building a kayak bulkhead
Luc Martel
ideas on materials and or methods of installation?
Bill Pendlebury
from Necky but I was told they no longer sell them separately. They were
made of 3" thick Minicell foam and glued in place with an adhesive/sealant
named Lexel. The Lexel came in a tube that fits a caulking gun and was
available at my local building supplies stores. You could probably get the
foam from a kayak store or mail order like NRS.
I first cut a template out of cardboard and then added pieces or trimmed
away until I had a good fit. Then I traced the template on the foam and cut
it out with a bandsaw. I marked the position inside of the hull, spread
glue on the marks inside the hull, and inserted the bulkhead. Lastly, I put
a good sized bead of sealant around the edges on both sides of the bulkhead.
Hope this helps.
Luc Martel wrote in message <7eu7k7$c20$1...@bgtnsc03.worldnet.att.net>...
Bill Apfel
Closed cell foam. Can RTV around for a water tight fit. Cut cardboard for
the trmplit.
Al Bowers
"Bill Pendlebury" <wpe...@fast.net> writes:
> Luc Martel wrote in message <7eu7k7$c20$1...@bgtnsc03.worldnet.att.net>...
> >I have purchased a Necky Alsek kayak and would like to install bulkeads.
> >Any
> >ideas on materials and or methods of installation?
> We used to own an Alsek and a Kyook. I ordered rear bulkhead and hatch kits
> from Necky but I was told they no longer sell them separately. They were
> made of 3" thick Minicell foam and glued in place with an adhesive/sealant
> named Lexel.
A friend added a fiberglass bulkhead to his Seda Swift (fiberglass sea
kayak). It was such a slick professional looking job, it looks like
the boat was always intended to have that bulkhead (Seda will sell the
boat with a foreward bulkhead, but this particular boat was delivered
without one).
He started with a piece of 3/4 inch exterior grade plywood that was
cut out slightly larger than the hull of the kayak at the bulkhead
location. The plywood was split horizontally (this is important to
remove the mold after forming), but small "holders" were bolted to the
two halves to hold the pieces together. After the boat was reasonably
placed inside the plywood, the ply was spaced up a bit with two dowels
so an approximately equal airspace was all around the boat between the
ply and the boat. A spray-on release agent was applied to the boat
(don't get any on the ply!). Then the airspace between the ply and
the boat was filled with auto grade bondo and allowed to dry. After
the bondo hardened, the ply was split (removing the holders) and
removed from the boat. The boat was cleaned an set aside. Next, the
two ply pieces were put back together and laid on another sheet of
plywood. Careful trimming and sanding of the bondo where it oozed out
from between the ply and the boat cleaned up the edge so the two
pieces of ply laid against each other cleanly. The entire mess was
sprayed with release agent. A fiberglass cloth was laid into the mold
and epoxied. If you really want to be slick, you can vaccuum bag the
whole thing and make a very clean bulkhead. After the 'glass
hardened, it was poped out of the mold and the edge was cleaned up.
Now you will probably note that the bulkhead is a bit larger than the
hole it is meant to fit in; this is okay because of the taper in the
forward end of the kayak (assuming you don't have protrusions like a
compass mount or deck rigging bolts that change the cross section.
Working inside the boat, fit the bulkhead into position and mark all
around the inside of the hull where the bulkhead fits. Move the
bulkhead back and apply epoxy where the flange on the edge of the
bulkhead will meet the hull. Press the bulkhead back into place and
allow the epoxy to harden.
The process is simpler than it sounds, and the result is truely
beautiful.
Al Bowers ...composite dabbler...
Wayne S. Hill
>"Bill Pendlebury" writes:
>> Luc Martel wrote...
>
>> >I have purchased a Necky Alsek kayak and would like to install bulkeads.
>> >Any ideas on materials and or methods of installation?
>
>> We used to own an Alsek and a Kyook. I ordered rear bulkhead and hatch kits
>> from Necky but I was told they no longer sell them separately. They were
>> made of 3" thick Minicell foam and glued in place with an adhesive/sealant
>> named Lexel.
>
>A friend added a fiberglass bulkhead to his Seda Swift (fiberglass sea
>kayak). It was such a slick professional looking job, it looks like
>the boat was always intended to have that bulkhead (Seda will sell the
>boat with a foreward bulkhead, but this particular boat was delivered
>without one).
Sorry, but I didn't follow your description (am I right that the plywood
goes inside the boat, not the other way around?), but I'm sure it came
out looking well.
It's not clear to me, though, that a rigid glass bulkhead, rigidly
attached, is a good idea in a rigid kayak. In naval architecture
terminology, it makes a 'hard spot', which stresses the hull, especially
in the case of impact. Over the long haul, this is likely to damage the
hull, at least locally. In boat-building practice, the best way to
install a rigid bulkhead is to epoxy a strip of Airex foam inside the
hull. This should be 1/2-in thick, say 1-1/2 inches wide, with the
edges beveled to form a land where the bulkhead will rest:
--------------------------
<---aft \\\\\\\\\\\\\\\\\\\\\\\\\\ Hull fwd --->
--------------------------
\ /
\ / Airex
------
| |
| | Bulkhead
| |
The bulkhead, made to fit the inside dimensions of the Airex, is
then installed and glassed in place. The glass is lapped from the
hull, over the Airex, and onto the bulkhead. This really should be
done on both sides of the bulkhead. If one side of the bulkhead is
dead space (not generally a good idea, in case of leaks), it is
still feasible to install the glass support on that side, then epoxy
the bulkhead in, then glass the accessible side. The Airex and shape
of the glass attachment allow some give between the bulkhead and hull,
yet the whole assembly is extremely strong.
Airex, BTW, is terrific stuff. It's an expanded closed cell PVC foam
that is extremely tough and uniquely non-crumbling. You can fold a
sheet of it in half. At least some other PVC foams will break. With
that said, I'm not sure where you can get it: I bought some years ago
from a commercial boat-builder's supply house, but places like Defender
(http://www.defenderus.com), which carry boat-building materials, don't
seem to carry it.
Short of this, I think people are better off with a thick foam bulkhead.
My concern here is that it pretty much has to be strong enough to stand
on to be safe. Think of a couple of feet of water (or more), about
1 psi, pushing on it trying to stove it in. That's a fair amount of
force, so installation should be taken seriously.
-Wayne
_______________________________________________________________________
Dr. Wayne S. Hill wsh...@world.std.com
Foster-Miller, Inc. ***Disclaimed*** 781-684-4228
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Al Bowers
wshills...@world.std.com (Wayne S. Hill) writes:
> Al Bowers said...
> >"Bill Pendlebury" writes:
> >> Luc Martel wrote...
Hi Wayne,
> >> >I have purchased a Necky Alsek kayak and would like to install bulkeads.
> >> >Any ideas on materials and or methods of installation?
>>> We used to own an Alsek and a Kyook. I ordered rear bulkhead >
>>> and hatch kits from Necky but I was told they no longer sell >
>>> them separately. They were made of 3" thick Minicell foam and >
>>> glued in place with an adhesive/sealant named Lexel.
>> A friend added a fiberglass bulkhead to his Seda Swift (fiberglass
>> sea kayak). It was such a slick professional looking job, it looks
>> like the boat was always intended to have that bulkhead (Seda will
>> sell the boat with a foreward bulkhead, but this particular boat
>> was delivered without one).
> Sorry, but I didn't follow your description (am I right that the plywood
> goes inside the boat, not the other way around?), but I'm sure it came
> out looking well.
The plywood goes _outside_ the boat. This is a common techique in
aircraft to make an accurate mold (female) of a part. The bulkhead is
a fiberglass layup popped out of that mold.
> It's not clear to me, though, that a rigid glass bulkhead, rigidly
> attached, is a good idea in a rigid kayak. In naval architecture
> terminology, it makes a 'hard spot', which stresses the hull, especially
> in the case of impact. Over the long haul, this is likely to damage the
> hull, at least locally.
Yes, it does form a "hard spot" in the hull. But I think this is a
rather common practice in higher-end all composite boats, especially
the lighter ones. The point of the above exercise was to replicate
the original manufacturer equipment; a job which this technique did
very well.
As for the "hard spot" problem, no doubt it may cause a problem with
localized failure in impacts. This may be the reason that Current
Designs uses plastic (polyethylene) bulkheads which are simply caulked
into place. But all the Seda boats have hard bulkheads installed as
described. It makes the hull more rigid, less suspect to oil canning,
and keeps the weight down to a minimum.
I wonder how this is done in very high end boats, like carbon fiber
designs from Easy Rider, Current Designs, or other high end companies.
I know Seda has made boats this way since 1969, and if it is
deficient, I would have thought they would have changed the design.
Any other thoughts?
Al Bowers