18-5: Did some Cave Man integration with 1/4 inch blocks on paper after tracing inboard rib with estimated sensor location but had no idea how much fuel or time this represented. Pictures I had seen showed the sensor higher than my eyeball estimate but provided no gouge as to what volume to expect. My first estimates by eyeball appeared to provide only a few minutes of flight before sucking air.
Basic process was to layout 1/4 in square, count and estimate averages between 1/4 in heights from bottom of the rib to approximately half way up. I measured dihedral of 3.5 deg, confirming what I had seen in one blog on-line by checking the cross-spar member and measuring using a steel protractor. I discounted the bottom 3/4 in of volume as unusable since this is where I estimate the fuel pickup to begin to suck air. Basic formula for line 3 that counts for the lowest level of usable fuel:
Vol (cu In)=B4/16*(0.25/TAN(3.5*PI()/180))*(1+2*(A4-1))/2
B4/16 = area of this layer in cu in. A4 = the line number, in this case would be 4 since which would produce 1/2 cube (dihedral angle until it reaches the next line equating to half the calculated volume cube) + 3 spanwise volumes.
Then add this amount to the next line through same calculation through about 15 lines. The multiple of the line number accounts for the total spanwise length for that volume height. Then have a running total and divide by 231 cu in/ gal to get the total fuel and divide by an ave of 12 gal/hr x 60 min/hr to get minutes at cruise. My result was 4 inches from the lowest point. for 4.5 gal and approx 20 min flight time.
Like I said, it's Cave Man integration so we'll see how close I get. Better than my first guess.