Date: Wed, 20 Oct 1999 22:06:54 4
From: "skimmer"
Subject: [Paddlewise] Kayak Radar visibility

A group of us once paddled in heavy fog among islands on the coast of 
Maine.  A Coast Guard boat loomed up from the mist and suggested we 
stay out of the channel.  They said we were only barely detectable 
with their hotshot radar, and would likely be entirely undetectable 
by average marine radar systems on private yachts. We encountered 
this patrol in an area of dead flat calm water.  We were not 
"obscured by waves".   We were studying navigation at the time.

I recently received a request for information about making kayaks 
detectable on radar.  

I don't have a useful response.  On those occasions that we paddled 
in heavy fog (visibility 100 yards), we stayed in a tight group, 
listened for other boats, sounded horns upon hearing other boats, 
heard their horns in reply, and listened as they veared around us. We 
never saw them.  We stayed out of boating channels except to cross, 
and crossed rapidly when we heard no traffic.  We mostly avoided 
traffic in this way.

Can anyone provide  some useful advice or experience on making 
sea kayaks visible to radar when paddling in heavy fog ?

Thanks,
Chuck Sutherland




Date: Thu, 21 Oct 1999 09:54:20 EDT
From: JCMARTIN43@aol.com
Subject: Re: [Paddlewise] Kayak Radar visibility 

Chuck Sutherland wrote, "A group of us once paddled in heavy fog among islands 
on the coast of Maine.  A Coast Guard boat loomed up from the mist and suggested 
we stay out of the channel.  They said we were only barely detectable with 
their hotshot radar, and would likely be entirely undetectable by average 
marine radar systems on private yachts. We encountered this patrol in an area 
of dead flat calm water."  Chuck has asked about ideas on radar visibility for 
kayaks.

We have bounced this subject around before on PW, and there was a pretty 
comprehensive article done in Sea Kayaker a while back --- don't have the 
date --- which, from memory, indicated that there were no viable means to 
enhance a kayak hull's radar cross-section, its radar visibility to an oncoming 
ship; however, there are commercial metal or metalized foam three dimensional 
radar reflectors available at boating supply stores (~$15-20) which, if mounted 
on a nominal four to six foot mast on the after deck of the kayak, will provide 
some enhanced passive visibility for a kayak.  (All this assumes that an 
oncoming vessel operator is (1) looking at his scope, and (2) is seriously 
concerned about a very small blip on his screen --- the argument being that he 
may be far more concerned about a blip indicating the presence of something 
bigger and meaner than himself --- like Nova Scotia or something.  But that's a 
different thread.)

An option to this for deep-pocketed kayakers --- or maybe trip operators or 
instructors with insurance concerns --- is a Search and Rescue Transponder 
(SART).  SARTs basically monitor radar frequencies and, when they are swept by a
radar signal, answer back to that radar transmitter that there's something 
there.  You will not resemble a Canadian province, but you will certainly 
indicate your presence to the oncoming vessel.  Re the "deep pockets" issue: 
a SART is going to run between $1200 and $1500 (US).

A cheaper option is one of the inflatable assistance widgets sited in Sea 
Kayaker in April 1998, the Sea Bouy (see www.seakayakermag.com/apr98/inflatdev.htm).  
This is a diver's device which inflates into a four foot international orange 
cylinder with retroreflective tape at the top and a radar reflective element in 
the top.  Mounted to a kayak's rear deck, this widget could provide a quick 
inflating "mast" and some passive radar protection (said to provide a one mile 
indication in an independent boating magazine's test).  The price tag on this 
guy is somewhere around $100 (from memory).  Again, the oncoming vessel has to 
be looking and concerned --- both big assumptions.  (And this doesn't even 
address the idea of recovering the kayak from a knock-down with a six foot mast 
or a four foot inflatable cylinder above your after deck!  Other serious safety 
issues here.)

Bottom line: I have used boat store radar reflectors in nighttime tests of 
search and rescue (SAR) equipment in open ocean scenarios in the past; mounted 
to a bouy at a nominal three foot height above water level in two to three foot 
seas, these things were marginally effective inside a one mile radius --- and we 
were definitely watching for them on the vessel's radar because they were 
attached to several thousand dollars worth of equipment which we wanted to 
recover at the end of the evening!  My guess is that passive radar reflectors at 
heights above water which a kayak could conceivably provide would be, at best, 
marginal.  Better than nothing?  Sure.  Good if the Coast Guard is out there 
actively searching for you?  Definitely.  Valuable to a kayaker skirting or 
crossing a channel in fog?  Dunno --- wouldn't bet my life on it.  Better bet?  
A SART for the instructor's boat, keeping the flotilla in close formation.  
Best bet?  Stay out of the fog altogether.

My somewhat more than two cents.

Jack



Date: Thu, 21 Oct 1999 10:21:06 -0700
From: rdiaz@ix.netcom.com
Subject: Re: [Paddlewise] Kayak Radar visibility

Let's face it, you are duck soup in fog.  You're best staying off the
water in trafficked areas in fog, period.  Even if this means adjusting
your schedule to wait out the fog.  If it descends on you while on open
water, get to anything you can that is solid such as some rocks or a
bouy and stay there til things clear even if it takes half a day.

One of my scariest times ever on the water was on an Albany to NY Hudson
River trip on the day at mid-point where we started off one early
morning in such thick fog that we could hardly see 3 feet past our bow. 
Going down river, we constantly bumped into the shore on each side like
a ball in a pinball machine, so blind were we.  I kept expecting some
cement barge and tug from the factories near Cementtown NY to run us
down in this early morning fog.  In hindsight, we should have stayed at
our campsite, drank more coffee, worked on knot-tying etc. and waited
for the thing to lift a bit.

Forget about reflectors, etc.; they won't work for all the reasons
stated by Jack, most particularly that they make such a some blip on a
radar screen that only the most microscopic-eyed operator would spot
it...most like it would be dismissed as a quark in the system.

ralph diaz
- -- 
- -----------------------------------------------------------------------
Ralph Diaz . . . Folding Kayaker newsletter
PO Box 0754, New York, NY 10024
Tel: 212-724-5069; E-mail: rdiaz@ix.netcom.com
"Where's your sea kayak?"----"It's in the bag."
- -----------------------------------------------------------------------




Date: Fri, 22 Oct 1999 10:22:21 +0100
From: "Colin Calder"
Subject: [Paddlewise] Kayak Radar visibility  


Jack Martin wrote some interesting stuff about radar reflectors.

There have been a series of articles on the subject recently in Practical Boat
Owner magazine. During the course of the articles a number of commercial passive
reflectors were tested on a sailing yacht for radar visibility from a large
commercial power vessel - the conclusions as far as I recall were that these
passive reflectors at best made virtually no improvement to the radar reflection
of the yacht, and in several cases actually reduced the reflection. This caused
some consternation, and the reflectors were taken to a military radar test
facility, where it was found that in certain circumstances they could cause
interference which cancelled radar reflections from the yacht itself!

I would guess that if a reflector up a 50ft mast doesn't help, its not going to do
much on a kayak/paddler which is completely (at least from sea level) obscured
when  sitting in the trough of waves bigger than say 3-4 ft. Stealth kayak! -  I
would assume that you are invisible to the eyes and radar (if anyone is actually
looking at it) of other craft.

I personally don't have much concern about being run down by commercial vessels
(kayaks are pretty much the only craft which tend/are capable of nosing around/in
the local sea cliffs where I do maybe 90% of my paddling). However, I wonder
whether some sort of active transponder would give kayaks a noticeable radar
signature. As a research student I spent some time at a wildlife field station
radio tracking deer. At this time (~1990) active radar transponders were being
tested for wildlife telemetry/tracking. Units were fitted to pink footed geese.
Geese obviously swan (sic) around somewhat higher above the water than kayaks (at
least those which aren't equipped by inflatable crotch dirigibles) but as far as I
remember you could follow geese fitted with transponders around quite effectively
(at least when they were airborne) over the range of a standard marine radar
outfit. GPS/satellite transponders came on the scene about the same time for
wildlife telemetry and I haven't heard anything more about the use of radar, but
the units were obviously relatively small and light if they could be carried by
birds (I assume <5% of the body weight of a goose)- presumably because most of the
weight would be the battery, which can be relatively small because the unit only
transmits when it receives incoming radar.

This may have already been tried on kayaks/boats, I don't know, but food for
thought.

Cheers

Colin Calder
57º19'N  2º10'W



Date: Fri, 22 Oct 1999 07:45:11 -0700
From: Dan Hagen
Subject: Re: [Paddlewise] Kayak Radar visibility

Pains Wessex makes a relatively compact marine radar transponder:

http://www.pwss.com/products/xponders/rte.htm

However it is very expensive, and while relatively compact, it is still
a bit larger than is desirable for use on a kayak. Given this, and given
that I paddle mainly in areas where larger boats fear to tread, I have
not been tempted to buy one. But if I paddled in New York I might be
tempted, given some of Ralph's stories of heavy ship traffic (and
mystery barges) rumbling about in the fog.

Dan Hagen




Date: Fri, 22 Oct 1999 09:24:17 PDT
From: "Philip Torrens"
Subject: Re: [Paddlewise] Kayak Radar visibility

The unit itself looks relatively compact, but the reference to leads 
strongly suggests it is not self-contained, but runs off your 12-volt marine 
battery (as found in every kayak:-) . I'd be worried about running down my 
battery and not having enough juice for the Rule 500 pump and the drinks 
blender...

Philip Torrens
N49°16' W123°06'




Date: Fri, 22 Oct 1999 12:25:25 -0800
From: "Rev. Bob Carter"
Subject: [Paddlewise] radar

    An important point about being visible on radar.

    Even if a ship has "the best radar" and your kayak is made entirely of
radar reflecting material the main safety factor is whether or not the ship's
crew  is paying attention to the radar. Obviously the crew of the Exxon Valdez
was not! Bligh reef was marked and visilble on radar.

    Last summer here in southeast alaska the ferry LeConte (200') almost
collided in the fog with a small cruise ship. Both ships had radar!  They
missed by 50'!

    Also I have often seen fishermen in southeast working the back of the boat
where the fishing gear is and they only occasionally look forward to see if
they are still on course. The radar could be showing a dozen kayaks and they
would not notice. 

    Also some of the bigger ships in narrow passages have little or no room to
manuvover and it takes miles for them to stop!

    So I always assume they are unaware of my presence and it is up to me to
stay out of their way.

Happy boating

Bob

sitka



Date: Fri, 22 Oct 1999 14:44:15 -0700
From: Jerry Hawkins
Subject: Re: [Paddlewise] radar

Regarding radar (again),

It isn't the really huge ships one should worry about, in that (as all agree) 
there is zero possibility of making them see you, and frankly they won't stop 
or maneuver around you anyway.  Stay out of their way.  It isn't hard to stay 
out of the main shipping lanes in most areas.  It is the medium and small guys 
that behave erratically.  Those people may have their radar turned off, even in 
fog, or have no experience or training.  For the 30' fishing boats and cabin 
cruisers and sailboats, you just might be visible on radar, under best of 
circumstances, but this will never be reliable.  Whether you are canoeing, 
kayaking, or even in a small to medium motorboat, the best advice is to assume 
they don't see you, don't have radar, and may have been drinking.  There was a 
major collision in the English Channel in August -- two experienced captains, 
large commercial boats, radar, GPS, and damn if they didn't hit each other 
anyhow.  A freighter out of San Francisco hit a large fishing boat called the 
Jack Junior a few years back, caught its nets, dragged it underwater, and no 
trace was found for months.  You just have to minimize time spent in the 
shipping lanes, know you are invisible, and work from there.

jerry.