Cobra and fuel fill.

Buds Cobra strengthening.

rparigoris — Fri, 14 May 2010 00:35:06 +0000

Y10-05-13
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Bill,
I just saw your post on the list.
I am sorry, I thought this was now common knowledge, and I apologize to everyone on
the list. Sometimes I get tunnel vision on the way I advise my customers to build
this area and don't pass it on. This method has been used successfully for quite a
few years now and has been wrinkle free. If it ain't broke, I'm not fixing it.

Problem:
As the fuel vapors evaporate and vents out, it causes cooling in the PTFE fueling
nozzle, the fuel filler tube shrinks and shrinks the fuselage skin along with it.
Epoxy sticks to PTFE extremely well so any movement of the tube is translated
directly to whatever it is attached to, namely the skin. The manual does not imply
that the fuel filler tube should be separated a bit from the fuselage side and only
held by the tapes, and not a floxed corner at the juncture of the filler tube to the
fuselage (after all, we have gotten used to floxed corners). A little slop in the
two glass straps, applied as described in the manual (too briefly), would limit the
distortion. Many of us do not like to have a slightly floating fuel filler neck and
this is the cure used by many of us.

Correction:
If you desire to fix your fuel nozzle, cap, and the filler tube solidly to the
fuselage, the fuselage side must be reinforced. Put a 3/16 to 1/4 inch layer of
blue foam with two layers of bid glass over the foam (similar to the forward wing
support) to stabilize the fuel filler contact area to provide for support and
prevent expansion/contraction skin deformations. The thickness of the foam will
form a more rigid skin that extra glass alone may not correct as the skin is only
1/8 inch thick. Attach the nozzle with straps as described. One at the top, one
near the bottom.

Procedure I use at Custom Flight:

1. Open the hole in the fuselage top to allow the boss from the filler tube to pass
through.
2. Align the fuel filler tube to the fuselage side and temporarily set it against
the side of the aircraft, mark where the fuel tube will set and check that the
rubber fuel hose will fit and not be folded or bent.
3. Cut a piece of scrap blue foam about 1/4 inch thick, and wider than the fuel
tube by about an inch. Set the length from 1 inch minimum below the fuel filler top
hole, and stop near the bottom of the flat part of the PTFE filler tube.
4. Affix the blue foam to the fuselage side with 5 minute floxed epoxy on the top
and bottom edge and floxed Aeropoxy for the center. Clamp as necessary. Allow to
cure.
5. When secure, chamfer the sides to a 45 and round the edges. Spread entirely
with micro slurry and two layers of glass, and peel ply.
6. Refit the tube, mark the top for the filler cap flush with the outer fuselage
and cut and install the filler cap. Check fit. Once fit is acceptable, Redux the
top area around the filler cap inside and out, and affix with glass straps as
described in the manual. Peel ply as you will be working around here later.

7. Once all is secure, attach the trimmed rubber fuel elbow and clamp.
8. Use Pro Seal on just the top and bottom points of the rubber fuel elbow if you
are concerned about fuel leakage in the event of an overfill. Keep in mind, the
fuel tube will have to be cut off to remove it if using Pro Seal (available at A/C
Spruce.).

9. Attach fuel vent tubing as appropriate.

Bud Yerly
Custom Flight Creations
US Dealer.

----- Original Message -----
From: William McClellan
To: enquiries@europa-aircraft.co.uk
Cc: Bud
Sent: Thursday, May 13, 2010 12:01 PM
Subject: Fuselage skin distortion at fuel fill

I find only inconclusive information on the forum about fuselage skin distortion
that can develop around the fuel fill tube. I can not find additional
information. Would you steer me to the correct solution or give me any revised
procedure.
Thanks,
Bill McClellan

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Graham Singleton:
Bud
I see you used plastic tube for the breather. Makes me nervous remembering Harald
Linke's refueling fire. I always use 3/8 versatube and ground it.
Fuel vapour and droplets running up an insulated tube might act like a Van der Graff
generator and cause a spark. My guess anyway.

Graham

Fuel inlet skin deformation.

rparigoris — Thu, 13 May 2010 21:14:27 +0000

Fuel inlet skin deformation. I forget whos plane this was, but think it was in AZ.
We are hoping Balsa/ BID and keeping fuel hose stress off filler will prevent both print through and this.

Europa-List message posted by: "Tim Ward"
Bill,
In the early days (1996)the manual stated that the plastic 'cobra' tube
should be fibre glassed with Bid directly onto the fuselage skin in two
places.
It was then found on early models that exposure to the sun on a hot day
would cause the cobra to expand and therefore deform the fuselage skin
inwards. This happened to me. I then found via the builders web, that other
people were reinforcing the inside fuse skin with BID layers and placing
blue foam between the cobra and fuselage skin to absorb that expansion. I
am not sure if that was a Europa Club Mod or Company Mod however
it does avoid that deformation. I had to take my cobra out, push the skin
back out with the help of hot water over the outside and my son pushing
from the inside on a moulded piece of wood! Then reinforce the inside
fuselage skin, blue foam between and replace the cobra with new Bid
brackets.
Why it happened to me? I left the aircraft out in the open on a very hot 33
degree C day without the reinforcement.

Does it now say not to affix it to the fuseskin? If not, then do they expect
it to support itself, or the cover to support it?

Interesting.

Hope this helps,

Tim
Y10-05-13

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