Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??

wrote in message
oups.com...
Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??


Laminate. Thin, dry sections. Wood that's green, or air dry is always a
better bet for steaming than something that's been through the kiln.

wrote:
Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??


My understanding, is that steam bending works best on *green* wood.

You might have better luck doing bend lamination with matching scarf
joints to build up the desired thickness. Issue here would be that the
circumference would change upon each lamination application, so you'd
have to cut laminations longer than needed and test fit them to get the
appropriate lengths.

~Mark.

wrote in message
oups.com...
Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a
0.381m(15")
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??


As others have suggested, I too would use a bent lamination technique to
make the porthole liners. If for no other reason, they will be very stable
in a barge environment.

Basic bent lamination technique:
Slice the wood into thin strips 1/16" -1/8" (1.5mm-3mm)
Glue and wrap the strips around a form, (use a slow setting glue)
Clamp in place.
Unclamp and machine to finished size, sand and apply finish.

Dave



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wrote in message
oups.com...
Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??

Steaming is a big and technical subject. Curved work in general and
boatbuilding are even vaster, so nobody will be able to tell you how to do
this or even run through the options in a quick ng reply.

Mahogany is not a wood for steam bending. Bending requires a strait grain
and mahog has too much cross grain. Further to that i do not know how you
would intend to make a complete ring of timber. Are you steaming pieces and
then scarfing them together? If you laminate you might be advised to buy
structural veneers rather than trying to cut them.

Tim w

wrote in message
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

After attending a recent seminar at Lee Valley Tools conducted by Michael
Fortune and watching him bend wood, I'm convinced almost any radius within
reason can be obtained. I'm not that sure Mahogany is the best wood since
straight grained wood is the best for steam bending, but you should be able
to find something suitable. My first suggestion is that you read up a bit on
bending wood.
http://www.leevalley.com/wood/page.a...=1,45866,45867

There's also another route you might consider for these portholes. Bendable
Lauan also known as Bendable Plywood or "Wiggle Board", (information also
courtesy of Mr. Fortune) might meet your needs. You could laminate several
layers together to obtain your desired thickness. I've provided one sample
picture of it in the link below. It does come in longer lengths (at least
96") than listed on the website.

http://www.vandykes.com/product/02007822/

I'm guessing that mahogany veneer would need to be 1/16" at most to agree
to an 8" radius. Experimentation is needed.
As an alternative, turn the veneer such that the bend is cross-grain and
laminate. A couple of laminations of light glass cloth can supply
cross-grain strength.
Vacuum bagging would be a big wrote in message
oups.com...
Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??

wrote:
Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??

Try this: http://www.wcha.org/tidbits/steamfaq.html

wrote:
Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??


Mahogany is not a good wood to bend. It's almost impossible to steam
bend anything close to that radius. The rig you would have to make would
be dangerous. According to my Fine Woodworking Bending Wood book the
best radius you would see for 1" thick mahogany is 32" to 36".

Even bent laminations are tricky with mahogany. If you want to attemp
this keep the strips really thin 3/32" to 1/16". Cut lots of extras,
you'll need them. Bend SLOWLY. Have both an inside and outside form. My
guess is 1/2 to 3/4 of them will break. Use epoxy if you do this. I
prefer a nice slow setting gel type.

The other choice is cutting a circle. This would be the most wasteful,
but might be your best bet.

The advantage to bending wood over cutting curved forms is tensile
strength. Grain orientation (and therefor tensile strength) is
inconsistent on a curved cut form, where a bent form will have fairly
consistent grain orientation. IMO A pothole liner would not need need
the tensile strength a bent piece of wood would give. It would be
supported on all sides, unless I'm missing something.


The other best bet option. Choose a contrasting wood that does bend well
like Ash, White Oak, or Red Oak. Walnut and Cherry will also bend well.


Christian

Christian Brink wrote:

wrote:
Hi,
I need to make some porthole liners for a barge and I was thinking of
steaming some wood strips. Size is approx 1.15m long - it is a 0.381m
diameter porthole - 60mm wide and 6 - 8 mm thick. I was thinking of
using mahogany or similar dark hard wood.

Can I bend steamed mahogany to this radius?? - or any other
suggestions??


Mahogany is not a good wood to bend. It's almost impossible to steam
bend anything close to that radius. The rig you would have to make would
be dangerous. According to my Fine Woodworking Bending Wood book the
best radius you would see for 1" thick mahogany is 32" to 36".

Even bent laminations are tricky with mahogany. If you want to attemp
this keep the strips really thin 3/32" to 1/16". Cut lots of extras,
you'll need them. Bend SLOWLY. Have both an inside and outside form. My
guess is 1/2 to 3/4 of them will break. Use epoxy if you do this. I
prefer a nice slow setting gel type.

The other choice is cutting a circle. This would be the most wasteful,
but might be your best bet.

The advantage to bending wood over cutting curved forms is tensile
strength. Grain orientation (and therefor tensile strength) is
inconsistent on a curved cut form, where a bent form will have fairly
consistent grain orientation. IMO A pothole liner would not need need
the tensile strength a bent piece of wood would give. It would be
supported on all sides, unless I'm missing something.


The other best bet option. Choose a contrasting wood that does bend well
like Ash, White Oak, or Red Oak. Walnut and Cherry will also bend well.

I'd avoid ash or red oak on a boat--you can pretty much count on everything
being wet even on a barge so decay resistance is an issue--white oak or
walnut would be much better bets IMO. Cherry I'm not sure about, I'd have
to look up the decay resistance figures.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)