REFLECTOR: Do Plans include Carbon Fiber "Y"?

Fri Oct 9 16:54:52 CDT 2009

Hi,

Maybe this is overly simplistic, but sure you have eliminated all the easy
stuff first.  Does the door fit OK when it is unhinged and not connected to
the opening strut?  I had trouble setting the depth of my hinges both on the
door and on the ceiling.  Are you looking from the inside.  Is the strut
travel imposing a load either by vertical or horizonal travel or
misalignment.  I have McMaster Carr cylinders as door struts.  Even if you
did it all correctly the "fix" could be in shimming experiments.  

Terry

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Tony Babb
Sent: Friday, October 09, 2009 16:26
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Do Plans include Carbon Fiber "Y"?

I'm having a hard time picturing this in what's left of my mind. Are there
any photos available? It would really be helpful if someone at the factory
could update us on their current practice and recommendations.

Thanks,

Tony Babb

SEFG 62% done, 78% to go

www.alejandra.net/velocity

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Al Gietzen
Sent: Friday, October 09, 2009 8:01 AM
To: 'Jim Agnew'; 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Do Plans include Carbon Fiber "Y"?

Jim;

Thanks for the clarification.  That sounds much better than just the "Y"

Al

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Jim Agnew
Sent: Thursday, October 08, 2009 6:56 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Do Plans include Carbon Fiber "Y"?

To Al & Dennis,

I have a carbon fiber roll cage12" wide that runs down the overhead  from a
Y about 18" in front of the engine bulkhead  that connects to the very heavy
triax layups for the engine mounts to the overhead of the front window and
down into the lower fuselage along the front of the door beams and is tied
across the middle between the door rear carbon beams.  I covered all of the
overhead carbon with a wider strip of Kevlar containment in case the cage is
over stressed and shatters into the sharp carbon pieces.  Mounting the
engine did not in any way alter the shape of my fuselage that I can detect.

Jim

James F. Agnew

Jim_Agnew_2 at Yahoo.Com

Tampa, FL

Velocity 173 Elite Aircraft Completed & Flying

  _____  

From: Al Gietzen <ALVentures at cox.net>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Thu, October 8, 2009 8:20:51 PM
Subject: Re: REFLECTOR: Do Plans include Carbon Fiber "Y"?

Dennis;

I'd assume that the increase in difficulty of latching your doors is still a
result of distortion in the fuselage.

Some reinforcement helps; although hard to know how to reinforce without
knowing what the stress distribution is.  My best guess is that the forces
on the firewall (and carried into the spar and strakes from the engine, and
further, from the swept back wings); create a distortion of the
cross-section of the fuselage forward in the area of the doors, as well as
pulling back on the top.  That's why when you put the jacks under the wings
the doors latch more easily.

My approach to strengthening was to continue the carbon side beams across
the top (I think this may now be standard), reinforce the small beam at the
front of the door and across the over head panel.  I then added foam core
beams across the top of the doors, and down the center from the mid cross
beam back to the firewall.  The center beam is in place of the V channel
that has become standard.  I'm also guessing that more circumferential
rigidity at the front of the door would reduce the distortion.

It added a few pounds, and I wouldn't say it's necessary, but it added
strength and rigidity.  When the engine and wings were added, not much
notable change in the door fit, but it did take more force to latch the
door.

Terry makes a good point - keep the doors closed, when the plane is sitting
around.  In the few months that mine sat without the left door, the right
door became more difficult to latch.  The doors are part of the load
carrying structure.  Composites are very strong and light, but they are
subject to viscoelastic creep at much lower temperatures than metals.
(Don't ya just love that "viscoelastic creep".  Sounds like something that
should only happen on Halloween J.  I did a lot of finite-element,
viscoelastic creep analysis of high temperature metals way back when).

Al

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Dennis Martin
Sent: Thursday, October 08, 2009 7:08 AM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Do Plans include Carbon Fiber "Y"?

Al Gietzen mentioned this geometry issue in a post yesterday, and Jim Agnew
advised me to install carbon reinforcement back in the late 90s. Here's the
thing. The entire fuselage will distort after you hang the engine on - and
doors may no longer fit properly. Physical forces from engine weight will
change all of the geometry.

Jim advised laying up a 2-bid carbon fiber "Y" on the top of the fuselage
(inside cabin). I don't know if it's in the plans by now, but I think it
should be a standard part of the build. I did this about 6 years ago before
installing the engine. I laid up a 12" wide carbon fiber "Y" on the ceiling
of the fuselage. The two branches of the Y go to the firewall, and attach
about 3 inches down onto the wall to add extra strength where firewall and
cabin intersect. The two branches of the Y meet about in the middle of the
cabin, then the trunk of the Y runs all the way to the front windscreen.

Added benefit is a stronger "egg" in case you ever end up in a ground loop.

My engine weighs 450 pounds, and my cabin is true to the original. Doors fit
same as when I first installed them. Door pins are tight, so there might be
minor distortion. But that should be easy to fix. 

-- 
All the best,
Dennis

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