Tip Stalling and Wing Washout
09-08-2003, 09:49 AM
#1
Tip Stalling and Wing Washout
One of the guys in the club tried my plane, the GP Spirit sailplane
This is a Great Planes Spirit Select 2 Meter
http://www.greatplanes.com/airplanes/gpma16.html
He said it was tip stalling and that I should add some washout. He explained what he meant, but I am still confused. He was talking about using a heat gun to warp the tips of the wings.
Can someone help me better understand what tip stalling is and what washout is?
This is a Great Planes Spirit Select 2 Meter
http://www.greatplanes.com/airplanes/gpma16.html
He said it was tip stalling and that I should add some washout. He explained what he meant, but I am still confused. He was talking about using a heat gun to warp the tips of the wings.
Can someone help me better understand what tip stalling is and what washout is?
09-08-2003, 12:21 PM
#2
Join Date: Nov 2002
Location: Bakersfield,
CA
Posts: 136
Likes: 0
Received 0 Likes
on
0 Posts
RE: Tip Stalling and Wing Washout
Hello,
I'll see if I can correctly answer your question. Tip stalling usually happens in some planes as the plane slows below the minimum speed it can fly at efficiently. When you start to tip stall, you'll notice that the plane will tend to drop a wing down forcing you to add the opposite control to level it out which then proceeds to constantly fighting the plane to keep the wings level especially at low speed. I dont know the technical reason for why this happens but I'm guessing the wing tips want to fly more efficiently then the center section of the wing. My Gentle Lady has the recommended 1/4" of washout in per my plans. I can bring it in to almost a crawl and it flys very stable without tip stalling, this may be due to more then just the washout that I added but washout simply adds to low speed stability. I would take a look at your plans and add the correct amount neccessary for your Spirit Select.
To add washout on your polyhedral plane, you can simply hold the wing between your legs and very carefully bend the trailing edge of the wing tip(only) slightly upward as you heat the monocote..be careful not to burn a hole in the monocote if you heat it up for too long. As the monocote quickly cools, continue to hold the wing and then check for your recommended washout amount on a level surface. You may have to do this several times till you get both wing tips to match evenly. Your leading edge will continue to lay flat but the trailing edge should be lifted slightly at the tip edge. Take a look at my photo and you'll notice how the angle of the trailing edge tip is twisted slightly upward as compared to the root side of my wingtip. My plane has removable wingtips but the same theory would apply to your 1 piece wing as only the outer dihedral sections would recieve the washout and not the middle section.
I'll see if I can correctly answer your question. Tip stalling usually happens in some planes as the plane slows below the minimum speed it can fly at efficiently. When you start to tip stall, you'll notice that the plane will tend to drop a wing down forcing you to add the opposite control to level it out which then proceeds to constantly fighting the plane to keep the wings level especially at low speed. I dont know the technical reason for why this happens but I'm guessing the wing tips want to fly more efficiently then the center section of the wing. My Gentle Lady has the recommended 1/4" of washout in per my plans. I can bring it in to almost a crawl and it flys very stable without tip stalling, this may be due to more then just the washout that I added but washout simply adds to low speed stability. I would take a look at your plans and add the correct amount neccessary for your Spirit Select.
To add washout on your polyhedral plane, you can simply hold the wing between your legs and very carefully bend the trailing edge of the wing tip(only) slightly upward as you heat the monocote..be careful not to burn a hole in the monocote if you heat it up for too long. As the monocote quickly cools, continue to hold the wing and then check for your recommended washout amount on a level surface. You may have to do this several times till you get both wing tips to match evenly. Your leading edge will continue to lay flat but the trailing edge should be lifted slightly at the tip edge. Take a look at my photo and you'll notice how the angle of the trailing edge tip is twisted slightly upward as compared to the root side of my wingtip. My plane has removable wingtips but the same theory would apply to your 1 piece wing as only the outer dihedral sections would recieve the washout and not the middle section.
09-08-2003, 05:58 PM
#3
Member
RE: Tip Stalling and Wing Washout
The Spirit is prone to tip stalling because of the absence of LE sheeting on the tips.
In any case, to suppress the tip stall it's best to twist the INNER panels. Just 3/32" washout at the trailing edge at the poly break should be sufficient. Twisting the tip panel itself is much less effective, and it's best to leave it flat.
The reason why twisting the inner panel is better is because tip stall begins just outboard of the poly break. Twisting the inner panel directly reduces the local a.o.a. at this location, while twisting the tip panel is much less effective.
In any case, to suppress the tip stall it's best to twist the INNER panels. Just 3/32" washout at the trailing edge at the poly break should be sufficient. Twisting the tip panel itself is much less effective, and it's best to leave it flat.
The reason why twisting the inner panel is better is because tip stall begins just outboard of the poly break. Twisting the inner panel directly reduces the local a.o.a. at this location, while twisting the tip panel is much less effective.
09-15-2003, 07:35 PM
#6
Member
RE: Tip Stalling and Wing Washout
Excessive washout will produce excessive drag when flying fast (coming back upwind). This is because the washed-out tips will now be producing negative lift. You always want the least amount of washout needed to do the job.
09-15-2003, 08:45 PM
#7
Senior Member
Join Date: Feb 2003
Location: Medina,
OH
Posts: 264
Likes: 0
Received 0 Likes
on
0 Posts
=> No fear <=
'aeajr' and others new to the concept of washout:
There are an awful lot of planes that use washout so have 'NO FEAR' experimenting within reason. In particular, if your plane is rather new to you and you have checked your plane and found out that you currently have NO washout and you can handle the plane then feel free to experiment with handling the plane in various situations, especially in very slow speed flight or working small or light thermals. Then once you have plenty of experience, to the point where you feel you cannot improve the flight performance, try placing a little washout in the wings and again experiment. I believe you will notice there is some improvement in low speed handling of the plane and in some cases, if you really have the plane balanced and tuned well, you might see a dramatic improvement in slow speed handling or tight turns and working small or light lift. As a matter of fact this is one terrific experiment you can try (and is it simple and cheap) because you will most likely detect there IS a noticeable difference and that makes the experiment very rewarding. At some point you will 'see the light' and will be able to detect those situations where washout might be needed in designs of other club members.
As far as the consequences of having too much washout, again, try it. If your plane is well tuned and you really have learned how the plane 'normally' flies, increase the washout and see if there is any noticeable improvement. It should be a very inexpensive and rewarding experiment.
My experience has been that I benefit with 1/8'' to 1/4'' washout in each wingtip on almost any plane I have owned (power and sailplane). Whatever it is it should be set exactly the same for each left and right wing panel. I have seen the suggestion that the washout should be started in the inner panels rather than in the outer panels of a polyhedral wing platform and the author has an impeccable background so he is probably absolutely correct. But I have not experimented along that line yet so I cannot give first hand comments.
But do not overlook a chance to experiment with washout. It can make a good flying plane into a great flying plane.
There are an awful lot of planes that use washout so have 'NO FEAR' experimenting within reason. In particular, if your plane is rather new to you and you have checked your plane and found out that you currently have NO washout and you can handle the plane then feel free to experiment with handling the plane in various situations, especially in very slow speed flight or working small or light thermals. Then once you have plenty of experience, to the point where you feel you cannot improve the flight performance, try placing a little washout in the wings and again experiment. I believe you will notice there is some improvement in low speed handling of the plane and in some cases, if you really have the plane balanced and tuned well, you might see a dramatic improvement in slow speed handling or tight turns and working small or light lift. As a matter of fact this is one terrific experiment you can try (and is it simple and cheap) because you will most likely detect there IS a noticeable difference and that makes the experiment very rewarding. At some point you will 'see the light' and will be able to detect those situations where washout might be needed in designs of other club members.
As far as the consequences of having too much washout, again, try it. If your plane is well tuned and you really have learned how the plane 'normally' flies, increase the washout and see if there is any noticeable improvement. It should be a very inexpensive and rewarding experiment.
My experience has been that I benefit with 1/8'' to 1/4'' washout in each wingtip on almost any plane I have owned (power and sailplane). Whatever it is it should be set exactly the same for each left and right wing panel. I have seen the suggestion that the washout should be started in the inner panels rather than in the outer panels of a polyhedral wing platform and the author has an impeccable background so he is probably absolutely correct. But I have not experimented along that line yet so I cannot give first hand comments.
But do not overlook a chance to experiment with washout. It can make a good flying plane into a great flying plane.
09-16-2003, 07:49 PM
#9
Senior Member
RE: => No fear <=
Sheeting the outer leading edges on the Spirit is easy. I removed the covering, and added on 1/32" sheet back to the spar on top. Nothing on the bottom. Then re-covered.
Haven't flown the plane deliberately into tip-stall conditions, but it is a good sloper.
It had stalled out of steep turns in low thermals, haven't seen like that since.
Haven't flown the plane deliberately into tip-stall conditions, but it is a good sloper.
It had stalled out of steep turns in low thermals, haven't seen like that since.
09-16-2003, 11:40 PM
#10
Senior Member
Join Date: May 2003
Location: Enumclaw,
WA
Posts: 669
Likes: 0
Received 0 Likes
on
0 Posts
RE: => No fear <=
I happen to read these postings about washout and tip stalling, and it made me realize that I needed to take a good look at the shape of my Gental Lady's wing...I found that it had washin(I guess that's what would call it) and a lot of it. I had flown it that day by hand tossing it in the local field and if I tried to turn it at slow speeds it would spin into the ground. I put about 1/4 inch washout into the tips and it has made slow flight so much better. -Thanks
I have since build a small high start with 30' of rubber and about twice that of string. It seems to work ok...I feel like I am just toying around, so just how long of a high start can I use with a 2M like Gental Lady? I am new to gliders...if you can't tell! I have one glow and one electic that DON'T fly right now, so here I am!
I have since build a small high start with 30' of rubber and about twice that of string. It seems to work ok...I feel like I am just toying around, so just how long of a high start can I use with a 2M like Gental Lady? I am new to gliders...if you can't tell! I have one glow and one electic that DON'T fly right now, so here I am!
09-17-2003, 04:50 AM
#11
RE: => No fear <=
scudrunner77
I am also new to RC flying and new to gliders. I started flying an Aerobird in March. I got my sailplane in July. I would guess I have about 40+ lunches on the sailplane.
Here is a great link for understanding hi-starts. I use this when I am explaining sailplanes to friends.
http://www.labyrinth.net.au/~learmont/HiStart.html
I have a Great Planes Spirit 2 meter. Similar in size and weight to a Gentle Lady. htttp://www.greatplanes.com/airplanes/gpma16.html
I have two hi-starts.
Practice hi-start/up-start
This one is a home made up-start with 25' of 7/16" latex tubing (1/16 wall) that I bought on e-bay. It is really stronger than what I need for this plane. I added 100 feet of pink mason's line that I bought at home depot. I made the parachute out of a pink golf hat. I use this one for practicing launches and landings. It would be better matched to the plane if the tubing was 5/16". I get a good but a little too powerful launch. This rubber is so strong that it has been used to launch 3 meter full house sailplanes with no problem.
I can get about 100-150' launch with this set-up. If there is a strong breeze, say 7 MPH, I add another 50 feet of line because I can get more of a kite effect and add 30-60 feet to my launch.
Big Hi-start
My main hi-start is from Northeast Sailplanes. It is their "Pinnacle Standard" model.
http://www.nesail.com/pinnacle.html
This Hi-Start has 100' of 1/2" rubber with a 3/32 wall. Again, this is really stronger than I need for this plane, but I bought it in anticipation of moving into larger planes later. This one can launch 3+ meter sailplanes with ease. It has 390 feet of hot pink line that is identical to the mason's line that I got at home depot. I get 400-500 launches with this one. I often approach the launches that others get off of the club winches. The more experienced pilots can really zoom off the top of the launch with this hi-start.
Keep in mind that I have a huge field to work with. Here is a picture of the field. http://www.lisf.org/Pictures/29070035.jpg
Our field is about 800' by 1600' so I can lay out a 500' hi-start, pull back 75-100 feet and have room to work. For the larger planes, they pull my hi-start back close to 200 feet and really send the plane up.
Hope this is useful info.
I am also new to RC flying and new to gliders. I started flying an Aerobird in March. I got my sailplane in July. I would guess I have about 40+ lunches on the sailplane.
Here is a great link for understanding hi-starts. I use this when I am explaining sailplanes to friends.
http://www.labyrinth.net.au/~learmont/HiStart.html
I have a Great Planes Spirit 2 meter. Similar in size and weight to a Gentle Lady. htttp://www.greatplanes.com/airplanes/gpma16.html
I have two hi-starts.
Practice hi-start/up-start
This one is a home made up-start with 25' of 7/16" latex tubing (1/16 wall) that I bought on e-bay. It is really stronger than what I need for this plane. I added 100 feet of pink mason's line that I bought at home depot. I made the parachute out of a pink golf hat. I use this one for practicing launches and landings. It would be better matched to the plane if the tubing was 5/16". I get a good but a little too powerful launch. This rubber is so strong that it has been used to launch 3 meter full house sailplanes with no problem.
I can get about 100-150' launch with this set-up. If there is a strong breeze, say 7 MPH, I add another 50 feet of line because I can get more of a kite effect and add 30-60 feet to my launch.
Big Hi-start
My main hi-start is from Northeast Sailplanes. It is their "Pinnacle Standard" model.
http://www.nesail.com/pinnacle.html
This Hi-Start has 100' of 1/2" rubber with a 3/32 wall. Again, this is really stronger than I need for this plane, but I bought it in anticipation of moving into larger planes later. This one can launch 3+ meter sailplanes with ease. It has 390 feet of hot pink line that is identical to the mason's line that I got at home depot. I get 400-500 launches with this one. I often approach the launches that others get off of the club winches. The more experienced pilots can really zoom off the top of the launch with this hi-start.
Keep in mind that I have a huge field to work with. Here is a picture of the field. http://www.lisf.org/Pictures/29070035.jpg
Our field is about 800' by 1600' so I can lay out a 500' hi-start, pull back 75-100 feet and have room to work. For the larger planes, they pull my hi-start back close to 200 feet and really send the plane up.
Hope this is useful info.
09-18-2003, 07:39 PM
#13
RE: => No fear <=
Thanks,
We like it. In fact we host the Eastern Soaring League this weekend. Here are photos from the last time we hosted the competitions in June.
http://www.shutterfly.com/osi.jsp?i=...21b3201794e4dd
We like it. In fact we host the Eastern Soaring League this weekend. Here are photos from the last time we hosted the competitions in June.
http://www.shutterfly.com/osi.jsp?i=...21b3201794e4dd
09-18-2003, 11:48 PM
#14
Senior Member
Join Date: May 2003
Location: Enumclaw,
WA
Posts: 669
Likes: 0
Received 0 Likes
on
0 Posts
RE: => No fear <=
Aeajr-
Great flying field you have....! Very nice! Is it managed by a club?
Thanks for the info on high starts. Looks like I need to add more line to the 30' for tubing I'm using to get a little more altitude. I do have a .061 Novel I was planing on strapping to the front. I don't think the weight would be a big deal because I have so much in the nose already, and can take that out. I do not know how much it will effect drag though... Flying a glider feels very different to me. The only other plane I have flown is a .40 size trainer with ailerons.. It's hard to believe how much altitude is lost when turning with the glider. I really like the added challenge of keeping the plane in the air, even if it is only for a few seconds.....
Great flying field you have....! Very nice! Is it managed by a club?
Thanks for the info on high starts. Looks like I need to add more line to the 30' for tubing I'm using to get a little more altitude. I do have a .061 Novel I was planing on strapping to the front. I don't think the weight would be a big deal because I have so much in the nose already, and can take that out. I do not know how much it will effect drag though... Flying a glider feels very different to me. The only other plane I have flown is a .40 size trainer with ailerons.. It's hard to believe how much altitude is lost when turning with the glider. I really like the added challenge of keeping the plane in the air, even if it is only for a few seconds.....
09-19-2003, 11:59 AM
#15
Member
Join Date: Jan 2002
Location: Santa Fe, NM
Posts: 51
Likes: 0
Received 0 Likes
on
0 Posts
RE: => No fear <=
If you are packing enough lead in the nose that it comes anywhere close to the weight of a .60, then you may want to play w/ that CG first.
The correctly trimmed / balanced Spirit should have the elevator prerfectly lined up w/ the bottom of the stab when she's floating along nice and flat. Check this after you've made a nice slow landing and see if the elevator isn't working (and adding drag) to hold up that extra lead.
One simple approach I heard was to go out and fly in calm air and continue to trim & take out lead a little at a time until she gets too squirelly, then throw a 1/4 oz back in and call it good. The guage this guy took was to time each flightl, fly the same pattern, and once the times from launch to landing start to increase, you just past YOUR best CG point.
Since you are losing a lot of altitude in your turns, it sounds as if she is packing a little extra nose weight. I fly the Spirit and she does not drop much on a nice gentle turn w/ minimal elevator (adds drag). My turns into the wind usually give me a nice boost because my airspeed increases and I can translate that into altitude.
Gluck, and IMHO, save the motor for an aileron ship to blast around w/.
The correctly trimmed / balanced Spirit should have the elevator prerfectly lined up w/ the bottom of the stab when she's floating along nice and flat. Check this after you've made a nice slow landing and see if the elevator isn't working (and adding drag) to hold up that extra lead.
One simple approach I heard was to go out and fly in calm air and continue to trim & take out lead a little at a time until she gets too squirelly, then throw a 1/4 oz back in and call it good. The guage this guy took was to time each flightl, fly the same pattern, and once the times from launch to landing start to increase, you just past YOUR best CG point.
Since you are losing a lot of altitude in your turns, it sounds as if she is packing a little extra nose weight. I fly the Spirit and she does not drop much on a nice gentle turn w/ minimal elevator (adds drag). My turns into the wind usually give me a nice boost because my airspeed increases and I can translate that into altitude.
Gluck, and IMHO, save the motor for an aileron ship to blast around w/.
09-21-2003, 11:00 AM
#16
Senior Member
Join Date: May 2003
Location: Enumclaw,
WA
Posts: 669
Likes: 0
Received 0 Likes
on
0 Posts
RE: => No fear <=
I will check the CG before I fly again...I thought it was strange that I was loosing as much altitude as I was by just turning. I am new to gliders and didn't know
what to expect. Thanks for the info!
what to expect. Thanks for the info!
09-21-2003, 03:38 PM
#17
RE: => No fear <=
Great flying field you have....! Very nice! Is it managed by a club?
09-21-2003, 03:42 PM
#18
RE: => No fear <=
I will check the CG before I fly again...I thought it was strange that I was loosing as much altitude as I was by just turning. I am new to gliders and didn't know
what to expect. Thanks for the info!
what to expect. Thanks for the info!
Now it doesn't pop off during launches.
I ahve about 4.5 oz of lead in the nose. and mine floats along nicely.
09-22-2003, 12:09 AM
#19
Senior Member
Join Date: May 2003
Location: Enumclaw,
WA
Posts: 669
Likes: 0
Received 0 Likes
on
0 Posts
RE: => No fear <=
I found that if I have some up trim in my Gental Lady that it will pop off the high start as well. I have launched it with no or slight down elevator trim and this helps a lot. Pitch control seems sensitive while zipping up with the high start...so I try not to have to make to many inputs on the way up.
I did have too much weight in the nose.... I took some out and it seems a little better.
Got it up in a thermal off my little hight start! First for me...a hawk even joined it for a few minutes. Wish I had a camera with me!
I had to call it quits for the day when my rudder servo got real sluggish and would not return to center....an old Futaba FP-S133, I put in a Hitec HS-85bb+ when I got home and it is so much better than the still working Futaba for elevator that I might have to get one for it too.
I suspect that the rudder servo was under too much load. When it pushed the rod for right rudder, the rod would flex. When I put the hitec servo in I took some throw out of it and I get almost the same rudder movement with very little flex...
I did have too much weight in the nose.... I took some out and it seems a little better.
Got it up in a thermal off my little hight start! First for me...a hawk even joined it for a few minutes. Wish I had a camera with me!
I had to call it quits for the day when my rudder servo got real sluggish and would not return to center....an old Futaba FP-S133, I put in a Hitec HS-85bb+ when I got home and it is so much better than the still working Futaba for elevator that I might have to get one for it too.
I suspect that the rudder servo was under too much load. When it pushed the rod for right rudder, the rod would flex. When I put the hitec servo in I took some throw out of it and I get almost the same rudder movement with very little flex...
09-24-2003, 10:33 PM
#20
Senior Member
Join Date: Aug 2003
Location: Austin, TX,
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
RE: => No fear <=
I too have a Spirit, but the Spirit Elite. I have found that when turning (with the ailerons) that the plane would start to nose down. Probably similar to what some of you are also experiencing (if you have an aileron plane.) This is caused by the aileron differential being off. In other words, then ever you turn left your right aileron goes down and your left goes up. If your plane is pulling down in the turn you probably need to add more differential (in other words the right aileron will go down more to balance out the drag from the left aileron.)
Likewise if your plane tends to pull up and stall in a turn you need to decrease the aileron differential.
I have found that my Spirit enjoys the tip stall as well. Tip stalls generally occur when you have your plane at a slow flight speed and attempt to turn. Say you turn left. The left wing slows down relative to the right wing in the turn (ie. think of the turn as a circle. your speed at the outside of the circle is faster than the speed at the inside.) This speed difference causes the right (or outside) wing to increase lift relative to the inside wing. When you're already moving at close to stall speed this can be a problem. The inside wing will essentially "lose lift" and since the outside wing is still above stall speed the plane will be thrown onto its side...which we call a tip stall.
If you're experiencing your tip stalls at a speed relatively high above stall level then you probably have a wash out problem as discussed.
Good Luck!
Thermals!
Jared
Likewise if your plane tends to pull up and stall in a turn you need to decrease the aileron differential.
I have found that my Spirit enjoys the tip stall as well. Tip stalls generally occur when you have your plane at a slow flight speed and attempt to turn. Say you turn left. The left wing slows down relative to the right wing in the turn (ie. think of the turn as a circle. your speed at the outside of the circle is faster than the speed at the inside.) This speed difference causes the right (or outside) wing to increase lift relative to the inside wing. When you're already moving at close to stall speed this can be a problem. The inside wing will essentially "lose lift" and since the outside wing is still above stall speed the plane will be thrown onto its side...which we call a tip stall.
If you're experiencing your tip stalls at a speed relatively high above stall level then you probably have a wash out problem as discussed.
Good Luck!
Thermals!
Jared
10-07-2003, 05:24 AM
#21
RE: Tip Stalling and Wing Washout
I regret to report that, while learning to use a winch, my original spirit was destroyed in a bad launch this weekend so I am going to build a new one from a kit.
If you have any building advice, I have posted a request for advice here:
http://www.rcuniverse.com/forum/Spir...1185655/tm.htm
If you have any building advice, I have posted a request for advice here:
http://www.rcuniverse.com/forum/Spir...1185655/tm.htm
10-21-2003, 05:23 PM
#23
RE: => No fear <=
Sheeting the outer leading edges on the Spirit is easy. I removed the covering, and added on 1/32" sheet back to the spar on top. Nothing on the bottom. Then re-covered.
Haven't flown the plane deliberately into tip-stall conditions, but it is a good sloper.
It had stalled out of steep turns in low thermals, haven't seen like that since.
Haven't flown the plane deliberately into tip-stall conditions, but it is a good sloper.
It had stalled out of steep turns in low thermals, haven't seen like that since.
If I was going to add sheeting, as you mention above, where would I add it?
10-21-2003, 11:28 PM
#24
Senior Member
Join Date: Aug 2003
Location: Austin, TX,
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
RE: => No fear <=
I would extend the D-tube all the way to the edge of the wing. This is how my Elite's wing is built. I'm actually suprised that they don't come that way from the factory! But if I were to do it I would go clear from the dihedral break all the way to the tip...top and bottom...
That doesn't look like that bad of a crash
is this all the damage that was done?
Averen
That doesn't look like that bad of a crash
is this all the damage that was done?Averen
10-22-2003, 12:09 AM
#25
RE: => No fear <=
You asked about damage:
The left wing is worse than the right. I will have to cut some new ribs. I had to cut away some of the sheeting, not shown in this photo, in order to reveal more of the internal damage. The left wing will take a lot of work, especially since I have never done this kind of thing before. Remember I bought this plane RTF.
The nose of the fuse is all smashed, but I think I can fix it.
The left wing is worse than the right. I will have to cut some new ribs. I had to cut away some of the sheeting, not shown in this photo, in order to reveal more of the internal damage. The left wing will take a lot of work, especially since I have never done this kind of thing before. Remember I bought this plane RTF.
The nose of the fuse is all smashed, but I think I can fix it.