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Wing skin separation HELP

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wdaniell(at)etb.net.co
Guest

Posted: Sat Jan 14, 2006 1:37 pm Post subject: Wing skin separation HELP

I have made an error in construction in the interior of the wings and very

cleverly close then (with the error inside).



So now I have to open them again.



Any ideas anyone?



Thanks



Will

ptag.dev(at)tiscali.co.uk
Guest

Posted: Sat Jan 14, 2006 2:52 pm Post subject: Wing skin separation HELP

Will.....

Which kind of wings Foam or the later XS skinned wings and what area

/what error are you trying to fix?

Regards

Bob Harrison G-PTAG Europa MKI/Jabiru3300



--

wdaniell(at)etb.net.co
Guest

Posted: Sat Jan 14, 2006 3:36 pm Post subject: Wing skin separation HELP

I guess I had better 'fess up.



I did the reinforcements 0/90 instead of 45deg.  And then adding really dumb

behaviour to stupidity, I closed the wings out and then realized what I had

done...



I talked to andy about this and he said that the general opinion was to open

up and do them again.  He suggested heat and wished me luck!  He was very

nice about it



I am currently trying to heat up the skins to loosen the Araldite but I am

getting the distinct feeling that I will end up without useful skins and

with damage to the underneath structure.  So I fear than unless anyone has a

bright I idea that new skins are the order of the day.  Expensive.



So any ideas or help gratefully received.  Anyone got a spare pair of skins

- or perhaps someone who changed standard wings for glider wings?



Will

--

ptag.dev(at)tiscali.co.uk
Guest

Posted: Sat Jan 14, 2006 4:45 pm Post subject: Wing skin separation HELP

Hi! Will..

I would have thought a heat gun applied to the joint in one place at a

time and gradually prise the skins apart with a wedge or blunt chisel

would be a possibility. However I'm not an XS man and so unaware of

where you will be applying heat and at how many points. Why not make one

or two test pieces of waste bonded together to develop a technique prior

to setting to work on the wing?

Regards 

Bob Harrison.



--

kheindl(at)msn.com
Guest

Posted: Sun Jan 15, 2006 3:01 am Post subject: Wing skin separation HELP

Will,



Using just a heat gun would make it very difficult to get started. If it was 

me I would make up a "heat box" out of wood, with a long about 2 inch 

opening, with a heat gun at each end. It would need some holes to let the 

hot air escape. Hold it on top of the joint long enough to let the redux 

soften (trial and error) . Using a spatula, try lifting the skin along that 

section. Once you get one end separated, you may be able to loosen the 

remainder with just a heat gun and metal spatula.



Karl



 	  Quote: 	
		  From: "William Daniell" <wdaniell(at)etb.net.co>

Reply-To: europa-list(at)matronics.com

To: <europa-list(at)matronics.com>

Subject: Wing skin separation HELP

Date: Sat, 14 Jan 2006 16:36:28 -0500






I have made an error in construction in the interior of the wings and very

cleverly close then (with the error inside).



So now I have to open them again.



Any ideas anyone?



Thanks



Will

n3eu(at)comcast.net
Guest

Posted: Sun Jan 15, 2006 10:17 am Post subject: Wing skin separation HELP

My attempt to soften Redux, after it had cured a couple weeks, was too a

failure.  Too much heat required, verses heat to damage the glass

structure, which conducts heat poorly to get at the green stuff.  For my

safety at least, I would be assuming this procedure might give me a

potential airworthiness problem to forever worry me in severe

turbulence.



I'm surprised the factory would advise -- not knowing any builder's

skill level -- removal by any method other than panel destruction and

replacement (requiring essentially $$, that's all!).  Otherwise a

Hobson's choice on structural integrity, attempting a fix, the moral

equivalent of "don't force it...use a bigger hammer."



I don't have this style wing, but merely perused the XS manual online.

It's my opinion that the primary purpose of the tapes is such that

improper orientation of the fibers matters only a little, but I have no

credentials to say that.  But, when we add two more tapes, we do stiffen

the ass'y there further, concentrating stresses elsewhere.  That could

mean a "seven yard gain, with a five yard penalty," as in U.S. football.

So, if the factory can analyze that one with engineering analysis to say

no harm, they should be able to say computationally why -- in stress

paths -- 90 on the tapes is not good.  Or more likely just their gut

reaction and "usual rules" for FG construction.



The only thing I would not do was a fix which may compromise the

structure worse than the original problem.



Reg,

Fred F. (nickname "Hobson")

ami(at)mcfadyean.freeserv
Guest

Posted: Sun Jan 15, 2006 10:49 am Post subject: Wing skin separation HELP

<>



Merely reduces strength by 30%! 

Would need to do another load test on the wing to confirm the effect.



Duncan McF

---

n3eu(at)comcast.net
Guest

Posted: Sun Jan 15, 2006 11:26 am Post subject: Wing skin separation HELP

Duncan McFadyean wrote:

 	  Quote: 	
		  

 Merely reduces strength by 30%!

 Would need to do another load test on the wing to confirm the effect.


	


I guess you mean tensile strength of the tape + resin, not the whole

structure, but I'd a guessed more than 30.  However, there's stresses

from several directions here -- up/down in Gs, aft in drag, and twist

(flap and aileron).  But as to G forces, she tested beyond 10Gs, so

maybe now 9Gs due to the tape problem?  Who knows. We need only 3.8G for

utility category safety, though, but I understand the conundrum, is all.



Reg,

Fred F.

ami(at)mcfadyean.freeserv
Guest

Posted: Sun Jan 15, 2006 11:55 am Post subject: Wing skin separation HELP

Inverse of the square root of 2. Or 0.707.

Applied at 90 deg, half of the cloth is redundant to stresses orientated 

with weft or warp.

Duncan McF.

---

rowil(at)clara.net
Guest

Posted: Sun Jan 15, 2006 3:16 pm Post subject: Wing skin separation HELP

At 2006-01-14 18:35 -0500 William Daniell wrote:



 	  Quote: 	
		  I am currently trying to heat up the skins to loosen the Araldite but I am

getting the distinct feeling that I will end up without useful skins and

with damage to the underneath structure


	


Will - I suggest you talk to some of the glider repair people before 

doing anything irrevocable. People like Gary McKirdy or Martin 

Carolan would probably have a way to get in & out without buying new 

wing skins. Don't know if they inhabit this list, though. If you wish 

I can forward your query to them off-list. They are in UK so if you 

are elsewhere they can only offer advice - but that might be all you 

need!



regards



Rowland

-- 

| Rowland Carson  PFA #16532 <http://home.clara.net/rowil/aviation/>

| 750 hours building Europa #435 G-ROWI  e-mail <rowil(at)clara.net>

dglauser(at)gmail.com
Guest

Posted: Sun Jan 15, 2006 6:17 pm Post subject: Wing skin separation HELP

I had a similar problem after closing my wings. In my case, the plys were in

the correct orientation but there were some gaps between the rear closeout

and both the base and the top. (I found these with the aid of a small TV

camera on the end of a stick, run through panels cut un the wings.) After

consultation with Kim Prout, I cut access panels out of the wing and did the

repairs through the holes. Then I closed the holes using the usual

techniques - add a large flange around the hole that overlaps well onto the

wing (inside), then use the cut-out piece of wing as a closeout panel after

applying reinforcement to it too.

dg

On 1/15/06, Rowland Carson <rowil(at)clara.net> wrote:

 	  Quote: 	

 At 2006-01-14 18:35 -0500 William Daniell wrote:

 >I am currently trying to heat up the skins to loosen the Araldite but I

 am

 >getting the distinct feeling that I will end up without useful skins and

 >with damage to the underneath structure

 Will - I suggest you talk to some of the glider repair people before

 doing anything irrevocable. People like Gary McKirdy or Martin

 Carolan would probably have a way to get in & out without buying new

 wing skins. Don't know if they inhabit this list, though. If you wish

 I can forward your query to them off-list. They are in UK so if you

 are elsewhere they can only offer advice - but that might be all you

 need!

 regards

 Rowland

 --

 | Rowland Carson  PFA #16532 <http://home.clara.net/rowil/aviation/>

 | 750 hours building Europa #435 G-ROWI  e-mail <rowil(at)clara.net>

davedeford(at)comcast.net
Guest

Posted: Sun Jan 15, 2006 10:41 pm Post subject: Wing skin separation HELP

William,



I think the best heat source for separating the Araldite skin joints is a

flat silicone heat blanket, perhaps an inch wide by a foot or two long (see

www.mcmaster.com, part number 35765K154 for an example of what I am talking

about).  A fiberglass tape heater or Kapton heater would work also.  With a

contact heater, you can keep the heater temperature just slightly above the

desired temperature of the joint, leaving it there for a few minutes, until

the Araldite has softened.  The hot air from a heat gun must be much hotter

than the ultimate temperature of the joint, and it will rapidly overheat the

thin fiberglass/foam sandwich adjacent to the solid fiberglass/epoxy joint,

probably damaging it before the joint can get up to temperature.  When the

Araldite has softened, it should be possible to slide a putty knife between

the skin and the rib or spar.  The best place to start is at a corner.  The

good news (in my experience) is that the glass transition temperature of the

Araldite is lower than that of the laminating resin, so the joint should

soften before the skin delaminates.



For best control of the heating rate, run the heater from a variable

autotransformer (Variac) or a lamp dimmer.  Putting a thermocouple between

the heater and the skin lets you know how the heating is progressing.  While

I have not tried to separate fiberglass joints this way, I have used this

heating setup to deform the upper "shelf" portion of the fuel tank, as it

was interfering with the wing spar, and preventing rigging of the wings (a

problem with the early XS construction manuals).  The temperature range

between hard (too cold) and runny (too hot) for the plastic tank is narrow

enough to require fairly delicate temperature control.



Good luck!



Dave DeFord

N135TD (XS monowheel)

wdaniell(at)etb.net.co
Guest

Posted: Mon Jan 16, 2006 7:18 am Post subject: Wing skin separation HELP

Here is what I wrote to Jerry.  



Let me say it was very pleasant to have a group of guys rooting for one in

the face of a great disappointment.  Only someone who has built one of these

can understand the feeling of having made a significant mistake and having

to go back and correct it.



Thanks to all.



Will



"I have attacked the wing skin.  Weapons of choice wood chisel, wood plane

and sanding disk.  Thatll teach the bugger!  New skins ordered.



No way that I can see of saving the skin  or more accurately - might save

the skin but ruin the wing



I thought of making a new top skin (making a polyester mould) but discarded

this idea when I realized that the upper skin changes in construction from

tip to root  the root area is considerably stronger. 



Two steps forward one (and ) steps back."



 



Will



 

--

asarangan(at)yahoo.com
Guest

Posted: Tue Jan 17, 2006 5:28 pm Post subject: Wing skin separation HELP

I doubt you will be able to soften the Araldite without deforming the

top skin. I would not try to save the skin, but focus on saving the

bottom mating flange. If you lose that flange, life could get more

difficult. One option is to cut through the top skin, and then grind

away the remaining portion bonded to the flange. 



My feeling is that the reinforcement plies can't be all that critical

to warrant compromising the entire integrity of the wing. I would

proceed with the construction and evaluate the options as the projects

gets closer to the end. 



I decided a long time ago not to bond the top skin until the aircraft

is almost ready to fly. Bonding the skin does not take a lot of time,

and you never know what you might want to install at the last minute.

It is better to keep the options open as long as possible.





--- William Daniell <wdaniell(at)etb.net.co> wrote:



[quote] 

 <wdaniell(at)etb.net.co>

 

 I guess I had better 'fess up.

 

 I did the reinforcements 0/90 instead of 45deg.  And then adding

 really dumb

 behaviour to stupidity, I closed the wings out and then realized what

 I had

 done...

 

 I talked to andy about this and he said that the general opinion was

 to open

 up and do them again.  He suggested heat and wished me luck!  He was

 very

 nice about it

 

 I am currently trying to heat up the skins to loosen the Araldite but

 I am

 getting the distinct feeling that I will end up without useful skins

 and

 with damage to the underneath structure.  So I fear than unless

 anyone has a

 bright I idea that new skins are the order of the day.  Expensive.

 

 So any ideas or help gratefully received.  Anyone got a spare pair of

 skins

 - or perhaps someone who changed standard wings for glider wings?

 

 Will

 

 

 --

wdaniell(at)etb.net.co
Guest

Posted: Tue Jan 17, 2006 6:22 pm Post subject: Wing skin separation HELP

Agreed - now - but too late!

Destruction of top skin started!  You are right - I am more comfor4table

with grinding off the top skin than trying to heat release the araldite for

the reasons you give.



However I suspect (now that I know about the construction of the wing skins

in some detail)  that the wings skins play an important role in stiffening

the wings and therefore the incidence should be set with the upper skin in

place.  



Having said that I have no basis for this whatever.



Will



--

rogerjohnsheridan(at)yaho
Guest

Posted: Wed Jan 18, 2006 3:29 am Post subject: Wing skin separation HELP

I heard a good saying on the radio today:



"Anyone who never made a mistake, never made anything"



Good luck!



Rog S

wdaniell(at)etb.net.co
Guest

Posted: Wed Jan 18, 2006 3:45 am Post subject: Wing skin separation HELP

Thanks - Will



PS maybe I was just dumb enough to confess! 



--

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