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Dec 10, 2019, 08:32 AM
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Drone pilot looking to build micro delta wing ;)


Good morning! My question is in paragraph two if you wish to skip the background info Iíve been a drone pilot for about 3 years and love it but recently Iíve been wanting to try fixed wing. Iím really interested in it most because of the scratch building aspect with foam. I built an ft mini scout and our maiden wasnít so great. It flew amazingly until I got my thumbs confused and after that it wasnít right because I knocked the offset out of the motor pod. Since then Iíve begun repairing it, and also downloaded plans for Magnum Reloaded. I decided to try a sim before I tortured more parts and found picasim. I wasnít able to find rc desk pilot because the site kept living me an error. Iíd still like to get it and fly all the ft planes. I noticed I was much more comfortable flying the wing with elevons vs the planes. The rudder seems to mess me up. A buddy suggested putting the rudder on the aileron channel to see if that made flying feel more natural. Perhaps my drone experience is pushing me that way. When learning drones I finally got the most success from building a micro drone and learning to fly it which brings me to my question.

Iíd like to build a small kfm delta wing (maybe 2í span?) that runs a small 1104 brushless motor and a 2.5-3Ē prop. 450mah 2cell battery. Quick to build/rebuild. Iíve been searching for plans on here for something like that but havenít had much success. I did find the $5 challenge one but it used a larger 2205 ish motor and was pretty fast (not for beginners). Can I modify those plans? Or does anyone know of a design that meets these needs? Thanks in advance!
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Dec 10, 2019, 09:44 AM
Registered User
GeoffS's Avatar
If you aren't 100% set on a scratch-build project, the ZOHD Dart is a very nice little FPV mini-wing.
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Here are some threads about it:
https://www.rcgroups.com/forums/show...build-log-mods
https://www.rcgroups.com/forums/show...49-%C2%A333-91
Dec 10, 2019, 09:49 AM
Perpetual Noob
BoxCar31's Avatar
I will suggest joining the AMA if you're not already a member. Contact the Zephyr Hills flying club and ask for their help in learning to fly a "plank." They ca get you started and probably help with building/designing your wing too.

www.can-amflyers.com
Dec 10, 2019, 01:10 PM
Registered User
Thread OP
Thanks for the replies! I really do enjoy building, I’ve already built myself a nice little hot wire cutter and got some pink insulation foam in 1/4 and 2” I will look into joining the ama although I normally just fly at my home on our property. It’s about 5 acres and wooded on 3 sides which is another reason I was wanting something a bit smaller.
Dec 10, 2019, 01:28 PM
B for Bruce
BMatthews's Avatar
On delta wings the KFM style airfoils are really more for structural gains than any aerodynamic gain.

Also depending on the leading edge sweep angle your "delta" wing might be more of a tapered flying wing than it is a proper delta wing. Just saying..... But something to keep in mind so you are building and describing the right sort of thing.

The racing quad 1104's look like they'll have the power you want. At least in short bursts. Pick one that has a low Kv value so you can use it with as big a prop as you can for better climbing.

Model planes fly best when they are light. I'm seeing figures of 80 to 120 watts for the motors when used in short bursts of up to 3 minutes. So power isn't an issue. Even running one of the 120 watt motors at more like 80 watts to avoid overheating will give you lots of power and climb if you can make the model come in at around 6 oz total weight. And on a fairly short and longer span delta like flying wing at around 24" span you don't really want the weight to be much higher than around 6 oz anyway or the gliding and landing speeds will suffer and the model might even do high speed snap rolls out of sharp higher G turns if overweight. A good balanced design is not just about power to weight. You also need to consider the wingloading to get all around good flying manners that lead to a higher grin coefficient.

With light gear you SHOULD be able to make a workable delta like flying wing out of some dollar store foam board. Just don't go crazy with large double layered areas that pile on the material.

Good luck and if you like post a sketch of the wing plan over in the Scratch Built Foamies section and get their feelings on the wing design so you avoid any major flaws.
Dec 10, 2019, 01:33 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by Topher01
Good morning! My question is in paragraph two if you wish to skip the background info I’ve been a drone pilot for about 3 years and love it but recently I’ve been wanting to try fixed wing. I’m really interested in it most because of the scratch building aspect with foam. I built an ft mini scout and our maiden wasn’t so great. It flew amazingly until I got my thumbs confused and after that it wasn’t right because I knocked the offset out of the motor pod. Since then I’ve begun repairing it, and also downloaded plans for Magnum Reloaded. I decided to try a sim before I tortured more parts and found picasim. I wasn’t able to find rc desk pilot because the site kept living me an error. I’d still like to get it and fly all the ft planes. I noticed I was much more comfortable flying the wing with elevons vs the planes. The rudder seems to mess me up. A buddy suggested putting the rudder on the aileron channel to see if that made flying feel more natural. Perhaps my drone experience is pushing me that way. When learning drones I finally got the most success from building a micro drone and learning to fly it which brings me to my question.

I’d like to build a small kfm delta wing (maybe 2’ span?) that runs a small 1104 brushless motor and a 2.5-3” prop. 450mah 2cell battery. Quick to build/rebuild. I’ve been searching for plans on here for something like that but haven’t had much success. I did find the $5 challenge one but it used a larger 2205 ish motor and was pretty fast (not for beginners). Can I modify those plans? Or does anyone know of a design that meets these needs? Thanks in advance!
I took a look at your other posts ..... are you still building the Divinity wing ?

In My Opinion ( based on 10 years of RC fixed wing flying and scratch building ) , for a first time RC fixed wing flyer ..... there are two important characteristics a plane should have :
1) slow flight
2) self-leveling

The main ingredient for slow flight is low wing loading : maximum wing area combined with minimum weight . That is difficult to achieve with only a 2' wingspan . And tiny high KV motors are not ideal for slow flight , it's like trying to drive your motorcycle slowly in high gear .

Self-leveling can be accomplished in two ways :
1) build a plane with a high wing that has dihedral ( wing ends angled up )
2) use electronic stabilization

If you really want to continue with a non self-leveling flying wing and have multiple small motors , you could build a flying sheet of dollar store foam board . You could use two of the tiny motors/props instead of just one , and even set it up with differential thrust for steering left/right . Here is my flying sheet of foam board , it took about 20 minutes to build :



"Literally" just a Flying Sheet of Dollar Tree Foam Board (1 min 13 sec)
Last edited by balsa or carbon; Dec 10, 2019 at 01:58 PM.
Dec 10, 2019, 03:16 PM
B for Bruce
BMatthews's Avatar
And with smaller control surfaces (about 1/3 of the size shown) a flat pizza box plane like that would be as good an option as you would need for a "trainer" of that sort. The smaller surfaces would both reduce the control sensitivity for you as a beginner and at the same time reduce the risk of control surface flutter if you let it get flying too fast.
Dec 10, 2019, 03:39 PM
Just here to have fun with RC
Rhea's Avatar
The first time I built and flew a delta wing foamy I was amazed at how much fun it was. I followed the plans for a Blue Foam Wonder and when I was done I realized it was nothing more than an Isosceles Right Triangle. It doesn't even have to be a KFM but a piece of flat foam.
You can make it any size you want to fit the power system you have. There is really no limit to the fun you will have with a triangular piece of foam.

BTW 2' span might be a little bit too big for that motor. It would depend a lot on the prop you choose.

https://www.theparkpilot.org/bluefoamwonder
Last edited by Rhea; Dec 10, 2019 at 04:13 PM. Reason: Added link to Larry Towner's Blue Foam Wonder
Dec 10, 2019, 03:48 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by BMatthews
And with smaller control surfaces (about 1/3 of the size shown) a flat pizza box plane like that would be as good an option as you would need for a "trainer" of that sort. The smaller surfaces would both reduce the control sensitivity for you as a beginner and at the same time reduce the risk of control surface flutter if you let it get flying too fast.
A very big/tall vertical stabilizer also helps reduce control sensitivity , especially on roll .
Dec 10, 2019, 07:09 PM
Registered User
Thread OP
Wow thanks for all the info, it’s a lot to digest! I liked the kfm airfoil because it appeared simple to reproduce because it was simply layering as you mentioned. I guess I don’t fully understand what makes a wing “delta” or not, I noticed it helped very much as a search term when I was looking at plans and build threads. I had printed the divinity plans and was getting ready to build it but when I got to the the flexible control rods part of the plans it became a bit intimidating. I also figured that design may not fare well with crashes either. So I printed the ft versa wing on the other side of the paper and just sat down to cut it out. It seems to be fairly straightforward to build and the control rods are normal. I’ve also stripped all the extra weight from the ft scout. I have a 2205 2550kv motor on that with a 3 blade 5045 prop. I was flying it with either a 3s 550mah or an 850mah battery. It flew well and didn’t seem uncontrollable but perhaps that’s too aggressive? Thanks very much for taking the time to help. I really appreciate it!
Dec 10, 2019, 08:07 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by Topher01
Wow thanks for all the info, itís a lot to digest! I liked the kfm airfoil because it appeared simple to reproduce because it was simply layering as you mentioned. I guess I donít fully understand what makes a wing ďdeltaĒ or not, I noticed it helped very much as a search term when I was looking at plans and build threads. I had printed the divinity plans and was getting ready to build it but when I got to the the flexible control rods part of the plans it became a bit intimidating. I also figured that design may not fare well with crashes either. So I printed the ft versa wing on the other side of the paper and just sat down to cut it out. It seems to be fairly straightforward to build and the control rods are normal. Iíve also stripped all the extra weight from the ft scout. I have a 2205 2550kv motor on that with a 3 blade 5045 prop. I was flying it with either a 3s 550mah or an 850mah battery. It flew well and didnít seem uncontrollable but perhaps thatís too aggressive? Thanks very much for taking the time to help. I really appreciate it!
A "delta" is simply a triangle shape . KFm is not necessary for flight , but it will help to strengthen an airframe . A very simple delta you can make is a rectangular board ( like dollar tree foam board ) with the two front corners cut off at a 45 degree angle , and then glue the cut-off corners back on to the nose ..... one on top and one on the bottom . That will make the nose triple-layer thick for strength , and will aid in getting a flyable CG . Here is a simple delta that was made that way :



Giant simple delta (2 min 0 sec)
Dec 10, 2019, 09:46 PM
B for Bruce
BMatthews's Avatar
Topher, for what it is worth my own personal interpretation of what is a "delta" wing vs a special case of tapered flying wing is that a delta wing should have the leading edges at no more than a 90į angle. Most of the fighter jets with delta wings have the leading edges at more like 45 to 60 į at that particular point. If it's much more than 90į then I see it as more of a fluke of the taper and sweep angle producing a straight across trailing edge.

This isn't an iron clad rule though. But from the looks of his sketch above it seems that BorC has the same interpretation...

A lot of things have been attributed to KFM shapes. But so far I've not seen any actual wind tunnel or even simulated fluid dynamics testing that shows the usual folded over but otherwise flat KFM airfoils to be any better than a flat plate. And that's why I suggest that mostly it's about gaining some structural advantages instead of airfoil advantages. And since flat plates are not all that good for making lift without a lot of drag it still comes down to keeping the wing loading low if you want some variation of a flat plate airfoil for your wing. And if the wing loading is low then you don't need much of an airfoil at all. A situation that is well supported by some great flying F3P models that do all sorts of crazy indoor stunt flying..... and which are VERY light for their size.
Dec 10, 2019, 10:26 PM
Registered User
Thread OP
I’ve just gonna back through and reread everything. One thing I find confusing about these incredibly simple flat sheet builds is how do these flat sheets of foamboard generate lift with no aero foil shape to them to slow air across the top of the wing? Or does the elevon act as the aerofoil curve? Also would it make any sense to build in 2-3* dihedral to the wing? I read that the swept back design of the wing inherently adds dihedral effect but you could add more?

I like the analogy about the motor size. I have a bunch of spares but quad stuff is always pretty high kv compared to what I see on fixed wing. The 1104 are hglrc brand 7500 kv. They will swing a 2.5” prop. Can I run a large low pitch prop to kill some of the kv or do I just need to buy a couple power systems? The esc I’m using are from amazon. Simon k 30a w 2a bec. They seem I little big but I’ve already smoked one and they are cheap $22 for four. I just didn’t want to go buy a bunch of new stuff because I’m just gonna crash and outgrow it but I also want to enjoy fixed wing. I wanted to learn it because sometimes I want to fly something more relaxing than my quads. Thanks again for the help!
Dec 10, 2019, 11:31 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by Topher01
Iíve just gonna back through and reread everything. One thing I find confusing about these incredibly simple flat sheet builds is how do these flat sheets of foamboard generate lift with no aero foil shape to them to slow air across the top of the wing? Or does the elevon act as the aerofoil curve? Also would it make any sense to build in 2-3* dihedral to the wing? I read that the swept back design of the wing inherently adds dihedral effect but you could add more?

I like the analogy about the motor size. I have a bunch of spares but quad stuff is always pretty high kv compared to what I see on fixed wing. The 1104 are hglrc brand 7500 kv. They will swing a 2.5Ē prop. Can I run a large low pitch prop to kill some of the kv or do I just need to buy a couple power systems? The esc Iím using are from amazon. Simon k 30a w 2a bec. They seem I little big but Iíve already smoked one and they are cheap $22 for four. I just didnít want to go buy a bunch of new stuff because Iím just gonna crash and outgrow it but I also want to enjoy fixed wing. I wanted to learn it because sometimes I want to fly something more relaxing than my quads. Thanks again for the help!
The flat sheets generate lift by having a positive angle of attack to the oncoming airflow , much like waterskis have a positive angle of attack to the oncoming water . For model airplanes , this works well for smaller sizes and slower speeds where drag isn't much of an issue . For larger aircraft and higher speeds where drag is more of an issue , it's beneficial to have a rounded leading edge and a tapered trailing edge for smoother airflow ( less drag & turbulence ) . And with a curved airfoil : the Bernoulli principle factors into the lift equation to varying degrees also , but angle of attack is always in the equation . For example : when you input up elevator on the controls , you are changing the angle of attack of the wing to more positive ..... which translates into more lift ( climbing ) .
Dec 10, 2019, 11:41 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by Topher01
Also would it make any sense to build in 2-3* dihedral to the wing? I read that the swept back design of the wing inherently adds dihedral effect but you could add more?
Yes , you can add dihedral to a delta .... RCGroups member Nightstone did so on this delta , it seems to fly very well :



DiamondSE (5 min 25 sec)




Notice that he put the vertical stabilizer underneath the plane , instead of on top . Also , you can see in the video that he has a KFm1 airfoil ( underneath the wing ) .
Last edited by balsa or carbon; Dec 10, 2019 at 11:48 PM.


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