Sunday, May 29, 2011

Buying materials.

So, I used some hilariously low quality wood on the frame.  In several spots it's split.  Or cracked. 

This does not worry me as the frame very efficiently transfers stress to other slats if one breaks.  However, I would like to repair those broken, or weak slats.  The method I'm choosing to do this, is superglue, and splint slats. 

I bought the glue, and 900 yards of thread today.  Hopefully I'll get to use both. 

Friday, May 27, 2011

Erections. Really.. getting wood to stand up!

Well, not getting wood.  But getting wood to stand on it's own.  Tonight, at 8:15pm, the 27th of may, my yurt stood on it's own.

But first, rafters.  The rafters needed to be notched, and trimmed.  The math said they had to be 6'4" long, so they would rise 2' above the walls.
 I bought 7' lengths of wood to turn into rafters.  I'm not surprised I ended up with 8' leftovers. 

At some point, I'll post pictures of the notches.  The notching process was easy.  Since the center ring is 12", I measured 6" in from the end of each rafter and marked out at 3/8" wide slot.  I cut 1 blade depth deep on each line with my sawsall, and knocked out the bit of wood between the cuts. 

The pins that go into the ring at the center are just screws.  Normal 1.5" wood screws.  Again, I"ll get pictures later.

So for the money shot.  Here is the yurt, standing on it's own.  You can see the metal cable I used for the tension band.   I bought 1.5" long screws for the top of the wall just to have the excess length sticking out for the cable to sit on. 
 Next step, is making a shell for it.

Ringing it.

So to make the roof of a yurt work, you need a compression ring in the middle, and a tension ring on the outside.

I made the inner compression ring first.  I had a 36" long piece of 1/4" thick steel on hand.  I knew I was going to skip a rafter over the door, so  I would have 13 rafters.  I did a little guessing and checking, and found 2.5" between rafters would be about correct. 

I marked it out...
 Marked every 1.25" because I did my math based on filling all the rafter slots..
Out came the angle grinder, and I cut every other space open to accept the pins from the rafters.

I figured trying to bend 1" of steel would be a little difficult, and cutting an inch deep wasn't going to happen with my old angle grinder wheel.  It had to be replaced....   I seem to go through angle grinder wheels roughly every six months.
Hah, you can see the cut off bit of the main wall.  I got to do some vague sort of metalwork.  A big vice, and a hammer.  The notches that were cut into the bar made bending the ring fairly easy.
The ring was then drilled, and bolted.  Well, we'll call it pinned.  I had to clean up the notches, because the act of bending them closed the slots a bit. 

I'd have pictures of the outer ring.. but making that was really dull.  I drug the wire out on the sidewalk, measured it with a tape measure, and put the cable clamps on it.  You'll see it in the next post.

Walls and doors.

Well technically, a door.  The wall was shortened too.

Two posts previous I mentioned a mathmatical error.  This means I had to shorten the walls.  The yurt is now exactly 12' diameter, instead of 11.5'.  And it's 27 bays around.  Two bays are taken up by the door.

The door is very simple, just a square frame made of the same material as the rafters.  I will be adding corner blocks to make it a little more rigid.  But that's it.

I was very proud of this moment.  For two things.  First, the walls were done.  Second, I set it up all on my own.  It wasn't very quick... but it was all me.

Next up, is making the top tension cable, and the roof ring.  

No tablesaw, No problem.

In the interest of getting things done quickly I decided to rig up a saw so I could rip boards at home. 

Sometime, long in the past, my mother bought a circular saw.  It's been in the box for 10 years.  At least.  when I pulled it out, the sled was rusty, but the blade still had wax on the blade tips!  This new "old" saw, and my workmate came together to make a table saw.
So, in the interest of safety, I used a power strip as a remote on/off switch.  The 1"square tubing made for a really nice rip fence. 

Remember my warning about dust?  I did something about it.  I bought a $40 dust mask.  Combine that with a hat, and a $9 JT flex 7 clone...
Instant safety!  I wouldn't use those goggles on the paintball field.  But they're just fine for dust and shop type flingables protection.

I made 15 - 1.5"x1" wide boards.  Most of them were 7' and a three were 8'.  The 8' ones are destined to be a doorframe. 

Next post, is a door, and trimming the walls to the proper size.  

Tuesday, May 24, 2011

Yurt Math, and getting it wrong.

Here, I was all ready to sit here and write up all the math involved with doing a yurt. 

And I found a mistake.  I built my wall with 1' squares.  Now, if you have two 1' lines, with a 90 deg corner between them.. the distance between the furthest points is 1.41 feet.  I based my math on each bay being 1', not 1.41'. 

The wall I built is the right size for a 15' diameter yurt.  Sadly, BB didn't buy enough canvas for a 15' yurt. 

Allow me to illustrate:
Please, excuse the whole mspaint thing. Figure one is something i just know off the top of my head.  It's a long story as to why I know that, but I know that equal forces 90 deg from each other, gives you 1.41 times the force involved. 

Or in this case, 1 foot x 1 foot gives you 1.41 feet.  I feel dumb.  to have built this yurt properly, I would have needed to build the slats with holes spaced 8.5" apart, instead of 1' 

Next time, we'll cover the whole set of calculations to build a yurt.  Really.  I promise.

Sunday, May 22, 2011

Yurt links, kinks, and opinoins.

So, I thought I might post some yurt informational links. 
I like these guys.  If their site is to be believed, they build quality, permanant, yurts.  They use the right materials, they have engineering drawings, and they have realistic expectations both for the use, and survival of their buildings. 

What I really like about them, is that I saw how they attach their rafters to their walls.  And it's exactly how I planned on doing mine.  Which I had never seen before.  I'm glad to have my choice vindicated.
Wikipedias yurt entry.  It's a good introduction.  It doesn't go much into the construction, but it shows the different kinds.  I didn't even know that curved rafter yurts existed.  Thankfully I knew I was going for a mongolian style yurt anyway, so I'm not disappointed in my rafter choice.
This is the best instructables on building a yurt.  I think I may need to write a competing article there.  As they didn't go into the math on how to build the "yurt you want" instead of "the yurt they built." 

I have read most of what's out there about yurts, and I haven't been exceedingly pleased.  Most yurts are made by super-eco-friendly people, or hippies.  That sort of person usually is far removed from any sort of engineering background, and is more of the guess and check type.  Which in the end, means you need to be the guess and check type.  For instance, the instructable says "almost 300" screws. 

That, is not, me.  I'm glad they built their dwellings, but the instructional, and websites that have sprung up around them are not all that useful.  I think one in seven of the sites addresses how the roof actually stays on.  And I only know of one that puts real consideration into how well the thing seals. 

Most also don't address how you keep the yurt from becoming airborne in heavy winds.  ....  I have a plan for that. 

Next time, we'll talk about math.  :-)  SocCahToa....

Putting up walls

Later on thursday, the work crew that's working on the kitchen showed up.  I had to move my wall.  Here's where I was then...  

I didn't want to stop, but I had run out of space to work on that in the garage, so I took it outdoors.  I figured it was long enough to stand on it's own.  And due to a miscalculation in screw orders I found out I needed to remove some 60 screws.... 
Ooh, it stands on it's own.  When the wall is standing on it's own, it's so much easier to work on.  So long as it stands.  The wind can make that a little sketchy...  I was really proud of this moment.  It finally felt like a structure.
 You can't imagine the looks I got from people driving by.  I love doing "WTF" projects in public. 

Sometime around 7:30pm I decided the wall was done enough, that I could consider building roof slats, and a door frame.  But before that, I wanted to play with my yurt a bit.  I called upon the assistance of my mom... who's only seen these on tv. 
She's 5'6".  Feel free to use her as a yard stick.  This isn't the smallest the yurt will roll, it's just the smallest I dared when I did that.  I rolled it up so I could carry it into the yard.

And that's where we stand with this project.  It looks pretty good to me.  Once it's setup like that, it's quite stable.  I have two more slats to make, or trim, so the walls will be complete.

I need to make a door frame.  I bought eye-bolts so I could permanently affix the middle tension strap to the walls.  I will be stapling a nylon tension strap along the bottom of the wall.  And then the roof/top of roof strap is going to be 3/16" steel cable. 

After that, comes the roof.  Technically I may be making the roof slats before finishing the walls.  I need to make those down at pumpingstation.  ... and I may as well make the door frame there too.  They have better wood working tools than I do.  I'll bet I can do all of that in a couple hours.

Where that stack of wood came from...

Well, i'm not one to let "all" my projects languish at once.  I had a really funny day on thursday, and that meant I got lots of time to work on yurty things.
 That's the wall of the yurt at 7:25am.  The stack of wood came from trimming the ends of all the slats.  That took the wall down from a full 8' down to about 7'3".  I'll explain that math later...

Feeling hesitant

Holding up the roof worried me a lot.  holding everything up with some 3/16" slats seemed... scary to me.  I did the math.  I knew how much wood it was, logically.  But "seeing" it helps.  That's a lot of wood to hold up a cloth roof.


End of the third days work.

Day two. Well.. night two.

So the second night of building things started really happening. 

A decision I made during the design process, was to have slats every 1'.  This would make the planning easy. In the world of "close enough" math, I went with 36' circumference. I decided I wanted a 3' wide door.  That means I need 33 bays.
Oh hello slats.  But how am I going to put screws through you?  Holes!  Lots of holes.

Each slat has 8 holes drilled in it.  Measuring and drilling each hole separately would work.  But it would also take a lot of time.  33 slats, with 8 holes in each means drilling 264 holes.  That's a lot of measuring and drilling.  So it's time to break out the production line techniques. 

Templates are the key.  I have several slats that just aren't up to the quality of using in the yurt, so I have material to make one.  I did a little measuring, and...
The wood looks rough, but it's plenty accurate for the job.  Now the slats are very thin, so they need to be held straight, and not curved while drilling them.  Over an 8' length, the droop due to gravity makes the holes on the inner piece of wood almost a half inch off from the outer piece of wood. 

At first I did them singly, but by the end of the project, I was doing slats 4 at a time. 

To keep the slats aligned as I am drilling, I slipped a bolt into the holes.  Not every hole, usually every second or third.  This made the bundles more rigid, and therefore easier to hold straight. 
The wood I used was really low quality, so the slats are not very straight.  That's ok though, because there's 60+ slats they average out.  The curved bits only make themselves obvious at the ends of the wall. 

The end of day one's work.  It doesn't look like a lot.  But I was proud of it. 

Making mistakes, a word on safety.

First off, safety is important when making things.  Dust, chemicals, slivers...  It all can hurt you. 
 That is a lot of dust.  I expect another 1/3 of it was floating around in the room with me.  I did not take proper safety precautions when doing this, and ended up with a upper respiratory infection from all the dust.  I did wear protection for most of the job, but cutting the first board without protection was enough. 

I've made other mistakes over the years.  Everyone will get hurt eventually, doing something.  Never, ever, let yourself make a mistake and not learn a lesson from it. 

I bought a high end respirator.

Build night number one

The first night of building a yurt, isn't acutally building anything.  It's prepping materials.  In this case it means ripping seven 8' 2x4's into 1/4" thick slats.  Or at least that was my goal.  The slats acutally ended up between 1/8 and 1/4" thick.  Most of them were in the 3/16" thick range. 

This worried me at first.  .... And then I realized that even with 1/8" thick slats I will still have  8" of wood holding up my roof. 

Delta is my god.  230volts and 13 amps worth of table saw makes quick work of ripping lumber.  And old work friend of mine helped me with this part.  He was essential.  Running 8' long boards through a saw isn't exactly a safe activity if you're doing it solo. 

The room we were doing the ripping job in was only 15' across.  You'll notice the table is at an angle.  That's how we managed to get enough room to run the boards through. 
That's roughly 70 slats.  A few have ends that I can't use.  It took us about two hours to take care of this particular task.   I did this job at a place called PumpingStation: One.  They're a hacker space, and I'm proud to be a member. 

Driving a Mazda 6 with 8' long bits of lumber in it is not exciting. 

Yurt DNA - What's a yurt made of.

Well, what makes a yurt?

Usually a yurt is made up of sticks, which are lashed together using leather thongs, wrapped in felt, and canvas.  The floors are usually just covered with carpets.  

Mine.. well isn't like that.  It's going to be made of cheap 2x4's, ripped down to 1/4" thick slats.  Roof rafters will be done much the same way, but ripped to 3/4" wide boards. 

We'll get more into that nitty gritty as I show you how it's built.

Instead of using leather thongs to hold the slats together, I am bolting mine.  Because I'm a nutjob, I am going to bolt the slats at every joint.  The advantage to this is it will spread stress.  The disadvantage is that this will make the frame less flexible.   I expect this choice may come back to haunt me.

What else is a yurt made of?  Canvas.
Thirty yards of 5' wide 22oz canvas. 

And a whole lot of screws.  I got smart, and I threw the fasteners in a organizer box so I could easily access them.  On previous projects, I did something stupid and was working from the manufacturers packaging.  This may have been one of my smarter moves on this whole project. 

There's also tyvek, and some steel which haven't been purchased yet.  Steel box section for the roof ring, and for the tension bands. 

Yurt Planning and Decisions.

We will get to the why later.  But, on short notice (roughly two months) I was tasked with building a yurt.  Mostly by myself. And I needed room to sleep 4.  Comfortably.  The usual rule with tents, is you halve the number of people you can physically fit in the space to define what is comfortable. 

I've looked at yurts before, and am familiar with them.  I think they are really neat tents.  They are like primative dome tents.   The tent had to look period.  That meant we weren't going to be able to use really modern materials everywhere.  In the end we decided on canvas outside, tyvek inside, and polyethylene and carpets for flooring.  This should mean the tent will be waterproof like a modern tent, tough like it's Mongolian ancestors, and it will look right.

The yurt is going to be 12' in diameter.  The walls will be 5' tall, and the roof will have a peak 2' taller than that.  A 12' yurt will only really sleep six.  But we will have cots, so gear storage can happen under the cots. 

Oh boy, starting a blog with a text only post.... :-)  next time.. DNA.