Designing a Surfboard Fin

[wandererfan]

I tested both versions of the macro on Ubuntu 13.10 using latest Development Release and can confirm that flat spot. It looks OK as Wire and converting to sketch gives predictable results. Converting to BSpline adds that flat spot.

Could I get a step-by-step please? I can't reproduce the flat spot or the Coin error. This is what I'm doing:
1) Macro v2.0 from [wiki]Macro_Airfoil_Import_&_Scale[/wiki]
2) input file: NACA0007.dat, options: DWire, chord=100
3) run Draft DWire to BSpline tool on result
My results:

NACA0007.png (161.04 KiB) Viewed 2978 times

And for NACA0012.dat:

NACA0012.png (160.25 KiB) Viewed 2978 times

I must be doing something wrong (right?).

wf

OS: Ubuntu 12.04.4 LTS
Platform: 64-bit
Version: 0.14.3435 (Git)
Branch: master
Hash: 61919e89abdd7630e3893e33374eb303cd0fe726
Python version: 2.7.3
Qt version: 4.8.1
Coin version: 3.1.3
SoQt version: 1.5.0
OCC version: 6.7.0

[wandererfan]

I can't reproduce the flat spot or the Coin error.

I found the Coin error message, but only in the terminal window, not the FC display.

[triplus]

I can't reproduce the flat spot or the Coin error.

I found the Coin error message, but only in the terminal window, not the FC display.

True. I forgot to mention the error is shown in terminal not in FC.

This is what I'm doing:

Dwire is fine but converting to BSpline produces this on the screen:

naca.png (9.22 KiB) Viewed 2974 times

I used the exact same procedure as you said you used.

[triplus]

What is interesting using Pad on created BSpline produces result as if flat spot was not there. Maybe this is just "visual glitch" or some setting in preferences that controls visual representation for BSplines?

If it is a bug i guess it is a bug in some library responsible for visual representation where newer version is used on Ubuntu 13.10 and bug does not affect older library used on Ubuntu 12.04? Anyway it looks like it is more of an "visual representation" bug and not something affecting other tools in FreeCAD for example creating drawing view produces expected results without flat spot too.

[triplus]

Yes it is purely visual setting in preferences affecting this behaviour.

@woodbuddha just go under Edit -> Preferences -> Part design -> Shape view -> Tessellation. Set it to this 0.02 and you should achieve what you are after!

[woodbuddha]

Thanks Guys. Problem solved with the changing the teselllation to 0.02%

WB

[Florian]

Hi, I just starded with freecad and use it for designing a sailboat rudder. Very usefull info here, helped mee a lot. But besides the flat spot I had as well (fixed) there seems one more problem with converting the wire to a spline, the trailing edge witch is flat on my foils from xflr 5 becomes funny when using a spline. Are other peaple experiancing the same or is there a easy fix for that? Right now it looks better to me to just use a wire with a lot of point so the flat spots become neglectable.

[Florian]

After closing the trailing edge gap the problem is solved, althoug the TE gap is in the foil by default and might be there for a reason. Not sure if I ant it there or not, for construction it is probable better if it is there.

[Looktree]

Dear Florian,

have you managed to solve this "problem" somehow?
I do have the same with a kiteboard fin at the moment.

THX
Uwe

[woodbuddha]

Hi Florian,

Yes I get the same thing happening to the TE of my foils as well. How did you resolver the problem?

TK