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An Eccentric Anomaly: Ed Davies's Blog

There's been some nice weather and some not-so-nice weather. The bad weather hasn't been terrible - just finely judged to slow things down with the minimum amount of effort with days of drizzly showers and winds just high enough to make lifting purlins be not really sensible.

Mostly I've been making slow but steady progress in getting the frame up and thinking ahead to the next phase: the main structure of the floor. The timber for that's been ordered and I'm just sorting out a list of fasteners needed.

In the mean time, half the purlins are up, for the main bedroom, study, living room and kitchen, with the ones for the bathroom, guest bedroom, and the two greenhouse bays to go. The connection between the guest bedroom purlin on the south side and the adjacent one in the greenhouse will be interesting as the purlin is staggered at that point. Other than that I hope it should all be fairly straightforward.

The six replacement posts for the ones I'd messed up in various odd ways arrived. Depressingly, the first one I slotted and drilled didn't fit well so I set that aside. The remainder went fine, needing only a bit of sanding to match up with the brackets.

The problem with the first was that the holes were a bit skew relative to each other - I think the drill must have been sitting at a slight angle for one of them for some reason. With these I didn't need the other end as a “stub” post so I'd left it long to give myself a second chance (and, in theory, a third chance - see below).

Anyway, today I chopped the end off that post and slotted and drilled it taking even more care than normal. Pleasingly it looked very accurate (e.g., measuring the positions of the far sides of the holes) so I took it to the bracket with some confidence. The only irritation was that I made the mistake of trimming it to length so that the top hole was half on a knot but that was solid and drilled cleanly so not a problem.

Of course, it didn't fit at all. All my experience with the first 35 of these 36 brackets has been that the holes are drilled (punched?) accurately - all problems have been mine or the positions of the flange plates on the brackets which are not so consistently welded. Accordingly, it took me a while to work out the problem.

For context: square clamped to bracket:

Look at the distance between the bottom edges of the holes:

A full 105 mm, when the centres should be 100 mm and have been so on all the other brackets.

The nominal height of these posts is 3066 mm whereas the supplied timber is 3600. The height of the tongue which goes up into the bracket is 200 mm. I've been cutting 205 mm slots to allow for sanding to match the actual positions of the flange plates and so the top of the slot doesn't bear on the tongue which might start a split going up the grain of the wood.

(3600-3066)/205 = 2.6 (and a bit) so, in principle, I could have given myself three attempts at getting this post right. Actually, by the time I'd squared off the end for the first attempt there wasn't that much margin left. I could have left room for a third attempt but chose to skip that to get rid of a little ding probably provided by a forklift at some point in the timber's life.

So now I'm left with the last post not long enough to just chop the end off and start again with the measured positions of the holes in this last bracket:

As you can see the required length (3066 mm) comes in the top hole (the one with the knot).

What I'm thinking is that I can chop the bottom off, reuse the existing “top” hole as a bottom hole, extend the slot and drill a new top hole - matching this odd bracket's hole positions. That'll still give me a bit of length to play with at the top end to get the purlins level.

Worth a try rather than buying a new post (£50 or so) and waiting a week or two for it to come. But not worth trying this evening at 17:30 when I was feeling tired and irritable.