Flea style "Piojo Flying MiniBike"

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FritzW

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With all the resent T&G discussion... The side bends in a Piojo fuselage are very shallow, square (or round) tubes and gussets might be a super simple way to build one.

...if we could only find a tool to make drilling the tubes easier
 

Aerowerx

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With all the resent T&G discussion... The side bends in a Piojo fuselage are very shallow, square (or round) tubes and gussets might be a super simple way to build one.

...if we could only find a tool to make drilling the tubes easier
I seem to remember a thread here on HBA, some time ago. Some one had an idea how to easily drill aligned holes in tubes and gussets. You might want to search for it, Fritz.;)
 

Victor Bravo

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Wow... now that idea is getting a little traction in my mind. Fritz, perhaps take another look at the wing construction of the Kolb ultralights. The wing spars are large diameter AL tubes, strut braced... but there may be enough strength in those tube spars for a short span cantilever wing like the Piojo. Forward wing is supported by struts that meet the wing at .40 semi-span (like the Flea glider version here), and rear wing is short enough span that the unsupported portion looks the same as the unsupported portion of the Kolb outboard of the strut. The forward struts meet the wing at one location, allowing the wing to pivot on a simple ball joint.

Pou du Ciel Glider.jpg
 
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plncraze

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For drilling holes more easily has about a heavy duty hose clamp with a tube attached to align the drill?
 

cluttonfred

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The forward struts meet the wing at one location, allowing the wing to pivot on a simple ball joint.View attachment 90738
Why a ball joint? The wing pivots in one axis only, so simple hinge pins should do just fine both for the strut attachments and the pushrod(s) for pitch control. Those cantilever struts are cute but an inverted V-strut on each side and two pairs of wires (one down to the lower fuselage, the other across to the base of the opposite strut) would be lighter and easier on the wing spar.
 

FritzW

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Rod end bearings might be the simplest, especially if the goal is to make make it 'bolt together" as much as possible. It'd need high swivel angle bearings like these. ...but you have to wonder about rod end bearing that only cost $10 (mil spec bearings are a couple of hundred bucks each).

I'm drawing up a square tube T&G fuselage but I'm thinking regular "tin box" construction would have 1/2 the parts count and half the cost.
 

Victor Bravo

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The idea behind the ball joint bearings is that the threaded stud can be screwed into the end of the strut parallel to the major axis, and still allow the wing to rotate around the (spanwise) pivot axis. The ball joints have more bearing area than the bearing area of a 1/4" or 5/16" bolt shank on the edge of a hole in a .063" steel tab.
 

Victor Bravo

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The "tin box" could be very easy here, because the fuselage does not need any taper. A constant thickness slab. One simple 9" wide bent sheet aluminum C-channel can be used as a standard material for the top, bottom, and most of the bulkheads of the fuselage. So you'd bend up 12 foot lengths of this shallow C-channel, and cut bulkheads or upper/lower fuselage keels out of it... and then rivet the fuselage sides to these channels. Even better, you can lay out the channels with 3/4" hole spacing, and cut the fuselage sides with the same 3/4 spacing. So cut the C-channels to length, and cleco the sides to the channels, and start pulling rivets. The rudder needs to be 9 inches wide at the spar, which is of course more than it needs, but accepting this means you don't need any taper anywhere in the fuselage plan view. Only the firewall, landing gear mount plate, and engine mounting plate channel material needs to be made from .050 (the rest of the channel being .025). The fuselage side skins can be .016 or .020.
 

FritzW

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I'm digging the C channel idea but I don't think I could live with the fuselage being 9" wide at the tail. You could cut a wedge shaped notch in the middle of the top and bottom C channel, ~48 long and 5 wide at the aft edge, pull the sides in and rivet a doubler strip over the slice.

Even better, you can lay out the channels with 3/4" hole spacing, and cut the fuselage sides with the same 3/4 spacing. So cut the C-channels to length, and cleco the sides to the channels, and start pulling rivets.
You could probably get away with "drilling before you bend" on the C channel (perfect for CNCphiles) but the bends are still going to have to be pretty accurate.

How do you propose to bend a 12' C channel? Air conditioning duct company?

I inherited an 8' brake but it's too flaky for a bend this long (something is too bendy on it but I haven't messed with it enough to know what it is)
 

Victor Bravo

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The 9 inch wide rudder is a small price to pay IMHO. I would like to ask for any aero guy on HBA to compare the 70 MPH drag of a Zenair 701 style small single seat aircraft rudder at 4 inches thick to an identical one at 9 inches (I just went in the garage and measured a plans-built CH-701 rudder at 4 1/8 inches).

I'll bet the difference is a pound or two of drag at those speeds.

However, yes of course you can substitute two modified channels, or make specific tapered channels for the rear fuselage.

My idea was absolutely to have the skins drilled first then bent. The idea is based on CNC router or laser cutting the parts, so you get identical rivet spacing between the fuselage sides and the channel flanges.

Yes on the air conditioning shop to do the bends. I believe bending 48 or 64 feet of this channel, enough to do 2 fuselages, could be a hundred bucks and a six-pack for the shop owner to do after hours or between ther jobs.

The end result is that if the bends in the fuselage channels are within a small tolerance, the fuselage tops and bottoms will be within half a degree of square to the sides, and the bulkheads will be within half a degree of perpendicular to the long axis of the fuselage. That's plenty good for this use, and will save 40 hours of sheet metal layout and drilling.
 
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Topaz

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If you have the rear ailerons then why tilt the fore wing?
Rear-wing elevons won't work on a tandem wing aircraft. Or, more properly, the resulting aircraft is either very inefficient, or has really nasty stall characteristics of the wing-shedding variety.

Commanding "nose up" with a rear-wing elevon reduces that wing's lifting capability, since you're applying "up" flap, essentially. You never, ever, want the rear wing to stall first on a tandem-wing aircraft. It results in flipping the airplane over on its back, likely shedding flying surfaces in the process. That's a bad day.

Pitch control really has to be on the forward wing. It can either be elevators (Quickie, Q2/Q200, Dragonfly), or an all-moving wing (Pou du Ciel).
 
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Sockmonkey

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Rear-wing elevons won't work on a tandem wing aircraft. Or, more properly, the resulting aircraft is either very inefficient, or has really nasty stall characteristics of the wing-shedding variety.

Commanding "nose up" with a rear-wing elevon reduces that wing's lifting capability, since you're applying "up" flap, essentially. You never, ever, want the rear wing to stall first on a tandem-wing aircraft. It results in flipping the airplane over on its back, likely shedding flying surfaces in the process. That's a bad day.
Doesn't the higher AOA and area loading of the fore wing on a tandem ensure that it always stalls first even with rear flaps?
 

Topaz

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Doesn't the higher AOA and area loading of the fore wing on a tandem ensure that it always stalls first even with rear flaps?
It can be made to be that way, but then it means that the rear wing is always flying so far away from its maximum CL that you end up with a lot more wing area (and weight, and material, and cost) there than you'd have otherwise. The ideal situation has the main wing, under the worst-case situation, reaching just below its maximum CL capability when the canard lets go and stalls. That results in the smallest, lightest, cheapest design possible for the particular configuration. That's hard to do when part of the rear wing has flaps "up" and the rest has flaps "zero".

It's just far easier to resolve the stalling issues and keep the airplane as small and light as possible if the front wing contains the pitch control and the rear wing has roll controls only, if anything at all. All the Rutan designs, all the tandem wing designs, have done it this way.
 
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