Vortex – helicopter scratch build

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
I've been doing some shaping of 1/8" basswood fins lately. Differences I have discovered, relative to balsa:

1) You can go one grade coarser than 220 grit to do initial rough shaping. I have been staying with 220 though, because by working slowly I'm less likely to oversand anything. I seldom go coarser than 400 with balsa, unless it's very hard.
2) You don't have to handle the wood pieces like Faberge eggs. Almost every time I handle balsa fins I put an inadvertent fingernail mark or some other ding in the wood. Even while applying significant force with 220 grit to shape it, I find I don't need to worry too much about dinging the basswood. That is *very* nice.
3) As an addendum to #2, it seems like it'll hold a fairly sharp edge with no problem. I might harden the edges with CA at the end, but honestly it seems like it will only matter for fin edges that are likely to absorb landing impact.
4) Indeed it sands very smooth. In my correspondence with John Pursely, he has stressed that basswood sands best with the grain. I've been doing a round of 400 grit and then 800 and end up with a pretty smooth piece of wood.

Overall I've enjoyed working with it a lot. Might use it more in the future. I think 3/32" would be my preference, but that is less easy to find locally (I think Hobby Lobby has it).

I like basswood and reserve it for special uses where strength is a consideration (glider fuselages and wing leading edges, rotor stops, etc.). You're right that basswood won't crush like balsa. Just a little too much of a squeeze and balsa smushes. (I'm notorious for doing that to nose cones. Fortunately I've discovered that with the small dings/dents, a tiny bit of water applied to it will pop it back out as it absorbs the moisture). Also balsa is very much affected by humidity where basswood isn't. Balsa seems to be a moisture sponge and it plays havoc with gliders after you've tediously trimmed one and you suddenly have a really humid day.

The only reason I made these replacement rotors out of basswood was because I was upset after the balsa version snapped and it took me forever to get the broken one unglued from its hinge. I think basswood is about 20 - 30% heavier than balsa but since my main concern is longevity and not altitude or duration like in a competition model, it's not much of a concern.
 
You know, you could add your "more specific" location to your profile location. :wink: I think it's nice to see where the people you're interacting with are located. It helps to find other rocketeers local to you. So far, I haven't found anybody close to me. :(

Good idea. I'm still getting familiar with learning the ins and outs of the forum. Can't make it jump through hoops yet but I'm getting there.
 
Wish I could find some enthusiasts that lived over here in the central part of the state. Would be nice to get together for some informal launches or even meetings without having to travel a couple hundred miles.
I AM central state. Bout as central as you can get. But I don't have anywhere to launch. That's why I hit the sod fields in SC where the clubs go.
 
Petroleum gel good idea. You can also with some hinges simply take the metal peg out, glue on the hinge, and put it back when glue dry.

Sewing in good idea, but kevlar is overkill. Cotton thread (I use dental floss, partly because it comes with it's own cutter!) with a mid size needle can easily sew by hand throught the hinge and through the balsa (make starter holes with the needle from the plastic hinge side so you can find your way "back" from the other side.) Wick in some thin CA. Presto, hinge attached and balsa will break before hinge comes off.

Hmm, you are using basswood. May make it harder to get needle through by hand. Still easily do-able.

2 options:

1

Put hinge where you want it. Use mechanical pencil or sharp pencil to mark where the holes are.

Use 1/16" drill bit to make the holes.

Sew in place.

2. Glue hinge in place. Use 1/16 drill bit to drill through the plastic holes through the wood.

Sew in place.


either way, the additional strength places in the hinge attachment is huge, at a negligible cost in weight.

Thanks for the tips, already punched the mounting holes and filled with CA last night. I intend to use your technique
on my next heli roc build (your Whopper Flopper Chopper actually). I already have the 1/4" balsa. I was considering
using a modified rotor retention system released by a tethered engine-eject system instead of a burn string though.
All in my head at the moment and just waiting on a mock up to confirm the details.
 
I AM central state. Bout as central as you can get. But I don't have anywhere to launch. That's why I hit the sod fields in SC where the clubs go.


Too bad Star Trek transporters aren't here yet. Then it wouldn't matter, we could just beam over anytime to one of those big venues in Neveda, Texas, Colorado, southern Cal or even the Barboro one on the coast here.
 
Aaghhh! Okay I rushed things and didn't take into account that sketches are 1-dimensional and the real world has an X, Y, & Z axis.

I'm not above admitting a goof. I didn't take into account that the balsa is 1/8" thick so that when you sand off a bit of it to bevel it, it throws the overall dimensions off--just a hair, but enough so that now it won't fit around my BT-50 body tube. :facepalm:


View attachment 323455

If it's true that we learn the most from our mistakes, than I'll never make this one again. Lesson hard learned. Now that age-old carpenter's rule "measure twice, cut once" keeps nagging inside my head. I only built kits as a kid so I'm chalking this one up to a newbie designer's inexperience.

Time to redraw my template and break out the hobby knife...

Sorry came in late on this.
What's your engine size? If this is a D, you are minimum diameter and you have to adjust accordingly.

If you are going with an 18 mm.....
If you will have an engine mount inside this, nothing wrong with letting the BT-50 deform a bit (will make it a bit triangular) and go ahead and insert it into your fin unit. Before you do, however, place your forward engine mount centering ring in place (I am guessing will go forward of the fins.) Then when you put the rest of the mount in, the rest of the mount will be the engine tube and the rear centering ring.
You may have to sand 3 sides of the rear centering ring, but you should be able to get it in and straight.
 
Sorry came in late on this.
What's your engine size? If this is a D, you are minimum diameter and you have to adjust accordingly.

If you are going with an 18 mm.....
If you will have an engine mount inside this, nothing wrong with letting the BT-50 deform a bit (will make it a bit triangular) and go ahead and insert it into your fin unit. Before you do, however, place your forward engine mount centering ring in place (I am guessing will go forward of the fins.) Then when you put the rest of the mount in, the rest of the mount will be the engine tube and the rear centering ring.
You may have to sand 3 sides of the rear centering ring, but you should be able to get it in and straight.


That's a pretty neat fix that I didn't consider. I already went ahead and fabricated another larger fin unit, one that snugs in nicely. Appreciate the feedback though.
 
IMG_9990-Fins.jpg

Finally found time to get my fin units attached. Once the rear elastic hooks were in,
it made for a really tight fit. (As you can tell from the scratched up and dinged rear
of the tube). A little bit of CA and paint should remedy that, though it’ll slow things
down a bit, and it irritates that perfectionist gene in me that now it’s not flawless.

IMG_9989-Fins-closeup.jpg

The harder part was trying to get fillets in between the fin unit and body tube. It's
nearly impossible because of the tight space, though I did try using a thin dowel.
I finally gave up because I reasoned that I used a lot of Titebond Quick & Thick to glue
the two together (and yes I taped off the body tube before painting and sanded the area
to be joined to ensure a good bond). Besides the fit is so tight, that fin unit isn't going anywhere.
 
balsa fillets might work here.

Thin strip of 1/8 or 1/16 inch balsa (if 1/8, then 1/8 x 1/8 x fin length)
Put some glue along the edge.
press it into the "valley" between the tube and the fin. Kind of like where you would put a launch lug.

BTW, one of these valleys might be a good place to PUT your launch lug, if it won't interfere with placement of your rotors. Should guarantee a straight position of the LUG and add to the strength of the joint.

works well any time you have a tube to "flat side" of a fin or wing joint.
 
balsa fillets might work here.

Thin strip of 1/8 or 1/16 inch balsa (if 1/8, then 1/8 x 1/8 x fin length)
Put some glue along the edge.
press it into the "valley" between the tube and the fin. Kind of like where you would put a launch lug.

BTW, one of these valleys might be a good place to PUT your launch lug, if it won't interfere with placement of your rotors. Should guarantee a straight position of the LUG and add to the strength of the joint.

works well any time you have a tube to "flat side" of a fin or wing joint.


Thanks, that idea of situating the lug down in a corner of the fin unit solves a tiny problem: I forgot to glue it on the larger upper tube before painting it.
Now it'll be hidden and no sanding off the paint to install the lug where I originally intended to put it.
 
BTW, one of these valleys might be a good place to PUT your launch lug, if it won't interfere with placement of your rotors. Should guarantee a straight position of the LUG and add to the strength of the joint.

On second thought I'll do both. The launch rod will be right up against the side of the larger upper tube and the paint job came out so purty this time, I don't want to mess it up by having the rod leave abrasions from launches (ok I admit it's that "first nick in my new car's paint" syndrome) so a short 1" piece of lug will go on the upper tube as well.
 
Back on track after several days of other chores that needed attention. Have to play a bit of catch up on my build.
Rotor stops are next on the agenda. I prefer tracing a pattern from the inside vs tracing around one. Much easier in my opinion.

IMG_9991-rotor stop template.jpg


I cut 4 out then gang sanded everything, selecting the best 3 out of the bunch, then soaked them in CA to harden them up.
This is where a kicker to instantly set the CA really comes in handy.

IMG_9992-rotor hardening.jpg


While those are marinating, I’m going to move on to the rotor hooks that anchor the elastic bands. Since they’re made from
paper clips, I had to fashion a “drill bit” tool from another sharpened paper clip and bore a hole through the basswood rotor
by hand. (Normally a balsa rotor is soft enough to just push the hook through).

IMG_9994-drilling hook holes-2.jpg


That proper sized hole made for a nice clean snug fit.

IMG_9998a-hook installation.jpg



Maybe a bit of overkill but I’ve heard some guys will perf small holes in the root edge of critical components where
it’ll be glued to something else. Since I consider this rotor stop pretty much a critical component that’ll take quite a bit of a stress beating,
I did the pinhole thing to ensure the glue really has something to grab and anchor itself to.

IMG_9998b-rotor stop perfed.jpg


Rotor stop installed using the double glue method for extra insurance. Some filleting and they’ll be ready to go.

IMG_9999-rotor stop installed.jpg
 
I'd be a little weary of using paperclips for your elastic hooks. Most paperclips are not hardened and will break pretty effortlessly, especially after being bent.
 
I'd be a little weary of using paperclips for your elastic hooks. Most paperclips are not hardened and will break pretty effortlessly, especially after being bent.

Yeah, I was looking at that also. Had me thinking about when I came across these T Pins you can get in about any fabric department.

T Pins.jpg
 
I'd be a little weary of using paperclips for your elastic hooks. Most paperclips are not hardened and will break pretty effortlessly, especially after being bent.

Thanks, I'll keep that in mind. I've been meaning to pick up some piano wire but since I have a ton of paper clips filling up my drawers I thought I'd put them to good use. I guess it's time to switch, since I've been thinking of winding some simple springs from piano wire...something you can't do with paper clips.
 
Yeah, I was looking at that also. Had me thinking about when I came across these T Pins you can get in about any fabric department.

View attachment 324371


They're pretty handy. I used T pins as rotor hold downs on my previous heli roc (the one in my icon pic). Pretty useful to drill small holes in stuff when your dremel chuck won't fit really tiny drill bits.
 
IMG_10028_pre.jpg

Couldn’t resist seeing both halves together before the rotors go on. Too bad that roll pattern is only visible when the rotors are open. Doesn’t matter, I got a lot of useful practice on prepping, painting and finishing from the experience.
 
Took the suggestion by BABAR to reinforce the body tube/fin unit joint with thin balsa strips.
The extra insurance couldn't hurt, and it only took me a couple of minutes to slice up some
scrap and glue it inside like a fillet.

IMG_99930-joint reinforcement.jpg


 
Thanks, I'll keep that in mind. I've been meaning to pick up some piano wire but since I have a ton of paper clips filling up my drawers I thought I'd put them to good use. I guess it's time to switch, since I've been thinking of winding some simple springs from piano wire...something you can't do with paper clips.
Believe it or not, you can do great with used solar igniters. You just need to wrap them around something or they pull through the balsa. Crimp the around your band or string and they will not accidentally release.
 
They're pretty handy. I used T pins as rotor hold downs on my previous heli roc (the one in my icon pic). Pretty useful to drill small holes in stuff when your dremel chuck won't fit really tiny drill bits.

I like these!
 
Believe it or not, you can do great with used solar igniters. You just need to wrap them around something or they pull through the balsa. Crimp the around your band or string and they will not accidentally release.

Showing my ignorance here but until you mentioned it, I'd never heard of solar igniters. Are these the circular mirror like things with a coiled wire at the apex that campers use?
 
This is always the part that makes me the most nervous because if anything can go wrong,
this is where it’ll happen. And if it does there’s no really fast easy fix.

IMG_99934-rotor install.jpg



Being hyper cautious didn’t hurt because things went smoother than I was prepared for (I admit I had
the bottle of acetone and paper towels on standby just in case a hinge seized up or whatever).
Had to lightly run an emery board over the stop ends. The hinge is about 1/64” thick so
that balsa dust is from “adjusting” the rotor stops to maintain that 8° dihedral.

IMG_99936-rotor install2.jpg



In order to reinforce the hinge joint I’m putting in a hinge surround of 1/64” birch ply.
I’ll fill the recess with more CA then put on a ply “cover plate” to seal the hinge in. I may have to
do a fine tune of the rotor stops by sanding off a tiny bit of material again because the thin pieces of ply
do raise the surface slightly.
Glad I’m documenting this so I can make adjustments in my measurements/templates for any future do-overs or versions based on this.

IMG_99939-hinge surround.jpg



Got the hinge cover plates on at the end of the day. Just needs a fillet and I think I’m close to done.
The fin units are too hard to paint so I may just put on a couple of coats of dope and leave it at that.

IMG_99943-hinge cover plate.jpg
 
IMG_99969-fini1.jpg

Glad I did some careful measuring. The upper body tube is a perfect slide-on fit and captures the rotor tips firmly without binding.
It’s weighing in at 3.0 oz without an engine, not too bad considering it’s a 24” tall rocket with a ton of sealer, primer and paint on it.
The “cutout silhouette” method seems to indicate it’s stable but I don’t think it takes into account the weight of the engine?
I may slip in a tiny bit of lead sinker weight in the nose. I think it's time I teach myself how to use OpenRocket.


IMG_99957-fini2.jpg

Not sure if I’ll add any color to the fin units. I was thinking of maybe using self-adhesive vinyl to cover it with black and white
if I can figure out how to get it under or around those elastic hooks and hold down plate. Or maybe I’ll just stop tinkering with it.

Hindsight being the wonderful thing it is, now I wish I’d built this to take a 24mm engine, or at least with a swappable mount so
I could use either 18mm or 24mm.

Guess all that’s left is a test flight.
 
What is the total weight w/o a motor? I'm guessing you prolly won't miss the 24mm option. When I fly mine, I like to be able to see it whirly it's way down. It it goes really high, you might not be able to see it very well, and there's the drift factor. Low to medium flights are perfect. For my small chopper I've been using B4-2's with great success. C6 might do well but it could be a bit much for this little guy. The big chopper is rigged for 24mm but a D motor doesn't quite cut it. It flies and looks best at about 500 ft so I've been sticking with F30's.
 
What is the total weight w/o a motor? I'm guessing you prolly won't miss the 24mm option. When I fly mine, I like to be able to see it whirly it's way down. It it goes really high, you might not be able to see it very well, and there's the drift factor. Low to medium flights are perfect. For my small chopper I've been using B4-2's with great success. C6 might do well but it could be a bit much for this little guy. The big chopper is rigged for 24mm but a D motor doesn't quite cut it. It flies and looks best at about 500 ft so I've been sticking with F30's.


This one is 3.0 oz without the engine.

I test flew my smaller first heli at a medium size park in Raleigh and kept it to a B6-2 engine to keep it from drifting away. I flew it at the bigger Midland venue on a C6-3 and really had a hike to retrieve it. Guess with this newest one I was maybe regretting not having the option to fly it at a much bigger field like the NC Rocketry venue in Bayboro or the Camden grass farm in SC.

You're right though, I'd hate to lose this latest build by sending it too high and having it catch a breeze or thermal.

 
IMG_0203.JPG
Showing my ignorance here but until you mentioned it, I'd never heard of solar igniters. Are these the circular mirror like things with a coiled wire at the apex that campers use?

Same as the ones that come in with the Estes engines. I don't want to do any more hijacking of your thread than I probably have already done, so I will use these in an upcoming thread if my own.

VORTEX is looking great. At three ounces without engine, trust Gary, you won't need a 24mm mount, at least not if you want to see it again. B4-2 sounds about right for first flight.

Hoping we see a video soon!
 
Last edited:
View attachment 324709

Same as the ones that come in with the Estes engines. I don't want to do any more hijacking of your thread than I probably have already done, so I will use these in an upcoming thread if my own.

VORTEX is looking great. At three ounces without engine, trust Gary, you won't need a 24mm mount, at least not if you want to see it again. B4-2 sounds about right for first flight.

Hoping we see a video soon!


Can you tag me when you do that post about the igniter wire? (Or is there a way I can set up an automatic flag for that? Seems there are ways to do things on the Forum that aren't always in the "How to Use" section).

My camera sucks when it comes to taking videos of anything moving. Maybe I'll have to stand several hundred feet away so I can visually track it better to aim the camera in the right direction at least. I'm hoping to get over to the medium sized park I use for test flights maybe next weekend, and fingers crossed I'll be able to grab some decent footage this time.
 
Back
Top