Simple slender delta

[Vimana89]

If I can get my nutball to fly and clean up my building just a bit, and I end up doing this build, I've decided for sure on a ducted fan. No props to break in a crash or cut your hand in an accident, not to mention all the other benefits. Looking into some fairly inexpensive 50mm EDF's.

 

[Vimana89]

A couple of options for 50mm ducted fans complete with motor and soldered wires for low prices

Anyone have any experience with either of these, or can recommend an even better option in the $30-$50 price range, preferably already soldered? I'm looking for a 50mm or perhaps smaller fan to draw up this build around. Also, these are both made for 3s. What do differences in KV mean for a motor on a fan the same size that runs off the same size battery? Is higher KV more thrust? I'll be looking more into these things myself, but if somebody could give a nice basic explanation of how that works and what type of EDF in my size and price range would be best for my build, that would be great.

To be true to my title, I'm going to keep this build as cheap and simple as possible while still being clean and functional. No super expensive motors, most likely no rudder(yank and bank), no fancy f-16 fuselage, no dihedrals or anhedrals. That being said, this won't be a mad max flying wing like my nutball with all the wiring all out in the open. This will have a full length fuselage that is 4 sided and at least mostly enclosed, except for the intake windows for my fan, and perhaps the spot for the battery. If I can get my nutball flying well, I'll feel good about starting this build right after, and can justify ordering parts. I'll take everything I learned about building with the nutball and clean it up, do it nicer and more precise, with more attention to detail.

 

[Vimana89]

In the mean time between tweaking my nutball and running out of/ordering props, I'm going to start serious work on this design. I have decided to scale around a 50mm EDF, though not sure on the exact one I want. There are two main variables that I need help deciding on. One is that this will be a three channel plane, using my crappy hobby king transmitter with no servo mixing and sensitivity adjusting. I'm wondering if I will be better able to fly this plane better using two elevons(yank and bank), or if I should configure it like the nutball, with a single elevator and a rudder.

The second concern is, and I can post rough sketches if it will help, I am deciding wether to terminate my fuselage before the vertical stabilizer and place the back end with the EDF in front of my stabilizer and elevons, so it blows back over my control surfaces(will this give me better control through partial thrust vectoring?), or to make the fuselage full length and have the edf thrusting at the very back, not over the control surfaces?(I know this way works it is how the real jets do it, but reaction driven aircraft probably have concerns about the exhaust going directly over the control surfaces that I don't have to worry about with a simple EDF).

Thanks in advance, to anyone who helps. Once I answer these two questions and choose a motor/EDF the rest of design will fall together, because I've got it all pretty much laid out aside from those variables. If I build this and get it to fly successfully, I'll do my best to develop it into and exact plan with all the specs laid out, so others can mess around with it too!

 

[Vimana89]

Rough sketches showing what I mean by placement of the edf and termination of the fuselage.

 

[Vimana89]

I've done a bit of research and answered a couple of my own questions. It seems the plane will be easiest to control as a 3ch build using tank and bank rather than a rudder. Looking at most rc designs using ducted fans, it does not seem particularly important or beneficial to have the control surfaces aft of the fan. Some designs do, but most don't, so I'll be sticking with variation "A". I have not chosen a particular edf but I've decided for sure to use a 50mm diameter. I'll begin scaling around that factor, as my fuselage will probably have to be about 60mm wide to accommodate that.

 

[Vimana89]

Semi-finalized top sketch with approximate build parameters. Slimming the fuselage-only the back needs to be wide enough to accommodate my edf, the rest only needs to accommodate the width of my battery(otherwise it would look a lot like the space shuttle!). Will put intake cuts around the back in front of the edf,exact size and placement not finalized.

 

[Vimana89]

Ok so I'm actually going to be running a 64mm edf, I have a foam board cutout of my wing and it's 280mm at its widest and 600mm long. Is that too much fan and not enough plane? Could I build around that or do I need a larger wing and air frame? Most planes that use a 64mm fan have about a 700mm wingspan. Mine can't because I'm going for a low aspect ratio, but should it at least be scaled up to 700 or 800 mm long with the same length to width ratio? Or can I make that 64mm fan work on the smaller setup?

 

[Vimana89]

Decided to scale up quite a bit. I think about a 400mm wingspan at widest point and 900mm length should be sufficient with the 64mm EDF. If not I could go a bit larger.

 

[Vimana89]

Electronics should be here for this build by Friday. I'll be using the viggen as a rough size reference, though my plane's wing is a good bit more slender in proportion to its length.I'll also be using the viggen tutorial vid as a rough guide on how to go about mounting my EDF unit and whatnot.

 

[BS projects inc.]

Sounds like a plan! Good luck with this one.

 

[Vimana89]

I'll need all the luck I can get, and patience. Getting new blades for my exacto knife, hope I can bevel the elevons right this time without messing up. If not, I'll have to sand again, albeit more cleanly than on my nutball. I'm going to make this as clean as possible but as basic as possible, no fancy cuts or engineering feats, as few separate parts as possible, as little "through-wiring" as I can get away with.

 

[Vimana89]

Learned up on thrust tubes today, and about the length and diameter of the exit that would be ideal. Will most likely be be rolling mine out of a sheet of soft craft foam and reinforcing with duct tape, will be easy to work with and allow me to get it just how I want it.

 

[jfaleo1]

The 3s Dr. Mad Thrust fan you show is not as powerful as I hoped. I have two of the 4s version on the quintet and they are not bad, but the 3s would not do the job. If you use that one say LIGHT as possible. I am still going to use the two 3s fans I have on a lightweight project in the future since the quality is not bad, just lower power.

 

[Vimana89]

The 3s Dr. Mad Thrust fan you show is not as powerful as I hoped. I have two of the 4s version on the quintet and they are not bad, but the 3s would not do the job. If you use that one say LIGHT as possible. I am still going to use the two 3s fans I have on a lightweight project in the future since the quality is not bad, just lower power.

Found a nice FMS 64mm 3s. Will be running this rather than the madthrust

 

[jfaleo1]

That is pretty much my final plan as well. Good Luck on this project!

 

[Dr. Looping Looie]

I have the FMS 50mm and it has plenty of power. Make sure your model is not too big or use a 4s battery with high C rating. For comparison: I have it in my FT Viggen on 4s 2200. Its not too fast but can do vertical. And it gets 5 min of flight time.
My recommendation: use smaller 4s batteries, 1600-2200 mAh with high C rating and experiment with your thrust tube. The smaller the exit, the faster the air, but fewer power.

 

[Vimana89]

New build parameters. Still working the finer points like the size and shape of the vertical stabilizer. Running a high c 3s setup going light and small.

 

[Vimana89]

May add low profile landing gear, may not. Any suggestions on a cheap set that would fit, or should I just go without? I think there might be some sort of park where people fly downtown but it's mostly desert gravel where I live.

 

[DamoRC]

May add low profile landing gear, may not. Any suggestions on a cheap set that would fit, or should I just go without? I think there might be some sort of park where people fly downtown but it's mostly desert gravel where I live.

Landing gear + desert gravel = broken landing gear (probably).

A couple of things to think about.
You have the forward fuse section marked as 40 x 40 mm (~1.6 inches) - just make sure you can easily fit your battery, esc, and Rx into this space including whatever you intend to hold the battery down with (for example velcro on the battery that sticks to velcro on the floor of the battery bay can add 1/8 to 1/4 inch to the height of the battery). Also remember that the foamboard is 4-5mm thick so your internal space will be 30mm wide.

You might also think about the weight of the EDF, battery, and ESC to confirm that you can position them in the plane in such a way as to get proper balance at the CG. At the moment, looks like you have plenty of room to move the EDF back if you need to. Worth trying a couple of online CG calculators to see approximately where your balance point needs to be.

On the thrust tube, I would recommend not going to tight on the exhaust initially, maybe 90% fan swept area (FSA). For a new design - you don't want to be caught short on static thrust for launch and initial flights.

DamoRC

 

[Vimana89]

Landing gear + desert gravel = broken landing gear (probably).

A couple of things to think about.
You have the forward fuse section marked as 40 x 40 mm (~1.6 inches) - just make sure you can easily fit your battery, esc, and Rx into this space including whatever you intend to hold the battery down with (for example velcro on the battery that sticks to velcro on the floor of the battery bay can add 1/8 to 1/4 inch to the height of the battery). Also remember that the foamboard is 4-5mm thick so your internal space will be 30mm wide.

You might also think about the weight of the EDF, battery, and ESC to confirm that you can position them in the plane in such a way as to get proper balance at the CG. At the moment, looks like you have plenty of room to move the EDF back if you need to. Worth trying a couple of online CG calculators to see approximately where your balance point needs to be.

On the thrust tube, I would recommend not going to tight on the exhaust initially, maybe 90% fan swept area (FSA). For a new design - you don't want to be caught short on static thrust for launch and initial flights.

DamoRC

The parameters are a bit flexible still, to account for the type things you said. My electronics will be here tomorrow, and I'm a hands on kind of guy, even though I know the basic sizes of them, seeing them in real time hands on will allow me to fine tune everything. I was thinking the exact same thing about the tube, I want to go more for better static thrust so I was thinking only like a 5-8% reduction in diameter at the exit.