Quantcast

AeroDagger Cranked Arrow Build

The Rocketry Forum

Help Support The Rocketry Forum:

BABAR

Builds Rockets for NASA
TRF Lifetime Supporter
TRF Supporter
Joined
Aug 27, 2011
Messages
6,773
Reaction score
1,905
For future ideas, wondering if, in situations where you need extra tail weight with or without additional rudder surface area, replacing vertical rudders with larger rudders tilted vertically laterally may help.

The larger rudders will increase your tail weight as needed, the tilt gives you an bit of effective diehedral and maybe a bit of lift even when glide is level.
 

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
Eric,

Since you added a "flap", it might cause a tendency to loop during Boost.

The cure for that would be slightly more Downthrust Angle on the Pop-Pod.

If more "dihedral effect" is needed, you could "droop" the Wing Tips, like the XB-70 Valkyrie ( Actually - "Anhedral" ).

Dave F.

1a.jpg

1c.jpg

1b.jpg


1d.jpg


xb70_3view-2.jpg
xb70_3view-3.jpg
061122-F-1234P-020.JPG
061122-F-1234P-034.JPG
 

Attachments

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
For future ideas, wondering if, in situations where you need extra tail weight with or without additional rudder surface area, replacing vertical rudders with larger rudders tilted vertically laterally may help.

The larger rudders will increase your tail weight as needed, the tilt gives you an bit of effective diehedral and maybe a bit of lift even when glide is level.
I prefer vertical rudders, as I've tried the "tilted rudders" (aka V-tail) and they needed to be larger than a vertical rudder to provide the same amount of yaw control. That being said, if a design could benefit from more aft weight, I believe a larger V-tail would add dihedral. For example, the Holverson Swinger's wings have zero dihedral; the only dihedral is provided by the large V-tail, and it glides fine.

IMG_2506.JPG

Rick Needham's Swinger flight:
 
Last edited:

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Eric,

Since you added a "flap", it might cause a tendency to loop during Boost.

The cure for that would be slightly more Downthrust Angle on the Pop-Pod.

Dave F.
How much pod downthrust would be required to compensate, an amount equal to the flap angle? If the flap's angle is 1.5°, would a pod angle of -1° be enough? Or would that be too much? I built in a -1° angle in my pylon but if it's insufficient I could always remove and resand the pylon in a spare moment to salvage this "trial run" version.
 

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
I usually use 1 - 2 degrees of Downthrust, but I am NOT flying gliders with an "Elevator Flap", either ( just normal Decalage of the Stabilizer ) . . . The effect of the Flap will INCREASE with Airspeed. Sorry, I can't give you a definitive answer on this.

Canard gliders tend to Boost straighter than conventional B/G's . . .

Dave F.
 

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
For example, the Holverson Swinger's wings have zero dihedral; the only dihedral is provided by the large V-tail, and it glides fine.
The Swinger in that video "glides like a brick" . . .

The "Glide Circle" was way too tight and Glide Speed was quite high ( I suspect a Forward CG location ) . . . The result was more of a "Spiral" than a flat glide.

When you see a real "free-flight" Competition B/G or R/G in flight, you will instantly see the difference !

The video's below show a "high-performance glide" by comparison . . . Yes, the mass would be higher for a rocket-powered glider, but the comparison is valid.

Remember that these flights are INDOORS with ZERO thermal activity ! ( The last video is a world record flight of nearly 2 minutes ! )




Dave F.
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
The Swinger in that video "glides like a brick" . . .

The "Glide Circle" was way too tight and Glide Speed was quite high ( I suspect a Forward CG location ) . . . The result was more of a "Spiral" than a flat glide.

When you see a real "free-flight" Competition B/G or R/G in flight, you will instantly see the difference !

The video's below show a "high-performance glide" by comparison . . . Yes, the mass would be higher for a rocket-powered glider, but the comparison is valid.

Remember that these flights are INDOORS with ZERO thermal activity ! ( The last video is a world record flight of nearly 2 minutes ! )




Dave F.
The Swinger was simply an example of apparently using dihedral in the stab vs the wings in answer to BABAR'S question.
 

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
The Swinger was simply an example of apparently using dihedral in the stab vs the wings in answer to BABAR'S question.
Eric,

I've seen Holverson Swinger's turn in some very good flights. The glider in that video appeared to be the victim of bad trimming.

Dave F.
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Eric,

I've seen Holverson Swinger's turn in some very good flights. The glider in that video appeared to be the victim of bad trimming.

Dave F.
Having the same problem with my clone. Fortunately I acquired an original in- the-bag kit and I'm looking forward to building and flying it to see if it flies any better, and if so, why?
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Per your first article: "The designer has typically arrived at a design by the built it, fly it and then build another one with some small improvements". I'm strongly considering doing just that with this build and the Icarus build to get both gliders as close to optimum as possible. Call it curiosity (or maybe obsessive-compulsive lol).
 
Last edited:

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
Eric,

I have a "theory" . . .

HYPOTHESIS : The "Tail Moment Arm" may play a big part in Glide Performance & Trimming.

(1) In those video's, all of the high-performance gliders have LONG Tail Moment Arms and glide extremely FLAT ( yes, the Wing Loading is super-low ).

(2) The Holverson Swinger has a SHORT Tail Moment Arm and a much steeper Glide Angle ( yes, the Wing Loading is higher ).

Whether a Conventional glider or a Canard glider, I believe that the effect of the Tail Moment Arm may be the same . . .

https://aviation.stackexchange.com/questions/47306/does-static-longitudinal-stability-require-download-on-the-tail

http://softskills4us.blogspot.com/p/aero.html

http://www.phoenixmp.com/articles/preptodesign.htm

EXCERPT :

2. Tailplane


The size of the tailplane is going to have a direct impact on the model's pitch stability along with the tail moment arm (distance between the mean chords of the wing and tailplane). Within reason larger the tailplane / moment arm the more stable the model. It is possible however to have too powerfull a tailplane whereupon in certain dive situations the tailplane takes over and holds the model in the dive until up elevator is applied. I experienced this on a number of occasions when I flew single channel gliders in the mid-sixties.

A starting point for tailplane area is 15% of wing area with a mooment arm of 3 x mean wing chord. The tailplane on 'Tee' tail models is more efficient than one fitted at the base of the fin so a slightly smaller tail can be fitted (12 - 15%). 'Vee' tail models have perform the function of both the fin and the tailplane. As a rough guide the fin area is approximately half that of the tailplane so the 'Vee' tail angle must be set to attain this ratio when the tailplane is veiwed from above and the side. If you do your sums this works out at approximately 110 degrees but for convenience I always use 120 degrees (60 / 30 set squares). Actual tailplane area needs to be increased by 2 - 3% to make up for the area 'lost ' due to the angle but it is still less than the total area of a conventional fin and tailplane. I have built a number of models that have been fitted with both a conventional tailplane and a Vee tail and in my experience the vee tail out-perform the conventional tail but they are aerodynamically less abusable without biting back! Basic trainers need good in pitch stability so fit a slightly larger tailplane of 18 - 20% of wing area.

Fin Area


As mentioned above the general rule for calculating fin area is half the tailplane area or 7 - 9% of wing area. Again the further aft the fin the more effective it will be. Please remember though that the fin still has to perform like a wing even though it is fully symmetrical and mounted vertically. It still has to produce 'lift', albeit horizontally. It is not just a paddle that is stuck out into the airstream.

Moment Arm

Choosing the correct moment arm is a bit of a compromise. The longer the tail moment arm the more stable the model will be in pitch and yaw for any given area but the model will require more nose weight to achieve the correct balance point . Long fuselages also increase the wetted area and the fuselage volume therby increasing parasitic drag i.e. drag not associated with lift production. Likewise a short nose moment will increase the weight required in the nose. Another side issue and quite an important one is that loong fuselages are more vulnerable to damage on an arrival due to the 'whiplash' effect.

A good starting point is to set the tail moment arm at 3 x Mean Wing Chord. The tail moment is the distance between the aerodynamic centres of the wing and tailplane. The aerodynamic centre of a section is assumed to be 25% back from the leading edge. Nose length can be provisionally set at 1.25 x Wing Root Chord.

END EXCERPT:

1606065322781.png



Dave F.
 
Last edited:

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Forgot to take shots of my version #2 build up to this point. It was basically a repeat of what I did earlier anyway.

I’m at the stage of assembling everything.

Did the best I could putting an airfoil on the 1/16” balsa canard. This shot is a bit low contrast, hope you can make out enough of the details.

canard airfoil.JPG

Finished all the parts and tissued the flight surfaces. What I like to do to ensure a good glue bond is to perforate both surfaces to be joined with a pin or a perforator wheel whenever possible.

IMG_5152.JPG
IMG_5146.JPG
IMG_5145.JPG
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
I decided to trim off a bit more weight by using a lighter xerclod/piece X pod mount rather than Apogee’s cast plastic glider pod hook like I usually do. (The small balsa piece X weighs in at only 0.10g vs the plastic glider hook’s 1.2g).

One thing I gotta recommend adding to anyone’s toolkit is a rotary cutter. It’s normally used for cutting fabrics but the super sharp wheel will cut through thick balsa like butter, and leaves a clean straight cut (assuming you keep your hand vertical) with no frayed balsa or chipped edges. Easy to use too, just roll it to cut with the razor sharp edge.

Anyway, there’s no way I could manage to get such a perfect fit trying to cut out the piece X with a hobby knife. I divided up the xerclod into sections so I can cleanly cut out the piece X, then glue the other pieces back together around it to get a perfect fit.

pylon and xerclod.JPG


I’m also going with a rear-eject pop pod system. https://www.rocketryforum.com/threads/ending-the-“red-baron”-curse.158166/
I like the reliability — In two years and 61 flights I’ve never had a Red Baron or failure using it.

rear eject pod.JPG
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Version 2 is done: lighter forward fuse, airfoiled canard, top-mounted fuselage, and a closer match to the prototype.
Final Ver2.JPG

Ver 1 vs Ver 2:
Ver 1 vs ver 2.JPG

Did some trimming tosses this morning and the revised version #2 only needed a tiny 0.09g dot of tail weight. Quite happy that the changes made a very noticeable difference in glide performance.

The original version is a tad heavier and while I’m not happy about that flap, I’m glad I had the opportunity to improve on the original design and learn something in the process. Oh well, guess I’ll be using version #1 as a second string wind/weather condition tester to see how conditions are at altitude before sending up my better version.

For comparison purposes, weight of the first version was 23.47g (0.827oz) vs this updated version’s 15.39g (0.542oz). May not seem like a really huge difference but it is when you consider their size (8” wingspan x 12.5” length). My similarly sized Pterodactyl weighs in at 31.36g (1.12 oz), or just about double my version 2 AeroDagger.
Aero2 vs Pterodactyl.JPG


I’m looking forward to an actual launch, though I’ll have to put it off until things are Covid safe. It should survive and do okay on a 1/4A3-3T or 1/2A3-2T. No matter what though, it’s been a fun project.
 
Last edited:

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
Eric,

Looking at the photo with Version #1 & #2 got me thinking about something that may not "crop up", until Flight Testing.

I am concerned that this design, both Version #1 & #2, might either "choose" to Invert or to remain inverted, if it happens to get into that flight orientation . . . I think this might, most likely, occur at Transition, or if the Glider were to Stall.

My hypothesis is based on :

(1) Zero Wing Dihedral.
(2) Upright Vertical Rudders ( as opposed to "under-slung" ones ) may tend to act as a "pendulum", if the Glider "inverts".
(3) Canard Dihedral - The Canard, even with Dihedral, might not create sufficient force to "right" the Glider, if it "inverts".
(4) The Angle of Attack of the Canard might induce a "Dive", if the Glider "inverts".

Just a "concern", hopefully unjustified !

Dave F.

1606318565270.png
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Put in some protection from the blast of the motor exhaust with self-adhesive aluminum duct tape. Works well but it’s a major PITA to get it to lay down smoothly. Final result covers up a lot of the visual interest (the internal framework) but better that than starting a grass fire from a flaming glider (spectacular as that might be). 🔥 😬

Alumin tape shield.JPG
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Suggestion on what I can do on the version 2 model since the fuselage runs above the wing surface?
High-heat paint? Trying to manhandle that sticky tape would be a nightmare; it wrinkles with the slightest bend and once any part touches the surface it sticks tenaciously and is almost impossible to pull up without damaging the surface. I pretty much only get one shot at it and I’d really hate if it ended up looking like a piece of crumpled aluminum foil was just stuck down to that fuse spine.

external spine Ver2.jpg
 
Last edited:

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
Suggestion on what I can do on the version 2 model since the fuselage runs above the wing surface?
High-heat paint? Trying to manhandle that sticky tape would be a nightmare; it wrinkles with the slightest bend and once any part touches the surface it sticks tenaciously and is almost impossible to pull up without damaging the surface. I pretty much only get one shot at it and I’d really hate if it ended up looking like a piece of crumpled aluminum foil was just stuck down to that fuse spine.
I like the idea of the high-temp paint ( probably less Mass than Tape ).

As for the possible "Aerodynamic concerns", I suggest to just fly it and, if the problem arises, address it at that point.

Dave F.
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Eric,

Looking at the photo with Version #1 & #2 got me thinking about something that may not "crop up", until Flight Testing.

I am concerned that this design, both Version #1 & #2, might either "choose" to Invert or to remain inverted, if it happens to get into that flight orientation . . . I think this might, most likely, occur at Transition, or if the Glider were to Stall.

My hypothesis is based on :

(1) Zero Wing Dihedral.
(2) Upright Vertical Rudders ( as opposed to "under-slung" ones ) may tend to act as a "pendulum", if the Glider "inverts".
(3) Canard Dihedral - The Canard, even with Dihedral, might not create sufficient force to "right" the Glider, if it "inverts".
(4) The Angle of Attack of the Canard might induce a "Dive", if the Glider "inverts".

Just a "concern", hopefully unjustified !

Dave F.
No worries, deltas don't require dihedral.

Deltas that come to mind that fly sans dihedral: the Modelrockets.us Quick Fly, Estes Gryphon, and Edmonds CiCi, Ecee, and Deltie. Coincidentally they even have top-mounted fuselages.
 

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
No worries, deltas don't require dihedral.

Deltas that come to mind that fly sans dihedral: the Modelrockets.us Quick Fly, Estes Gryphon, and Edmonds CiCi, Ecee, and Deltie. Coincidentally they even have top-mounted fuselages.
Eric,

I was thinking that "dihedral effect" might encourage an inverted glider to right itself . . .

What is the source of info for delta wings not requiring dihedral ?

I would like to read more about that.

Thanks,

Dave F.
 

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
Eric,

I was thinking that "dihedral effect" might encourage an inverted glider to right itself . . .

What is the source of info for delta wings not requiring dihedral ?

I would like to read more about that.

Thanks,

Dave F.
Excerpt:
"An additional reason for using swept or delta wings is that they exhibit a beneficial dihedral effect. When an airplane is in a roll, it tends to side-slip to the inside. Dihedral creates a rolling moment, tending to roll the airplane upright. Swept and delta wings exhibit this characteristic. For example; the wing on my canard has no dihedral, but the 35-degree sweepback provides dihedral effect. An advantage in using a swept or delta wing and no dihedral is that the airplane will exhibit the same dihedral effect when upright or inverted. Still another advantage is a beneficial effect added to the airplane's directional stability. "
End Excerpt
https://www.airplanesandrockets.com...ters-april-1968-american-aircraft-modeler.htm

I never bothered to download the math/formulas and aerodynamic physics behind why, they were too much for me to deal with, but I'm sure you can find additional tech articles with them online.

Also mentioned in attached pdfs:
 

Attachments

Last edited:

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
To lessen any tendency to loop, especially with the "flapped" version 1, I built the pop pod so that the boost CG falls right over the canard wings.

I want to build a final "high wing" version (fuselage on bottom) because it's so much easier to apply the exhaust protection tape on the flat top surface. Also might try a few other tweaks to see the effect.

I'm going to take a break from this project to whittle down my build pile, and will return to it after I maiden these two. Will provide video if I can, or at least a flight report.
 
Last edited:

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
Excerpt:
"An additional reason for using swept or delta wings is that they exhibit a beneficial dihedral effect. When an airplane is in a roll, it tends to side-slip to the inside. Dihedral creates a rolling moment, tending to roll the airplane upright. Swept and delta wings exhibit this characteristic. For example; the wing on my canard has no dihedral, but the 35-degree sweepback provides dihedral effect. An advantage in using a swept or delta wing and no dihedral is that the airplane will exhibit the same dihedral effect when upright or inverted. Still another advantage is a beneficial effect added to the airplane's directional stability. "
End Excerpt
https://www.airplanesandrockets.com...ters-april-1968-american-aircraft-modeler.htm

I never bothered to download the math/formulas and aerodynamic physics behind why, they were too much for me to deal with, but I'm sure you can find additional tech articles with them online.

Also mentioned in attached pdfs:
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.
 
Last edited:

Rktman

Eric
TRF Supporter
Joined
Mar 5, 2017
Messages
1,146
Reaction score
131
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.
IDK, maybe the physics of a plane that much larger isn't quite the same?
 

Ez2cDave

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
3,889
Reaction score
1,074
IDK, maybe the physics of a plane that much larger isn't quite the same?
I suspect that other forces may have been at work, as it was under power versus being a glider. Airspeed, torque from the engines, the fact the part of the right Rudder remained, after impact . . . The fact that the Pilot was, initially, unaware there was a problem . . . Probably others, too !

My "instinct" would have been to "droop" the Wing Tips to their maximum downward angle ( to try to get some "Rudder effect" ) and use the Flaps to introduce some Camber and induce "Base Drag", in an effort to try to stabilize it like a "Dart" ( possibly lower the Main Landing Gear ), all to PREVENT a Spin . . .

Many possibilities, but little time for "experimentation" ! ( Just some "arm-chair quarterbacking" - LOL ! )

Dave F.
 
Last edited:
Top