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Spa hole


wildbird

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I was wondering if any one knows if it is acceptable to drill two 3/8 inch holes from within the spa box behind the seat, either through the bottom into the hell hole or directly through the fire wall. I plan to mount some censors for the engine monitor in this area. I need to make 2 maybe 3 small hole to run the wiring back to the engine. My gut tells me it would not be a good idea to drill the spa but the plans depict only one ply of bid inside the box and two plies outside the box in this area. The other option is to run the wires out of the access hole and around and through the access hole into the hell hole. But it will require much more work to make this option neat and well done.

 

Wildbird N227EZ

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You planning on installing a hot tub? :D

 

Since you are talking about the spar (I hope) drilling a hole thru the spar box is almost always a bad idea. I'm sure there are many who would disagree and there are numerous exceptions. I've seen quite a few things mounted to the spar box backside in the engine compartment. Brackets and things for accesories that wouldn't fit anywhere else.

DO NOT under any circumstances drill UP or DOWN thru the spar box. You could hit the spar cap and damage the structural integrity of the spar box. There might be exceptions again, BUT, I've never seen anything that needs this kind of installation.

Go around the spar box if you're not 100 percent certain you won't damage the structural integrity. The spar box next to the fire wall structure is kind of critical.

I'm mounted my electronic engine ignition in the hell hole as well as my terminal busses for the engine instruments. All my wires go thru the firewall under the spar box where I don't worry about the structure. I also have the wires going out of the hell hole in the back seat into the spar box out to the wings. I don't like the looks of the wiring coming out of the hell hole out the back seat hole and into the spar box hole, but there it is.

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I was wondering if any one knows if it is acceptable to drill two 3/8 inch holes from within the spa box behind the seat, either through the bottom into the hell hole or directly through the fire wall. I plan to mount some censors for the engine monitor in this area. I need to make 2 maybe 3 small hole to run the wiring back to the engine. My gut tells me it would not be a good idea to drill the spa but the plans depict only one ply of bid inside the box and two plies outside the box in this area. The other option is to run the wires out of the access hole and around and through the access hole into the hell hole. But it will require much more work to make this option neat and well done.

 

Wildbird N227EZ

The forward side of spar is OK. The aft side of spar ( firewall side ) NO holes, this is the shear web

The top or bottom of spar from the fire wall to 3" forward NO, this is the spar caps

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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The forward side of spar is OK. The aft side of spar ( firewall side ) NO holes, this is the shear web

The top or bottom of spar from the fire wall to 3" forward NO, this is the spar caps

I think I will go with my original Idea and make a conduit of some sort and come out of the spar box and down into the hell hole and out the fire wall that way. The previous owner mounted the strobe pack in side and down the right side of the spar box about a foot and half down the right side. It is mounted with 4 #10 screws that penetrate the back of the spar and screw into nut plates that are riveted to the strobe pack. They are accessible from within the cowl. That would not have been my choice, and was also a concern. But with that said the the installation was done neatly and the plane has more that 400 hours of flight time and everything look perfect.

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1st - DO NOT drill ANY holes into the Spar Caps. If you accidently drill into the spar caps, the CenterSpar is now trashed, there is no repair for this.

 

For Wiring that needs to go from the Hell Hole into the Engine compartment. Drill the penetration hole(s) just below the centerspar. Do this from the Hell hole side, If you do it from the Engine side, you could accidently drill into the spar caps.

 

 

For wiring that needs to go from the Hellhole into the CenterSpar (i.e. strobes, navlights) Drill a small hole (1/2 inch) in the bottom forward portion of the Centerspar (just behind the front lip cutout ONLY), DO NOT DRILL through the top or bottom of the centerspar in the area of the engine extrusion hardpoints. If you look carefully at the photo I've enclosed, you can see black/white twisted wires coming up through the holes on the left and right side of the centerspar.

 

 

 

If you mount stuff to the center spar (Engine side), again, be very carefull that you don't drill into the spar caps. (i.e. autopilot servo).

 

Your Strobe power supply is OK where its at (mounted inside the centerspar)

 

NOTE - You can see in one of the photos where I mounted components inside the Centerspar ( Hydraulic valve) , where the bolts pass through the shear web and into into the Engine compartment. (This is the area that the Firewall has the lighting cutout, see next paragraph)

 

ALSO, if you mount stuff on the firewall where the mount bolt would go through the centerspar, again Be carefull where you drill. ALSO, Note that if the firewall is per plans, there is a big oval shaped cutout of the firewall (makes it lighter) where it covers the centerspar.

 

Waiter

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F16 performance on a Piper Cub budget

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