Roof Problem !!!

[greggieboy]

Hi Guys,i have built a few small structures from card previously,but have currently stepped up the anti and decided to construct a station building.It is not based on any specific building so there are no detailed plans,only my rough drawn sketches of what I 'designed' !!

      Everything has been going ok until I have reached the point of constructing the roof(s).

The problem being I have one apex roof joined at 90 degrees to the other.How do you get the measurements and angles right where the two roofs meet?.....HELP !!!!

[john new]

I am sure it can be done as precise theoretical exercise with geometry, the easier way is make the straight through leg as a mock up in card, then fold a much thinner paper template for the angled roof leg. Trim with scissors until it sits right. When you fold that out you then have the template for your final build angles and lengths.

[Great Eastern Lady]

I had the same problem with my station building roof , like @john new said the easiest way is to use thin card templates first before making the roof proper 

[ikcdab]

Yes it can be worked out with some simple trigonometry and Pythagoras. I am not trying to be clever, is about the only thing I remember from my school days and have found both useful my modelling.

I tend to plot out my structures using Coreldraw and it's easy to measure on screen. However if you are using good old pencil and paper, then templates are a good approach.

Doesn't have to fit perfectly as the flashing will cover any gaps.

Ian

[Kylestrome]

.

 

Edited February 4, 2021 by Kylestrome

[DGO]

Perhaps this will help   

isometric (3d) view at the bottom, elevation views in the middle, development of roof panels at the top.

 

You can work out B and J by simple trigonometry as they are the hypotenuse of the triangle or add the square of each of the other two sides together and the square root of the sum will be the length 

 

The best way to work out the dimensions for D, F and G is to draw the structure in projection all, you actually need are F & G, D is just a check dimension.

 

Finding I is easiest using projection, but you can find it wit trigonometry so long as you know the width of each roof section and the height to the ridge, then it's just a case of drawing triangles 

 

David

 

Edited February 4, 2021 by DGO

[DGO]

OK so if you are not good at geometry here's another diagram to help you work things out

 

Lets work out B first, this = Square root of (( P ^2 ) + ((Q/2)^2)) or if you prefer The Square root of B = P squared plus half of Q squared

 

Next Lets work out B , this = Square root of (( R ^2 ) + ((S/2)^2)) or if you prefer The Square root of J = R squared plus half of S squared

 

Lastly we need to wok out I

 

First we find the angle X this = inv TAN of P / (Q x 0.5) or Angle X is the inverse TAN of P divided by half of Q (use a calculator e.g https://www.rapidtables.com/calc/math/Arctan_Calculator.html ) 

 

Now we know the height of the ridge line R and the length H so I is calculated as follows Divide R by the tan of Angle X and add H or (R/tan X )+ H = I 

 

 

 

Edited February 4, 2021 by DGO

[simonmcp]

A compass and old fashioned drawing board with set square would help as well. Studying how John Wiffen of Scalescenes does his kits will also give you a good idea of how it is done. When it clicks in your brain it will seem simple but it's actually hard to explain without seeing it done. I couldn't find any short sensible YouTube videos either.

[john new]

Sorry @DGO I still think paper and scissors to make a template is so much easier. The KISS principle in action.

Edited February 4, 2021 by john new

[monkeysarefun]

This is all going above my head. Have I always been doing it wrong?

 

First, I assume this is the situation you are talking about, greggieboy - you need to work out the dimensions of the roof over the unfinished section? 

You know one dimension -  from the top of the gable down to the eaves, so I cut a strip of card that is the same width as that but longer than I know the finished roof will be, and put it in place so that the bottom edge touches the other roof.

 

Now I measure A, and transfer that length to B, I then draw a line from this point up to the peak and cut it out. Here it is shown cutout but not adjoining the other roof for clarity. It can be slid up until it butts the other section 

 

I  measure it  for  its final length allowing for any possible overhang at the gable end and cut to fit.:

If you are accurate at building things, the same piece can be replicated to form the other side, but mine never quite works out so I repeat the process for the other side to give:

 

 

 

Is that what you were after - all the geometry and trignometry and maths and stuff in the posts above  above makes me wonder if I am just a bit simple.

 

 

[Pete the Elaner]

A friend of mine suggested using Sketchup, an online 3d CAD program which I was a little familiar with after using it for designing items for 3d printing. It is free, there is nothing to install/ It just uses a browser & all drawings are stored online.

It was one of the best pieces of advice I have taken. I previously used card to make a mock-up but drawing on a computer was so much easier.

 

I wondered about roof angles, so I googled it to find out. The answer I got was that it depends on how heavy rain usually falls, but never ever use a 45 degree angle (90 at the roof) because for some reason, this looks odd.

 

To find the top of the roof:

Draw the base.

Fine the length of the shortest side. Find the halfway point. Draw a line from this point in towards the centre of the roof. The line needs to be half the length of the side measured earlier.which is the same as half the length of the shortest side.

Work out how high you need (I used 80% of the length in, which gives a gradient of 80% or 39 degrees) & draw a line this high.

Do the same at the other end.

Draw lines connecting the top of these 2 together. This is the top line of your roof.

Draw lines from each corner to the nearest end of this top line.

Use the measuring tool to find whatever measurements you need.

 

This is easier to demonstrate over a video conference than explain in words.

You only need to understand very basic tools in Sketchup.

 

[Damo666]

7 hours ago, DGO said:

Perhaps this will help   

isometric (3d) view at the bottom, elevation views in the middle, development of roof panels at the top.

 

You can work out B and J by simple trigonometry as they are the hypotenuse of the triangle or add the square of each of the other two sides together and the square root of the sum will be the length 

 

The best way to work out the dimensions for D, F and G is to draw the structure in projection all, you actually need are F & G, D is just a check dimension.

 

Finding I is easiest using projection, but you can find it wit trigonometry so long as you know the width of each roof section and the height to the ridge, then it's just a case of drawing triangles 

 

David

 

Hi David,

 

Good drawing, should be very helpful to lots of people.

 

Can you check dimensions C and J between the plan views and the isometric. One appears to show the dimension along the slope and the corresponding letter shows it on the true elevation.

 

Otherwise, wonderfully clear and explanatory (at least to me, someone who's been making / reading such drawings for, well, lets say a long time).

Thanks

[DGO]

7 hours ago, Damo666 said:

Hi David,

 

Good drawing, should be very helpful to lots of people.

 

Can you check dimensions C and J between the plan views and the isometric. One appears to show the dimension along the slope and the corresponding letter shows it on the true elevation.

 

 

The views at the top are not plan views but are developments, that is to say that the top set of views are what you get if you draw the roof on a flat sheet of paper and then fold it up, thus C and J are correct 

[David Bigcheeseplant]

I draw up in 3D Aylesbury station in Fusion 360 you can then create drawings for each elevation, plus at an angle to the roof plan if you know the angle, as in my case there was lots of intersecting roof parts but doing it this way was really simple and I did not have to work anything out. 

Building Roof Parts Drawing v1.pdf

[Damo666]

1 hour ago, DGO said:

The views at the top are not plan views but are developments, that is to say that the top set of views are what you get if you draw the roof on a flat sheet of paper and then fold it up, thus C and J are correct 

Oh, OK. Understood.

 

I was reading the top images as true elevations of the surfaces, ie: as if the roof was flattened to a 2D plane like a piece of paper before being folded.

 

My mistake.

[DGO]

37 minutes ago, Damo666 said:

Oh, OK. Understood.

 

I was reading the top images as true elevations of the surfaces, ie: as if the roof was flattened to a 2D plane like a piece of paper before being folded.

 

My mistake.

 

No problem, this was why I said they were developments, what I was forgetting is that most people don't know what that means, sorry

[greggieboy]

Well Guys and Girls,I certainly opened a can of worms!!

Thanks to everyone who replied.It is amazing how many methods people use.

I think I will try the method from 'monkeysarefun ' to start with and see how I go'.

 

Thanks again everyone for your time and expertise.

[Nearholmer]

2 hours ago, greggieboy said:

I think I will try the method from 'monkeysarefun ' to start with and see how I go'.

 

Monkey's method works perfectly, I've always used it, and it is a lot quicker than doing the maths.

 

All the methods using CAD look very impressive, but wouldn't be my cup of tea, because I find learning how to use such software packages a tedious effort that I'd rather not spend hobby time on.

[Shanghai Diver]

Coming late to this, but I had a similar, but simpler roof problem.  My Trig days are long behind me but thankfully the internet arrived to rescue me!  

 

This (of many) I found to be the most intuitive for trig work: https://www.omnicalculator.com/math/trigonometry and got me to what I needed with the correct angles give or take my modelling errors.