Maybe a stupid question and/or often asked, but I could not find an answer in this forum:
My hydrofoil consists of Mainwing and Elevator. Analysis with fixed lift, because the lift of the complete plane must always compensate the weight of board+rider.
For all Wingfoil-hydrofoils the elevator is mounted "upside down" and therefore generating negative lift for nearly all Op-Points. The lower the AOA of the mainwing, the higher the AOA of the upsidedown-mounted-elevator: The lower the AOA of the mainwing / the faster the plane is going, the more downward lift is generated by the elevator.
Because the sum of all lift-forces must always equal the total weight of board and rider, the mainwing must compensate the negative Lift of the elevator by producing more lift:
Example:
Weight of board+rider = 80kg / 800N
Total lift mainwing = 1.200N
Total lift elevator = -400N
Total lift plane = 800N ok!
My question:
Where can I see the total lift in Newton separately for mainwing and elevator in XFLR5?
I did only manage to see the total lift Fz of the entire plan, which is of course always the same (fixed lift analysis!). In my example it is always 800N.
But I need the lift wing and elevator separately for stress calculation of the fuselage.
The total lift of one wing in Newton should be the total area of the lift distribution, shown in the 3D-view, right?
Last edit: KlausG 2023-03-02
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Hi Klaus,
I don't think there is an option to display the individual lift, or at least I can't think of one right now.
I would create individual "planes" instead, one for the main wing and one for the elevator. One would suffice as well, since you can just calculate the other one by hand. Then perform a T1 analysis for the velocities & AOAs obtained from your T2 analysis of the whole hydrofoil board. Since you know the corner cases two velocities with a very narrow range of AOAs should suffice - one analysis for the maximum and one for the minimum force generated by the elevator.
This obviously assumes that the influence between the lifting surfaces is small, but it should still suffice. You probably don't want to build your hydrofoil with a safety factor of 1 anyway ;)
Cheers,
Stefan
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At the moment I take the average CL over the span and insert it into the Lift-formula (CL * ro/2 * A * v2). I just wondered, because alle the values are there, would be easy to implement it!
By the way, for my planned aluminium-fuselage I have safety factor 1,5. But you never kow :-)
regards,
Klaus
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Hi Klaus,
I'm assuming you're already doing this but I'm going to write it out a bit more clearly nonetheless so someone in the future can understand:
You can export the individual operating points of the analysis as a text file and use a spreadsheet program like excel to calculate the overall lift coefficient of the elevator and wing individually. Those can then be inserted into the lift formula.
With a bit more work you could probably write a script to automate this.
Cheers,
Stefan
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Maybe a stupid question and/or often asked, but I could not find an answer in this forum:
My hydrofoil consists of Mainwing and Elevator. Analysis with fixed lift, because the lift of the complete plane must always compensate the weight of board+rider.
For all Wingfoil-hydrofoils the elevator is mounted "upside down" and therefore generating negative lift for nearly all Op-Points. The lower the AOA of the mainwing, the higher the AOA of the upsidedown-mounted-elevator: The lower the AOA of the mainwing / the faster the plane is going, the more downward lift is generated by the elevator.
Because the sum of all lift-forces must always equal the total weight of board and rider, the mainwing must compensate the negative Lift of the elevator by producing more lift:
Example:
Weight of board+rider = 80kg / 800N
Total lift mainwing = 1.200N
Total lift elevator = -400N
Total lift plane = 800N ok!
My question:
Where can I see the total lift in Newton separately for mainwing and elevator in XFLR5?
I did only manage to see the total lift Fz of the entire plan, which is of course always the same (fixed lift analysis!). In my example it is always 800N.
But I need the lift wing and elevator separately for stress calculation of the fuselage.
The total lift of one wing in Newton should be the total area of the lift distribution, shown in the 3D-view, right?
Last edit: KlausG 2023-03-02
Short version:
For a defined plane: Where can I see the total lift (in Newton) separately for main wing and elevator for different OP-Points?
Hi Klaus,
I don't think there is an option to display the individual lift, or at least I can't think of one right now.
I would create individual "planes" instead, one for the main wing and one for the elevator. One would suffice as well, since you can just calculate the other one by hand. Then perform a T1 analysis for the velocities & AOAs obtained from your T2 analysis of the whole hydrofoil board. Since you know the corner cases two velocities with a very narrow range of AOAs should suffice - one analysis for the maximum and one for the minimum force generated by the elevator.
This obviously assumes that the influence between the lifting surfaces is small, but it should still suffice. You probably don't want to build your hydrofoil with a safety factor of 1 anyway ;)
Cheers,
Stefan
Thanks, Stefan!
At the moment I take the average CL over the span and insert it into the Lift-formula (CL * ro/2 * A * v2). I just wondered, because alle the values are there, would be easy to implement it!
By the way, for my planned aluminium-fuselage I have safety factor 1,5. But you never kow :-)
regards,
Klaus
Hi Klaus,
I'm assuming you're already doing this but I'm going to write it out a bit more clearly nonetheless so someone in the future can understand:
You can export the individual operating points of the analysis as a text file and use a spreadsheet program like excel to calculate the overall lift coefficient of the elevator and wing individually. Those can then be inserted into the lift formula.
With a bit more work you could probably write a script to automate this.
Cheers,
Stefan