Graeme,
That was a Flight Crafters mod for the trigear only. However the
Berube=99 conventional often had it also. The flange was done in
four layers. The cover was normally done in a four layer, however, that
is a structural member and in a front end impact the aircraft with this
mod will buckle right across the canopy bow area if the area is cut down
considerably like flat from the back to the panel face.
I have made this cutout myself on many aircraft but frown on cutting the
tunnel lower.
To add structure back, I made the center console cover and the flanges
out of a compressed 6 layer piece of high density 8oz. glass. The
cutout has to be reinforced with a flange of considerable strength to
maintain the beam strength of the top. The flange must be six plies in
my opinion and run down on to the inside of the tunnel at least 3-4
inches overlapping each two plies over each other to take the shear of
an impact. The cover plate is screwed in using #8 or 10 screws about 3
inches apart down the sides. That makes for a robust part but it is
considerably heavier than the original couple of plies and some 3 mm
foam.
Note each engineering test firm has slightly different criteria ( I use
USAF Wright Patterson Data mostly), but a .009 thick glass ply has very
little compressive strength capability. If you layer say, six
compressed layers (i.e. no voids), at 15,000 psi for a thin flat hand
laid plate you only have .050 inches of glass and over three inches, the
math says it will hold 750 pounds, but it has little compressive
rigidness and will buckle under load unless built like an angle iron.
So make it thicker right! Well a uniform thickness with a glass to epoxy
ratio of about even may get you 100,000 PSI in a perfect sample built to
nearly a 90 degree angle, which is quite strong (it is now a longeron),
but every hole and cut you put into that cover and flange will in fact
weaken it. Fiberglass peels in bending shear so pay attention to your
molding. I=99ve seen some ugly voids which basically makes the
structure suspect...
I feel comfortable with a full ring of six plies well lapped onto the
tunnel wall all the way around and screws every three inches or so. The
cover plate should be at least 6 plies but it has to be esthetically
about the same as the piece you took out so it gets a bit thick. If you
compress the piece you took out to bending failure and you test your
filler piece and it is stronger, you did your job. I rely on the
flanges being considerably stronger than the original C section and
assume the plate is only a shear load. One must not forget to tie the
original glass to the new glass by hollowing out the edge and filling
with flox and assure there are no voids. Once complete, you can lift
the plane with the panel cutout. It is very rigid, and analytically
should take the force of a modest impact better than original.
I also recommend that Trigear owners and those conventional conversions
consider a beam be added from wall to wall to make the seat areas
connect with one another if cutting out the tunnel. That makes a
brutally strong beam across the cockpit. Not really essential to the
Trigear but worth considering on the conventional conversion. After
all, one does not care to have his =99arse be the first item on
the scene of the gear collapse.
Does my reinforcing work. A nameless client on a cross country impacted
the runway some 25 degrees nose low and porpoised some 4 times before
ramming the nose into the tarmac at a 30 degree angle and pushed the
nose gear leg into the center tunnel. The fuselage was completely
intact but all three gear were pretzels. Airport observers (mechanics
watching the approach and bounces) were astounded the aircraft was in
such good shape. No main structure was damaged. Yes the gear,were
changed out and the engine frame and nose gear, but more damage to the
plane was done grinding off paint and inspecting it than was done by the
=9Ccrash=9D. This is one tough little airplane. If you
want to stiffen the nose a bit more, lay a 2mm or 1/8 inch foam and
glass over with two layers to the area between the seat and the footwell
step. That is the common impact failure area due to buckling
I=99ve seen which puts more stress on the center tunnel.
Nigel is correct. Unless you can prove your mod is as strong as the
original structure, don=99t fool with it. Put an access panel in
the belly for the center tunnel and leave it alone. If you do cut it
out, do your homework. I did and I feel confident in my construction
and am pleased with its performance. I am as a builder my own inspector
in the US, and frankly the FAA rep just rolled his eyes and said you
damn engineers, it feels really strong to me so here is your
airworthiness certificate. Heck of a thing we put up with. 419 PL was
originally built in 2004, still going strong. 12AY has bottom access
only because it was faster lighter and easier to do.
Why avoid this mod, well it is a pain to sit in the seat and undo a
zillion screws to get to an item in the tunnel, then drop something and
try to bend over to feel around for it. The underbelly pan is a bit
more relaxing on a flat floor with a nice creeper to lay on. However it
is really dark in there and since gravity works 24/7 wear safety glasses
as every nut and bolt hits you in the face. It makes for great stomach
muscles as you continually cycle from the belly to the cockpit
unscrewing things. I have a love hate relationship with everything in
an airplane so keep it light and simple.
Note that the Europa Trigear mod which cuts out 1/3 of the side of the
tunnel has less glass than what I do and that was approved. There was
also an approved foam and glass modification to cut down a tunnel
approved but it did not have a large removable panel.
On the original mono I was always amazed how thin the glass was on the
center tunnel and as seen in crash photo=99s the tunnel will fail
on a mono. Of course it fails on a very severe impact only. One cannot
build to an impact resistant aircraft as it would never get off the
ground would it.
That=99s my two cents of boring info.
Best Regards,
Bud Yerly
Custom Flight Creations, Inc.
US Europa Dealer
Best Regards,
Bud Yerly
Custom Flight Creations.
From: Graeme Hart
Sent: Thursday, July 07, 2016 7:16 PM
Subject: Re: Fwd: Europa-List: Do you recognise this cockpit mod
Thanks Nigel
While that is bad news it is also good news in that I'm only starting
the build so it shouldn't be too hard to fix compared with attempting to
fix when ready to fly.
I am in New Zealand and with our smaller population it is a little
harder to find people with the experience your inspectors have. We also
have a much simpler inspection regime.
I'll contact the Europa factory and get their advice on how to reinstate
the structure. Hopefully it will just be a matter of reinstating the
missing structure with a flat panel with an appropriate number of plys
and a suitable overlap/bonding to the edges.
On Fri, Jul 8, 2016 at 10:48 AM, nigel_graham@m-tecque.co.uk
<nigel_graham@m-tecque.co.uk> wrote:
Hi Graeme,
I don't like to be the bearer of bad news but that mod was not (and
never will be) approved in the UK. The centre tunnel is a critical
structural component and by removing such a huge area of the box
section, most of the strength will have been removed with it. If it is
your intention to build the airframe to flying condition, I would
suggest involving your inspector (one with proven composite skills) to
advise on reconstructing the tunnel.
The Europa has no longeron like structures forward of the seat
moulding and it is only the tunnel that prevents the fuselage snapping
off in the event of a high "G" arrival. Typically, the fracture
initiates at the sharp corner at the lower edge of the windscreen,
propagates down the fuselage sides and across the floor. I have attached
a picture of such a failure to help concentrate the mind (I have more!).
Nigel
On 07/07/2016 21:51, Graeme Hart wrote:
Hi Alan
It is a trigear and came as a trigear from the factory.
It looks to me like the plan was to put a removable panel on the
top.
I have attached a better picture.
On 7/07/2016 11:14 pm, "Alan Burrill" <alanb@dpy01.co.uk> wrote:
<alanb@dpy01.co.uk>
Tri-Gear or Monowheel?
Alan
GOBJT
> On 7 Jul 2016, at 11:35, Graeme Hart
<graeme.hart@onecoolkat.com> wrote:
>
> Hi All
>
> I have a kit that started out around 1999 and has been worked on
by a number of builder since them.
>
> Does anyone recognise the mod that has been done to the cockpit.
A lot of the top of the centre console has been cut out and reinforced
around the edges.
>
> I'm hoping that this is a recognised mod and someone can point
me at documentation on what was intended.
>
> A picture of part of the cutout section is below (sorry I don't
have one of the entire cutout)
>
> I'd appreciate any leads on how this mod is intended to work.
Also, with this large hole in the top do you still need the fuel valve
access panel?
>
>
> Thanks
> Graeme
> <20160705_174300.jpg>
|