralight design, I only need to remove the wings and store them alongside the fuselage.

However, for the folding Airplane design (still a pipe dream), I want to do something like the X-14d I had for quite a while. Basically, I want an airplane that can fold up and be stored inside a 4'x4'x8' crate (or the back of a van or pickup).
Thus, the wings each need to fold in half, the tail group needs to come off and fold up, and the rear fuselage needs to come off (or fold 180 degrees back on itself).
All of this, while having automatic controls? This is the main reason I haven't built it yet.
On the X-14, the setup time was lengthy, and there were literally dozens of places where a mistake could be made - not something I want to do.

Max length of any part is 7.5'.
If the wings fold in half, each half-span can be no more than 15' - but only 13' usable if I have to allow for 2' of spar overlap inside the fuselage. Two half-spans at 13' plus 2' of fuselage gives a potential wing span of 28'. At an AR of 10, and a taper ration of .7 (30" tip, 40" root), the max wing area is 82 sq.ft. - more than enough for a light single-seat aircraft. Frankly, since the empty weight is probably going to be less than 380 lbs, 72 lbs of fuel, 250 lb pilot, and even 50 lbs luggage, the wing loading would only be 9.2 psf, which is significantly less than what is needed for LSA. I might even go up to 12-14psf, which would only require a 54-63 sq.ft. wing area, or a 24' wing span (24" tip, 34" root). That would be a 11' half span plus the 2' in the fuselage, or a 6.5' long package.

The front fuselage (with engine) would also have to be less than 7.5', from spinner to seat rear-bulkhead. The rear fuselage could only be 7.5', and whether that includes the tail feathers would have to be determined. Regardless, the overall fuselage length would be no more than 15' - unless the rudder were detachable, then maybe 16'.

Use teleflex type cables for elevator and rudder?
Use struts to hold the Hstab and rudder in place, or make it removable like on gliders (whether on bottom, or top like glider?).
Folding wing, with 6' aileron and 4.5' flap - and automatic connections for both?

This is the paper excersize I'm going through right now.
If I can come up with viable solutions, I may even work with a friend of mine to build it next year.

 

[Head in the clouds]

BTW how goes the Ossie Mossie ?

Yeah Alan - what progress on the mozzie? Long time and no updates. We need a progress report mate. Phil

After a lot of messing around, I've concluded that it's pretty much impossible to get a fuselage that's shorter as 2.50 meters, let alone 2.25.

AussieMozzie - long story. On the Aussie recflying site I'd been running a thread a bit like the 'Challenge' thread here, but it was about a 'Cheap 2 Seater', and very similar to this thread and the 'Cheap Aircraft Impossible' thread, '$5500 Aircraft' thread etc, all rolled into one. The desirable/possible configuration came out to be -

2 side by side seats
Enclosed cabin - doors on or off
Tri-gear
Tractor
Cheap
Factory-built option
Quick-build kit option
Assemble kit with basic hand tools only (and simple so anyone can do it)
Very quick folding (less than 2 minutes)
Folds to fit 20ft ISO container and/or legal road trailer size
Preferably meet the Euro 450kg microlight class as well

Pretty similar requirements to these threads really, so at least we know folks in different parts of the world are wanting something along similar lines. As the new design came together I was approached by someone wanting to manufacture and market it and so OzMoz got put on the sideline as I developed it further (lots of CAD work). After several months the expected contracts and agreements from the manufacturing side hadn't materialised and I'd had other approaches so I had to get more of the fine detail completed. So OzMoz has had to take a back seat temporarily while the Cheap 2 Seater (C2S) gets all the attention for now. The reason being that the Moz is very complex and never likely to be produced in numbers whereas the C2S looks like being very simple to manufacture and should retail cheap enough to create a reasonable demand. It should be in a similar price bracket to the X-Air Standard and the Skyranger Swift i.e. $36K-ish built, $28K-ish as a quick assembly kit. If I didn't have some pretty heavy duty 'real' work to do as well right now I'd only be about a month off getting the prototype under way.

As autoreply says, getting the length below 2.5m/8ft 4in is quite a challenge, but not impossible, and I'd say that there aren't too many configurations which would allow it to be done. Mine comes out at 5.8m long x 2.2m high x 2.2m wide (19ft x 7ft 3in x 7ft 3in) on the trailer or in the container. No dolly is needed to get it in the container lengthwise. The aft fuselage partially collapses and folds sideways. The span is actually a bit more than 5.8m courtesy of quick detach wingtips. There could be a long-wing version because it works fine structurally, that would legally fit the motorglider category, and it would have very STOL capabilities with commensurate very slow flying/loitering characteristics. It would need a 40ft container or longer trailer.

The very quick (2 min) rig and de-rig is achieved because there are no wings to remove and no need to disconnect or re-connect any controls, the aft part of the elevator and rudder control linkages is cable, and the cables just go slack as the tail is collapsed and folded sideways.

 

[Doggzilla]

After a lot of messing around, I've concluded that it's pretty much impossible to get a fuselage that's shorter as 2.50 meters, let alone 2.25. Even the Mistral (engine above feet) doesn't come close if you cut off the fuselage behind the pilots.

I was reading that the ideal subsonic length to width is about 4.2:1, if you are looking for the perfect ratio of skin drag to parasitic drag.

Having a raised engine pod seems to have worked well for Lake, in that it outperforms aircraft of conventional configuration. It also seems to work well in gliders with retracting engines. Since the tech already exists, perhaps a folding engine mounting could be the tipping point.

 

[autoreply]

After a lot of messing around, I've concluded that it's pretty much impossible to get a fuselage that's shorter as 2.50 meters, let alone 2.25. Even the Mistral (engine above feet) doesn't come close if you cut off the fuselage behind the pilots.

Just measured this. Not true; spinner to rearmost point of the seats is 228 cm. You'd still need a detachable fairing of some sort (plus a tail)

I was reading that the ideal subsonic length to width is about 4.2:1, if you are looking for the perfect ratio of skin drag to parasitic drag.

Having a raised engine pod seems to have worked well for Lake, in that it outperforms aircraft of conventional configuration. It also seems to work well in gliders with retracting engines. Since the tech already exists, perhaps a folding engine mounting could be the tipping point.

You still need to fair in the pod. The theoretical ideal might be very fat, stubby fuselages, but the flow around the wings forces other optima. The easiest way to reduce fuselage drag is to decrease frontal area (by canting the seat backwards). This makes the cockpit longer, but the fairings shorter, resulting in an overall shorter fuselage (but still far longer as max trailer width)

 

[cluttonfred]

I do think that the ultrashort fuselage is workable if you accept that it's not going to be ideal from a drag standpoint. Taking a look at some of the resources in this thread -- https://www.homebuiltairplanes.com/forums/aircraft-design-aerodynamics-new-technology/12253-ergonomics-seatback-angles.html -- you can see that there is quite a bit of length to be saved with an upright seating angle and, as has been suggested, a staggered firewall that allows the rear of the engine to project over the feet of the occupant(s). Also, has autoreply has mentioned, you could also incorporate a removable or folding fairing--much easier to implement than a folding wing, for example, thanks to the absence of control connection complications.

 

[TFF]

How about this

 

[cheapracer]

There is nothing wrong with an asymmetrical fold line.

That comment is not appreciated by us Aspergers sufferers! :gig:

 

[Aircar]

Lots of recumbent velomobiles come in under 2 metres --easy to do if prone also . there are always assumptions inherent in flat statements of something can't be done -just got to find them before you can see the answer. And nice to see I am not the only 'keyboard dyslexic'- I think it comes from seeing the next plus one letter closer than the next and going to it to save time or something )

 

[cluttonfred]

To give another example, here is neat little plane that could serve as inspiration. The original Praga E.114 Air Baby with a two-cylinder Aeronca or Praga engine measured 21' 6" (6.56m) long. A quick guesstimate shows the length from the prop hub to the wing trailing edge of about 9' 9" (3.0m).

So, pulling the engine back on a staggered firewall should gain at least 12". Replacing the mixed straight and tapered wing with a constant-chord wing of the same area saves us about 10", so it pulls in the trailing edge about 7.5". Let's say that upright seating, a center instrument pod and no panel, fuel tanks in the wings, etc. gain us another 4.5". Now we're down to 7' 9" (2.39m) prop hub to wing trailing edge and we can fit through the container doors with an inch te spare on either side. There is still room in our 40' container, so we push the wingspan from 36' to 38.5' and now we've got about 3" clearance on each side of the doorway and about 6" at either end of the container. so wing and pod are good.

Even without going the plank flying wing route, we could go with the suggestion from Hot Wings for a side-folding rear fuselage. To make that even easier, we make the rear fuselage an open truss like a primary glider but of neatly faired, large-diameter tubes. The tail could be an inverted vee or a horizontal stabilzer with downward-projecting rudders like the Boeing YL-15 to tuck neatly under the wing, with the span an inch or two more than the pod since it will be angled. If the tail hinges to the right, then running the control cables from right to left down the tail means they will slacken when folded. Folding could be as simple a pulling a few captive pins and pushing the tail on the hinge. The dolly or trailer would have wheel chocks and a tail rest built in to keep everying in position when folded.

 

[Head in the clouds]

To give another example, here is neat little plane that could serve as inspiration. The original Praga E.114 Air Baby with a two-cylinder Aeronca or Praga engine measured 21' 6" (6.56m) long. A quick guesstimate shows the length from the prop hub to the wing trailing edge of about 9' 9" (3.0m).

So, pulling the engine back on a staggered firewall should gain at least 12". Replacing the mixed straight and tapered wing with a constant-chord wing of the same area saves us about 10", so it pulls in the trailing edge about 7.5". Let's say that upright seating, a center instrument pod and no panel, fuel tanks in the wings, etc. gain us another 4.5". Now we're down to 7' 9" (2.39m) prop hub to wing trailing edge and we can fit through the container doors with an inch te spare on either side. There is still room in our 40' container, so we push the wingspan from 36' to 38.5' and now we've got about 3" clearance on each side of the doorway and about 6" at either end of the container. so wing and pod are good.

Even without going the plank flying wing route, we could go with the suggestion from Hot Wings for a side-folding rear fuselage. To make that even easier, we make the rear fuselage an open truss like a primary glider but of neatly faired, large-diameter tubes. The tail could be an inverted vee or a horizontal stabilzer with downward-projecting rudders like the Boeing YL-15 to tuck neatly under the wing, with the span an inch or two more than the pod since it will be angled. If the tail hinges to the right, then running the control cables from right to left down the tail means they will slacken when folded. Folding could be as simple a pulling a few captive pins and pushing the tail on the hinge. The dolly or trailer would have wheel chocks and a tail rest built in to keep everying in position when folded.

View attachment 25622 View attachment 25623 View attachment 25624

The furthest aft you could have your fold hinge would be at the rear spar, then when it's folded you've not allowed for the width of the fuselage which would project aft of the rear spar position by approx 3ft (or whatever the width of the fuse is, at that point), so now you're back to being about two feet too long/wide. What you've described is pretty much (including the slackening cables) what I have almost completed the design of, as described in post #144, with the exception that you need an aft fuselage that collapses to no more than about 9" wide before you fold it sideways.

I don't think your inverted V tail would work though because if you consider it assembled/rigged ready to fly you wouldn't have the required tail clearance for the landing or take-off angle, and so would bang the tail on the ground. I think you'd more likely have to accept the folding or removal of one side of the HS.

 

[cluttonfred]

Not quite, I should have drawn a picture. I suggested that the rear fuselage should be a flat truss like a primary glider, so the cross-section of that need onlyl be a few inches, not a a few feet. The rear fuselage could be hinged to the pod, so above the wing in a low-wing configuration or below the wing in a high-wing configuration, so the hinge point could be forward of the rear spar. In fact, an advantage of the high or shoulder wing would be that the hinge point could be further forward--even with fairly upright seating, the occupants shoulders will be further aft than their rear ends. This would work easily in a single seater. In a two-seater, the transition from a side-by-side cockpit to a narrow rear fuselage could be eased by removable "cheek" fairings. Inside, the rear fuselage ***structure*** would narrow quickly to the same width as the single seater. I would use visible external hinges with little fairings on both sides--one side with safetied bolts as hinge pins and the other side with L-shaped steel pins--you could even work out a key lock with a safety pin backup. Simple, cheap and easy to inspect and repair. Here are a couple of poor sketches. Cheers, Matthew

 

[autoreply]

Why go through all the trouble, when you can have a monopiece high-wing, where you pull the two bolts, jack up the wing with a 5$ jack and rotate the wing 90 degrees? That's a hell of a lot simpler and lighter?

 

[plncraze]

Didn't the Lacey M-10 have this feature? According to Air Progress Sport Aircraft Annual 1973 Joe Lacey lived in Irving, Texas and plans were $8.00!

 

[cluttonfred]

Why go through all the trouble, when you can have a monopiece high-wing, where you pull the two bolts, jack up the wing with a 5$ jack and rotate the wing 90 degrees? That's a hell of a lot simpler and lighter?

My first reaction, not trying to be sarcastic...let's see, strange control runs, harder to design, harder to inspect, complicates primary load path from the main wing to the fuselage.

Something like what I described could be much simpler--it's basically a side-by-side version of a TEAM Airbike with trigear, a cockpit enclosure, a lower tail design and a couple of hinges and pinned joints added to the fuselage truss.

You could make it even simpler by using four removable pins and a little dolly--just wheel the rear fuselage over and park it under the wing--though I like the folding idea better.

 

[Norman]

Lots of recumbent velomobiles come in under 2 metres --easy to do if prone also .

Velomobiles typically have a 1/2 hp electric motor in the hub of the rear wheel and the rider's feet in the nose. Just try wedging a useful sized engine into one of those little fairings and leave room for a pilot

 

[Hot Wings]

Why go through all the trouble, when you can have a monopiece high-wing, where you pull the two bolts, jack up the wing with a 5$ jack and rotate the wing 90 degrees? That's a hell of a lot simpler and lighter?

You wouldn't even need the jack, just a spring to lift the wing in a center pivot. An over center latch could then pull the wing back into place manually.

My only objection to this method is that you still end up with a fairly long unit to trailer. My personal limit is about 20 ft (5.4m) Most older garages here in the US are only 24 feet - external dimension - which yields about 21 feet of useable internal length for storage. Allowing for a non-telescoping trailer tongue the means that 18 feet is the practical limit.

 

[autoreply]

Fold the outer panels. Orders of magnitude simpler (and lighter loaded) as folding two separate wings.

 

[Rienk]

You wouldn't even need the jack, just a spring to lift the wing in a center pivot. An over center latch could then pull the wing back into place manually.

My only objection to this method is that you still end up with a fairly long unit to trailer. My personal limit is about 20 ft (5.4m) Most older garages here in the US are only 24 feet - external dimension - which yields about 21 feet of useable internal length for storage. Allowing for a non-telescoping trailer tongue the means that 18 feet is the practical limit.

I think the solution that the Smiths came up with for their Swing Wing on their Backyard Flyer is ingenious.

But I agree that keeping it small enough for a old garage - or to fit in a 20' shipping container (important from a manufacturer's delivery perspective) is rather important. Of course, I'm envisioning going even smaller (4'x4'x8' crate) so removable AND foldable wings are necessary - as well as a foldable fuselage. Any 'useful' aircraft that can fit in the back of a pickup or an 8' trailer would be the ultimate IMO.