Cormorant II

[Pieliker96]

Killer. Show us the belly!

As you wish.

 

[Matthewdupreez]

As you wish.

View attachment 186355

could it be made without the droperons

 

[Matthewdupreez]

and do you think you could mount 1 c pack motor in the tail... instead of 2 f pack motors?
but keep the wing motor pods(without motors in them obviously)

 

[Pieliker96]

could it be made without the droperons

Yes, absolutely. They are very much optional as a way of changing the plane's performance in a way that remains to be seen - I figured I wanted a good bit more aileron surface area than I was able to get with the flaps where they were and so chose to put it on the leading edge. If you'd like to make the plane a tad more beginner-friendly you can build them and then tape or glue them in their fully drooped position so they act as a leading edge cuff, which should delay stall of the wingtips by decreasing the effective angle of attack of the outer wing.

and do you think you could mount 1 c pack motor in the tail... instead of 2 f pack motors?
but keep the wing motor pods(without motors in them obviously)

You probably could, but there are two major factors that cause me to not recommend this: First, the elevator must be able to deflect downwards, which puts it right into the space where the motor or its supporting structure would be. You could split the elevator on either side of the fuselage to get around this, but I don't think you would have an optimal experience due to the next factor: Prop clearance. As it sits, it has ~6.5" of prop clearance. When at its maximum ground angle of attack, resulting in a tailstrike, that decreases by nearly five inches, leaving you with less than two inches of clearance. Using a single power pack C as pusher with this design would not allow the plane to perform its best by severely limiting the angle of attack on takeoff and landing.

 

[Pieliker96]

I couldn't help myself - I had to give it some sort of paint scheme and detailing before the maiden flight. I pencilled in some panel lines with the help of a flexible ruler and smudged them with my fingertips to give them some more weight and definition. I added streaking around the nacelle exhausts, near the landing gear, and around the flaps and such to give it a dirtier look - again, all done with pencil and blended quite literally by hand. But that wasn't quite enough for me - the build was lacking in contrast. I painted all of the control surfaces black as I had done in the renders, which really made it come alive. The significant areas of overspray got turned into areas of battle damage with some bullet holes and streaking, done with pencil and sharpie. Parts where the paint had bled under the tape got blended into streaking and soot from gradual wear and tear. I think I've captured the "scuffed and well-worn aerospace" aesthetic quite well, it's turned out as a sort of mishmash of aeroplane and spacecraft, which is rather fitting given what it's based on.

And, of course, here's the maiden flight:

It has a healthy excess of power, decent stability, and decent maneuverability - aileron rolls were quite easy and carefree. I did a quick test of the flaps. Half-deployed felt as I would expect and is what I ended up using for landing. Full flaps caused a good bit of porpoising, probably from partial blanking of the horizontal stabilizer - I felt as if I still had a tad bit of elevator control but it was greatly reduced. I noticed a significant increase in power required for full flaps as well. Further flight testing will determine full flaps' controllability and effectiveness. Initial performance in all regards can be considered satisfactory, and I've yet to take this thing to the corners of its flight envelope.

I have the v1.0 plans done, but they'll have to wait until I'm done editing the ~12 hours of build footage I'll have to sift through - not that the build process itself will be 12 hours long, but that filming something while doing it seems to incur a rather large time penalty.

 

[Pieliker96]

The final release plans are up in the resources tab, the build video is as well - all three hours of it!

Cormorant II Plans v1.0

 

[Pieliker96]

I put two more packs through it today: I tested flight with both levels of flaps, stalls in all configurations, and spins. The plane has proven itself to be capable of taking off grass with the 1.25" nose wheels, although not as gracefully as I would like. The measured thrust-to-weight ratio with 6x3 props was just slightly over one, although it performed as (and theoretically should be) well over one in flight - some of the thrust was being converted to lift and drag from the thick wing behind the props, it takes up a good bit of disk area. I've ordered some 6x4.5 and 5" three-blade props to push the limits of the FT 20A ESC, potentially achieving more static thrust and speed in the process.

EDIT: the 6x4.5 two-blade props (Bull Nose) got the static TWR up to the design spec of 1.5 at the expense of powertrain efficiency. I'd recommend these over the 6x3s as they give a much higher performance ceiling with a small hit to cruise performance. The FT 20A ESCs got a bit toasty but handled the load without any thermal protection kicking in.

Flaps
The plane remained controllable and stable in all flap configurations, no significant blanking effects were observed. The power to pitch coupling was little to none when the flaps were retracted or in their intermediate position. When the flaps were fully extended, a significant coupling was observed: Gunning the throttle would push the nose down decently hard. This is likely due to the flaps' externally blown nature and their location behind the CG. This has been mitigated with a 20% throttle to elevator mix active only when the flaps are fully deployed: Elevator is proportionally coupled to throttle to where at full throttle, 20% extra up-elevator is applied.

Stalls
With the flaps up, it is quite forgiving - it rocks its wings and remains upright. The amplitude of the rocking increases over time but seems to achieve a stable maximum. With flaps at half, the story similar, although the nose was able to achieve a higher angle relative to the horizon. The rocking was higher in magnitude than without flaps and threatened to roll the plane past 90* of bank once the stall was fully developed. With full flaps, the plane again rocked its wings and achieved a higher nose-high attitude than previous, with the amplitude of rocking increasing over time and threatening to overturn the plane. Overall, the stall characteristics were rather docile. The rocking took a decent length of time to develop into dangerous territory and never resulted in a loss of control or significant attitude upset. There's headroom in moving the CG aft for those who want maximum STOL and aerobatic performance - If I release an update to the plans, I'll make the battery tray larger by extending it backwards, allowing for this (currently, however, the CG works fine where it is, aft CG is not a priority).

Spins
Spins were easy to do: Stall the plane, hold full up elevator, and bring it around with differential thrust. The plane spun in a nose-down attitude - flat spins may be achievable with moving the CG aft.

 

[Crawford Bros. Aeroplanes]

That's beautiful

 

[L Edge]

What was your max angle for the drooperons?

 

[Pieliker96]

What was your max angle for the drooperons?

28 degrees from center either way

 

[CampRobber]

I like this airplane. If you would like to collect and share performance data (i.e. speed/power curve at various weights, most efficient cruise speed, etc) for the Cormorant II I'd be willing to donate an FC and GPS to the cause.

 

[Pieliker96]

I like this airplane. If you would like to collect and share performance data (i.e. speed/power curve at various weights, most efficient cruise speed, etc) for the Cormorant II I'd be willing to donate an FC and GPS to the cause.

That sounds interesting. I've had inklings of doing flight performance analysis for a good while now - dm me about it.
With that said you'll likely be waiting for a good bit. I'll be away for college shortly till at least May. That, and the exact minute you posted this, its most recent flight (swinging 6x4.5 props giving a TWR of ~1.5) ended in an unfortunate run-in with a tree - video coming soon.


Skis for the nose and main gear, simply attached with rubber bands.

Some clear shots of the skis in-flight.

Cruising around. Note the deployed flaps.

Sequence of the unintentional arbor-braking and subsequent uncontrolled lithobraking of the Cormorant II


The aftermath - note the half of the prop blade sticking out of the fuselage! Surprisingly, the nose was barely damaged. It looks repairable, and it's very much in the spirit of this paint scheme to be imperfect and scuffed. I'll see what I can to to get it back in the air.

 

[dani1390]

The aftermath - note the half of the prop blade sticking out of the fuselage! Surprisingly, the nose was barely damaged. It looks repairable, and it's very much in the spirit of this paint scheme to be imperfect and scuffed. I'll see what I can to to get it back in the air.

Hi my friend, your efforts are appreciated and I hope you can fix it as soon as possible.

 

[Pieliker96]

Hi my friend, your efforts are appreciated and I hope you can fix it as soon as possible.

Thank you for the kind words! I'm in the process of doing so, and I appear to have got rather lucky: most of the foam isn't permanently deformed; the parts just glue back together! Here's the video illustrating the improved thrust-to-weight ratio, some mild aerobatics, and, of course, the crash. It also includes a view from under the wing of the flaps, ailerons, and drooperons doing their thing.

 

[Pieliker96]

And just like that, it's back and ready for action

 

[L Edge]

Glad it is back in action. There is certainly a lot of information to be gleaned out of your setup.

 

[dani1390]

View attachment 187626 View attachment 187627
And just like that, it's back and ready for action

View attachment 187625

Your efforts and perseverance are appreciated .

 

[Pieliker96]

Your efforts and perseverance are appreciated .

Thank you!

I know y'all have probably seen enough of this plane already but I think this is one of the best pictures of it I've got so far:

The skis work great on proper snow. They've been added to the plans, along with some changes to the battery tray and minor fixes.

Here's some guidance on building the skis, which are available in v1.1 of the plans:
Start with the Main and Nose Skis. Bend up the radiused nose (you can use the 20° angle gauge for the wingtips here too) and glue them in place. Next, cover the bottom of the skis in packing tape, making sure to bring the tape over the edge and onto the top of the ski to prevent the paper from delaminating. Then take both the main and nose plates and peel the paper off the side with the score cuts. Open up those score cuts with skewers, and cut the skewers such that there is around 3/8" of length on either side of the plate. Glue the skewers into the score cuts, glue the plate with cut side down onto the skis, center them in the rectangular section. Once they have dried, peel the paper off the top of the plates. Next, take the two main chocks. Crease them in the middle to a 90° angle and bevel the edges. Glue them between the two cutouts in each main gear plate. These will sit between the wheels and serve to keep the ski from moving fore and aft. Next, cutout the wheel guards and take the paper off both sides. Glue these onto the plates to the side of the wheel cutouts: there should be two on each side of each wheel to prevent the skis moving side to side.

To install the main skis, you'll need four rubber bands. Pass the bands under each wheel such that the two ends of the loop are on top of the wheel - this can be accomplished by bringing the loop under the wheel (up into the wheel pant) and rotating it such that it brings the other end of the loop around the other side. Repeat this for all four main wheels, then attach them by looping the bands around the skewers. This process can be repeated for the nose gear, although you may have to use a smaller band (or twist it back on itself to form two loops). Attach a piece of scotch tape to the nose of the nose ski and tape it securely to the underside of the nose. Make sure there is sufficient slack in this such that it will not pull itself off if the nose gear is fully compressed but not loose enough to where the ski refuses to stay facing straight ahead.

 

[dani1390]

Thank you!

I know y'all have probably seen enough of this plane already but I think this is one of the best pictures of it I've got so far:

View attachment 187818

The skis work great on proper snow. They've been added to the plans, along with some changes to the battery tray and minor fixes.

Here's some guidance on building the skis:
Start with the Main and Nose Skis. Bend up the radiused nose (you can use the 20* angle gauge for the wingtips here too) and glue them in place. Next, cover the bottom of the skis in packing tape, making sure to bring the tape over the edge and onto the top of the ski to prevent the paper from delaminating. Then take both the main and nose plates and peel the paper off the side with the score cuts. Open up those score cuts with skewers, and cut the skewers such that there is around 3/8" of length on either side of the plate. Glue the skewers into the score cuts, glue the plate with cut side down onto the skis, center them in the rectangular section. Once they have dried, peel the paper off the top of the plates. Next, take the two main chocks. Crease them in the middle to a 90* angle and bevel the edges. Glue them between the two cutouts in each main gear plate. These will sit between the wheels and serve to keep the ski from moving fore and aft. Next, cutout the wheel guards and take the paper off both sides. Glue these onto the plates to the side of the wheel cutouts: there should be two on each side of each wheel to prevent the skis moving side to side.

To install the main skis, you'll need four rubber bands. Pass the bands under each wheel such that the two ends of the loop are on top of the wheel - this can be accomplished by bringing the loop over the wheel and rotating it such that it brings the other end of the loop around the other side. Repeat this for all four main wheels, then attach them by looping the bands around the skewers. This process can be repeated for the nose gear, although you may have to use a smaller band (or twist it back on itself to form two loops). Attach a piece of scotch tape to the nose of the nose ski and tape it securely to the underside of the nose. Make sure there is sufficient slack in this such that it will not pull itself off if the nose gear is fully compressed but not loose enough to where the ski refuses to stay facing straight ahead.

View attachment 187843 View attachment 187845 View attachment 187844 View attachment 187846

The description was excellent and the pictures were very clear.

 

[Battery800]

awesome! I might try this with my spare f pack motors, but I'm sure I won't use drooperons yet