 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
Bob Barrow
Joined: 11 Jan 2006
Posts: 29
|
 Posted: Mon Mar 27, 2006 6:43 pm Post subject: Tip tanks (more) |
 |
|
I also plan on using tip tanks on my RV7A. And I've also been pondering this
fuel feed question for at least 12 months. This is a very good thread and
timely for me.
I've seen many solutions (actually flying) for feeding fuel from the tips
and I've listed a few below with a few of my comments on each. Just my
opinion of course and I welcome further feedback.
1. Floating "cistern" style valve in main tank. Opens valve to allow fuel to
flow from tip to main when fuel in main gets down to a certain level.
Advantages: Fully automatic..nothing to do or remember. No chance of fuel
being vented from mains vent. Disadvantages: No suitable valve available on
the market as far as I know which means you have to manufacture it. May be
prone to mechanical failure. A nightmare to get to if it fails. Conclusion:
Not for me.
2. Five way fuel selector. Andair sells them. Enables selection of either
mains or either tips individually.
Advantages: 100% access to auxiliary fuel guaranteed. No check valves to
fail. No problems with differential vent pressures between mains and tips.
Disadvantages: You'll have to run the tips dry to empty them which means the
engine will stop. If you're not careful and you leave the tips selected you
might lose engine power at a bad time. Conclusion: A potentially dangerous
set-up if you get distracted. Using all useable fuel in flight essentailly
means running a tank dry. Not for me.
3. One way mechanical valve. Andair sells them and they are fitted between
the tips and the mains.
Advantages: Very reliable in terms of fuel availability and nothing to
remember. Disadvantages: Can result in fuel overflowing through mains vent
if pressure differential not precise. Once flow starts it may be assisted
by siphon effect. When the plane is parked with full mains, fuel will seep
back through the one-way valve and refill the tips. This can be a problem
for accurate fuel measurement. It also precludes any aerobatics until the
fuel can be pumped back into the mains in flight. Also requires a well
sealing fuel cap to prevent fuel loss at the cap (that excludes Vans caps
which are terrible). Conclusion: Popular solution but not without problems.
4. Electric fuel pump between tips and mains.
Advantages: Fast fuel transfer. Control of flow. Disadvantages: Requires
electric power to gain access to aux fuel. The pump introduces another
failure point. If the mains are full when the pump is switched on then all
the tip fuel will be pumped overboard. Conclusion: Unnecessarily
complicated.
5. Straight feed between tips and mains. No check valve.
Advantages: Completely outweighed by disadvanteges. Disadvantages: No way to
control fuel from feeding back into the tips while parked or in flight. If
it occurs in flight it could result in fuel exhaustion. It could also result
in an irretrievable spin if aerobatics attempted. Conclusion: Not practical
as far as I can see.
6. Tips to mains through fuel selector. Calls for routing the tips fuel into
the cabin to auxiliary selector(s) and then to the mains.
Advantages: Virtually guaranteed fuel supply if correct selection made.
Disadvantages: Additional fuel plumbing in wing and cabin. Additional fuel
selectors which may present problems in terms of location, access and
accidental movement of selector by pilot or passenger. Conclusion: Messy
plumbing in cabin and fuel selectors everywhere.
7. One way electric solenoid. Fitted between tips and mains.
Advantages: Complete control of fuel flow. Fuel can be retained in tips
until mains reduced to avoid any possibility of fuel overflowing from mains
vent or leaking fuel cap. Positive valve action will prevent fuel seeping
back into the tips while plane parked. Disadvantages: Requires electric
power to enable access to aux fuel. Relatively slow fuel transfer (but
should exceed fuel flow required for 100% engine power). Conclusion: Not
perfect, but might be best of the bunch.
Have others had success with an electric solenoid. If so, what type of
solenoid did you use. If you've had problems with this arrangement I'd like
to know about that as well.
careerone.com.au
http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fadsfac%2Enet%2Flink%2Easp%3Fcc%3DNWS014%2E19163%2E0%26clk%3D1%26creativeID%3D28927&_t=752722611&_m=EXT
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
 |
Fred.Stucklen(at)UTCPower
Guest
|
| Posted: Tue Mar 28, 2006 7:00 am Post subject: Tip tanks (more) |
|
|
Bob,
Per your item #5 below, (Straight feed between tips and mains.
No check valve.) flow to the tip tanks can be some what
mitigated by the position of the inlet to the main tank (from the tip
tank). Jon's plans call for this fitting to be in the center of the tank
height. This results in there always being fuel in the main tank, and
the inability to drain to the tip tank once the main tank level goes
below the level of this fitting. This is something like 10 gals of fuel.
It also takes a fair amount of time for the tip tanks to refill, and the
aircraft must be in an abnormal position (wing low on a ramp, or
a continuous slip) for that time period to have a substantial amount
of fuel drain out of the main. In flight, if the low wing were selected,
you would also run the risk of un-porting the fuel pickup before a
substantial amount of fuel were moved (but this is another problem).
What I like about this setup is that there in no pilot input required
to utilize the tip tank fuel: no fuel selector to forget to position, no
electric pump or solenoid to forget to shutoff.. If there is fuel in the
tip tank, then the main tank is always full.
I'm in the process of trying this setup out. I'll post to the list the
results of my tests. I should have it completed for the trip to
Sun 'N Fun next week (4/6 - 4/7 for me...).
Time: 06:43:00 PM PST US
From: "Bob Barrow" < bobbarrow10(at)hotmail.com
<mailto:bobbarrow10(at)hotmail.com> >
Subject: Tip tanks (more)
<mailto:bobbarrow10(at)hotmail.com> >
I also plan on using tip tanks on my RV7A. And I've also been
pondering this
fuel feed question for at least 12 months. This is a very good thread
and
timely for me.
I've seen many solutions (actually flying) for feeding fuel from the
tips
and I've listed a few below with a few of my comments on each. Just
my
opinion of course and I welcome further feedback.
1. Floating "cistern" style valve in main tank. Opens valve to allow
fuel to
flow from tip to main when fuel in main gets down to a certain level.
Advantages: Fully automatic..nothing to do or remember. No chance of
fuel
being vented from mains vent. Disadvantages: No suitable valve
available on
the market as far as I know which means you have to manufacture it.
May be
prone to mechanical failure. A nightmare to get to if it fails.
Conclusion:
Not for me.
2. Five way fuel selector. Andair sells them. Enables selection of
either
mains or either tips individually.
Advantages: 100% access to auxiliary fuel guaranteed. No check valves
to
fail. No problems with differential vent pressures between mains and
tips.
Disadvantages: You'll have to run the tips dry to empty them which
means the
engine will stop. If you're not careful and you leave the tips
selected you
might lose engine power at a bad time. Conclusion: A potentially
dangerous
set-up if you get distracted. Using all useable fuel in flight
essentially
means running a tank dry. Not for me.
3. One way mechanical valve. Andair sells them and they are fitted
between
the tips and the mains.
Advantages: Very reliable in terms of fuel availability and nothing to
remember. Disadvantages: Can result in fuel overflowing through mains
vent
if pressure differential not precise. Once flow starts it may be
assisted
by siphon effect. When the plane is parked with full mains, fuel will
seep
back through the one-way valve and refill the tips. This can be a
problem
for accurate fuel measurement. It also precludes any aerobatics until
the
fuel can be pumped back into the mains in flight. Also requires a well
sealing fuel cap to prevent fuel loss at the cap (that excludes Vans
caps
which are terrible). Conclusion: Popular solution but not without
problems.
4. Electric fuel pump between tips and mains.
Advantages: Fast fuel transfer. Control of flow. Disadvantages:
Requires
electric power to gain access to aux fuel. The pump introduces another
failure point. If the mains are full when the pump is switched on then
all
the tip fuel will be pumped overboard. Conclusion: Unnecessarily
complicated.
5. Straight feed between tips and mains. No check valve.
Advantages: Completely outweighed by disadvantages. Disadvantages: No
way to
control fuel from feeding back into the tips while parked or in
flight. If
it occurs in flight it could result in fuel exhaustion. It could also
result
in an irretrievable spin if aerobatics attempted. Conclusion: Not
practical
as far as I can see.
6. Tips to mains through fuel selector. Calls for routing the tips
fuel into
the cabin to auxiliary selector(s) and then to the mains.
Advantages: Virtually guaranteed fuel supply if correct selection
made.
Disadvantages: Additional fuel plumbing in wing and cabin. Additional
fuel
selectors which may present problems in terms of location, access and
accidental movement of selector by pilot or passenger. Conclusion:
Messy
plumbing in cabin and fuel selectors everywhere.
7. One way electric solenoid. Fitted between tips and mains.
Advantages: Complete control of fuel flow. Fuel can be retained in
tips
until mains reduced to avoid any possibility of fuel overflowing from
mains
vent or leaking fuel cap. Positive valve action will prevent fuel
seeping
back into the tips while plane parked. Disadvantages: Requires
electric
power to enable access to aux fuel. Relatively slow fuel transfer (but
should exceed fuel flow required for 100% engine power). Conclusion:
Not
perfect, but might be best of the bunch.
Have others had success with an electric solenoid. If so, what type of
solenoid did you use. If you've had problems with this arrangement I'd
like
to know about that as well.
careerone.com.au
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
Bob Barrow
Joined: 11 Jan 2006
Posts: 29
|
| Posted: Tue Mar 28, 2006 6:06 pm Post subject: Tip tanks (more) |
|
|
Hi Fred, thanks for your comments. I actually received quite a lot of
replies to my post but for some reason people chose to email me directly. I
appreciated all of the comments but I would ask people to respond through
this forum because it enables everyone to gain benefit from the diversity of
opinion and experience.
In terms of your specific direction re straight feed. There are a number of
reasons I feel reluctant to go that way but I will raise just one.
The ability of the RV to recover from a spin depends primarily on the
capacity of the rudders' authority to overcome the moment of the spinning
wings. And because moment is lever arm multiplied by mass it therefore stand
to reason that even a small increase in mass at the wing tips will grossly
increase the moment. For a start all tip tanks will add at least 6 lbs over
the weight of standard tips (dry weight). That alone may influence spin
recovery.
Any additional mass in the form of fuel in the tips (extra 1kg per litre
approx) could prove fatal in a spin....even a very small quantity (say just
3 or 4 litres) may lead to an unrecoverable spin. On the other hand it may
not...it might take 10 litres...but I for one will not be the test pilot
finding out where the limit is.
So I would say that it would be very prudent not to get into a spin with any
fuel whatsoever in the tips. And the straight feed solution can never
guarantee that the tips are completely empty. So aerobatics would be out of
the question...firstly because they would guarantee that fuel would run to
the tips...and secondly because it greatly increases the chances of an
inadvertent spin.
As Einstein was reported to have said: " A mechanism should be as simple as
practicable...but no simpler" (or words to that effect). In aviation
oversimplification can introduce risk...just look at Van's nose gear.
| Quote: | From: "Stucklen, Frederic W UTPWR" <Fred.Stucklen(at)UTCPower.com>
Reply-To: rv-list(at)matronics.com
To: "'Bob Barrow'" <bobbarrow10(at)hotmail.com>
CC: "'RV-List'" <rv-list(at)matronics.com>
Subject: Re: Tip tanks (more)
Date: Tue, 28 Mar 2006 09:57:00 -0500
<Fred.Stucklen(at)UTCPower.com>
Bob,
Per your item #5 below, (Straight feed between tips and mains.
No check valve.) flow to the tip tanks can be some what
mitigated by the position of the inlet to the main tank (from the tip
tank). Jon's plans call for this fitting to be in the center of the tank
height. This results in there always being fuel in the main tank, and
the inability to drain to the tip tank once the main tank level goes
below the level of this fitting. This is something like 10 gals of fuel.
It also takes a fair amount of time for the tip tanks to refill, and the
aircraft must be in an abnormal position (wing low on a ramp, or
a continuous slip) for that time period to have a substantial amount
of fuel drain out of the main. In flight, if the low wing were selected,
you would also run the risk of un-porting the fuel pickup before a
substantial amount of fuel were moved (but this is another problem).
What I like about this setup is that there in no pilot input required
to utilize the tip tank fuel: no fuel selector to forget to position, no
electric pump or solenoid to forget to shutoff.. If there is fuel in the
tip tank, then the main tank is always full.
I'm in the process of trying this setup out. I'll post to the list the
results of my tests. I should have it completed for the trip to
Sun 'N Fun next week (4/6 - 4/7 for me...).
Time: 06:43:00 PM PST US
From: "Bob Barrow" < bobbarrow10(at)hotmail.com
<mailto:bobbarrow10(at)hotmail.com> >
Subject: Tip tanks (more)
bobbarrow10(at)hotmail.com
<mailto:bobbarrow10(at)hotmail.com> >
I also plan on using tip tanks on my RV7A. And I've also been
pondering this
fuel feed question for at least 12 months. This is a very good
thread
and
timely for me.
I've seen many solutions (actually flying) for feeding fuel from the
tips
and I've listed a few below with a few of my comments on each. Just
my
opinion of course and I welcome further feedback.
1. Floating "cistern" style valve in main tank. Opens valve to allow
fuel to
flow from tip to main when fuel in main gets down to a certain
level.
Advantages: Fully automatic..nothing to do or remember. No chance of
fuel
being vented from mains vent. Disadvantages: No suitable valve
available on
the market as far as I know which means you have to manufacture it.
May be
prone to mechanical failure. A nightmare to get to if it fails.
Conclusion:
Not for me.
2. Five way fuel selector. Andair sells them. Enables selection of
either
mains or either tips individually.
Advantages: 100% access to auxiliary fuel guaranteed. No check
valves
to
fail. No problems with differential vent pressures between mains and
tips.
Disadvantages: You'll have to run the tips dry to empty them which
means the
engine will stop. If you're not careful and you leave the tips
selected you
might lose engine power at a bad time. Conclusion: A potentially
dangerous
set-up if you get distracted. Using all useable fuel in flight
essentially
means running a tank dry. Not for me.
3. One way mechanical valve. Andair sells them and they are fitted
between
the tips and the mains.
Advantages: Very reliable in terms of fuel availability and nothing
to
remember. Disadvantages: Can result in fuel overflowing through
mains
vent
if pressure differential not precise. Once flow starts it may be
assisted
by siphon effect. When the plane is parked with full mains, fuel
will
seep
back through the one-way valve and refill the tips. This can be a
problem
for accurate fuel measurement. It also precludes any aerobatics
until
the
fuel can be pumped back into the mains in flight. Also requires a
well
sealing fuel cap to prevent fuel loss at the cap (that excludes Vans
caps
which are terrible). Conclusion: Popular solution but not without
problems.
4. Electric fuel pump between tips and mains.
Advantages: Fast fuel transfer. Control of flow. Disadvantages:
Requires
electric power to gain access to aux fuel. The pump introduces
another
failure point. If the mains are full when the pump is switched on
then
all
the tip fuel will be pumped overboard. Conclusion: Unnecessarily
complicated.
5. Straight feed between tips and mains. No check valve.
Advantages: Completely outweighed by disadvantages. Disadvantages:
No
way to
control fuel from feeding back into the tips while parked or in
flight. If
it occurs in flight it could result in fuel exhaustion. It could
also
result
in an irretrievable spin if aerobatics attempted. Conclusion: Not
practical
as far as I can see.
6. Tips to mains through fuel selector. Calls for routing the tips
fuel into
the cabin to auxiliary selector(s) and then to the mains.
Advantages: Virtually guaranteed fuel supply if correct selection
made.
Disadvantages: Additional fuel plumbing in wing and cabin.
Additional
fuel
selectors which may present problems in terms of location, access
and
accidental movement of selector by pilot or passenger. Conclusion:
Messy
plumbing in cabin and fuel selectors everywhere.
7. One way electric solenoid. Fitted between tips and mains.
Advantages: Complete control of fuel flow. Fuel can be retained in
tips
until mains reduced to avoid any possibility of fuel overflowing
from
mains
vent or leaking fuel cap. Positive valve action will prevent fuel
seeping
back into the tips while plane parked. Disadvantages: Requires
electric
power to enable access to aux fuel. Relatively slow fuel transfer
(but
should exceed fuel flow required for 100% engine power). Conclusion:
Not
perfect, but might be best of the bunch.
Have others had success with an electric solenoid. If so, what type
of
solenoid did you use. If you've had problems with this arrangement
I'd
like
to know about that as well.
careerone.com.au
|
Want 1c text 24/7? Click here for details
http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fadsfac%2Enet%2Flink%2Easp%3Fcc%3DTEL185%2E19163%2E0%26clk%3D1%26creativeID%3D29997&_t=753375536&_m=EXT
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
Jerry Grimmonpre'
Joined: 09 Jan 2006
Posts: 144
Location: Huntley, Illinois 60142
|
| Posted: Tue Mar 28, 2006 6:48 pm Post subject: Tip tanks (more) |
|
|
DO NOT ARCHIVE
Bob ...
It may be that responders don't want to run the risk of being roasted by
critical remarks from others reading replies. We all miss out when fear of
roasting trumps willingness to share with the group. I learned a lot from
this thread. The largest thing was respecting what extra weight could do at
the wing tips.
Jerry Grimmonpre'
Sent: Tuesday, March 28, 2006 8:05 PM
Subject: Re: Tip tanks (more)
| Quote: |
Hi Fred, thanks for your comments. I actually received quite a lot of
replies to my post but for some reason people chose to email me directly.
I
appreciated all of the comments but I would ask people to respond through
this forum because it enables everyone to gain benefit from the diversity
of
opinion and experience.
|
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
rv8ch
Joined: 10 Jan 2006
Posts: 250
Location: Switzerland
|
| Posted: Tue Mar 28, 2006 8:44 pm Post subject: Tip tanks (more) |
|
|
| Quote: | The ability of the RV to recover from a spin depends primarily on the
capacity of the rudders' authority to overcome the moment of the spinning
wings. And because moment is lever arm multiplied by mass it therefore stand
to reason that even a small increase in mass at the wing tips will grossly
increase the moment. For a start all tip tanks will add at least 6 lbs over
the weight of standard tips (dry weight). That alone may influence spin
recovery.
|
Are you planning to test spin recovery with the tip tanks installed,
but empty, during your test phase? I have a friend with home grown
removable tip tanks on his RV4 - he said he removes them before
doing any aerobatics. Perhaps this is an option with the Johanson
tanks.
--
Mickey Coggins
http://www.rv8.ch/
#82007 finishing
do not archive
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
_________________
Mickey Coggins
http://www.rv8.ch/ |
|
| Back to top |
|
|
Terry Watson
Joined: 09 Jan 2006
Posts: 290
Location: Seattle, WA USA
|
| Posted: Tue Mar 28, 2006 9:47 pm Post subject: Tip tanks (more) |
|
|
I have Jon Johanson's tip tanks and have been following this discussion with
great interest. The change in the spin characteristics, even when empty,
does concern me, as does the fuel venting problems already discussed. I
haven't installed the tip tanks yet, and I still have the wingtips that came
with the kit so I still have options. I would NOT consider Jon's tanks as
"removable", although I'm sure some of you could remove and replace them
with regular wingtips, including the plumbing and wiring in a few hours if
you wanted. It would take me more like a week.
It would be helpful to me and others if you would let all of this discussion
go to the archives.
Thanks for all the great information, guys.
Terry
RV-8A #80729
Baffles
Seattle
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
Bob Barrow
Joined: 11 Jan 2006
Posts: 29
|
| Posted: Wed Mar 29, 2006 2:51 am Post subject: Tip tanks (more) |
|
|
Yes I am. At least an incipient spin...maybe even up to 2 turns.
I don't see that's it's practical to remove the tip tanks. The answer is to
keep them as light as absolutely possible. I know for a fact that some
home-built tip tanks end up weighing a ton...many builders don't even know
what their tip tanks weigh....they just keep slopping on the resin.
Standard Vans tips (one tip) are approximately 6.5 lb. Johanson tip tanks
vary but generally weigh between 11.0 and 12.5 lb (and they have no baffles
inside).
I certainly wouldn't want any fuel in the tips though...not a drop.
| Quote: | Are you planning to test spin recovery with the tip tanks installed,
but empty, during your test phase? I have a friend with home grown
removable tip tanks on his RV4 - he said he removes them before
doing any aerobatics. Perhaps this is an option with the Johanson
tanks.
--
Mickey Coggins
http://www.rv8.ch/
#82007 finishing
|
Make your dream car a reality
http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fcarpoint%2Eninemsn%2Ecom%2Eau&_t=12345&_r=emailtagline&_m=EXT
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
Fred.Stucklen(at)UTCPower
Guest
|
| Posted: Wed Mar 29, 2006 10:47 am Post subject: Tip tanks (more) |
|
|
First off, Jon explicitly states no aerobatics in his instructions.
He also states that the plane must be placarded against spins
if there is ANY fuel in the tip tanks. That's enough to convince
me to adhere to those instructions. I've intentionally spun my RV
during the test period (without tip tanks) and agree with Van's
observations that the RV6 (with the old vertical stab & rudder)
does not recover well (once established - might take 6 turns -
it took over three turns to recover...). Adding ANY weight to the
wing tip area will only make that recovery worst. I agree that
this includes the additional weight of an empty tip tank.
That said, it doesn't mean that adding the weight of extra fuel
to the wing tips for NORMAL flight condition, is dangerous. The
issue is the KNOW what the operational limitations are under
those condition, and to stay away from those limits. I'm
satisfied that the operational characteristics and limitations of
the RV6 with wing tanks is safe. And I don't plan on spinning the
aircraft intentionally. And knowing the limitations, I plan on staying
away from conditions that might induce a spin....
The original issue of these posts was to get information about
any venting issues from those flying their aircraft. To date, I've
only got feedback from one individual whose flying aircraft
experience a problem with draining the tip tanks while in flight.
He was able to modify the main tank vent slightly (from a 45*
angle into the airflow to a 30* angle) and demonstrate proper
operation. There has been no other flying aircraft (with tip
tanks) feedback...
So far, I'm the only flying aircraft (on the list) that has had the
opposite
problem - venting fuel out the main tank vents because of excessive
tip tank vent pressure relative to the main tank vent pressure.
I'm not comfortable with the dual vent design. I'm planning on
modifying that design (one side at a time) this weekend to a
single tip tank vent for both tanks. This will require the removal
of the check valve (& replacing it with a union) and capping off
the existing main tank vent. From an operational point, this
approach will always require the operator to fill the main tank
prior to adding any fuel to the tip tanks.
I'll keep the list informed of my progress and test results....
Fred Stucklen
RV-6A N926RV
<mailto:bobbarrow10(at)hotmail.com> bobbarrow10(at)hotmail.com>
Hi Fred, thanks for your comments. I actually received quite a lot of
replies to my post but for some reason people chose to email me
directly. I
appreciated all of the comments but I would ask people to respond
through
this forum because it enables everyone to gain benefit from the
diversity of
opinion and experience.
In terms of your specific direction re straight feed. There are a
number of
reasons I feel reluctant to go that way but I will raise just one.
The ability of the RV to recover from a spin depends primarily on the
capacity of the rudders' authority to overcome the moment of the
spinning
wings. And because moment is lever arm multiplied by mass it therefore
stand
to reason that even a small increase in mass at the wing tips will
grossly
increase the moment. For a start all tip tanks will add at least 6 lbs
over
the weight of standard tips (dry weight). That alone may influence
spin
recovery.
Any additional mass in the form of fuel in the tips (extra 1kg per
litre
approx) could prove fatal in a spin....even a very small quantity (say
just
3 or 4 litres) may lead to an unrecoverable spin. On the other hand it
may
not...it might take 10 litres...but I for one will not be the test
pilot
finding out where the limit is.
So I would say that it would be very prudent not to get into a spin
with any
fuel whatsoever in the tips. And the straight feed solution can never
guarantee that the tips are completely empty. So aerobatics would be
out of
the question...firstly because they would guarantee that fuel would
run to
the tips...and secondly because it greatly increases the chances of an
inadvertent spin.
As Einstein was reported to have said: " A mechanism should be as
simple as
practicable...but no simpler" (or words to that effect). In aviation
oversimplification can introduce risk...just look at Van's nose gear.
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
Bob Barrow
Joined: 11 Jan 2006
Posts: 29
|
| Posted: Wed Mar 29, 2006 3:24 pm Post subject: Tip tanks (more) |
|
|
Hi Fred, I must correct your statement below. Jon Johanson does not exclude
aerobatics when his tip tanks are installed. You must be misreading his
instructions. He specifically says no aeros when there's fuel in the
tips....that's all.
Of course there's always the small possibility that one might end up in an
inadvertent spin without doing aeros. So on that basis I wouldn't want to be
flying around with any fuel in the tips unless I specifically needed it for
a mission. On that basis I see it as important to be able to control fuel
from migrating from the mains to the tips at all times.
I look forward to recieving your feedback on your current experiment.
| Quote: |
<Fred.Stucklen(at)UTCPower.com>
First off, Jon explicitly states no aerobatics in his instructions.
He also states that the plane must be placarded against spins
if there is ANY fuel in the tip tanks. That's enough to convince
me to adhere to those instructions.
|
New year, new job there's more than 100,00 jobs at SEEK
http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek%2Ecom%2Eau&_t=752315885&_r=Jan05_tagline&_m=EXT
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
