Flex hose conduit inserts

A few builders have made a mod to imbed a flex hose inside of the fuselage between the avionics bay (just forward of the instrument panel) to the leading edge of the strakes. The idea here is to be able to route cables from the avionics bay, directly though a conduit that runs from the leading edge of the strakes, along the leading edge of the wings and to the wing tips.

The advantage of doing this is that it gives you an isolated path to route wires that require very low noise in the signal. In other words, you don't want the cables that power your strobes and nav lights to be routed along side the cables carrying your accelerometer signals (assuming you go with an advanced glass cockpit avionics package as I plan to do).

In my opinion, the added work is well worth the result. So let's begin...

First, I picked up some flex hose from the hardware store. Nothing fancy here, just a 1/2" flex line found in your sprinkler system isle. Make sure the outside diameter will fit in the fuselage!! There are some flex hoses out there that say they are 0.5" OD, but are really 0.55" and will not fit!



I then had to measure where the leading edge of the strake will be; this information is located on page 21-2 in the plans. Once I had that drawn onto the fuselage side, I drew a circle representing the control stick recess (on the right fuselage side only) to make sure the flex hose would clear the recess. I then drew the path I wanted to carve out.



Close up...


I prepped my router with a flat bit and went to work...


As for the width of the channel, I wanted it to be tight enough to hold it in place, but not too tight to where it would squish the flex hose. If it's not tight, the flex hose will have a tendency to float to the top when micro is poured over it ::lessons learned from other builders!::


Notice how the flex hose will lead straight into the leading edge tip of the strake...


I then cut the flex hose to length and used sand paper to scuff it up... I wanted the mircro to bond properly to the surface of the flex hose. Here is a picture showing the before scuffing (top hose) and after scuffing (bottom hose)...

 

I then plugged the ends of the hose with a little bit of tape - I didn't want micro to get inside the hose. I then test fitted the flex hose into the channel. 



 I mixed up some micro and poured some into the channel...

 


I then inserted the flex hose into the channel...


 Pouring micro to fill the rest of the cavity...

 

 I then let cure overnight...

 

 The left side was much easier - since I didn't have the side stick recess to worry about getting in the way, it was just a straight shot.


Close up...



Post router work...






Test fit...


Scuffed the flex hose and closed off the ends...



Poured micro into the channel and inserted the flex tube into place..





Then poured micro over it to fill the cavity...




After a full cure, I sanded everything flush. Some filling will be required just before I glass the outside fuselage, but nothing to worry about!



I'll refrain from opening up the conduit ends for now (from the avionics bay or the leading edge strake). At least I now have the conduits in place and ready when I need them.