Discussion in 'Hydrodynamics and Aerodynamics' started by revintage, Feb 27, 2020.

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### revintageSenior Member

Have played around in Excel with the formulas discussed in
Aspect ratio for surface piercing foil https://www.boatdesign.net/threads/aspect-ratio-for-surface-piercing-foil.63468/ , to find liftoff and max speed numbers.

To calculate a V-foil with a single dihedral foil at the lower end, I have used the NASA 1954 3D CL formulas from the thread above for the V and used the Fs equation from Beason and Buckle when calculating 3D CL of the single dihedral. No drag calculations done.

It might be some errors involved, so if anyone wants to make a "ballpark reality check" it would be appreciated. With so many unknown parameters involved in an amateur foiler design, I guess this basic spreadsheet is good enough.

#### Attached Files:

• ###### VEND2fix.xlsx
File size:
109.8 KB
Views:
346
Last edited: Feb 29, 2020
2. Joined: Nov 2016
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### revintageSenior Member

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### tspeerSenior Member

I think you'd be better off using AVL to calculate the lift and induced drag on a V foil configuration like that. The reason is there is substantial interference between the legs of the V, and the spanwise load distribution of the y foil will be unlike either the V or an inclined / foil. AVL can also include the infinite-Froude number approximation to the free surface, which is reasonably representative of the free surface effect at the operating speeds of hydrofoils.

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### revintageSenior Member

Thanks for the input. I am fully aware of that a program like AVL can solve this and give all the answers. Unfortunately I am not into DOS and that is a pity. I found a program that I could probably handle, but it is far beyond my price limit: MultiSurface Aerodynamics: Wing Analysis and Design Software http://www.hanleyinnovations.com/multisurface/

The Y-foil calculations I made indicates that the necessary liftoff area needed is at fault, giving far to large numbers. My idea with this spreadsheet was to find a simple ballpark calculation, but your answer indicates this is probably not achievable.

If we imagine the pure V-foil calculations(based an the above mentioned -50s paper) are OK, the area for the Y-foil should probably not be so far off from that, maybe a little larger at liftoff and a little smaller at high speed.

If using the added projected span of the V and END when calculating 3D CL for the END the results gets more realistic, but this is only based on guesstimate. See attached file where NEW-Y is the one with manipulated 3D CL.

Long before playing around with the spreadsheet, my non scientific ballpark guesstimate was 1150 cm2, although with a shorter END and a wider V ;-) .

#### Attached Files:

• ###### VEND2fix5test.xlsx
File size:
23.9 KB
Views:
266
Last edited: Mar 13, 2020
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