Glider Flaps Thermal Entry and Exit

How I fly with flaps in my Ventus CT.
Note I'm not an expert, I've spent most of my flying career in standard class gliders like the Discus and DG300. And this glider is relatively new to me. Also trying to narrate a video and fly is more difficult than you'd think, my speed control was all over the place!
I'd love to know if others use similar techniques or any thoughts. Comment below!
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[@danielsazhin9226]

Cool video! The way you described using the flaps is how many people typically use them, however, it's sub optimal. The misconception is that flaps are driven by airspeed, but in fact optimal flap position is driven by Angle of Attack (driven by airspeed AND G-loading). The easiest approximation is that you should be dropping the flaps as you are pulling back on the stick and retracting flaps as you push over. As you pull into the thermal, you should be dropping the flaps while you are pulling into the turn rather than waiting for the speed to bleed off. The second misconception is that the flap forces on the handle are an indication of drag. That's not necessarily true. Remember that the flaps adjust the whole camber of the wing. So yes, you might have additional force on the flaps on the back, but depending on the balancing of the linkages, the camber that lines up with the least amount of force on the flap does not necessarily optimize the forward 2/3 of the wing to the optimal airfoil. Usually it's close enough, it's just to say that while it "feels" right, it doesn't mean that it must be so. Which is to say, simply consult the tables for your wingloading and simply put the flap into that position. Thanks for the video!

[@PureGlide]

Hey thanks for the comment. Yeah I've since learned how they flap levers are usually sprung in some way, and looking at mine while it's pulled apart it is indeed sprung. So just that means the 'feel' isn't going to be just the air pressure. And yes makes sense re angle of attack, I guess that is what you 'feel' anyway. It would be interesting to see an angle of attack indicator in a glider. Good advice, follow the manual...

[@miketaylor3947]

I thought that the flaps were driven by the little handle on the left side of the cockpit ;)? More seriously, I would have naively thought that flaps are used depending on what you're trying to accomplish. Fly slow, more flaps, fly fast, no to negative flaps?

[@PureGlide]

@@miketaylor3947 Yeah that's it, fly fast use negative flaps, fly slow use positive flaps. Pretty simple really! But there are subtleties like how much flap at which speed exactly. And do you ease into the flaps before reaching that speed or as you reach that speed.

[@miketaylor3947]

@@PureGlide thanks! I've got some time in an l 23 super blanik w no flaps and powered seaplanes w flaps, oh the thrill of pointing directly at the sea w 40 degrees on 🤣

[@RoelBaardman]

This video illustrates that nicely I think. It's a video of a glider (Mue-28) with automatic flaps based on airspeed and g-loading: kzbin.info/www/bejne/jn6php6jbqxohbs

[@lautoka63]

Darn you guys with your genetically-modified Discuses! Nice work, Tim.

[@PureGlide]

Haha never heard that before. Hey hang on Ventus was produced 1980, but Discus was 1984! Nice try obviously a Discus is a Ventus with bits missing :O

[@TheCryptKeeper8]

Thanks. Amazing that this is the only video I can find searching for "glider flap settings" All others are about RC a/c

[@PureGlide]

Thanks! Glad it's useful. Make sure you read the top pinned comment too as what I said in the video isn't 100% accurate. In summary: follow the instructions in the manual for best flap setting at any particular speed. But my vid still shows how I use them. Those damn RC videos are a pain, especially the ones that don't have RC in the title!

[@diamondmidnightgardener]

the first actually useful content I've seen on the net for years..... subscribed!

[@PureGlide]

Thanks Phil! Appreciate it :)

[@mitchellkaye9619]

Excellent, practical and easy to follow. Thank you!

[@PureGlide]

Glad it was helpful!

[@palleh.jensen4648]

Hi Tim, thanks for your videos, they are great training tools, keep it up. Cheers Palle.

[@PureGlide]

Glad you like them! Just remember this one isn't quite accurate, read the pinned comment :)

[@wiebebosman]

Nicely shown and told!

[@PureGlide]

Thank you! Be aware it's not quite accurate, read the top pinned comment :)

[@ricklederman]

Thanks for the great video. It is nice to see someone that has speed control problems once in a while too, although narrating the video makes it much more difficult. Also, while circling in lift I noticed how much opposite aileron you need to hold, similar to the Stemme S10 that I spent a few hours in before getting my S12. The S12 has polyhedral which allows you to circle without holding ANY opposite aileron. Polyhedral is a R/C or freeflight model term that most full size folks never hear, and it really works.

[@PureGlide]

Interesting! And glad you liked the video, cheers

[@Marcus-cz5uu]

Great demo

[@PureGlide]

Thanks!

[@Christopher-pe6zj]

Great video!! :)

[@PureGlide]

Thanks!

[@Firefox131]

Thanks! That makes sense!

[@PureGlide]

Cheers!

[@willhibbardii2450]

I've never been in a glider other than twice experiencing catastrophic engine failure in single engine piston aircraft. Trimming for best Vg is paramount for extended time in the air when the propeller stops. We practice this with the engine wind-milling at idle power. Gives time to pick the landing spot and keep it insight and go through the checklist if sufficient AGL is available. In both cases I had over 3,000 feet AGL and had time to check possible engine out solutions with no joy. When the prop stops it's surprising the how much more energy the aircraft has than when the propeller is wind-milling creating drag. In this situation I kept the aircraft clean till I had the landing spot made. This made my first off airport landing uneventful though inconvenient when I was a teenager. The second was an uneventful on airport landing that I was directly over, enroute to where I was landing and I had 7,500 AGL when I was in my early 40s. Again inconvenient but uneventful. Glider flaps and spoilers offer a great dimension of knowing how to avoid sink with correct airspeed. I've never flown an aircraft with negative flap settings, however with laminar flow wings this could be a dimension that could add airspeed to piston aircraft. I have allot to learn about gliders. Thank you for sharing! I'm designing my own carbon fiber aircraft. Seems the glider enthusiast have worked out many compromises I wasn't aware of till this week thanks to you guys!

[@PureGlide]

Thanks for watching Will! And thanks for sharing your stories. There's a bit of a difference when the glide ratio of the gliders is 49:1 compared to an engine cutting out on a plane :) Yes gliders really are at the forefront of aerodynamics. I listened to an interesting podcast recently about Winglets and how they came to be, first found on gliders before all the big planes! Very interesting. soaringthesky.com

[@willhibbardii2450]

Thank you ​@@PureGlide​ for the link. I will enjoy going through it. Yes winglets are amazing! I worked with them in creating hydrofoils for boats. They provide great compromise solution for low-end and midrange improved performance with very little effect of parasitic drag on top-end performance. The fuel savings at cruise is minimum 7% and I have seen as much as 35%. I love doing more with the same thrust. I'm a sailboat enthusiast and love working with nature for power. For the past 5 years I've been commissioned to build electric power drives, 15KW off grid inverters and power management systems, which exceed normal Q performance. I've developed a 1.5 KW metronomic/parametric system that runs 216 hours on a charge. This is actually old technology developed in the 1930s. I'm moving into the next phase of 15KW power for the same runtimes and think I can run at 45KW for up to 6 hours. One of the items in my bucket list is to develop a pure electric aircraft with minimum of 6 hours runtime. My plan is to make the batteries/super capacitors part of the airframe instead of modular battery power packs. I'm working with composite combinations to achieve this. I've been searching for existing female aircraft molds to further develop and test my system. Peter with Raptor Aircraft is getting ready to test fly his unit powered by an available Audi 3L TDI diesel engine redrive combination. Burt Rutan ingeniously utilized this winglets as a triple combination of winglets, rudders and speed brakes. I wasn't aware the winglets served as speed brakes till a few days ago. I still think that flaps should be part of the solution as well. I never knew why I liked connecting to the clouds at 500 feet below them in overcast. Till watching Bruno Vassel demonstrated it in his glider. I hope to get acquainted to the glider community. Living in Texas flat lands all the gliders are best operated around the mountains. Thanks to the internet I'm getting interest and see myself flying one soon! Best wishes sir!

[@zeljkoroskar6237]

Thanks for sharing. We share the same glider. What I do when entering the thermal, I'm starting rolling it with flaps 0, when I have the bank that I want only then I go flaps +1. Occasionally only in very good lift, maybe flaps +2... But never in positive flaps (+1) when flying straight

[@PureGlide]

Hey thanks for sharing! Sounds sensible

[@jme104]

I started flying my old flapped glider in thermals without using the 5° plus flap position and I have no problems. I decided I should try using no flaps in thermal because of this: I was trying to thermal very low at a few hundred meters outside the base leg , after I found nothing usable I decided to make a straight in on the runway in use and I had trouble accelerating my speed from 80 to 110 km/h for my final . I then realised a had the 5° down on my flaps and that caused a lot of drag hence my decision to try thermaling with a 0° setting . I' now using the 0° setting for thermaling and that causes me no problems .

[@tinchote]

I'm not familiar with the Ventus, but I flew the ASW20 extensively, and the recommendations from the manual are fairly different to what is mentioned in the video. I'm curious whether it's design or philosophy. The ASW20's manual directly says that speed is mostly controlled with the flaps, with the stick used for minor corrections. It also mentions that the spirit is that you want more flaps when you have higher G, and less when you have less G. So when you accelerate you want to have negative flaps as early as possible, and the opposite when you pull.

[@PureGlide]

Yes that makes sense, and no I don't think they're that different. I haven't flown the 20 for a long time, but don't remember it being that different. It's more my flying style to try and make the flaps match the flying speed, so flaps are eased on as I accelerate, and eased off as I decelerate. As mentioned in the top pinned comment, more correct is to follow the flap settings for the speeds as set in the manual. You can't judge it purely by feel due to springs on the flap system. I also understand that flap changes too early or late really won't make much difference, and far more beneficial is to quickly centre climbs and stay out of sink!

[@adamcumberlege8228]

Great to see some real flying. I miss my ASW20, it worked exactly the same way. For my sake what were you flying?

[@PureGlide]

Thanks Adam, this is GOP, the Ventus CT. Cheers!

[@CoinedBeatz]

I fly a ash26 and my experiemce with flaps is mostly changing flaps too quickly does more harm than actually help. The flow takes some time to adjust to the profile apparently and also my subjective experience concludes this behavior. Another advice is to use neutral flaps for centering thermals and in turbulent air. Makes circling more comfortable.

[@PureGlide]

Thanks for the feedback

[@johannesachleitner912]

Hi, the flow takes only the time which it needs to pass one chord length to adjust. So thats a matter of fractions of a second. Nevertheless its a good advice to use the flaps gently, as you may put significant g-loadings on the aircraft, which then causes additional drag.. Gerhard Waibel wrote an excellent article in the ASW 20 flight manual, which still is 100% correct from an aerodynamicist point of view. I absolutely recommend reading this and use the flaps accordingly..

[@mikeroark6009]

Good morning! Thanks for all the great videos. I flew gliders in college when I should have been studying. 2-33’s and 1-26’s. ( back in the 70’s ) We didn’t term our climb in thermals by using knots but rather feet per minute. What do you mean by a 6 knot climb in a thermal? Thanks!

[@PureGlide]

Hi 6 knots is roughly 600 feet per minute. So easy to convert!

[@antigoon78]

Nice quiet glider you have!

[@PureGlide]

Thanks! We just repainted it and removed the Mylar from the front edge of the canopy frame. So it’ll be interesting to see how she is now! Flying tomorrow

[@antigoon78]

@@PureGlide Have fun, could you do a walk-around video so we can see the result? Always cool to see someone-elses ship. I fly an ASW20 :)

[@PureGlide]

@@antigoon78 Yeah I'd love to, will try in the near future!

[@jme104]

On my LS3a, the builder recommends use 5° flaps when thermaling but after checking Dick Johnson's polars and trying it in flight I found that you can perfectly circle at 80km/h with flap setting zero .

[@PureGlide]

Yeah the best thing to do is test out the flaps and see how they feel at different speeds. It’s really hard to compare how effective it is for flying in a thermal because they change all the time. I guess you could test sink rates at different flap settings and speeds in still air… or compare to other gliders in the same thermal

[@jme104]

@@PureGlide Following Dick Johnson's puplished polars in his february 1980 article, it looks like the LS3 A has a better sink rate with 0° flap setting . On his comments he says "minimum sink rate is not achieved with the +10°( 5°? )flap setting, but its lowered minimum airspeeds provide tighter circling radii". As my test was conducted using an 80km/h (43kts) speed, I think I can not anyway fly slower even with the flaps at +5 or +10°.But all that concerns only the LS3A .

[@KonradZaprucki]

Nice video! What software do you use on the iPhone on the left?

[@PureGlide]

Thanks! That’s the GNZ tracking software gliding.net.nz/tracking

[@thepb7913]

I will try ‘floating flap’ and see how it compares to the LXNAV flap tape, which takes into account G-loading and airspeed.

[@PureGlide]

Yeah as mentioned in the top pinned comment, I'm not sure floating is the best way to go, as the flaps are spring loaded. So best to obey the LXNav tape!

[@SuperReasonable]

I have owned 3 flapped gliders and the ASW20 and Ventus 2a were very similar. Trim to a set speed in 0 Flap and then use the flaps to keep the nose at the same attitude, or presentation to the airflow. However, our EB28 is a very different beast with the flaps having less impact on attitude and must be operated by pure airspeed indication. It’s also very different with thermal entry. The Ventus was excellent for pulling up and clicking the flaps back as you slowed, drop it into thermal flap and turn. The EB needs to be turned first and once established, slow slightly to around 55knots and then apply thermal flap. I guess what I’m saying is that there’s quite a difference between operating a 15/18m glider and a very large span open class glider...

[@PureGlide]

I bet! Thanks for that, I've never flown anything that big :)

[@uhertlein]

In the Ventus B, the flaps are connected to the trim (the trim knob is sliding on the flaps pushrod), so e.g. setting negative flaps will automatically put the nose down to speed up, which I actually quite like. Did they change that in the Ventus C? Thanks for this video, I found it just before asking about your use of flaps. :)

[@PureGlide]

Yeah much the same I think. Only the air brakes are different AFAIK

[@johandewaal]

Thanks for the great video. Might be a stupid question, but do you also use the flaps together with the spoilers when landing? And if so do you use max flap settings?

[@PureGlide]

Hey no stupid questions here! Yes I use either positive 2 flap, or L. I thought 'L' means landing, but apparently it is 'slowly' in German. The more positive flap settings mean it flies more easily at low speeds. You have a bit more control if you come in faster, especially if it is windy so I might stay in +2 instead of L, otherwise I normally use L. To control our descent rate we then use airbrakes (aka spoilers) as well, which enables us to land right where we want to.

[@TheSoaringChannel]

@@PureGlide didn't know that! I thought it meant Landing flaps also lol

[@uhertlein]

@@TheSoaringChannel I'm guessing Schempp-Hirth wanted to stay consistent with the 'S' setting ("Schnellflug") and made 'L' corresponding "Langsamflug".

[@redsparkinthebluelazer1353]

thanks

[@PureGlide]

No problem

[@grahamstallard4883]

Very intersting. Easy to follow. Do like the device on the right. What is it?

[@PureGlide]

Thanks Graham. That’s a Samsung galaxy tab A6 7” tablet. A bit old now

[@Zed1776]

What is the software you are using on your tablet?Thanks.

[@PureGlide]

The free XCSoar. Handy you can also run it on your phone if you have an Android

[@sidtp7307]

Could you do a segment on how the handling compares for the same plane with different spans. Eg 15 vs 18 or 18 vs 21

[@PureGlide]

You're in luck! Way ahead of you kzbin.info/www/bejne/h4rIfniaapeaf7s I've never flown 21m so can't comment on that, but 15 vs 18 is there.

[@pauljanssens4449]

Yes, approximatively that. But gliding is a science, so here goes. If you have a detailed aircraft manual, like the ls6 has, you’ll find a polar page with one polar for each flap setting. It’ll show you exactly at which speed (or angle of attack) that flap setting does the thing it was designed for the best. You can interpolate the top lines of those polars into the best polar that glider can fly…IF the pilot changes flap settings at the correct moment. The correct moment is where for instance the flap neutral polar dips under the polar of flap-1. So it’s at that speed where you, always, change from neutral to -1, during acceleration or deceleration . So you’re cruising along at 100kts or 186 kph enroute to a thermal. You don’t, like in the video, pull up ahead of the cloud to arrive at 40 kts in…sink. You eyeball the cloud and make a mental picture of where the lift is. You pull up to time it so that you arrive at best gliding speed or just under, right where the lift begins to push. If the lift warrants a circle, you bank in, and go to thermal flap as you go to 15 degrees of bank or so. Thermal flap only help if the wing is loaded up in G, and that only starts when you’re banked. Arriving at best glide gives you better aileron authority to roll crisply into the thermal, after the roll in you’ll find yourself at best climb speed. Easy! If the lift isnt good enough, you can pull up further to min sink speed and drift up in a straight line. Coming out of the thermal, flaps zero as you go through 15 degrees of bank, nose down, wait for your changeover speed,and smoothly change flap setting. In a straight climb, Don’t wait till the vario drops below zero to accelerate , the vario is ALWAYS 3 to 9 seconds behind, FEEl the thermal slacking off and push as soon as you feel that. The vario is only there to show you what you were doing 3 to 9 seconds ago, so its only real value is to confirm that when you pulled up, or accelerated 3 to 9 sec ago you did the right or the wrong thing The key is to train yourself to judge where the lift starts…..and stops. It’s a slow learning curve, but once you master it gliding takes on a different dimension. Getting it right, with the science to prove it

[@LuisOliveira-ns5xp]

Interesting I wanna pilot a glide!!

[@PureGlide]

You should!

[@GregorHarih]

Hey Tim. Just rewatched this video today and saw that you are using a tablet with xcsoar and in later videos you do not use it anymore. How come? 😀

[@PureGlide]

Hi, it's because I've now got the LX9050 installed in the panel :) h just saw the video I had it then too! I now rely on it, don't feel the need for the XCSoar as well.

[@GregorHarih]

@@PureGlide makes sense. 😀 Thanks.

[@naturarum]

Do flapped gliders get better performance than unflapped gliders, when used correctly? I can't seem to find an answer to this question, as glide ratios vary wildly and mostly seem to come down to wing span and design. My club only has 1 glider with flaps (Ventus 2c) and I don't have the hours to fly it yet. Is it safer to thermal using flaps because of the reduced stall speed? Are they better for competition because they are basically made for flying maccready?

[@PureGlide]

Good questions! Yeah the main purpose of flaps is for better performance at high speed. Also they do help for going slower without stalling on landing too or thermalling. So essentially flaps mean you can fly more efficiently at different speeds.

[@naturarum]

@@PureGlide Thanks for answering! I get this theoretical aspect but concretely I'm still not sure how much flaps influence flight performance. Would you say that, all things being equal (pilot, conditions) a flapped glider would win against a standard one?

[@nicolaspilot7189]

Beautiful weather 😍 you aren't in containment?

[@PureGlide]

Sure am, and the glider is in bits being repainted! This was filmed a few weeks ago, but I finally put the video together.

[@nicolaspilot7189]

@@PureGlide We waiting to fly !!!

[@MrAleudine]

Hi! Why you do not set to L position in thermal ?🤔 I note that a lot of competition pilots use it instead of +2

[@PureGlide]

Hi it's the landing flap - I need to test it out a bit more to see if it helps more than +2 for some thermals, otherwise I'm assuming it's for landing and creates more drag than we want. Of course it might mean I can fly even slower and thus for a very tight thermal it might be the best option. I'll get back to you in a few years with my thoughts :)

[@MrAleudine]

@@PureGlideJust try it! I know a lot of famous glider champions that swear that is better (on ventus 2). I use L normally too, after the first centering phase. Only when you need more responsive handling it is better flap less +2 or +1: tipically in rotors or heavy conditions. Note that L it not means "Landing" but for "langsam" that means "slow" in german language?🤔

[@PureGlide]

@@MrAleudine Ah ha! very interesting that L is for Langsam. Yeah I'll definitely spend some time with it, maybe in a few months when we have thermals again :)

[@TheSoaringChannel]

GOD I LOVE THIS COMMUNITY!!!!!

[@Birdie4120]

And for landing do you have spoilers AND flaps?

[@PureGlide]

Yeah sure do, can come down nice and fast.

[@julesviolin]

Are you still using Hawk ?

[@PureGlide]

Sure am, not in this old video though!

[@chris11oz]

my glider has no force on the flaps unless moving to L for landing. How to optimise that?

[@PureGlide]

You’ll have to simply trust the manual and the recommended flap settings for various speeds

[@chris11oz]

@PureGlide I trust the Grossinsky Ring which is better than my memory ;-)

[@ianlazenby3871]

I am actually a blithering idiot, would i be able to fly?

[@PureGlide]

Haha maybe! Who knows, I’m quite a big idiot too, so there is hope

[@christianmeynard4952]

Je n'ai pas tout comprit... L'anglais ce n'est pas évident ! Les planeurs «de course» c'est comme on les sent et bien sûr que ça se pilote pas mal aux volets ! J'y ajouterai un truc de mes jeunes années : Le Bréguet 901 ! Ce truc avait une spécificité : 1 cran de volet et on doublait tout le monde dans les pompes ! Avec les planeurs modernes c'est moins évident. (En fait les planeurs à volets permettent toujours de doubler tout le monde mais plutôt dans les transitions.)

[@PureGlide]

Sorry my French is worse than your English. But thanks for watching!

[@willhibbardii2450]

Christian MEYNARD according to the Microsoft translator - I didn't understand everything... English is not easy! The "race" gliders are as you feel them and of course it drives quite a bit of shutters! I'll add something from my early years: Le Bréguet 901! This thing had a specificity: 1 notch of shutter and we doubled everyone in the pumps! With modern gliders it's less obvious. (In fact, flap ***(glors)*** always double everyone but rather in transitions.) *** Not sure what glors is translating from French to English*** Maybe "glors" is hearing the wind and simultaneously pumping the stick in finding the lift ratio to the thermal utilizing flaps for optimum angle of attack to double the lift relating to indicated airspeed to time of gaining altitude. Trade off of Vx and Vy with flaps but with hearing and feeling? Sometimes it's hard to translate the language barrier.

[@christianmeynard4952]

@@willhibbardii2450 “Glors” does not exist in French. Thanks for reading me. In fact, I was saying that “racing” gliders are just as we feel them and of course that they are well pilot with the flaps! I'll add something from my early years: Le Bréguet 901! This thing had a specificity: at the first step of shutter we doubled everyone in the thermals ! With modern gliders it is less obvious. (In fact, flap gliders always allow you to overtake everyone but rather in transitions.) Hoping to have expressed myself more or less well in English!

[@willhibbardii2450]

​@@christianmeynard4952 Hello sir, If I'm interpolating your racing experience with the Le Bréguet 901 correctly... my understanding is at the first setting of positive flap the configuration speed step, it would shutter (shudder as in shake?) at the slower speed setting as it was close to the stall but double the climb rate in the thermals compared to other designs. This shake shudder is less obvious in newer designs. The 901 and 901S have shorter wingspans than the sailplanes produced today! Paul B. MacCready Jr. was an American aeronautical engineer. He was the founder of AeroVironment and the designer of the human-powered aircraft that won the first Kremer prize. He devoted his life to developing more efficient transportation vehicles that could "Do more with less". He won the 1956 international championships with the 901S which the cockpit was 20 inches longer with these French designs. Thank you Christian for making me aware of this design. I hope to find blueprints of this remarkable glider. These sailplane designers flew by seat of their pants and built in the tell-tail configurations that the pilots probably felt and heard. I imagine they navigated with a compass, turn and bank indicator, altimeter, airspeed indicator. Radio was probably still an expensive luxury and the first variometers (VARIO) Variable Speed Indicators were originally specific to Gliders. These pioneers knew aerodynamics and rules of thumb. It will be interesting to see the tapered wing and to see the overall wing profile on paper. There are probably advancements with modern materials that will be discovered by analyzing this remarkable glider! Pilots learn from each other and good pilots are always learning. I'm glad to talk to someone that's flown this remarkable machine. This Shudder is probably a desired warning of stall that the pilot feels instead of hearing a warning horn. Keeping sailing quiet as it should be. 😊

[@georgehaeh4856]

Perhaps doubler in this context can be pass in English. Does pompe mean thermal?

[@bobsutton9698]

you know nothing

[@PureGlide]

Pretty much Bob!

[@bobsutton9698]

you know nothing

[@PureGlide]

Pretty much