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Author Topic: Fully Sheeted Wings  (Read 2808 times)

Online Ken Culbertson

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Fully Sheeted Wings
« on: May 22, 2018, 08:05:36 AM »
Is there a reason you see so few fully sheeted wings now days?  (Foam excluded) 
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Offline Avaiojet

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Re: Fully Sheeted Wings
« Reply #1 on: May 22, 2018, 11:00:29 AM »
There are plenty of sheeted wings around.

Tom Morris builds and sells a good deal of them.

You might want to talk to Tom.

CB



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Offline Will Hinton

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Re: Fully Sheeted Wings
« Reply #2 on: May 22, 2018, 11:10:17 AM »
Weight.
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Online Brett Buck

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Re: Fully Sheeted Wings
« Reply #3 on: May 22, 2018, 12:57:29 PM »
Is there a reason you see so few fully sheeted wings now days?  (Foam excluded)

   If you are going to fully sheet a wing, you might as well do it with foam core, much more likely to come out straight and no net weight penalty. I would also contend that there is no net weight penalty for using foam VS built-up, once you beef up the built-up structure to be as stiff, and put the finish on. We have some examples of that around here. Built-up only seems lighter before you finish it (assuming a competition quality finish), which is swell if you like bragging about component weights, but ultimately makes no difference in the end product.

    Brett

Online Ken Culbertson

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Re: Fully Sheeted Wings
« Reply #4 on: May 22, 2018, 01:35:43 PM »
   If you are going to fully sheet a wing, you might as well do it with foam core, much more likely to come out straight and no net weight penalty. I would also contend that there is no net weight penalty for using foam VS built-up, once you beef up the built-up structure to be as stiff, and put the finish on. We have some examples of that around here. Built-up only seems lighter before you finish it (assuming a competition quality finish), which is swell if you like bragging about component weights, but ultimately makes no difference in the end product.

    Brett

Thanks.  I always sheeted my wings but when I came back in, everything seemed to be open.  I was concerned that there may be some good reason.   I really enjoy building but I am quite crappy at finishing so I will probably stick with ribs. Crappy looks better on a sheeted wing!
I have used foam on sailplanes and didn't really like it. 

Ken
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Offline Trostle

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Re: Fully Sheeted Wings
« Reply #5 on: May 22, 2018, 01:41:43 PM »
Bob Gialdini explained in his 1963 American Modeler Annual article on his Nats winning Olympic that he went to "fully planked wings, since proper wood didn't weigh any more than a fabric covering."  Sort of supports Brett's argument.

Keith

Online Brett Buck

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Re: Fully Sheeted Wings
« Reply #6 on: May 22, 2018, 09:23:13 PM »
Bob Gialdini explained in his 1963 American Modeler Annual article on his Nats winning Olympic that he went to "fully planked wings, since proper wood didn't weigh any more than a fabric covering."  Sort of supports Brett's argument.

   David's first two Star Gazer/Trivial Pursuits both weigh the same, one was built-up/open bay and the other was foam, both with similar translucent finishes. Ted's Trivial  weighed almost the same to start with, too, one foam, one built-up/open bay.

     Brett

Offline Mike Griffin

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Re: Fully Sheeted Wings
« Reply #7 on: May 24, 2018, 09:08:48 PM »
Tom Morris has built and sold many fully sheeted built up Millennium wings. 

Mike

Online Dave_Trible

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Re: Fully Sheeted Wings
« Reply #8 on: May 29, 2018, 06:27:39 PM »
I think I will be doing more fully sheeted wings-mostly because good quality silkspan is history.  I just silked one which is my other alternative but I'm sure I didn't save any weight vs. full sheeting. I still do hand-rubbed dope finishes so most other coverings don't seem too practical.

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Online Brett Buck

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Re: Fully Sheeted Wings
« Reply #9 on: May 29, 2018, 07:12:49 PM »
I think I will be doing more fully sheeted wings-mostly because good quality silkspan is history.  I just silked one which is my other alternative but I'm sure I didn't save any weight vs. full sheeting. I still do hand-rubbed dope finishes so most other coverings don't seem too practical.

  Get rid of that dope and switch to epoxy/car clear and you will save about 2-3 ounces and it will be much more durable.

    Brett

Online Dave_Trible

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Re: Fully Sheeted Wings
« Reply #10 on: May 30, 2018, 05:20:33 PM »
I may be more likely to do that without open bay covering.  I always  needed a way to easily patch holes or other damage.  The dope makes that pretty easy-  says this old dog shy of new tricks...

Dave
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Online Brett Buck

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Re: Fully Sheeted Wings
« Reply #11 on: May 30, 2018, 10:29:46 PM »
I may be more likely to do that without open bay covering.  I always  needed a way to easily patch holes or other damage.  The dope makes that pretty easy-  says this old dog shy of new tricks...

  As long as you are talking sheeted surfaces (foam or built-up), I think epoxy is much easier, because you don't need to worry about adhesion or incompatible chemicals. It's glue with pigment, it sticks to anything and itself just fine.

     My airplanes have *many* repairs, some pretty drastic, and I routinely get 17-18 points. And the only thing wrong with the finish is the fact that it is clear nitrate dope underneath, and *that* has gotten fuel in it and self destructed underneath the otherwise intact epoxy paint.
 
       Brett

Offline Dennis Adamisin

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Re: Fully Sheeted Wings
« Reply #12 on: May 31, 2018, 07:09:35 AM »
Is there a reason you see so few fully sheeted wings now days?  (Foam excluded)

I think the problem is simply availability of decent wood.  I used to build fully sheet wings, both built-up & foamies.  Ease of build, ease of finish, stiffness, strength and durability were all key attributes.  When I came back (after a 25 year lay-off) I discovered that good wood was essentially non-existent.

Balsa ranges from 4 lb to 28 lb (!!!) density.  With that kind of variation wood selection is paramount. Way back when we used to go Hobby shop to shop picking through the 1/16" sheeting, weighing every piece we bought.  Usually could find what we needed within a couple visits.  Contrast to the present, I went to my local shop to buy a piece of 1/16" sheet - would have settled for almost anything because it was not going into a weight sensitive part.  After TWO shops I went home empty handed, they did not even have a single piece in stock.

So what is PLAN B? A couple years ago my brother ordered a stack of sheeting from one of the big suppliers, specifying weight per their standards.  Out of some 20 sheets he got exactly 1 piece that he could use. There is a happy ending - he ended up placing another order, this time to Tom Morris and he got GREAT wood. (I think he used the first order to build a set of car ramps...)

Frustration was enough to drive me to I-Beams!  An I-Beam can build fairly light but that is deceptive - it is difficult to FINISH well, with durability, and to finish light.  For this reason all my I-Beams have been monocoated; both to deal with the finishing & durabiity issues and to control weight gain.  I do not think I would ever do an I-beam with tissue - not worth the grief, and I offer my appreciation to any/all who successfully use tissue.  Also with an I-beam you accept some risks - like flexibility - versus D-tube or foamies.

To Brett's point about finish durability: some of the best finished models are pylon racers, where the balsa sheet wings are typically covered in 1/2 oz cloth and epoxy resin, and finished with epoxy paint - eliminating the nitrate layer.  Obviously technique is a big factor in the final weight but it can be done within reasonable weights and is absolutely bullet proof.  Would probably work well using tissue (NOT CF veil) to control weight.  If you fly a lot and/or plan to fly the same bird over multiple seasons this would be the way to go...
Denny Adamisin
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Offline MikeyPratt

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Re: Fully Sheeted Wings
« Reply #13 on: May 31, 2018, 01:05:25 PM »
  As long as you are talking sheeted surfaces (foam or built-up), I think epoxy is much easier, because you don't need to worry about adhesion or incompatible chemicals. It's glue with pigment, it sticks to anything and itself just fine.

     My airplanes have *many* repairs, some pretty drastic, and I routinely get 17-18 points. And the only thing wrong with the finish is the fact that it is clear nitrate dope underneath, and *that* has gotten fuel in it and self destructed underneath the otherwise intact epoxy paint.
 
       Brett

I happen to go along with Brett, they are about the same when finished.  However, it’s the same old problem finding suitable wood is the key.  For that reason alone is why most are now open bay assembly’s.  There are other things that can be used to get fantastic finishes such as, glasscloth, CF vail, tissue and iron on film.  The attached photos are the stab & elevators of my latest design P-Force XL.  They are covered with Sig Plyspan tissue and then covered with SLC covering and turned out really good.  Process is as follows!

(1)  Lightly sand parts with different grit sandpaper from 220 to 400 grit sandpaper.

(2)  Give parts one coat of nitrate dope thinned 70% thinner, and 30% dope and allow to dry at least 12 hours.  When dry, lightly sand with 400 grit sandpaper and remove the dust with a tack-cloth.  The only reason for the thin coat of dope was to insure that the parts would not warp when the wet tissue was applied to the structure.

(3)  I want to try a new product to attach the plyspan instead of the old dope method.  The Deluxe Eze-Drop worked as intended.  I did find the Eza-Kote finishing resin worked better than the Eze-Dope to attach the plyspan to the stab & elevators.  Apply a light coat of the Eze-Kote to the out side edge’s of the stab. Wet the plyspan with water by passing it under a facet and ringing out the excess water by crumpling the plyspan in your hand and squeezing the plyspan covering (Do not coat the entire stabilizer with Eze-Kore)   Place the plyspan on the part and remove as many wrinkles as possible.  Apply an additional coat of Eze-Kote to the out side edge of the plyspan tissue using a 3/8” paint brush and allow to dry. When dry then trim off the excess covering with an #11 Exato or razor blade.  Follow the above to cover other the side.  When the covering and Eze-Kote are dry, lightly sand the edges with 220 grit sandpaper.

(4)  cut a piece of SLC covering oversized giving you at least 2” of extra in each direction.  Place you Sealing Iron on 200 degrees (about 2 on the iron).  The film has two sides, one very smooth, second side has a slight rubber feel, which is the glue side to go aginset the tissue.  Place a piece of SCL on the part and iron in place starting in the center and working your way to the ends pushing the air bubbles out from under the SCL covering as you go.
As you approach the leading and trailing edge, roll the iron over and around the leading & trailing edges
attaching the film to the edges.  Replete the above to cover the remaining side.  Turn the heat up to 250 to 275 degrees, and carefully seal down the edges of the film.   Note; Overlap the covering at least 1/4” on small parts and 1/2 to 3/4 for larger parts.

Mikey


« Last Edit: May 31, 2018, 01:32:19 PM by MikeyPratt »

Offline Alexey Gorbunov

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Re: Fully Sheeted Wings
« Reply #14 on: May 31, 2018, 01:52:18 PM »
I use PU glue to glue the plating sheets. But the glue is thick and I dilute it with acetone to a state like liquor. If you think that acetone will damage the foam core, then you are mistaken. The glue layer turns out to be so thin that acetone has time to evaporate, until the gluing is pasted to the core. The main thing is to use a long lasting PU glue.
To compress the skin i use a foam craddles in a vacuum bag.


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