The Twelve Foot Yurt

The ten foot yurt has had a few outings in the past few years.  It worked well but I thought it could use a little more floor space in conditions where we wanted to use part of it as a kitchen. So I set to work on the design of a twelve foot version.

A twelve foot diameter, vs. a ten foot diameter would give this yurt 44 percent more floor space.  I decided to keep wall height the same so that I could re-use the existing wall lattice, needing only to add another 6 foot section of wall to bring the circumference up to 37 feet from 31 feet.  

I tried to figure out ways to re-use the existing roof parts, but that was not possible.  Still, re-using the existing wall parts and door cut down considerably on the total amount of work.

So on to some pictures.

Here's the sewing studio for the roof. I tried sewing the roof on the floor of the living room at first, but the large hunk of canvas kept colliding with various furniture.  Having the large flat area of our driveway to rassle the canvas was a big plus. The other thing I learned from the ten foot yurt was to soak the canvas in water and let it dry to shrink it before cutting and sewing it.  Shrinkage was mostly along the length of the canvas with very little across the width so trying to get a good fit without pre-shrinking the canvas would have been a challenge.

 This photo is of the trial assembly of the yurt in back of the shop. Looks good enough.

 What you are looking at here is the extension of the wall canvas joined to the existing wall canvas from the ten foot yurt.

 I also decided to add a skirt to the interior of the yurt to minimize the amount of sand blowing into the yurt in windy weather.

 And this is the tono or roof ring.  I made the roof poles a little over long so minor changes in length wouldn't have them pulling out of their sockets.

 Here's the twelve foot yurt pitched in front of the original 16 foot yurt.  Note the difference in roof pitch.  I wanted to experiment with a lower pitch on the twelve footer to keep interior volume down for easier heating.  The new pitch was 30 degrees vs. about 39 degrees for the 16 footer.  A lower roof also makes for easier setup of the roof.

 I also decided to make a door frame for the door cover, an upgrade from a simple flap that hung over the door but was a nuisance to go in and out of.  The assembly of the parts is tongue and groove for reasonable stability combined with ease of disassembly.

 Once I was done, I dragged all the yurt parts outside to weigh them.  Total weight about 198 pounds.  Not suitable for backpacking but OK for car camping.

And here, the yurt deployed in the Mojave National preserve.  We wanted an open roof for star viewing at night but rigged a table cloth for shade during the day.  

The Yurt Gets a Door and other improvements

The sixteen foot yurt has lived for over a year without a door.  But now that it has a stove, I discovered that the yurt loses heat quickly without a door.  Actually, I already knew that, but since my improvements on the yurt tend to be on a just in time basis, having a source of heat made a door imperative.  The first stab at a door was to just staple some pieces of vinyl banner to the door frame, but in a wind they were practically useless.  So the next step was to build a door with a wooden frame, something more substantial that would actually keep the drafts out.

The stove, blazing away.

The stove pipe now has a hat which keeps the rain out of the pipe but the smoke hole needs some flashing around the pipe so the tarp that covers the hole in the rain doesn't get melted by the heat from the stove pipe.

One of my neighbors at the shop has donated a chair, a mockup for the console/chair for the boat he is building.

And here is the new door, a wooden frame with a piece of plastic banner stapled to the front of it.

And here is a view of the door from the outside. Love that shanty-town look.

Closeup on the latch mechanism. The string goes through a hole on the top and another on the bottom.  When outside the door, you pull the top string to pull up the latch or the bottom string to pull the latch down. 

By the way, the yurt has now withstood 65 mile an hour winds and survived.  Little by little, small improvements make it a better structure.  Surprisingly, the most challenging task was how to keep the roof in place since wind going over the top of the roof creates a vacuum which wants to lift the roof cover up and then blow it off.  An improved tiedown system did the job.

Yurt Design - Canvas Shrinkage

Canvas shrinks.  I knew that. So when I designed the roof pattern for the yurt, I should have allowed for shrinkage but didn't.  Oh well, nothing that can't be fixed with a little more sewing.
Not only didn't I allow for shrinkage in the roof, I also didn't realize that the canvas shrinks unevenly, more along the length of the material than across it.  Something to be conscious of next time.
Now that I think of it,  I doubt that I could plan for shrinkage in any sort of exact way since the shrinkage is non-isotropic.  I suppose I could just make a roof cover uniformly oversize, then when it shrinks, regardless of whether it does it evenly or not, it would still be large enough to do the job.
For now, not having tried to it yet, I am leaning toward pre-shrinking the canvas.  Unroll however much canvas I need, hose it down, dry it in the sun, then cut it up and sew it into whatever shape I need. Everything I haven't tried yet sounds like a good idea.  Whether it actually is, doing it will tell.
Meanwhile, some before and after shrunken roof cover pictures.

Before: the yurt roof cover on its maiden voyage in Kings Canyon National Park. I trimmed the fabric so there would be about 8 inches of overhang.  Sewing the seam at the edge reduced that by about an inch.  Other than the wrinkles which I hadn't dealt with yet, not bad.

After: Overhang of the roof fabric has been reduced to about 4 inches at the max and two inches at the minimum.  The wall fabric likewise has shrunk some top to bottom and side to side. Time to make some corrections. Canvas work is not an exact science.

Yurt Report - Wind Test

Two nights ago, the yurt underwent a spontaneous wind test.  A front with wind gusts up to 50mph moved through the area.  The bushes and trees were rattling against the fences and roofs and making a spectacular amount of noise.  And then I realized that I had recently skinned up the yurt.  It had survived the previous winter without problems but that was as a bare frame.  With the skin on, the wind would be able to exert more pressure on it.  I was tempted to drive out to the shop and check the yurt right away but decided to wait till morning to assess the damage if any.

Next morning I drove to the shop.  The first thing I saw was the flag down on the ground.  This wasn't a good sign. 

I went to the back of the shop with some trepidation but there was the yurt, still standing, albeit with the roof cover partly blown off.  This was no big deal since I had not sewn the final seam and the cover had a tendency to get blown off even in a light wind.

A few of the roof poles had also lost their moorings and fallen to the ground. I suspect what happened that made the poles fall down was that the flexing of the wall in the wind distorted the round shape of the walls into an oval, popping off the tension band and allowing the top of the wall to bow out to where the roof poles were able to pull loose.

The tension band, the green rope, is inside the wall instead of outside, apparently just rolled over the top of the wall.

Putting the yurt back together took maybe 15 minutes. So the test was useful, revealed some more of how the yurt works.  I already knew that the wall was a little too flexible.  Now I knew another reason why it should be a little stiffer, to not distort in a strong wind and allow the roof poles to come loose.  Also the roof covering needs better tiedowns, something I just hadn't bothered with yet.

Oh, and I untangled the flag and got it back to the top of the pole.

Yurt report - a new stove

The fire in the yurt test went well as reported in my previous post, but the guys at the shop were put off by the burnt potato smell left behind by the fire.  I told them that I would be getting a stove, but shopmate Tim said that we could make one on our own. I told Tim that he could because I don't know how to make a stove from scratch. Tim, said, let's go and off we went.  Chris, another guy at the shop donated a propane tank as the shell for the stove.  Progress so far documented below.

Tim cutting an opening for the door of the wood stove. Before we got to this point we had to vent the tank to let remaining propane escape, torque off the valves and flush the tank out with water to force all the propane out. Tim did the cutting with the tank filled with water.

Les is grinding away tack welds he put on to hold the door in place while he welded on the hinge for the door at the left.  Legs are already welded on.  Legs were cut from scrap angle iron.  It's good to have scrap laying around and neighbors who can weld.

And there it is, a small stove that looks like a bulldog.  Still remaining to be fabricated, a latch for the door and a hole cut in the rear and a flange for attaching stove pipe.

Yurt Report - Fire Test

Another update on the yurt.  As my shop mate Tim said, I liked it better when you were building boats.  Still, yurts is what you get for now.  This report is on the fire test, that is, on a test of whether I could build a fire in the yurt without choking on the smoke. 
But first, some outside views of the sixteen foot yurt with a skin on it.  This skin consists of big plastic banners that have done their duty.  They consist of a fabric substrate that is then coated with some sort of plastic.  On this, the graphic is printed. And when the date for the advertisement expires, they are tossed or handed off to some recycler. I got these from my friend Tim who got them from a neighbor. So yes, they're  recycled.

I don't know why, but this particular skin gives the yurt a decided third world look.  Maybe it's the ragged edge on the roof and the dirt on the white banner and the advertisement on the outside.  Looks like a place where you could buy used motor oil.

With just the white wall showing, the place looks a little more dignified.  Ropes that hold the roof and the wall in place courtesy of a friend who sold his sailboat.  Also ropes abandoned by fishing boats and washed ashore at Point Reyes National Seashore.

As I said, this is a test, the 16 foot yurt being a prototype for all aspects of the yurt technology. So far the test of the banners as a covering material has gone on for about a year.  I have already been using the banners as a cover for my kayaks.  What I found out is that the plastic deteriorates within a year, probably at the same rate as those ubiquitous blue tarps sold everywhere.   So I would probably use these plastic sheets only for temporary installations.  The amount of work to do a good job on covers isn't worth it given the short life of this stuff.  Still, for prototyping, they are just fine.  Beside the short lifetime of the banners, another major shortcoming is that they are heavy and stiff, especially in cold weather and getting them installed is quite a chore, especially for the roof.  The walls are not a problem.  There the stiffness is an asset. Plus you have to not be put off by whatever commercial message is printed on the banners. 
And now for the fire test.

The fire in progress with a bucket of water standing by just in case.

Here it is, the fire.  While the fire got going the yurt filled up with a good deal of smoke because the fire wasn't creating enough heat to generate a good updraft that would pull the smoke out of the smoke hole.  But once it burned nice and hot, the smoke was minimal, but that was with the door open.  I will have to do more testing, but I would say that with the door closed, you wouldn't really want a fire inside.  But then, having a fire would hardly be of much benefit. 
Also, this yurt is quite tall with 64 inch high walls and the smoke hole at about 10 feet elevation.  So this is a fair size space to dissipate the smoke. So for now, recommendations are, keep the sticks small to minimize smoke.  Get the fire going good and hot before you invite anyone inside the yurt, ideally, you would build up a good bed of embers first so any new wood on the fire would burn quickly without a lot of smoke.
Or get a stove. I ordered one and will report on that soon as I get it.

Shortly after sunset with some color remaining in the sky and the San Francisco skyline in the background and the tail end of Alameda in the foreground just past the yurt. 

Pretty much the same shot as the one before but with the sky just a bit darker and the yurt lit up just a little more. Either I stoked the fire or the sky got darker and the camera gave the whole picture a little more exposure.  In any case, the yurt is positively glowing.

The Camping Yurt

I built a ten foot diameter yurt suitable for camping.  The ten foot diameter seemed suitably large for comfort but not so large as to provide a transportation problem and also not so large as to overflow available camping spots. Our intent was to give it a good workout in Kings Canyon National Park.  By and large, it worked out with minor problems.  Pictures and comment below.

This shot was meant to show how small the yurt looks in a natural setting.  It looked much larger when I first set it up in the driveway of our house. We left the roof cover off so we could look at the stars at night.

Here is a picture of the yurt in the afternoon when the sun is hitting it.  We peeled back the wall for better air circulation.

Here is the yurt with the roof cover on.  We may still sew darts into the overhanging portion of the roof to take up the wrinkles.

After we got kicked out of Kings Canyon due to government shutdown, we found a camping spot in Sequoia National Forest right next to a Jeffrey pine.

Here is a longer shot of the yurt to show its size in proportion to the pines.

And then it snowed.  Clouds moved in in the morning and we put the roof cover on.  I had not yet made a smoke hole cover so a plastic tarp had to do the job.  The snow all melted once the sun came out.

A closeup on the tension band that holds the top of the wall in against the pressure of the roof poles.

And a closeup of the roof pole to wall junction.

The tarp leaked a little since laid flat over the smokehole ring to which I had not yet added any arch.  Here I have added some willow twigs to remedy that problem.

All in all, we were pretty happy with how the yurt behaved.  Next addition, some flooring to isolate the bedding from the ground and a small wood stove for heat.

Skin on Frame Housing - the yurt gets a roof

Progress on the yurt continues.  Much of the progress is imperceptible to anyone but myself but the progress is there.  As it turns out, my initial suspicion that my first yurt would be a prototype for working the kinks out of the design turned out to be true. So let me share what I've discovered so far.

 I got the crown on the central ring of the yurt.  I used some kayak rib stock, 1/4 inch by 3/4 inch white oak, socketed into the central ring and lashed together with tarred seine twine. The idea behind the crown is that it will be open under normal conditions but covered when it is raining or heat needs to be kept in the yurt.
Another discovery I made after the initial assembly of the yurt was that for the sake of getting a good setup it helped to trace a circle on the ground first before erecting the walls so that the walls would form a perfect circle.  The perfect circle is essential so that all the rafters are the same distance from the central ring.
I also discovered that I had much more wood in the central ring than I needed and so it was too heavy and difficult to get into position when no help was available. What I did to remedy the weight problem was to cut some of the extra wood away from the center of the ring.  It was way stronger than it needed to be. 

 The next step was to cut out some fabric for the roof.  It took me some time to work out the trigonometry for the roof cover shape, but I did it.  But I have learned to distrust theory and test with an actual life size cover.  The other reason for getting the cover in place was that a series of rain storms were coming into the area and that would be a good test to see how the cover would stand up to the wind.

Here's an inside shot of the cover.  The wind lifted it some and pushed it off center.  Part of the problem is that the shape of the cover is like a pie with a wedge cut out of it and the edges adjacent to the missing wedge get pulled together and glued or sewn resulting in the desired pyramidal shape.
The cover is made out of some sort of vinyl covered fabric that is used for advertising banners.  A friend gave me a bunch of these banners and I cut them up to fit the roof. The fabric has two problems.  One is that it is very heavy and the other is that it is very stiff.  The combination of weight and stiffness makes it very difficult to pull this stuff up on the roof.  The weight also works against its portability.
On the plus side, the cover survived the storm and did not get blown off.  I also discovered that once again, there is nothing like building something to test a design because until you do, it's next to impossible to know what sort of problems the design has.  So far, none of the design elements have been complete failures but lots of them can use improvement.
The list so far.
The wall battens are slightly too flexible.  A bit more stiffness is advisable even at the expense of greater weight.
The skin is too stiff and heavy.  Lighter weight is advisable.
Other commitments have kept me away from the yurt, but the learning continues.  I will continue to post whenever there is progress or even when design ideas fail.

Yurt or Skin on Frame Portable Dwelling

I haven't done much boat building lately since I have been busy working on a yurt.  Though this blog is supposed to be all about skin on frame boats, I thought it would be OK to indulge in some related skin on frame construction, namely, the yurt or portable dwelling.
The idea of building a yurt came to me after last year's October camping trip.  We were pretty far south but at high elevation and so we encountered snow and cold nights at times.  We had an adequate tent and warm sleeping bags but the sun went down early each day and then stayed away for twelve hours so that once it got dark there was little to do but crawl into the bags and listen to books on our mp3 players.  Camp fires and eating are usually good camping entertainments, but most campsites have fire rings that keep the heat of the fire away from the camper and otherwise hamper what should be a good entertainment.  Likewise, cooking food when it is near freezing is possible but once the food is done, it gets cold in a hurry and then you have to clean up in the dark and cold.
So the idea of a tent that was big enough to stand up in and build a fire or set up a camp stove in and cook in and eat in, all in comfort and warmth wormed its way into my consciousness.  The idea of a tipi came to mind, but those require long poles and a lot of canvas and would add a lot of bulk to an already bulky camping load. So then I thought about yurts.  And as a little research showed, there were lots of articles on the topic on the internet. 
In addition, my neighbor, Tim Anderson had built a yurt and so I could use him as a technical adviser.  So off I went on the yurt adventure.  I quickly found out when doing the research that everyone builds yurts their own way and nobody seems to tell you much about general principles like how strong to make the walls or what the pitch of the roof should be, whether the thing will hold up to a snow load, heavy winds and so on.  And so I decided to build a prototype yurt that could sit behind the shop.  I would use it to work out the design details and once that was done, I would build a smaller more portable and lightweight yurt for camping.
So here goes with the photos.

 The target diameter of the yurt is 16 feet so I needed to construct 48 feet of wall.  Circumference of a circles is pi times diameter of the circle, remember?

Here's a closer up view of the wall with another semi-nomadic structure behind it.  Nomadic if movable by fork lift fits your definition of nomadic.  In any case, for the sake of convenience the wall of a yurt is usually constructed in sections so that each section is of a size that is easy to lift and not too wide to transport.

And here's a shot that tries to show the curvature of the lattice wall.  Hard to visualize this sort of thing until you actually build the wall.

Intersections of the wall slats are held together with clinched nails, that is nails whose tips are bent over and hammered down and buried in the wood.

Here's a view of the junction from the other side where the tip of the nail is buried in the slat.

And here is one section of the wall, all folded up into a 30 inch wide section.  When unfolded, this represents 24 feet of wall.

When the two sections of wall are joined as shown here (temporary joint made with clamps) the wall is complete.  And the 96 inch long slats at an angle make the wall 72 inches tall.

The other two ends of the two wall sections will get connected to a door frame, not yet built.  Note alternating colors of wood.  I had enough old redwood deck boards to make almost the whole wall but had to buy a few extra doug fir two by fours to top off the number.  The redwood was free and light.  The doug fir was about ten dollars total and stronger than the redwood but also heavier.  We will see how they hold up over time.
Stay tuned for door frame, roof and canvas cover yet to come.