Twisted: Week 68 - Ducts...

Hours to date: 677.75

Yes, I'm still working on them...

It's well over 100 hours now on this mod.

I finally got the flanges to fit nicely to the oil cooler.

Then I put all the nut plates in place only to discover that I had gone overkill on nut plates. The ducts fit so well top and bottom now, that only the nut plates on the sides are really necessary.

I also bought some HiTemp RTV which I will use when finally installing everything to make sure the edges are air tight on the ducts.

I put the strip of door sealing foam all round and everything is feeling pretty snug now.

I moved onto fitting the cowl flap - which has a long arm on the inboard side which will connect to a forked rod end and then onto a control arm before finally connecting to a yet to be decided control in the cockpit!

Actually I have done quite a bit of thinking about this and am leaning towards the simplest solution for the control - which is a metal gate with a knob on the cockpit side which is screwed onto a threaded rod which goes through the cell to the outside and connects to the control arm via a rod end bearing (I think.)

The metal plate will just have a notch at either end which the knob and rod will slide into to lock it in place - either open or closed. I don't see the need to have any other settings at this stage but can easily put some more in should I need to in the future.

I think I may also need a spring in the system to provide some resistance when the flap is open - you would think it would be the other way round but I have read online about someone else who had a cowl flap and this is the way it works. Easy to open - hard to close.

Due to the arm on the cowl flap I had to make a slot in the outlet duct - to seal up this gap as best I could I used a piece of rubber and contact cemented it onto the outside of the duct. Then cut a thin slice in the middle with a sharp blade. This should seal up most of the gap. (see photo below).

Finally I moved onto laying up the flanges at the other ends of the ducts.

I think I've made a better job of them this time round - I could hardly do worse than last time!

I used the fuselage bottom itself as a guide for the outlet duct flange. First off taping the area with Duct tape so it will release when set.

The same principle applied with the inlet duct and I used the bottom of the air scoop as a guide for the lay up.

We'll have to wait till tomorrow night to see if I have done it right this time and hopefully everything releases okay.