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Screw-Down
Boat Hatches – An Alternative to Tape!
By
Ralph von Eppinghoven
Metro Marine Modelers
Toronto, Canada
As Fast Electric (FE)
radio control boats get more realistic and detailed in appearance, it is
becoming desirable to find simple, secure and “clean” methods of fastening
the hatch to the hull of the model boat. The vast majority of FE boaters
simply tape down the hatch using clear tape or electrical tape. Taping the
hatch is an effective way to seal and secure the hatch, but if you have
spent many hours painting and decaling your model to replicate a real
offshore or hydroplane racer, applying tape to the hull may not be your
first choice for securing the hatch. This article shows how to fasten the
hatch, for either monohulls or hydroplanes, by screwing the hatch onto the
deck. This is a secure and waterproof method of fastening the hatch, and
also improves the boat’s appearance.
Screw-down hatches are easy, professional
looking, and waterproof
1: SELECTING SCREW-DOWN HATCHES:
It is possible to screw down many different types of hatches
for both monohull and hydroplane models. All that is required is a flat
surface around the perimeter of the hatch, and a flat “ledge” around the
interior of the deck on which the hatch rests. If these features are found
on the hull, then it is possible to install a screw-down hatch instead of
taping the hatch in place. Photos 2 and 3 show hydroplane and monohull FE
models with finished, screw down hatches in place.
In all cases the hatches are screwed down onto the hull using small socket
head screws and blind nuts that are installed under the ledge around the
inside of the deck. Foam tape, or weather striping, is placed under the
hatch to ensure the hatch has a watertight seal on the deck.
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| Hydroplane hull with
screw-down hatch |
Monohull with
screw-down hatch |
2: REQUIRED MATERIALS
The following materials are required to fasten the hatch to
the hull using the screw-down method.
Materials
- 5/32” minimum thickness aircraft
plywood
- 6-32 stainless steel or nylon screws
- 6-32 stainless steel blind nuts
- Medium thickness CA Glue
- DuBro Instant Stik Foam Tape (Cat.
No. 163)
3: FASTNERS
The key to making the hatch easy to screw in place is to
install blind nuts under the deck ledge, which supports the hatch. The
simplest and strongest method of holding the blind nuts in place under the
ledge is to press them into small pieces of plywood (approximately 1/2” X
3/4”) and then glue these plywood pieces under the ledge. Photo 4 shows the
required materials and the small plywood pieces.
3/4” 6-32 screws, blind nuts and plywood
supports
As noted in Photo 4, the holes for the
blind nuts are slightly off centre – closer to one edge than the other. This
“shorter edge” is on the inside edge of the deck ledge so that it does not
protrude into the hull.
4: PREPARING THE HATCH AND DECK:
The first step is to determine at which locations to drill the holes in the
hatch. Typically, the hatch holes are spaced 5” – 7” apart around the edge
of the hatch as shown in Photo 5. The shape of the hatch also determines the
hole locations – a square hatch does not require a hole at the bow end,
whereas a monohull hatch usually requires one. As shown in Photo 5, the
9/64” diameter hatch holes need to be close enough to the edge of the hatch
so that they are approximately in the in the centre of the deck ledge. If
the holes are too far to the outside edge of the hatch, they may result in a
weakened hatch. Conversely, if the holes are too far too the inside of the
hatch, they may miss the deck ledge and not have a fastening point. Either
situation is a problem, so care is required in selecting the hole locations.
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9/64” Holes drilled around hatch |
Foam placed around the deck, and
corresponding hatch holes drilled through deck |
Once the
hatch holes have been drilled, test fit the hatch on the deck to ensure all
of the holes line up on the deck ledge. Then place the hatch on the deck and
use the hatch holes as guides to drill the corresponding holes around the
deck ledge. Photo 6 shows the finished deck ledge with the hatch holes
drilled around the perimeter. It should be noted that at this point in the
project, the DuBro Foam Tape has not yet been applied.
Now that the hatch and deck have been drilled, it remains to glue the
blindnuts - already pressed into the plywood squares - underneath the deck
ledge. The plywood squares make it easy to attach the blindnuts under the
ledge. Simply test fit the plywood squares, with blindnuts installed, to
ensure they line up with the deck ledge holes and then glue them in place
using medium CA. Photos 7 and 8 show some of the blindnuts glued in place
under the deck ledge. As mentioned in section 3, it may be necessary to sand
and file one side of the blindnuts and plywood pieces to avoid having the
edge protrude into the deck opening. This is particularly true for the
hydroplane model since it has a “lip” under the deck edge (see Photo 8).
Once all of the wood pieces with blind nuts have been installed, test fit
the hatch on the deck and screw it in place to ensure all of the holes and
nuts line up properly. If required, enlarge the hatch holes slightly to
ensure a good fit of the hatch onto the deck.
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| Photo 7: Small plywood
supports and blindnuts glued to the underside
of the deck ledge (Monohull) |
Photo 8: Small plywood
supports and blindnuts glued under deck ledge (Hydroplane) |
5: FINAL STEPS:
Remove the hatch and apply the DuBro foam tape around the perimeter of the
deck ledge as shown in Photo 6. The foam tape provides a waterproof seal
when the hatch is screwed onto the deck. In this example, the deck ledge was
painted in advance of applying the foam tape to make the final hull painting
easier. After the foam tape has been applied, cut small openings in the tape
to allow the 6-32 screws to pass through the foam and into the blindnuts. It
is recommended to submerge the sealed hull and hatch in the bathtub to test
for leaks and determine how tight to screw down the hatch for a good seal.
Typically, the hatch only needs to be tight enough to slightly compress the
foam tape and hold the screws in place so they don’t loosen when the boat is
in operation. If leaks are observed around the hatch holes, use flat washers
with the hatch screws to seal these openings.
Lastly, use small cardboard or plastic retaining washers on the underside of
the screws to hold them in place in the hatch – see Photo 9. This makes it
easier to handle the hatch and avoids lost screws. These plastic retaining
washers happen to be the same size as those found on household 110V duplex
receptacles and light switches, so they can be purchased from any hardware
store.
You now have a waterproof hatch that is easy to install and remove, and
looks good on your FE boat.
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Photo 9: Plastic retaining washers Installed |
Photo 10: The finished hatch
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Full
PDF Document on Screw-Down Boat Hatches – An Alternative to Tape!
By Ralph von Eppinghoven
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