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From: Doug Lloyd <douglloyd_at_shaw.ca>
subject: Re: [Paddlewise] pressurize the boat
Date: Mon, 02 Apr 2007 13:58:09 -0700
I use an old Valley 7" hatch that was still serviceable but not ideal for 
continued use, then silicone in a tire fill valve. I use compressed air from 
a compressor (don't over do it, though my Nordkapp would blow the hatch 
before anything else due to its reinforced nature). Use soapy dishsoap 
liquid and water mixed, and brush it on. Bubbles are easily observed if 
present. Don't make the soap to runny with water. Tire stores do something 
similar if they don't have a dunk tank for testing tire mounting and 
repairs. Some kayaks, like those with plastic "H" seams, sometimes can be 
difficult to track down the leak if the air is migrated away.

I can't fathom (pardon the pun) even remotely why an experienced paddler 
would venture off into potentially heavy seas trusting only the reputation 
of the manufacturer, though I'm sure 99% do that. I've witnessed and heard 
first and second  hand boat leak stories. I think it is one of the few 
things that I find really upsetting to me to undergo while sea kayaking. 
I've had a breached hull myself while winter storm paddling on the remote 
shores of Vancouver Island and in-season touring, and once even spit my 
seams in storm-tossed logs. I much prefer to minimize the occurrence of 
these types of incidents (ergo my reinforced hull, seams, and testing 
regime).

I've heard of filling your kayak (very partially) with colored water, then 
testing for leaks breaching through. Admittedly, I'm pretty anal about this 
kind of stuff. It's a matter of taking responsibility for yourself. With a 
home made boat, I'd be just as rigorous, if not more so. I don't know what 
the building forums suggest. My method was adopted after a local kayak 
retailer showed me how he tested hid boats (all British heavies with he 
rubber hatches). Well, your YSMV (your sinkage may vary).

BTW, I doubt the wave height were as the reporter described. Most media 
reporting add an exaggerating factor. I always prefer authors and reporters 
to downgrade to as close as possible the real wave heights/wind velocity. It 
doesn't take much to cause an upset, test gear and boat to the maximum, and 
drain paddling energies. Readers looking for relevance need to hear the real 
facts so as to provide a realistic appraisal for their own yardsticks.

Doug Lloyd
Victoria BC



> Doug
> How do you pressurize your boat so you can look for leak?  I am putting 
> the finishing touches of a Gillemot Double and the leaks are a concern.
> Thanks in advance
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From: Craig Jungers <crjungers_at_gmail.com>
subject: Re: [Paddlewise] pressurize the boat
Date: Mon, 2 Apr 2007 18:00:38 -0700
On 4/2/07, Doug Lloyd <douglloyd_at_shaw.ca> wrote:
>
>
> BTW, I doubt the wave height were as the reporter described. Most media
> reporting add an exaggerating factor. I always prefer authors and
> reporters
> to downgrade to as close as possible the real wave heights/wind velocity.


I believe almost everyone overestimates wave height but not on purpose. Part
of the reason is that one seldom has a level platform from which to make the
estimate. One's platform is usually tipping one way or the other. If your
bow is headed for the trough of a wave and you look at the top of the
approaching crest it appears higher because the angle of your head is
farther up due to the bow of the kayak pointing down to the trough. This
increased angle causes most of us to think that the approaching wave is
higher than if you were level looking up at a normal angle.

And there is always the pucker factor.


Craig Jungers
Royal City, WA
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From: Doug Lloyd <douglloyd_at_shaw.ca>
subject: Re: [Paddlewise] pressurize the boat
Date: Mon, 02 Apr 2007 19:01:59 -0700
A skilled paddler should be able to estimate wave height and wind speeds 
reasonably accurately. The two kayakers were supposed to be fairly advanced, 
though 8 years of paddling experience may or may not have provided the 
necessary accumulation of attributes. I guess my real point was the media 
seem responsible for inflating wave heights - usually. Don't ask me how I 
know.

Your points were taken under good advisement, however. Glad we have 
experienced mariners on this list.

Doug L


> On 4/2/07, Doug Lloyd <douglloyd_at_shaw.ca> wrote:
>>
>>
>> BTW, I doubt the wave height were as the reporter described. Most media
>> reporting add an exaggerating factor. I always prefer authors and
>> reporters
>> to downgrade to as close as possible the real wave heights/wind velocity.
>
>
> I believe almost everyone overestimates wave height but not on purpose. 
> Part
> of the reason is that one seldom has a level platform from which to make 
> the
> estimate. One's platform is usually tipping one way or the other. If your
> bow is headed for the trough of a wave and you look at the top of the
> approaching crest it appears higher because the angle of your head is
> farther up due to the bow of the kayak pointing down to the trough. This
> increased angle causes most of us to think that the approaching wave is
> higher than if you were level looking up at a normal angle.
>
> And there is always the pucker factor.
>
>
> Craig Jungers
> Royal City, WA
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From: Dave Kruger <kdruger_at_pacifier.com>
subject: Re: [Paddlewise] pressurize the boat
Date: Mon, 02 Apr 2007 19:32:44 -0700
Doug Lloyd wrote:
> A skilled paddler should be able to estimate wave height and wind speeds 
> reasonably accurately. The two kayakers were supposed to be fairly 
> advanced, though 8 years of paddling experience may or may not have 
> provided the necessary accumulation of attributes. I guess my real point 
> was the media seem responsible for inflating wave heights - usually. 
> Don't ask me how I know.

Basically, I agree with Doug.  However ...

I think 80% of the folks I have paddled with over the years grossly 
overestimate wave height, when they are out in it ... typically by a factor 
of two.  Most folks are not very good observers, unless they have trained 
themselves and checked their estimates.  Having reporters repeat what 
paddlers say makes even for more error.

OTOH, if the writer of the article had quoted a figure from a NOAA or 
EnvironmentCanada buoy ... than I'd believe they were more accurate.

-- 
Dave Kruger
Astoria, OR
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From: Doug Lloyd <douglloyd_at_shaw.ca>
subject: Re: [Paddlewise] pressurize the boat
Date: Mon, 02 Apr 2007 20:36:13 -0700
Good points Dave, as always.

Of course, if you are in three foot waves, and you are down in the trough 
three feet looking up at the crest of either a shore break or a steep wind 
wave, it does appear to be a 6 foot wall of water coming down on you. Your 
factor of two. Nick's explanation helps:

http://www.paddlinginstructor.com/articles/determining_wave_height_in_rough_water_20060401.php

Usually, I determine wave height from simple exposure over the years of 
comparing observed height estimations with reported heights. But say, if a 
paddler doubles their estimate and then a newspaper reported factors in 
another doubling, well, it doesn't take long to have 20 foot seas on the 
Great Lakes at half the needed 60 knots to really generate those seas. On 
the other hand, most of us estimate the wave height correctly, then add 
another three feet when telling friends about our little adventure. Add 
another three feet to that if you are drinking at the pub with those same 
friends or there are women listening. The latter is usually when most guys 
lie about size. :-)

Well, it's just about tax time here in Canada. Kayaking is like taxes, you 
can make it as dangerous as you want.

DL

> Doug Lloyd wrote:
>> A skilled paddler should be able to estimate wave height and wind speeds 
>> reasonably accurately. The two kayakers were supposed to be fairly 
>> advanced, though 8 years of paddling experience may or may not have 
>> provided the necessary accumulation of attributes. I guess my real point 
>> was the media seem responsible for inflating wave heights - usually. 
>> Don't ask me how I know.
>
> Basically, I agree with Doug.  However ...
>
> I think 80% of the folks I have paddled with over the years grossly 
> overestimate wave height, when they are out in it ... typically by a 
> factor of two.  Most folks are not very good observers, unless they have 
> trained themselves and checked their estimates.  Having reporters repeat 
> what paddlers say makes even for more error.
>
> OTOH, if the writer of the article had quoted a figure from a NOAA or 
> EnvironmentCanada buoy ... than I'd believe they were more accurate.
>
> -- 
> Dave Kruger
> Astoria, OR
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From: mike dziobak <mdziobak_at_mtu.edu>
subject: Re: [Paddlewise] more like "wave heights" but was pressurize the boat
Date: Tue, 3 Apr 2007 21:04:49 -0400 (EDT)
Doug wrote:
....snip
> paddler doubles their estimate and then a newspaper reported factors in
> another doubling, well, it doesn't take long to have 20 foot seas on the
> Great Lakes at half the needed 60 knots to really generate those seas. On
....snip

Check out this forecast for the inshore waters south shore Lake Superior:

NATIONAL WEATHER SERVICE MARQUETTE MI
533 PM EDT TUE APR 3 2007
FOR WATERS WITHIN FIVE NAUTICAL MILES OF SHORE
LSZ241-242-040600-

UPPER ENTRANCE OF PORTAGE CANAL TO MANITOU ISLAND MI-
533 PM EDT TUE APR 3 2007
...SMALL CRAFT ADVISORY NOW IN EFFECT UNTIL 8 PM EDT THIS
EVENING...
...GALE WARNING NOW IN EFFECT FROM 8 PM EDT THIS EVENING THROUGH
THURSDAY AFTERNOON...
.TONIGHT...NE WIND TO 30 KT INCREASING TO GALES TO 35 KT BY
MIDNIGHT...THEN BACKING N LATE. SNOW. WAVES 4 TO 6 FT BUILDING TO
15 TO 20 FT.
.WED...N GALES TO 40 KT. SNOW SHOWERS. WAVES BUILDING TO 20 TO 25
FT.
.WED NIGHT...NW GALES TO 35 KT. SNOW SHOWERS. WAVES 20 TO 25 FT.

I can't find my wind speed/wave height tables but is this even possible
with only 40 kt gales? I won't be out there in my kayak but I'll be
looking for a protected cove with my surfboard.
-mike
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From: Dave Kruger <kdruger_at_pacifier.com>
subject: Re: [Paddlewise] more like "wave heights" but was pressurize the boat
Date: Tue, 03 Apr 2007 18:57:11 -0700
mike dziobak wrote:

> Check out this forecast for the inshore waters south shore Lake
> Superior:

> NATIONAL WEATHER SERVICE MARQUETTE MI 533 PM EDT TUE APR 3 2007 FOR
> WATERS WITHIN FIVE NAUTICAL MILES OF SHORE LSZ241-242-040600- .WED...N
> GALES TO 40 KT. SNOW SHOWERS. WAVES BUILDING TO 20 TO 25 FT. .WED
> NIGHT...NW GALES TO 35 KT. SNOW SHOWERS. WAVES 20 TO 25 FT.

> I can't find my wind speed/wave height tables but is this even possible 
> with only 40 kt gales?

Yes.  With sufficient fetch, the "observed average" produced by a sustained 
35 knot gale runs about 20 ft [Bascom; Waves and Beaches; 1980 version; 
page 48].  I suspect the "observed average" relates closely to the 
"significant wave height" figure given by the buoy reports.

-- 
Dave Kruger
Astoria, OR
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From: mike dziobak <mdziobak_at_mtu.edu>
subject: Re: [Paddlewise] more like "wave heights" but was pressurize the boat
Date: Tue, 3 Apr 2007 22:04:52 -0400 (EDT)
That's what puzzles me here, the north fetch on the Keweenaw is only about
40 nmi because of Isle Royale and it goes to about 60 on one side of IR to
about double that on the other side. I did notice that the open lake WX is
gales up to 50 kt. But I'm not used to seeing such large wave magnitudes
for the in shore even at those wind speeds. The weather map doesn't look
very special either.
-mike

> mike dziobak wrote:
>
>> Check out this forecast for the inshore waters south shore Lake
>> Superior:
>
>> NATIONAL WEATHER SERVICE MARQUETTE MI 533 PM EDT TUE APR 3 2007 FOR
>> WATERS WITHIN FIVE NAUTICAL MILES OF SHORE LSZ241-242-040600- .WED...N
>> GALES TO 40 KT. SNOW SHOWERS. WAVES BUILDING TO 20 TO 25 FT. .WED
>> NIGHT...NW GALES TO 35 KT. SNOW SHOWERS. WAVES 20 TO 25 FT.
>
>> I can't find my wind speed/wave height tables but is this even possible
>> with only 40 kt gales?
>
> Yes.  With sufficient fetch, the "observed average" produced by a
> sustained
> 35 knot gale runs about 20 ft [Bascom; Waves and Beaches; 1980 version;
> page 48].  I suspect the "observed average" relates closely to the
> "significant wave height" figure given by the buoy reports.
>
> --
> Dave Kruger
> Astoria, OR
>


-- 
mike Dziobak
Dept of Civil and Environmental Engineering
Michigan Technological University
1400 Townsend Dr.
870 Dow Bldg.
Houghton, MI 49931
 Tel:906-487-3471
Fax:906-487-2943
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From: Phil Baus <philnlynn_at_comcast.net>
subject: Re: [Paddlewise] pressurize the boat
Date: Mon, 2 Apr 2007 12:44:20 -0700
[Please remove all old content that is not pertinent to your reply
including old headers and footers.  It's list policy.... 
this post was modified to meet policy]

From: "Doug Lloyd" <douglloyd_at_shaw.ca>
> Agreed Craig - very well written. I like to do a leak test on my kayak at 
> least once a year with mild air pressure and a soap solution (bubbles form 
> if there are leaks). Boat leaks, boat no float, boat no good. It's a 
> simple mantra. Anyway, I'm sticking with my small hatches.

Doug
How do you pressurize your boat so you can look for leak?  I am putting the 
finishing touches of a Gillemot Double and the leaks are a concern.
Thanks in advance

Phil Baus
Vancouver, USA
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From: <Rcgibbert_at_aol.com>
subject: Re: [Paddlewise] pressurize the boat
Date: Tue, 3 Apr 2007 11:15:32 EDT
In a message dated 4/2/2007 6:03:53 PM Pacific Daylight Time,  
crjungers_at_gmail.com writes:

I  believe almost everyone overestimates wave height but not on purpose.  Part
of the reason is that one seldom has a level platform from which to  make the
estimate. One's platform is usually tipping one way or the other.  If your
bow is headed for the trough of a wave and you look at the top of  the
approaching crest it appears higher because the angle of your head  is
farther up due to the bow of the kayak pointing down to the trough.  This
increased angle causes most of us to think that the approaching wave  is
higher than if you were level looking up at a normal angle.

And  there is always the pucker factor.



>>>>>>>>>>>>>>>>>>>>>>>>>
 
Buoy reports are your friend. 
 
Cheers,
 
Rob G



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From: mike dziobak <mdziobak_at_mtu.edu>
subject: Re: [Paddlewise] wave heights, was pressurize the boat
Date: Tue, 3 Apr 2007 20:26:14 -0400 (EDT)
Ah, but the bouy report is significant wave height which is average of the
top third largest waves. So on the lake at least, from my experience, it
might be possible to see an occasional wave twice the size of the bouy
report. I say it might be because i am never very sure of my wave height
estimate from the seat of a kayak. While surf boarding and sail boarding,
I think my estimates are better.
-mike

>>>>>>>>>>>>>>>>>>>>>>>>>>
>
> Buoy reports are your friend.
>
> Cheers,
>
> Rob G
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From: <Rcgibbert_at_aol.com>
subject: Re: [Paddlewise] wave heights, was pressurize the boat
Date: Tue, 3 Apr 2007 21:30:54 EDT
In a message dated 4/3/2007 5:26:24 PM Pacific Daylight Time,  
mdziobak_at_mtu.edu writes:

Ah, but  the bouy report is significant wave height which is average of the
top  third largest waves. So on the lake at least, from my experience, it
might  be possible to see an occasional wave twice the size of the bouy
report. I  say it might be because i am never very sure of my wave height
estimate  from the seat of a kayak. While surf boarding and sail boarding,
I think my  estimates are better.
-mike



>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
 
Hi Mike (and all),
 
Buoy reports tell you what went on in the area of the buoy. The further you  
stray from there, the more talent at elocution you may apply to what you saw.  
However, a buddy said, we were in 8-10 foot seas!!! Later, I looked at the 
buoy  report several miles away, it said the seas there were 5 feet. Perhaps, 
and a  big perhaps, he saw a couple corporate swell mergers, a bit of clapotis 
or  current enhancing for a while a 5 foot swell and with pucker factor adding 
in  another embellishment made them out to be 8-10 feet. What I saw was 
typical 5  foot swell, enough to bury a paddler whose upright paddle blade 
disappears  from view momentarily. Honest to God 5 footers, honest to God 2.5 footers. 
Once  in a blue moon, maybe a 6 due to some feature, but who knows, maybe I 
was too  close to it and made it up.
 
Cheers,
 
Rob G
 
 
 
 



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From: <Rcgibbert_at_aol.com>
subject: Re: [Paddlewise] pressurize the boat
Date: Tue, 3 Apr 2007 11:24:40 EDT
In a message dated 4/2/2007 7:35:22 PM Pacific Daylight Time,  
kdruger_at_pacifier.com writes:

OTOH, if  the writer of the article had quoted a figure from a NOAA or  
EnvironmentCanada buoy ... than I'd believe they were more  accurate.



>>>>>>>>>>>>>>>>>>>>
 
Dave,
 
a couple of pairs of surf skiers got into trouble las fall up by  Bellingham, 
WA. One pair was whisked aboard a coast guard chopper. The news film  made 
the blog rounds. They said the waves went up to 10 feet. The closest buoy  was 
about 10 miles away on south San Juan Island, in a much more exposed area to  
the fetch, it reported waves up to 5.9 feet. Like Craig said, pucker factor,  
works every time.
 
Cheers,
 
Rob G



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From: Doug Lloyd <douglloyd_at_shaw.ca>
subject: Re: [Paddlewise] pressurize the boat
Date: Tue, 03 Apr 2007 12:40:00 -0700
FOLLOW UP POST - Try the Southwind site for some _great information_:

http://www.southwindkayaks.com/library/survivalskills.html

No affiliation

dl

> Doug
> How do you pressurize your boat so you can look for leak?  I am putting 
> the finishing touches of a Gillemot Double and the leaks are a concern.
> Thanks in advance
>
> Phil Baus
> Vancouver, USA
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From: Michael Daly <mikedaly_at_magma.ca>
subject: Re: [Paddlewise] pressurize the boat
Date: Tue, 03 Apr 2007 16:24:29 -0400
Doug Lloyd wrote:
> FOLLOW UP POST - Try the Southwind site for some _great information_:

One problem with that info is that it assumes all bulkheads are 
perfectly watertight.  Many kayaks have a teensy hole in the centre to 
allow for air pressure equalization.  I put one in both front and rear 
bulkheads after seeing the hatch covers bulging (Kayaksport rubber).  No 
amount of rolling or other wet practice has ever resulted in anything 
other than a bit of dampness in the compartment.

If you're really paranoid about leaks, Doug, you're gonna have a lot of 
fun with an SOF.  What with sewing seams making holes in the fabric that 
are sometimes too large (just) to completely close with paint or 
varnish, you're gonna have to decide whether you want a bit of a leak or 
go crazy finding and filling every possible hole.  Since the reserve 
buoyancy in an SOF comes from flotation bags and not the skin's 
integrity, it's really a moot point, IMHO.

With composite kayaks, I think you have to differentiate between a leak 
that constitutes a leak and one that constitutes a potential structural 
failure.  The small one of the former is annoying, a large one or the 
latter, dangerous.

Mike
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From: Robert Livingston <bearboat2_at_comcast.net>
subject: Re: [Paddlewise] pressurize the boat
Date: Tue, 3 Apr 2007 16:55:43 -0700
One factor involved in leakage into a bow or stern compartment is  
pressure differences. This does not arise in a skin boat or any kayak  
without bulkheads but can have a profound effect in bulkheaded  
composite boats where a small leak that in and off itself might be of  
no particular significance can admit a large amount of water.

If the leak is small (as are the small drill holes that people place  
in their bulkheads) the pressure in the compartments is rarely the  
same as the outside when you are paddling in rough water. There is a  
certain about of flex in the hull (even in heavily constructed boats)  
and as the kayak crosses the waves, the compartments alternately  
become of higher and then lower pressure than the outside. They are,  
in effect, breathing. If there were no bulkheads this would not  
happen. The tiny hole that people put in their bulkheads does not  
change this situation because the pressure can not equalize across  
such a small hole this quickly. The bellows effect is more pronounced  
when conditions get bad. People who have been puzzled with the fact  
that a small amount of water is getting into their boat while  
paddling in moderate conditions can find out at the wrong time that  
the situation is a lot worse when conditions go bad. A small leak can  
become a big problem.

This difference in pressure means that the kayak effectively sucks  
water through the small hole about half the time. The other half the  
time, it blows air back out. It is surprising how much water can come  
in through a small hole under such circumstances. It is like a pump.

Usually this is a nuisance, but the hole does not have to be that big  
to become a problem on a rough day.

I have seen this phenomena be a problem even in places above the  
waterline, for example a hatch leak at the junction with the deck. A  
little puddle might collect here and be replenished frequently and  
the boat is quietly drinking from that puddle enthusiastically every  
time a relative vacuum is being created in the bulkheaded space.

One can conceive of circumstances that one could try and do something  
about this. In a boat with a hatch in the aft bulkhead, it might  
actually be worth opening that hatch so the pressure in that back  
compartment is equalized.

Understanding the disadvantages of that strategy, blah blah.

__________

Anyway, one of the advantages of building your own fiberglass boat  
(there are not many) is that as the builder you can devote attention  
to the details of inside and outside seams and hatch mountings that  
many commercial builders cannot "afford" to do.

There should be a zero-tolerance policy to leaks with the Doug Lloyd  
bubble test.

At least with the rudderless crowd. Many rudder installations  
effectively mean there is a leak into the back bulkheaded space. The  
"hole" can be tolerated if it only intermittently is flooded with  
water. If there is no "standing" water over the hole, then the volume  
of water that gets in will probably not be dangerous.

As a matter of kayak design, it is preferable if hatch-deck junctions  
and seams and rudder line entrance areas are not in puddles. Many  
designs do not meet this particular standard.


On Apr 3, 2007, at 1:24 PM, Michael Daly wrote:

> With composite kayaks, I think you have to differentiate between a  
> leak that constitutes a leak and one that constitutes a potential  
> structural failure.  The small one of the former is annoying, a  
> large one or the latter, dangerous.
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From: Doug Lloyd <douglloyd_at_shaw.ca>
subject: Re: [Paddlewise] pressurize the boat
Date: Tue, 03 Apr 2007 15:09:03 -0700
I'm aware of the SOF issue. I guess I realize the SOF's are better at 
shorter duration trips/outing - not long, dangerous crossing or rough, 
extended off shore paddling.

I figured someone would bring up the pin hole issue. Leak testers need to 
work out how they are going to take that into account.

I heard back from Sharon Bloyd-Peshkin at the Magazine Program, Journalism 
Department of Columbia College Chicago. She said the hatch on the Epic kayak 
wasn't strapped down tight enough. Mike had a similar boat in the past which 
didn't need as much cinching down. he was obviously unaware of the issue at 
the time of the incident.

Doug L




> Doug Lloyd wrote:
>> FOLLOW UP POST - Try the Southwind site for some _great information_:
>
> One problem with that info is that it assumes all bulkheads are perfectly 
> watertight.  Many kayaks have a teensy hole in the centre to allow for air 
> pressure equalization.  I put one in both front and rear bulkheads after 
> seeing the hatch covers bulging (Kayaksport rubber).  No amount of rolling 
> or other wet practice has ever resulted in anything other than a bit of 
> dampness in the compartment.
>
> If you're really paranoid about leaks, Doug, you're gonna have a lot of 
> fun with an SOF.  What with sewing seams making holes in the fabric that 
> are sometimes too large (just) to completely close with paint or varnish, 
> you're gonna have to decide whether you want a bit of a leak or go crazy 
> finding and filling every possible hole.  Since the reserve buoyancy in an 
> SOF comes from flotation bags and not the skin's integrity, it's really a 
> moot point, IMHO.
>
> With composite kayaks, I think you have to differentiate between a leak 
> that constitutes a leak and one that constitutes a potential structural 
> failure.  The small one of the former is annoying, a large one or the 
> latter, dangerous.
>
> Mike
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From: <cholst_at_bitstream.net>
subject: Re: [Paddlewise] pressurize the boat
Date: Wed, 4 Apr 2007 12:14:44 -0500 (CDT)
> I'm aware of the SOF issue. I guess I realize the SOF's are better at
> shorter duration trips/outing - not long, dangerous crossing or rough,
> extended off shore paddling.

Doug, if you can find a copy of Watkins' Last Expedition, by F. Spencer
Chapman, you should read his account of what I recall was a hundred-mile
or more trip in an Inuit-built SOF kayak in weather so rough that Chapman
was forced to roll several times. Even the Inuit he traveled with thought
it was a rough trip. Nonetheless, he stayed afloat, and without flotation
bags, at that.

Chuck Holst
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From: Doug Lloyd <douglloyd_at_shaw.ca>
subject: Re: [Paddlewise] pressurize the boat
Date: Tue, 03 Apr 2007 19:03:49 -0700
Robert said (big snip):
> One factor involved in leakage into a bow or stern compartment is
> pressure differences. This does not arise in a skin boat or any kayak
> without bulkheads but can have a profound effect in bulkheaded
> composite boats where a small leak that in and off itself might be of
> no particular significance can admit a large amount of water.

Robert, et al,
One of the reasons I'm a bit anal about leaks is because of all the 
modifications I've done to the hull and deck (I have a full-lenght keel 
strip bolted every 12" inches and custom-molded rudder lines entering the 
rear deck, to name a few.

I should also add that when my Nordkapp kayak was new in 1981, I got wet 
compartments all the time paddling, especially hot days in rough seas. I 
tried drilling the pin holes under advisement of the retailer in the 
bulkheads. It didn't help. That's when I took it in for the first leak test, 
performed by the retailer (I eventually started doing this myself) . We 
filled the pin holes first, then subsequently discovered bubbles coming from 
around the 7" hatch rims. I guess they are glassed in seperately and there 
were migratory pathways for the air/water exchange. We sealed them up (the 
dealer did). I eventually redid the rim edges where they are cut into the 
deck with my own attention for better detai, using epoxyl. I'm the one out 
there on the ocean, not the retailer as I once complained loudly.

Some paddlers trust their hatches so much they don't use gear bags. I never 
had that much faith. :-)

Doug L
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From: Peter Treby <ptreby_at_ozemail.com.au>
subject: Re: [Paddlewise] pressurize the boat
Date: Wed, 4 Apr 2007 12:55:13 +1000
"A small leak can  become a big problem... It is 
surprising how much water can come in through a 
small hole under such circumstances. It is like a 
pump. Usually this is a nuisance, but the hole 
does not have to be that big to become a problem 
on a rough day."
Have you ever seen this become a significant 
problem? I have drilled a 1 millimetre hole at the 
top of each bulkhead and each compartment remains 
dry, no matter how much rolling, surfing or 
bashing over waves the day involves. While a boat 
without bulkheads won't have this problem, isn't 
it likely true that much more water can enter the 
boat and fill spaces around float bags and other 
buoyancy in the event of a capsize and flooded 
boat, than with a bulkheaded boat? 
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From: Robert Livingston <bearboat2_at_comcast.net>
subject: Re: [Paddlewise] pressurize the boat
Date: Wed, 4 Apr 2007 01:26:23 -0700
On Apr 3, 2007, at 7:55 PM, Peter Treby wrote:
> "A small leak can  become a big problem... It is
> surprising how much water can come in through a
> small hole under such circumstances. It is like a
> pump. Usually this is a nuisance, but the hole
> does not have to be that big to become a problem
> on a rough day."
> Have you ever seen this become a significant
> problem? I have drilled a 1 millimetre hole at the
> top of each bulkhead and each compartment remains
> dry, no matter how much rolling, surfing or
> bashing over waves the day involves.

I mentioned the small hole in the bulkhead only to say that the goal  
of that hole is to keep the pressure in the bulkheaded space equal to  
atmospheric pressure when you are taking your boat over a mountain  
pass or when the temperature is changing.

It works great for that.

But it is not a big enough hole to maintain an equilibrium pressure  
in the setting of the bellows effect of paddling a boat in rough  
water with the hull being alternately compressed and released by wave  
pressure every few seconds.

The water is not entering via that small hole in the bulkhead. There  
is no water up against that hole most of the time. The problem is  
some small leak in the seam or hatch or deck attachment point that  
normally does not admit much water but will admit water when the boat  
is flexing etc when traveling in rough water. The "vacuum" phenomena  
will suck the water in and alternately puff little bubbles of air out.

Rolling is a different situation. The "pressure" in the bulkheaded  
space is likely never much different than the outside and small holes  
(such as that deliberately put in a bulkhead) do not admit much water  
between the fact that there is no pressure difference and that that  
hole only for short times might have water up against it. The key is  
that that hole is not exposed to water all day long.

If you have the round rubber hatches that I prefer which are air- 
tight, you can just plug up any bulkhead hole vents and take the boat  
from the hot air into cold water or from a cold spot to a warm one  
and look at the hatch. It should bulge out or suck in. If it does  
not, you have a leak.

Not as useful as the Lloyd test because you do not know the location  
but it has alerted me to the problem when I would notice my front  
hatch bulging out but not the back hatch or on one boat but not the  
other. My recent experience had to do with deck fittings that I  
THOUGHT I had installed watertight. If they are in recessed  
depressions, they are perfect places for the bellows effect --  
patiently pulling in water.

I am compulsive about this stuff because I like my boats dry for  
camping. I do not store everything in water-tight bags. Water  
resistant bags are easier for many things. Once of those safety vs  
convenience tradeoffs. But I have been on trips where someone in a  
commercial boat had a gallon of water accumulate in a day of vaguely  
rough water paddling without a clearly visible leak even looking at  
the situation on dry land. That is up there in the "effects handling"  
category.

When I read these stories of experienced people getting into trouble  
with leaks that they did not "know" about it, it is troubling. They  
are sinking and they do not know why! There is no "obvious" hole. I  
believe this occurs largely in the context of bulkheads. The same  
holes in a boat without bulkheads would admit substantially less  
water. -- or they would learn about it sooner :)

On my earlier boats I would make hatches that were essentially just  
two cockpit rims covered with two spray covers, one slightly smaller  
inside the other. Actually it worked pretty well in an era that good  
watertight hatches were hard to find ( or some sand would get in the  
threads or whatever). If the boat was upright it worked perfectly. If  
you rolled a lot or spent time with the boat upside down then some  
water would get in so it is was not as good as the commercial rubber  
hatches available today. I built a small, very "rigid" kayak for  
surfing and camping and I would watch endlessly -- what else is there  
to do :) -- the front hatch puffing up and sucking back as I  
travelled through the waves. I would have never guessed how much  
compression and relaxation of the hull was taking place without  
having the benefit of watching this little rhythm. Suddenly it made  
sense that "leaks" that would normally not admit any water of  
consequence could pull in a lot of water. In calm water paddling, you  
did not see it.


> While a boat
> without bulkheads won't have this problem, isn't
> it likely true that much more water can enter the
> boat and fill spaces around float bags and other
> buoyancy in the event of a capsize and flooded
> boat, than with a bulkheaded boat?

ABSOLUTELY. I believe in bulkheaded boats with the cockpit volume  
minimized. That means no space behind the seat, that back bulkhead  
wrapping around the hips and the feet up against the front bulkhead.  
I think that a boat should paddle reasonably well with the cockpit  
area completely flooded and a dysfunctional spray skirt. It is  
possible to design boats this way. Few are.

I am just saying that people with bulkheaded boats should be a little  
more compulsive about looking for leaks. For me that means no leaks  
-- air tight (except for the bulkhead vent hole)

I am no fan of the float bag approach. But for the open canoe or the  
skin boat that is the way to go, obviously. Just another trade-off.
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From: Dave Kruger <kdruger_at_pacifier.com>
subject: Re: [Paddlewise] pressurize the boat
Date: Wed, 04 Apr 2007 02:39:26 -0700
Peter Treby wrote:

> "A small leak can  become a big problem... It is surprising how much 
> water can come in through a small hole under such circumstances. It is 
> like a pump. Usually this is a nuisance, but the hole does not have to 
> be that big to become a problem on a rough day."

> Have you ever seen this become a significant problem? I have drilled a 1
> millimetre hole at the top of each bulkhead and each compartment remains
> dry, no matter how much rolling, surfing or bashing over waves the day
> involves.

As Robert Livingston said, it is not that hole which allows water in; it is 
any hole in the outside of the hull in regular contact with water.  In my 
boats, I do not see leaks into the _bulkheaded_compartments_ any more; 
rather, I get water "pumping" from the hull flex mechanism, operating on 
the opening the rudder cables demand, _into_the_cockpit_, where they exit 
the hull-deck seam.  The cables run along the inner edge of the H-shaped 
rubber extrusion which "seals" the hull and deck.*  The hull and deck are 
mated with a structurally sound overlap of mat and resin on the inside; 
but, the cables have to penetrate that mat/resin overlap, and after a few 
hours of rough water travel, I'll have a quart or so of water sloshing 
around in the cockpit.

That quart of water has never been a problem; I know from rescue practice 
that even a couple gallons of water is not enough to materially affect the 
handling of my boats.  I get wet some from the leakage; but, it _is_ a wet 
sport, after all.

---------
*That H-shaped extrusion is laughable as a "seal"; it just makes the 
hull-deck seam look good;  I think its main function is to maintain 
registration when the real seal (the mat and resin overlap on the inside) 
is bedded in place at manufacture.  Once, I replaced most of the overlap in 
a boat which had been oil-canned in surf; the H-extrusion helped me mate 
the halves, but that was about all.

-- 
Dave Kruger
Astoria, OR
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From: Peter Treby <ptreby_at_ozemail.com.au>
subject: Re: [Paddlewise] pressurize the boat
Date: Thu, 05 Apr 2007 08:02:32 +1000
"...I have been on trips where someone in a commercial boat had a gallon 
of water accumulate in a day of vaguely rough water paddling without a 
clearly visible leak even looking at the situation on dry land. That is 
up there in the "effects handling" category."
The backup buoyancy approach has a lot to recommend it. Even with 
bulkheads and quality rubber hatches, it is comforting to have back up 
buoyancy inside compartments. If on a long trip, the compartments might 
be filled with dry bags full of gear. If a day trip, I used to stuff the 
two larger compartments with an inflatable float bag. I've gotten a bit 
slack about that lately, as compartments remain dry in all conditions, 
but the Great Lakes Sinking Story might get me back into that habit.

"On my earlier boats I would make hatches that were essentially just two 
cockpit rims covered with two spray covers, one slightly smaller inside 
the other. Actually it worked pretty well in an era that good watertight 
hatches were hard to find ( or some sand would get in the threads or 
whatever)."
Other than VCP rubber hatches, the only other hatch cover I have seen 
which keeps a compartment completely dry is a vinyl sewn cloth cover 
with a double thick bungy cord running around a sewn tube at the bottom 
edge. This goes over a round fibreglass coaming. These are used on "Sea 
Leopard" kayaks, pictures here: 
http://raftakayaks.spaces.live.com/default.aspx?_c02_owner=1
Photos 1,2 and 6 in the slides show these hatches. (Some classy paddlers 
there: check the guy in the red inflatable PFD ;-)) Perhaps surprising 
that this lightweight system works, but it does, at least in rolling and 
upright paddling in rough water. I don't have experience of surf 
capsizes with these, still need to be assured that they hold up against 
implosion in all conditions, but others say so.
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From: Robert Livingston <bearboat2_at_comcast.net>
subject: Re: [Paddlewise] pressurize the boat
Date: Wed, 4 Apr 2007 16:04:39 -0700
I have had very good experiences with the Kajak hatches (glued to the  
fiberglass with 3M Sealant 5200). (I have used all the round rubber  
sizes with them all being air-tight.) I have not used their larger  
Oval ones although the biggest round one at about 9" seems like a  
beautiful gapping hole if you grew up with the old screw down hatches  
of my old Baidarka at about 7" and suits me fine as a camping kayaker.



On Apr 4, 2007, at 3:02 PM, Peter Treby wrote:

> Other than VCP rubber hatches, the only other hatch cover I have  
> seen which keeps a compartment completely dry
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From: Doug Lloyd <douglloyd_at_shaw.ca>
subject: Re: [Paddlewise] pressurize the boat
Date: Wed, 04 Apr 2007 10:41:43 -0700
True. Not being a SOF builder/user yet, I was assuming the context for SOF 
use as outlined from other, more authoritative modern sources who gave a 
summary similar to what I posted. I would well imagine that there were a 
number of Inuit paddler over the millennia who were blown out to sea for 
days of survival paddling in their trusty steeds, returning to rub noses 
with the little women at home in the Igloo. Maybe the single guys just 
rubbed noses with their sled dogs.

If I make a SOF (thanks Turner for more input), you bet it will be as 
watertight as I can make it, even if it weighs a bit more than the usual.

Doug




>> I'm aware of the SOF issue. I guess I realize the SOF's are better at
>> shorter duration trips/outing - not long, dangerous crossing or rough,
>> extended off shore paddling.
>
> Doug, if you can find a copy of Watkins' Last Expedition, by F. Spencer
> Chapman, you should read his account of what I recall was a hundred-mile
> or more trip in an Inuit-built SOF kayak in weather so rough that Chapman
> was forced to roll several times. Even the Inuit he traveled with thought
> it was a rough trip. Nonetheless, he stayed afloat, and without flotation
> bags, at that.
>
> Chuck Holst
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From: <Rcgibbert_at_aol.com>
subject: Re: [Paddlewise] pressurize the boat
Date: Wed, 4 Apr 2007 18:35:05 EDT
In a message dated 4/4/2007 3:06:15 PM Pacific Daylight Time,  
ptreby_at_ozemail.com.au writes:

"Photos  1,2 and 6 in the slides show these hatches. (Some classy paddlers 
there:  check the guy in the red inflatable PFD ;-)) Perhaps surprising 
that this  lightweight system works, but it does, at least in rolling and 
upright  paddling in rough water. I don't have experience of surf 
capsizes with  these, still need to be assured that they hold up against 
implosion in all  conditions, but others say so."



Somehow I'm not sure that would work in surf. A friend of mine had his  
Feathercraft K1 roll top hatch with the cordura/bungy cover blown through in the  
surf. It needs to be supported underneath. a thread was started on another 
board  some time ago regarding spare hatch covers. Some reported that neoprene and 
 bungie or nylon and bungie do implode in surf and would add that a beachball 
or  paddlefloat underneath for support was a possible resolution.
 
I carry the spare neo and bungy hatch covers for the NDK/Valley sizes.  
Simple, small and matches what others often use. However, a cockpit cover  and 4' 
of bungy fits all the larger ones you see out there.
 
Cheers,
 
Rob G



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From: Matt Broze <mkayaks_at_oz.net>
subject: Re: [Paddlewise] pressurize the boat
Date: Thu, 5 Apr 2007 00:07:12 -0700
Thanks for the description of the bellows effect that can pump water in
through very small holes when waves are alternating squeezing and releasing
the hull. Your hatch designs certainly made this effect obvious.  Is it okay
if I quote you for an update of the "Flotation" manual on our website? For
those interested in flotation and leaks I recommend taking a look at that
"Flotation" manual. It gets into detail as to the pros and cons of most
flotation systems including many examples of system failures I've heard,
read or have written about for Sea Kayaker magazine (now in Sea Kayaker's
Deep Trouble).

I agree with Robert that bulkheads for footrests and wrap around the cockpit
stern bulkheads are a good way to increase a kayak's buoyancy. Adding a pod
would be even better as it also adds more buoyant volume along the side of
the seat and leg area of the kayak. The catch is that unless the kayak is
carefully custom fit to the paddler's dimensions you are going to looses a
lot of volume to adjustable foot pedals and backrests. I might also point
out that a float bag that is big enough can fill up the space lost to the
adjustable foot braces (when using a bulkhead) may well provide more
buoyancy than a bulkhead in front of the adjustable foot pedals (especially
so for a shorter legged paddler). The catch there is that most float bags
available aren't nearly big enough for sea kayaks.

Matt Broze
www.marinerkayaks.com
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From: Matt Broze <mkayaks_at_oz.net>
subject: Re: [Paddlewise] pressurize the boat
Date: Fri, 6 Apr 2007 01:03:51 -0700
Dave Kruger wrote:

>>>>As Robert Livingston said, it is not that hole which allows water in; it
is
any hole in the outside of the hull in regular contact with water.  In my
boats, I do not see leaks into the _bulkheaded_compartments_ any more;
rather, I get water "pumping" from the hull flex mechanism, operating on
the opening the rudder cables demand, _into_the_cockpit_, where they exit
the hull-deck seam.  The cables run along the inner edge of the H-shaped
rubber extrusion which "seals" the hull and deck.*  The hull and deck are
mated with a structurally sound overlap of mat and resin on the inside;
but, the cables have to penetrate that mat/resin overlap, and after a few
hours of rough water travel, I'll have a quart or so of water sloshing
around in the cockpit.

That quart of water has never been a problem; I know from rescue practice
that even a couple gallons of water is not enough to materially affect the
handling of my boats.  I get wet some from the leakage; but, it _is_ a wet
sport, after all.

- ---------
*That H-shaped extrusion is laughable as a "seal"; it just makes the
hull-deck seam look good;  I think its main function is to maintain
registration when the real seal (the mat and resin overlap on the inside)
is bedded in place at manufacture.  Once, I replaced most of the overlap in
a boat which had been oil-canned in surf; the H-extrusion helped me mate
the halves, but that was about all.<<<<<<<<<<<<<<<<

Your asterisked section above is an astute observation. Those are the
H-shaped extrusion's functions. With a vacuum-bag mold the cockpit opening
is closed and must be cut open later to put the cockpit in. That means the
kayak can not be seamed together when it is still in the molds (by bolting
the mold halves/boat halves together after the edges are trimmed flush with
the mold and seaming the inside through the cockpit hole). Therefore, the
much thinner boat parts have to be held together somehow, in register, and
sealed such that the resin in the seams can't leak out though the gap
between the hull and the deck. The vinyl H-molding (and several strips of
masking tape to temporarily hold things in place) provides those functions
and also means that the seaming job is completely finished once the masking
tapes are removed. This is a very efficient and labor saving way to seam a
fiberglass kayak together and you end up with a very crisp looking seam.
With vacuum-formed plastic kayaks the hull and deck are just glued into the
extrusion so no inside seam is even necessary.

Contrast this with what must be done with a vacuum-bagged kayak otherwise.
The parts must be trimmed and removed from the mold as before but without
the vinyl extrusion they must be carefully butted together and taped with
masking tape every 4 to 6 inches in a manner that doesn't start to generate
a twist to the hull. Next long strips of masking tape are put along the seam
to seal it for putting on the fiberglass inside seams (which is pretty much
the same job for both types). Once the seams have cured a lot more masking
tape must be removed with the non-vinyl extrusion type (outside seams). Now
some way must be found to cover the raw edges of the seam where they butt
together. In early fiberglass kayaks this was often covered with a long
strip of plastic electrical type tape. The downside was that later handling
often resulted in the tape getting moved and looking bad. It was pretty easy
to replace though. Today most kayaks that don't use vinyl extrusion in the
seams are made with fiberglass outside seams. This requires two new long
strips of masking tape be placed along the seam at an equal distance apart,
by eye, on each side of the kayak. Next someone must sand the shiny waxed
gelcoat surface between the strips of masking tape so the fiberglass resin
has a roughened surface to get a good grip on when the fiberglass outside
seams cure. A layer of fiberglass "selvedge edge" tape is wetted out with
resin and laid down between the masking tapes and the masking tapes must be
peeled up while the resin is still runny or it won't leave a clean edge (the
cured resin overlapping it will tear the tape or the gummy resin will make
strings that will mess up a clean edge appearance when the tape is removed).
The resin was often pigmented black or some other color and a liquid wax
(known as "surface agent") was added to make the outside seams cure
completely so they weren't gummy on their surface. When resin cures in
contact with air the surface layer of resin molecules are air inhibited and
never cure. The downside of this was that the outside seams were pretty
rough and could abrade other boats they rubbed against on say a car rack (or
ones knuckles if scraped across them). The selvedge edge (where the fibers
fold back toward the center to form the tape edge) would often protrude a
little above the grade of the rest of the tape aggravating the problem. To
solve this many builders mask off the area again and sand of any rough spots
that stick up above grade and then cover the whole thing with gelcoat that
has a smoothing agent and a surface curing agent in it, making another step
in the long process.

As you may have guessed fiberglass outside seaming certainly isn't a very
efficient process. One builder told me there was eight man hours of labor in
just the fiberglass outside seams of his kayaks. A strip of vinyl extrusion
doesn't cost as much as even a half hour of labor so why don't those
manufactures just use the extrusion? Nobody has a patent on it.  If you
order the extrusion with a hole down the middle you can even eliminate the
plastic tubes that the rudder cables need to run through otherwise (to keep
the cables from sawing through the fiberglass where they enter the kayak,
any bulkheads they pass through, and your rear compartment's gear bags when
worked back and forth as you use the rudder).

Now, why is the title of this thread "Pressurize the boat"? Oh yeah, to find
leaks. Leaks have been a major problem for H-seams. As Robert described,
anywhere that water can puddle, where there is also a tiny hole, the flex of
the boat and resulting pumping action draws water into the boat. Dave,
above, blamed that process for the water getting into his cockpit but I
think he is mistaken about that unless he has a taut and airtight spraydeck.
I think his leak is one I observed once in trying to stop multiple leaks in
a kayak. The rudder cables working back and forth as they do move water
inside the rudder cable tubes until it is running down into the cockpit. My
suggestion to Dave is to inject some silicone sealant into the tube where
the rudder cables emerge near the back of the kayak and let it cure. This
will make the cable hole a lot smaller there (and as the silicone sealant is
sawn away enough by the cable that the leak reappears replace it again). The
main problem with the H-seam is that the upper half hold water and if there
are any pin-hole leaks in the inside seam that water can be pumped into the
closed compartments and replaced in the "gutters" by the next wave high
enough to lap over the seam. One manufacture even admitted there was a
problem with the early H-seams but claimed his new seams fixed the problem.
The new seams had the uneven lengths of the H-seam switched around. The
shorter side was on the outside. I think the theory was that way there would
be no head of water since the water on the outside would pour over the edge
of the tape before it could get high enough to go through any holes and pour
over the inside of the tape. If I'm correct in that speculation, he didn't
count on Robert Livingston's pumping action observation as the new seams
were leak prone just as the old had been. So why can't the inside seams
adequately seal the kayak with H-molding? Well, sometimes they do. But then
again, sometimes they don't. I think the problem is partly due to the inside
edge of the H itself. When the inside fiberglass seam tape bridges across
that H edge to seam to the hull or deck a bubble line in the resin often
forms along the bridged gap. As the resin cure some of those bubbles break
and form pin-holes. The other problem is that someone seamed the ends of the
kayak by reaching in with a brush on the end of a long stick and having done
this many times I can attest that you don't have a good enough angle to
really see how well you have done at getting the bubbles out near the ends
of the kayak or maybe even in getting the fiberglass seam tape completely
saturated way down there. Coincidentally, or not, most seam leaks are near
the ends of the kayak. While hatches on many kayaks are not very watertight,
if a kayak has H-seams and is getting water inside I'd check the seams first
as they are the most likely leak site. Rather than pressurizing the
compartment though, I'd just put several gallons of water inside the kayak
and rotate it around to see where it leaks out (or stand the kayak on end
and fill up the lower three feet of so to give the water a little head to
increase the water pressure to help it find the leaks for you.

If you find that your H-seams leak, don't despair, there is a rather simple
fix. Get a tube of silicone sealant and cut the long applicator tip at an
acute angle, like a hypodermic needle. Fill the top half of the H with the
sealant by injecting it in as you move your "needle" slowly along the seam.
If the vinyl of the H is too stiff to get your "needle" into, warm it up
some with a hair dryer to soften it temporarily. Don't bother trying to seal
the inside seam with thickened resin, as is often tried. Most likely you
will just add several pounds to the kayaks weight and find it is still
leaking some.

Matt Broze
www.marinerkayaks.com
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From: Duane Strosaker <strosaker_at_yahoo.com>
subject: Re: [Paddlewise] pressurize the boat
Date: Fri, 6 Apr 2007 20:47:53 -0700 (PDT)
Matt,
   
  Thanks so much for the info on seam construction methods. With all the building info you've provided over the years (and I printed out), I could start a kayak manufacturing business. But there are easier and healthier ways to make a living.
   
  Also, I have to give pros like you, John W. and Nick S. a lot of credit for having the guts to contribute to this email list. I know a lot of pros lurk here but aren't willing to post.
   
  Duane
  www.rollordrown.com
  Southern California
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Submissions:     PaddleWise_at_PaddleWise.net
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