Large Scale Central

Octagonal Roof Revisited

Okay, I am revisiting this topic. Not sure why I can’t get this through my head, but it seems to be my foe. So not that I am working with CAD, I want to build an octagonal roof for a water tank to go with the sand house I am building for the MIK. I was planning on making it entirely 3D printed. Or at the very least make print the roof panels. Once again I am running into not being able to figure out the geometry. In playing with it I have decided that I want a 4" diameter tank. I want a 15 deg pitch to the roof. and about a 1/4" overhang on the faces of the eves (not the points).

I thought I could figure it out in CAD. But no go. So can someone help me, either with how to make it work in Fusion 360 (Dan?) or help me with the angles. The way I was trying to do it was to layout 1 half of each of the 8 panels that I could then mirror and attach to the first. By doing this I can draw the bevel easily. This general theory worked but I never got the bevel angle right. So as I went around the octagon by the time I got to my 16th half panel I could never get it to mate up. Instead of trying and retrying to get that angle right, can someone help me get that bevel angle and any other geometry I need so that my panels will meet up.

Or is there a better way to approach it?

Is this similar to what you are after?

Well after messing with it the pitch needs to be a bit steeper more like 20 to 30 degrees. Dan, are those flat panels or is the roof a cone.It looks like a cone. The edges should be flat across the face not arced. And each of the 8 panels need to be flat.

Yeah, I caught that about the time I hit reply. How does this look?

Still at 15 degrees, though.

Here is some information that may or may not be of use to you. If you can’t/don’t use it let me know and I will take it down so it doesn’t clutter up ypur thread.

First laying out your octagon.

Then using that information to develope the layout and pattern.

This pattern developement is for a one piece construction to be rolled or broke into shape. The pattern can be cut in segments to use to develope on another material. the outside edges on the pattern can be cut straight across to eliminate the rounded look.

Here is one I did recently using the full pattern developement as shown in problem #43.

Good luck with your project.

I’m telling you all Dan knows EVERYTHING when it comes to Fusion… Do I feel another PDF study aid coming my way?

Yes Dan that’s what I am trying to do.


I would leave it up there for someone else but no it doesn’t really help for what I am trying to accomplish. But I do like that and If I get to $^%&%(%&(^( mad at it I will have a nice aged copper roof on it like that one. :thinking:

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Sure. Give me a little while to get back to the PC. Hard to do on an iPad :wink:

Thanks Dan. You should talk to autodesk and see if they will hire you for educational materials.

Wait a minute… I thought this was going to be a “ junk box only “ build. Wimping out rather quickly aren’t we!

This won’t be part of my MIK. This is just going in the same yard area.

Devon, your design guide should be in your inbox.

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I know I keep telling everyone how much i appreciate Dan and his working me through the difficulties of CAD drafting. In several posts it has been mentioned that the main hurdle to 3D printing is learning design. And I completely agree. And in the past I have said that 3D printing is cheating and have been properly scolded about how there is just as much if not more work/skill/talent that is involved with 3D modeling. Well its true. I could have made these roof panels by trial and error sanding much faster than it took me to learn to design them in CAD.

But Dan came through yet again. Not only did he figure out how to do it, but he sent me yet another PDF tutorial on with picture (Devon needs pictures) with a step by step on how to get it done. Now I have a perfect roof on my tank with perfect angles. But the best part is he didn’t just say here are the numbers or here I designed it for you. He walked me through the process and I can now and forever be able to do this whenI need to. I have started a Dan Fusion 360 tutorial file for myself.

Thanks yet again Dan.

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You are quite welcome, Devon. Oh, and remember, pictures or it didn’t happen :stuck_out_tongue_winking_eye:

It did occur to me that ‘trial-and-error’ would also have produced the roof using card to experiment. Cut out the roof in card as an octagon so it lies flat on your tank. Then reduce the bottom width of each segment while making them longer and try again. Eventually you’ll get a roof that fits your requirements.

Like this:

Dan said without pictures it didn’t happen. So here is proof that you can train a monkey to do tricks. Here is my octagonal roof.

I think after seeing the video on how to build a tank and since this will be viewed from the floor looking up that I will print the roof as one piece, the tank as another piece and then make the rafter tails separate pieces and then the legs will be real wood.