I'm starting to do some early optimization on my design, particularly for climb rate, since my engine is relatively small for the weight of the aircraft.
My spreadsheet now includes a formula that calculates wing weight based on a number of parameters such as wing area, aspect ratio, takeoff weight, maximum speed, etc. I can change the aspect ratio, then use the 'goal seek' feature in Excel to iterate a takeoff weight and wing area that maintains my the wing loading to meet a specific goal, such as stall speed, takeoff distance, or climb rate. That provides new information for the page that calculates climb rate based on required and available thrust, and spits out a new curve showing climb rate at various speeds. Spreadsheets are cool.
It'd take me days to do this by hand.
It's interesting watching the results in my low-power case, where increasing the aspect ratio is actually reducing the climb rate because of the extra weight of the longer, narrower wing.
I'm about to run a few cases and plot a curve for aspect ratio vs. climb rate to see what the optimum would be, if there is one. Then, since this is a flying wing, check that against my rough stability and control calcs to make sure it still works there.
I guess my point in posting this is how sometimes the results you get in the 'real design' are counter-intuitive. And that spreadsheets are cool.
My spreadsheet now includes a formula that calculates wing weight based on a number of parameters such as wing area, aspect ratio, takeoff weight, maximum speed, etc. I can change the aspect ratio, then use the 'goal seek' feature in Excel to iterate a takeoff weight and wing area that maintains my the wing loading to meet a specific goal, such as stall speed, takeoff distance, or climb rate. That provides new information for the page that calculates climb rate based on required and available thrust, and spits out a new curve showing climb rate at various speeds. Spreadsheets are cool.
It'd take me days to do this by hand.It's interesting watching the results in my low-power case, where increasing the aspect ratio is actually reducing the climb rate because of the extra weight of the longer, narrower wing.
I'm about to run a few cases and plot a curve for aspect ratio vs. climb rate to see what the optimum would be, if there is one. Then, since this is a flying wing, check that against my rough stability and control calcs to make sure it still works there.
I guess my point in posting this is how sometimes the results you get in the 'real design' are counter-intuitive. And that spreadsheets are cool.
