It’s been a busy Winter, although the midwinter blues got me badly this year, so it’s all felt like wading through treacle, and the last thing I’ve wanted to do is sit in front of my computer screen and write blog posts.

Christmas passed uneventfully. The “other parents” dutifully dropped off the respective children at mid-afternoon on Christmas Day. Interestingly both my ex- and Chris’s ex- have independently decided that this is the one day of the year that they’re prepared to make the journey to our place. For all the other twice-weekly handovers we’re both expected to make the 50-mile round trips in opposite directions to them. I guess they’re pissed off because they both expressed (with idealistic enthusiasm) the expectation that ditching their partners (e.g. Me and Chris) in the shit would lead them to lives of unending delight, whereas they’ve both found nothing but misery while Chris and I have had 7 years of blissful happiness together, and look set for many more. So their mean-ness with the handovers simply has the effect of making me feel even more smug!

The Chartered Engineer application is gathering pace. My mentor has approved the written part of my application now that I’ve cut it down from 14 pages to 7. Even so he says it’s a bit longer than average, but then again I’m a bit longer in the tooth than the average ambitious young engineer.

I had to submit that by a mid-January deadline in order for my employer to agree to pay the fees. The next step is an interview together with a 30 minute presentation on “any aspect of my professional work”, though it should highlight my “exceptional achievements and potential for leadership” … not words I would ever have associated with the “day-job that I only do to pay the bills and enable me to do what I really love”!

A simplified data flow diagram taken from my draft CEng presentation. Many of the “rules” of painted images transfer to readable technical diagrams: compositional balance, leading the eye around the page, colours expressing meaning, etc. I guess there must be artists who exhibit “fake” technical diagrams, just as there are artists who produce “pretend” industrial building fixtures. Not something that’s ever turned me on though.

The design of the “versatile garden structure” is moving ahead too. I’ve settled on some dimensions, entirely dictated by pragmatic concerns. Planning law dictates that the structure must be 1 metre from the garden boundary, so that cuts the potential width from 6 metres to 5. The cross-beams must  be 2 metres high to allow headroom for people to walk in. The total height is limited to 3.5 metres, again for planning regulations, so the angle between the roof-beams and the horizontal needs to be about 30 degrees. The cross beams must be 2.4 metres long to create a regular octagon 5 metres across, and the roof beams must be 3.2 metres long to make a 30 degree angle and meet in the middle.

I’ve also settled on a material: For a structure in a beautiful garden, to celebrate the beauty and fragility of our natural environment, metal didn’t seem right, though it would undoubtedly have been the most enduring and possibly cheapest material. Any hardwood should last 20 years or more though. Chestnut is apparently unusually durable when sunk into the earth, and I will have to sink the uprights into the earth for stability. It turns out that coppiced chestnut poles are grown by smallholders across Surrey and are relatively cheap, so that is what I’ve gone for.

But how thick should the poles be? The uprights have to be thick enough to support the roof beams, and the cross beams need to be thick enough to withstand wind stress. But how thick to make the roof beams?

We will probably have grand-children within the next decade, and one thing that grand-children will almost certainly do is climb up things they’re not supposed to. Thus I want each roof-beam to be able to bear the weight of 3 children. More precisely, the deflection of the centre of a 3.2 metre beam should be no more than 4 inches when loaded with 15 stone.

There is an engineering formula for this, involving a quantity called “Young’s Modulus” after a gentleman called Mr. Young who took an interest in such things. I didn’t expect this, but I actually managed to find a value for the Young’s Modulus of coppiced chestnut poles, and plugging this into the requisite formula yields a sensible number: 3 inches diameter. From this, the uprights must be 4 inches diameter and the cross-beams 3.5 inches diameter.

I found a coppiced chestnut pole supplier who could provide me with 8 poles each of the necessary thickness and length at a reasonable price. Chris and I hired a van and drove down to Surrey in the snow to collect our poles. And here they are, sat in the garden waiting for me to mark out the octagonal base points on the ground.

I rather foolishly bought exactly the right number of poles for the proposed structure. I wish I’d bought some spares, because if I cut just one pole a few cms too short I’ll have to fork out to hire a van just to collect a single replacement. I will now be completely paranoid every time I cut a pole.