KR> First Flight Issues - Elevator Trim Tab

[Sid Wood]

On the first flight the elevator trim tab Nyrod sheath anchor point broke 
loose and moved the trim tab to the full nose up position resulting in near 
loss of control.  Epoxy does not stick to well to plastic surfaces.
For the fix: I installed an aluminum angle to support an Adel cushion clamp. 
The clamp captures a 1/4 inch fuel hose that was slipped over the Nyrod 
sheath.  Wrapped the Nyrod with vinyl tape for a snug fit in the hose.  The 
clamp keeps the cable from wiggling around and prevents the sheath from 
moving without pinching the inner cable.  Operation of the trim tab is now 
smooth and positive.
Here is a picture from my website for the re-worked cable support:
http://websites.expercraft.com/sidwood/index.php?q=log_entry&log_id=71589

Sid Wood
Tri-gear KR-2 N6242
Mechanicsville, MD, USA

KR> Glass cloth shelf life

[Jeff Scott]

This article included below is from the web site 
. ?These guys weave and finish 
composite fabrics to sell. ?What I read here is that our discussion has some 
terminology issues. ?Sizing is a coating for the yarn so they can weave the 
fabric, but is cleaned away once the weaving is completed. ?Silane is most 
likely what our fabrics are coated with which does enhance the bonding of the 
resin to the cloth. ?Note, the key word here is that it enhances the BONDING, 
now the wetting out of the cloth. ?

The work I am currently doing is being done with 8 year old cloth. ?However, it 
should be noted that none of it is structural, so minor losses in bonding won't 
matter. ?For that matter, the plane isn't going to fall out of the sky if the 
current work falls off in flight, so I am still comfortable working with this 
material. ?However, based on what I am reading here, if I was building a new 
structural component such as a horizontal stab or elevator, I would buy new 
material to work with. ?Thank you Sid for bringing this to our attention.

-Jeff Scott
Los Alamos, NM



Fiberglass Finishes

When fiberglass cloth comes off the loom it is said to be ?in the greige? 
[pronounced grey]. In order to be compatible with resin systems it must first 
be heat cleaned to remove oils and sizing needed for weaving and then treated 
in a chemical bath, called ?finishing.? Finishing formulations are proprietary 
recipes that enhance bonding with the type of resin to be used. One of the 
earliest fomulations that is still in use is called Volan, which employs 
compounds of chromium. We do not recommend the use of Volan finishes because of 
the chromium content. Chromium is a toxic heavy metal that is considered a 
strategic material by the military and much of it is imported from Africa. 
Potential problems are evident! It also imparts a green cast to the fiberglass 
and the resulting laminate is generally rather grey and dirty looking. Silane 
finishes produce a clearer laminate and avoid the chrome problems.

Our preferred silane finish from BGF is called 497A. It was developed for 
critical aerospace applications and is compatible with epoxy, vinylester, and 
polyester resins. We occasionally have fabrics with 627 finish, also a 
general-purpose silane. Our fabrics that are made by Hexcel-Schwebel have a 
CS-767 finish, which we believe to be comparable to the BGF finishes. Very 
occasionally we will have some material that is finished specifically for one 
resin system, usually epoxy. In those instances we are careful to assure that a 
potential buyer is using the correct resin before making a sale.

Fiberglass finishes are degraded by environmental conditions such as moisture 
or even humidity and they deteriorate to some degree just with time. The 497A 
finish has especially good longevity, which is one of the reasons we prefer it. 
While deterioration begins as soon as finishing is completed, there is no 
significant loss of physical properties over the first year or two, provided 
the fabric has been wrapped in plastic and protected from high heat and 
humidity. I would be careful about using fiberglass more than three years old 
and would probably not use it after five years for any critical application 
without running some tests first.

> - Original Message -
> From: smwood
> Sent: 03/27/13 10:45 AM
> To: krnet at list.krnet.org
> Subject: Re: KR> Glass cloth shelf life
> 
> The glass in fiberglass cloth does not have a shelf life. The glass is 
> inorganic. The sizing coating on the glass strands is an organic compound 
> and has a definite shelf life.
> I use to teach this fiber glass stuff for the EAA Sport Air Workshops and 
> still do at AirVenture.
> 
> Sid Wood
> Tri-gear KR-2 N6242
> Mechanicsville, MD, USA
> 
> ---
> > Sid said - Fiber glass cloth has a sizing coating on each strand to help
> > the epoxy
> > resin to bond to the glass. The shelf life for most fiber glass sizing is
> > five years. After that time the wetting out with the resin becomes more
> > difficult and will result in a weaker structure. The older the cloth the
> > worse the situation will be.
> >
> > I posted this question to the group some time ago and was told that there 
> > is
> > no end shelf life on fiber glass cloth. Would someone in the industry, (If
> > there is someone in the group), please check in and clear this up.
> >
> > Patrick Driscoll
> > Saint Paul, MN
> > patrick36 at usfamily.net
> > www.pensbypat.com
> > If you can read this, Thank a teacher
> > If you are reading this in English, thank a veteran
> >
> > 
> 
> 
> 
> ___
> Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search.
> To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org
> please see other KRnet info at http://www.krnet.org/info.html
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KR> Glass cloth shelf life

[smwood]

The glass in fiberglass cloth does not have a shelf life.  The glass is 
inorganic.  The sizing coating on the glass strands is an organic compound 
and has a definite shelf life.
I use to teach this fiber glass stuff for the EAA Sport Air Workshops and 
still do at AirVenture.

Sid Wood
Tri-gear KR-2 N6242
Mechanicsville, MD, USA

---
> Sid said  - Fiber glass cloth has a sizing coating on each strand to help
> the epoxy
> resin to bond to the glass. The shelf life for most fiber glass sizing is
> five years. After that time the wetting out with the resin becomes more
> difficult and will result in a weaker structure. The older the cloth the
> worse the situation will be.
>
> I posted this question to the group some time ago and was told that there 
> is
> no end shelf life on fiber glass cloth. Would someone in the industry, (If
> there is someone in the group), please check in and clear this up.
>
> Patrick Driscoll
> Saint Paul, MN
> patrick36 at usfamily.net
> www.pensbypat.com
> If you can read this, Thank a teacher
> If you are reading this in English, thank a veteran
>
> 

KR> Glass cloth shelf life

[brian.kraut at eamanufacturing.com]

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KR> First Flight Issues - Elevator Trim

[brian.kraut at eamanufacturing.com]

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KR> First Flight Issues - Elevator Trim

[Lawrence Bell]

Thanks, Sid, good heads up for the rest of us. I like your throttle setup,
I'm going to try to copy it, Larry Bell

On Tue, Mar 26, 2013 at 5:57 PM, Sid Wood  wrote:

> On the first flight, 3/23/13, moments after lift off, the elevator trim
> jumped to Full Nose Up.  Trim control in the cockpit was non-responsive.  I
> had to hold firm forward pressure on the stick to maintain level flight
> with the stick position about neutral.  The bounced landing bent the nose
> strut.
> Investigation after the flight revealed the epoxy seal on the sheath of
> the Nyrod trim tab rod had broken.  The Nyrod center rod and the sheath
> were not damaged.  The break is at the entrance to the horizontal
> stabilizer leading edge inside the fuselage.  This allowed the sheath to
> move resulting in the trim tab moving to the Full Nose Up position.  The
> fix is to secure the Nyrod sheath.  This is the same practical installation
> requirements for any Bowden cable.
> NV aero is shipping a new nose strut.
> Here are some pictures from my website showing the Trim Control in the
> cockpit at Full Nose Down, the Elevator Trim Tab at Full Nose Up, and the
> broken Nyrod sheath anchor area:
>
> http://websites.expercraft.**com/sidwood/index.php?q=log_**
> entry&log_id=71577
>
> Sid Wood
> Tri-gear KR-2 N6242
> Mechanicsville, MD, USA
>
>
>
> __**_
> Search the KRnet Archives at 
> http://tugantek.com/**archmailv2-kr/search
> .
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> please see other KRnet info at http://www.krnet.org/info.html
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