Bamboo Propellers

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

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.
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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