Aligning Planes in Rake Ladder Roof Structure Design

[nicorellius]

Let me start by saying, this forum is awesome! I recently got into DIY solar power systems and found a forum that was very active and helpful, and this forum is almost that good Which is saying a lot coming from a programmer who uses the Stack Exchange boards.

That out of the way, I’ve got a dilemma. I’ve been using SU for about 2 weeks and I’m getting the hang out it:

YouTube and this forum have helped me get this far, which is so great. Thank you!

But now I’m at a plateau. I keep running into the same type of snags… I’m able to do simple, straight forward things easily but I’m bumping into some issues. In this case, I’m working on rake ladders. As you can see, I managed to get one side built out. So now I’m working on the other side. It’s slightly narrower so copying the rake ladder component didn’t work out so well.

I orient my view so I’m looking directly down at the roof. Then I use the rectangle tool to draw a 2D rectangle and extrude it down into the rafters. No matter what I do (and I’ve tried this like 5 times), I get slight discrepancies:

The above is zoomed in at the junction of the rake board and the rafter. I’ve tried moving it, rotating it, etc. And I’ve confirmed best I can (with guides and the tape measure tool) that all my rafters are lined up as best I can get them.

Looking at it from a few feet out seems fine:

And even zoomed in quite a bit seems fine:

So I have two general questions:

1. What is the best way to model one of these rake boards?
2. Generally speaking, what kind of tolerance should I expect or accept? My goal is to submit this model to an engineer for approval so I can get city permits to actually build this thing on my property

My perspective as a developer makes me want to have everything be perfect, drilling down as far as I can. But I’ve seen other models out there (downloaded examples) that aren’t that great, so I’m wondering the acceptable level of tolerance is. Obviously when I go to build this thing from supplies purchased from my local Home Depot, Lowe’s, or lumber yard, the precision is going to be up to me and my carpentry skills.

Anyone out there have some real-world feedback on this? Experience with models submitted to engineers or using designers to build these models for real-world buildings? Am I doing something wrong or reaching the limits of the online program?

[DaveR]

If I were modeling the rake ladder I would start by drawing the first one in place. I’d draw it in the orientation it should have and, when creating the component, I would set the axes to align with the geometry. then I would use Move/Copy to make the additional copies up the roof. Move the first copy the required distances, then type x and the number of additional copies you want. If you are following the rafter line things should be aligned with no problem.

This is using a shed model so the copy distances is kind of short.

@nicorellius

My perspective as a developer makes me want to have everything be perfect, drilling down as far as I can. But I’ve seen other models out there (downloaded examples) that aren’t that great, so I’m wondering the acceptable level of tolerance is.

I’m in the same boat as you are. Small errors or sloppy bits might not be a problem but then again, they can result in problems. Personally I model to the highest precision I can. Higher than I’d need in the shop or in the field. I do this to prevent having errors creep in and cause problems later. It’s always easier to make things right up front than to chase problems and fix them later.

@nicorellius

Am I doing something wrong or reaching the limits of the online program?

My guess is it’s the former. I don’t think there’s any way you could have reached the limits of the program.

FWIW, depending on what you need to supply to an engineer and for permits, you might find it worthwhile having SketchUp Pro and LayOut.

[nicorellius]

Thanks for the reply and feedback. In fact, the suggestion you make is exactly how I did this left side. My problem is that when I make the first one, it’s not aligned to the geometry. How do I ensure the first one I make is properly aligned? As you say set the axes to align with geometry?

I’m already using SU inference to snap to the rafters to make my rectangle. Extrusion should not be an issue if the face is drawn properly.

I am considering getting pro but I wanted to familiarize myself with the free version first, a proper evaluation and all that.

[DaveR]

You can infer to get the direction correct and then, after making the component you can change the axes. I should have drawn the board wide face up but it’s much of a muchness.

In the desktop version you can set the axes to align to the geometry while you are making the component.

Alternatively you could make the component so it is aligned with the model axes and then rotate it after creating it. I prefer modeling as much in place as I can because it requires less data input.

[gsharp]

Might be easier to notch out a rafter first… make it a component… duplicate as needed… then use the notches to define your ladder frame components ?

[DaveR]

Not very common, at least in the US to notch rafters for rake ladder boards.

[pbacot]

Different working styles I guess. In the west I’ve never heard someone say “rake ladder”, but we notch the rafters so “outriggers” (or “outlookers”) can cantilever for the rake overhang. Usually notching one rafter or notches in gable wall framing

[nicorellius]

Thanks for all the feedback. I honestly didn’t know what they were called (as I’m a novice) so I just looked at some images online. I see references to outlooker, rake ladder, ladder frame, etc.

But it seems designs vary quite a bit, eg, only in between 2 rafters, spanning 3 rafters, notched, un-notched, supports horizontal or vertical. I’ll have to do some research for my sepcific use case.

And thanks again, @DaveR, the line tool on the rafter to draw end of rake board, then extruding out for the length, worked like a charm. I applied the change axes as well, and this was a very cool trick.

In general, whenever I have a board (or component of boards) that is not aligned on the default axes (x, y, z), I see it as a rectangle with the board inside:

Is it best practice to always change axes on these type of components?

[DaveR]

@nicorellius

Is it best practice to always change axes on these type of components?

It kind of depends on what you need out of the model. I would generally align the axes to fit the “board” because it makes it easier to apply textures correctly and I usually want some sort of report such as a cutlist from the model. Any of the tools thatmake those sorts of lists can only report bounding box dimensions so if I were running a cutlist on your model, the rafters would report as much larger than they are.

There are some times, though, when it makes sense to wait to change the axes for a component. For example, when I modeled the leg for this workbench I drew the first one in place at the front left corner. I left the axes aligned to the model axes so I could use Flip Along >Component’s Red to make the front right leg. After I was finished make that copy and flipping it, I changed the axes so the bounding box aligns with the geometry.

There are many times when modeling in SketchUp where the order of operations can make your work easier or more difficult. With time and use you’ll figure them out.