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Ez2cDave

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Great hinge material, but unfortunately I found out the hard way that it can't stand up to the heat of motor exhaust (it's basically plastic with a super thin layer of aluminum on its surface).

I'm going to try self-adhesive aluminum tape today. Sticky stuff that's hard to handle, especially on irregular surfaces. But what the heck, the result might not look perfect, but I know it works.
Eric,

Agreed . . . 100% . . . Mylar tape is only "plastic" and would melt.

IDEA : Tape application . . . In difficult areas, apply it in small sections, rather than "wrestling" with a larger piece that wants to grab and "stick in all the wrong places" !

Dave F.
 
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BABAR

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Putting yourself on fire seems a little drastic, I'm no doctor, but maybe there are other, more conventional remedies.
I’m glad your a Smart Aleck and not a DA!
Fixed it.
Darned voice rec!
 

Rktman

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Putting yourself on fire seems a little drastic, I'm no doctor, but maybe there are other, more conventional remedies.
Self-immolation, especially of one's family jewels, seems to be a rather dire cure for anything. o_O Inadvisable under any circumstances IMHO.
 

Rktman

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Applied the aluminum tape and though the little imperfections irritate the perfectionist in me, no one but me will care, and certainly no one on the flight line. It's functional so I'm satisfied.

IMG_5471.JPG
 

BABAR

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Applied the aluminum tape and though the little imperfections irritate the perfectionist in me, no one but me will care, and certainly no one on the flight line. It's functional so I'm satisfied.

View attachment 441075
Looks cool to me. Be interesting to see the soot marks on this, my guess is you are covering more than you need to, BUT that IS the recommended way to START.
 

burkefj

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I'm thinking they weren't drooped enough to either act as dihedral or vertical stabilizers

Thanks for the info . . .

I was thinking back to when the REAL XB-70 Valkyrie crash happened . . . The F-104 stuck the Right Wing and got caught in the Tip Vortex from the Drooped Wingtips and was flipped across the top of the Valkyrie, shearing off both Vertical Rudders in the process.

I wonder why the "dihedral effect" of the Delta wing did not permit an emergency landing, especially since the Wingtips were "drooped" at the time ?



Dave F.
 

BABAR

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I'm thinking they weren't drooped enough to either act as dihedral or vertical stabilizers
If they were “drooped” instead of “perky” (down instead of up) wouldn’t they be REVERSE dihedral and therefore DEstabilizing?
 

burkefj

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I'm not sure, they would certainly have helped with lateral stability I would think.

If they were “drooped” instead of “perky” (down instead of up) wouldn’t they be REVERSE dihedral and therefore DEstabilizing?
 

Ez2cDave

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If they were “drooped” instead of “perky” (down instead of up) wouldn’t they be REVERSE dihedral and therefore DEstabilizing?
Take a look at the images and note the Rudder positions.

Note that the Valkyrie's wingtips were not fully drooped, at the time of the crash.

Dave F.

ESTES NIGHTHAWK - 1.JPG




MINI-CONDOR - 1.jpg





NIM_Plan.jpg





xb70_3view-2.jpg
 

GlenP

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With a delta wing, most of the vortex lift is concentrated along the leading edge, so the wing platform can be as simple as this, for example:


that open platform design concept may also help avoid burn through, because well, what is there to burn?

But I really like the built up frame wing and tissue covered look of your cranked delta wing.
 
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Ez2cDave

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Hmm . . . Tissue or Monokote that open section and add a "micro-brick" RC unit ?

Dave F.

1607282473796.png
 

Aeronerd

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Flying wing designs like the nighthawk and n1m use the those downtiped wingtips for rudder control and for washout. Not dihedral. Swept wings and deltas don't need dihedral.
 

Ez2cDave

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Flying wing designs like the nighthawk and n1m use the those downtiped wingtips for rudder control and for washout. Not dihedral. Swept wings and deltas don't need dihedral.
Correct . . . My hypothesis for saving the XB-70 was to droop both wingtips to the maximum to try to create some "Rudder Effect" stabilization, after both vertical Fins were sheared off by the F-104 Starfighter.

Additionally, I would have used the Flaps and Main Landing Gear to create "Base Drag" to try to stabilize it like a "Dart". Those 6 jet engines, capable of Mach 3+, would have had no problem maintaining velocity above Stall Speed.

Given that, a controlled Emergency Landing might have been possible or, at least prevented the Flat Spin that would have made Ejection much safer ( The Pilot was severely injured and Co-Pilot was killed because Centrifugal Force prevented him from ejecting in his "Pod" ).

Dave F.
 

BABAR

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Flying wing designs like the nighthawk and n1m use the those downtiped wingtips for rudder control and for washout. Not dihedral. Swept wings and deltas don't need dihedral.
I am curious with delta wings with no dihedral how the glider determines which side is “up”? Of course, I have the same problem understanding the RingHawk. Sometimes ignorance is bliss.
 

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I am curious with delta wings with no dihedral how the glider determines which side is “up”? Of course, I have the same problem understanding the RingHawk. Sometimes ignorance is bliss.
Wish I had the answer to that myself. That's one of the reasons I put some dihedral in the canard wing, as a "just in case".
 

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How do delta wing gliders know which side is "up" without dihedral?
Any knowledgeable TRF-ers out there know the answer?
 

BABAR

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How do delta wing gliders know which side is "up" without dihedral?
Any knowledgeable TRF-ers out there know the answer?
Interestingly enough, I have had some helicopters come in rotating just fine, but upside down. I have also seen this with the helicopter nose cone of the Estes Cosmic Cobra and variants, coming down rotors down and nose cone up. (Incidentally, if anyone considers getting one of these, don’t get the Cosmic Cobra or the SkyTwister, get the HeliCat. They are ALMOST all three the same rocket, except the HeliCat has a longer body tube which actually ALLOWS for easy and reliable packing of the wadding, chute, and the nose cone rotor blades. The other two are far to short and tough to pack, in my experience at least with the Cobra resulting in failed deployment and lawn darts.)
 

Rktman

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Interestingly enough, I have had some helicopters come in rotating just fine, but upside down. I have also seen this with the helicopter nose cone of the Estes Cosmic Cobra and variants, coming down rotors down and nose cone up. (Incidentally, if anyone considers getting one of these, don’t get the Cosmic Cobra or the SkyTwister, get the HeliCat. They are ALMOST all three the same rocket, except the HeliCat has a longer body tube which actually ALLOWS for easy and reliable packing of the wadding, chute, and the nose cone rotor blades. The other two are far to short and tough to pack, in my experience at least with the Cobra resulting in failed deployment and lawn darts.)
With helicopters coming down inverted, it's either insufficient rotor dihedral, a too nose-heavy rocket, and/or a too long motor delay charge such that the rocket is past apogee and already headed nose down when the rotors deploy. I suppose it could be a combination of those things as well.
 

BABAR

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With helicopters coming down inverted, it's either insufficient rotor dihedral, a too nose-heavy rocket, and/or a too long motor delay charge such that the rocket is past apogee and already headed nose down when the rotors deploy. I suppose it could be a combination of those things as well.
Probably the Combo. Sometimes I set the dihedral for zero because I EXPECT the mass of the body tube and motor to “force” the system nose-up/motor down, with the “flex” of the rotors creating and effect dihedral. MOST of the time it works as planned. But it sure looks freaky when it comes down inverted, and what is really weird is that apparently I speak with an Aussie accent for the next 1/2 hour every time.
 

Rktman

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Probably the Combo. Sometimes I set the dihedral for zero because I EXPECT the mass of the body tube and motor to “force” the system nose-up/motor down, with the “flex” of the rotors creating and effect dihedral. MOST of the time it works as planned. But it sure looks freaky when it comes down inverted, and what is really weird is that apparently I speak with an Aussie accent for the next 1/2 hour every time.
Now I have GOT to go back and listen to the narration on your flight videos!
 

BABAR

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You poor sod!
 

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How do delta wing gliders know which side is "up" without dihedral?
Any knowledgeable TRF-ers out there know the answer?
Balance and trim, and possibly a dorsal rudder. They should be balanced and trimmed for upright flight. When inverted they would not be trimmed and balanced and would stall or dive. A dorsal rudder helps it go straight and the drag on top helps keep that on top, but mostly the balance and trim for glide keeps the glider right side up. Not much different than why a stable rocket flies nose first instead of tail first.
 

Ez2cDave

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How do delta wing gliders know which side is "up" without dihedral?
Any knowledgeable TRF-ers out there know the answer?
Eric,

I am going to "hazard a guess" . . .

I suspect that the "Pendulum Effect" comes into play . . .

With that said, if we built 2 identical, Zero-Dihedral, Delta Wing gliders ( without Canard ) and only one thing varies :

( 1 ) One is a "High-Wing / Shoulder-Wing" arrangement.

( 2 ) One is a "Low-Wing / Fuselage On Top" arrangement.

THEORY - Each Glider would tend, due to the "Pendulum Effect", to stabilize with the Fuselage "on the bottom". This would be due to the Mass of the Fuselage creating the "Pendulum Effect".

1607480850995.png

The reason I eliminated the Canard is that it has an "Angle of Attack", relative to the Wing, and, often, Dihedral.

The CMR "MANTA" glider has no Canard, "Under-slung Rudders", and Wing Tip Dihedral.

Kuhn_Manta.jpg


Dave F.
 

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burkefj

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I'll quote Bob Parks since we were just having this discussion in emails recently
"There is no such thing as pendulum effect on a flying airplane. If you
think about the forces on a real pendulum, the pivot is fixed, and the
pendulum is hanging from it. The force applied by the pivot to the
pendulum is ALWAYS purely vertical. When the pendulum is off to the
side, the gravity force vector applied to the weight has a vector
component that is along the strut of the pendulum, but also a component
that is a rotational moment about the pivot... thus it swings back to
vertical (and oscillates).

In an airplane as it rotates in pitch or roll, the lift force vector
does not change its angle relative to the airplane, so there is no
"gravity" component to give a rotational moment. In an airplane it is
VERY difficult to know where the gravity vector even points to. I have
done a bit of aerobatics in full size planes. If you do a pretty tight
loop, you go over the top still pressed into your seat and you are
looking "up" at the ground. Same thing in a tight, coordinated turn.
you feel like you are upright when you are in a 45 deg bank. That is
why flying IFR is so hard to learn.

There are some dynamics effects of having the CG well below the wing,
but the low wing vs high wing difference in dihedral effect is mostly
the difference in wing to body aero interference.

What you care about is often called "dihedral effect", or in engineering terms, "rolling moment vs sideslip angle". Basically, if the left wing drops, the tilted lift pulls the plane to the left, which results in a sideslip. Dihedral effect causes a rolling moment to roll the plane back to level. Similarly, if you gave right rudder, that gives the same kind of sideslip (relative wind hitting the left side of the nose), and would roll the plane to the right, into the turn. All the examples below assume the same relative wind hitting more on the left side of the nose.

There are 4 big things that contribute to it:

1) actual geometric dihedral. The dihedral angle means that with the side slip, the left wing is at a slightly higher angle of attack than the right, and makes more lift causing the roll.

2) wing location on the body. This is really an interference effect. With a low wing, and the body at an angle to the flow, the leeward wing is somewhat masked by the body, cutting its lift. This one depends a LOT on configuration. A long chord delta wing is a lot different from a sailplane.

3) sweep. With the sideslip angle, the left wing gets less sweep relative to the flow, has more exposed span than the right wing, so left wing makes more lift. This effect tends to vary with angle of attack. Higher angle of attack, more dihedral effect due to sweep. Very rough rule of thumb.. 10 degrees of sweep is about the same as 1 degree of dihedral

4) a really tall vertical tail, particularly if it is a T tail. With the sideslip, the tail makes a side force trying to yaw the plane to the left, and with a tall tail, that side force also makes a right roll moment.

These things all add up. What matters is the total dihedral effect.

You want to get the right balance of dihedral effect and yaw "weathervane" stability. Too much dihedral and not enough yaw stability, results in a combined yaw and roll oscillation called a "Dutch roll". It can be unpleasant if you are in the plane.. or even flying FPV. I have a Twisted hobbies ProXy FPV airplane and it has a V tail and high wing so is prone to Dutch roll. It can be a bit nausea inducing.

Similarly, airliners with sweep and dihedral and the desire to not have a lot of weight and drag in a big vertical tail makes them prone to Dutch Roll. They use active gyro dampers to handle it. I was once on an airliner, sitting up near the front, where the yaw damper failed.. not pleasant.

In the other direction, low dihedral effect, plus being yaw stable gives spiral divergence. If you leave the plane on its own, it will eventually end up in an ever worsening spiral dive. But this can take many minutes to happen. A human pilot, either onboard or RC takes care of it without even realizing what is going on. Most manned airplanes accept spiral divergence to avoid Dutch Roll. "

Bottom line, high delta wing, no wing to body interference, dihedral not needed as effective dihedral due to the delta wing is sufficient. Low delta wing, dihedral is beneficial due to body/wing interference reducing effective dihedral.






Frank
 
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BABAR

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Okay, read posts 83-85.

Still not sure how a delta glider with no dihedral figures out which way is up.

Teleologically I agree that gliders with no dihedral work when rudders are up (because all the ones I have seen HAVE upward rudders, the only downward rudders I remember seeing were in gliders WITH dihedral), but teleologically only means I have seen deltas with no dihedral and upward rudders work, but I don’t know WHY they work.

Then again, there are lots of things I don’t know.

There’s a great story of a USAF EC-130 flying off the China coast “monitoring” electronic emissions.

It got jumped by two Migs.

The only thing the C130 can do as well as a MiG is drop out of the sky like a brick.

Short version is the 130 leveled off about 50 feet above the water, the Migs 200 feet below it.

The 130 continued to monitor Chinese transmissions until they got out range. On the Chinese Military ATC channel rough translation as follows:

ATC: “Red 1, Red 2, come in.”

Static..........

ATC: “Red 1, Red 2, come in.”

More static........


Back at base the 130 apparently had about 5 more degrees dihedral in the wings than it took off with, they later painted two red stars on the nose.
 
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Rktman

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I'll quote Bob Parks since we were just having this discussion in emails recently
"There is no such thing as pendulum effect on a flying airplane. If you
think about the forces on a real pendulum, the pivot is fixed, and the
pendulum is hanging from it. The force applied by the pivot to the
pendulum is ALWAYS purely vertical. When the pendulum is off to the
side, the gravity force vector applied to the weight has a vector
component that is along the strut of the pendulum, but also a component
that is a rotational moment about the pivot... thus it swings back to
vertical (and oscillates).

In an airplane as it rotates in pitch or roll, the lift force vector
does not change its angle relative to the airplane, so there is no
"gravity" component to give a rotational moment. In an airplane it is
VERY difficult to know where the gravity vector even points to. I have
done a bit of aerobatics in full size planes. If you do a pretty tight
loop, you go over the top still pressed into your seat and you are
looking "up" at the ground. Same thing in a tight, coordinated turn.
you feel like you are upright when you are in a 45 deg bank. That is
why flying IFR is so hard to learn.

There are some dynamics effects of having the CG well below the wing,
but the low wing vs high wing difference in dihedral effect is mostly
the difference in wing to body aero interference.

What you care about is often called "dihedral effect", or in engineering terms, "rolling moment vs sideslip angle". Basically, if the left wing drops, the tilted lift pulls the plane to the left, which results in a sideslip. Dihedral effect causes a rolling moment to roll the plane back to level. Similarly, if you gave right rudder, that gives the same kind of sideslip (relative wind hitting the left side of the nose), and would roll the plane to the right, into the turn. All the examples below assume the same relative wind hitting more on the left side of the nose.

There are 4 big things that contribute to it:

1) actual geometric dihedral. The dihedral angle means that with the side slip, the left wing is at a slightly higher angle of attack than the right, and makes more lift causing the roll.

2) wing location on the body. This is really an interference effect. With a low wing, and the body at an angle to the flow, the leeward wing is somewhat masked by the body, cutting its lift. This one depends a LOT on configuration. A long chord delta wing is a lot different from a sailplane.

3) sweep. With the sideslip angle, the left wing gets less sweep relative to the flow, has more exposed span than the right wing, so left wing makes more lift. This effect tends to vary with angle of attack. Higher angle of attack, more dihedral effect due to sweep. Very rough rule of thumb.. 10 degrees of sweep is about the same as 1 degree of dihedral

4) a really tall vertical tail, particularly if it is a T tail. With the sideslip, the tail makes a side force trying to yaw the plane to the left, and with a tall tail, that side force also makes a right roll moment.

These things all add up. What matters is the total dihedral effect.

You want to get the right balance of dihedral effect and yaw "weathervane" stability. Too much dihedral and not enough yaw stability, results in a combined yaw and roll oscillation called a "Dutch roll". It can be unpleasant if you are in the plane.. or even flying FPV. I have a Twisted hobbies ProXy FPV airplane and it has a V tail and high wing so is prone to Dutch roll. It can be a bit nausea inducing.

Similarly, airliners with sweep and dihedral and the desire to not have a lot of weight and drag in a big vertical tail makes them prone to Dutch Roll. They use active gyro dampers to handle it. I was once on an airliner, sitting up near the front, where the yaw damper failed.. not pleasant.

In the other direction, low dihedral effect, plus being yaw stable gives spiral divergence. If you leave the plane on its own, it will eventually end up in an ever worsening spiral dive. But this can take many minutes to happen. A human pilot, either onboard or RC takes care of it without even realizing what is going on. Most manned airplanes accept spiral divergence to avoid Dutch Roll. "

Bottom line, high delta wing, no wing to body interference, dihedral not needed as effective dihedral due to the delta wing is sufficient. Low delta wing, dihedral is beneficial due to body/wing interference reducing effective dihedral.



Frank
Frank I'm particularly interested in your explanation because I've noticed a lot of your gliders use wing sweep (delta or swept wing planforms) and NO geometric (physical) dihedral (i.e. the wings are flat). So I just want to make sure I thoroughly understand what you described regarding how a delta wing glider "knows" which side is "up" WITHOUT (physical) dihedral by doing a Reader's Digest summary as I believe I understand it (and feel free to jump in if I get anything wrong):

> Wing location - generally speaking, *fuselage interference in low-wing gliders, i.e. body somewhat blocks airflow to DOWNWIND wing, reducing its lift, causing it to compensate/correct in the opposite direction of any sideslip/roll.

> Effect of primarily the height (and I assume width?) of the vertical stab, which creates a roll opposite to the sideslip due to airflow striking it on the windward (sideslip) side.

> Effect of wing sweep angle: on windward side, less sweep angle relative to airflow and more exposed span, which creates more lift (amount dependent on angle of attack). Approx. 10° sweep = 1° dihedral effect.

*I assume this has a greater influence on gliders that use a body tube as a fuselage, less so on smaller gliders that use a thin fuselage "stick".
 

Aeronerd

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I grew up with those Guillows type hand toss gliders and guys used to always talk about the pendulum effect. Wow so it was just more like a urban myth thing?
 

GlenP

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Still not sure how a delta glider with no dihedral figures out which way is up.
balance and trim.

There is usually a horizontal stabilizer or elevator at a fixed angle for trimmed glide in a nose-up attitude. If you toss it upside down it will dive and loop until it finds the proper upright balanced and trimmed condition on the other side of the loop, if there is enough altitude before it hits the ground.
 

Ez2cDave

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balance and trim.

There is usually a horizontal stabilizer or elevator at a fixed angle for trimmed glide in a nose-up attitude. If you toss it upside down it will dive and loop until it finds the proper upright balanced and trimmed condition on the other side of the loop, if there is enough altitude before it hits the ground.
So, basically, the Angle of Attack, influenced by the Angle of Incidence of a Horizontal Stabilizer ( conventional "Stab" or a Canard ), determines what the Glider "sees", as being "upright".

What happens on a Delta planform, zero-dihedral, "flying wing" ( without any Horizontal Stabilizer) and symmetrical, vertical Rudder(s) that are above and below the Wing ? ( Think a fuselage-less Delta-Katt, without a Canard )

I am assuming that some type of "Elevator Flap" would be necessary . . .

Dave F.

1607564706700.png


1607564766694.png
 

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