Date: 201601
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Icing; Thunderstorm; Turbulence
Light: Night
Aircraft: Regional Jet 900 (CRJ900)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: Long story short; we took off with the wrong flap setting of 8 [when it] should have been 20.The first factor is my FO. He's a great guy; but he's really behind the airplane. He's missing flows and very very slow on getting checklists done. I took this into consideration and always try to give him time. It just seems it's never enough. So; at the gate; I knew we were going to get Runway XYC to fly to airport ZZZ. I put in the numbers for XYC ; XYC [intersection takeoff]; and XYR. When we pushed off the gate; they told us to expect XYR. So; we changed everything and bugged it. We taxied out and contacted Ground. They told us to expect XYC now. So; we changed everything again and bugged XYC.We're taxing down Runway XX. I saw no line and I know he needed time. So; I asked for delayed engine start and we cranked engine #1. In my opinion; my FO just looks lost. And I'm trying to help him. This is day 2; leg 2 of 4. It's night; bad weather; etc.We turn on [the] Taxiway to head to XYC. I ask for 'Airport Runway XYC; flaps 8 taxi checklist'. He reads it to me; albeit very slow. Tower comes on and asks why we are taxing so slow. He's flustered. I say I'm giving my FO time to run a checklist. Tower instructs me to pull into XYC intersection taxiway to let a MedEvac airplane behind me takeoff.No problem; I do as I'm told and pull in to taxiway. So; now I ask him to bug those numbers! Because we have them. He's barely through before takeoff checks. We get those done and now were ready.What I failed to see XYC [intersection takeoff] was flaps 20. Not flaps 8. If I had made him read and do all the taxi checks over again; I guarantee I would have seen it. And I didn't. We did a normal takeoff. Got to 1;000 feet. Accelerated to 200 KTS. VT 10 I call for flaps up. Well; I glanced down and saw 20. I was sick to my stomach. I can't believe I made such an error. All I could think about was the CRJ -200 that went off the runway when was in ground school.That said; the airplane flew fine. We got it cleaned up. We flew to ZZZ as normal. Still; I'm not happy with what happened and want to admit to it. I have learned from this; that from now on; when ATC changes my runways 3 times and we're under pressure; I'm stopping that airplane and redoing the whole checklist over again. No question about it. Because if I had; I would of caught that.Lastly; my FO. As I stated earlier; he's a great guy; very nice; but he is behind that airplane. I almost feel at times I'm single pilot. Flying to ZZZ; he goes on this rant about '%^$% Aviation Safety Action Program (ASAP) and #%@& Flight Operational Quality Assurance (FOQA); changing runways is ##%' etc. I told him to calm down and not worry about it and I needed him to focus on flying the plane and helping me. I could tell this flustered him. He missed all his after takeoff flows even though I asked for them. I looked up and see a green light and I ask 'why is the APU still on?' I check Crew Alert System (CAS) and ask why the thrust reversers are still armed. He throws his hands up and says I'm not thinking right. I didn't yell or say anything. I just got the airplane configured correctly.So; we land in ZZZ and we still have to do one more ZZZ1 to ZZZ turn for the night. It's his leg to ZZZ1 and we're taxing out. He's not organized. He has no charts out. He's fumbling for them. He couldn't brief me. I look at him and ask if he's okay and if he wants me to fly the leg to ZZZ1 and back to ZZZ. He said he thinks that would be best. We flew (well; I was pilot flying) the last two legs without incident.I think it might be best for my FO to have a review or maybe some more training. I say it out of Safety. Not to be mean. The CRJ is a huge learning curve. I was there once myself; so; I get it.


Second narrative: Taxiing to Runway XYC with the flaps set correctly at 8 degrees for XYC and while performing the before takeoff checklist Tower asked if we could turn onto XYC intersection taxiway in order to give way to a MedEvac aircraft taxiing behind us and accept a XYC intersection [takeoff] departure. After the Captain told the Tower we could; the MedEvac aircraft was given a takeoff clearance behind us from [a further down] XYC intersecting taxiway so in fact our intersection departure was no longer a necessity. Nevertheless; Captain turned onto [intersecting runway] and after stopping short of XYC changed the Automatic Communications Addressing and Reporting System (ACARS) takeoff data from XYC to XYC [intersection takeoff]; informed me that he had bugged the speeds and asked me to finish the before takeoff checklist and call ready for takeoff. During the climb the Captain pointed to the ACARS and stated that we should have used flaps 20 instead of 8.


Synopsis: CRJ-900 flight crew reported taking off with flaps set to 8 when they should have been set to 20; after several runway changes by ATC during taxi out. The Captain described the First Officer as being well behind the aircraft.