How much bend in lattice walls

[Robyn]

I’ve had to change plans, as the timber yard is no longer open I will be using coppiced wood from the woods where I live. I’ll have to bend it how do you calculate how much bend to give the wall poles

[Bob Rowlands]

I don't know the math equation.

Here is a carpenters empirical way to measure the lattice bend. You need to know the wall height of your yurt when erected, the diameter of the yurt, and the focal point length, which is 1/2 yurt diameter. You need a straight edge, and the extended blade on your tape measure will work.

Find a flat spot like a garage floor or basement floor that you can draw out an arc of the footprint of your yurt wall when erected. Even dirt around your house will work. A basketball court in a park. A slab somewhere. Anyplace you can draw an arc.

Example. If your yurt is 16' diameter, use 8' as the focal point. Draw an arc several feet long.That arc represents the yurt wall curve in the installed position.

Draw out enough arc so that you have a point to point distance on the wall curve that equals your wall height. Not your lattice length, you WALL height.

Say your wall is 7' tall. Make a mark on the curve. Extend the blade and lock it at 7'. Set the blade o your mark, and sweep it side to side until it hits the wall line, and leave it on the line. Leave the tape sitting on those two points.

The widest distance from the arc to your tape blade at mid point of 7', will be the amount of bend in the lattice. At 7' wall height that's 3.5'. If the wall is 5' tall, it will be at 2.5'. At 6', it will be 3', etc.

Now this assumes you are installing the lattice at a 45 degree angle to the ground, or in effect making square shaped lattice, not diamond shaped.

Add a couple inches to that number because those steam bent coppiced shoots will lose some bend once you pull them off the three formers. The tighter they are bent, the more they will spring back.

This is all real fancy. A guy that makes steam bent trad yurt wall lattice is just gonna bend them about a half foot and know that it's gonna work. Have fun building your yurt.

[James]

I am not sure about the math, but what I do is take the length of my lattice wall pole, sit two poles in the ground, so the tips of the lattice wall poles maybe and inch or two in can rest on them put a pole in the ground smack down in the middle get a long pvc pipe that you can cap on each in see how much pressure it can take put a pressure release valve on the end where the cap will not come out, put a intake hole at the end where the cap is removable, hook that up to a teapot full of water sit a fire underneath of it to get it to steam put your lattice wall poles in the pvc pipe, put the steam to them, get heavy gloves cause wood will burn you, weave the lattice wall poles thru the ground poles that are sit in a straight line one on the right side of the center pole one on top of it but on the left side, keep alternating like that all the way up your poles. have fun.