HVT FLC NEGLECTS TO RETRACT FLAPS COMPLETELY. FLAP OVERSPD.

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THIS HVT WAS EQUIPPED WITH ELECTRONIC FLT INSTS (EFIS) AND A MODERN AUTOPLT. THE COMPANY ENCOURAGES ITS USE AT ALL TIMES BUT DOESN'T REQUIRE ITS USE. I DON'T ALWAYS USE IT BUT DECIDED TO USE IT THIS NIGHT FOR PRACTICE. I HAND FLEW THE AIRPLANE TO 1000 FT AGL; NOSED THE AIRPLANE OVER; CALLED FOR THE FLAPS TO 10 DEGS (FROM THE TKOF SETTING OF 25 DEGS); AND STARTED PUSHING BUTTONS TO SET THE FLT DIRECTOR AND ENGAGING THE AUTOPLT. AT THIS TIME WE WERE SWITCHED FROM LCL CTL TO DEP CTL WHICH ISSUED AN ALT CHANGE AND A ROUTING CHANGE. AT THE POINT I SHOULD HAVE CALLED FOR FLAPS UP I WAS PUSHING BUTTONS AND THE FO WAS BUSY TALKING ON THE RADIO. AT 3000 FT AGL I CALLED FOR THE AFTER TKOF CHKLIST. THE FO SHOULD HAVE CHKED THE FLAPS UP BEFORE HE CHKED THE GEAR UPLATCH. THE SO SHOULD HAVE VERIFIED FLAPS UP IN ACCORDANCE WITH THE AFTER TKOF CHKLIST. THE HVT HAS NO LIGHTS TO INDICATE FLAPS DOWN LIKE OTHER MANUFACTURER ACFT. THE FLAP GAUGE IS DOWN BY THE FO'S L KNEE AND THE FLAP HANDLE IS HARD TO SEE IN A DARK COCKPIT. SOMEWHERE ABOVE 20000 FT AT 300 KTS I NOTICED THE AIRPLANE'S CLB PERFORMANCE BELOW NORMS. I LOOKED AT THE FLAP GAUGE AND SAW THE FLAPS WERE STILL AT 10 DEGS. MAX SPD FOR THE FLAPS AT 10 DEGS IS 230 KTS. THERE WAS NO DAMAGE FOUND DURING THE REQUIRED MAINT INSPECTION. CONTRIBUTING FACTORS: 1) PF ENGROSSED IN EFIS AND AUTOPLT. 2) PNF BUSY TALKING ON RADIO DURING CRITICAL PHASE OF FLT. 3) HVT DESIGN.