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dtbushpilot
Ultra Nomad
Posts: 3290
Registered: 1-11-2007
Location: Buena Vista BCS
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Mood: Tranquilo
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That's a great visual of the difference DK, thanks.....dt
"Life is tough".....It's even tougher if you're stupid.....
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wilderone
Ultra Nomad
Posts: 3825
Registered: 2-9-2004
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"A sand mat is useful only for the time it is under your tire... "
I think it would be very useful in many situations, considering the various factors involved. Sand mats would be another tool available for the
occasion when it's required, like a shovel. In my case, I realized I needed more traction for the front tires to pull me out (had it in low 4WD),
rather than fix the rear problem. After I built a traction "ramp" for the front tires, I was able to power it out fairly easily. I don't think the R
rear ever got enough traction. The sand mats would have given me 4 ft. of instant traction. hmmmm 1/2" polyethelene with 1/4" bolts screwed in. I
found another site where a person inquired about aluminum "mats". I think you could make your own using the same bolts through a strong, flexible
material design. I've been stuck in the sand many times (other people driving - really!), and hasn't ever been a disaster - just part of the trip. I
would have been out much sooner had it not been so hot, had more sticks and traction materials available (the smooth river rock only made the tires
spin against them), and had another person to help. Live and learn.
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watizname
Senior Nomad
Posts: 774
Registered: 8-7-2009
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That picture is certainly worth a thousand words
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motoged
Elite Nomad
Posts: 6481
Registered: 7-31-2006
Location: Kamloops, BC
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Mood: Gettin' Better
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Quote: | Originally posted by David K
So a rattler can kill you... but you can't kill it??? So much for a government 'for the people'! |
David, David, David......tsk, tsk !!
That is "Government for the snakes"....
"Although snakes are widely feared, fewer than half a dozen deaths occur per year in the United States after snakebite. Lightning kills more people in
the United States than snakes do. However, serious injury and disability can result from a snakebite, such as the loss of a finger or the loss of
function at a joint."
# Approximately 8,000 people a year receive venomous snakebites in the U.S., 9-15 victims die. (FDA)
# 25% of adult rattlesnake bites are dry, with no venom injected.
http://lomalindahealth.org/medical-center/our-services/emerg...
http://www.desertusa.com/mag98/mar/stories/rattlesin.html
[Edited on 12-4-2010 by motoged]http://lomalindahealth.org/medical-center/our-services/emergency/programs-and-divisions/venom-er/resources/when-snakes-strike.page
[Edited on 12-4-2010 by motoged]
Don't believe everything you think....
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Barry A.
Select Nomad
Posts: 10007
Registered: 11-30-2003
Location: Redding, Northern CA
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Mood: optimistic
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How about BROWN RECLUSE and BLACK WIDOWS------should "we" protect them too??? perhaps reintroduce them to areas where they are seldom seen???? They
are part of "nature" you know. (on and on and on and on)
I will kill any animal that poses a serious threat to people, like these known dangerous animals in areas of human habitation or large use. Animals
in the real wild are a different matter------so I leave them alone, and give them a wide berth.
It is just a matter of priorities, I guess. As a Ranger I just have seen too many horrible results of people vs dangerous animals, mostly as a result
of people just not realizing the danger they put themselves in, and refusing to believe any warnings.
We used to move rattlers rather than kill them, but we found out that snakes bruise so easily that we were during fatal harm to them in the catching
process, more often than not, so we seldom moved snakes out of areas anymore-----just dispatch them.
Barry
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motoged
Elite Nomad
Posts: 6481
Registered: 7-31-2006
Location: Kamloops, BC
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Darwinian.....
Quote: | Originally posted by Barry A.
.... As a Ranger I just have seen too many horrible results of people vs dangerous animals, mostly as a result of people just not realizing the
danger they put themselves in, and refusing to believe any warnings.Barry |
Don't believe everything you think....
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Barry A.
Select Nomad
Posts: 10007
Registered: 11-30-2003
Location: Redding, Northern CA
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Mood: optimistic
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Quote: | Originally posted by motoged
Darwinian.....
Quote: | Originally posted by Barry A.
.... As a Ranger I just have seen too many horrible results of people vs dangerous animals, mostly as a result of people just not realizing the
danger they put themselves in, and refusing to believe any warnings.Barry | |
the reality
of that word has NOT escaped me, believe me.
Barry
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David K
Honored Nomad
Posts: 64859
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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Getting bit by a rattlesnake in Borrego Springs or Escondido is not the same as getting bit by one in central Baja... no cell phones, helicopter
medivac, then add being stuck in sand so you can't drive yourself out, if you could...
Of course, I am not one to talk when this photo of my 12 year old daughter made the Discover Baja magazine in 2003! (the Red
Diamondback was unharmed, and went on his merry way after the photo shoot!)
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BajaBlanca
Select Nomad
Posts: 13197
Registered: 10-28-2008
Location: La Bocana, BCS
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what an amazing photo - and your daughter's smile is precious. Can't say I wd be able to pose for the picture myself
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Brian L
Nomad
Posts: 250
Registered: 6-21-2010
Location: Alpine, CA
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Mood: No Bad Days
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Great picture!
Are you sure the stick wasn't harmed? Hmmmm??
Brian
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mojo_norte
Senior Nomad
Posts: 725
Registered: 2-14-2006
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Quote: | Originally posted by Cypress
Yea, that's a real healthy looking rattler. |
Beautiful snake - good for you for letting it be.
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vgabndo
Ultra Nomad
Posts: 3461
Registered: 12-8-2003
Location: Mt. Shasta, CA
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Mood: Checking-off my bucket list.
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I would venture to guess that more people are trampled to death by humans than are killed by rattlesnakes each year.
The real danger to humans on this planet is NOT wild animals; it is one of the self conscious mammals. The human animal. With the intelligence to
create fiendish weapons, but without the reason to control their use. We're the champions of intraspecies violence where the victim is not considered
food. I believe our closest relative is known to murder, but I believe there is also a use of the corpse for food.
Rattleshakes are cool if for no other reason than that they let us feel how our bodies have evolved to respond the the snakes warning. The suddenly
racing heart, the goose bumps, the clamminess, all occur almost before the mind can consciously identify the threat or even see it.
If you already know rattlesnakes, the proximity, and position can in another milisecond add pounding kidneys as the adreneline hits. I haven't had to
kill one for a long time.
In retrospect I always enjoy my encounters (so far) as stimulating and educational.
[Edited on 12-5-2010 by vgabndo]
Undoubtedly, there are people who cannot afford to give the anchor of sanity even the slightest tug. Sam Harris
"The situation is far too dire for pessimism."
Bill Kauth
Carl Sagan said, "We are a way for the cosmos to know itself."
PEACE, LOVE AND FISH TACOS
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Barry A.
Select Nomad
Posts: 10007
Registered: 11-30-2003
Location: Redding, Northern CA
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Mood: optimistic
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I have been bitten 3 times by rattlesnakes, all 3 while on the job-----thank God each time I was wearing high logger-type boots, and they did not
reach my skin. All three times was in high grass in the San Diego back Country. No warning at all-------just bang, they got me.
I don like them sneaky critters-------and adrenalin surges make me deathly ill---always have.
Barry
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Neal Johns
Super Nomad
Posts: 1687
Registered: 10-31-2002
Location: Lytle Creek, CA
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Mood: In love!
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I'm an air down guy, but here is a hot tip from an old miner (now deceased) at Kingston Spring, CA for sandmat users:
Tie a 10 ft. rope to the sandmat from your bumper and drag it as far as necessary to get to a firm spot after the vehicle gets moving.
Don't stop 'til you get to the firm spot!
My motto:
Never let a Dragon pass by without pulling its tail!
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David K
Honored Nomad
Posts: 64859
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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I am trying to visualize that Neal...? Photos please
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Skipjack Joe
Elite Nomad
Posts: 8084
Registered: 7-12-2004
Location: Bahia Asuncion
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Neal,
That reminds me of one of Baron Munchausen's episodes.
Somehow he ends up on horseback sinking in a bog of quicksand with no help in sight. At the last possible moment he grabs his own hair with his right
hand and is able to lift both himself and his horse to safety.
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racheldarlin
Junior Nomad
Posts: 69
Registered: 9-30-2010
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The sand mat is a self recovery tool i.e. helps if you get stuck. I carry them but have never used them except to help someone else get unstuck. I
alway air down when going off paved or well graded road. That is what I meant to say in my original post and I'm sticking to it.
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Geo_Skip
Nomad
Posts: 154
Registered: 5-15-2009
Location: Alta California and......../
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Thanks David K for the pic and story. If the snake was not near your tent...and no threat... release is the honorable act!
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bajalou
Ultra Nomad
Posts: 4459
Registered: 3-11-2004
Location: South of the broder
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Tire Pressure Information
From Extreme 4X4 Trails
Please visit our Sponsor, CLICK on the Banner above
Letting the Hot Air Out of Tire Talk
Tire Pressures for 4-Wheeling
by Harry Lewellyn
Experiences Playing in the Sand
I guess I should cut those reluctant to lower their tires down to sand pressure a little slack. My first time onto the beach in San Felipe, Baja, I
did the air pressure trick, with a little unwillingness, and wasn’t sure it was really necessary. Then, over the next three or four years, I would
first tackle the mellow white stuff at full street pressure and when all my power, skill and finesse failed, I would let ‘em down and move ‘em out.
Me, low range and low gear, would struggle along at a whole five MPH. Deflation they defied resistance as I sailed along in high range, OD, at
whatever speed I chose! Time and again, year after year, I tested the softies with the same undeniable results. Low tire pressure just plain works in
the sand!
What Affects Optimum Sand Tire Pressure
Optimum sand tire pressure is a combination of many things, of which old husband's tales are least productive. However, your tires, their construction
methods and materials, what your car weighs, how it is loaded, and wheel width all play into the sand-pressure tire formula with predictable results.
For this article, I will neglect tire temperature which I suppose could be critical if you test below freezing and play at +80°. Why low pressure
works and how to determine your best sand pressure follows.
Why Low Pressure Works
It’s a simple fact, which some diehards still deny, the bigger the footprint, the softer the stuff you can travel. Mother Nature knows it. Take a look
at the feet of camels, polar bears and marsh birds. They are big and spread out to distribute their weight over a larger surface area. For those who
say skinny, hard tires are better for snow, mud or whatever, please tell me why they don’t use ten-speed bicycle-type tires on snowmobiles? Sand rail
people and mud boggers know big feet work better too! With that out of the way, lets take a look at tire pressure and footprints.
Tire Pressure and Footprints
Right next to your wheel, on the tire, find the small black print that specifies maximum load pressure. For example, my BFGoodrich Radial All-Terrain
T/A 30x9.50R15LTs state 1990 pounds at 50 pounds per square inch (PSI) cold. Most folks, generally including those who install tires, run them up
close to this, and neglect the actual term, "MAX. LOAD" pressure. The street pressure, TREAD FOOTPRINT figure below represents Coyote assessed over
inflation.
Do you really need maximum load pressure?
Consider that standing flat and level (static), loaded the way you normally run is one thing. Now further consider you lose full tread width contact
as the 4X cruises at higher and higher speeds. Centrifugal force tries to increase the diameter of the tread. You only have to look at dragster tires
when they light 'em up to convince yourself of this tire reality. The sidewalls tend to hold the outer edges closer to their static diameter than the
center of the tread and hence the center of the tread spins into an ever increasing diameter with increased speed. In other words, while moving at
highway speeds, the tire is trying to run more on the center of the tread than the edge. That’s why I feel my full width, static contact test
(described below) is conservative. My tire life and wear pattern prove putting more rubber on the ground increases longevity.
Full tread width contact, street pressure
Since this article deals with sand tire pressure, see a back issue of Ecological 4-Wheeling for full details on how to safely determine your exact,
full tread width contact, street pressure. Summarizing Tire Pressure, April, 1990 4-Wheeling, you don’t want to overheat the tire and should only be
able to slip a business card under the outside and inside edges of the tread less than 1/4 inch. Reprints of past 4-Wheeling articles available for
$4.00 each.
Follow along with some arithmetic that scopes in the same results. Four tires times 2000 pounds each (1990 MAX. LOAD rounded up to simplify math)
equals 8000 pounds total (tire) load capacity. My Explorer weighs 4000 (3800 rounded up), or half the maximum capacity of all four tires combined.
That roughly says half the pressure should yield ample load capacity.
As a result of both methods above, I run 26 PSI, night and day, seven days a week, and typically get 60,000 to 80,000 miles out of a set of BFG T/As,
including sand runs at much lower pressure. I trust this information will add practicality to determining your street pressure and encourage you to
accept overall lower tire pressure. No figure is shown for the increase in street pressure footprint, but it should approach full tread width.
Optimum Sand Pressure
To determine your optimum sand pressure, perform the following test on a flat, level and smooth surface, fully loaded as you would be for a sand run
(gas tank and passengers included). Measure the vertical height to the bottom of the wheel (rim) from the ground. This is your 100%, street pressure,
wheel height. Now reduce this height by 25%. In other words, let out air until your wheel is 75% of the street height. Measure and record this
pressure and depending on your vehicle and loading scheme, front and rear tires may differ.
This is your optimum sand pressure. As the TREAD FOOTPRINT figure shows, this typically results in more than a 250% increase. That is like having ten
tires where you only had four. This pressure is only valid for exactly what you tested. Change vehicle, tires, wheels or load and you have to retest.
It’s obvious a vehicle change would dictate retesting. Tires differ in number and stiffness of sidewall plys and rubber compounds, hence the need to
retest with a tire change, and in actuality, tire age/wear too. Wider or narrower wheels influence how the sidewalls bulge, so this too requires doing
the deed anew.
How did I measure the 250% increase? I measured the pressure, painted the tread, let the tire down onto a piece of paper and “printed” the footprint
for various air pressures. I could see the edge begin to make contact and footprint increase with ever-decreasing pressure.
The results are dramatic, but carefully observe the PRESSURE-HEIGHT CURVE, and understand this is not a universally applicable curve. It is specific
to my 4X, tires, wheels and load. Wheel height and footprint are obviously related. Putting the curve into words, the footprint really starts to
increase (wheel height decrease) with the last few drops in PSI. Note I measured no height change from 50 to 37 PSI. From 50 to 20 PSI resulted in
only 3/8 inch drop in height. The drop from 20 to 12 PSI was about 1/2 inch and the drop from 12 to 7 PSI yielded more than 3/4 inch drop in height.
These last few pounds are where the real effect takes place. Give them pudgy cheeks!
I’ve had people tell me the low pressure trick does not work. "I went down to 16 or 18 PSI and still had trouble in the sand," so the claim goes. It
should be apparent from the curve, the last few pounds really count! A good indicator other than ease of movement comes by watching your engine
temperature gauge. If you are heating up, your pressure is still too high or you’re really in some tough stuff!
So does this mean flat tires are best? I believe not. Again the 75% rule is somewhat tire and wheel dependent, but at too low tire pressure, the
center of the footprint begins to well up, reducing the footprint and creating a small “traveling hill” in the center of the footprint. This hill
offers increased resistance to vehicle movement.
For my combination of 4X, tires, etcetera, my optimum sand pressure is six to seven PSI and I typically get by with eight to ten.
Tire Gages
The Great American Big Numbers Misconception
Before we move on, let's talk pressure measurement - tire gauges. I’ll leave the type - stick, dial or digital - up to you and a future article in
4-Wheeling. What I’m primarily addressing is the Great American Big Numbers Misconception; the bigger the number, the better it is.
As a kid, I remember one of my first automotive questions was, "What does the speedometer go up to?" Not how fast does the car go, but how big is the
number at the end. This end number on both speedometers and pressure gauges has little, and sometimes a negative bearing, on gauge usefulness.
Actually, I have quite a few tire gauges. Several fell prey to the Great Numbers Misconception. I carry and use two. One for everyday street use and
another for low pressure. My street pressure gauge goes to 50 PSI and my low pressure gauge goes to 20. It’s pretty hard to measure 10 PSI on a gauge
that starts at 20 PSI. Most 120 to 200 PSI gauges don’t even start until 20 or more. These are useless for sand pressure measurements. Don’t waste
your money on high pressure gauges! Consider having two and perform the above tests and field air-down measurements with the same low pressure gauge.
The exact accuracy of the reading or value is not as important as repeatability.
And something to plan for is the eventuality of no gauge or a failure. This is easily handled by knowing how long it takes to air down from street to
sand pressure. I use the one-thousand-one, one-thousand-two, second counting method. I can let 50 seconds worth of air out of my tires before I need
to take a reading. It’s usually another ten more seconds before I reach my optimum. Given a gauge failure, I will still stand a fair chance at
"bringing ‘em back alive" - me, the car and the tires.
Four Affects of Low Tire Pressure
Low tire pressure changes four things: footprint; ground clearance; rolling radius and what I call Obstacle Rolling Resistance. Footprint was covered
above. Common sense and the TREAD FOOTPRINT figure shows the center of the axle is lowered by the decrease in wheel height. This results in lower
ground clearance and consider the softer tires also flex and give more resulting in compression loss of ground clearance too. But on the other hand,
ground clearance is not that important in the sand.
Rolling radius is part of the equation which contributes to your net moving force; your overall gear ratio; your "stump pullin’ power". See December
1988, Ecological 4-Wheeling, for a complete treatment of net moving force. Think of it this way: you know how bigger tires eat up low gearing and
smaller tires effectively give you lower gears? Flatter tires act like smaller tires and increase your pulling (moving) power.
OBSTACLE ROLLING RESISTANCE
Move on to the OBSTACLE ROLLING RESISTANCE figure below to learn how significant this sleeper is! Several years back, I was convinced a tire’s ability
to conform to obstacles played a big part in ease of movement, but I had no idea how significant it was until I measured it. Here’s my experiment.
Face-off two 4Xs some 30 feet apart, on a flat, smooth surface. Take the winch of one and connect it to the other, with a dynamometer (a big fish
scale) in the cable. Put a pair of 2X4 wood blocks in front of the pulled vehicle and measure the force (pull) required for different towed vehicle
tire pressures.
A simple, lowly 2X4 offers more of a climb angle (hill) than you might initially think. It is roughly 25° to 30°. Knowing this, it’s now easy to see
why not so big rocks require the thrash and bash technique to climb with hard tires.
The 2X4 tests showed a 40% difference between street and sand pressure! And it may be worse than that because the initial burst of pull required to
get the street pressure tires started up over the obstacles (the 2X4s) was not precisely recordable with my crude equipment and test methods. With the
sand tire-pressure, it was obvious the dynamometer saw a gradual buildup in force as the tires smoothly conformed and crawled over the obstacles. What
this 40% difference means is you now have roughly six tires where you only had four. Add this to the "ten tires" of the pressure drop and you now have
16 where you had four. Any more questions about the effectiveness of lowering tire pressure?
There is a lot more to making this test perfect and I would be most happy to redo it using proper equipment and controls. Anyone have access to strain
gauge cells and strip chart recorders?
Rock Crawling
Actually, I suspect this is also why lower tire pressure is very effective for rock crawling. The Obstacle Rolling Resistance factor, as I call it,
plays an even more crucial role when rolling through the rocks.
Caution!
Now comes the soap box. Use Caution! Caution! Caution! with low tire pressure. The Obstacle Rolling Resistance factor works against you with speed and
in the rocks! Soft tires easily bend and break wheels. Drive with caution when back on hard ground or the rocks! And you obviously need some way to
reinflate the tires back to street pressure when you hit the black stuff.
Even in 2WD
You 2-wheelers take note as well, for this trick works equally well in 2WD. But remember, you must still deflate all four tires even though you are
only putting power to two. Your hard front tires create hills that your rears must continually try to climb.
Treading Lightly
I also feel lower pressure is more ecologically compatible. With better traction you don’t have to spin the tires and hence leave Mother Nature
unscathed.
You’ll be doing yourself and Mother Nature a favor when you lower your tire pressure the next time you hit the soft stuff.
© Harry Lewellyn
Ecological 4-Wheeling Adventures
P.O. Box 12137
Costa Mesa, CA 92627
voice: (949) 645-7733
fax: (949) 645-7738
email: info@eco4wd.com
This method hasn't ever failed me.
No Bad Days
\"Never argue with an idiot. People watching may not be able to tell the difference\"
\"The trouble with doing nothing is - how do I know when I\'m done?\"
Nomad Baja Interactive map
And in the San Felipe area - check out Valle Chico area
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David K
Honored Nomad
Posts: 64859
Registered: 8-30-2002
Location: San Diego County
Member Is Offline
Mood: Have Baja Fever
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Thanks for posting that Lou... Harry has some good things in his books... He was at VivaBaja #3.
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