REFLECTOR: Door strut review

Tue Oct 6 21:27:24 CDT 2009

My door pins are super tight - they were perfect and easy to move when I
first fit them years ago. The handle requires a lot of force now to get the
pins all the way in. Will this improve with time, or should I make some
adjustments to the pins or the receiver tubes? Grease helps a bit, but not
enough.

Doors fit great, but I did have to use heat on inside of doors to make them
relax. Still required a bit of filling here and there.

Thanks in advance,
Dennis

On Tue, Oct 6, 2009 at 8:08 PM, <nmflyer1 at aol.com> wrote:

> Al,
>
> I too was not too keen on such beautiful aircraft having the aft potion of
> the doors bending under the load & heat. My approach was slightly different
> than yours:
>
> I purchased some gas springs that had half the force of the factory
> originals (mine are 30 pounds). Then I ended up working on the attach points
> to stiffen things up on the door, and find a place that would work for
> mounting the new springs.
> The spring source I used is :
> http://www.spdhardware.com/catalog/list.asp?id={A818FF64-E51A-422F-A59A-4E2E52A3BDA2<http://www.spdhardware.com/catalog/list.asp?id=%7BA818FF64-E51A-422F-A59A-4E2E52A3BDA2>}
> and the springs I used are the 5300-30's.
> I made a quick look over the site and didn't see a 23" extension spring. I
> am sure you measured attach point to attach point, but the closest they have
> is a 20" one on their website.
> You can always call them, but just make an inquirey and write down the part
> number if they have what you need. It is much cheaper to order off of the
> website. I think they have a minimum dollar amount on phone orders.
>
> The good news, My doors do not bend up at the back and they don't twist the
> door. The not so good news is that the door opens about 4" shorter height
> than the factory ones. Works for me since I'm short :)
>
> I also tried the "new method" while I was playing aroud and really did not
> like the front-door-twist, or the slamming at the lower end. Same results
> that you had.
>
> Kurt Winker
>
>
>
>
>
> -----Original Message-----
>
>
> From: Al Gietzen <ALVentures at cox.net>
> To: reflector <reflector at tvbf.org>
> Sent: Tue, Oct 6, 2009 7:30 pm
> Subject: REFLECTOR: Door strut review
>
>   This is just a story about different door strut configurations and
> issues which may be of interest to builders who have not yet installed them,
> or those who may not like the way the door works.  I’ve now had experience
> with original version of the strut, my modified original version, and the
> new version.
>
> First I’ll mention a couple of things I really like about the new door and
> hardware.  In fitting up the new door, I was pleasantly surprised and
> impressed that its shape matched up very nicely to the fuselage – much
> better than the original had.  Remember all that discussion years back about
> heating the doors to get them to fit right? And the over-center spring on
> the latch crank is much stiffer than the earlier version – good idea.
>
> Those of you that built your plane some years ago with the elite doo rs
> know that there were some issues with the door struts.  They fastened to the
> door up at the back corner, tended to twist the door toward the back, and
> caused distortion so the top rear of the door tended to stick up above the
> fuselage surface. Disappointing after you had carefully fit the door.
>
> My solution to that was to install a new hardpoint further forward in the
> doorframe; just in front of the rear hinge.  This took away the twisting
> force by putting the force between the hinges and perpendicular to the hinge
> line (See photo 1). Of course this didn’t eliminate the force tending to
> bend the door up in back. Noting that most of the bending was between the
> top frame and the hinge line, I reinforced that area with about 5 plies of
> BID, with a ply of fine BID over (photo 2).  This eliminated most of the
> problem, and with a little filler on the fuselage, all was copasetic. The
> behavior of the door was nice, and had a slight closing force near the end
> of travel.
>
> After that someone came up with the idea of a longer strut, connected
> further down on the door, along with the claim that it eliminated the
> distortion of the door, worked better, etc; and the design was adopted by
> Velocity for subsequent kits. So naturally in replacing my door I chose
> the new approach so I wouldn’t have to install a new hardpoint and reinforce
> the hinge area – even though it wouldn’t match the other side.
>
> After fitting up the new door and hinges to nicely fit the existing op
> ening; I installed the strut per the current instructions.  Yikes – the
> bottom front corner was now coming to close position almost ¼ - 3/8” too far
> forward.  And from about the 2’ open point it wants to SLAM shut.  If
> person had their fingers over the edge and wasn’t sure to restrain the door
> you could loose a finger. And now the downward force on the rear hinge, and
> the resultant distortion, was about the same as in the original top corner
> approach – except downward instead of upward.
>
> So a caution to those still building: install the strut BEFORE doing the
> final fitup of the door to the fuselage.
>
> Had I reviewed the strut installation geometry, and the resultant force
> compone nts, before installing; I would have realized the likely result, and
> done as I did with the original.  With the current strut (photo 3, yes, I
> painted it the match the interior), the forward component of the force on
> the door during the stroke is nearly 30 lbs, pushing forward, which is why
> the door gets so twisted out of alignment toward the front.  The new
> geometry gives the strut much more mechanical advantage on the door, which
> could be a good thing for holding the door open, and allowing a lower strut
> force rating; except when the door is open a good percentage of the force is
> directed forward instead of upward. That same advantage requires much more
> force to open or close the door, and makes it want to slam.  I’m sure one
> can get used to that; if that’s a characteristic you like.
>
> The door frame is very rigid longitudinally, as down the sides of the door;
> but the force in the hinge area is transverse to the upper beam, and
> although there are some carbon plies in there, the distortion is basically
> between the upper beam and the hinge line.  So again I re inforced the
> hinge area as before; which solved most of the problem of the distortion of
> the hinge area.  Nonetheless, the 60 lb strut still has about 12-15 lb in
> excess of that needed for my door.
>
> So the unshod is that I definitely prefer my original modified strut and
> orientation.  Putting a new hardpoint into the upper door frame to install
> that strut is fairly easy – drill a couple of holes about ¾” dia just
> forward of where you want to mount the bracket, make a fairly still mix of
> epoxy and 50/50 mico and milled fiber and fill in the space behind where you
> want to mount the bracket. Light and strong.
>
> The replacement for the original door is readily available from
> McMaster-Carr (part #9416K17, $12.85).
>
> Before I consider a rework to my earlier version of strut; I’d like to try
> a 45-50 # strut in the new configuration.  So far I haven’t found any vendor
> for a strut with 23” extended length with the lesser rating – which may be
> why Velocity supplies the 60#.  Anyone know a source I should check?
> (e.i.; if you happened to be interested enough to read this farJ).
>
> Al
>
>
>
>
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-- 
All the best,
Dennis
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