This is just a preliminary writeup since it may take a long time until I can write out a proper plan. For the purposes of this post I will assume you are familiar with how to build a hexayurt out of OSB/plywood and wooden blocks.
I recently envisaged a way that a standard OSB hexayurt could be built by one person as opposed to the normal 2 person team doing most of the work and the brief 6-20 person roof lift. The great thing about the normal build is that everything can be worked our pretty much by eye and you can bodge a whole lot of it together. A single person build would need substantially more precision so that he could attach the blocks to the sheets ahead of time and know where to drive in screws later with no one else holding the other side or guiding him. Also no one needs to be trapped inside.
I was attempting to draw out my plans for how one goes about doing this. Normally I work and think in Solidworks. I would build it and then use a measuring tool to tell me exactly all the measurements I need. Incredibly useful when trying to figure out the dimensions of the heaxayurt once you move away from idealised geometry and add in all the modifications that make it useful. Sadly, I no longer have Solidworks since I am no longer a student so I had to try something else. Enter Google Sketchup. It seems unfair to criticise it since it is free but the tools are limit. There are millions of plugins available and I have downloaded a few but I haven’t had the time to go through them properly. If anyone can advise of a package or link that helps bridge the gap between Sketchup and a full featured program do let me know. I have searched throught he internet and sketchup does seem powerful and capable of meeting my demands. I just have to spend time with it. However, I feel that the heirachy is too limited and the interface buy attempting to be overly intuitive makes it less so.
Well my first attempt was to make the sheets and then place mates and constraints that would force everything into place, sadly Sketchup didn’t have those tools or I dind’t know how to use them and after playing with it for a little while I gave up. The following will be a mashup of my attempts of illustrating everything.
Down to business
Anyway here is the basic idea. I hope to write a full plan from beginning to end later but for now I will tackle the problems faced when building a heayurt alone and the solutions. I should mention I am trying to make this as low tech as possible, metal brackets and bolt fitting would make the whole process easier but I want to rely on as little as I can get away with.
1. Securing the wooden blocks without the extra hands
Simply measure everything beforehand and mark. I was hoping to use the program to figure this all out for me but it seems like I will have to use my brain.
Also attach the wooden blocks beforehand onto one sheet before putting the sheets in place and joining them. Take into consideration the way the roof is layered to be reciprocating.
2. Supporting the roof during construction
With idealised geometry you could use one of the right angles triangle produced by cutting a sheet along the diagonal and it would perfectly support the roof until you needed the do the last side. At that point you can remove the supporting triangle. Depending on the surface you are building on you can use pegs, weight or friction to prevent the roof from splaying at you attach the final side. String or rope can also hold the roof in tension.
However, you can see that once an overlap is in place the supporting triangle’s hypotenuse greatly exceeds that of the edge it is joined to. This is solved by increasing the downwards length of the wooden blocks that join the roof to the side.
3. Strength of the joints of the last roof panel
The joints of the last roof panel can be too far away for one person to reach. Place a beam high up that runs between the neighboring sides before placing the final side. Also use 2-3 joints towards the middle between the side as opposed to the normal joint high up.
4. Getting the roof ontop
The answer is to build the wall underneath. With joining blocks between the roof and walls extended for problem 2 getting underneath is easy.
OSB weighs approximatetly 20 kilograms dependent on country. Some places use 1/2 inch (12.7mm) others use 11mm etc so its variable worldwide. With 6 sheets on the roof and a little extra to account for the blocks and screws minus a bit for the little pieces cut off lets call it 130kg. Since you will be lifting it at twice the distance as the center of gravity pushes it will be equivalent to lifting 65kg. Ever lifted an average human male (77ish kg)? Perfectly manageable if a bit unpleasant. Screw the wall into place with the wall sheet sitting against the outer side of the block so that the weight of the roof holds it.
Do the same with the other side. It will be slightly heavier but still manageable. During the entire process use pegs, weight or friction to prevent it from slipping.
5. Will it be stable enough?
As you can see from the front view the weight will be concentrated in the middle so side to side stability is not an issue.
However, from the side view it can be seen that the weight of the will place major stress onto the walls to roof joint. It will create a levering action onto the joints. This is encountered when first placing the two wall sheets underneath and if put under any sideways force, e.g. wind, as well as the weight of the roof being too far off-center. The only ways I have thought to solve this is reinforcing the joints, using more joints and using stronger materials. However, this will need field testing to determine how far these measures should go.
The rest of the build should be pretty straight forward.
A better more professional writeup is on the way with measurements and calculations. Hopefully a field test if I find a place to do it and someone to fund the materials. Then onto figuring out if H13 can also be built one man.
Please do comment and tell me of any other problems you foresee as well as answers to my CAD program woes.