Creating a sketch for building a light house made of wood

[M4x]

Can someone explain to me which angle is missing / hard to get with TechDraw? I haven't understood it so far

The other dimensions are as expected if I'm correct?

TechDraw

Snip macro screenshot-6d33ff.png (14.28 KiB) Viewed 1168 times

[Shalmeneser]

Can someone explain to me which angle is missing / hard to get with TechDraw?

Any angle on a face (0° here, should be the same).

[derNiwi]

I'm trying to measure the angle between this two planes / faces along the green edge.

Measure the angle between this two planes.png (12.45 KiB) Viewed 1115 times

For this I need a view perpendicular to the green edge, because the object itself is not a cuboid.

Need a view view perpendicular to the green line.png (34.42 KiB) Viewed 1115 times

Using the manipulator Workbench it results in 112.28 degrees, or as inside the object 67.72 degrees.

Update:
I've tried with both
OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.25391 (Git)
Build type: Release
Branch: master
Hash: eef30446aa32ae989d5025cabcd8c28093f6a801
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: German/Germany (de_DE)

and

OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: German/Germany (de_DE)

Update 2:
attached "Lighthouse FreeCAD 002.FCStd"

[Shalmeneser]

center angle of an octogon : 360°/8 = 45°
isosceles triangle : (180°-45°)/2 = 67.5° 67.5°+67.5°+45°=180°
The angles at the bottom (or top) are 67.5° or 180°-67.5°=112.5°

It's possible to get those numbers in a 3D view (but TechDraw doesn't get it right confusing with acute/obtuse angles).

[derNiwi]

Yes, as I said before, I can calculate them or meausre it using the Manipulator Workbench.

But nothing of this will let me create a technical drawing. So I need either a (simple) way to create additional views aligned to one plane and perpendicular to a selected line or something like a construction layer were I can use the "Align view to face" macro.

Fortunatelly FreeCAD now stores the used view in the Page object so it should be possible to use different views for one part.This is of course a special situation, but I don't think really unccommon. So I wonder if no one else has asked this question.

[papyblaise]

Is it really necessary to cut the frog's hair in 4 like this?
for a mathematical truth perhaps
but in real life, especially in wood
but I concede that making a projection of cut (section) according to a desired plane would be a good

[derNiwi]

At this step the error is very small, I agree. But I think I will get an other part (since I've build this project with Fusion) so the error might b much bigger.

Changing the Tower_height in the spreadsheet from 1000 to 200 will also change this angle. Now TechDraw and it's projection shows up with 67.31° while the correct angle is about 71.67° - a difference of about 4 degrees. If I build this in wood I 16 times (8 pieces with two edges) this difference which will result in a huge error.

In the "original" version with a tower height of about 1000 it would end up in about 6.5°...

And yes, before you ask, I know that I also will have to tilt my saw with a high precision which also will give me an additional error.

[derNiwi]

I tried to recreate the Fusion 360 light house with FreeCAD from almost scratch.

I currently have still a problem with the roof and for the next step with the TechDraw as written in the previous comments.

But just to get an idea what I'm trying to build...

Light house.png (16.73 KiB) Viewed 1006 times

Edit: updated the file with the last version, I forget to make the window size changeable using parameters.

[derNiwi]

So here is my current version of the light house.
I know it is not perfect, there are for sure some improvements and I have to learn a lot more.

But I got my object and implemented some points I wanted to have:
- use parameters so I can change the tower on the fly
- have the ability to check dimensions and angles using the Manipulator workbench, unfortunatelly I have not really a good progress with the TechDraw workbench and angles
- can "detach" the light house to parts I can build with wood

Thank you all for supporting.