Inspecting rings...

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gicummo

Member
Joined
Nov 19, 2009
Messages
20
Location
montevideo / uruguay
Hello,

Soon I am going to cover my first wing of a Pietenpol, everything ok, but I want to know something that I can't see anywhere, the inspections rings, where they go?.. inside the wing, outside or in both sides of the fabric? I am talking about the plastic circle.....

Just this, thank you for any answer in advance.
 

bmcj

Well-Known Member
Joined
Apr 10, 2007
Messages
14,007
Location
Fresno, California
The rings are usually placed on the outside of the fabric and then covered (reinforced) with a fabric panel or tape overlay. They can be placed on the inside, but that is a lot more difficult to do. For your plane, you only want them on the bottom surface of the wing since inspection covers on the top of the wing may come off in flight and cause major airflow and handling problems. If that happens on the bottom surface, the effects are minimal (plus, there is more negative pressure on top trying to pull the covers off).

You want rings anywhere you might need to inspect or service periodically (like control bellcranks or wing/strut attachments), but do not need to cut the opening until such time that you need to actually get in there. But go ahead and buy your cover plates because it's easier to paint them when you first paint the plane, then just put them away until needed.

Here's section 2-14 of FAA AC43.13-1B which talks about inspection rings. I've included the part about drain grommets too, since you will probably be doing those at the same time.

2-14. INSPECTION RINGS AND DRAIN
GROMMETS.

a. Inspection Rings. Inspection access is
provided adjacent to or over every control
bellcrank, drag-wire junction, cable guide,
pulley, wing fitting, or any other component
throughout the aircraft which will be inspected
or serviced annually. They are installed only
9/27/01 AC 43.13-1B CHG 1
Par 2-14 Page 2-23 (and 2-24)
on the bottom side of the wings except where
installed on the top surface by the original
manufacturer.

(1) Cutting the holes may be delayed
until needed; however, all covers should be
finished in matching colors with any trim lines
and stored until needed. Spraying matching
colors a year later is expensive and time consuming.

(2) The 3-9/16 inch inside diameter
cellulose acetate butyrate (CAB) plastic inspection
access rings have become popular and
bond satisfactorily with Nitrate Dope or Fabric
Cement. Any metal inspection hole reinforcements
of a particular shape or special design
or size, installed by the original manufacturer,
should be reinstalled after cleaning.

(3) Tapes or patches over aluminum
reinforcements are optional, but recommended
in the prop-wash areas on the wings and forward
fuselage bottom.

(4) Fabric patches over plastic rings are
strongly recommended because plastic is not a
stable material, becomes brittle at low temperatures,
and fatigues and cracks from prop
blast vibration. Plastic rings are often cracked
during removal and installation of spring, clipheld
covers. Patches with a minimum 1-inch
overlap, should be installed with dope.

b. Drain Grommets. Atmospheric temperature
changes cause the humidity in the air
to condense on the inside of aircraft surfaces
and pool in all low areas. Rainwater enters
through openings in the sides and top, and
when flying, everywhere throughout the
structure. Taxiing on wet runways also
splashes water up through any bottom holes.
Therefore, provisions must be made to drain
water from the lowest point in each fabric
panel or plywood component throughout the
airframe while in a stored attitude. Drain holes
also provide needed ventilation.

(1) Install drain grommets on the under
side of all components, at the lowest point in
each fabric panel, when the aircraft is in stored
attitude. Seaplane grommets, which feature a
protruding lip to prevent water splashes
through the drain hole, are recommended over
drain holes subject to water splashing on land
planes as well as seaplanes. The appropriatesize
holes must be cut through the fabric before
installing seaplane grommets. Plastic
drain grommets may be doped directly to the
fabric surface or mounted on fabric patches
then doped to the covering. Installing a small
fabric patch over flat grommets to ensure security
is optional. Alternate brass grommets are
mounted on fabric patches, then doped to the
fabric.

(2) After all coating applications and
sanding are completed, open all holes through
flat drain grommets by cutting through the fabric
with a small-blade knife. Do not attempt to
open drain holes by punching with a sharp object
because the drain hole will not remain
open.
 

Joe Fisher

Well-Known Member
Joined
Feb 10, 2007
Messages
1,379
Location
Galesburg, KS South east Kansas
It could be of interest to you I use the Ceconite and dope system it is much better than Poly Fiber. The rings are made out of butyrate so it is better to attach them with butyrate dope. The rings partly desolve into the fabric and they never come loose like they do with Poly Fiber. I use 2.6 oz Ceconite to cover then the inspection rings patches I use the 1.7 oz fabric it blends in better than the 2.6 fabric. I use the bottom of a one gallon can for a pattern to cut out the patches.
 

gicummo

Member
Joined
Nov 19, 2009
Messages
20
Location
montevideo / uruguay
Thank you all for the answers, I ask that because I was watching a video about this topic and it start marking the rings in the inside of the wing; then he put them outside, so he make me doubt.

than you and regards
 

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
6,603
It could be of interest to you I use the Ceconite and dope system it is much better than Poly Fiber. The rings are made out of butyrate so it is better to attach them with butyrate dope. The rings partly desolve into the fabric and they never come loose like they do with Poly Fiber. I use 2.6 oz Ceconite to cover then the inspection rings patches I use the 1.7 oz fabric it blends in better than the 2.6 fabric. I use the bottom of a one gallon can for a pattern to cut out the patches.
Never had any rings come loose with poly fiber. They're glued on with poly-tak and stay stuck good.
 
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