First Time Yurt Builder - many questions

[ejb]

Woohoo, your build is awesome Knecht!

Are laths always "9 cross"? That would help me calculate how many laths I need to make the 20' circumference. I saw that you were short a few laths on your kana... how did you make your initial guess at how many you would need?

[Knecht]

Thanks.
I didn't have to buy any more laths, but the last shorter pieces by the door were made of lower quality laths that we had to lay aside before. If you have some right sized store-bought standard laths available, I recommend to pay much attention to their quality and handpick them. Avoid any larger knots, cracks and cross-grain pieces. Hold the lath horizontally and shake it some, or rest it on the ground and try to bend it slightly. If you hear cracking noises, leave it. If it tends to "hinge" in certain spot, leave it. If it breaks, well, leave it and make sure the shopkeeper isn't watching. This process will take time, but save you trouble later.
Also, when drilling holes for attaching the lattice together: pay attention to make the template lath as accurate as possible. A yurt will forgive many imperfections, but the khana laths really need to have the holes exactly where they should be.
Yes, our lath holes are about 9" apart, but as I said, if I did this again the distance would be bigger and the whole thing would have less laths and would be a little lower.
Another thing: when planning the holes, keep in mind you need the upper crossings form a V at the top - big enough to seat the roof lath into. You need to realize that the resulting V size will be affected by the width of the laths - the wider they are, the more length you need to keep above the top hole to form big enough V when crossed with the other lath. Hope that makes sense.
As for the initial guess, I've been counting that for a while, then my wife started correcting me, using a different method and completely messing my mind, so I just let her do the math In the end, she mainly used a triangle method:
1) you get your planned yurt circumference, minus the planned door frame width.
2) you realize how high your khana wall shall be
3) you calculate how long your khana laths must be to form a trinagle (rather a chevron) that will have the height you desire for your wall
4) you calculate what part of the yurt circumference will one such triangle take. Divide the circumference by this number. This will pretty much tell you how many "basic triangles" (as we called it) you need.
5) now decide how many crossings you plan on each lath (drawing a picture of two basic triangles with the "inner" laths helps a lot). Once you know how many laths will fill the triangle in one direction, you should be almost done. You know how many such triangles you have around the circumference, right? So, once you know how many laths you need in one direction, you double the number (as there's the other direction yet) and you should have your magical number. Add something as a reserve and go shopping...don't bother calculating the door area with shortened laths and such. When you get there, you just shorten them.
Hope that helps. I bet there are far more smart ways to calculate this, but this worked for us.

[Bob Rowlands]

Did you do your homework grasshopper? lol I hope so. My best advice for you is to >fully understand< I repeat..>fully understand< how to build the yurt, before you attempt to build the yurt, or you'll be wasting your time, your money, and then be asking the wunderkids at Home Depot when the next yurt build class is scheduled.

Just one build detail of big s pot full, is: For calculating wall length, if your lath hole centers are on 12", and the yurt wall is expanded such that your laths form squares in shape, not diamonds, the horizontal distance between any two adjacent lath centers is 16.97". a2 x b2 =c2. Savvy?

If you want a 20' d yurt, and the lath centers are 16.97" apart as detailed above, 3.14 x 20' will give the overall wall length-which includes the door width. Divide that by 16.97 and that will give the number of crosses that the rafters sit upon, including the 2 or three atop the door frame. Round up or down to get a whole number.

That number will also be the number of rafters if you have a rafter sitting on each cross. That also tells you the number of rafter 'slots' in your yurt ring if you use the kaminari plan. You can use that number to do the math on the ring, without having them show the ring and say 'do this that and the other'. You'll also know the exact diameter of your platform, not including overhang.

BTW, you can lay out the yurt in cross section on the garage floor and make a master rafter fit the specific ring height you've chosen for the yurt. Just lay your 1x4 in place and mark it. Voila! Piece of cake, eh? lol

Etc. Have fun. I've been a carpenter since 1973, and even so, I read and re read the kaminari plan until I fully understood it before proceeding. We're here to help. Good reading and good luck.

[Bob Rowlands]

Lets review the Pythagorean theorem. In 'new skool' math it's: a2 x b2 = c2. In old school math the Pythagorean theorem is: a squared PLUS b squared = c squared.

[hierony]

I would highly recommend Paul King's book "The Complete Yurt Handbook"--it is a good reference/place to start. He includes plans for 10', 12', and 16' mongolian yurts and those sizes again in bentwood yurts as well as lightweight 'weekend' yurts, covering most of the questions you asked, cover designs & sewing, to a quick yurt history and culture. There is a chance a library nearby has it; otherwise there's always amazon.

If you want a good place that goes over the math (including online calculators), check out Simply Differently's yurt blog/diary/calculator. You will find lots of pictures, explanations, ideas, and his experiences in the yurt.

I won't add to the math chaos here, though I easily could. I'd figure the khana number this way: decide spacing of roof poles, figure circumference of yurt based on diameter, giving number of roof poles; subtracting the door (~3') this'll give you the rough number of pairs of lathe. Add a few (5%?) due to doubling up/short pieces of lathe at lattice junctions.

The reason most online plans don't include 20' yurts is that they take a little bit more skill and precision to make consistently without liability issues. The quick and dirty systems can become too bulky or too light at that scale. If you can, check out lots of pictures of 6m/20' yurts and maybe visit some. Looks like Two Girls probably has some you could check out Mongolians used small wood with lots of redundancy because that's what they had available; American commercial yurts use fewer but larger pieces, because that's what we have and are familiar with.

If you're in Maine, I would guess there's probably an amateur mill or two around--here in N. Idaho I know some arborists that keep 10-15' sections of trees they remove and mill them up/use them for firewood. Can be a source of quality wood in the dimensions you'd like.