Metal vs Wood or T2 vs VP (Part II)

On Mar 29, 2:44*am, Bob Hoover wrote:
On Mar 28, 9:20*pm, Copperhead wrote:

... I looked at the VP
and used the plans as a means of determining if I could build the ribs
and bulkheads with store front or scrap lumber. I could and did, but
my height and weight pretty much ruled out the VP for me.

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Dear Joe,

Agreed, sadly. *The design is such a tumbleweed it limits its market.
Unfortunately, in most cases it doesn't do that until time for that
all-important first flight rolls around. *Based on the Volksplane
Group, the exact same features that limit the plane's practicality for
one group of pilots turns out to be one of the most critical factors
for another, in that smaller/lighter pilots often acquire their bird
as a bargain, already built. (But I gotta tell you pard, There is some
BIG people flying Volksplanes. [See their Photos archive. *They've got
some wizard videos].)

Since the short-coming (ie, excessive drag) is largely a function of
its design I suspect there are a few examples of cleaned-up copies.
On the other hand, I weighed about 190 when I had my first flight in a
VP1 and found it an enjoyable experience. *I was especially impressed
by the coordination of the tail. *But the take-off was best described
as leisurely. (I was six feet tall back then. *Now, I'm exactly one
vertebrae shorter :-)

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Your information about the rear shaft VW engine was much appreciated
as I've purchased the Great Planes Type 1 Engine Assy Manual and found
it to be every bit as good as you'd told me it was. W/O a doubt any VW
engine I build will be a rear drive, if for nothing else due to the
weight savings and lesser amount of money involved.

I'd intended to send you an e-mail asking about the "mission"
differences of the front vs rear drive VW engines but was unable to do
so.

---------------------------------------------------------------------------*--

Yeah, Steve's manual is pretty good. *I think he's also got a video
now. *As for tracking me down...

*Try:

I've a hunch Steve spends a good part of his life on the
telephone :-) *(Steve produces a really beautiful flywheel-mount.
There are some pictures of it in my blog.)

As for the 'mission' business it might help if you couch the question
differently. *For example, name all the automobile engine conversions
in which the propeller was attached to the pulley-hub of the
crankshaft?

Then ask yourself 'why?' *Because the truth is, putting the prop as
close to the thrust-bearing as possible makes the best kind of sense.
In effect, the typical VW with its prop on the pulley-hub is an
EXCEPTION to the standard practice of auto engine conversions.

As for any reference to the clutch-end of the crankshaft as being the
REAR, it is actually located on the FRONT of the VW engine. *At least
it is to those with any experience with Volkswagen vehicles. ( ALL
references for Volkswagen are relative to the driver or the front
bumper.)

I've explained how the first flying VW's used the pulley hub and how
those advantages were lost by the time the engine's displacement
surpassed 1200cc. *The sad part of the tale is that everyone continued
to try and emulate the success of the 1000cc engine with its 'built-
in' engine mount.

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Regardless the 1835 cc and 1915cc R/D VW engines are remarkably
affordable looking to me, with the difference between them and the
2180cc cost wise being considerable. HP does indeed cost money as
you've written quite often.

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The reason for the big difference is that you don't need the special
crankshaft nor the 'Force 1' prop-hub. *But depending on which
airframe you're interested in, there may be even LESS COSTLY
alternatives.

In the above you've mentioned 'horsepower.' *I understand what you
meant but it would be far more accurate to refer to TORQUE and more
specifically to THRUST. *In fact, when it comes to homebuilts, we'd
probably all be better off if we referred to our engines in UNITS OF
FLYABILITY or UF's. *It certainly wouldn't be any crazier than the
situation we have now, where some fellow tells you his engine produces
80 horsepower then in the next breath sez it burns only three gallons
per hour. *The tricky bit here is that both statements may be
correct.. but it would be impossible for them to be correct AT THE
SAME TIME.

Three gallons of fuel is about 18 pounds *One of the most critical
specifications for an engine is its Specific Fuel Consumption, which
is how many POUNDS of fuel it burns PER HOUR to produce ONE
horsepower. *Normally aspirated air-cooled engines are clustered near
the .500 mark, meaning they burn about half a pound of fuel per hour
for each horsepower. *Economy of scale applies so you'll find a big
radial down near the bottom of the curve and your lawn-mower up near
the top, but your flying Volkswagen will be found clustered with the
small (ie less than 500cid) Lycomings and Continentals.

The best SFC EVER for a spark-ignited, gasoline-fueled aircraft engine
was for those humongous *turbo-compound radials like the ones used in
the B-36. *Their SFC was under four-tenths of a pound of fuel per
hour. *(!!)

Then comes this expert with his converted VW that has an SFC of .225!
By every engineering measure in the world the man should be given the
Nobel prize... right after they give him the Harmon Trophy. *I mean,
an SFC of .225! *The guy has got to be the best engineering GENIUS of
all time!

(What's that? *You're saying he FIBBED a little? *Well... okay. *But
did he cross his fingers at the same time? Because if he DIDN'T it
means we get to call him 'Liar Liar pants on fi..' What? *Ah! *He DID
cross his fingers. *Ah! *You're saying he DID cross his fingers. *I
see. *Thanks for clearing that up for us.)

Well shucks. *I was really looking forward to the Awards Ceremony.

So maybe we should lay horsepower aside for the moment and stick with
just the engine and the prop. *Including the prop is the honest way to
do it because you need to figure-in your prop's efficiency. *If you're
lucky your prop's efficiency will be between 60% and 70%. *That's
because we're using a fixed-pitch prop, which has to be a compromise
between take-off and cruise. *If you carve your prop for its optimum
climb (or take-off) performance you're going to have to give away a
lot of fuel during cruise. *But if you carve a prop for maximum cruise
performance you're liable to need a mile of concrete to get that puppy
into the air.

Of course, what you'll do is try to find a good compromise between the
two.

But having said all that, you're probably still wondering about this
less expensive option I mentioned, which is to leave your heads and
the crankcase alone -- don't machine them for bigger jugs. *Then
install a crankshaft having a longer throw... and a set of longer
connecting rods.

Odds are, you'll stick with a stroke of about 78mm the longest set of
rods you can afford. *The savings comes in because you don't have to
do any machining on the crankcase or heads; you use the stock items.
You WILL have to clearance the case because the longer throw is now
going to hit the webs inside the crankcase -- exactly as they would if
you opted for a 2180 -- but clearancing is a minor chore and something
you can do for yourself. *So you end up buying a new crank, new rods
and a set of SPACERS that allows all this stuff to bolt together.

What you GET is an engine that develops its torque 'way down near the
bottom of the rpm curve. *That means you can carve a more efficient
PROP because it will be spinning a lot SLOWER. *Slow means low rpm's
and low rpm's means low wear.

Bottom line is that you get an engine that provides all the TORQUE you
can use. *How big is it? Umm lesssee... 78mm crank and stock jugs is
1791cc. You can call it 1800 if you wish.

How many 'horsepower?' *Well.... spin *it up to about 5000 rpm on the
dyno, you'll probably see about 100hp. *For mebbe a minute :-)

-Bob

"Bottom line is that you get an engine that provides all the TORQUE
you
can use. How big is it? Umm lesssee... 78mm crank and stock jugs is
1791cc. You can call it 1800 if you wish." BH

Now that's just the information I was wanting Bob as I'm looking at
the M-19 Flying Squirrel or the Rag a Bond. It would sure be nice if
the BK 1.3 plans were out, but the Beta testing he's having done is a
positive indication of his intent to do right by others.

Oddly enough I've had more fun researching and experimenting with
plans and parts building then I'd ever have thought possible and have
spent very little money so far. Mostly this has been due to the fact I
already have most of my woodworking power tools as well as a lot of
metal cutting and bending tools.

Regards

Joe S.

On Mar 29, 9:17*am, Copperhead wrote:

Oddly enough I've had more fun researching and experimenting with
plans and parts building then I'd ever have thought possible and have
spent very little money so far. Mostly this has been due to the fact I
already have most of my woodworking power tools as well as a lot of
metal cutting and bending tools.
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Dear Joe,

Normally, when you have the option of building from either aluminum or
wood, you would opt for metal but there are a few cases where wood may
prove to be the better choice. In the mid-1930's Virginias Clark, the
fellow who gave us the Clark-Y airfoil, patented a process of making
plywood called 'Duramold' that was superior to aluminum in several
ways, but especially with regard to compound curves. Howard Hughes
acquired the rights to the process (I believe through Fairchild
Camera) and used it to produce the HK-1 'Hercules' -- which we
generally know as 'the Spruce Goose,' even though it is mostly birch.
The 'K' part of 'HK' referred to Henry J. Kaiser, who was supposed to
assemble the giant flying boat, Hughes to fabricate the parts.

One reason we've never heard much about Dura-mold is because of
fiberglas.... and a small Swiss company that came up with epoxy.
Combine the two and even a back-yard craftsman has the ability to
produce complex parts stronger than steel but weighing as much as two-
thirds less.

-Bob

PS -- I've got a hunch that threads such as this often turn into
something useful.

On Mar 29, 12:54*pm, Bob Hoover wrote:
On Mar 29, 9:17*am, Copperhead wrote:

Oddly enough I've had more fun researching and experimenting with
plans and parts building then I'd ever have thought possible and have
spent very little money so far. Mostly this has been due to the fact I
already have most of my woodworking power tools as well as a lot of
metal cutting and bending tools.

---------------------------------------------------------------------------*------------------------------

Dear Joe,

Normally, when you have the option of building from either aluminum or
wood, you would opt for metal but there are a few cases where wood may
prove to be the better choice. *In the mid-1930's Virginias Clark, the
fellow who gave us the Clark-Y airfoil, patented a process of making
plywood called 'Duramold' that was superior to aluminum in several
ways, but especially with regard to compound curves. *Howard Hughes
acquired the rights to the process (I believe through Fairchild
Camera) and used it to produce the HK-1 'Hercules' *-- *which we
generally know as 'the Spruce Goose,' even though it is mostly birch.
The 'K' part of 'HK' referred to Henry J. Kaiser, who was supposed to
assemble the giant flying boat, Hughes to fabricate the parts.

One reason we've never heard much about Dura-mold is because of
fiberglas.... and a small Swiss company that came up with epoxy.
Combine the two and even a back-yard craftsman has the ability to
produce complex parts stronger than steel but weighing as much as two-
thirds less.

-Bob

PS -- I've got a hunch that threads such as this often turn into
something useful.

Bob,

I’d read about the composite construction techniques of the ill named
“Spruce Goose”, but never made a correlation with respect current
fiberglass composite aircraft. Merely at a guess, it would appear that
one would need to make they’re own “duramold” ply (glass) wood while
constructing an airframe.

I certainly agree that such a practice would eliminate the need for
applying fiberglass to foam for panels or coverings. Current vacuum
bagging practices used on KR’s with hand made mold would most
certainly work. Now I’m going to have to do some research and
experimentation to see what epoxy and wood veneer bond together best.

For this, I believe the local boat builder’s and marine plywood supply
distributors are going to be a good information source. I think your
right about the weight savings coupled with enhanced strength of such
a project. It also looks like it would eliminate a lot of glass cloth
as well as grinding and sanding. Very interesting and informational,
thanks.

Regards

Joe S.

On Mar 29, 11:45*am, Copperhead wrote:

I’d read about the composite construction techniques of the ill named
“Spruce Goose”, but never made a correlation with respect current
fiberglass composite aircraft. Merely at a guess, it would appear that
one would need to make they’re own “duramold” ply (glass) wood while
constructing an airframe.
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Dura-mold used a 'resin' similar to Plastic Resin Resorcinol in
APPEARANCE (or so I'm told; second-hand information coming at you
here). That is, there was a powder and a liquid which had to be mixed
according to a critical ratio. The wood was then impregnated with the
resin using a lay-up process similar to doing a boat hull. cabin tops
or what-have-you... with one critical exception. It was a CLOSED mold
-- you had to get the lid on the thing -- and the cure was done using
HEAT. In this case, steam or hot water.

The molds could be concrete & hot water -- and most of them were --
but some parts used ALUMINUM molds and electrical or steam heat.

Hughes ponied up an incredible amount of cash to resolve a lot of
unforseen problems relating to serial production, producing panels of
larger size, attaching panels together ...ever heard of FPL-16a
(HUGHES GLUE) ? Once all the bugs were out of the production process
you start popping HK-1's out of ship yards on both coasts at a
guesstimated rate of thirty PER DAY. And of those eight humongous
engines, it took only FOUR to FLY the thing... but all EIGHT were
needed for a fully-laden take-off

The deal with fiberglas & epoxy was that it weighed less and was
stronger than Dura-mold, plus you could formulate it for room-
temperature curing. All of that development work -- and all of that
MONEY -- had been overtaken by events.

(So what was the big flap between Hughes and the government? Hughes
had a piece of paper signed by 'the government' that said they would
pay ALL COSTS incidental to production of the HK-1, which the Hughes
lawyers read to mean all those bucks spent in development work. The
Government disagreed, saying they meant the cost of setting up
production facilities, NOT costs associated with basic research. Plus
there were more than a few Congressmen who kept pointing out that the
thing had not actually FLOWN... that it might be nothing more than a
bogus scheme to screw the American tax payer, yada yada yada...

Hughes won, by the way. But it was often said that he spent more on
legal fees than he recovered.)

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I certainly agree that such a practice would eliminate the need for
applying fiberglass to foam for panels or coverings.

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I'm not sure why it is, but a lot of people seem to think that mold-
less composite work was something new; that Kenny had come up with a
better mouse trap. In fact, that method of fabrication has been in
use for literally THOUSANDS of years. Although I wasn't around back
then (despite what you may have heard...) they have found numerous
examples of PLYWOOD in Egyptian tombs and the re-curve bow used by
Genghis Khan's mounted troops was of mold-less composite structure.
Closer to home, when tasked with producing 1200 sets of Roman-era
armor for the movie 'Ben Hur,' the set designers cranked them out
using paper mache. But of more practical use, it was fairly common
for fishermen to re-enforce spars and booms using canvas & varnish.

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Current vacuum
bagging practices used on KR’s with hand made mold would most
certainly work. Now I’m going to have to do some research and
experimentation to see what epoxy and wood veneer bond together best.

-----------------------------------------------------------------------------------

Homebuilders could turn out some damn good airplanes on the cheap if
we can come up with a mini-production line for vacuum bagging leading-
edge sections for a couple of standard airfoils, such as 4412, 4415 or
the M6, in lengths of about 48 inches. Properly done, the section
gets peel-ply'd on the interior and the edges get stepped. It locks
you into a rectangular plan-form but you can come up with a good D-
cell, allowing you to produce a really good wing.

---------------------------------------------------------------------------------

For this, I believe the local boat builder’s and marine plywood supply
distributors are going to be a good information source. I think your
right about the weight savings coupled with enhanced strength of such
a project. It also looks like it would eliminate a lot of glass cloth
as well as grinding and sanding.

---------------------------------------------------------------------------------

The information everybody wants is out there but it's fragmented.
Unfortunately the only body that claims to speak for the lowest level
of aviation in America -- logically the organization that should
concern itself with such matters -- has not.

-Bob

On Mar 29, 7:04*pm, Bob Hoover wrote:

Homebuilders could turn out some damn good airplanes on the cheap if
we can come up with a mini-production line for vacuum bagging leading-
edge sections for a couple of standard airfoils, such as 4412, 4415 or
the M6, in lengths of about 48 inches. *Properly done, the section
gets peel-ply'd on the interior and the edges get stepped. *It locks
you into a rectangular plan-form but you can come up with a good D-
cell, allowing you to produce a really good wing.

I've had similar thoughts and have done some small experiments with
the TPG process. Haven't yet found the right core material. High
density PVC foam looks promising in place of Taylors paper. I have
some to play with but started projects must be completed first.

As for being "locked" into a rectangular plan-form, I'm not so sure.
There seems to be enough flexibility in the formed leading edges to
squish them down a bit after cure. The leading edge radius stays
larger then a full scaling down but that might work out to be an
advantage when it comes to tip stall?

While I'm thinking about it - vacuum sources. Mine is a water bed
drain tool. Works great and cost little. Set it up on the lid of a
Rubbermaid type tub of water with a small recirculating pump and you
have an inexpensive and reliable source of vacuum. When your finished
everything stores in the tub for the next use. Just remember to put a
check valve on the outlet or you risk sucking in water if the power or
pumps prime gets interrupted. A good source of check valves ... power
brake hose from about any salvage auto. For vacuum control a fish
tank air valve works well enough.
==============================
Leon McAtee