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John,
I could not view your YouTube video; it asked for a
log in...
Door strut damage is becoming a common item as the
fleet ages. We are seeing problems on probably a 3rd of the planes that we
service. There have also been at least a couple of cracked windows possibly
attributed to the door strut stress placed on the door.
Assuming your ball and socket alignment isn't so
bad that the range or motion is exceeded, the other common issue is the stud
wallowing out the hole through the carbon frame. Once it begins to move around,
the threads will quickly open up the hole diameter, and as the assembly becomes
loose, the socket will either pop off, or damage the fingers in the
socket.
There's more than one kind of ball and socket
floating around out there, also. Some don't have the same amount of motion as
others, so if your replacement strut did not come from Lancair, make sure that
the similar ends will actually allow the needed rotation.
Adding a strap to the door to allow you to cushion
the opening is a good idea also. I still see folks that land, unlatch the door
and just push it up and allow it to open on it's own (and you know who you
are!!!). I can just about guarantee you that the ball studs will be loose in
their composite mounts.
Brad Simmons Airframes Inc. 39 Airport Rd. Milan, TN
38358 731-686-3610 731-686-3613 fax www.airframesinc.com
----- Original Message -----
Sent: Tuesday, October 08, 2013 6:55
AM
Subject: [LML] Cabin door strut on IV
series
Hi all,
I have to say that my first
attendance to a LOBO fly in was awesome ( to use my children's and their
children's cliche). The chance to meet so many enthusiastic,
knowledgeable and fun Lancair folks provided WAY more benefit than I ever
would have imagined. Thank you to the board, the vendors, presenters and
to everyone involved. I loved it and so did my wife, Anne.
I saw some folks examining a IVP
door strut on Saturday I think. The attachment at the frame was very
loose so that the ball stud was flopping around. Close inspection showed
that the door frame was cracked under the stud. I'm not sure whose plane
this was but I think it is the one that vibration measurement equipment had
recently been attached to for studies.
The door strut triggered memories
of similar occurrence with my strut a couple of years ago prior to first
flight. I would guess the smart folks who noticed this also figured out
the reason for the failure, but just in case I will share what I found and how
I dealt with it.
The problem with the door
strut is that the arc described by the strut during opening and closing
exceeds the range of motion built into the ball stud socket on the lower end
of the strut. Therefore the door frame is wrenched back and forth during
door operation when the stud is attached to the door frame without
modification to the frame. There is a plane you can find by
experimentation or by mathematical exercise if you are so gifted and inclined
to pursue (I am not) that will allow the socket to move within the design
limits and therefore not stress the stud and the door frame. Once this
plane is determined, you can use a small washer of wood, foam or other
material to shape the door frame where the stud penetrates the frame.
You'll need to cut out a bit of the frame to accomplish this.
since my frame was broken here it made that part simple. Super
glue or hot glue can hold the form in place. Then lay up two BID of
carbon fibre cloth over the form and remove the form material when done.
Lay up several layers on the back side to strengthen the mod and to
secure it by sandwiching on both sides of remaining frame.
It
gets a little more complicated because the back side in my case was in very
tight quarters. When complete I found that the screw stud on the ball stud
part was too short. I was able to go online and find a replacement at
very nominal cost and that had plenty of thread length for the
purpose.
I have uploaded a video to
YouTube of the way the attachment looks now. See link below. I
hope it helps someone.
John Barrett
N31VP
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