Windrose II 15-meter Motorglider Plans For Sale

Jim and I are conducting a Spar workshop on november 22-23, 2003 in Marion
OH.

Carbon Rovings are a very poor spar material since you cannot pull all of
the strands straight and through testing it was found to have a wide
variance in tension and compression. Compression being the worst case which
is about 40,000 to 80,000 psi... one may get to 120,000 psi in tension but
this is highly unreliable so you must degrade the enitre layup ..... but
just what do you degrade it to... it depends on how well the person laid it
up. With the Tests that Jim did, they where extremely careful and where
professional fabricators in fiberglass and those results where very
discouraging.. With carbon rods there is no guessing as to what numbers you
are dealing with. Also the process has been thoroughly tested.

The other problem is that with the windrose construction you are directed to
drill through the carbon. This is an absolute mistake!! This is dangerous.

If you are asking an amateur builder to construct the spar with roving you
have a situation where the result is highly unpedictible and then drilling
through the spar increases the danger that the spar could fail.

As for instances of actual breaking in the air..... I'd rather build it
correctly first and not have to site facts of dead pilots and broken wings.
See our testing of the carbon Monarch spar on our web site for example.

All of the Maupin plans need upgrading to deal with modern practices and
show that indeed the aircraft have been throughly tested. From what I have
seen the Maupin/ Culver designs where never thoroughly tested and with the
15 meter windrose was never even built by the designers.

Jim Maupins designs were wonderful concepts and should be studied with that
in mind but they are not a refined aricraft as they exist at present.

Having siad all of that we in north america do need some brave designers to
challenge the dominance of the German ships. It takes a lot of money, guts,
research and hard work. and do not expect much support from your fellow
soaring pilots! That Jim Maupin got outside the normal glider design was
very welcome... that he tried new concepts was great...that he opened up the
light sailplane was terriffic..... but we need dedicated people to continue
these ventures. It will not be profitable... and plans should not be sold
unless you have a craft that has been thoroughly tested. However people can
donate to the cause and be an active part of a development.

-mat
--
Marske Flying Wings
http://www.continuo.com/marske

Earlier, (Doug Hoffman) wrote:

Jim Marske shows carbon rovings to have 120,000 psi tensile
strength in his website. Not the numbers you show. ??

Actually, that's the Web site that Mat maintains for Jim Marske. So
Mat does know exactly what's on it.

But on-topic, what's really at issue is not the tensile strength, but
the compression strength.

The way I understand the issue from personal conversations with Jim
Marske, hand-laid carbon rovings often drastically under-perform their
predicted values in compressive strength. The problem is that it is
very difficult to achieve the proper fiber alignment and resin content
and properties under hand-layup conditions. The result is compressive
strength (the kind you usually need in an upper spar cap) in the
neighborhood of only 40 ksi or 60 ksi. Jim says he did coupon tests to
validate these numbers, and I certainly believe him.

In comparison, the Graphlite rods and strips are amazing, with tensile
strengths of something like 320 ksi and compressive of about 280 ksi.
They achieve these very high values using a pultrusion process in
which the perfect fiber/resion ratio is achieved, and in which the
fibers are perfectly aligned, and in which the fiber/resin matrix is
heated and compressed to achieve the best possible resin properties.

The only area in which the Graphlite does not vastly outperform
hand-laid carbon is in stiffness. The stuff is about 20% stiffer than
hand-laid, which is great but not incredible. In glider design, much
of the structure is bounded by stiffness and not strength. In
stiffness-bound applications, the Graphlite products will give you a
20% weight reduction over hand-laid; but as a side-benefit they give
you about 600% greater ultimate strength.

I used the Graphlite rods according to Jim Marske's design
methodologies in the HP-24 wing spar, and what I got was a wing spar
for a 9-meter wing panel (half of the 18-meter total span) that weighs
16.5 lbs (about 20 lbs after the spar butt reinforcements are added).

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

"Bob Kuykendall" wrote in message
But on-topic, what's really at issue is not the tensile strength, but
the compression strength.

The way I understand the issue from personal conversations with Jim
Marske, hand-laid carbon rovings often drastically under-perform their
predicted values in compressive strength. The problem is that it is
very difficult to achieve the proper fiber alignment and resin content
and properties under hand-layup conditions. The result is compressive
strength (the kind you usually need in an upper spar cap) in the
neighborhood of only 40 ksi or 60 ksi. Jim says he did coupon tests to
validate these numbers, and I certainly believe him.


Excellent stuff Bob.....
I also believe Jims numbers.........
Compressive strength is the upper spar cap limiting constraint.
Rovings or tow, are admittedly difficult to use, BUT can be used
successfully. Personally, I find that Unitape cures many of Mats
concerns about orientation and resin content. In fact it is so commonly
used that free tow is basically off the market. 20 some odd years ago
when carbon was expensive,new,untested, all you could get was dry tow.
Bunches better than not having it, but definately not state of the art
today.
Todays woven goods are vastly superior to the old stuff. I hesitate to
condemn its use in spars. It might be a bit less efficient than rods but
definately
usable in todays structures. Especially by the workman at home.

NOW lets also get down to brass tacks and admit to each other that the mode
1
failure of upper spar caps is BENDING caused by a collum buckling. When
this
occurs the substructure supporting the spar caps deflects and the cap fails
in bending.
A good example is when the shear web ruptures as the bending loads go up and
the
spar cap can't absorb the local bending load. The failure looks different
than a
compressive failure (because it is) inasmuch as it looks like a snapped
pencil.

Scott.

To add to the discussion of Carbon in use with spars.

One of the important elements that should not be forgotten is the
deflection. With Carbon rods you can accurately predict the deflection which
I believe is very important in glider wings. I have produced a spreadsheet
that will predict the amount of rods needed and predict the deflection. A
good deflection is about 10 to 12 " per G and with hand laid up rovings you
may overcompensate to account for the poor quality of rovings and produce a
very stiff wing.

And incidently I own and maintain the site and work in partnership with Jim.
-mat
--
Marske Flying Wings
http://www.continuo.com/marske

On Tue, 21 Oct 2003 17:30:24 +0000, Robert Ehrlich
wrote:

Marske Flying Wings wrote:
...
The use of wood in a glider is not really recommended any longer, nor is the
combination of wood and fiberglass. Ineveitably the wood and fiberglass tend
to separate. It is better to use an all fiberglass structure and I even
avoid the use of foam.
...

However a lot of fiberglass gliders are using wood (mostly plywood)
for holding various elements of the linkages from stick/spoilers lever
to the control surfaces they actuates. I had just a look inside one of
our Pegases where the seat pan has been removed for its annual, and it
is made this way. IIRC this fuselage is a copy of the ASW20, never heard
of separation of wood from fiberglass, neither in Pegases nor in ASW20's
and there is a lot of them flying since a lot of time.


Wood inside fibreglass can be a problem for repairs. The wood will
shatter inside the fiberglass and you end up removing good glass to
repair the wood.
I was told this by Harry Schneider (glider designer, manufacturer and
repairer) at Gawler about 30 years ago and subsequently saw an example
of what he was talking about.

Mike Borgelt

(Bob Kuykendall) wrote in message . com...
In comparison, the Graphlite rods and strips are amazing, with tensile
strengths of something like 320 ksi and compressive of about 280 ksi.
They achieve these very high values using a pultrusion process in
which the perfect fiber/resion ratio is achieved, and in which the
fibers are perfectly aligned, and in which the fiber/resin matrix is
heated and compressed to achieve the best possible resin properties.

Bob,

With all due respect I think you missed my point. I am not saying
"don't use the rods".

I said:
'I will not question that the pultruded carbon
rods are an excellent building material. Had the stuff been
available when Culver and Maupin were designing they may even
have used them instead.'

My point was that materials other than the rods can still be safely
used (providing they are used properly, etc., etc.). There is no
reason for Mat to be condemning the perfectly legitimate use of the
carbon rovings as used in the Windrose and Carbon Dragon. Guess what,
the Windrose 13 meter doesn't even use carbon. It uses fiberglass
rovings.

Also, when using the rovings as specified for the Windrose I or II or
CD one avoids the complexity and possible source of error of having to
design and build an additional structure to tie the main spar
pins/bolts to the carbon rods. One needs only to drill bolt holes
straight through the roving layup. Simple, easy. Which was one of
the design criteria for the glider.

Again, I'm not slamming the rods. I think they are great. I just
think Redsell doesn't know what he is talking about when he says the
rovings cannot be safely used and other things he's said that I won't
get into. Note that he did not produce the evidence that I asked for,
that is: even one instance of roving spar cap failure either through
proof loading or flight loads. He didn't because he can't. Culver
was not incompetent. Irv Culver is not able to defend himself from
the likes of Redsell because he is dead. Especially given that,
Redsell has taken a lot of cheap shots, in my opinion.

-Doug

Doug hoffman wrote:
My point was that materials other than the rods can still be safely
used (providing they are used properly, etc., etc.). There is no
reason for Mat to be condemning the perfectly legitimate use of the
carbon rovings as used in the Windrose and Carbon Dragon. Guess what,
the Windrose 13 meter doesn't even use carbon. It uses fiberglass
rovings.

The point I am making is that there is no way you can honestly compute the
strength you have using carbon rovings with hand layup especially for
someone who has never done it before. Even a fiberglass pultrusion would
have been better as Jim used in the early Monarchs. The other problems is
that you cannot compute the deflection at the wing tips which should be
about 10-12 ". So if an amateur is building the wings for the first time he
could easily mess it up by not being consistent in the pulling of the carbon
or fiberglass tow. I have found that there is no underestimating the bad
buidling practices of some homebuilders. I have had to correct a number of
homebuilts!

Doug hoffman wrote:
Also, when using the rovings as specified for the Windrose I or II or
CD one avoids the complexity and possible source of error of having to
design and build an additional structure to tie the main spar
pins/bolts to the carbon rods. One needs only to drill bolt holes
straight through the roving layup. Simple, easy. Which was one of
the design criteria for the glider.

Once you drill through the carbon you have little tensile strength left at
that point since you are relying on the fiber to give you the strength. The
carbon should be properly bonded to a well engineered fiberglass block ,and
that is what you drill. Never drill through the carbon!!!!

Remember also that you cannot put iron and carbon together... galvanic
action corrodes the bolt.

Rather than present those wings that have broken in the air, a better method
is to see the results of the testing of the Marske Designed spar in the
Genesis that went to 18 G's before the fitting broke on the test stand. Jim
had tested each of the componet parts proving that this method would not
come apart after many years of use. And this was all predictible. There are
no studies done on the longevity of the windrose style of spar.

So in my estimation using rovings can be dangerous for the first time
builder and especially so if you drill through it. I do realize there are
still a number of glider manufactureres building spars with carbon rovings
but gradually they are changing to accept Jim Marske's proven Carbon rod
spar. See the article in the SHA newletter from the Silent Glider
manufactuere.

--
Marske Flying Wings
http://www.continuo.com/marske

"Marske Flying Wings" wrote in message
...
1) The point I am making is that there is no way you can honestly compute
the
strength you have using carbon rovings with hand layup especially for
someone who has never done it before.
2) The other problems is that you cannot compute the deflection at the wing
tips which should be about 10-12 ".
3) I have found that there is no underestimating the bad
buidling practices of some homebuilders. I have had to correct a
number of
homebuilts!
4) Once you drill through the carbon you have little tensile strength left
at
that point since you are relying on the fiber to give you the
strength. The
carbon should be properly bonded to a well engineered fiberglass block
,and
that is what you drill. Never drill through the carbon!!!!
5) Remember also that you cannot put iron and carbon together... galvanic
action corrodes the bolt.

Good Morning Mat.

1) You can certianly do it. It is accomplished in the same manner that all
other materials
are checked. You just have to decide on a value to use. You say you have
tested and
shown values as low as 30KSI. Cool, use that and move on........

2) Your wind bending allowables may be 10 to 12 inches, but that is a
subjective opinion.
Many all glass birds deflect more with no ill effects. Yours is a
subjective opinion
presented as a fact.........

3) Agreed, But these clowns would be the same fools who couldn' glue in the
rods properly
either, so I'll forget about misassembly. Your DAR or Tech Councellor
will stop this from
being a problem.

4) The loss of tensile strength is very dependant on the reduction in
laminate cross section. Unless
you have the particular layup schedule in front of you, you can't make
an informed decision on the
reduction in tensile strength. If the laminate gets thicker or wider,
all bets are off. If the laminate
is the same in cross section at the hole location as it is outboard of
there, you still need to run the
numbers to see if the remaining cross section meets the design loads.
Again, lacking that data,
neither of us can make an informed decision. You are correct that you
will experience a local
reduction in tensile strength, but it may still very well reach the
design limits and be of no consequence.

5) This is a narrowminded statement. You would be correct if you put the
fasteners in "dry", but only
a fool would do that. Many steel and titanium fasteners are installed
through carbon
panels on Boeing and MDC jetliners. I have installed them. The trick
is to install them "wet" with
an approved sealant to provide the barrier you need. Entirely doable
and cost effective. Proclaiming
that you can't do it is in my mind incorrect, but we can disagree on
how you present the facts on this one.

Back on point. There is no reason you can't use hand layed up carbon
successfully. Yeah it requires care,
but so does riveting , welding, dope and fabric and all the other processes
involved in amatuer constructed
aircraft. Some people find it easy to work composites well, some are very
challenged. Blanket statements saying it
is unsafe to do so is in my mind bull****...........

Scott Correa

Scott Correa,

Yes those things can all be done and at one time where probably accepted as
normal practice.... but we have better methods and materials today so lets
use them. Jim Marske's Spar design is the best design I have seen so lets
give him credit for such good work and encourage others to use this.

As for dangerous, that is for each of us to decide: but for me I want the
best technology, methods and proven methods with predictable results and
that is exactly what the Windrose lacks in its present state....there was no
mention in the plans of coating anything with epoxy and the carbon tow was
not increased at the point where the bolts went through.

Update the Windrose plans, do a lot of test flying... that will go a long
way to remedy this design.

-mat
--
Marske Flying Wings
http://www.continuo.com/marske

Mat Redsell Writes:
[snip]

As for dangerous, that is for each of us to decide: but for me I want the
best technology, methods and proven methods with predictable results and
that is exactly what the Windrose lacks in its present state....there was no
mention in the plans of coating anything with epoxy and the carbon tow was
not increased at the point where the bolts went through.

Umm, page 8 of Jim Maupin's instructions. Third paragraph: "If everything
checks out, drill the spar stubs for the 5/16" bolts, and bolt in place. I
recommend using lots of epoxy in the bolt holes and on the nuts."

and the carbon tow was
not increased at the point where the bolts went through.

Oh please. Did you really build one of these? I'm not even going
to bother rolling open the plans to give the measurements. The
hot-wired slot in the foam, for the spar caps, is a *lot* bigger
at the spar root than anywhere else.

I am tiring of this, Mat.

What kind of technical education did you say you received? It must
be impressive for you to berate Irv Culver's calculations as you are
doing.