What is the total EXTRA lift produced using an 80 deg flap and distributed propulsion? What is the total EXTRA lift produced using an 80 deg flap? ( 50 deg flap at 30 deg AOA ) and distributed propulsion.

Specs: Ultralight, stall speed 20mph, ROW of 12 x 15" props along entire wing span in DISTRIBUTED PROPULSION, max local AOA estimated at &lt; 9 deg ), electric 25 hp (total), MTOW 500 lbs, low wing in ground effect, max 3 ft height for xSTOL/nVTOL, VG's, full span single slotted flaps with spoilers , Clmax: 3.4.

Hypothesis:

A low wing ultralight accelerates with a short field takeoff, along a runway to 20mph and rotates to 30 deg AoA just prior to takeoff, producing the following:

Total lift = Wing lift (bernoulli/momentum/vortex lift + deflection lift )  + Prop lift + Flap Lift

Example:


Wing lift: 


standard wing lift formulas, lift equal to airplane weight of 500 lbs.


Prop lift:


Estimated thrust at 20mph: 5lbs/Hp thrust x 25 HP = 125lbs thrust.

Prop lift = 125 lbs x sin ( radians(30 deg))= 62 lbs


80 deg Flap Lift


Thrust due to Prop wash on bottom of wing hitting flap
= 30%(???) of total thrust = 37 lbs.


Total extra vertical thrust/lift


= 62 + 37 = approx 100 lbs ( 20% extra vertical thrust/lift...!!!! )


Reduced MTOW wing requirements at Vtakeoff to Vflap


orginal MTOW = 500 lbs.

MTOW revised= MTOW original - extra vertical lift = 500lbs - 100 lbs.= 400 lbs.

This is the reason for asking the question: 

Could I then resize my wings based on 400 lbs MTOW at Vtakeoff(Vso) to Vf, not 500 lbs?

Is this correct thinking?  

See black tuft dwg below showing downwards air flow.
A 30° flap is a typical landing setting. Increasing that to 80° is only adding more drag. Your 25 hp thrust will only add a mild breeze and will not help to reach that 30° AoA unstalled. Better use 8° or 10° of flaps (depends on flap chord) and do not rotate to more than 10° AoA.