Trailing edge camber adjustments - Best Practices?

[aeajr]

I have been flying thermal sailplanes about 2.5 years and full house for a little over a year.

I have not played with camber settings yet. My Futaba 9C can handle it so I guess it is time. I am asking about best practices and practical experience.

I just put up an Prism T-tail with a SD 7037 air foil. So far I like the plane a lot. Now I am trying to dial it in and figure out what settings work best.

When you talk about applying full TE camber, how much are we talking?

Is full TE camber better than just adding a little flap?

I can put this on a side slider, a dial or I could put this on a switch and go to one or two presets. What would be the recommendations here.

Should I be using full TE camber adjustment as soon as I confirm lift, or are there times when it should not be used?

I appreciate any guidance.

My questions are general, but if you have any specific suggestions on how I implement this on my Futaba 9C, that would be appreciated as well. Today I have crow on the stick ( no choice) flap/elevator on left slider. I was thinking of putting this on right slider but it could go on a 2 way or three way switch as well. I don't typically use the dials.

Thanks! :)

[rdwoebke]

I'm not expert on full house planes by any means. But I am planning on following some of the suggestions in this thread when I get a full house plane again.

http://groups.yahoo.com/group/soaring/message/133159

[erikdahlchriste]

Hi Aeajr,

http://www.gliders.dk/triming_and_setup_of_a_glider_wi_eng.htm

cheers

Erik Dahl Christensen
Denmark

[Robglover]

The 7037 does benefit from changes in camber. If you want to go fast reflex it. If you want to slow down add camber. How much and when is up to the pilot. Better pilots know their planes well enough to decide when to add what. That's how we pick who wins the contest. There are some general rules, but the best rule is to try it and see what works for you. This is easier to do if you like to fly a lot.

happy trails

[Hostage-46]

To Rob's point, it really is about knowing when and how much to use camber and reflex. Like you aejr I'm just getting to the point where I've been experimenting. My current full house ship, a 7035 sage wing Sapphire, seems to like camber more then reflex. My XP-4 was designed to leverage camber and reflex to optimize performance.

I find it interesting that most folks tend to user sliders to vary camber. In full scale soaring, you generally select a particuar setting that will yield the known airfoil polar, which is why it seems like a switch, with a given,consisant setting makes more sense.

I continue to noodle through both options, slider vs. switch.

[aeajr]

I think a switch seems much simpler but I don't know if we are talking 1/16 inch or 50% or what the range should be. I am leaning on putting on a slider to experiment and once I find what seems to work, move that to a 2 way or 3 way or a flight condition switch.

[nuevo]

When you talk about applying full TE camber, how much are we talking? 2-3 degrees down in general

Is full TE camber better than just adding a little flap?yes. Full TE camber, all surfaces deflected so the TE is still straight.

I can put this on a side slider, a dial or I could put this on a switch and go to one or two presets. What would be the recommendations here. Use whatever suits you best. Not a big issue here.

In the last year, I migrated to using my flight-mode switch for different camber positions. That is because I'm flying airplanes where the airfoil designer has designated specific positions for thermal, cruise, launch, speed, etc.

On one plane, the designer has not given such information, so I experimented with xfoil to find what I believe is the best location. To compute the "best" angle for thermal, etc. you would need to compute the % hinge location on your plane, and then use xfoil or Profili to generate polars for the Re and surface deflection angles you are interested in. Then compare the polars. Using this technique takes quite a bit of study, knowledge, estimating, and insight on your part.

Profili (http://www.profili2.com/) is a lot easier to use, but I find myself using xfoil (http://raphael.mit.edu/xfoil/) directly more often.

I'm not solidly on the "switch" side, and can see the advantages of both.

[aeajr]

Hi Aeajr,

http://www.gliders.dk/triming_and_setup_of_a_glider_wi_eng.htm

cheers

Erik Dahl Christensen
Denmark

Erik, I have seen your paper before. It circulates at our sailplane club often. Thanks for sharing it. ;)

[aeajr]

I'm not expert on full house planes by any means. But I am planning on following some of the suggestions in this thread when I get a full house plane again.

http://groups.yahoo.com/group/soaring/message/133159

A discussion by Joe Wurts around setting up a sailplane and computer radio is about as good as it gets. Thanks!

[Robglover]

Joe's stuff is pretty much gospel to me, hard to argue with his success.

Camber presets are working well for me the last year or so, for a couple reasons.

I think that the recent crop of airfoils were designed to have a couple sweet spots. One for high camber, and one for low camber settings.

If you lay a stainless steel rule down on the top of the airfoil and flex it to follow the wing surface it helps you to visualize smooth and kinky flow paths. Camber the wing just right you can spot when you have a good smoothly curved upper surface. This will likely correspond to the thermal setting.

If you do the same on the lower wing surface you should get pretty close to the best low camber setting, good for runs between thermals.

Set the presets to get your wing to those two spots and then ignore the slider, instead focus your attention on keeping the plane centered in lift. Flying smoothly in lift will trump whatever you do with camber settings.

[Hostage-46]

Joe's stuff is pretty much gospel to me, hard to argue with his success.

Camber presets are working well for me the last year or so, for a couple reasons.

I think that the recent crop of airfoils were designed to have a couple sweet spots. One for high camber, and one for low camber settings.

If you lay a stainless steel rule down on the top of the airfoil and flex it to follow the wing surface it helps you to visualize smooth and kinky flow paths. Camber the wing just right you can spot when you have a good smoothly curved upper surface. This will likely correspond to the thermal setting.

If you do the same on the lower wing surface you should get pretty close to the best low camber setting, good for runs between thermals.

Set the presets to get your wing to those two spots and then ignore the slider, instead focus your attention on keeping the plane centered in lift. Flying smoothly in lift will trump whatever you do with camber settings.



Once again .... very useful thread. I will look at the plots but the steel ruler appoach is genious in its simplicity.

Something we've grown to expect from you guys. How in the world did people survive before RCSE and RC Groups :)

I've also gone to the mode switch approach as I'm not able to otherwise tell the difference because of my experience level.

[Kestrel]

Hi Ed,

I have a Sapphire with the 7037. I have it set up on the new 9C Futaba. Ed Whyte's suggested settings for the model is 1/16" reflex, 3/16" camber and I believe it is 1/2" drop on the flaps and 3/8" drop on the ail for launch. These settings may need some elevator compensation. Especially the launch settings.

What I have settled on is:

1/16" reflex with no elev. compensation.
The launch settings as listed with elev. compensation.
My camber setting is at about 1/8" with a very slight amount of elev.

I don't use any of the knobs. I have the launch, camber and reflex settings set up on switches. I also set up the camber on the left slider. Basically, I set up the slider, as you had mentioned, to be able to "play" with the amount of camber to see how the model reacted. After a while, it seemed as though I was always coming to the same setting on the slider. So, I decided to set the camber switch up with the setting that I was arriving at with the slider. I am sure that there are pilots out there that like to be able to vary the setting. But for me it is a lot easier to flip the switch on and off as needed rather than to fiddle with the slider. Using the slider, you have to mover it till it beeps to find center. Count the clicks needed. Then move it to the beep again. The switch is a lot more convenient.

When doing the testing of the set ups, I would set the camber or reflex up on the slider and then use the elev. trim to adjust elev. compensation. After I determined how much if any elev. was needed, I then set up the elev. on the switch too.

I have also been playing with flaps coupled to elev. a little. Not sure if I like it yet or not. There are some situations where it works very well. It is activated by a switch, so I can turn it on or off as needed.

PS:

On the slider. Since reflex is set at 1/16" and really not varied, I have "0" setting programed on the up side of center and the camber set up when moving the slider down. This way I can park the slider in the all the way up position when not in use. Helps to keep from making an accidental trailing edge adjustment.

Since the adjustments are now set on the switches, I really don't use the slider much.

BTW, I really like the 9C Super Series.

Duey