November 2009

This is a shaving horse, I made it of some leftover wood. It is basically a clamp for greenwood carving.  With your feet you push down on the lever that clamps the wood down so you have your hands free to use a two handed drawknife.

A drawknife has the advantage that you can take thick shavings off, while still have control and precision. You grab the drawknife and pull it toward you while your feet push against the lever and fix the wood in position. Therefore is physically impossible to cut yourself this way, it is possible to fall of the shaving horse.

I’m still experimenting a bit with the clamp itself, I used a piece op round wood now. But in retrospect it might be better to use something with a hammer shape that has a bigger clamping surface.

See more shaving horses here


Does the boat tail work

The boat tail, is a simple tapered extension on a truck and saves 7,5% fuel. Considering that there is not much more efficiency gain on the internal combustion engine, 7,5 % is a lot.

The man who came up with this idea, Gandert van Raemdonck, says: “In the ideal situation the extension should be 10 meters long, but that wouldn’t be very practical”. It is still in testing phase and right now you couldn’t access the loading ramp or open the doors of the truck. All of this can be easily solved.

Another reason that makes this idea good is that it can be retro-fitted on existing trucks. And even more important, this idea will also save energy on future electric trucks.


Well, does it work enough? some simple Maths!

 How much is 7,5% fuel reduction, sounds like a lot right?

In the Netherlands there where 19.800.000.000 (19,8 billion) road-freight km a year in 2006, that is a lot for a country that is only 350 km long and 200 wide.

Lets make this a more comprehensible figure. 19,8billion/365 = 54.246.575 km each day

54.246.575/24 = 2.260.273 km each hour.

2.260.273 / 60 = 37.671 km a minute, there is a figure that we can work with. That is just slightly less then 40.074 km which is the circumference of the earth.

So each minute in the Netherlands, trucks transporting stuff almost go around the earth!

After some research on the internet I found out that a “normal” truck uses about 26 litres of fuel for 100 km on long distance driving. So If the freight kilometres where driven with this “normal” truck then they would use 37.671/100*26 litres of fuel. That is 9794 litres of diesel each minute.

Now, diesel is more or less C16H34. Molecular mass is 16*12 + 34 = 226. 1 litre weighs 830 grams, that’s 3,67 mol. If you burn this it would give you 3,67 * 16 = 58.72 mol CO2. So per liter diesel that is 58,72*44=2.583g or 2,58 kg.

So 9794 * 2,58 = 25.269 kilos of CO2 each minute because of trucks in the Netherlands, that is 13.281.386.400 kg CO2 each year!

If we are talking about a 7,5% decrease of fuel consumption, (9794*0,925) * 2,58 = 23.373 kg of CO2, Almost 1896 kilos CO2 less each minute. Still 23.373kg/minute is a staggering figure.


My conclusion.

Alltough a 7,5% decrease in fuel consumption is quite good, also because you can retrofit this on every truck in the world. I would say retro-fit every truck now.

According to the IPCC we would have reduce the GHG 80% of year 2000 level to sort of stay in the clear. So, it would not make enough difference in the larger scale of global warming. The only real way is to cut the transport down to 20% of 2000 level, and then, with the boat-tail you could drive 7,5% more then 80% of 2000.


I assumed that all road freight km are done with trucks, but there are also vans and cars involved. They have a lot less fuel usage but also carry less freight. These are just kilometres driven, not tonnes transported, so efficiency of each type of transport is also not taken in account. It is very raw data.

These figures are for the Netherlands, a country the size of a post-stamp, imagine Germany, the U.K., France or U.S.

For the UK it is 156 billion ton/km in 2006. If a truck carries 10 tonnes it would be 15,6 billion km a year, assumed again that it is all truck and they are fully loaded.



I had a go at knife making, I promised a couple of knives as presents but, I still had to try if I could actually make one. Well this is prototype 1. The blade is a Sami type, the handle is oak leftover from making a table, antler from a caribou and some leather.

I made the handle puukko style, a  tool for cutting food, wood, leather, hunting and fishing.  The knife lacks the hand protection that you see on many other knives. That protection is ment to keep your hands from sliding down the edge and thus hurting yourself. However this is a working knife not a stabbing knife. The guard would be pointless. I even think that the guard is in the way when carving wood.

Grip on the handle is maintained by the oval shape of the handle. The thick part sits in the palm and the thin part is grabbed by your fingers.  You can also see that same shape on my woodcarving knife here. It works very well, you have more flexibility how to hold the knife and you can push the knife with your wrist.