Trying to draw Bow-roof gothic arch for my greenhouse

Bow sheds can get to be quite large and still remain structurally sound.

2 Likes

Couldn’t agree more, but something tells me we are needing to give a few more directions on how to do it than we in the know would normally need.
With all good intentions, you need to get the math and the logic.

1 Like

I think the problem stems from the 5m limit on the length of the boards. The classic Gothic Arch uses a 60 degree equilateral triangle. To create one with a 6.4m base needs a 6.7m length bent along a 6.4m radius.

Another solution … add extra triangle at the top made from straight pieces.

1 Like

You could just remove the ‘fancy’ bits from my model and …

1 Like

According to this website, 6.25m width should work.

The classic Gothic arch is known as the quinto acuto or “pointed fifth”. The arcs are 4/5 of the span. The centres of the arcs are inside the span of the arch.

http://www.codesmiths.com/shed/workshop/techniques/quinto_acuto.jpg

http://www.codesmiths.com/shed/workshop/techniques/arches.htm

That works out to requiring the curved pieces to be 5.93m long … they’re only 5m to begin with.

@jimhami42 what do you mean?

The problem here is that a fixed width between the two arches, the length of those two arches, and the radius of the ‘bending jig form’ is presumably fixed.
Therefore the exact form of the two arches needs a specific setting out so that it works.
There have been several permutations offered…

Can someone please [re]state the exact width at the base, AND the exact bent radius [5m ?], AND the exact arc [5m ? timber] length.

Width 6m
Timber length 5m ( less a little for top trim)
Radius 5m

With only following this for a while, I think that the radius has to be decreased to bring the top together sooner to have the 6m width.
The 5m length is fixed, the 6m width is critical, the radius/form of curve is the only variable that I see to allow this to “happen”.

Just my thoughts.

Some excellent tries so far by the way.

1 Like

I think this should be the question: what should the width be for 5m long timber? my original plan was 6.4m width but I think the width should be max 6.25m. I might even go for 76.8m long, 6m wide. this should give me 460.8 square meters.

Hello Baris…What are you going to grow…trees or…?
do you need the width or the height…?

Why not make 2 rows of a smaller “More Normal” size…?
2 greenhouses: 78m3m.
or…
4 greenhouses: 39m
3m.

That is my practical suggestion to you…
Consider the logistics, of walking and watering 78 meters to “Finish”…!

Work is commenced. Foundation posts are set.

4 Likes

a few years late, found this thread to be super informative and fun! any finished product pictures by chance?

I need to take some photos. I don’t have any latest ones.

1 Like