Electric Wright Stuff B

[coachchuckaahs]

I have one question about flight turning. My airplane turns to the right when it starts and goes up. Then in the middle/almost top of height, it changes turning direction. I wonder why it changes turning direction and which part should be trimmed. Thank you very much

Please provide Coach Brian with the information requested to get more help.

Generally this is caused by competing trim adjustments. Coach Brian points out that excessive wash-in can cause this. We have seen little need for any wash-in this year, and in fact a plane that banks in may have advantages in climbing slower. Generally wash-in will convert excessive bank (zooming in circles) into climb, but if you are already struggling with too much climb, a zooming circle may be used to benefit.

There are a number of things that impact circle, some at different speeds. We generally set up a left circle (J&H seems to like a right circle on their electric planes). A left circle is driven by the large props in WS that will favor turning left. This is less of an effect on the small EWS props.

The following factors affect the circle. They all affect the circle throughout the flight, but some have greater impact at high torque. (My comments are for a left turn)

• Stab tilt: Generally more impact at slower speeds, later in flight. Left stabilizer tip higher than right, typically 5-10mm difference
• Tailboom or rudder offset: More impact at higher speeds. Generally if the angle is set at the motor-stick to Tailboom joint, about an inch of offset tot eh left will encourage a left turn. Note that some kits have NO offset! I have found this leads to ambiguous turning that you have noted. If your tailboom is straight and not easily adjusted, and you have tip fins on the stab. you can unglue (cut) the REAL joint of the stab to the TB, and move this to the left side about 3mm, thus imposing some left rudder. If your plane has a single vertical fin in the middle, you can try bending in some left rudder (if balsa), or reglue it on with a shim to induce left turn
• Motor thrustline: Highly speed dependent. Normally this will be at 0 on EWS, but if your motor is poorly mounted you may have induced some high torque turn in the wrong direction. You can shim the motor to ensure 1-2 degrees (very small) of left thrust.
• Wing wash. We can increase the left wing incidence by twisting the wing so the left LE is higher than the right LE, in order to reduce undesired banking. However, this can also increase drag substantially, and give strange yaw issues. I would stay close to 0 on wash-in. If intentionally added, keep it to 1-3mm difference. "Measure" by sighting the LE from the front, compared to TE. Wing wash is more effective at high speeds, but adds drag to the whole flight.

All of this assumes your plane is straight to begin with. Make sure that your tail has no wash-in or out (LE and TE are parallel), that your wing is line dup with your motorstick, etc.

It is likely that you have one or two parameters favoring a left turn, and others favoring a right turn, and they fight each other all flight.

Coach Chuck

[cctl29]

Hi Coach Brian,

Thank you very much for your suggestion of using varied prop.'s and testing for voltage. I am probably missing the obvious, but how can we test capacitor voltage if our plane is not equipped with a switch? Our setup is once the battery charger is unplugged, the motor starts running. Thank you very much in advance.

[coachchuckaahs]

The latest version of the J&H charger, without switch, has a connector in one of the leads form the battery. If you disconnect this, it stops charging (disconnects battery form capacitor), but the jack is still plugged in to the switch/jack combo on the plan, isolating the motor from the capacitor.

In this scenario, the cap is charged and not yet connected to the motor, and you can measure the voltage at the cap. If you do not have a connector in the line to the battery, GET ONE!

I suppose you could remove one battery form the holder to stop the charging, but this may be difficult.

Coach Chuck

[cctl29]

Hi Coach Chuck,

Thank you very much for explaining the connector on the charger lead. That makes sense. Unfortunately our charger does not have such a connector. Too later for us to buy a new charger.
Is there an easy hack to achieve this? Thanks!

[coachchuckaahs]

Yes. Solder in your own connector.

You can use a 2-prong connector such as https://www.amazon.com/eBoot-Connector- ... B01M5AHF0Z, though some of these might be a little tight for quick plug and unplug. This is actually what we used. You likely can find similar at a local hobby store

Any 2-pring mini connector would work.

Or you can fashion a single-lead connector, like J&H does, using something like this: https://www.amazon.com/Breadboard-20-Mo ... B07XMH2K4M. You may be able to get one such lead from your electronics team (detector builder or other similar), anyone with a breadboard. Or if you have an electronics shop in your school. If you get a male-female lead, cut it in half and solder each half in to one of the battery leads. For safety, put the female end on the lead going to teh battery, so it is not exposed.

If all else fails, find a small connector (1 or 2 lead) at Autozone.

Coach Chuck

[cctl29]

We noticed this pretty consistently with either glide or flying at reduced power - our two planes both exhibit stalling at very low speed, at about 3 feet above the floor. Wondering what areas we should look into to trim?

Another question on fast ascending - is that mostly because of the weight of the plane if everything else more or less equal? Our other plane is a little bit heavy and we don't notice the fast climb.

[coachchuckaahs]

I would have to see video on what you are calling "stalling", to be sure. If the motor is truly out of power, the character of flight does not really matter (I do not do glide testing). But if it is just stalling at lower power, it is a trim issue, reduce your incidence a mm, or move your CG forward a few mm.

Weight will impact the climb for sure. However, the power system likely is your issue. If you are not releasing the plane within 1/2 second of starting the motor, you are missing a large amount of climb. If your prop is not well matched to your motor, it may lack power. To get more power (unless already overloaded), increase the prop a bit (preferably more diameter rather than more pitch, though either will increase the power). However, if you have already loaded it down to 1/2 of unloaded RPM in the air, then loading more will only reduce power and more so reduce duration.

Please indicate your power system details. What motor? If J&H, what version? (There have been several). Resistance of the motor will tell a lot. Prop source, diameter, and if possible pitch.

Some early prop/motor setups were very sensitive in terms of climb. The latest high efficiency setup from J&H, with a 3.3 ohm motor and 65mm prop) is much more forgiving

Coach Chuck

PS: While in rubber-powered flight we generally trim our planes very close to stall on the letdown, the EWS class appears to benefit, in some cases that I have seen, to fly a little faster than one would like in rubber power, so it may set up with a little less incidence for best times. Only your log and stopwatch can confirm. This also can help control the climb when you are running an motor setup that climbs too much. Generally you want to trim for most efficient letdown, not the climb, because the plane spends more time in cruise and letdown.

[iflycheeseburger]

Thank you very much, coach Brian and coach Chuck. The information you shared are very helpful, especially using numbers as the reference. Sorry I don’t know how to reply following your previous post.

Coach Brian, I use zapper kit. Following the general instructions, the recommendations is airplane to turn left by tuning the tilt of the tail. But to make it turn left from glide test, I need to tilt tail a lot, thus I choose the right turn from glide test. After power on, it does follow the turning direction as glide at the beginning, but in the middle of flight, ~20 seconds flight, it either go straight to hit the wall or turn to opposite direction/left direction. This makes flight end to the wall/out of control:( I remember the tail tilt control direction with power, but front wing twist to control no power/later part glide direction. But I don’t know how to control or adjust front wing twist in zapper. Maybe there are some way to trim I didn’t realize. In the flight test, I can adjust tail wing twist or front wing shim.
I need more time to measure the airplane parameters to measure the offset/ twist etc.

[iflycheeseburger]

Coach Chuck, Thank you very much again for the details to address all my questions. I will try all your tips in the coming test.

[coachchuckaahs]

Thank you very much, coach Brian and coach Chuck. The information you shared are very helpful, especially using numbers as the reference. Sorry I don’t know how to reply following your previous post.

Coach Brian, I use zapper kit. Following the general instructions, the recommendations is airplane to turn left by tuning the tilt of the tail. But to make it turn left from glide test, I need to tilt tail a lot, thus I choose the right turn from glide test. After power on, it does follow the turning direction as glide at the beginning, but in the middle of flight, ~20 seconds flight, it either go straight to hit the wall or turn to opposite direction/left direction. This makes flight end to the wall/out of control:( I remember the tail tilt control direction with power, but front wing twist to control no power/later part glide direction. But I don’t know how to control or adjust front wing twist in zapper. Maybe there are some way to trim I didn’t realize. In the flight test, I can adjust tail wing twist or front wing shim.
I need more time to measure the airplane parameters to measure the offset/ twist etc.

Cheeseburger:

Based on your account, I suspect that kicking in some rudder by offsetting the tail to the left is needed. Usually wing twist (wash-in) is a finer detail to control roll-in during high power.

If I am understanding your post here, I think you have it backward. The tail tilt has effect all flight, but is the dominating trim feature at slower speeds (lower power). The rudder offset and motor thrustline offset (if any) affects the higher power portions of the flight.

I would look at adding rudder offset, either by cutting and shimming the joint at the tailboom to motorstick, or cutting the rear joint of the stab to the taillboom and moving that to the left about 3mm to start.

Then start with low power flights (I don't get a lot from glide tests), perhaps 2V charge, to see what late-flight looks like, and work up to full charge incrementally. This can help separate the various trim issues.

Coach Chuck