May I add a note here?
A tubular steel firewall pass-through filled with an intumescent sealant is very fire resistant. The sealant will also do a pretty good job of locking the components (wires, cables, etc) in relation to each other. However, that fixation is not perfect, as the sealant is elastic. It's also easy to have voids inside the tube, since flow during sealant injection is entirely random.
I've seen a few -14's with power wires, control/instrument wires, and engine push-pull cables all run through the same tube. Must be on the plans that way. This one is typical.
I think it's a bad idea.
First, the fundamental objection; Bowden cables can act like a saw. I've seen 'em cut completely through an Adel clamp. It doesn't take a lot of mis-rigging to have that Bowden pull a little with each startup, for example.
Second, note the approach angle on the big wire. It is hard against the edge of the tube at 1:00 o'clock. It will wear through the insulation there even if the tube is full of sealant.
Third, think about maintenance, or wiring changes in the future. The big control push-pull will wear out eventually. It will need to be removed through the tube, and a new push-pull inserted. If you install the push-pull with its end fittings, then install wires, will you have enough clearance to get it back out without first removing the wires?
Last, clearance issues aside, the sealant plug will need to be cut away from the interior surface of the tube in order to remove wires or cables. To do it requires using a shop-made semicircular "knife" pushed into the tube in two or three places. Here there is no clearance for the approach of the knife. The cables need to come straight out of the fitting for at least an inch or two.
I realize locating firewall passages is a challenge for some builders, so I'm not going to tell you where to put them. If you want to stick with the location(s) on the plans, that's great. However, I strongly recommend that you install separate
pass-throughs for control cables and wires. It need not be complicated. Using the above as an example, just put two of them side by side
. I'm sure Vans will cheerfully sell you a few more, and they're easy to weld up locally. If you wish, weld multiple tubes on the same baseplate to save real estate.