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albine92

Vortex Generator for RC Plane / Wing Reptile S800 Sky Shadow

by albine92 Jan 15, 2017
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Wing tips break and when removed the wing is less stable. Will VG stabilize the wing?

Hello.
Unfortunately not, the wing tip being removed will reduce lift and will cause the plane to behave quite poorly. Youll be better off replacing the wing tip.

Ok, I'll print new ones.
From your video the VG energize the boundary layer to make it more "sticky" how much lift does it add in the case of the s800?

hello, how does it behave at high speeds? what's your maximum speed?

Hello,
Using a pitot tube, i've recorded 78mph (125kmph) in a dive. Usually i get about 45-50mph in level flight depending on the motor and prop setup i'm using. With or without the vgs, the wing is always stable and behaves well.
These do reduce top speed ever so slightly but their main job is to help low speed flight so its a trade off really.

Hope this helps :)

Hello, just had a question regarding placement, more just wanting to understand why you chose to do one VG, when on most full size acft there are two (-15° and 15°). Is there a benefit to have a single VG aside from weight?

Good question! I did single VG's as it is easier for people to apply to ANY of their planes, not just the S800. If i did a twin VG for the S800, it would only work with wings that have a very similar or identical wing sweep angle.

A twin VG would be easy for a straight wing plane such as a Cessna, but to keep the 15 degree angle, a new version would have to be designed for each sweep angle if this makes sense?

Thank you for your question :)

Does make sense. I called Micro AeroDynamics and spoke with Anni. She informed me the "pigeon toe" placement is better for slip control-ability. I think this could be more beneficial, for a wing especially. She also told me due to the size of the VG's the space between the pigeon toed VG's will not make a difference on this scale, so place them as close together as desired. I am installing these on an AR Wing, which is similar to the S800 but not identical. Anni gave me a bunch of good tips on finding ideal placement for this handy print. Thanks again for uploading for us to science nerd out on. :)

Do you know what your root/tip chords are? I'm trying to create an airfoil with your VGs for a demonstration in a water tunnel, but I can't find the RC plane dimensions online. I just want to make sure I scale the VGs correctly

are they really that small and thin or i am printing them wrongly? like 2mm thin and little more than cm long?

Yes they are that small, you are printing correctly!

Their job is only to creat a small vortex behind them hence the tiny size.

thanks for fast reply, I can't get them smooth on both size due to only 6 layers, should I sand them a little bit from the top side? Or it does not have to be smooth?

The exact size isn’t really an issue. Feel free to sand them if you want them smooth but rough will work just as well.

Is there a reason why the 15° inclination is pointing "far from the motor" and not the opposite?
The airflow (for delta/arrow wings) tends to divert from the wing root to the wing tip due to the wing geometry, and that's also why the stall tends to begin at the wing tip (reducing the autorithy over the elevons/ailerons, which is bad).
With that being said, wouldn't be more efficient to have the VGs pointing the airflux towards the motor (if now the angle is "plus" 15°, i suggest to install the VGs at "minus" 15°).
Does this make sense for you?

This is a very good question!

The vortex generators here are too small to properly direct air towards the tip of the wing, they only manage to produce a small vortex behind them due to their size. If they were bigger in relation to the wing (if they looked more like wiglets / fins) then you would be right and the angle they're set at would be a slight issue.

With a swept wing, a wing fence (Boundary layer fence) can be used to stop span wise air flow across the wing. Which can also be used in combination with the VGs if desired.

The angle the VGs are set at, can alternate if desired (pos 15, neg 15, pos 15, neg 15..) or be all reversed (all neg 15) as you pointed out, with no ill effects either way.

I never really tought about a wing fence on a small rc flying wing, mainly because of the additiona weight, and i really don't want to use thin carbon fiber sheet to do that.
But actually wing fences would be a really good thing (if you want to preserve lift at low speed) because the flow across the wing became more and more significant with the reduction of the airspeed.

Anyway, i'm probably overthinking since i'm talking about a 300grams flying wing that will hardly pass 10m/s... :)

I like your thinking. Even though these are small and light, they still experience the same effects as a larger, heavier plane.

I was going to do some wing fences for this plane as 3D printed ones would be incredibly light and could be fairly strong too.
I just never got round to drawing the aero foil shape on CAD.

Same here, if you find an easy way to draw the airfoil on cad please report.
Greetings from Italy!

Ps: i'm using the rainbow 800 as "test plane", waiting the right offer (from china) i've purchased two sets of wings for about 11$ each, and i won't be mad in case of crashes... :)

It is a very tough plane! You'll struggle to break it i think!

I will let you know if i ever get round to tracing the aerofoil :)

hello, can you please tell me which aerofoil is used for the wing. thank you

anyone can please tell me which aerofoil foil is used for reptile s800. thankyou

Anyone try the flow generators on the outside of the winglets? The winglets are asymetrical airfoil with the long curve on the outside. Thinking a little outside the box.

Nice idea but unfortunately this wouldn’t do anything for you. The winglets are there to minimise wing tip wrap around and vortex drag, they don’t produce lift them selves. They also maximise lift along the entire length of the wing.

If you’re looking for other ways to maximise lift, especially at low speed, a wing fence, aka vortex fence, would work too.

I have a RMRC Recruit (AR Stealth Wing) ... Would these actually help this wing as well...or are these specific for the s800?

Hi, these will work with literally any wing. You just have to make sure that they are at the angle specified relative to the direction of flight.

These can be used on everything from a straight wing, such as a Cessna, to a high sweep angle wing like the Concorde.

The only thing you have to do is make sure you have the right angle relative to the direction of flight.

I hope this helps buddy!

Damn.... I'm not sure how to figure out the angle... I would guess the 15° would be about right?

Yes mate, anything from around 10 to 20 degrees relative to the direction of flight will be fine.

Hi, will try and tell you if I feel the difference. Hope that will change S800 behaviour. Thanks.

Looking forward to your feedback! I hope they help!

Cheers, Andy

Do these vortex generators have any affect when you're flying at cruise speed? Do they slow it down at all?

By design, yes they will as they create pressure drag. But it will be negligible on a model of this size, weight and power.

So basically, yes but you wont notice.

Thanks for those, made a huge difference on my wing :)

I've made a simple tool to help placing the generators.
https://www.thingiverse.com/thing:2544706

Sky Shadow S800 Vortex Generator Placement Tool
by warhog

I'm glad they helped you out!

That tool looks awesome! Great idea! Would it be okay with you if i put a link to them in the description?

Thanks again!

Sure, you can put a link there :)

Nice one! Thank you dude!

Disclaimer I'm a noob fixed wing pilot ymmv. The S800 had really bad stall characteristics for me. Almost every landing I'd try to glide in and have sudden hard stalls as I slowed, usually 15-20 up which would turn into direct nose in crashes, luckily with limited speed.

These Vortex Generators made an instant improvement. I put 5 per instead of 6 (lost one somewhere and didn't want it lopsided), at 15 degrees off airflow 60mm apart as instructed. Night and day difference for me, plane now gently tips its nose down as I slow with no sudden harsh stall that I've noticed.

I am very happy that they worked as they're supposed to for you!

Thank you for your comment too, its lovely to know that something i designed has been used and works well!

All the best and happy flying!

One suggestion, could you make the front of the glue plate 15 degrees (and thus 2 versions) we could use to align with front of wing ?
Also thinking, that maybe creating a 120mm (most can print that) thin strip with 3 pcs on. Would make aligning/mounting easy. The strip could be 0.3-0.5mm.

Or a template for mounting. strip with 2 holes (for 2 vortex generators), 15 degrees off center, and the 2 cm space out the wing edge, Would get consistent mounting.

That good idea! Ill look into doing that.

I used a piece of 20mm wide tape to get the correct distance from the leading edge and then marked on tape every 60mm, to get the right spacing. To get the correct angle, i just cut a piece of card, lined it up along the edge of the tape and that gave me a consistent, correct angle.

Cheers for the suggestions! Ill look init!
Andy

I made one myself. Basicly it is just a 45 degree angle (assuming the wings are 30 degrees as you said) relative to the front, and a guide sticking out 2cm back. Fast to make i Fusion360, and it takes a 1 minute only to mark all the spots.
Since the mark is from the thingie that goes into the wing, my guide should likely be 2.5cm back if I would make another.

Do thease need to be at small angle against the airflo?

Yes mate, I put mine at 15 degrees against the airflow and they seem to work well. Feel free to experiment with them though.

Thanks for sharing! I printed and will mount today!

Thats awesome!! Let me know what you think!

just ordered my s800. will add this to my to print list. always loved to experiment with vortex generators. great work!

You find your s800 has poor glide? Mine floats! How heavy is your build? With an sj5000+, fpv cam, 2200mah and the obvious vtx and my rx I'm at 579g. Im still gonna try these on my second s800 (on order) as id like to see the difference they make. A plane that would love them... The Go discover! Mine at least had shocking stall speed!

I wouldnt say its a terrible glide. Ive got an RMRC MAKO which is a 1.2m wing and i think im used to that more than these slightly smaller wings.

With everything, im at 600g on the dot. 1 of my S800s seems to glide better than the other though...

These do help especially to make slower landings.
If you do print and use them please stick a picture up, id love to see it!

Ah yeah, I've got an x8 that just glides forever! These aren't like that. But not bad. I'll definitely print and put a picture up!

Hi mate!
I usually go flying on my own so videoing the landings and stall speed it very difficult.

I will try and set up a gopro to film it next time i go.