70cc FLEX Ultimate assembly thread.

[Snoopy1]

After getting the 2 wing halves to fit I was looking at how to get the 2 servos in the top wing connected to the receiver. We’ll it ended up the run from the servo to the receiver is over 36 inches. So because of the length and 2 connectors between the servo and the receiver I decided to add a servo booster to the 2 servos in the top wing.

 

[TonyHallo]

I don't know if I should like that or not!

 

[TonyHallo]

Do you believe this 70cc bird will need these?

After getting the 2 wing halves to fit I was looking at how to get the 2 servos in the top wing connected to the receiver. We’ll it ended up the run from the servo to the receiver is over 36 inches. So because of the length and 2 connectors between the servo and the receiver I decided to add a servo booster to the 2 servos in the top wing.

View attachment 123569

 

[Snoopy1]

Do you believe this 70cc bird will need these?

It’s not the size of the plane it’s length of wire from the receiver. Ok there is more to it also depends on the servo that is on the end of the extension. Fist is it a fast servo, it is over 400 oz and a 2K-hertz up date time and it is digital. So when it is asked to move quickly the voltage will drop, by how much is always debated, but it will drop and it also depends on how many servos are being asked to move at once. so it depends on bunch of conditions. So over the years and building a few bigger planes and noting some anomalies after adding a booster it fixed the problem. The one time was in a 100cc plane with some high powered servos in a very windy day and the plane had a Demon Cortex gyro in it, It did some strange things. After talking to some radio experts they recommended a booster and I believe it solved the problem. So as a rule I add a booster at 36 inches and a couple connections the voltage can see a reasonable drop at the servo.

 

[Snoopy1]

I don't know if I should like that or not!

Have to say up and till the top wing I was very pleased with everything and everything was going well the finish and quality of plane is great.

 

[TonyHallo]

Just wondering what batteries you use?

 

[Snoopy1]

Just wondering what batteries you use?

You have been around for a while you do ask the correct questions or I should say build many planes and seen it all.
Ok, batteries over the years I have had my share of difficulties with batteries, because of that I have purchased a full computer battery testing system.
My understanding of batteries and experience is as follows now all this only started when I started building planes bigger than 50cc and high powered digital servos.
1 First lesson large capacity batteries do not necessary work or solve voltage drops.
2. Do not use batteries labeled as RX batteries they have no punch and can have big voltage drops.
3. Use batteries that have at least 35C rating much better punch and a lot less voltage drop.
4. Always use 2 packs and no less than 3500mAh.
5. Use Power Box HD wire.
6. Keep good track of the IR on the individual cells of a battery pack. When one cell goes off the battery just loess it’s ability to push amps.
7. Do not use voltage regulators.
8. Run 2S LiPo at full voltage and use no less than XT 30 connectors.
When abiding to the 8. points above I believe I solved my voltage drop problems or I should say haven’t had problem since.
Ok Tony what are your thoughts of my experience.

 

[TonyHallo]

Well you answered all the questions I would have ask. Attached is my Champ's telemetry log from the NASA scale contest back in September 2024. RB1 and RB2 are the each battery voltage at the redundancy buss and RXB is the battery voltage of the selected receiver, there are three receivers. The receivers are only satellites, no servos are attached. Collecting the data at .1 sec intervals. The Champ has two 2100 MA maybe 10C LIPO batteries, the batteries are 2S3P packs that fit under the seat and were sold by Hobby King as receiver packs, never measured the voltage at the servo but in the Champ's case the aileron servo leads are probably over 6 foot long, they are routed under the cabin floor, then up the back to the wing rib, then forward to about the high point of the wing,then out about 3' to the servo. Normally use Hitec D945TW servos that are wide range voltage, coreless motors, 320 in oz torque, not worry about the speed because the plane is going rather slow. I'm happy with the battery performance and recently looked to buy another set but they don't seem to be available any longer.

 

[AKNick]

You guys are getting technical, I like it. Why no less than 2x 3500? I’d rather use lighter packs and switch them out more frequently (couple flights). Do they just maintain a higher voltage longer?

The fit on those wings… sheesh. My 120” Turbobushmaster needed some sanding with the wing tube fit - so not perfect either.
The mamba has a pretty good rep, Its always been a plane id like to have, but can’t have them all! Disappointed I never saw one fly at Joe Nall! Lots of the Flex edge 540s - the new schemes on those are killer.

 

[Snoopy1]

@TonyHallo I get good feed back from voltages at the receiver but not at the servo. When I was really into at one time I was monitoring the voltage at the last connection before the servo that is when I noticed up a 2 volt drop. And also checked voltage drops across a small JR 3 pin plug seen up to 0.6 volt drop. If you want to do something interesting just run a 7.4 volt 5 amp load across a 3 pin JR connector for 5 minute. It really gets quiet hot.

@AKNick you are correct power wise a 2200 will do fine as long as you do not do to many flights And have at least 35c pack, On my bigger planes when I have 8 big powerful servos going for 10 minutes I can use up to 600 mAp per flight so 3 flights and you are up to 1800 on a 2200 pack that is close as I would like to go. Down to around 30%.