REFLECTOR: Jeffco or not?

[Andy Millin]

Hey Grigore,

Joe is a pretty savvy builder, and I agree with everything he wrote.

I too bought my Jeffco from the factory.  They now have a slower hardener
that will give you better working time.  The color difference from the EZ-84
provides great contrast.  Much easier to tell if you have a thin spot.

I did flange the tops of the baffles.  Very grateful to Joe for sending the
pics and write-up.  I too was able to complete the strakes without flipping
the plane.  I also was fortunate enough to have the strakes hold pressure
for 24+ hours.  Whew...

As for the lower strake/removing the wing question:  I spoke with Rob
Johnson some time ago.  Many of the "Old Timers" on the list will remember
the Ditch Master.  Rob did not have room to put both wings on in his garage.
His solution was to roll the fuselage out of the garage, install the wings,
install the lower strakes, remove the wings, and roll it back into the
garage to complete the strakes.  He did it all in one weekend!

Much later when he put the wings on, they were misaligned by about 1/2" on
each side.  His experience said the strakes are not locked-in until the
upper skin is bonded on.  I listened to his experience, and did not remove
the wing until the strake was completed.

I know this method worked.  I have had the wings back on a couple times
since then and everything still lines up.  The other thing that we did not
get into was wing incidence.  If the strakes were no longer aligned with the
wing, then one could reason the incidence of the strake, wing, or both was
no longer what was desired.  Brendan had written about this in his "The Sh*t
that Flies" column.  A Velocity can fly with things really out of alignment.
Almost by definition, it will mean drag and a slower airplane.  One of the
best drag reduction favors you can do for yourself is to build a true
airframe.

One small tip on the strakes.  Most of us use a bottle jack on some type of
stand on the outboard wing to hold the incidence during strake construction.
Bottle jacks are not meant to hold the same position indefinitely.  Some
know this lesson in a painful way.  They WILL slowly bleed down.  I used
hose clamps around the ram of the jack to lock it in place.  There is a
picture somewhere on my site.  It worked very well.

I liked Joe's idea of using a balloon.  I used a simple water manometer.
Remember, you are looking for a good seal not a precise measurement while
you are checking.  If it can hold pressure for 24 hours, you should be
good-to-go.

Andy



-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Joe Ewen
Sent: 01-28-2008 8:20
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Jeffco or not?

Grigore,
1-I believe the Jeffco is considered the preferred approach.  I bought mine
from the factory.
 
2-I used a balloon to test my tank.  After sealing the fuel cap with 4"
masking tape, a balloon was connected to the vent line and air blown into
the tank's fuel supply line.  A temporary valve in the supply line was
closed.  I tested my tanks individually for 24+ hours.  During that time the
balloon contracted due to temperature change, but came back to original
inflation when the temperature came back up.  In fact one balloon burst from
the higher temp the next afternoon.  
 
3-I completed one strake then worked on the second.  May be personal
preference, learn on the first and the second is usually constructed more
efficiently.  I left the wings on until the strakes were finished.  
 
I departed from the manual on a couple of techniques.  One was I used Ronnie
Brown's procedure for making the baffle templates (I believe he outlines the
process on his web site.)  The other departure was to create flanges on the
upper portion of the bulkhead and baffles to eliminate the need for
inverting the fuselage.  I shared this approach with Andy M, if he used the
technique maybe he can comment of his success. 
 
At the time of construction my strakes tested leak free.  I will be
retesting now that I am close to completion and hope they are still leak
free.
 
Joe
 

	----- Original Message ----- 
	From: Grigore Rosu <mailto:grigore.rosu at gmail.com>  
	To: Velocity Aircraft Owners and Builders list
<mailto:reflector at tvbf.org>  
	Sent: Monday, January 28, 2008 1:34 AM
	Subject: REFLECTOR: Jeffco or not?

	I'm about to install the bulkheads in my first strake and therefore
I'll soon need to worry about the fuel tank.
	 
	1) Should I use Jeffco or not?  The manual sounds as if Jeffco is
optional ...  If I should use it, where can I get it from?  (I can do a
random search on the internet, but perhaps there are some better avenues
that you may have encountered so far).
	 
	2) Do I need an altimeter to test the fuel tank?  I have none, but
the messages I could find in the reflector archive on this subject mention
an altimeter.  BTW, can I test each tank in isolation, or they need to be
both installed first and checked together?
	 
	3) Should I finish the first strake (including installing the upper
strake) and then move to the other one, or it is better to also install the
lower strake on the other side and its bulkheads, then do both tanks at the
same time, and then install both upper strakes at the same time?  Note that
I can only install one wing at a time in my garage.  The flow-chart that
came with my manual says that the wing can be removed once the lower strake
is installed ... I'm a bit reluctant to do so though, because I'm afraid the
torsion generated by the spar may be too big without the upper strake.
	 
	Thank you,
	Grigore
	 

	
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