K8b restoration

[John Foster]

I was given a junked K8b due to water damage to the wood at the wing root and multiple tears in the original fabric and chipped/peeling paint. However, it looks like it may be restorable (worth it, that's another story). Anyway, I'm interested to know if there is an online repair manual that lays out the specific techniques of repairing or replacing wood in the wings, and specifications on what type of wood to be used, etc. I looked around and found the list of ADs, but nothing that laid out what I am looking for. I've contacted Schleicher as well, but they simply directed me to a link on their website, that didn't really give the information I needed. This is a certified glider, and I'd like to keep it that way, as I'm hoping to use it as a club glider.

[Martin Gregorie[_6_]]

On Fri, 01 Feb 2019 17:29:37 -0800, John Foster wrote:

> I was given a junked K8b due to water damage to the wood at the wing
> root and multiple tears in the original fabric and chipped/peeling
> paint. However, it looks like it may be restorable (worth it, that's
> another story). Anyway, I'm interested to know if there is an online
> repair manual that lays out the specific techniques of repairing or
> replacing wood in the wings, and specifications on what type of wood to
> be used, etc. I looked around and found the list of ADs, but nothing
> that laid out what I am looking for. I've contacted Schleicher as well,
> but they simply directed me to a link on their website, that didn't
> really give the information I needed. This is a certified glider, and
> I'd like to keep it that way, as I'm hoping to use it as a club glider.

If you can't find anything more specific, this might help:

Workshop Practice For Building and Repairing Wooden Gliders and Sailplanes
by Hans Jacobs publisher Eqip, 45 euros.

Available from Eqip, amazon.de or www.vintagesailplane.org

I've no personal experience of that book, but I do have some of Eqip's
other books (Sailplanes 1920-1945, Sailplanes 1945-1965 and Sailplanes
1965-2000, which are excellent.


--
Martin | martin at
Gregorie | gregorie dot org

[Eric Munk]

At 02:05 02 February 2019, Martin Gregorie wrote:
>On Fri, 01 Feb 2019 17:29:37 -0800, John Foster wrote:
>
>> I was given a junked K8b due to water damage to the wood at
the wing
>> root and multiple tears in the original fabric and
chipped/peeling
>> paint. However, it looks like it may be restorable (worth it,
that's
>> another story). Anyway, I'm interested to know if there is an
online
>> repair manual that lays out the specific techniques of repairing
or
>> replacing wood in the wings, and specifications on what type
of wood to
>> be used, etc. I looked around and found the list of ADs, but
nothing
>> that laid out what I am looking for. I've contacted Schleicher
as well,
>> but they simply directed me to a link on their website, that
didn't
>> really give the information I needed. This is a certified glider,
and
>> I'd like to keep it that way, as I'm hoping to use it as a club
glider.
>
>If you can't find anything more specific, this might help:
>
>Workshop Practice For Building and Repairing Wooden Gliders
and Sailplanes
>by Hans Jacobs publisher Eqip, 45 euros.
>
>Available from Eqip, amazon.de or www.vintagesailplane.org
>
>I've no personal experience of that book, but I do have some of
Eqip's
>other books (Sailplanes 1920-1945, Sailplanes 1945-1965 and
Sailplanes
>1965-2000, which are excellent.
>
>
>--
>Martin | martin at
>Gregorie | gregorie dot org
>

Schleicher has all the drawings. The plywood used is birch, GL I
spec. Measure thickness or original material when replacing. Some
is 5 ply, but most ia 3-ply. Wood is spruce by heart. Specs are in
the Jacobs book.

Wooden Sxhleichers are known to suffer from Kaurit glue joint
brittleness by ageing, and a full glue survey of wings, fin and
controls would be prudent to see if a rebuild is viable. Have a look
at the YouTube channel “Kaurit in gliders” to see what to look for...

[James Thomson[_2_]]

At 01:29 02 February 2019, John Foster wrote:
>I was given a junked K8b due to water damage to the wood at the wing
root
>a=
>nd multiple tears in the original fabric and chipped/peeling paint.
>Howeve=
>r, it looks like it may be restorable (worth it, that's another story).
>An=
>yway, I'm interested to know if there is an online repair manual that
lays
>=
>out the specific techniques of repairing or replacing wood in the wings,
>an=
>d specifications on what type of wood to be used, etc. I looked around
>and=
> found the list of ADs, but nothing that laid out what I am looking for.
>I=
>'ve contacted Schleicher as well, but they simply directed me to a link
on
>=
>their website, that didn't really give the information I needed. This is
>a=
> certified glider, and I'd like to keep it that way, as I'm hoping to use
>i=
>t as a club glider.
>
As a general guide download "Standard Repairs to Gliders" from the BGA
website. It's in the Airworthiness section of their library, in a number
of
chapters.

Link to chapter 1: https://members.gliding.co.uk/wp-
content/uploads/sites/3/2015/04/1430312226_Section%201.pdf

Specific information on the Ka8 has to come from Schleicher.

[Colin Roney]

At 10:48 02 February 2019, James Thomson wrote:
>At 01:29 02 February 2019, John Foster wrote:
>>I was given a junked K8b due to water damage to the
wood at the wing
>root
>>a=
>>nd multiple tears in the original fabric and
chipped/peeling paint.
>>Howeve=
>>r, it looks like it may be restorable (worth it, that's
another story).
>>An=
>>yway, I'm interested to know if there is an online
repair manual that
>lays
>>=
>>out the specific techniques of repairing or replacing
wood in the wings,
>>an=
>>d specifications on what type of wood to be used, etc.
I looked around
>>and=
>> found the list of ADs, but nothing that laid out what I
am looking for.
>>I=
>>'ve contacted Schleicher as well, but they simply
directed me to a link
>on
>>=
>>their website, that didn't really give the information I
needed. This is
>>a=
>> certified glider, and I'd like to keep it that way, as I'm
hoping to use
>>i=
>>t as a club glider.
>>
>As a general guide download "Standard Repairs to
Gliders" from the BGA
>website. It's in the Airworthiness section of their
library, in a numbe
>of
>chapters.
>
>Link to chapter 1: https://members.gliding.co.uk/wp-
>content/uploads/sites/3/2015/04/1430312226_Section
%201.pdf
>
>Specific information on the Ka8 has to come from
Schleicher.
>
Contact Rattlesden GC.They are have almost finished the
renovation of a K13 which had the glue issue.

[Charlie Quebec]

Jacob’s book is the definitive work in this field.

[[email protected]]

It might be best to start with an thorough inspection by someone with wood repair and wood rot knowledge. Also ask about requirements to return the ship to service. Where are you located? In the US, the best way to go would be to license the ship in the Experimental category which can be used in clubs.
Hope this helps,
JJ

[son_of_flubber]

The best use might be to convert it to a Condor 2 simulator.

That will reduce your training costs.

[Charles Longley]

AC 43.13 has some good info
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43.13-1B_w-chg1.pdf

[Bruce Friesen]

On Friday, February 1, 2019 at 5:29:38 PM UTC-8, John Foster wrote:
> I was given a junked K8b due to water damage to the wood at the wing root and multiple tears in the original fabric and chipped/peeling paint. However, it looks like it may be restorable (worth it, that's another story). Anyway, I'm interested to know if there is an online repair manual that lays out the specific techniques of repairing or replacing wood in the wings, and specifications on what type of wood to be used, etc. I looked around and found the list of ADs, but nothing that laid out what I am looking for. I've contacted Schleicher as well, but they simply directed me to a link on their website, that didn't really give the information I needed. This is a certified glider, and I'd like to keep it that way, as I'm hoping to use it as a club glider.

John, there is a wealth of information, expertise and encouragement available from the Vintage Sailplane Association.

http://www.vintagesailplane.org/

I could expand on my comment if you wish, but my advice is to join the VSA, explore some of the past publications, and perhaps contact a couple of the names on the website directly. Just as one example, the subject of glues, and kaurit in particular, has been covered in articles in the Association magazine "Bungee Cord" within the past couple of years. Obviously, a magazine article is limited, but does lead to a knowledgeable author, perhaps in your neck of the woods.

[Steve Leonard[_2_]]

On Saturday, February 2, 2019 at 1:15:04 AM UTC-6, Eric Munk wrote:

Much snippery...

> Wood is spruce by heart.

Sorry, Eric, bust I must disagree with you on that. Keifer is not the same as Spruce. If you use Spruce in equivalent thickness, you come out with a weaker spar.

Also, to another comment. Longer scarfs required for Keifer and backing blocks, as dictated by AC43.13 are not to be used, as they impart a "stiff spot" in the wing.

Please buy a copy of the translation of Workshop Practices, join VSA, and absorb the knowledge that is available through this group (VSA).

Steve Leonard

[Per Carlin]

Kiefer is Pine, however can't you just pick the wood in the local warehouse, there is specifications as curls per cm, humidity etc to be OK for planes.

Workshop Practice by the Vintage Sailplane Association is translated from German and covers all you need to know on wood, selection, testing, gluing etc and some more.

[Eric Greenwell[_4_]]

John Foster wrote on 2/1/2019 5:29 PM:
> I was given a junked K8b due to water damage to the wood at the wing root and multiple tears in the original fabric and chipped/peeling paint. However, it looks like it may be restorable (worth it, that's another story). Anyway, I'm interested to know if there is an online repair manual that lays out the specific techniques of repairing or replacing wood in the wings, and specifications on what type of wood to be used, etc. I looked around and found the list of ADs, but nothing that laid out what I am looking for. I've contacted Schleicher as well, but they simply directed me to a link on their website, that didn't really give the information I needed. This is a certified glider, and I'd like to keep it that way, as I'm hoping to use it as a club glider.

Are you familiar with restoring wooden aircraft, and are just looking for
specifics on the K8? If that's not the case, I suggest the first thing you look
for is someone that has restored a K8, and go from there. A club ship should be
restored to a higher standard than an individual might accept.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[Frank Whiteley]

On Friday, February 1, 2019 at 6:29:38 PM UTC-7, John Foster wrote:
> I was given a junked K8b due to water damage to the wood at the wing root and multiple tears in the original fabric and chipped/peeling paint. However, it looks like it may be restorable (worth it, that's another story). Anyway, I'm interested to know if there is an online repair manual that lays out the specific techniques of repairing or replacing wood in the wings, and specifications on what type of wood to be used, etc. I looked around and found the list of ADs, but nothing that laid out what I am looking for. I've contacted Schleicher as well, but they simply directed me to a link on their website, that didn't really give the information I needed. This is a certified glider, and I'd like to keep it that way, as I'm hoping to use it as a club glider.

My SWAG would be that type of restoration this glider might require will involve 3-4 years of part-time effort.

Frank Whiteley

[[email protected]]

On Friday, February 1, 2019 at 7:29:38 PM UTC-6, John Foster wrote:
> I was given a junked K8b due to water damage to the wood at the wing root and multiple tears in the original fabric and chipped/peeling paint. However, it looks like it may be restorable (worth it, that's another story). Anyway, I'm interested to know if there is an online repair manual that lays out the specific techniques of repairing or replacing wood in the wings, and specifications on what type of wood to be used, etc. I looked around and found the list of ADs, but nothing that laid out what I am looking for. I've contacted Schleicher as well, but they simply directed me to a link on their website, that didn't really give the information I needed. This is a certified glider, and I'd like to keep it that way, as I'm hoping to use it as a club glider.

I was one of the two co-editors of the translation of Hans Jacobs book Werkstattpraxis - Workshop Practice. All the information you need can be found in this book, and more importantly, the information is appropriate for the construction utilized to build the K8b. A few copies of the book are still available thru the VSA website, Cumulus Soaring in the USA, and Eqip Publisher in Germany.

Some repairs made using AC-43.13 or many other methods should be avoided, particularly spar repairs, since they add stress concentration. The methods in Workshop Practice are the best for wood airplanes of all types. The book also has several pages of addendum that I wrote to address items that have become available after the last edition of the book in German.

You should consider joining the Vintage Sailplane Association (VSA in USA) and/or the Vintage Glider Club (VGC worldwide, but HQ in UK). Check out their Facebook pages as well (Vintage & Classic Sailplanes or Vintage Glider Club). There are many postings every day and it is an excellent way to get questions answered. Thru these organizations, you should be able to find someone near you that can help you assess the condition of the glider and make appropriate decisions on how to more forward. You may also find important parts and lessons for others who have done the work before.

If you are in the USA, you could contact me directly thru email, my address is on the VSA website. I am also the Drawing Archivist for the VSA, and we can help you with drawings.

Best of luck with what I believe to be a worthwhile endeavor. ..... Neal

[John Foster]

On Saturday, February 2, 2019 at 6:55:07 PM UTC-7, wrote:
> On Friday, February 1, 2019 at 7:29:38 PM UTC-6, John Foster wrote:
> > I was given a junked K8b due to water damage to the wood at the wing root and multiple tears in the original fabric and chipped/peeling paint. However, it looks like it may be restorable (worth it, that's another story). Anyway, I'm interested to know if there is an online repair manual that lays out the specific techniques of repairing or replacing wood in the wings, and specifications on what type of wood to be used, etc. I looked around and found the list of ADs, but nothing that laid out what I am looking for.. I've contacted Schleicher as well, but they simply directed me to a link on their website, that didn't really give the information I needed. This is a certified glider, and I'd like to keep it that way, as I'm hoping to use it as a club glider.
>
> I was one of the two co-editors of the translation of Hans Jacobs book Werkstattpraxis - Workshop Practice. All the information you need can be found in this book, and more importantly, the information is appropriate for the construction utilized to build the K8b. A few copies of the book are still available thru the VSA website, Cumulus Soaring in the USA, and Eqip Publisher in Germany.
>
> Some repairs made using AC-43.13 or many other methods should be avoided, particularly spar repairs, since they add stress concentration. The methods in Workshop Practice are the best for wood airplanes of all types. The book also has several pages of addendum that I wrote to address items that have become available after the last edition of the book in German.
>
> You should consider joining the Vintage Sailplane Association (VSA in USA) and/or the Vintage Glider Club (VGC worldwide, but HQ in UK). Check out their Facebook pages as well (Vintage & Classic Sailplanes or Vintage Glider Club). There are many postings every day and it is an excellent way to get questions answered. Thru these organizations, you should be able to find someone near you that can help you assess the condition of the glider and make appropriate decisions on how to more forward. You may also find important parts and lessons for others who have done the work before.
>
> If you are in the USA, you could contact me directly thru email, my address is on the VSA website. I am also the Drawing Archivist for the VSA, and we can help you with drawings.
>
> Best of luck with what I believe to be a worthwhile endeavor. ..... Neal

Thanks for all the replies. I'm definitely going to have to get a copy of Jacob's book. I have a friend in town who is an A&P/IA, and has had a fair bit of experience doing repairs on wooden aircraft before. He has taken a brief look at this glider and feels "it has good bones". The spar seems good to him, although there are a few glue joints on the ribs that need to be "redone". The wing root rib seems to have delaminated on the left wing, which I'm thinking will need some attention, but otherwise it appears that it will mostly be a recovering job. Once I get the fabric off the bottom of the left wing, I'll have him take a closer look at it and let me know what he thinks.

[Eric Munk]

Replacing wing root rib ply is a fairly straightforward job on the
K8. Good luck! Lovely little gliders...

At 10:08 03 February 2019, John Foster wrote:
>On Saturday, February 2, 2019 at 6:55:07 PM UTC-7,

>=
>wrote:
>> On Friday, February 1, 2019 at 7:29:38 PM UTC-6, John Foster
wrote:
>> > I was given a junked K8b due to water damage to the wood
at the wing
>ro=
>ot and multiple tears in the original fabric and chipped/peeling
paint.
>Ho=
>wever, it looks like it may be restorable (worth it, that's another
>story).=
> Anyway, I'm interested to know if there is an online repair
manual that
>l=
>ays out the specific techniques of repairing or replacing wood in
the
>wings=
>, and specifications on what type of wood to be used, etc. I
looked
>around=
> and found the list of ADs, but nothing that laid out what I am
looking
>for=
>.. I've contacted Schleicher as well, but they simply directed me
to a
>link=
> on their website, that didn't really give the information I
needed. This
>=
>is a certified glider, and I'd like to keep it that way, as I'm hoping
to
>u=
>se it as a club glider.
>>=20
>> I was one of the two co-editors of the translation of Hans
Jacobs book
>We=
>rkstattpraxis - Workshop Practice. All the information you need
can be
>fou=
>nd in this book, and more importantly, the information is
appropriate for
>t=
>he construction utilized to build the K8b. A few copies of the
book are
>st=
>ill available thru the VSA website, Cumulus Soaring in the USA,
and Eqip
>Pu=
>blisher in Germany.
>>=20
>> Some repairs made using AC-43.13 or many other methods
should be
>avoided,=
> particularly spar repairs, since they add stress concentration.
The
>metho=
>ds in Workshop Practice are the best for wood airplanes of all
types. The
>=
>book also has several pages of addendum that I wrote to
address items that
>=
>have become available after the last edition of the book in
German.
>>=20
>> You should consider joining the Vintage Sailplane Association
(VSA in
>USA=
>) and/or the Vintage Glider Club (VGC worldwide, but HQ in UK).
Check out
>=
>their Facebook pages as well (Vintage & Classic Sailplanes or
Vintage
>Glide=
>r Club). There are many postings every day and it is an
excellent way to
>g=
>et questions answered. Thru these organizations, you should be
able to
>fin=
>d someone near you that can help you assess the condition of
the glider
>and=
> make appropriate decisions on how to more forward. You may
also find
>impo=
>rtant parts and lessons for others who have done the work
before.
>>=20
>> If you are in the USA, you could contact me directly thru
email, my
>addre=
>ss is on the VSA website. I am also the Drawing Archivist for the
VSA,
>and=
> we can help you with drawings.
>>=20
>> Best of luck with what I believe to be a worthwhile endeavor.
..... Neal
>
>Thanks for all the replies. I'm definitely going to have to get a
copy of
>J=
>acob's book. I have a friend in town who is an A&P/IA, and has
had a fair
>=
>bit of experience doing repairs on wooden aircraft before. He
has taken a
>=
>brief look at this glider and feels "it has good bones". The spar
seems
>go=
>od to him, although there are a few glue joints on the ribs that
need to
>be=
> "redone". The wing root rib seems to have delaminated on the
left wing,
>w=
>hich I'm thinking will need some attention, but otherwise it
appears that
>i=
>t will mostly be a recovering job. Once I get the fabric off the
bottom
>of=
> the left wing, I'll have him take a closer look at it and let me
know
>what=
> he thinks.
>

[Steve Leonard[_2_]]

On Sunday, February 3, 2019 at 5:30:05 AM UTC-6, Eric Munk wrote:
> Replacing wing root rib ply is a fairly straightforward job on the
> K8. Good luck! Lovely little gliders...
>
And this time, I agree with Eric. Ply delam on the root rib is one thing. Should be relatively easy fix.

I only have two flights in mine (so many other planes to play with!), but it is a lovely flying plane! Was so nice to fly a silent plane. No electrics. Not even a hand held radio on board. Too bad the pee tube was blocked.. Made things a bit sporting there for a while, flying with a full funnel! I was very glad the baggie didn't have a leak in it!

Steve Leonard
Ka-8B
N6660D

[Eric Munk]

At 17:32 02 February 2019, Steve Leonard wrote:
>On Saturday, February 2, 2019 at 1:15:04 AM UTC-6, Eric Munk wrote:
>
>Much snippery...
>
>> Wood is spruce by heart.
>
>Sorry, Eric, bust I must disagree with you on that. Keifer is not the
same
>as Spruce. If you use Spruce in equivalent thickness, you come out with
a
>weaker spar.
>
>Also, to another comment. Longer scarfs required for Keifer and backing
>blocks, as dictated by AC43.13 are not to be used, as they impart a
"stiff
>spot" in the wing.
>
>Please buy a copy of the translation of Workshop Practices, join VSA, and
>absorb the knowledge that is available through this group (VSA).
>
>Steve Leonard
>

Always happy to stand corrected, Steve. Have been putting lots of Kiefer in
Schleicher's finest as of late, on the European side of the Atlantic, but
thought spruce would be a good translation for it...

PS: the VSA's translation of Jacobs' masterpiece is lovely!

[[email protected]]

Get in touch with the Australian Gliding museum,they are in the process of restoring a K8 to airworthy condition from a wreck found in a trailer .they have a wealth of experience and expertise.

[John Foster]

On Friday, February 1, 2019 at 6:29:38 PM UTC-7, John Foster wrote:
> I was given a junked K8b due to water damage to the wood at the wing root and multiple tears in the original fabric and chipped/peeling paint. However, it looks like it may be restorable (worth it, that's another story). Anyway, I'm interested to know if there is an online repair manual that lays out the specific techniques of repairing or replacing wood in the wings, and specifications on what type of wood to be used, etc. I looked around and found the list of ADs, but nothing that laid out what I am looking for. I've contacted Schleicher as well, but they simply directed me to a link on their website, that didn't really give the information I needed. This is a certified glider, and I'd like to keep it that way, as I'm hoping to use it as a club glider.

Is it common for the fabric to not go all the way to the leading edge? This one has the fabric to just forward of the spar, and the rest of the leading edge is covered by painted plywood. Would there be any harm to have the fabric cover the whole wing? I don't imagine it would add any significant weight, but it would protect the underlying plywood better.

[Charles Longley]

It was probably a fabric width or budget issue. You can glue a piece around the leading edge easily enough.

[[email protected]]

On Thursday, February 21, 2019 at 10:59:13 PM UTC-6, John Foster wrote:
> On Friday, February 1, 2019 at 6:29:38 PM UTC-7, John Foster wrote:
> > I was given a junked K8b due to water damage to the wood at the wing root and multiple tears in the original fabric and chipped/peeling paint. However, it looks like it may be restorable (worth it, that's another story). Anyway, I'm interested to know if there is an online repair manual that lays out the specific techniques of repairing or replacing wood in the wings, and specifications on what type of wood to be used, etc. I looked around and found the list of ADs, but nothing that laid out what I am looking for.. I've contacted Schleicher as well, but they simply directed me to a link on their website, that didn't really give the information I needed. This is a certified glider, and I'd like to keep it that way, as I'm hoping to use it as a club glider.
>
> Is it common for the fabric to not go all the way to the leading edge? This one has the fabric to just forward of the spar, and the rest of the leading edge is covered by painted plywood. Would there be any harm to have the fabric cover the whole wing? I don't imagine it would add any significant weight, but it would protect the underlying plywood better.

It depends.... From the factory, it would have had fabric that extended about 50mm ahead of the rear side of the main spar. That is considered an adequate coverage with cotton, glider cloth, or even Dacron when using traditional dope (Ceconite process). The Polyfiber process (formerly known as Stits, since it was developed by Ray Stits) includes a requirement in its STC that many A&Ps & IAs would interpret to require putting all edges in double shear. This would require require covering the leading edge with fabric and overlapping the fabric on the open bays. The Stewart System STC allows the fabric to be installed in the same fashion as defined originally by the factory. I believe that SuperFlight and AirTech also allow that.

I would suggest carefully sealing the plywood on the leading edge with epoxy. Often people use Polyfiber EV400 epoxy varnish, but using a squeegee with WEST System epoxy will provide a more effecting sealing. Then you can either paint the scuffed leading-edge surface or decide to cover it with cloth. If you decide on cloth, you can use lightweight, uncertified fabric on the leading edge, since it is not carrying an air load.

Send me a private email if you would like to discuss more. I have direct experience with replacing fabric on Schleicher gliders with Stits & Stewart. I can give you some hints on what order to do the covering and handle the stitching.

...... Neal

[Eric Munk]

I think you will find that all wooden Schleicher gliders have been finished
from the factory with fabric up to 50 mm forward of the rear face of the
main spar, and with paint on the D-box. Sometimes the D-box has been
reworked (especially on Ka6s) with a thin layer of filler to reduce drag.
In fact, reducing drag by creating a smooth painted surface opposed to a
more rough fabric'ed D-nose is probably the main reason it was finished
this way. Fabric width was no problem.

[John Foster]

On Friday, February 22, 2019 at 10:00:06 AM UTC-7, Eric Munk wrote:
> I think you will find that all wooden Schleicher gliders have been finished
> from the factory with fabric up to 50 mm forward of the rear face of the
> main spar, and with paint on the D-box. Sometimes the D-box has been
> reworked (especially on Ka6s) with a thin layer of filler to reduce drag.
> In fact, reducing drag by creating a smooth painted surface opposed to a
> more rough fabric'ed D-nose is probably the main reason it was finished
> this way. Fabric width was no problem.

What glue is recommended for fixing broken glue joints? I understand that the original glue was not the best--very brittle.

[[email protected]]

>
> What glue is recommended for fixing broken glue joints? I understand that the original glue was not the best--very brittle.

This topic was covered in Bungee Cord articles published by the Vintage Sailplane Association (also VGC News). There is not a simple answer, since all IA's and FAA personnel are not the same. I've sent you a separate, private email on this topic. ..... Neal

[John Foster]

On Monday, March 18, 2019 at 1:05:49 PM UTC-6, wrote:
> >
> > What glue is recommended for fixing broken glue joints? I understand that the original glue was not the best--very brittle.
>
> This topic was covered in Bungee Cord articles published by the Vintage Sailplane Association (also VGC News). There is not a simple answer, since all IA's and FAA personnel are not the same. I've sent you a separate, private email on this topic. ..... Neal

Are these articles available online?

[[email protected]]

Hi John,
I have repaired and recovered a K-6 and a K-13, both were licensed in Standard Category. Simply stated, the rules are you must do what the manufacturer did and use the same materials originally used, or get written permission from Schleicher or the FAA to deviate. I had to get FSDO permission to use epoxy glue to rework the ribs and check with Stits Fabric to see they had aTSO for each ship in order to use their Poly Fiber covering materials. All this can lead to problems with the IA who will be asked to sign off your form 337 and the Feds who must accept the work done, methods and materials used, as stated on the 337.
If I were you I would ask my local FSDO to change the ship over to Experimental, exhibition & racing. I’d tell them you wish to do this in order to use modern glues, materials and coverings. I have done this a couple of times with no problems at all. Once your licensed Experimental, an A&P can sign off all the work with a log book entry, no form 337, no IA, no TSO’s needed!
JJ Sinclair
BTW, covering the D tube with fabric is not allowed on your type certificated ship (you must do what the manufacturer did)........bad idea anyway because after shrinking, the fabric will bridge over all low spots and the dope will form a ring at the edge of these low areas and show up as very ugly rings in your final paint Job!

[John Foster]

On Monday, March 18, 2019 at 7:07:16 PM UTC-6, wrote:
> Hi John,
> I have repaired and recovered a K-6 and a K-13, both were licensed in Standard Category. Simply stated, the rules are you must do what the manufacturer did and use the same materials originally used, or get written permission from Schleicher or the FAA to deviate. I had to get FSDO permission to use epoxy glue to rework the ribs and check with Stits Fabric to see they had aTSO for each ship in order to use their Poly Fiber covering materials. All this can lead to problems with the IA who will be asked to sign off your form 337 and the Feds who must accept the work done, methods and materials used, as stated on the 337.
> If I were you I would ask my local FSDO to change the ship over to Experimental, exhibition & racing. I’d tell them you wish to do this in order to use modern glues, materials and coverings. I have done this a couple of times with no problems at all. Once your licensed Experimental, an A&P can sign off all the work with a log book entry, no form 337, no IA, no TSO’s needed!
> JJ Sinclair
> BTW, covering the D tube with fabric is not allowed on your type certificated ship (you must do what the manufacturer did)........bad idea anyway because after shrinking, the fabric will bridge over all low spots and the dope will form a ring at the edge of these low areas and show up as very ugly rings in your final paint Job!

I would prefer to keep this standard certification if possible. I hope that once the glider is restored, it will be a club glider, that can be rented out to club members. Possibly even in a commercial setting. Thus the desire to kept standard certification.

[[email protected]]

Mr Foster (John),

The articles are not posted online. If you contact me by email, I can see about getting them to you. You should consider becoming a VSA member, since there are members across the country that have experience and can help.

In short, FAA guidance material states that epoxy may be used for some repairs, but must be approved. Unfortunately, there is no uniformity to that approval between FAA offices. Since wood aircraft have not been built commercially here in the US since the 50's at the latest, thee was no incentive to qualify epoxy as a wood adhesive. Homebuilts have used epoxy for years. Properly used, it provides good joints while not requiring tight joints or high pressure. In fact, with cotton flox or other fiber material, it can actually bridge small gaps. This makes it ideal for repair without factory fixtures.

You also received comments from JJ, who has a lot of experience with glider repair, wood and otherwise. Taking it experimental fixes some issues, but I would suggest that keeping it Standard category would be worthwhile, especially for selling it down the line. However, if you want to use epoxy, it will require finding an inspector that is willing to allow you to use that adhesive for your repairs, and willing to take it to his or her FAA office to get the Form 337 approved. I have been able to find IA's to do that for me. I have typically used T-88 for smaller repairs like ribs. It will provide a better joint than the original Kaurit. One IA also did some more major repairs for me using Aeropoxy. It comes in different viscosities, so it is easier to use for some repairs.

You could also use a resorcinol adhesive. Schleicher used Aerodux (resorcinol) to attach plywood skins (but generally Kaurit (a plastic resin glue) to do much of the structure.) Cascophen or similar resorcinol adhesives have a general approval from the FAA, but you need to have tight fitting joints and be able to provide uniform, tight clamping. That can be difficult with some repairs.

There is coverage for the Schleicher gliders in the Polyfiber (Stits) STC. But if one reads the details of the STC, it says to overlap all fabric joints, which would infer that fabric should cover the leading edge D-tube. This can be done with lightweight fabric, since it does not carry air loads, and it is glued tightly to the leading edge. The Stewart Systems covering system allows the fabric to be applied just over the open bays, like the original factory installation. Ceconite using dope also allows this. Aerotech and Superflight may also do the same. I have moved from Polyfiber to Stewart Systems to make my wife happier. If does not use the MEK and other volitiles in the the other systems. Also all bu the last paint coat can be cleaned up with water.

Again, send me an email if you want more info, and please consider checking out the Vintage Sailplane Association website (http://www.vintagesailplane..org/).

...... Neal

[John Foster]

On Monday, March 18, 2019 at 9:57:30 PM UTC-6, wrote:
> Mr Foster (John),
>
> The articles are not posted online. If you contact me by email, I can see about getting them to you. You should consider becoming a VSA member, since there are members across the country that have experience and can help.
>
> In short, FAA guidance material states that epoxy may be used for some repairs, but must be approved. Unfortunately, there is no uniformity to that approval between FAA offices. Since wood aircraft have not been built commercially here in the US since the 50's at the latest, thee was no incentive to qualify epoxy as a wood adhesive. Homebuilts have used epoxy for years. Properly used, it provides good joints while not requiring tight joints or high pressure. In fact, with cotton flox or other fiber material, it can actually bridge small gaps. This makes it ideal for repair without factory fixtures.
>
> You also received comments from JJ, who has a lot of experience with glider repair, wood and otherwise. Taking it experimental fixes some issues, but I would suggest that keeping it Standard category would be worthwhile, especially for selling it down the line. However, if you want to use epoxy, it will require finding an inspector that is willing to allow you to use that adhesive for your repairs, and willing to take it to his or her FAA office to get the Form 337 approved. I have been able to find IA's to do that for me. I have typically used T-88 for smaller repairs like ribs. It will provide a better joint than the original Kaurit. One IA also did some more major repairs for me using Aeropoxy. It comes in different viscosities, so it is easier to use for some repairs.
>
> You could also use a resorcinol adhesive. Schleicher used Aerodux (resorcinol) to attach plywood skins (but generally Kaurit (a plastic resin glue) to do much of the structure.) Cascophen or similar resorcinol adhesives have a general approval from the FAA, but you need to have tight fitting joints and be able to provide uniform, tight clamping. That can be difficult with some repairs.
>
> There is coverage for the Schleicher gliders in the Polyfiber (Stits) STC.. But if one reads the details of the STC, it says to overlap all fabric joints, which would infer that fabric should cover the leading edge D-tube. This can be done with lightweight fabric, since it does not carry air loads, and it is glued tightly to the leading edge. The Stewart Systems covering system allows the fabric to be applied just over the open bays, like the original factory installation. Ceconite using dope also allows this. Aerotech and Superflight may also do the same. I have moved from Polyfiber to Stewart Systems to make my wife happier. If does not use the MEK and other volitiles in the the other systems. Also all bu the last paint coat can be cleaned up with water.
>
> Again, send me an email if you want more info, and please consider checking out the Vintage Sailplane Association website (http://www.vintagesailplane.org/).
>
> ..... Neal

Thank you, Neal. I appreciate your reply. Email incoming. Thanks for your help.

[[email protected]]

The last shipi changed over to Experimental was a G-102 that I needed to make a new drag spar carry-through bar, not available from Grob. I asked my FSDO inspector if I could lease the ship out to the local glider FBO? He said yes, you just can’t give instruction or charge for rides in an experiment bird.
JJ