Show us what you are working on..

[j ferguson]

Doc, This thing is trying to be a working replica of a SwitchBlacde300, semi-autonomous drone designed, manufactured, and marketed by AeroVronment in San Diego, folding wings, folding prop, ejected from a 3 1/2 inch diameter tube to fly off and give the Russians a hard time.

I was working on another long term project to develop a fullhy autonomous fixed wing aircraft of about 3 pounds, but this came up and it looked like fun. But it has taken two years to get to where I am. It hasn't helped to have no idea what I'm doing.

Let me know if this could use a more detailed explanation.

 

[j ferguson]

Doc, I should add that wingspan is 775MM. This is as close as i cold get to Switchblade 300 without AeroVironment's drawings. I think I forgot to mention that the plane above has zero angle of incidence. My guess is it will need a couple of degrees, but I want to see what happens when we try to fly it. I did a more conventional tractor fixed wing a couple of years ago with a Gottingen 418 airfoil which is a bit fat. It flew best with no angle of incidence. On this plane it's a little hard to get used to idea of two lifting surfaces with the control surfaces in front, but i guess I'll find out.

I use OnShape for all of the stl design, and Creo for the landing gear jig. I've been using AutoCad since 1984 - for architecture then, ProE since 1988. I can model faster in OnShape and producing drawings seems faster in OnShape but OnShape Drawings aren't parametric. Creo's are if you do them right, but that takes time.

If I knew of a good CNC interface for OnShape I'd switch engtirely to it, but since I do need the CNC functions for my mills, I need Creo.
I have a CNC 6040 router which I love. I use SheetCam for the 2 1/2 D stuff like ribs and bulkheads for balsa planes. I made a needle foam cutter attachment which clamps to the spindle and which cuts foamboard astonishingl fast.

I did use OnShape to calculate weight and CG, but I think my input assumptions about the weight of parts of the plane were too sloppy. I'd expected to need a whole lot of weight in front, but now it doesn't look so bad. I'm also assuming that I'm going to get lift from the elvons.

John

 

[Doc J]

Doc, I should add that wingspan is 775MM. This is as close as i cold get to Switchblade 300 without AeroVironment's drawings. I think I forgot to mention that the plane above has zero angle of incidence. My guess is it will need a couple of degrees, but I want to see what happens when we try to fly it. I did a more conventional tractor fixed wing a couple of years ago with a Gottingen 418 airfoil which is a bit fat. It flew best with no angle of incidence. On this plane it's a little hard to get used to idea of two lifting surfaces with the control surfaces in front, but i guess I'll find out.

I use OnShape for all of the stl design, and Creo for the landing gear jig. I've been using AutoCad since 1984 - for architecture then, ProE since 1988. I can model faster in OnShape and producing drawings seems faster in OnShape but OnShape Drawings aren't parametric. Creo's are if you do them right, but that takes time.

If I knew of a good CNC interface for OnShape I'd switch engtirely to it, but since I do need the CNC functions for my mills, I need Creo.
I have a CNC 6040 router which I love. I use SheetCam for the 2 1/2 D stuff like ribs and bulkheads for balsa planes. I made a needle foam cutter attachment which clamps to the spindle and which cuts foamboard astonishingl fast.

I did use OnShape to calculate weight and CG, but I think my input assumptions about the weight of parts of the plane were too sloppy. I'd expected to need a whole lot of weight in front, but now it doesn't look so bad. I'm also assuming that I'm going to get lift from the elvons.

John

Thanks a lot for the details, John. It all makes sense now - pretty much what I guessed in fact.

I'd try to fly the plane with zero-zero first - except if its a very undercambered section(s)

Maybe you could be a sub-sub contractor and knock out more drones to give more Russians, more trouble!

Actually I have always got along in the international championships very well with the Ivans, but its thier leaders that are the worst.

Thanks again,

Doc.

 

[j ferguson]

I needed a thin airfoil, less than 10%. I ended up with a NACA 2408 which gives me 5.6MM with 66MM chord. With some down elevon, this airfoil looks undercambered if I understand the term. I suspect that I may wind up with some AOI on the aft wing but not the forewing.
I don't think this can fly slowly. I bought a stabilized receiver from Aloft and I thnk I may start out with the stabilization. Last time I was flying regularly, I put an S6R in my Pandora, callibrated it, and flew it fro a minute or two with the stabilization on. it worked but I didn't really want it.

 

[j ferguson]

Here,

scratchbuild your own Switchblade 300 ? - RC Groups

Discussion scratchbuild your own Switchblade 300 ? Electric Plane Talk

www.rcgroups.com

is the history of this thing.

 

[jure]

Here,

scratchbuild your own Switchblade 300 ? - RC Groups

Discussion scratchbuild your own Switchblade 300 ? Electric Plane Talk

www.rcgroups.com

is the history of this thing.

John,

you may notice from the RCG thread that I was a follower from the very early beginnings.
I would like to make a suggestion.

In order to expedite the design and test of the device, you could first try a test model with the proper geometries , planforms , airfoils, etc , but in a non-folding configuration.
Even a simple chuck glider , where a power plant may be added later.

With this first dummy, you could test the CG , controls , stabilization , power system (motor, prop, battery), and payload limit.
This will get you something in the air much quicker, and you may add afterwards all the other features needed to mimic the original Switchblade concept.

Jure

 

[j ferguson]

Hi Jure,

I can remember your excellent suggestions. I started out based on your earlier suggestion to build a foamboard "mule"

Probably because of an almopst complete inability tto do anything simple, this led to a couple of months designing and building a foamboard needle-cutter attachment for my CNC router, the vacuum table to hold the foam-board while the needle cutter cut out all the parts, the autocad designs for each of the parts of the plane, then the generation of G-Code from dxf files to cut the parts, then doing it, assembling the foamboard plane reinforced with balsa etc. etc. I didn't like what I'd done. Modifying the AutoCAD files took too long, and I was going nuts. As I said in the R/C group thread, I experimented with a couple of things I needed to design and thought would be difficult, I was thinking that if I couldn't solve them, this project would turn out to be a waste of time.

The wing pivots were a real challenge, but I wound up with something simple and possibly simpler than what AeroVironment did. There was also the issue of how to seize and control the elevons and rudders. I did it with servo driven pushrods with neodymium magnets on both the ends of the pushrods and the control surfaces. I think this is how AeroVironment did their rudders and I think their current SB300's have this design although Red tells us that they found they didn't need operable rudders after all, but the mechanism was still on the wrecks I have photos of.

And of course all this led to designing the ultimate bird. So Jure, you can see I've been at this almost two years and am now very close to flight - maybe in a few weeks. I have two serious 3D printers so I can make replacement parts quickly (well overnight at worst). My Aloft and Motion RC orders should show today so I can get going with mounting the servos and programming the receiver. I'm redesigning the steering to make it easier to adjust, and depending on where the CG can be located by moving the battery, I may want to print the rudders with PETG instead of Polu-Light which does not produce nice results for those particular parts. It doesn't weigh as much as I expected but then the aft wings really do have to lift not to need to depend on the forward wings for most of the wing-loading. I hope it doesn't need 60 mph to fly, but I guess I'll find out. Our flying field has a pnd at one end of the runway and a super-highway at the other which is not too comforting if it takes a lot of runway to horse this thing into the air.

So even though the bird is equipped with all of the features needed to tube launch and unfold the control surfaces, spin up the prop and fly off under some type of RC control, I'm doing elevon control with a simple scheme which won't work if the wings unfold but the pivot system is there in the 3D prints but I didn't put in the springs.

If anyone thinks all of this is too blabby, let me know and all try to hold it down a bit more.

John

 

[j ferguson]

Thats pond on one end of runway and superhighway on the other. If you don't know how to turn or the bird doesn't want to, things will not go well.

 

[Jarron]

oh well, shit happens...
@Jarron , in case you want to come and visit us in Walnut Creek, I have a few replacement planes for you , for free.

Bring them to Sunset XD

 

[Jarron]

@Jarron might remember this one.

oooo, how it is treating you?

 

[rcsoar4fun]

oooo, how it is treating you?

Flew just fine. Need to work through some double centering on the elevator before the next outing.

 

[jure]

here is the maiden flight of the NSB : the No-Switch_blade , inspired by the work of John Ferguson

The wings and tail fins are fixed to the fuselage.
KFm airfoils. Control surfaces : aileron and elevator, i.e. two servos only.
incidences are 0-0-0 .
Fixed (not-folding) propeller, APC 9"x6"
Motor: RC Timer 2836/7 , Kv=1120 RPM/V , 70g
3S LiPo 1200 mAh battery
AUW 580g

 

[Wayne]

Well, what did you learn?

Did your first CG location work?

Looks sort of cute in the air.

 

[jure]

Well, what did you learn?

Did your first CG location work?

Looks sort of cute in the air.

Learned that it is very stable even without dihedral , incidences 0-0-0 . No stabilizer needed, flew it with a simple minded 4 channel FrSky RX.

CG location at the trailing edge of the fore wing is very good.

Ailerons and elevator had too much authority , could be dialed down.

And again, pushers are noisy !

PS: it has potential for the slope, removing the motor and the relatively heavy 3S battery, it could get into the 250g AUW realm ( about 4.8 oz/sqft ).

 

[Wayne]

Yeah, that prop is in dirty air for sure. Sort of surprised the CG is that far back, but guess that rear surface is cambered too. Fun project.

 

[purview]

today the servo setup on my EDF Hawk went from rear mount to the next step — "figure out how to mount all up in the front" or somewhere in the middle.... I lost aprox60gram on the tail, the ducted fan and ESC is also rear mounted and the front retract should give matter a choice...butter to put all the electronics out and check the margin of beeing in balance right.

 

[purview]

penalty of 360g on the EDF unit. Sloping feels like heaven... definitely'll keep the flaps to see how camber handles the drag/lift penalty on this ship

 

[jure]

today the servo setup on my EDF Hawk went from rear mount to the next step —...t.

are you converting it into a sloper ship ?

 

[purview]

are you converting it into a sloper ship ?

yep, I have some very capable slopes... why not to try out?

 

[Wayne]

Should be fun.. Remember on the slopes, weight is your friend. That ducted fan will have a huge drag penalty already.