Raptor Composite Aircraft

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wsimpso1

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While some of the pushrods are way too small, they're short and none of the ones in the cockpit or wing are buckling, elastically or otherwise.
So some of the belcranks in the plane (for the door locking, and some of the controls) are too small, leading to any play in the rod-ends or bearings being magnified in the total play from stick to control surface. Some also have some to much flexibility in their mounting, adding to play. Pushrods aren't the issue.

The single shear nature of many of the mounting points, or the flexibility of the underlying substrate, is a large majority of the issue with compliance in the roll control system. PItch has its own issues, but yaw actually works pretty nicely.
Good to hear that the pushrods are OK. I keep thinking of Marc's observations on Long-EZ back seat elevator control and how easily Peter seemed to get the second half of his stick deflection on his gauged pull.

Also good to hear that the underlying sources of the flexibility have been identified. Single shear connections mean torsional deflection of the associated pieces. Lots of room for improvement in those elements by simple redesign where they are significant contributors. I hope that he starts with the largest contributors and works his way toward smaller ones.

Billski
 

donjohnston

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Some opinions are worth more than others :).

The Velocity used to use push/pull cables for part of the aileron control system - they moved away from them as their XL's got larger and faster. I don't believe that there has ever been aileron flutter on a Velocity (or any canard aircraft of which I'm aware), but clearly Velocity eventually decided on a more robust system.
Velocity still uses cables for the aileron. The push/pull tube system is an option for the center stick configuration. I believe it's standard for the side stick configuration since I haven't seen a side stick build without the push/pull tubes.

I've thought about converting mine to push/pull tubes but cables have been around Velocity since the beginning and it works fine. Maybe a little stiffer action that push/pull tubes, but it flies fine for me.
 

cheapracer

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New video posted. Looks like Peter is going back to cable and pulley system.
Yup, a number of items he says and does makes me think he reads here, or at least Boku's posts there ..

Umm, the carbon fiber is kind of thick isn't it, maybe tanks for the military may have been a better way to go ....
 

berridos

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He doesnt seem to be aware of monocoque structures, with such a panzer keel. Looks like he has implemented the structure of a car. Specially absurd in the case of a pressurised fuselage.
 

BoKu

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I've added my usual two cents:

The decision to go back to the pulleys was a good one, but there are a lot better ways to anchor them than with a 1/2" (13mm) pivot axle. The stiffness of a rod or tube scales with the square of its diameter, and the strength scales with the cube, so a relatively small increase in diameter gives you a large increase in stiffness and a huge increase in strength. The upshot is that a 3/4" tube with 1/16" (1.5mm) wall thickness weighs less than a 1/2" steel rod, but has three times the bending stiffness. And if you go out to like a 1" diameter tube with 0.049" (1.25mm) wall, you get five times the stiffness and it's still lighter than the 1/2" rod.

As I suggested several videos ago, the best way to skin this cat is probably with a steel weldment that bridges between the sides of the keel and supports the two pulleys. The bridge would be based on a 1" steel tube with 0.049" wall. At each end of the tube would be a plate that anchors to the sides of the keel with two to four AN bolts and nuts. Spaced along the tube would be two pairs of steel leaves that support the two pulleys. The plate and leaves would be 0.050" thick, and all steel would be common 4130N. The end plates might be braked into angles so they anchor to the aft bulkhead instead of to the keel. This sketch shows two possible schemes for the pulley bridge:

https://hpaircraftblog.files.wordpress.com/2020/01/raptor-aft-pulley-bridge.jpg

The anchors at the sides of the keel or at the aft bulkhead could be reinforced with plates or wedges of G10 Garolite. What we often do in situations like this is drill and tap the Garolite reinforcements 10-32 or 1/4-28, and temporarily attach them to the weldment with short machine screws. Then we'll bond the reinforcements into the airframe as dictated by the geometry of the weldment. When the bonding paste cures, we remove the machine screws and the weldment, drill clearance holes through the threads, and apply one or two plies of fiberglass over the Garolite to encapsulate it and distribute load into the airframe. Then we put the weldment back in and secure it with the final AN hardware.

The 0.05" thickness for the tubing and leaves makes it amenable to tack welding with a common 120v MIG box. So it's pretty easy to hack something together in the field, then take it to a professional welder to be TIG'd together with full circumference welds that submerge the tacks. Then you can send it out for powder coating and it comes back looking really professional. That's not the absolute best way to do a thing like that, but it is certainly good enough for most aeronautic applications.
 

pictsidhe

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The rear pulleys look like they will probably be pretty close to the sides, so the 1/2" will probably be ok. But the ones in the tunnel look like they'll be a long way from the sides, and that 1/2" may be too springy.
 

cheapracer

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I've added my usual two cents:

The stiffness of a rod or tube scales with the square of its diameter,
He'll read and think to himself: "Why would I use square tube"?

He could turn the new pulleys he mentioned up in a few hours, shirley there's a local shop to him.
 

BoKu

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He doesnt seem to be aware of monocoque structures, with such a panzer keel. Looks like he has implemented the structure of a car. Specially absurd in the case of a pressurised fuselage.
The section shown at time code 0:40 appears massive. If that's solid carbon and not a sandwich, well, now we know where some of the half-ton of extra mass comes from. I can't imagine what they were thinking making it that thick.
 

TarDevil

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The section shown at time code 0:40 appears massive. If that's solid carbon and not a sandwich, well, now we know where some of the half-ton of extra mass comes from. I can't imagine what they were thinking making it that thick.
IIRC, the halves didn't mate well and they backfilled with CF.
 

BoKu

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Why can't he do a push rod system? He cut a hole in the thing (thick in that area) so it looks like he could thread some rods in there to do a push rod system and be done with it.
That hole would give him access to install a bellcrank that runs the drive around the corner from the keel up the aft bulkhead. But he'd have to thread the tube in from the nosewheel bay, and unless it's a very large tube he'd have to install a mid-keel support or guide. I suspect that the constriction that forced the use of cables instead of push-pull tubes is at the wing root rib or at the outboard end of the strake, so he might have to retain the cables in the strakes. But push-pull tubes to a drive wheel at the upper aft bulkhead, and a cable loop between the outboard ends of the strakes, might indeed be a good compromise that yields a flightworthy roll control system.
 

pictsidhe

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He'll read and think to himself: "Why would I use square tube"?

He could turn the new pulleys he mentioned up in a few hours, shirley there's a local shop to him.
ah, but then they'd be non standard. Any fool also knows, aluminium pulleys would be heavier than gr4 or whatever it is 'proper' pulleys are made from.
 

cheapracer

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ah, but then they'd be non standard. Any fool also knows, aluminium pulleys would be heavier than gr4 or whatever it is 'proper' pulleys are made from.
My first choice in this situation would be hardwood actually.


So new chapters start on the right hand side of the open book, or because information was edited on a couple pages but overall page numbering is to be retained, or they’re in there as note paper.
PDFs ....
 

cheapracer

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Hmmm, plywood with rivets near the rim to prevent splitting?
Well I would do that for a test run, cents in the dollar to find out if it works or not.

This is an example of his poor management, going to wait a week for new parts to arrive, and he doesn't even know if they will cure the issue. If they don't work, he's lost a week, money and momentum.


Magnesium for lightweight and improved control authority during cabin fires.
Err, how exactly does magnesium improve anything during a fire, ever seen mag burn?
 
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