REFLECTOR: Delaminated Canard Top -- Safety of Flight Issues?

Tue Feb 22 19:48:54 CST 2011

It's *probably* safe, but I'd do the slurry fix before I flew personally. I
would at least consider putting   some holes (3/32" ?) to let the pressure
equalize if you're going to fly high before the fix. Maybe it won't   get
worse without air pressure trapped under the skin.    Brett

   	-------Original Message-------
  From: Bob Jackson (Jax Tech)
  To: 'Velocity Aircraft Owners and Builders list'
  Subject: Re: REFLECTOR: Delaminated Canard Top -- Safety of Flight
Issues?
  Sent: 22 Feb '11 20:18

We would like to think and hope that it's just  paint delamination.  We do
have several layers of Awlgrip polyurethane on the  canard!

How could you tell it was just the paint  and not the skin and all when you
had your problem?  To my ear, our coin  tapping indicates more than just
paint problems.

We're inclined to follow Scott Baker's  advice and to fill the voids by
injecting an epoxy slurry, while building a  completely new canard to
replace it with -- but, how concerned would you be  with flying without
making any repairs? 

Maybe it's just buckled paint -- that  would be nice!

Thanks for the ideas,

Bob

          --------------------

FROM: reflector-bounces at tvbf.org  [mailto:reflector-bounces at tvbf.org] ON
BEHALF  OF Scott Derrick
  SENT: Tuesday, February 22, 2011  7:55 PM
  TO: Velocity Aircraft Owners and  Builders list
  SUBJECT: Re: REFLECTOR:  Delaminated Canard Top -- Safety of Flight
Issues?

Bob,

  Are you sure its not just paint de-lamination?  I had that occur on my
canard when I used a water born urethane product. 

  Scott

  -------- Original Message --------
  Subject: REFLECTOR: Delaminated Canard Top -- Safety of Flight Issues?
  From: Bob Jackson [LINK: mailto:bobj at computer.org]
  To: 'Velocity Aircraft Owners and Builders list' [LINK:
mailto:reflector at tvbf.org]
  Date: 02/22/2011 11:47 AM

After 350+ hours of flying, yesterday while cruising at  18,000' with
perfect light from a setting sun, we noticed some 'bubbling' along  the top
surface of the canard.  Once back on the deck, a little coin  tapping
confirmed that the top canard skin had delaminated in several  places.  The
worst bubble is right under the fifth set of VGs counting  from the canard
tip inward, and was about 6" long (fore-and-aft) and 2 to  3" wide
(side-to-side).  This bubble looked like it was raised almost  1/4" in
flight at altitude!  On this flight the gross aircraft weight  was about
3400 pounds.

In addition while in the air, another area of  delamination that extended
nearly to the canard tip, along the top of the spar  and several inches
fore-and-aft (but only separated about 1/8" above the  canard foam) was
visible.  On a subsequent flight just up to 5000 ft (and  about a 3100 #
aircraft gross weight), only the slightest amount of  delamination bubbling
could be seen, and only under the 5th set of VGs. 

I believe our plane is more susceptible to canard  delamination because of
our very high max gross weights (3600 pounds), and high  altitude operation
(up to 25 Kft) where the sea level pressure air trapped  inside the canard
on take-off will be pushing outward on the canard skin when  we're cruising
at altitude before the pressures can   equalize.

Our canard was made by Alan at Wingco close to 15  years ago, and
apparently he was using a two step vacuum bagging technique at  the time
that Dwayne Swing says was generally more prone to delamination than  the
standard canard construction process outlined in the manual.  We still
need to 'coin tap' test the bottom of the canard to make sure we don't have
any  delamination on the bottom.

Eventually, we plan to build another canard that is a  foot or two longer
to better carry our higher aircraft weights and canard  loadings -- so it
doesn't bend up as much in flight, which will also create  delaminating
stresses.

The questions for the group   are:

Â· How much of a   safety of flight issue do you think it is to continue
flying with this   degree of canard delamination until we can repair it or
build a new canard?
Â· Who else has   experienced canard delamination, and did you have similar
'extenuating   circumstances' to ours (like high gross weight or high
altitude   operations) that might help to explain it.  Also, was it with a
 Wingco 'Fastbuild' canard?

Thanks,

Bob Jackson

N2XF

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