<div style="margin: 0in 0in 0pt">The powers to be at our club have released the events list for this year&rsquo;s club fun fly. If it&rsquo;s still alive by then, my Twist 40 should be a good plane for the events except for one&hellip; Climb and Glide. No problem climbing out for 30 seconds but the deadstick glide performance is less than stellar.</div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt">Looking at the plane was wondering if I can&rsquo;t drop the ailerons like flapperons but just slightly to create more lift without a significance increase in drag.</div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt">I&rsquo;ve thought about this from several angles and figure the only way to find out is play with the Tx programming and do some test flying. However I&rsquo;m hoping to shorten the learning curve here and get some opinions.</div>

I see no negative consequences by doing that.

I suggest to experiment with more than just slightly flaperon deflection, may be up to 20 degrees.
You may need to mix some elevator up due to the new pitch roll.

Experiment high enough first and watch for tip stalls.

I hope you can make it a mode in one Tx switch just for this particular competition.

Regards!

I think some flap might help, too. Also, don't just fly the thing to the ground, pay attention to the airplane for signs of lift. If one wing rocks up, turn into it!

I will wager  that NO amount of flap fiddling will help the  glide. BUT if'n you could use a folding prop -that would help a wee bit.
  flaps add  LIFTNDRAG
 thats one item and there is no way to pull it apart.

Dick, up to a point they add more lift than they do drag.  This is why sailplanes use "variable camber" which is just adding a bit of flap.  Selig and his band of merry assistants even tested some of their airfoils that were intended to use camber changing with lift drag charts for various flap angle deployments.  But the key is a low angle.  We're only talking up to MAYBE 10 degrees for the Selig airfoils.  For a fat symetrical airfoil a few more degrees up to perhaps 15 degrees would not be out of the question. 

Billygoat, get out and try it with various angles to see what the effect is.  And don't discount the thermal aspect as mentioned.  It's not much but if you can find one and stay in it you may delay the arrival for a significant time even if all it does is slow down the descent.

Take a good look at  a TWIST 40
 I really do not expect to see any  improvement with  varied aileron settings.
  low angles are the  key,-  Of course -for  ANY decrease in drag
 setting the CG aft to max controllable  location  -lowering weight  and using minimum diameter prop-  are likely the most produtive approaches

I truly appreciate the input so far. My original thinking on this is in line with Dick&rsquo;s, that any lift generated by flaps will be negated by drag.

For arguments sake let&rsquo;s say lift and drag increase equally with flap deployment but let&rsquo;s also say the addition of flaps also adheres to the third factor&hellip; Decreases the stall speed. If I&rsquo;m thinking this through correctly, glide ratio over distance should not improve. However I&rsquo;m only trying to increase glide ratio over TIME. Shouldn't this increase if the plane flown just above stall speed?

Do you have to use the same plane for all events?  Otherwise about the only thing that will improve the Twist is a better wing (much more span).  Or you could add tip plates and hope for the best.  But all the Twists that I have flown drop like bricks.

Negated if you don't know how to use the throttle.

Flaps are used day in and day out to improve landings. Of course, full scale boys know that the throttle still works until they shut down the engines.....

Too many of us in modeling try to figure out all our problems and issues with just one thing. We seem to need one-liners. Most problems don't have just one answer that's one dimensional.

Glider flyers (at least some of them) know that duration comes from efficiency.  There are three possibilities.   Longest distance.  Longest duration.  Longest distance.  They get each with a different technique for each.

They know how to get whichever one they want/need.   But they don't have a throttle to use.

In gliding, best duration comes at a speed that glider flyers call "minimum sink" speed.  That's at approximately 1.2 times the stall speed.  That will vary up or down, of course, depending upon the wing's design and whatever flaps are deployed.

For models, you can only do the best you can.  The "minimum sink" speed will be just a bit above the stall.  You can only get approximations, so your best bet is to set a speed with the elevator trim and hand-off the elevator stick.  Be careful with turns because they will make the model sink faster...only very shallow ones to keep sink to a minimum.

To get a good handle on the correct speed, you'll need to make a number of flights with different settings.  If you have someone with a model rocketry range finder, you can get to the same altitude each time and get a good idea of the sink rate.  You should  be able to eventually find the elevator trim setting that will give you the minimum sink.

Hi BillyGoat,

Deploying flaps (or flaperons) increases the coefficient of lift (CL)and the coefficient of drag (CD)of the wing; these are the two characteristics of the wing's performance you would be looking up, if there were a bunch of data available, which is probably not the case. Because the ailerons of the Twist 40 are full span and have a long
chord, they will have a significant effect when deflected. It is generally the case that small deflections of flaps increase CL more than they increase CD. Because of this engineering observation, we need to recognize that lift and drag can be "pulled apart" to a significant extent.

To predict the effect of using your ailerons as flaperons, you need to consider the energy. When you climb your plane to altitude, you are adding potential energy, and this is the energy that you have available for your descent. Aerodynamic drag will be bleeding this potential energy away, until it is completely gone, and you land. The rate at which the potential energy bleeds off is proportional to the CD times the cube of velocity. This means that if you increase the CD by 10%, you would lose energy 10% faster. If you decrease the velocity by 10%, you would lose energy 17% slower, everything else being equal. The main lesson here is that reducing your stall speed by increasing the CL seems to be much more effective at 'saving' energy than reducing CD. If you do the math on the lift side, it works out that a moderate deflection of flaperons should give you a decrease in velocity that more than compensates for the increase in CD.

I think this is enough justification to program your radio and give it a try. You probably want to start with small deflections.

banktoturn

Excellent explanation, Banktoturn!

For the same reasons just explained, the programmed mode should be on only during the glide phase, not during the climb.

The smaller prop propossed by Dick is another great idea.

<p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><font face="Times New Roman" size="3">Thanks for all the input. Certainly enlightening. </font></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt">

<font face="Times New Roman" size="3"> </font></p></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><font size="3"><font face="Times New Roman">After flying the event several times with the help of a buddy on the timer and no special programming, my results were quite varied. It's going to be very difficult to measure sink rates of various settings visually and in an uncontrolled environment. <span style="mso-spacerun: yes"> </span>Some flight test at various setting are certainly in order but unless flapperons dramatically increase glide duration, I can see right now results are going to be impossible to determine without extensive testing and charting averages. Since bragging rights are the only thing on the line, I don’t plan on getting too involved in this. </font></font></p>

I suspect some of the lift theorymentioned is based on design parameters totally UNLIKE the TWIST
If you can't reduce weight aft CG. n a low drag propis about the only hope
Take a look at the planform- it is a great aerobatic setup -one of my favorites
the aspect ratio is about 4.something to 1
this means the airflow moves heavily toward the tips
I always used a rule of thumb that the "tip" span was equal to the tip chord -on a setup like this
this means the tips are1/2 of the the wing.
In that air follows the path of least rsistance ,
(try and change THAT one) the best bet is lowest possible angle of attack.
this may mean letting the model speed up a bit more than you might think
tha aft cg (the more aft the merrier) increases total lifting area and if you can be gentle on the elev , ithas to help.
going for tip platesis probably a no nofor the contest .
I am no good at theory or math (Ionly have five toes so base ten is out)but )I found that tip plates can work on stubby wing setups -and work very well

None of the theory mentioned is specific to a particular type of wing. The question is essentially whether this wing would benefit from some camber for the power-off glide. It seems pretty likely that zero camber is not ideal for this task, and the TWISTwing is configured appropriately for meaningful camber variation (full-span ailerons with long chord). Moreover, the low aspect ratio makes tip stall fairly unlikely.

Decreasing drag could only help, but I wonder whether a folding prop could be found that would be a good choice for the other tasks.

banktoturn

Have you flown many models with this type planform?
It really is very good
a fellow named Wittman used it on racing planes as well as efficient sport planes etc.
It is lousy for gliding as the air simply moves side ways easily (easiest path) But one can hold full elevator and the model will sink -like a parachute .
very very reluctant to ever get into the same problems as lhigher aspect ratio stuf which can easily get one panel lifting more than the other -in a skid, etc..
We have done coupled flaps on these and the turning abilities improve BUT the increased drag requires more power to do the improved ,smaller radius maneuver
just something to gnaw on -