Apogee Mini Copter

[kuririn]

This is a 13mm power helicopter recovery rocket. Started the build today. It comes with an instructional DVD in 13 parts, also on YouTube. So I won't go into the finer details of the build.
First, the parts:


First step is to bend the rotor blades with an ammonia/water solution. I used a BT-5 tube, drew a straight line with an angle tool, taped a strip of wax paper to it, sprayed the rotor blades with the ammonia solution (50/50), aligned the edge with the line, and wrapped it. Will let dry overnight and see what I get tomorrow (hopefully a nicely curved blade).


TBC

 

[BEC]

That is quite an interesting build. I built two of them for NARAM-61. Have fun!

 

[kuririn]

Hey Bernard. How did they perform?

Unwrapped the rotors this morning. Nicely curved, looking good.
Building the hub later today.

 

[mbeels]

Ooooh, that did come out well. Makes me want to build a 'copter.... I'll be curious to see what the hub looks like.

 

[BEC]

Hey Bernard. How did they perform?

Unwrapped the rotors this morning. Nicely curved, looking good.
Building the hub later today.

I did my blades exactly the same way, wrapping them on sections of BT-5.

They spin up very nicely once you learn how to pack the kevlar shock line so that the blade assembly ejects smoothly and completely. I didn't do too well at NARAM (flying them on 1/4A3-3Ts) mainly because of my adjusting the wrong way on my piston launchers and getting little benefit from them.

We had a little informal "first day of the new contest year" gathering on the Sunday after NARAM at which I put up a 62 second flight with one on a 1/2A3-4T and a much more properly fitted piston launcher. That was pretty good.

They boost very nicely as they should, but come down rather faster than I expected. I think the only real modification I did on the build was to substitute fins of 1/64 inch plywood for the 1/16 inch balsa ones for drag reduction.

Have fun with that hub....it's a very in interesting little build in and of itself.

 

[kuririn]

Okay, hub is (mostly) complete.

Have fun with that hub....it's a very in interesting little build in and of itself.

Bernard, you have a remarkable propensity for understatement.
Interesting is not the word I would use. More like a royal PITA.
Here it is on a music wire while the thick CA on the pins dries:

I don't have a clay or putty epoxy so I'll use a paste epoxy to lock down the pins after the CA dries.
Went a little off script in this assembly by swiping thin CA on all the fragile wood parts beforehand.
Hopefully it will add more durability, especially to those stops on the swing arms.
The video said this was the hardest part, it's all downhill after that. Thank God.
Laters.

 

[BEC]

I didn’t want to scare you off before you tried to do it. I wound up ordering the epoxy clay as I had nothing else on hand to do that job. CA getting into the pivots at this point would be disastrous.

There’s not much load on the blade stops, but a little reinforcement probably isn’t a bad idea.

 

[burkefj]

This is a weird rocket glider if I ever saw one

 

[kuririn]

Frank, this sub-forum includes rockets with helicopter recovery.

Rocket Boosted Gliders
For discussions about all types of rocket boosted gliders. Parasite gliders, boost gliders, rocket gliders, flex-wing gliders, lifting bodies and R/C variants. Also the place for helicopter recovery.

 

[kuririn]

Did a little more work last night/this morning:
Assembled the nose cone/graphite rod assembly and glued on the hub.

CA'd the reinforcing mesh on the rotors, decided to CA the entire rotor. Sanded smooth when dry.
Assembled the motor mount.
Shaped the fins. Will be painted with thin CA.
Headed for the homestretch.


BTW hope you have your ears on Andrew_ASC. This build thread was at your request.
Laters.

 

[mbeels]

CA'd the reinforcing mesh on the rotors, decided to CA the entire rotor.

What is the reinforcing mesh? A fabric of some sort?

 

[BEC]

The “mesh” looked and handled like heavy silkspan. Those of you who built rubber-powered airplanes long ago will know what that is.

 

[kuririn]

What is the reinforcing mesh? A fabric of some sort?

It's a gossamer thin fabric mesh. You can see it in the first photo in the plastic bag under the balsa sheet with the discs. I guess it's the modern day equivalent of gauze reinforcement. Don't know what it's called.
Did a little more work this evening. Glued the Kevlar shock cord to the graphite rod and wrapped it with red thread, then soaked it with thin CA. Glued in the motor mount, fins, and launch lug. Changed my mind on painting the fins with CA like in Tim's video. Opting for the conventional fill, sand, primer, paint routine. The fins are not swept back and the motor tube extends back a bit so they're not especially vulnerable to damage.

Calling it a night. Time to binge watch Season 4 of The Expanse for the second time. I missed a few things the first time around.
Laters.

 

[Rktman]

Assuming those rotors don't require airfoiling due to the curve/twist in them?

 

[kuririn]

Assuming those rotors don't require airfoiling due to the curve/twist in them?

That, and they are so thin that I think sanding a taper on the trailing edge would make it thin as paper.
On the video just moving the rocket a few inches downward caused the rotors to rotate due to air flow.
For competition a tower launcher would be used instead of launch lugs. I'm building for fun.
Anyhow, blades are going to be balanced and go on the hub later today.
Right now I'm finishing up this build:

Gluing on the fin can segments for an Aerotech HV Arcas. Then internal and external fillets, glue on the aft centering ring and motor retainer and done. A BF special from Buyrocketmotors.com.
Stay tuned, folks.

 

[BABAR]

That, and they are so thin that I think sanding a taper on the trailing edge would make it thin as paper.
On the video just moving the rocket a few inches downward caused the rotors to rotate due to air flow.
For competition a tower launcher would be used instead of launch lugs. I'm building for fun.
Anyhow, blades are going to be balanced and go on the hub later today.
Right now I'm finishing up this build:
View attachment 401442
Gluing on the fin can segments for an Aerotech HV Arcas. Then internal and external fillets, glue on the aft centering ring and motor retainer and done. A BF special from Buyrocketmotors.com.
Stay tuned, folks.

Okay , throwing in the Arcas in this thread is just wrong. I mean, it’s kind of like 9 chapters of Tinkerbell and then a section on the Hulk.

 

[kuririn]

I like Tinkerbell and the Hulk. They make a good team.

 

[BABAR]

I like Tinkerbell and the Hulk. They make a good team.

They’re both green!

 

[kuririn]

Babar, I'm green with envy after seeing some of your models.
The rotors are on!
Colored with Sharpies. Used highlighter for the orange, result is spotty so will come back with an orange felt pen.
Black on the underside for visibility, as per the video.


While I had the orange highlighter out I re-did my orange Fliskits crayon rocket.
It was near a window and the UV rays turned the orange into gray.



The rotors were evenly weighted and balanced with a small amount of clay on the two lighter rotors.



Close up of the mechanism in launch mode.
Tolerances are tight.
I had to sand the tops of the hooks down slightly to get the assembly to fit the tube.


External fillets are applied, and assembly is complete!


Filler, primer, paint over the next several days.
Will post a pic of the completed model.
Whew, this was a challenge! But too much fun.
Merry Christmas Everybody!

 

[BABAR]

Babar, I'm green with envy after seeing some of your models.
The rotors are on!
Colored with Sharpies. Used highlighter for the orange, result is spotty so will come back with an orange felt pen.
Black on the underside for visibility, as per the video.
View attachment 401521

While I had the orange highlighter out I re-did my orange Fliskits crayon rocket.
It was near a window and the UV rays turned the orange into gray.
View attachment 401524


The rotors were evenly weighted and balanced with a small amount of clay on the two lighter rotors.

View attachment 401522

Close up of the mechanism in launch mode.
Tolerances are tight.
I had to sand the tops of the hooks down slightly to get the assembly to fit the tube.
View attachment 401523

External fillets are applied, and assembly is complete!

View attachment 401525
Filler, primer, paint over the next several days.
Will post a pic of the completed model.
Whew, this was a challenge! But too much fun.
Merry Christmas Everybody!

Try not to thermal it to Santa on its first flight!

 

[mbeels]

Looks good! What motor are you going to use for the first flight?

 

[kuririn]

1/2A for the shakedown. Want to see how much it drifts. Then maybe an A. Or not.

 

[Rktman]

Babar, I'm green with envy after seeing some of your models.
The rotors are on!
Colored with Sharpies. Used highlighter for the orange, result is spotty so will come back with an orange felt pen.
Black on the underside for visibility, as per the video.
View attachment 401521

While I had the orange highlighter out I re-did my orange Fliskits crayon rocket.
It was near a window and the UV rays turned the orange into gray.
View attachment 401524


The rotors were evenly weighted and balanced with a small amount of clay on the two lighter rotors.

View attachment 401522

Close up of the mechanism in launch mode.
Tolerances are tight.
I had to sand the tops of the hooks down slightly to get the assembly to fit the tube.
View attachment 401523

External fillets are applied, and assembly is complete!

View attachment 401525
Filler, primer, paint over the next several days.
Will post a pic of the completed model.
Whew, this was a challenge! But too much fun.
Merry Christmas Everybody!

Yikes, that IS a tight fit! Maybe baby-powder the inside of the body tube? Looking forward to your flight report.

 

[Andrew_ASC]

BTW hope you have your ears on Andrew_ASC. This build thread was at your request.
Laters.

Many thanks. This little kit makes me nervous. Mainly the blade and hub...

 

[Crawf56]

Sorry I am late to this game......

Do the instructions call out for the rotor blades to be curved? Some intricate work there, kuririn.

 

[BEC]

Not to sound flip or anything but....did you read the first post?

Curving the blades is the first step.

 

[Crawf56]

Not to sound flip or anything but....did you read the first post?

Curving the blades is the first step.

Yes, I did. But I wanted to verify that the curved blades were an actual step in the instructions, rather than a design choice by kuririn.

I have never put together a helicopter recovery rocket, but I have considered them several times. Do these models typically have curved rotor airfoil, or is this model unique in the curved design?

 

[Andrew_ASC]

Um I’ve seen one heli-rocket at Camden last year have flat blades but it was much bigger and took G motors. Oddly the blades had so much rotational inertia and mass that there were issues with hinges plastic r/c type snapping on landing. I wanna say it was something Gary Bayrum did scratch build. But he’s dead now.

The airfoils should massively help reduce descent rate by providing lift force increase as rotor speed increase. I picked up this kit as a curiosity item mainly lol.

 

[kuririn]

Do the instructions call out for the rotor blades to be curved?

Yeppers, the instruction for curving the blades are on You tube as well as the DVD:

Links to all the 13 videos are on the kit description page at Apogee, as well as an explanation of why curved blades are more efficient.
I'm thinking a tiny bit of WD-40 between the alum. tube and graphite rod might reduce friction and increase spin even more.
We'll see.

 

[BEC]

I have never put together a helicopter recovery rocket, but I have considered them several times. Do these models typically have curved rotor airfoil, or is this model unique in the curved design?

As others have noted this is indeed part of the design of this model. I don’t think the blades would even go in the tube if left flat.

I have only built one other heli so far - the Estes Mini-A Heli. On this one the sheet blades are cracked along a laser-etched line to form a sort of cambered airfoil with the aid of three slide-on guides to hold the intended angle.

That build is much easier both for the blades and the hinges, but it is much larger, heavier and draggier in boost configuration so doesn’t do as well on 1/2A motors.