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Spray HPK – Hatches and Bulkheads

Posted By Dan Caouette

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With the bare hull and deck constructed it was time to switch gears and start working on components that are attached to the interior of the kayak.  Spefically hatches, fittings for deck lines, bulkheads, steering components and the cockpit coaming.  In theory all of these items could be installed after the deck is bonded to the hull.  It’s much easier to build and install them now when the kayak is open.

Due to all the components I’ll break these up into a few entries.  This one will cover the hatch lips and bulkheads.

First up: The Hatches

There are many kinds of hatch systems we could have used on the project.

2012-wahoo-fsk-nh04The first option is to have no hatches or bulkheads at all.  Storage access would be through the cockpit.  Floatation would be provided by airbags stuffed in the ends.  Some race classes require bulkheads and hatches to be a kayak so that wasn’t an option.

Hatch - BecksonBeckson deck plates are nice.  They are relatively light in weight and are watertight.  The downsides is you are limited in size (4″, 6″ or 8″ maximum) and need a flat surface to mount to.

Hatch - VCP OvalVCP-style rubber hatches are virtually bombproof and allow larger opening sizes.  They are used on a large majority of commercially built kayaks.   They  also need a flat mounting surface and man, are they HEAVY!

The last option was to make wooden lids out of the stripped and fiberglassed deck.  A carbon fiber lip which holds a foam gasket is then bonded to the inside of the deck.  The lid is held on with bungee cords or straps.  Like most of my builds, the bungee cords will be routed internally using carbon fiber hardware for a very smooth, clean deck exterior.  They are very light and watertight and can be built to any size.  Since they are cut from the deck, there is no issue for flatness for mounting.  They can be cut out of highly curved surfaces and always match.

Due to the curved decks and goal of a lightweight build, Zack decided to go the last route.  They were sized similar to commercial hatches.  Both main hatches are egg-shaped ovals. The front hatch has an opening of 10″x 12″.  The stern hatch is 12″ x 17″.  There is also a small 6″ round opening directly over the rudder post.  It’s built using the same method.

Zack also wanted a “day” hatch for easy access on the water.  That one uses a Beckson deck plate as a base and will be covered under a seperate post. (Truth is, as of this post, the plate hasn’t been installed yet.  It should arrive this afternoon.)

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First the hatches were located on and the outline transferred to the deck.  These were “regular” sizes so I was able to use 1/2 patterns and traced them onto the deck with a Sharpie.  Custom-sized ones I print on paper and mount with a light mist of spray glue.

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The hatch lids are then cutout and everything is sanded smooth.

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Now to make the lips.  The lids are first taped back onto the deck.  I used scraps of cedar strips to hold the lids vertically.

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The deck is flipped over and packing tape is applied to the face of the hatch lid and the vicinity.  You can also use clear self-adhesive shelf protection film.  This forms the release so the epoxy doesn’t stick to the deck or the lid.  I used to tape only the hatch lid but there was too much clean-up.  This is quicker.

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Now laminate the lips.  I started with a layer of 4oz E glass as a sand-able scrim (if needed), then the show layer of twill carbon fiber, three layers of 9oz tightweave E-glass, an inner layer of carbon and a final layer of 3.2oz E-glass to smooth the interior. The final thickness is just over a 1/16″.   The lips could be made entirely out of fiberglass.  The carbon fiber is mostly for show when the hatches are open.

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The next morning I removed the masking tape and cedar support struts and gently popped the lids off of the lamination.  I took a sharp awl and scribed the hatch opening onto the carbon lip.  This registers the lip with the deck.  The lamination could then be popped from the deck interior and all packing tape was removed.

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Using a compass and the hatch openings I marked the inner and outer offsets for the lips.  The inner offset is 3/4″ and will hold the gasket material and support the hatch.  The outer offset is also about 7/8″ wide and will be the surface that gets bonded to the deck.  Their cut and sanded to the lines.

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The lips are placed back on the deck interior and the outer offset is marked on the deck.  This area and the lip are roughened up with sandpaper so the lips will adhere.

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Thickened epoxy is spread onto the mating surfaces and pressed together.  For the bonding I tried some JD Thixo 2-part epoxy.  It was very controllable.  What little waste was in the cleanable mixing nozzle.  Not a lot of clamping pressure is required.  Here I used a few 2″ spring clamps.  All squeeze out needs to be removed now.  It’ll be a lot harder to remove when it’s hardened and there’s a high likelihood of damaging the lip. Now’s a good time to seal any exposed wood edges with thickened epoxy.

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When cured just remove the clamps.  In a future post I’ll make and mount the internal hardware and add the pull tabs.

Bulkheads

In a way, bulkheads are related to the hatches.  If you have bulkheads you need a way to access them, hence hatches.  These are pretty typical so I won’t bore you with the details of how I made them. Just 3/16″ cedar strips skinned on both sides with fiberglass.  I made them the same time as the deck.

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There is a single hatch up front.  To minimize the cockpit volume it’s located as close to footbraces as possible without being in the way.  This one landed near to a station and was easy to fit.  Here’s it’s tacked in place with some hotglue.  It’ll be held with epoxy fillets.  The cleanest way to make fillets is to mask off the area.

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The stern gets two bulkheads.  The nearest one is placed close to the edge of the coaming, slanting toward the seat to minimize cockpit volume.  The second one is placed about 10″ back and forms the day-hatch hold.  Here the bulkheads have been fitted, tacked in place and the fillets have been applied.

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The masking tape is best removed while the epoxy is still a bit green, usually after a couple hours.

Next post: deck fittings!

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4 thoughts on “Spray HPK – Hatches and Bulkheads

  1. This system of hatches is very interesting especially to them to the extent we want, but they are really effective to keep out any water, or function Beckson best type purchased?
    Very good post.

    1. The hatches held by internal bungees have been mostly reliable to date. Lately I’ve been adding pull loops to the lids because in the past they have sealed too well and were hard to open. You have to be really careful the deck and/or hatch lid stay in shape during the build. If one or both warp, usually warping the deck to fit a misaligned hull, they can leak. They’ve been mostly installed on race hulls where weight is a concern. They definitely are much lighter than plastic Beckson or rubber (ie VCP or KayakSport) hatch systems. On expedition kayaks the bungees get in the way of the cargo. The rubber lids for those kayaks may be preferable. They can be a pain to open on the water. That’s why I don’t recommend them for day hatches.

  2. Dan,
    Do you not add something between the CF lips and the hull to account for the thickness of whatever you use for a gasket?
    Thank You.
    Matthew

    1. I’ve found it to be unnecessary. The gasket I use is 1/8″ thick (about a 1/16″ compressed). The thickened epoxy used to bond the lip to the underside of the deck does add some thickness.

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