Trying to draw Bow-roof gothic arch for my greenhouse

Hi there,

I am very new to sketchup and trying to draw this all day without any luck.
I am building a greenhouse. I want to draw the arches.

These are some sample arches.

My timber is 5m long, 70mm wide and 25mm thick. So the radius of the arch will be 5m. Inside timber will start about 10cm before the outside arch.

Can you please help me.

here is an image I drew.

Hey there! Have you watched any of the beginner videos at SketchUp Campus? They are a good place to start for getting familiar with some basic SketchUp fundamentals.

What I would do to approach the arches, is to get the dimensions down for each item of the arch in 2D (on the ground plane, draw the shapes for each item) and then use the push/pull tool to extrude each shape up.

I would create components for each element of the arch. It looks like for each full arch, you would make the following components:

  1. The inner arch
  2. The outer arch
  3. On each end, there are two longer connectors - make one connector and then copy it.
  4. The connectors in between look shorter than the outside connectors and look to be uniform in size. If you make one inner connector, make it a component, and copy it then you will be able to edit all the inner connectors at once.
    Here’s a bit of reading on components: Creating a Basic Component | SketchUp Help
    Here’s a bit of reading on how to copy/paste items easily: 그린 개체 복사하기 | SketchUp Help

We need more information to be able to help you draw this. How tall at the peak on the inside? How wide at the base? How thick are your spacer blocks?

Thanks alot for your help. I have tried to do this for 2 days now without success. I can get the basic but the measures don`t add up.

Please check the image below.

My timber is 5m long, so the radius of the inner timber will be 5m.

Now I’m at my day job and don’t have access to what I need to show you how to draw this but, with the given dimensions, start with an online calculator to figure out the included angle for an arc with a 5m radius and 5m length. It happens to be 57.296°.

Use the Arc tool (not the 2-Point Arc) to draw an arc with a 5m radius and 57.296° included angle. After that you can use Offset on that arc to create the other edge of the inner board as well as the edges for the outer board. Use the Line tool to connect the ends of the arcs to create faces. then, if you want to make this 3D, Push/Pull to width. Make each bow a component. Rotate the outer one about the center of the arc (I used the origin for this) to raise the bottom up 10cm.

You can draw a block to fit between the inner and outer bow, make it a component and use Copy/Rotate to copy it around the center.

No. The inside peak of the bow will be a little more than 4.2 meters.

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Hello DaveR…
How do you insert drawings in here…?
My “Peak” is between the arc and a straight base-line, its “Korde”.

@JakobHovman, use the Upload button in the message window. 7th from the left.

If the arc is a 1/4 circle why not draw it ?

This shows it slightly longer that the 5m ??
But if this a chord length as you just drew how is the to supported ?
With a semi-circle the diameter [d] needs to be just under 6.4m for a half-circumference of 10m long…
10 = Pi * d / 2
d = 2 * 10 / Pi = 6.37m

@JakobHovman, you’ve not drawn the correct arc and you’re working too hard to get what you got. The length of the arc in this case is 5 meters, you’re showing the chord at 5 meters. Those are very different dimensions.

@TIG, The arc isn’t a quarter of a circle, though.

This still needs the purlins but this is generally what a bow shed looks like. Much like a Gothic arch.

1 Like

Now I see it… doh!
As it’s set out around a equilateral triangle to determine the base ‘r’
we know there are six arcs in the full circle, so use…

5m * 6 = Pi * 2 * r
r = 5m * 6 / Pi / 2
r = 4.77m

You’ll note the title of the original post refers to a Gothic arch. Have a look at this. Lots of examples of what he’s trying to model. They make great temporary structures for working on boats, too.

Thank you very much.

I forgot to mention about the ridge beam. There will be 2 where the arches come together.

Yes. I left those out as well. No big deal, though. Draw a rectangle for the end of the beam and use Push/Pull to extrude it to length.

I am at work just now and I dont have access to sketchup. Can you please attach the sketchup file as well.

I’m sorry. I didn’t save it.


I am actually crying just now…

Sorry. It would be easily redrawn but I can’t do it right now.

Thanks. I spent 2 whole days on this without any success on the arch.
I will be looking forward to check this on sketchup.

A 5m length of wood bent along a 5m radius will come out to 57.295578 degrees of the circle. If you want to use 60 degrees instead, these numbers work out:

The inside piece will actually extend 61.283523 degrees, but you can compensate for that by aligning the top ends to the ridge beam.

Here’s the two pieces bent in place, if that helps: gothic.skp (64.7 KB)