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Mini moth experiment

#1
Hello,
This is the start of a project that I want to scale up and get electronics on eventually. I call it the moth. I designed the airframe and wings based on a picture of a moth. It is intended to be a fantasy(fun) build and an exercise in aerocrafting. I have just started the hobby and this is my second project. If anyone out there has suggestions or questions or just good old fashioned comments on the build feel free to ask. (Edit I forgot to mention I want the wings to be able to sweep mid flight when I get the electronics sorted out. For now the wings are manually adjustable.)

Thanks
-Cwildred
 

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BATTLEAXE

Well-known member
#3
Judging by your living room chuck glide test it has balance and some loft. Why do you want the wings to sweep? Do you plan on doing low and high speed with it?
 
#4
Judging by your living room chuck glide test it has balance and some loft. Why do you want the wings to sweep? Do you plan on doing low and high speed with it?
Yes that was my plan open wings for slow speed and back swept for high speed. Also because of the shape of the wings when its closed it looks and flys like a delta but when the wings open it kinda flys like a more traditional plane. Right now just chucking this little guy it flys great in both wing positions. One thing I noticed is it does a little bit of porpoising like a very shallow sine wave. Do you guys think it's a CG thing causing that? I agree with jfaleo1 scalding up is my next task and getting more control surfaces mapped out after that. I will keep you guys posted.
 

BATTLEAXE

Well-known member
#5
Absolutely it is a CG thing. a little more nose weight as a chuck glider or/also more thrust under power. Once it is powered a couple of degrees of down thrust would help that as well, which may give you the full spectrum of the wide speed envelope you are looking for. One servo with two arms could be all you need to get the wings to sweep mechanically as well, should be pretty simple to play with depending on how you set it up in programming.

I imagine you are going with a front motor mount tractor style configuration?
 

L Edge

Well-known member
#6
Yes that was my plan open wings for slow speed and back swept for high speed. Also because of the shape of the wings when its closed it looks and flys like a delta but when the wings open it kinda flys like a more traditional plane. Right now just chucking this little guy it flys great in both wing positions. One thing I noticed is it does a little bit of porpoising like a very shallow sine wave. Do you guys think it's a CG thing causing that? I agree with jfaleo1 scalding up is my next task and getting more control surfaces mapped out after that. I will keep you guys posted.
Were are you putting the control surfaces so they work in wings in/out and have the swing mechanism? It is basically a f14 aft swept wing thing. Nice concept.
 
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#7
Absolutely it is a CG thing. a little more nose weight as a chuck glider or/also more thrust under power. Once it is powered a couple of degrees of down thrust would help that as well, which may give you the full spectrum of the wide speed envelope you are looking for. One servo with two arms could be all you need to get the wings to sweep mechanically as well, should be pretty simple to play with depending on how you set it up in programming.

I imagine you are going with a front motor mount tractor style configuration?
I will try a little more nose weight to see if that stops the porpoising.

Front mounted motor for sure. I am not familiar with the "tractor style configuration" terminology.
 
#8
Were are you putting the control surfaces so they work in wings in/out and have the swing mechanism? It is basically a f14 aft swept wing thing. Nice concept.
My first idea is to put the rudder on the bottom behind the fuse and use the tail as elevons. So each side can move independently. If that is not so great I plan to try to put ailerons on the lower main wing. Any suggestions on this would be great.
 
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L Edge

Well-known member
#9
My first idea is to put the rudder on the bottom behind the fuse and use the tail as elevons. So each side can move independently. If that is not so great I plan to try to put ailerons on the lower main wing. Any suggestions on this would be great.
Rather than re-invent the wheel, go to RCGroups and seek out maybz tomcat build. There is how he did the swing wing and go for it, forgetting about the ailerons for now.

Go for it, it is unique!!!!

 
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BATTLEAXE

Well-known member
#10
My first idea is to put the rudder on the bottom behind the fuse and use the tail as elevons. So each side can move independently. If that is not so great I plan to try to put ailerons on the lower main wing. Any suggestions on this would be great.
The swing wing mechanism @L Edge posted is exactly what I was thinking of. Simple stuff. Tractor is front motor Mount meaning it pulls the plane, pusher is exactly what it implies, rear mount pushing the airframe.

As far as the rudder goes you can get away with a single rudder, top or bottom. Remember a bottom rudder will take abuse on landings. A top rudder if it has enough surface area is ideal for yaw stability, left to right. Another option you may want to go with would be 2 smaller rudders sitting parallel to each other at the back split between top and bottom. All you really need is enough surface area to stabilize and /or control yaw authority.

Take a look at other FT designs on the website or YouTube. Take a look at the Mini Arrow or other delta wings for inspiration. Most of the deltas use elevons as well and makes a little tricky to set up but are very successful flyers. Keep posting, this is interesting
 

L Edge

Well-known member
#11
You are going to have 2 problems to deal with as I see. One is the shifting CG and the second is the swing. You will have to solve the fluttering and bearing forces of the wing. Servos will strip if not using metal and must fight the forces due to rotation as well as bending. Ask me how I know. Only build it large enough to handle your present size equipment and swing mechanism.

That is the fun of designing. It's a blast when it works.
 
#12
Thanks for the suggestions guys. These sweep mechanisms are exactly what I had planned. I was thinking two rudders on the bottom coming off the fuse but top might be better. I will post more soon. I'm going to run down to dollar tree today for more foam board. I think the biggest I can scale my plans up right now is 140%. I need to learn how to draw up plans in pdf format. 🤷‍♂️

P.s. the f14 is my all time favorite fighter jet.
 
#13
You are going to have 2 problems to deal with as I see. One is the shifting CG and the second is the swing. You will have to solve the fluttering and bearing forces of the wing. Servos will strip if not using metal and must fight the forces due to rotation as well as bending. Ask me how I know.

That is the fun of designing. It's a blast when it works.
I do see the CG issue for sure being a real thing to consider. And I would love to hear about your experience with this type of thing L edge.
 

L Edge

Well-known member
#14
I do see the CG issue for sure being a real thing to consider. And I would love to hear about your experience with this type of thing L edge.
I also have the first ever morphing plane that is capable of starting the wing out perpendicular and go to an aft swing wing and then make it go to a forward swing wing in flight.

P1010037.JPG

P1010038.JPG

This is the next step and I wonder will it fly?

P1010035.JPG

Off the top of my head, I give yours a 50-50 chance as a concept. I will give my opinion if you ask me, otherwise the fun is letting you try and get it to go by you.

VTOL still has kicked my butt over and over, and it is a challange I still try off and on.

The last is an offset oblique and I don't even think NASA played with this one. Give it low odds.
 
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#16
I also have the first ever morphing plane that is capable of starting the wing out perpendicular and go to an aft swing wing and then make it go to a forward swing wing in flight.

View attachment 142281

View attachment 142282

This is the next step and I wonder will it fly?

View attachment 142283

Off the top of my head, I give it a 50-50 chance as a concept. I will give my opinion if you ask me, otherwise the fun is letting you try and get it to go by you.

VTOL still has kicked my butt over and over, and it is a challange I still try off and on.
Yes, yes, yes! That thing looks awesome what do you call it? I can see how you got some serious force to overcome to get your wings to sweep that far. That really has to mess with the CG too. I think it would fly with one wing out, I have seen some asymmetric designs fly that you wouldn't expect to fly. Crazy idea I had fir the moth was to have sweeping dihedral on the top wing for very stable slow flight. But I haven't seen any designs for that sort of mechanism. 🤔
 
#18
As far as swept wings and CG go, i have a question. Where does the CG end up with the wings forward as compared to swept back, does the CG move back as well?
So far on the moth it moves back a little but not very much at least in this small scale version. I will document it on the larger version in the pictures to follow. Im printing plans for a 150% scaled up version right now.
 
#20
Ok so here is the Mini Moth 2.0. It has been scaled up 150% and now has a bottom mounted vertical stabilizer. @BATTLEAXE the last picture shows how far back the CG moves when the wings sweep. More info coming soon.
 

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