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Static Line Through Tunnel

grjtucson

grjtucson

Well Known Member
I've searched and come up with very little. I am planning to route my static line down into my conduit in the tail section and on through the center tunnel with other wiring.

I just don't particularly like drilling bulkhead and installing clamps under the longeron. I've got the room, there seems to be no greater risk of moisture being a problem, and it would be neater as far as I can see.

Anyone have anything I should consider before committing to this?

Merry Christmas!

George
 
Hi George,
Your airplane may vary, but you may have trouble fitting everything through the provided bushing holes on the bottom of the bulkheads if you add the static line, especially at the aft baggage bulkhead. *Unless* you are doing one or more of: manual pitch trim, no lights in the tail, no ELT back there, no remote compass, etc.

If you're going to be drilling holes for an extra bushing, under the longeron is pretty convenient. You can probably get by with a single stick-on or epoxy-on zip-tie mount between each bulkhead, so no fussing with adel clamps. Or you can fashion little hangars out of .032 sheet that rivet onto the longeron via the existing skin rivets.

I would not feel pressured to decide right now. You're going to be crawling around back there to rivet the skins anyway -- this sort of stuff can be finalized at that point if you're having trouble deciding.

Paul
 
Longeron

Hi George,
We routed the static line under the upper longeron and hold it in place with a globs of silicone about every 15 inches. A piece of masking or duct tape will hold it 'til the silicone dries.

If you route it along the left side of the airplane it'll come out right at the airspeed and altimeter. If you go through the tunnel, you either have to turn left or go all the way to the firewall, then up and back.

We elected not to put in the center console that runs from the center of the instrument panel down to the fuel selector because it really makes it much more difficult for long legged folks to get their legs in and on solo trips you can slide your legs waaaay apart for a stretch. That precluded us from running it up the center.

Regards,
 
pierre smith said:
If you go through the tunnel, you either have to turn left or go all the way to the firewall, then up and back.
Click to expand...
Which...in a -7[A] runs it right by the heat manifold. Plastic tubing...heat manifold...hm....
 
Longeron route...

grjtucson said:
I've searched and come up with very little. I am planning to route my static line down into my conduit in the tail section and on through the center tunnel with other wiring.

.......

Anyone have anything I should consider before committing to this?

Merry Christmas!

George
Click to expand...

George.... the advantage of the under the top longeron route is that the static ports will become the lowest point in the system.... especially with your taildragger.

This makes the system somewhat self-draining for moisture (when you are not in Tucson.... :) ...)

gil in Tucson
 
One of the more difficult tasks is getting everything from the panel to aft of the center section/spar in a side-by-side. Options are very limited. Consider all the plumbing, cable, coax, wires and how you're going to route them before running the static down the tunnel. You might find it best left for wires and cable going to the wing and tail.

Snip up pieces of appropriate gauge wire and cable and try cramming them, as a bundle, into bushings, through tight radii, and around obstacles you will encounter enroute. Just making up the wire list is illuminating.

John Siebold
 
In my 7A, no possible way to route through tunnel. Mine is full with strobe power wire, 2 wing strobe feeds, trim wires and tail light wires. As it is, I'm routing my TT A/P pitch wires and GRT magnetometer wires under right side longeron similar to the static line on the left.

You either need to set in a new conduit under the baggage and seat floors (wish I had before riveting them in) or modify the right opening in the tunnel to pass through the aft baggage bulkhead.

Now, if you are not using strobes or a pitch servo, you will have room.

Jekyll
 
Thanks!

Great input all, thank you.

It seems that there is little problem in sticking it under the longeron, so no downside there, and the upside is more room in the center, so side it is :) The thought of having the other side available is nice as well.

I just found 100 of the zip tie bases for $9.50 in the electrical section of Home Depot. I'll probably scrape off the sticky pad and use Shoe Goo. Seemed like a deal.

I am putting a few extra conduit runs under the seats and baggage floors "just in case". They'll run both laterally and longitudinally.

I'll also be sure to insulate the pitot and LRI tubing as it comes up near the heater manifold - hadn't thought about that. Isn't there a fuel line there too? Is there an easy way to route them along the sides of the forward fuselage? (haven't gotten there yet)

My preliminary thinking is:

Fuselage
- strobe, position light, and pitch trim servo in the tail
- autopilot pitch servo at the bellcrank
- probably a magnetometer above the bellcrank (GRT/Dynon/AFS/?)
- elt in the baggage compartment
- flap motor at the rear spar carry-through
- ptt swich on each stick
- comm. antenna under the left seat
- seat heaters for each seat
- transponder antenna just aft of firewall

Left Wing
- strobe and position light at tip
- marker beacon antenna at tip
- taxi light nearly at tip
- pitot at bellcrank
- fuel quantity at root
- fuel vent entirely in root

Right Wing
- strobe and position light at tip
- VOR/LOC/GS antenna at tip
- taxi light nearly at tip
- autopilot roll servo at the bellcrank
- LRI (two smaller tubes) at 1st insp. cover
- OAT wire at 1st insp. cover
- fuel quantity at root
- fuel vent entirely in root

I'm leaning pretty heavily towards the Thor strobe and light system which is very lightweight and puts the power supplies out by the strobes themselves. This current plan doesn't include any cockpit, map, or panel lighting yet either.

I'm trying to keep all wiring and plumbing to a minimum, and also working towards an ambidextrous cockpit. Thus I am planning to use panel switches only for trim, flaps, and autopilot, and to put the headset jacks on or near the panel at each side. I have no problem using my throttle hand to control things, and I actually like an uncluttered stick.

Opinions and experience, of course, are welcome.

George
 
George, looks like you've done your planning. Thanks for listing your runs, it reminded me of one I hadn't yet put in - OAT, thanks.

I'll offer something to consider, try placing your MB antenna in front of the spar or under the floor right behind the spar. The wing tip requires a long run of heavy coax. I considered glassing a foil to the inside of the cowling but went with a MB boat antenna which I plan to install in front of the spar. I may put it under the seats if I have room for the coax through the spar. Just a thought to save a pound or 2.

Jekyll
 
Marker Beacon

Jekyll,

Glad to help, I sometimes feel guilty that I ask more than I answer 'round here, so I'm trying to compensate by posting some of my more developed trains of thought. As Ironflight discussed recently, sometimes it's just good to summarize and clarify if for no other reason than to enhance the archive.

As to Marker Beacon, I'd love to ditch that coax run through the left wing and move the VOR run to that side. I assumed the stripped wire type would be best in a fiberglass wingtip, and didn't even think about externals until now. Your post got me started on research so I'll now look into a "boat" or a flush mount (I like those) or ditching the marker beacon all together and using an IFR GPS.

This is why I start asking questions early :D

Thanks much,

George
 
Use a smaller cable

Jekyll said:
George, looks like you've done your planning. Thanks for listing your runs, it reminded me of one I hadn't yet put in - OAT, thanks.

I'll offer something to consider, try placing your MB antenna in front of the spar or under the floor right behind the spar. The wing tip requires a long run of heavy coax. I considered glassing a foil to the inside of the cowling but went with a MB boat antenna which I plan to install in front of the spar. I may put it under the seats if I have room for the coax through the spar. Just a thought to save a pound or 2.

Jekyll
Click to expand...

George and Jekyll,

The Marker Beacon antenna cable does not need to be the heavy stuff for the 75 MHz signals it is receiving.

You can use some small much diameter stuff such as this Belden RG-174/U

http://www.skycraftsurplus.com/index.asp?PageAction=VIEWPROD&ProdID=1157

The specifications for the cable are here in the Mouser catalog, but you will notice their price being almost 9 times higher!

http://www.mouser.com/catalog/628/861.pdf

This cable is only 0.101" diameter, and the /U variation has a stranded center conductor, making it more flexible.

I say keep it in the wing tip, but use a much smaller cable to keep the bundle size down. In this case, an external antenna is not needed at the 75 MHz...

gil in Tucson
 
Static line, wire planning

George...

In planning wire, static & pitot runs I would advise you to use my "Plenty Rule" which says plan on what you need early and then double the requirement. I built an RV6 fuselage just before the currant glass technology and I put two 1/2" PVC condiuts (PVC water pipe from Home Depot) under the floor, as well as two in each wing, drilled about 1/2" holes from front to rear under the longerons each side and I felt I had plenty. Upon completing the wiring I was starting to run out of wire space under the longerons and only had a couple wires through the underfloor conduits. Then TruTrak came along with a servo in the back which filled one floor conduit leaving one remaining. My aircraft now has a good IFR steam gauge panel with 2 axis autopilot and I am happy with it considering when I built it. But the new glass cockpit would add still more "stuff" to wire meaning an AHARs unit, a magnometer, more antennae etc. The Later RV kits have a different spar center section which would be easier to work with but the point is there is not as much room as it first appears. Use the "plenty Rule" early on. Drilling a reasonable, properly deburred hole through the web of a bulkhead does not reduce the strength of the bulkhead provided the flange is intact. Neither does a 3/16" adel clamp mounting screw hole harm the longeron if it is in the center portion of the angle. We earlier builders who had no prepunched anything drilled hundreds of them as none of that was spec'd.

Dick DeCramer
N500DD RV6
175 Hours
RV 8 Tail Kit complete
Northfield, MN
 
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