Vortex – helicopter scratch build

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To my knowledge I don't think any of the sim programs work well with non-cylindrical rocket bodies. Although I would be happy to find I was wrong. Apogee had an article on this a while back with some mods, but it was way over my head.

Aha, here it is
https://www.apogeerockets.com/education/downloads/Newsletter296.pdf


Thanks for the link. I think I get the gist of the article and it's a keeper because I may graduate to RockSim at some point. I think I'll just err on the side of safety this time and add a bit of lead weight to the nose cone. Better to be "over stable by design" than have it do the sky writing thing.
 
Guess the test flight is going to have to wait awhile. Caught a really nasty flu and missed my opportunity this past weekend. It looks like I'm going to be sidelined for quite a bit.
 
Finally had the chance for a test flight and happily the Vortex put in a great low level B4-2 performance. Unfortunately my camera wasn't up to the task. I caught only a few seconds of video...enough to verify that 1) the model is satisfyingly stable and 2) deployment and rotation worked quite well...before the camera cut out. Not sure what happened but it was probably my fault since the battery was just about empty. So apologies in advance for the crummy video.

[video=youtube;qN0BUhYOFC8]https://www.youtube.com/watch?v=qN0BUhYOFC8&feature=youtu.be[/video]


Things would have ended on a happy note but I just had to try a 2nd flight on a C6-3. Did I listen to that nagging little voice in my head warning me the park was just a little too miniscule and the wind was picking up? Oh no, of course not. It left the pad fine but a freak gust sent it right into the treeline, where it straight away bored first through one tree canopy and then right through its neighbor's still under boost. The branches/leaves stripped off all three rotor blades and chunks from the fin but it somehow miraculously managed to survive with only a few minor paint scuffs to the nose cone and body.

But I never did find the rotors. Of course I only managed a couple of minutes of searching in the 102° heat. What disturbs me more was that not even one of the rotors survived being torn off. My thought is that the hinges would have done better if they had been reinforced by sewing thread through the hinge holes the way competition helicopter models frequently have theirs done. It keeps the rotors attached in case the CA gives out. I considered doing that but got lazy. Oh well, hindsight is such a wonderful thing. At least I know the rotor retention method (upper body slip tube) is uncomplicated, easy, and works well.
 
DOOD! That's a real bummer. Gotta say tho, I have never used any kind of hinge like that. Mainly because I know what works for me. And #2) I would never use CA glue for any major construction job. I didn't want to say anything back when you were "buttering the hinge" because I wasn't sure if you knew something I didn't. Anyhoo, I do have a suggestion for the refitting of the props. When I built my upscale Gyroc, I blew off using that flexible crap that came stock with the kits and opted for brass hinges. Brass? These are easy to find at Lowe's, they're really light weight, and epoxy sticks to them very well. In the pics below, I marked around the hinges, then made a cut deep enough to recess the hinge into the wood enough to be flush with the surface. I chiseled out the wood like you might to hinge a door on a frame, took some heavy grit sandpaper and roughed the bottom/glue side of the hinges. This is so when you apply EPOXY, it has that rough surface to stick to better. I then pushed more epoxy in the screw holes and enough to make a level surface on the fins. Gotta say, that Gyroc has seen a great many flights and those hinges are stuck very well. Used the same method for both my heli jobs. Epoxy is your friend!!!

DSCF3176.JPG DSCF3180.JPG
 
DOOD! That's a real bummer. Gotta say tho, I have never used any kind of hinge like that. Mainly because I know what works for me. And #2) I would never use CA glue for any major construction job. I didn't want to say anything back when you were "buttering the hinge" because I wasn't sure if you knew something I didn't. Anyhoo, I do have a suggestion for the refitting of the props. When I built my upscale Gyroc, I blew off using that flexible crap that came stock with the kits and opted for brass hinges. Brass? These are easy to find at Lowe's, they're really light weight, and epoxy sticks to them very well. In the pics below, I marked around the hinges, then made a cut deep enough to recess the hinge into the wood enough to be flush with the surface. I chiseled out the wood like you might to hinge a door on a frame, took some heavy grit sandpaper and roughed the bottom/glue side of the hinges. This is so when you apply EPOXY, it has that rough surface to stick to better. I then pushed more epoxy in the screw holes and enough to make a level surface on the fins. Gotta say, that Gyroc has seen a great many flights and those hinges are stuck very well. Used the same method for both my heli jobs. Epoxy is your friend!!!

View attachment 326568 View attachment 326569


Guess I'm down to just 2 models for Freedom Launch since I won't have time enough to do all the
repairs, but I'm going to take your suggestion of using epoxy and brass hinges if I can find hinges small
enough to fit the narrow 1"w rotors. I have some 2 part epoxy putty, do you think that'll work as well
as the 2 part liquid variety?

I'm out of my experience zone here, so do you think I should carve hinge reliefs on the rotors too? Or would that
weaken them too much? I'm also wondering if pushing small needle heads with about 1/8" of their shaft through the
hinge screw holes would help keep them attached?
 
Guess I'm down to just 2 models for Freedom Launch since I won't have time enough to do all the
repairs, but I'm going to take your suggestion of using epoxy and brass hinges if I can find hinges small
enough to fit the narrow 1"w rotors. I have some 2 part epoxy putty, do you think that'll work as well
as the 2 part liquid variety?

I'm out of my experience zone here, so do you think I should carve hinge reliefs on the rotors too? Or would that
weaken them too much? I'm also wondering if pushing small needle heads with about 1/8" of their shaft through the
hinge screw holes would help keep them attached?

Those brass hinges are 3/4" wide. Worked great on my 1" props on the little Cloud Chopper. NO! I would not recommend epoxy putty because I never tried it that way. I used 2 part liquid. The small chopper has thin wood props and the hinges were surface mounted. I ran 3/4" screws into the part that attaches to the airframe because they also went inside the nose cone shoulder. Just long enough so they didn't poke out the other side. I used epoxy on the side where the props attach and a much shorter screw. Those did pop out some but I used something like epoxy putty to cover the points and round them off. They look like little lumps but they paint over nicely. I'll bring it to the launch and show you what I did. Better to show you than try to explain it. The thicker the wood prop is, the more you may consider some hinge relief. I did that with the Big Chopper and I CA'd the relief area to strengthen it up.
 
Glad you got one good flight!
Yup, that temptation to go up a motor has been the death knell for many a rocket!
Now you know why I don't do a lot of finishing work on my sporting Rockets. They may not survive to become hangar queens.
 
Glad you got one good flight!
Yup, that temptation to go up a motor has been the death knell for many a rocket!
Now you know why I don't do a lot of finishing work on my sporting Rockets. They may not survive to become hangar queens.

She's currently in the intensive care unit awaiting reattachment of cloned rotors. Regardless of the outcome her legacy will be sturdier progeny based on her DNA.
trytofly.gif
 
Finally found some time to do some repairs. On closer inspection I discovered some internal injuries that I didn't notice before;
although the BT isn't bent the impact caused the tube to "unwind". I shoved a coupler down and soaked the tube sides with CA.
Seems to have done the trick.

IMG_0222-split tube.jpg


The fin units were in worse shape with large ragged holes torn in the leading edges. This is my first experience with epoxy putty
and I have to say that stuff is a dream. Workable like clay and a wet finger is all it took to knead and smooth it. Dries hard as a rock
and sandable too. The end result looks pretty crappy, like a rusted out car with bondo patches on it but I'll probably just paper it or
skin it with self adhesive vinyl or monokote or something.

IMG_0226-fin patch.jpg


I also cut some new rotors, though these will by necessity be shorter since I can no longer attach it to the fin units. Unfortunately they won't
provide as much lift since they're 2.5" shorter x 3, so instead of doing the diagonal bent-blade thing I'll be carving airfoils into them.
I've noticed that with the bent blade technique the rotors don't start rotating immediately like with airfoiled rotors, and since this is a
heavier model with less rotor area now, I'd prefer it to start spinning right away to provide a softer landing.

IMG_0228-nrw rotors.jpg

Hope to get this back in the air soon now that hurricane season is just about over.
 
This is my first experience with epoxy putty
and I have to say that stuff is a dream. Workable like clay and a wet finger is all it took to knead and smooth it.

Caution, I believe this is still an epoxy resin product, and nitrile not latex gloves are recommended to prevent an acquired allergy.
 
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Given this is a sports model, you may be okay without any airfoiling of the fins at all.

Only airfoiling the heli rotors. I'd already decided at the start of build not to airfoil the fins since I intended to attach the rotors
to them and didn't want to weaken them.
 
Only airfoiling the heli rotors. I'd already decided at the start of build not to airfoil the fins since I intended to attach the rotors
to them and didn't want to weaken them.

Carving airfoils is not one of my favorite pastimes, but I only did it here because it starts the model rotating immediately. This isn't the case when using the diagonal cut method or no airfoiling. Nothing happens for about 2 1/2 - 3 seconds so I just decided I wanted to give mine every opportunity for a softer landing after all it's been through.
 
Carving airfoils is not one of my favorite pastimes, but I only did it here because it starts the model rotating immediately. This isn't the case when using the diagonal cut method or no airfoiling. Nothing happens for about 2 1/2 - 3 seconds
I'm not disbelieving you but I have to say I'm surprised that airfoiling the rotors would have this (much of an) effect.
 
I'm not disbelieving you but I have to say I'm surprised that airfoiling the rotors would have this (much of an) effect.
Me too! I first noticed that unsettling (well, to me unsettling) tendency on the maiden flight of my Heli Roctor, which uses the diagonal cut technique to put a "twist" in the rotors instead of using an airfoil. I've since seen videos of other helicopters that exhibit the same "pause" when using diagonally cut rotors. Although I do kind of understand how the method works, I have no idea of the physics behind why it doesn't spin up instantly.
 
IMG_0249.jpg

Finished the repairs, including cosmetic stuff to hide the damage (lazy so I decided to use self-adhesive vinyl I
had to cover the patched areas). I couldn't resist taking it out for a trial run at a smallish park nearby. Not the
wisest thing considering how much trees seem to find it irresistably appetizing, but I got lucky on a C6-3 with no
wind and got a satifyingly straight boost and immediate spin up once the ejection charge went off. Couldn't
believe my luck when it landed just 50' from the launch pad without being snatched by any branches or a
passing eagle.


It had a real soft landing but the body tube did sustain more damage (it fractured along the spiral winding again)
and I can't blame it on tree branches this time. I'm wondering if it's from a too-short ejection delay? At 3.6oz
without the engine, could it be packing enough mass to possibly still be traveling upward at too fast a clip when
the ejection charge fires at the 3 second mark?
 
DOOD! That's a real bummer. Gotta say tho, I have never used any kind of hinge like that. Mainly because I know what works for me. And #2) I would never use CA glue for any major construction job. I didn't want to say anything back when you were "buttering the hinge" because I wasn't sure if you knew something I didn't. Anyhoo, I do have a suggestion for the refitting of the props. When I built my upscale Gyroc, I blew off using that flexible crap that came stock with the kits and opted for brass hinges. Brass? These are easy to find at Lowe's, they're really light weight, and epoxy sticks to them very well. In the pics below, I marked around the hinges, then made a cut deep enough to recess the hinge into the wood enough to be flush with the surface. I chiseled out the wood like you might to hinge a door on a frame, took some heavy grit sandpaper and roughed the bottom/glue side of the hinges. This is so when you apply EPOXY, it has that rough surface to stick to better. I then pushed more epoxy in the screw holes and enough to make a level surface on the fins. Gotta say, that Gyroc has seen a great many flights and those hinges are stuck very well. Used the same method for both my heli jobs. Epoxy is your friend!!!

View attachment 326568 View attachment 326569


Been meaning to ask you how you carved those reliefs so precisely and neatly?
 
Been meaning to ask you how you carved those reliefs so precisely and neatly?

Well, just like it says in my post. I cut about deep enough to get the hinge to inlay flush with the surface. They didn't for the most part so I modified an emery board (fingernail sanding stick) to have square edges and sanded the cuts deep enough for the fit I needed. Pretty easy really.
 
Well, just like it says in my post. I cut about deep enough to get the hinge to inlay flush with the surface. They didn't for the most part so I modified an emery board (fingernail sanding stick) to have square edges and sanded the cuts deep enough for the fit I needed. Pretty easy really.


My compliments, very precise and meticulous work there. (I thought maybe you might've used some sort of power balsa router that I'd never heard of or imagined).
 
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