Bamboo Propellers

On May 27, 6:25*pm, Brian Whatcott wrote:

Brian said...

Ha!
....and later on...

Amazing!
--------------------------------------------------------------------------------

Well... Ha! right back atchew :-)
(and tanks for the URL's)

I first mentioned the 'Roll Yer Own RPV' 'way back when sometime...
back before the Big C came to call. The typical response was from
Good Ol' Boyz telling me all the reasons why it couldn't be true,
which generally boiled down to the fact they'd never heard of it
before.

Among the reasons why it wouldn't work was the 'fact' that every one
of those 'mystery' aircraft penetrating American air space was being
tracked by FLIR-equipped helicopters, so that by the mystery airplane
touched down, there was a reception committee there to meet it.

Not so. Because APPARENTLY each of those mystery airplanes was NOT
carrying anything besides extra fuel. So let's say ten drones cross
the border. Their flight path takes them through a populated area
where they are VISUALLY checked to see if they are being followed. If
they are, the flight path is re-programmed and eventually returns home
without ever touching down. Or it may be carrying external tanks,
dropped near downtown Sage, California. (Lookitup :-)

The guy on the ground with the sound-tracking FLIR is the 'cleaner.'
His job is to look for anything-anyone following the Mystery
Airplane. If the answer is 'yes' it simply turns around and goes
home. But the truth is, we don't have enough aerial assets to track
each Mystery Airplane 100% of the time.

But the very BEST of the Good Ol' Boy reasons is that Messicans just
aren't smart enough to run 'something like that.' Meaning the Good
Ol' Boys aren't bright enough to appreciate the problem.

Personally, I think it's funny as hell :-) Because as soon as someone
underestimates the problem, they've lost the war by default.

-R.S.Hoover

On Tue, 26 May 2009 10:03:08 -0700 (PDT), Veeduber
wrote:

To All,

As a point of interest, in the 1970's I was able to buy all the
STRAIGHT-GRAINED maple I wanted at bargain prices because (here it
comes) the straight-grained varieties ( sometimes called 'sugar
maple' ) was LESS desirable for furniture than the 'curly' varieties.
The same was true for mahogany; with straight, hard-grained mahogany
did not have as much 'figure' and was therefore used only for the
hidden portions of the furniture. Which lead to.... Bob, the Garbage
Thief.

Back in the Day, whenever that was, people used to get rid of unwanted
furniture by simply sitting it out by the road-side on Garbage Day
(whenever THAT was). I found that couches and chairs USUALLY had
frames made of straight-grained maple or oak, often in pieces long
enough for making a prop-blank. After dismantling the piece I would
return the residue to the road-side (something we are not allowed to
do today). And WOOD residue went into the stove.

Unless you were seriously poor you would never consider such sources
for hardwood, partly because of the difficulty in removing the
zillions of pneumatically-installed staples and nails. But when you
can't allow your hobby to financially intrude on your family's
welfare, you treat your time as having zero-value when involved in the
recovery of wood from old furniture, tables and what-have-you.

-R.S.Hoover

bob you are amazing.
(in a very positive way)

Stealth Pilot

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

On Wed, 27 May 2009 03:54:38 GMT, Jerry Wass
wrote:



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.)

the actual examples of english longbows that remain were recovered
from the holds of the Mary Rose. no other *actual* medieval english
longbows existed. the making of them was pretty well lost to hearsay.
they are made from Yew wood exactly as you describe for the american
indians.
most are apparently roughly shaped but I think that that was so that
the wood behaved as needed.
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