Making Plans.......How could I 'unroll' this shape?


Spiral Labyrinth.skp (1.4 MB)

Thanks to those whose advice helped me get this far…pretty much what I was aiming for… I now need to produce plans for the joiners and was wondering if possible to group and unroll the whole structure for machine cutting plans?

Was thinking of section cuts, but one 2D plan would be ideal…

Any ideas?


There re several plugins allowing to unfold entities ( unfold, flattery etc). I assume the tubes will be like SONA tubes etc, so use the unfold plugin to make paper template you can wrap around, trace curve and then cut card board tube with jig saw etc.
Sorry do not have them loaded here. note on it states Su 2014 and earlier but probably will work with 2015 also


I think that “unrolling” this construction would work log-by-log, not face-by-face, so the unfold plugins probably wouldn’t help–they would actually deconstruct the logs themselves.

Since the logs are all raw geometry–they really should be individual components (or groups)–ordinarily I would say you’re not unrolling anything, since all the logs are stuck together. But they’re not; incredibly, there’s a tiny gap between each pair of logs (except for a very few). Thus:

I certainly would go ahead and componentize the logs before handling them further. After that, If you’re really intent on “unrolling” them, the idea would be to rotate Log A around the axis of Log B to some reference line (upon which all the logs will line up). Then rotate A and B around the axis of C and stop at the reference line. Then rotate A, B, and C around D, and so on.

It sounds ridiculously time-consuming, tedious, and error-prone. At the risk of sounding pessimistic, there’s no way it’s going to happen.

Have you spoken to the builders who are going to make this thing about what kind of drawing they’d like to see and what kind of information they would need?

It seems to me they’re going to erect the logs first, then cut the openings, much the way @slbaumgartner showed you in your last thread. So what you need is a plan (top) view showing the position of each log, giving dimensions for the overall pattern. You’re going to have to assign each log a reference number of some kind so you can refer to them, so you should label them in the plan view or provide some kind of numbering schema.

I think you’d be best off creating a spreadsheet to tabulate the lengths of the logs. Just list the reference designations and give an axial length. You can query each log for its length with Entity Info. This sounds extraordinarily tedious, but I guess that’s the nature of this project. As I said, the openings can be cut using a couple of elevation views to locate them and provide size dimensions.



I agree with @Gully_Foyle and add this thought: the cuts in this sort of a project are not likely to be (or need to be) fine furniture grade. Anything passably close will be good enough. So, give the builders the plan and let them cut and assemble using whatever technique they think will be easiest.


Thanks Mac, As I am using this project as a learning tool for sketchup it is always good to find out some new ways of doing things so will have a look at the plug ins.


Think there needs to be some clarification on what you really build. I posted earlier but then erased suggesting the openings are cut in place, but if real logs which can weight as much as 8 lbs per foot I question in my mind the design would really take that load , but then concluded you are making a Halloween part type of thing and then concluded you are probably going to use card board tubes, the joiners are lay persons no back ground in laying out and cutting ARCs etc in place. For my peace of mind what is it?


Hi Mac,
Good Question!!
This is a non prescriptive play structure designed as part of a development in a multi age special needs school in London. The idea is that it has a ‘maze’ element and allows many different types of movement and free play for children with a wide variety of special needs including wheelchair users. It provides a ‘backdrop’ for group or individual play with trail following, hide and seek type games and gross motor play such as scrambling through tunnels, reaching and throwing etc… To be constructed from 100mm diameter machine rounded timber, set in to a base.
That was the idea anyway! The reality is proving more complex… I took advice from others that had answered my post and showed designs to joiners without bothering to create a ‘flat’ elevation (I wondered if anyone had an idea to do it easily - but not worth messing around with I think) - thanks also to all that sent suggestions I’m sorry I haven’t answered all yet.
Various ideas but not sure will be able to construct. Joiners have suggested window ‘frames’ of me sort but cannot work out how to support the structure safely above arches and windows (as you have pointed out)… Still thinking but not sure how long to pursue, and how to redesign. Annoying thing is client loves it… I work with some great builders and craftsmen so maybe we’ll solve it!
Thanks so much for your comments,Jeniflower


Hi Gully,
Thanks for your considered reply and thoughts on planning. Now it’s so easy to send plans etc I probably send too many! Prior to this project all my plans and designs were hand drawn and illustrated, so big learning curve.

Help and tips always much appreciated,


You are so right…


Have you done search on web for timber frames ? I would guess they will give the best idea on how to go forward. They will have background in log home framing. Setting the logs and then cutting holes is the way to go, the layout is not that difficult almost like lofting =>simple long thin boards, three nails to set to points; buldge / center and two at sides for the template boards to slid on, like tracing out a number of cords. Almost every opening is none planar but they can handle that I hope.

Quick search turns up very few log home circular widows. Those shown the logs like all homes are laid horizontal, the logs then are some what like stones you see in the old aqueduct designs they are self supporting.


Good steer, will look.
Joiners have suggested a metal plate above all openings sandwiched between 2 half rounds, will be strong and invisible. Think this is the solution we will go with this time, although can’t help feeling a little over engineered… Jennie PictonJP DesignMobile: 07894 163510


Not stress engineer here but think of the down side if not correct. I have seen some post folks making Finite Element Model with SU and then if you have loads and allowables you can calculate margins of safety. What I have been associated with ( Aerospace type designs) we start at initial design with margins of 2.5 and as design progresses that keeps getting reduced down to ~1.25 etc for final design and build, but loads and environments ( often not well defined at start ) much worse than you will have. Guess that will depend on your locale code requirements if any. Pics I found of log homes did not appear any had steel beams but logs were laid horizontally so they have some what self support ?
Good Luck