Bamboo Propellers

Charles Vincent wrote:

I found the reference. It was in Martin Hollman's Modern Propellor and
Duct Design book. It just notes that mahogany tends to splinter easily
and is therefore not a good choice. In any event, mahogany doesn't
grow here in Texas, at least anywhere near me. Bois dArc does though
and has ridiculous strength in compression - double mahogany (I have a
house built on Bois D Arc stumps, the tree is so ugly, termites won't
touch it) I have the compressive strength numbers since it is a common
foundation material, but do not have the normal engineering values for
the rest. I need to find them.

Charles

Are you making propellers from mesquite?

cavelamb wrote:
Charles Vincent wrote:

I found the reference. It was in Martin Hollman's Modern Propellor
and Duct Design book. It just notes that mahogany tends to splinter
easily and is therefore not a good choice. In any event, mahogany
doesn't grow here in Texas, at least anywhere near me. Bois dArc does
though and has ridiculous strength in compression - double mahogany (I
have a house built on Bois D Arc stumps, the tree is so ugly, termites
won't touch it) I have the compressive strength numbers since it is a
common foundation material, but do not have the normal engineering
values for the rest. I need to find them.

Charles

Are you making propellers from mesquite?

Nope. Hard to find a section of mesquite with straight grain around
here. I have heard of a furniture maker around Austin using mesquite,
but he is using mesquite growing on river banks, as it grows taller and
straighter. I was musing on the applicability of Bois DArc, or Bodark
colloquially. Used by the native for making bows, and by the early
settler for fence posts ( there was once a thriving market in Texas for
bodark seeds and plenty of the material was sent north for fences there
as well. This was just in line with Bob Hoover's "use what is found
locally and cheap" approach.

Charles

On Wed, 27 May 2009 11:42:23 -0500, Charles Vincent
wrote:

cavelamb wrote:
Charles Vincent wrote:

I found the reference. It was in Martin Hollman's Modern Propellor
and Duct Design book. It just notes that mahogany tends to splinter
easily and is therefore not a good choice. In any event, mahogany
doesn't grow here in Texas, at least anywhere near me. Bois dArc does
though and has ridiculous strength in compression - double mahogany (I
have a house built on Bois D Arc stumps, the tree is so ugly, termites
won't touch it) I have the compressive strength numbers since it is a
common foundation material, but do not have the normal engineering
values for the rest. I need to find them.

Charles

Are you making propellers from mesquite?

Nope. Hard to find a section of mesquite with straight grain around
here. I have heard of a furniture maker around Austin using mesquite,
but he is using mesquite growing on river banks, as it grows taller and
straighter. I was musing on the applicability of Bois DArc, or Bodark
colloquially. Used by the native for making bows, and by the early
settler for fence posts ( there was once a thriving market in Texas for
bodark seeds and plenty of the material was sent north for fences there
as well. This was just in line with Bob Hoover's "use what is found
locally and cheap" approach.

Charles

It always pays to pick up the dregs from a pranged propeller and look
at what has actually let go as opposed to what you'd think would let
go.

I did a quiet post mortem on a prop made with curly wood in part of
the blades. wood in the hub was straight but it was quite curly in
sections of the blades. all for the reject bin you'd think.

well when that prop was shattered in a wheels up landing of the
sidlinger hurricane it was on, not one part of the curly grain had let
go. no glue breaks in the curly grain. no breaks of any type in the
curly grain area. all the breaks were in the adjoining straight
grained sections at radiuses either side of the wrong grained wood.

it showed me again that doing it often shows you that the conventional
wisdom in aviation is either wrong or was formed when the
constructional conditions were quite different from what we are doing
today. as veedubber says dont be afraid to do and learn from *current*
experience.

more wood is usable than you'd think.
Stealth Pilot

"Stealth Pilot" wrote

well when that prop was shattered in a wheels up landing of the
sidlinger hurricane it was on, not one part of the curly grain had let
go. no glue breaks in the curly grain. no breaks of any type in the
curly grain area. all the breaks were in the adjoining straight
grained sections at radiuses either side of the wrong grained wood.


If the curly wood is in the middle of the prop blank, or carved section of the
blade, it is only taking up the centripetal forces (I know, they don't exist)
and not any bending load. It is only serving to hold the outer sections away
from each other, like the web in an I beam.
--
Jim in NC

On Thu, 4 Jun 2009 20:32:31 -0400, "Morgans"
wrote:


"Stealth Pilot" wrote

well when that prop was shattered in a wheels up landing of the
sidlinger hurricane it was on, not one part of the curly grain had let
go. no glue breaks in the curly grain. no breaks of any type in the
curly grain area. all the breaks were in the adjoining straight
grained sections at radiuses either side of the wrong grained wood.


If the curly wood is in the middle of the prop blank, or carved section of the
blade, it is only taking up the centripetal forces (I know, they don't exist)
and not any bending load. It is only serving to hold the outer sections away
from each other, like the web in an I beam.

centripetal forces exist.
it is centrifugal forces that dont.
Stealth Pilot