Engine Mount (3h 30)

The rigging of the wings has stalled (yes, sometimes they write themselves) while I hope to get loan of some wing stands which will greatly help the process. It is certainly possible to do them without but it would be easier to have them. I did experiment with the positioning though. By running a string across both wings down the spar rivet line you can see if they are straight or not.

As you can see, initially they were quite a ways off, but since then I got them dead on. I then raised the wings up higher on the ladders using some blocks to get the height accurate.

In this picture the height of the string above the first rib is 87mm (on both wings) and we are aiming for 85 plus or minus 5. So the wings are pretty set! Well, except that I looked at the string again and I had moved them out of alignment. If I don’t get the wing stands I need an extra ladder, standing on plastic chairs isn’t working.

So in the meantime I thought it would be good to get one of the larger pieces off the hangar floor: the engine mount. First job is to grind down a lot of the brackets so that they fit on to the firewall. I was happy that Allen was able to join me as I really don’t like the grinder. Much grinding later we had something that fit and we could jiggle it around in place until we finally got something that would work.

The holes have to be drilled from the back but there’s really no easy way to keep the mount in place so we used a pencil to mark the position of the holes on the mount and took it away to drill pilot holes. The engine mount brackets inside the firewall were bolted in place, though not without some effort. First I had used some of the wrong size bolts (too short or too long) so they had to come out, and then a couple of the bolt heads were too close to the bracket to get a wrench on. Allen showed me a neat trick where you use a screwdriver up against the head to provide the resistance needed. It is a common complaint on the Zenith website but I really don’t know why they didn’t make the lower mount brackets bigger.

With the brackets in place we were able to cleco the engine mount in place and check angles and levels – looked pretty good. The view from the front is disconcerting because the engine sits off centre so every time we looked at it we thought we had maybe got it wrong. The plans soothed our worries.

We then spent some time trying to decide how best to drill the holes and it was decided to drill them all without the parts attached, so first I drilled all the holes in the engine mount, one drill bit size at a time. The main holes on the mount take an AN6 bolt (3/8 inch) but there are also some 1/4 inch holes and some 3/16 inch ones. I then drilled through the mount brackets it was time to bolt the two together and they went together just great.


Time had run out (the Super Bowl was about to start!) so we just hand tightened the bolts. Also, for the last hole my drill battery decided it was worn out so I couldn’t finish the last two holes (yes, four years into this project and I still have not bought a spare).

But the engine mount is pretty much on – still quite a bit to do before the engine can come out but it is one step closer.

Hmmm reading this article I realise I didn’t put any primer on the firewall under the engine mount brackets, I should probably do that before tightening the bolts.

Next up – finish bolting on the mount, and then get the wing struts cut and installed so the wings can stand without needing the ladder. I realised this week that if we have an earthquake we run the risk of the wings falling off the ladder and then who knows what damage. That said, if we have an earthquake the shaking might shake loose all my crappy rivets and the whole thing fall apart! 🙂