REFLECTOR: Reflector Digest, Vol 30, Issue 15
matt
mbuc310 at cox.net
Sat Nov 4 10:52:56 CST 2006
Sorry Kevin, putting up drywall today. Come over & help, then tomorrow we
can move the plane into the shop!
Matt
-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of reflector-request at tvbf.org
Sent: Saturday, November 04, 2006 9:03 AM
To: reflector at tvbf.org
Subject: Reflector Digest, Vol 30, Issue 15
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Today's Topics:
1. Re: Phenolic Pad Options (Chuck Jensen)
2. engine.... (matt)
3. Re: engine.... (Velocity_AZ)
4. Re: Velocity 20B update (Al Gietzen)
----------------------------------------------------------------------
Message: 1
Date: Sat, 4 Nov 2006 07:54:54 -0500
From: "Chuck Jensen" <cjensen at dts9000.com>
Subject: Re: REFLECTOR: Phenolic Pad Options
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Message-ID: <8984A39879F2F5418251CBEEC9C689B3286D74 at lucky.dts.local>
Content-Type: text/plain; charset="us-ascii"
Kent,
Looks like a nice fix. The most important part of the fix is...you're
back in the air!!! Good job and good flying.
Chuck Jensen
Do Not Archive
-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Kent Murley
Sent: Saturday, November 04, 2006 2:17 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Phenolic Pad Options
Thank you Chuck Harbert, Jim Agnew, and Chuck Jensen for your responses
to my phenolic board replacement questions. I'm finally flying again and
using a thin stainless steel plate to protect my new left strut from
brake disc heat (picture attached). I'm still using a phenolic pad on my
right strut. Both are working well.
Not too evident in this picture: the leading edge of the SS plate is
curved inboard around a 6mm radius to provide some stability in the
relative wind but I doubt it is necessary. The plate still only contacts
the strut down by the axle. The orange RTV sealant may be providing some
rigidity but I would bet those two little dobs will dry out over the
years and fall out. I wonder if I can paint them.
To summarize: I have an XLRG with Cleveland brakes and toe pedal
actuators, a carbon fiber wrapped left strut (replaced this month after
some surface cracks revealed the original strut was damaged in an
off-airport landing 5 years ago by the previous owner) with stainless
steel heat barrier, and a standard wrapped right strut with a phenolic
board heat barrier.
Email me directly for more pictures of either strut, if you like.
Kent Murley
Tacoma Narrows WA
Chuck Jensen wrote:
Kent,
I was ready to reply to your email about a SS divider instead of
phenolic board but thought I would read the other posts first. Mmmmm,
nobody seems to be on the same path that I was ready to stumble down.
The reason for the phenolic board is not to protect the leg from radiant
heat, only conductive. Even though the air gap between disc and leg is
small, one would have to have a very hot heat source at that distance
for an extended period of time to start affecting the gear leg. Before
that radiant heat became a problem, there would have been so much heat
conducted through the bolts and surface attachment points that a little
radiant heat would be the least of our problems.
Looking at the overal design, it seems quite obvious that the
phenolic board is intended to be a thermal break to prevent conductive
transfer of heat. Yes, some will still make it through the bolts, but
the surface area of the bolts for heat transfer is small compared to the
area of the mating surfaces. Regarding the use of SS, yes, it is a poor
conductor compared to copper, but still quite efficient compared to
phenolic board. So the SS substituted is still a thermal break, but one
of modest value.
So, why do the SS plates work? Probably because there's not
much of a problem to begin with. With the older style, small Matco
brakes in the big XLRG, and the original brake-rudder tie-in, brakes
were worked a lot harder and got a lot hotter....a LOT hotter. With the
bigger Clevelands and their mass and ability to absorb energy, the whole
brake assembly rarely gets hotter than 'warm to the touch', so the
thermal break, be it phenolic or SS, is a solution to a problem that
barely exists anymore.
That's my theory and I'm stickin' to it.
Chuck Jensen
-----Original Message-----
From: reflector-bounces at tvbf.org
[mailto:reflector-bounces at tvbf.org] On Behalf Of Kent Murley
Sent: Thursday, October 05, 2006 11:05 PM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Phenolic Pad Options
Anybody use something other than phenolic pads to
protect their main struts from brake disc heat?
My situation:
XLRG
I changed to Cleveland brakes a dozen hours ago (and toe
pedals - love 'em) and installed new phenolic pads per the usual method:
the top of each phenolic pad runs vertically up each strut to a height
nearly a centimeter above each brake disc. The only attach points
between the phenolic pads and struts are down by the axle to minimize
transfer of heat.
The shape of my well used struts made the tops of the
phenolic pads warp away from the struts a couple centimeters and nearly
touch the brake disc. After the first flight one pad actually did touch
its disc - wearing an arc into the phenolic pad less than a millimeter
deep. I jambed a one centimeter spacer between the pads and the discs to
sit overnight. Neither pad has touched its disc since but they are close
- within 5 millimeters - and it varies after each flight. It may be the
strut or the phenolic pad or both that is changing shape with each set
of heat cycles.
For other reasons I'm now replacing the left main strut
and, after taking the wheel off, the phenolic pad has cracked and is
unusable, perhaps from my manipulation. Should I use a new phenolic pad
or can I fashion an aluminum (or other material) plate that would not be
subject to such large (3mm) flexure in heat cycles but still protect my
carbon fiber wrapped new strut from the hot disc?
Kent
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Message: 2
Date: Sat, 4 Nov 2006 07:57:30 -0700
From: "matt" <mbuc310 at cox.net>
Subject: REFLECTOR: engine....
To: <reflector at tvbf.org>
Message-ID: <LEELJEOFNLPEFHEJGIINGEEJCDAA.mbuc310 at cox.net>
Content-Type: text/plain; charset="us-ascii"
Any thought ever given to putting in 1 of these 420 shp Rolls-Royce
250-C20B? It is out of a MD 520N helicopter. Stick a PSRU on it,. run it
around 350 continout HP... 3 or 4 blade CS prop, single power lever control.
It is small, light and goes forever, at least till the fuel is gone.
Matt
------------------------------
Message: 3
Date: Sat, 4 Nov 2006 07:59:20 -0700
From: "Velocity_AZ" <velocity_az at cox.net>
Subject: Re: REFLECTOR: engine....
To: "'Velocity Aircraft Owners and Builders list'"
<reflector at tvbf.org>
Message-ID: <00cb01c70021$ced9ced0$6401a8c0 at Kevin>
Content-Type: text/plain; charset="us-ascii"
Can you break away to go fly now?
-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of matt
Sent: Saturday, November 04, 2006 7:58 AM
To: reflector at tvbf.org
Subject: REFLECTOR: engine....
Any thought ever given to putting in 1 of these 420 shp Rolls-Royce
250-C20B? It is out of a MD 520N helicopter. Stick a PSRU on it,. run it
around 350 continout HP... 3 or 4 blade CS prop, single power lever control.
It is small, light and goes forever, at least till the fuel is gone.
Matt
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Message: 4
Date: Sat, 4 Nov 2006 08:03:19 -0800
From: "Al Gietzen" <ALVentures at cox.net>
Subject: Re: REFLECTOR: Velocity 20B update
To: "'Velocity Aircraft Owners and Builders list'"
<reflector at tvbf.org>
Message-ID: <000001c7002a$bf44c4d0$6400a8c0 at BigAl>
Content-Type: text/plain; charset="iso-8859-1"
Elevator is not at max up position, but I do run out of trim, at about 170
KIAS. Faster than that the trailing edge is up 1 ?? or more, and that is
just a bit much. Also, at the low end the canard is stalling (gear down) at
75-80 kts, meaning landing speed is 90+, and end up with only about ??
trailing edge down on landing.
John wrote:
I'm far from an expert here, but it seems like shortening the canard will
make the stall problem worse. Seems like the canard incidence is up too
much. When you do a power off stall (flying solo) is the bucking strong,
mild, or just a mush? If it is strong-mild, then perhaps there is room to
reduce incidence.
I?m no expert either, but it?s more complicated when you add a ?fowler flap?
elevator to the airfoil. The issue seems to be the canard stalling before
you can get full down elevators. The incidence was initially set exactly to
the gauges (presuming they are correct). I then reduced the canard
incidence by about 1 degree (roughly 3/16? front to back on a 12? wide
canard). It helped, but not a lot. The advice from the factory was not to
decrease incidence further because of risk of reducing the differential
between canard and wing too much. The suggested options were to add VGs to
the wing, or shorten the canard. If my logic is correct, VGs on the wing
will help the low end condition, but not the top end.
Canard stall is more of a buffet and mush than pitch buck. I still have
about half the elevator cuff on, which reduces the pitch buck. Although at
the current landing condition trim of only ?? trailing edge down, the gap is
small and the cuff likely makes little difference.
I can trim the elevator full trailing edge down (on the ground), but not
full up ? so I am going to put a block between trim spring and the torque
tube bracket for more trim up
I don't recall the spring arrangement, but I seem to recall that a block
will move it in the other direction (less trim up). Maybe someone else
knows.
The trim spring attaches to the backside of the bracket on the torque tube.
The spacer block goes between the spring and the bracket which brings the
trailing edge further up.
I?d thought about reversing the sparrow strainer, but I?m concerned about
making it more pitch sensitive.
I did not notice any change in pitch sensitivity when I reversed the
strainer.
I think that is very interesting. Unless I misunderstand, the sole function
of the sparrow strainer is to increase the stick force in pitch at higher
speeds to reduce the ?apparent? pitch sensitivity. It makes you push harder
against the spring in one direction, and the airfoil load in the other.
Steve Murphree is suggesting I should put on a larger sparrow strainer.
Seems like this would cause you to run out of trim at an even slower IAS
because the strainer is working against the spring, pushing the elevator
down.
That is true. More work to be done. I am going to add some VGs on the
wings, and the spacer on the trim spring as the next step; and see how
things work. That should have effect (hopefully good) at both high and low
speed ends.
Al
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