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Wing covering

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Old 01-31-2013, 09:39 PM
  #1
33willys
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Default Wing covering



Before covering my wing I did some research and watched several videos. Very informative but I may have missed something. Basicly the instructions say to seal the edges and then shrink the middle. Before shrinking the middle should the iron be run over the ribs to stick the Monocoat to it or just shrink the entire center? As a side note I have a non-contact thermometer that I used to check the temp of the iron. Temps came up fast in the middle but the toe and heel took a while to reach a usable temp. In other words I needed to let the iron set for a while before it was able to do the job across the face.

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Old 02-01-2013, 02:47 AM
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Edwin
 
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Default RE: Wing covering

Yeah, stick down the perimeter, then I use the hot air gun to shrink up the middle. I do the iron over the center section, but you can run the iron over the ribs if you want. Sometimes I do it, sometimes I dont. On the fuse, I use the hot air gun then come back over it with the iron. Cant speak to the non-uniform shoe temps. My iron is about 12 years old and due for replacement, topflight. I dont recall where its set, I think just past the mid point. I also use ultracoat.
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Old 02-01-2013, 07:36 AM
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Default RE: Wing covering

When doing wings:

Yes I always start by sealing the perimiter and later sealing ribs as well as any leading edge sheeting if any. You will find your most successful order is after sealing the perrimeter the middle areas are shrunk before sealing ribs or the sheeting. You can use either the gun or iron for this and if used the iron is used with very light pressure to avoid sealing the ribs. The idea is to allow the entire panel to be shunk uniformly and this will avoid the numerous small wrinkles in the corrners of every ribs. Now after the wing looks great and smooth go back and seal all the ribs with an iron using an even pressure with no attempt to walk the material sideways. Seal all the ribs as well as the sheeted areas.


Now lets talk about sealing ribs and sheeted areas. A wing that has not been sealed at these areas will be a much weaker wing in torsional stiffness. In the case of most trainer type wing especially ones that have no sheeting at all such as a Senior Kaydet or LT-40 for example the integrety of the design is dependant entirely upon the covering material and full sealing of the ribs to bring up to the intended strength.

Most irons run the hottest in the heal and coolest in the toe this is normal and can be used to advantage if you take this into account as you cover. I do not us a temperature gage but I use monocoat exclusively anymore and I also use T-shirt socks always so don,t worry and run the iron at the hotest.

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Old 02-01-2013, 10:32 AM
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Default RE: Wing covering

Some folks do run the iron over the ribs after shrinking and some don't, I'm a don't. I use Ultracote and when it shrinks it goes down tight and the heat from the heat gun glues the covering to the ribs pretty well. You don't know how well until you pull the covering to do repairs or recover. If you iron down on the ribs before you shrink it creats a problem sometimes like wrinkles or nasty looking spots in the covering. Makes a cool sounding pop when it does shrink tight though!
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Old 02-01-2013, 10:33 AM
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Default RE: Wing covering


Quote:
ORIGINAL: 33willys



Before covering my wing I did some research and watched several videos. Very informative but I may have missed something. Basicly the instructions say to seal the edges and then shrink the middle. Before shrinking the middle should the iron be run over the ribs to stick the Monocoat to it or just shrink the entire center? As a side note I have a non-contact thermometer that I used to check the temp of the iron. Temps came up fast in the middle but the toe and heel took a while to reach a usable temp. In other words I needed to let the iron set for a while before it was able to do the job across the face.


Simply put, you want to tack the perimeter, then shrink the middle (preferably with a heat gun which gives you better control) without sticking the covering to the ribs. You want the covering to be able to move around as your shrinking it over the various ribs. There will be times, depending on the shape of your wing (like the wing tips of an Astro Hog), were you'll need to lift, stretch and restick the covering material to smooth it around compound curves. I've had some wings that have taken 2 to 3 hours to get the covering to stretch over compound curves around wingtips without wrinkles.

After everything has been shrunk you want to run your iron over the ribs and leading/trailing edges to make sure the covering has glued down and is not just floating over it. This is where the strength comes from.

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Old 02-01-2013, 12:33 PM
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Default RE: Wing covering

Sealing the ribs with a heat gun sure it can be done with a glove to apply momentary pressure directly on the rib which is an acquired skil and the reason I reccomended for the beginner to use the iron to accomplish this with perfect up and down applications of pressure with no movement of the material in any direction and this only after the complete shrinking has already been done.

Failure to seal all the surfaces including the ribs in a lightly built trainer wing (and specifically those such as the Kaydet Senior and LT-40) Will result in a wing severely impaired in torsional stiffness and gentlemen that means dangerous.

"Some do and some Don't " indeed well we are not talking about giant scales here or as another put it an astro hog, that airplane has a wing built like a diving board, Definately not a trainer.

This is the trainer forum and from the OP's questions and statements he seems to be a newbie very likely the airplane in question is a typical trainer with very little structural 'D' tube sheeting and a dangerous one if only sealed on the outside perimeter. To trivialise the need for rib sealing on the typical trainer to the new fellows does them a disservice.

Thats only my opinion as always and I am an expert in nothing what I am is a survivor.
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Old 02-01-2013, 12:48 PM
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Default RE: Wing covering

I generally iron the perimeter tight, then come back and heat gun or iron the center area tight, and last, I iron all the ribs for the very reason John stated, torsional strength. I do this very same thing on small trainer type wings or my giant scale wings, too me it is just a good way to go. Here is my wife holding the stab and wing half for my 55% Extra 260 and both are covered the way I explained. Do you think the aileron on this wing adds lift? LOL

Bob
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Old 02-01-2013, 03:36 PM
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Default RE: Wing covering

Well I just learned something new and it makes sense. in a way. I always used an iron, tacked down the ribs and did most of my shrinking with an iron and pretty much only used the gun for open spaces that the iron couldn't reach . I would like to hear more as to why using my method is different and adds less torsional integrity. Of course I'm probably wrong, but I'm thinking that tacking down the perimeters and not distributing the load , you would be using less of a "point to point" contact area increasing more wing warpage as in increasing the bending moment created. Sort of like torquing down the head bolts of a cars engine head.
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Old 02-01-2013, 04:51 PM
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Default RE: Wing covering

I tack the perimeter first pulling everything as tight as I possibly can, I mean really tight then I iron and heat gun whats left with the exception of any rib area, I do this so the covering can move and slide as a whole during the super heating process, otherwise areas between the ribs can be too loose and other areas too tight. now that everything is tight, I heat the covering over the ribs and lock everything down. I learned to do this on the smaller stuff and carried over onto the big stuff. When I cover with plastic film, I use MonoKote and as most of you know, it is very difficult to cover with these days, but I use it anyway because with my methods of covering I can still make it look like paint and I do like that.

Bob
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Old 02-01-2013, 05:03 PM
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Default RE: Wing covering


Quote:
ORIGINAL: sensei

I generally iron the perimeter tight, then come back and heat gun or iron the center area tight, and last, I iron all the ribs for the very reason John stated, torsional strength. I do this very same thing on small trainer type wings or my giant scale wings, too me it is just a good way to go. Here is my wife holding the stab and wing half for my 55% Extra 260 and both are covered the way I explained. Do you think the aileron on this wing adds lift? LOL

Bob
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Old 02-01-2013, 05:04 PM
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Default RE: Wing covering

Gary you completely misconstrued both of my posts without really reading them, the question was by the OP in this trainer forum thread is it OK to cover only the parimeter of his wing without out sealing the ribs.

The implication was being made by responders that it did not really matter. Well My response could only be it is dangerous to cover a trainer wing (remember this is after all the trainer forum) 'Without' sealing the ribs and I will stand by that agine and agine.

Gary take a Senior Kadet wing that is kit built and has only been parimeter sealed compare it directly with the exact same wing that has been covered and all surfaces sealed then the unsealed rib version and the lack of stiffness will be shocking and yes I have done exactly this many times as well as seen this result many times expecially by the fellows who refuse to seal the ribs.

Like I Have said I am not any kind of an expert nor have I ever been but what I am is a survivor. So I will not argue about basic cellular structures but willing Jack Northrup would have back in the thirtys with his Alpha and Gamma monoplane wings which became the basis for his multispar cellular wings for the DC-1,2 and 3 wings as well as just about everything since.



John
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Old 02-01-2013, 05:30 PM
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.
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Old 02-01-2013, 05:33 PM
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Default RE: Wing covering

Didn't mean to start a todo just wanted inside.  Seems to me that the process should go...1.perimeter, 2. heat gun the center, 3.  seal the covering to the ribs.  The last step locks everything in place.  Not sure but gaining insight.  Would be nice to run into an oak tree and knock it over rather than have to climb the tree.  Sensi, I think you have enough lift with the ailrons to get the dining room table aloft.
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Old 02-01-2013, 06:00 PM
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Default RE: Wing covering

Not trying to disagree with anyone or stir the pot, I would like to learn more. I would still like to see proof on the torsional moment theory.
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Old 02-01-2013, 06:11 PM
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Default RE: Wing covering


Quote:
ORIGINAL: 33willys

Didn't mean to start a todo just wanted inside. Seems to me that the process should go...1.perimeter, 2. heat gun the center, 3. seal the covering to the ribs. The last step locks everything in place. Not sure but gaining insight. Would be nice to run into an oak tree and knock it over rather than have to climb the tree. Sensi, I think you have enough lift with the ailrons to get the dining room table aloft.
OK, now you made me spit my soda out my mouth and nose... 1,2,3, and 4. I been doing it that way since MonoKote came out. Maybe it's not for everyone, but it sure works for me.

Bob
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Old 02-01-2013, 06:23 PM
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Default RE: Wing covering

Quote:
ORIGINAL: GaryHarris

Not trying to disagree with anyone or stir the pot, I would like to learn more. I would still like to see proof on the torsional moment theory.

If I understand your question on the proof you seek, I think you may be able to prove this theory to yourself very easy by taking an uncovered open bay wing panel with a relatively small D section and performing a torsional twist test, you will find that it will twist very easily. Now cover both sides that same wing panel and try and torsionally twist it, you will see and feel the difference like night and day.

Bob
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Old 02-01-2013, 06:35 PM
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Default RE: Wing covering

Nice!! I like the plane too.
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Old 02-01-2013, 06:48 PM
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Default RE: Wing covering


Quote:
ORIGINAL: sensei

Quote:
ORIGINAL: GaryHarris

Not trying to disagree with anyone or stir the pot, I would like to learn more. I would still like to see proof on the torsional moment theory.

If I understand your question on the proof you seek, I think you may be able to prove this theory to yourself very easy by taking an uncovered open bay wing panel with a relatively small D section and performing a torsional twist test, you will find that it will twist very easily. Now cover both sides that same wing panel and try and torsionally twist it, you will see and feel the difference like night and day.

Bob

Bob. That's before covering. It's late and Ill be back tomorrow.
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Old 02-01-2013, 06:57 PM
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Quote:
ORIGINAL: oliveDrab

Nice!! I like the plane too.
I showed my wife your post and it made her evening...
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Old 02-01-2013, 10:48 PM
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Quote:
ORIGINAL: GaryHarris

Well I just learned something new and it makes sense. in a way. I always used an iron, tacked down the ribs and did most of my shrinking with an iron and pretty much only used the gun for open spaces that the iron couldn't reach . I would like to hear more as to why using my method is different and adds less torsional integrity. Of course I'm probably wrong, but I'm thinking that tacking down the perimeters and not distributing the load , you would be using less of a "point to point" contact area increasing more wing warpage as in increasing the bending moment created. Sort of like torquing down the head bolts of a cars engine head.
I don't see much of a problem with your technique Gary, if I understood it right. Do you or do you not make sure that iron on covering is firmly attached to the ribs? If yes, it's as strong and rigid as it's gonna get.

Iron on coverings are often polyesters (Mylar is one type). They are usually tensilized which means they are oriented or stretched to add strength and stiffness and also allow them to shrink back when reheated.

Stiffness is a property of any material; it governs things like torsional rigidity. It's a measure of how far some thickness-width-length of something will deflect under a load applied at some distance away (a moment arm). It's an "intrinsic" property. That basically means that stiffness is the same regardless of whether the material is 1" long of 10" long....The 1" long piece takes more force to move than the 10" piece, true enough, but when you normalize for the moment arm, the stiffness is constant

A wing that has closely spaced ribs that has full and good contact with the covering, will have greater torsional strength than one with ribs wider. If the covering is not adhered, then it's like having a long piece of covering...ie- it takes less force to move it. It is really that simple.

Similarly, a surface that has fully adhered covering will be stiffer and stronger in torsion than one where only the perimeter was adhered. The point folks may be missing is that coverings provide the best stiffness and torsional rigidity when fully adhered to a solid surface because they are not allowed to move independently of that surface- ie- there isminimal moment arm

Apologies in advance for the Physics lesson and hopefully it makes sense to you folks
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Old 02-02-2013, 06:34 AM
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Default RE: Wing covering

Matt,

A bit technical for the beginners forum but all true. Lets not forget to mention that more ribs = more weight and solid surfaces = allot more weight so lets not go off the deep end with structure avoiding twist. In simple view, just give your wing a little twist both without covering and with, you will see the lite...

Bob
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Old 02-02-2013, 07:52 AM
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Default RE: Wing covering

Quote:
ORIGINAL: sensei


Quote:
ORIGINAL: oliveDrab

Nice!! I like the plane too.
I showed my wife your post and it made her evening...
You're a lucky man!
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Old 02-02-2013, 08:36 AM
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Default RE: Wing covering


Quote:
ORIGINAL: 33willys

Didn't mean to start a todo just wanted inside. Seems to me that the process should go...1.perimeter, 2. heat gun the center, 3. seal the covering to the ribs. The last step locks everything in place. Not sure but gaining insight. Would be nice to run into an oak tree and knock it over rather than have to climb the tree. Sensi, I think you have enough lift with the ailrons to get the dining room table aloft.

Excellent 33Willys your process will work fine and of course the important one is your number three. A heat gun can be used in the center but to assure the ribs are sealed simply run your hand along each rib with it in a sock and apply a slight pressure downwards not sliding it along as you move the heat gun. If you can see the rib (the seal line) visually then you know that it is sealed.

John
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Old 02-02-2013, 10:22 AM
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Default RE: Wing covering

Good advice, results seem to work out for the best!
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Old 02-02-2013, 11:36 AM
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Default RE: Wing covering


Quote:
ORIGINAL: JohnBuckner


Quote:
ORIGINAL: 33willys

Didn't mean to start a todo just wanted inside. Seems to me that the process should go...1.perimeter, 2. heat gun the center, 3. seal the covering to the ribs. The last step locks everything in place. Not sure but gaining insight. Would be nice to run into an oak tree and knock it over rather than have to climb the tree. Sensi, I think you have enough lift with the ailrons to get the dining room table aloft.

Excellent 33Willys your process will work fine and of course the important one is your number three. A heat gun can be used in the center but to assure the ribs are sealed simply run your hand along each rib with it in a sock and apply a slight pressure downwards not sliding it along as you move the heat gun. If you can see the rib (the seal line) visually then you know that it is sealed.

John
I have a sock I use as john mentioned and use it as I'm shrinking with the heat gun, it works very well. I never run the iron over the ribs or cap strips. I won't get into the structure thing but by using the sock the hot covering does stick to the ribs but you don't get that nasty looking glued down look, it's very smooth. I try to only use Ultra but I still often use the Mono and do the same thing with the sock. Most the time Ultra will shrink tighter but both coverings seem to work the same way when using the sock.
Right now I'm working with Microlite film for the first time. So far I really don't like it, sort of like working with cling wrap that likes to stick to itself. I found the correct heat for it with the iron and I'm learning to work with it. I have also created new words to swear at it!! There is a learning curve to everything and this is my time!
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