Pills & Propellers

On Nov 23, 9:35*am, " wrote:
On Nov 23, 3:32*am, Stealth Pilot
wrote:

something for Veedubber to explore is whether epoxy saturation of the
hub area could increase the crush strength of readily available softer
woods.
laminating hard faces wont do it because they just transfer the
pressure unabated to the soft core and crush it.
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I don't know if just saturation would work. *As Richard points out, on
healthy wood epoxy hardly soaks in at all. *But if your hub has an
accurately made center-bore and if you make or buy drive lugs, you can
auger out the area where the drive lugs would seat and fill that area
with JB WELD or other filled epoxy. *You have to wax the drive-lugs
and the bolts, and you need to get the filled epoxy deep into the
holes you've made (you don't want any of it to squeeze-out between the
prop and the hub), you'll end up with a softwood prop capable of being
torqued to hardwood specs. *This is usually done as a repair
procedure. *Just look at the clamping ring. *If it has been drawn into
the wood by any amount you'll probably find charring between the prop
and the hub. *Soaking the charred portion with epoxy will harden it
but the real problem is that the softwood prop simply lacks the
required compressive strength. *That's where the filled epoxy comes
in. *This also works for the valley created by the clamping ring. *You
can use a WIRE BRUSH on a drill-motor to get down to clean, bare wood
then brush on a thinned coat of epoxy to act as a primer. *Let it get
tacky then FILL the valley with a filled epoxy... such as JB WELD. *It
will take a couple of tubes to fill a serious 'valley.' *After it
cures you can sand it flush. *Just make sure you keep it flat. *If it
has been varnished (as opposed to epoxied) you may have to do the wire-
brush trick over the entire surface so you can apply a finish-coat of
epoxy once you've returned the surface to truth. *(Tracking will tell
you if you've got it right.)

There's a lot of elderly VP's and other basic designs that, despite
their age, have accumulated relatively few hours, such as fifty hours
in fifteen years -- stuff like that. (And most of that will have been
accumulated during the first year or two.) * The sale of such
airplanes is often tied to an estate sale -- the builder has died and
there's no one who can give you accurate information about the
condition of such things as the prop, engine and landing gear. *And
they may not want you to go digging into it. *But if you're allowed to
dig (or just remove the prop, for that matter) you'll often find
charring, especially if they've glued on a spacer to allow the prop to
clear the #3 exhaust stack.

At a real auto-parts store (as opposed to a franchise, such as Pep
Boys, et al) in the 'Dorman' trays, you will find 'drive lugs' for
about six bits as opposed to the $18 or $20 wanted for an 'aircraft'
drive lug. *They don't call it a drive-lug of course -- it is a brake
part, I think for early Chrysler products.

-R.S.Hoover

I don't think epoxy saturation of a soft prop would safely, even
if we could get the whole hub saturated to its full depth. The hub
would get hard enough, certainly, but the blade roots would still be
soft and the flexing of soft wood is therefore concentrated at that
point instead of tapering off into the hub as it should. Saturating
the whole prop would stiffen it without increasing its tensile
strength. Brittleness would result, along with much more weight and
cost. Better to use a hardwood in the first place.
Pine is soft. It doesn't have the tensile strength of
hardwoods. Concentrating stresses is asking for trouble. We've seen
this in several older strut-braced high-wing aircraft designs where
the wooden spars are plated with birch or mahogany ply at the strut
attach points, and the spruce spars suffer compression failures at the
ends of the plates on the top of the spar.
There are so many ways of introducing "unintended consequences"
when we "fix" something. If I was to build a prop (and I plan to) I'll
be using a wood that's worked for many people for many years.
Something like hard Canadian Maple.

Dan

There is a method I have done thought experiments on, in which a wood
part could be soaked through with methyl methacrylate monomer, which
will penetrate to the deepest cell structure, and then activated
chemically to cross link. Something of this nature could possibly be of
use. Methyl methacrylate monomer will cross link under UV such as
direct sunlight, which I have used (taking several days to start the
reaction). You would need to maintain the saturation in a closed
container since the monomer is quite volatale.

A.L.
Phoenix

wrote:

There is a method I have done thought experiments on, in which a wood
part could be soaked through with methyl methacrylate monomer, which
will penetrate to the deepest cell structure, and then activated
chemically to cross link. Something of this nature could possibly be of
use. Methyl methacrylate monomer will cross link under UV such as
direct sunlight, which I have used (taking several days to start the
reaction). You would need to maintain the saturation in a closed
container since the monomer is quite volatale.

A.L.
Phoenix


I think I'd rather just buy a good prop from Tennessee Props and
go fly...


--

Richard

(remove the X to email)

The democracy will cease to exist when you
take away from those who are willing to work
and give to those who would not.

Thomas Jefferson

"cavelamb himself" wrote in message
...
wrote:

There is a method I have done thought experiments on, in which a wood
part could be soaked through with methyl methacrylate monomer, which
will penetrate to the deepest cell structure, and then activated
chemically to cross link. Something of this nature could possibly be of
use. Methyl methacrylate monomer will cross link under UV such as
direct sunlight, which I have used (taking several days to start the
reaction). You would need to maintain the saturation in a closed
container since the monomer is quite volatale.

A.L.
Phoenix


I think I'd rather just buy a good prop from Tennessee Props and
go fly...

OK I can find the definition and properties of: Methyl methacrylate monomer
, but what is that word: "FLY"? Is the other word Fishing? My helicopter
has been down for sometime now waiting for me to quit "Digging Dirt" and
finish a small "Put Back" job.

Stu

On Sun, 23 Nov 2008 14:26:41 -0800, "Stuart Fields"
wrote:


"cavelamb himself" wrote in message
...
wrote:

There is a method I have done thought experiments on, in which a wood
part could be soaked through with methyl methacrylate monomer, which
will penetrate to the deepest cell structure, and then activated
chemically to cross link. Something of this nature could possibly be of
use. Methyl methacrylate monomer will cross link under UV such as
direct sunlight, which I have used (taking several days to start the
reaction). You would need to maintain the saturation in a closed
container since the monomer is quite volatale.

A.L.
Phoenix


I think I'd rather just buy a good prop from Tennessee Props and
go fly...

OK I can find the definition and properties of: Methyl methacrylate monomer
, but what is that word: "FLY"? Is the other word Fishing? My helicopter
has been down for sometime now waiting for me to quit "Digging Dirt" and
finish a small "Put Back" job.

Stu


Stu. helicopters are like austers. every auster owner needs to own
another aircraft. ....the one he flies while the auster is being
repaired.

it is a well known fact :-)
Stealth Pilot

On Nov 23, 2:19*pm, cavelamb himself wrote:


The democracy will cease to exist when youtake away from those who are willing to workand give to those who would not.

* * * * * * * * * * * * * * Thomas Jefferson

Falsely attributed to Thomas Jefferson
http://tinyurl.com/6gmvmz