Hatches - Strong Miter Joints
 

I am at the planning stage of replacing some deck hatches on a sailing boat.
The framework is mitered, to prevent endgrain being open to the sea, but as
these are stepped on they also need to be strong.

I see the altenatives being miters with routed slots for loose tongues, or
mitered mortice and tennons. Anyone have any experience with this type of
work?

Thanks.

BernardR

"Bernard Randall" wrote in message
...
I am at the planning stage of replacing some deck hatches on a sailing
boat.
The framework is mitered, to prevent endgrain being open to the sea, but
as
these are stepped on they also need to be strong.

I see the altenatives being miters with routed slots for loose tongues, or
mitered mortice and tennons. Anyone have any experience with this type of
work?

A mitered glued edge is not too strong, in my experience. Could it be a
solution to build the framework with whatever strong joints you want and
then cover it with a thin (3mm / 1/8") layer with mitered edges?

Meindert

Dove tails.
I know about end grain, but hatches are easy to revarnish or paint as
needed.....The hatch is in the open air so does not suffer "permanant
wet"....
And good dove tails are strong enough to stand on (assuming reasonable
scantlings)
"Bernard Randall" wrote in message
...
I am at the planning stage of replacing some deck hatches on a sailing
boat.
The framework is mitered, to prevent endgrain being open to the sea, but
as
these are stepped on they also need to be strong.

I see the altenatives being miters with routed slots for loose tongues, or
mitered mortice and tennons. Anyone have any experience with this type of
work?

Thanks.

BernardR

Bernard Randall wrote:

I am at the planning stage of replacing some deck hatches on a sailing
boat. The framework is mitered, to prevent endgrain being open to the sea,
but as these are stepped on they also need to be strong.

I see the altenatives being miters with routed slots for loose tongues, or
mitered mortice and tennons. Anyone have any experience with this type of
work?

Thanks.

BernardR

Have you considered mitered half-lap joints.

An illustration is 1/3 of the way down the page.

http://www.woodworking-online.com/chapter6/2.html
--
_______m___õ¿~___m_________________________
"Life is not measured by the number of breaths we take,
but by the moments that take our breath away".
--George Carlin--

Meindert Sprang wrote:

"Bernard Randall" wrote in message
...

I am at the planning stage of replacing some deck hatches on a sailing

boat.

The framework is mitered, to prevent endgrain being open to the sea, but

as

these are stepped on they also need to be strong.

I see the altenatives being miters with routed slots for loose tongues, or
mitered mortice and tennons. Anyone have any experience with this type of
work?


A mitered glued edge is not too strong, in my experience. Could it be a
solution to build the framework with whatever strong joints you want and
then cover it with a thin (3mm / 1/8") layer with mitered edges?

Meindert


Interlocking dovetails would be best in wood, sealed with paint,
whatever. For ultimate strengh, metal corner reinforcements, or
moulded solid glass fiber construction.

Ultimately, I would prefer a dark tinted plexiglass cover, with
gaskets and a moulded glass or aluminum edge frame resting on the
deck, with bugscreen and ventilation arrangenets integral. Perhaps a
modified scrap aluminum storm door frame?

Terry K

"Terry Spragg" wrote in message
...
Meindert Sprang wrote:

"Bernard Randall" wrote in message
...
I see the altenatives being miters with routed slots for loose tongues,
or
mitered mortice and tennons. Anyone have any experience with this type
of
work?


A mitered glued edge is not too strong, in my experience. Could it be a
solution to build the framework with whatever strong joints you want and
then cover it with a thin (3mm / 1/8") layer with mitered edges?

Meindert

You are correct that a plain glued miter joint has little mechanical
strength. The joint I am refering to has been around for a long time but I
haven't had the need for it before.


Interlocking dovetails would be best in wood, sealed with paint,
whatever. For ultimate strengh, metal corner reinforcements, or
moulded solid glass fiber construction.

The top framework of the hatches are 1 1/2" wide by 7/8" thick, without the
endgrain, the correct joint would be mortice and tennons.

Ultimately, I would prefer a dark tinted plexiglass cover, with
gaskets and a moulded glass or aluminum edge frame resting on the
deck, with bugscreen and ventilation arrangenets integral. Perhaps a
modified scrap aluminum storm door frame?

Sorry I didn't make it clear in the original post, these are cockpit hatches
which double as the seats, and cover the gas, rope and general storage
areas. The 'filling' of the hatch framework is marine ply with layed deck
veneer.

Bernard R

Terry K

One approach is to clean up the old hatches, glue up any open joints, and
sand the insides well. Then turn the hatch upside down and fiberglass all
inside surfaces. I used one layer of 1.5 oz. matt followed by three layers
of 8 oz. cloth. Trim the glass around the edges of the hatch and varnish
inside and out. My hatches are 20 years old and have had no joint problems.
Another option is to cut away most of the top, tape a waxed piece of plywood
over the outside of the cutout, then glass the insides. When the plywood is
removed the fiberglass will form a translucent window.

"Bernard Randall" wrote in message
...
I am at the planning stage of replacing some deck hatches on a sailing
boat.
The framework is mitered, to prevent endgrain being open to the sea, but
as
these are stepped on they also need to be strong.

I see the altenatives being miters with routed slots for loose tongues, or
mitered mortice and tennons. Anyone have any experience with this type of
work?

Thanks.

BernardR

On Thu, 2 Dec 2004 19:22:03 -0800, "John Holtrop"
wrote:

One approach is to clean up the old hatches, glue up any open joints, and
sand the insides well. Then turn the hatch upside down and fiberglass all
inside surfaces. I used one layer of 1.5 oz. matt followed by three layers
of 8 oz. cloth. Trim the glass around the edges of the hatch and varnish
inside and out. My hatches are 20 years old and have had no joint problems.
Another option is to cut away most of the top, tape a waxed piece of plywood
over the outside of the cutout, then glass the insides. When the plywood is
removed the fiberglass will form a translucent window.

"Bernard Randall" wrote in message
...
I am at the planning stage of replacing some deck hatches on a sailing
boat.
The framework is mitered, to prevent endgrain being open to the sea, but
as
these are stepped on they also need to be strong.

I see the altenatives being miters with routed slots for loose tongues, or
mitered mortice and tennons. Anyone have any experience with this type of
work?

Thanks.

BernardR




Any half lap mitre joint will still leave half of the end grain
showing on one side of the joint as will a dovetail - but dovetails
are used where one side of the frame is carried by the other side, I'm
not sure if that is the case here. If mitred tenons are used the tenon
must not be a through tenon or you still get end grain showing, but
will give you a strong joint - not easy to form though. A mitre with a
biscuit or a loose tongue will not be so strong but is probably the
simplest.

However, if you cover the wood with epoxy I don't see what long term
problems you would have by exposing some end grain. It's just a
question of maintenance and as James says it is not as if the joints
are exposed too much.