Bamboo Propellers

Stealth Pilot wrote:
On Mon, 25 May 2009 12:32:15 -0500, Charles Vincent
wrote:
I know the British preferred mahogany for their propellers, but as I
recall, mahogany had some serious knocks as prop material. I can't
bring them to mind at the moment though.

Charles

mahogany was used by the brits, to quote lattimer-needhams engineering
text,
"mahogany is largely employed in the manufacture of airscrews, and the
variety that grows in honduras is favoured for that class of work. The
suitability of honduras timber is due chiefly to the fact that its
liability to shrink (after efficient seasoning) is only very slight
and that it possesses particularly satisfactory glue retaining
qualities. it is a strong, hard, straight grained wood and is not
difficult to work."

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

Ron Webb wrote:
I lived on the island of Guam from 1985 thru 1988. One of the things I noted
there was that if you went down to the lumber yard, the 2x4's you got would
be straight grained Phillipine mahogany. And it was cheap!

I've sometimes wondered if it would be profitable to travel to Guam, or the
Phillipines, or wherever, and put together a big platform consisting of
nothing but the most valuable wood at hand, then mount a GPS, a satellite
phone, and a set of sails controlled by computer. Tell the thing to sail
itself to L.A. or wherever, and call me when you're close...then sell all
that beautiful wood...



What an imaginative idea. I know there is a certain class of folks who
already make surface submersibles (only the snorkels show...)
but they keep them crewed, and run a diesel to get them to the US with
their valuable aromatic or sensory modification goods.

Brian W

Charles Vincent wrote:
Stealth Pilot wrote:
On Mon, 25 May 2009 12:32:15 -0500, Charles Vincent
wrote:
I know the British preferred mahogany for their propellers, but as I
recall, mahogany had some serious knocks as prop material. I can't
bring them to mind at the moment though.

Charles

mahogany was used by the brits, to quote lattimer-needhams engineering
text,
"mahogany is largely employed in the manufacture of airscrews, and the
variety that grows in honduras is favoured for that class of work. The
suitability of honduras timber is due chiefly to the fact that its
liability to shrink (after efficient seasoning) is only very slight
and that it possesses particularly satisfactory glue retaining
qualities. it is a strong, hard, straight grained wood and is not
difficult to work."

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

I seem to recall that just about any straight grain wood - hardwood or
softwood or both laminated together will do the job. Some protection
against leading edge erosion is desired - used to be brass, now could be
fiberglass. The slender trailing edge would be a good candidate for a
hardwood lamina in my view. Wooden pros are MUCH kinder to cranks than
glass or metal.

Brian W

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?

Charles Vincent wrote:
Stealth Pilot wrote:
On Mon, 25 May 2009 12:32:15 -0500, Charles Vincent
wrote:
I know the British preferred mahogany for their propellers, but as I
recall, mahogany had some serious knocks as prop material. I can't
bring them to mind at the moment though.

Charles

mahogany was used by the brits, to quote lattimer-needhams engineering
text,
"mahogany is largely employed in the manufacture of airscrews, and the
variety that grows in honduras is favoured for that class of work. The
suitability of honduras timber is due chiefly to the fact that its
liability to shrink (after efficient seasoning) is only very slight
and that it possesses particularly satisfactory glue retaining
qualities. it is a strong, hard, straight grained wood and is not
difficult to work."

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


Surely you've seen some native Indian bows (old ones) the wood is split
from a tree so that the heart (dark wood) and the lighter (outside,sap
wood ) both appear in the bow..The dark is placed on the inside of the
curve because it is much higher in compressive strength..The back side
is the sap wood which is much higher in tensile strength.

Pore old uneducated indians--didn't know much did they G --also
Bois= wood d'Arc= of the arc or bow. Jerry--(used to live on
Bois d'Arc in ElPaso.)

On May 26, 6:17*pm, Brian Whatcott wrote:

What an imaginative idea. I know there is a certain class of folks who
already make surface submersibles (only the snorkels show...)
but they keep them crewed, and run a diesel to get them to the US with
their valuable aromatic or sensory modification goods.
----------------------------------------------------------------------------------------------------

Dear Brian (and the Group),

If you are familiar with trans-Atlantic flights of model airplanes...
or of the campus-to-campus flights of model airplanes buzzing along a
carefully pre-planed flight-path between Miami and Boston, the
following will not come as a surprise.

The original Varieze was meant to be powered by a VW... and would have
been far more successful, in my opinion, had they used my engine
instead of Ted's. Water under the bridge and so forth. However, some
diligent gentlemen from south of the border have apparently been
making flights north of it in un--manned Variezes using VW engines
with the prop on the proper end of the crank. One of their flight
paths is said to be from the strip at the LA Bay junction to one of
the WWII air strips out in the Mohave, where control is transferred to
a local transmitter for landing. Once on the ground the cargo is
removed, the bird refueled and sent back south. Another flight path,
said to be the original, was from a strip in Sinaloa to a stretch of
highway in Arizona, the move to Baja and the Mojave the result of
inter-tribal warfare.

All just Hobby Shop rumor, of course. Or rather the product of
several hundred rumors about home-built RPV's heard but not seen as
they putter their merri way back & forth at zero altitude, delivering
Ami-Rica's most popular yarb at a hundred keys per trip. And if they
lose one now & then it's no big deal. VW engines are cheap and so are
N7EZ's if you don't have to worry about a canopy nor any human flight
controls.

-R.S.Hoover

On May 26, 6:21*pm, Brian Whatcott wrote:

I seem to recall that just about any straight grain wood - hardwood or
softwood or both laminated together will do the job.
---------------------------------------------------------------------------------------------

Dear Brian,

Sorta-hard softwoods such as fir, do just fine with the VW. Trailing
edge can be relatively blunt and still get the job done. Leading edge
-- the outboard foot or thereabouts -- needs to be glassed then fitted
with a slippery tape. But rpm is definitely a factor. Use the proper
cam on a seriously over-square engine and a tip-speed of no more than
880fps, you can even use spruce... but ONLY if you are running a
flywheel. Maple remains the best choice, not so much for its
durability but because of its MASS. Turns the veedub into a real
chugger.

Wait until you see what Bruce King & Steve Bennett have come up with
for the BK1.3. One of the engine options is a surprisingly light-
weight package that's all wrong... according to the instant
experts :-)

-R.S.Hoover

On Wed, 27 May 2009 00:28:42 -0700 (PDT), Veeduber
wrote:
...However, some
diligent gentlemen from south of the border have apparently been
making flights north of it in un--manned Variezes...

Hmmm, "back in the day" I recall discussing the possibility of such
flights in a VariEze, which would naturally have a very low radar
signature. The idea was to paint it black, except for weird
phosphorescent shapes on the underside, and a small black light
mounted under the aircraft to light them up. The idea was that even
if anyboby _did_ report such a strange apparition crossing the border,
he wouldn't be believed...

-Dana
--
When you get it right
mighty beasts float up into the sky
When you get it wrong
people die

-Roger Bacon (c1384)

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

Veeduber wrote:
On May 26, 6:17 pm, Brian Whatcott wrote:
What an imaginative idea. I know there is a certain class of folks who
already make surface submersibles (only the snorkels show...)
but they keep them crewed, and run a diesel to get them to the US with
their valuable aromatic or sensory modification goods.
----------------------------------------------------------------------------------------------------

Dear Brian (and the Group),

If you are familiar with trans-Atlantic flights of model airplanes...
or of the campus-to-campus flights of model airplanes buzzing along a
carefully pre-planed flight-path between Miami and Boston, the
following will not come as a surprise.

The original Varieze was meant to be powered by a VW... and would have
been far more successful, in my opinion, had they used my engine
instead of Ted's. Water under the bridge and so forth. However, some
diligent gentlemen from south of the border have apparently been
making flights north of it in un--manned Variezes using VW engines
with the prop on the proper end of the crank. One of their flight
paths is said to be from the strip at the LA Bay junction to one of
the WWII air strips out in the Mohave, where control is transferred to
a local transmitter for landing. Once on the ground the cargo is
removed, the bird refueled and sent back south. Another flight path,
said to be the original, was from a strip in Sinaloa to a stretch of
highway in Arizona, the move to Baja and the Mojave the result of
inter-tribal warfare.

All just Hobby Shop rumor, of course. Or rather the product of
several hundred rumors about home-built RPV's heard but not seen as
they putter their merri way back & forth at zero altitude, delivering
Ami-Rica's most popular yarb at a hundred keys per trip. And if they
lose one now & then it's no big deal. VW engines are cheap and so are
N7EZ's if you don't have to worry about a canopy nor any human flight
controls.

-R.S.Hoover

Ha! I had heard about the trans-Atlantic trips (and maybe some
Trans-Pacific endeavors too,) but the inter campus express had passed me by.
But in that connection, I can tell you about a hardware equivalent to
the hugely successful Open Software movement, GNU, copyleft, and all
that good stuff.
It focusses on a little microcontroller card called the Arduino,
of which the current implementation is called the Duemilanuove
(Italian for "2009") It is about 2 X 2 inches.
This has attracted a large active following from
people who make things. It has a USB socket for power and downloading.
A FREE soft development capability on your PC. Hundreds or thousands
of applications in software - available cards for expanders and whatever.
And the good news is - the entry price for the whole shebang is under
$50 - and you will be testing an on board flasher you programmed and
compiled, on the first day you get it. It has AtoDs DtoAs, DOs DIs
a k or two of memory for code, etc, etc....
The reason I gushed on about this is that I stumbled on it when reading
about a drone (RPV) autopilot, wing leveler, GPS waypoint follower -
with smooth switchover to radio control. This is the Ardupilot.
Around $100 basic.

Less than $500 gets the controller, the servoes the GPS the
application, the custom PCB, an IR horizon wing leveler and pitch
controller. Oh, and the model electric plane and RC gear to try it out with.

First batch sold out....
http://blog.makezine.com/archive/200...le_uav_co.html
or in tiny format:
http://tinyurl.com/pqz2ev

Ardupilot home page
http://diydrones.com/profiles/blog/s...ogPost%3A44814
or in tiny format:
http://tinyurl.com/5g5gho

Amazing!

Brian W