Someone mentioned warped wing
 

When I unpinned one of my wings from my plan I sat it aside and started the other wing.. I then came back to the 1st wing a few days later and I eyed down it long ways. It seemed to have developed somewhat of a warp to it. I repinned it and weighted both ends then misted it with water.. I then let it dry overnite and repeated the misting again yesterday.. I allowed it to dry and checked today.. Almost completly straight, but may still have a hint of a curve.. What can I do here? I read in another thread about using a heat gun to heat and bend it back.. Any other thoughts on this?

How much is too much of a warp to still fly straight?
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RE: Someone mentioned warped wing
 

Your weight and water is good, just shim it so it goes beyond straight, it will spring back slightly when you remove it after it dries. I somehow got a 1/4" twist in an uproar wing, I wet it down with glass plus and clamped it to the table. I put an 1/8" scrap piece of lite ply as a shim, it dried perfectly straight. You will get it.<div>Ed</div>

RE: Someone mentioned warped wing
 

Thanks for the info Ed.. I'll shim it tonight and mist.. Thank You

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RE: Someone mentioned warped wing
 

Give up trying to get it straight with moisture. I don't use wood glue like titebond because it contains water and water and balsa don't mix. I always get warps if I use wood glue, it's why I still put up with CA. Just today I was making a long hatch out of 1/4 inch balsa. It needs to be plained and sanded to shape so I had to use wood glue. It warped!
When it's time to cover you use the covering to remove warps out of wings and surfaces. When you get there several of us will help you out. It's just twisting the surface and shrinking the covering on the opposite side of the covering to remove the warp. Using water usually just makes things worse. The balsa will also warp toward the side of the wood you have wet. If you have a wing warp going toward the top of the wing you moisten the bottom of the wing. It's just easier to do with the covering.;)

RE: Someone mentioned warped wing
 

+1 and very true words. I so hate it when I have to agree with just about everything you say :D

Karol

RE: Someone mentioned warped wing
 

Nailed it I say.

RE: Someone mentioned warped wing
 

I don't use wood glue like titebond because it contains water and water and balsa don't mix.

Sorry - I disagree. It isn't the moisture in wood glue that makes a warped anything (except, don't use it to laminate). Its the builder. I've been using "yellow glue" for well over 50 years and it is excellent. Use the CA and hope it doesn't make you sick!

All types of glue have their place - it is knowing where to use what.

RE: Someone mentioned warped wing
 

Warping which can result in unbalanced aerodynamic forces is usually associated with wings or tail surfaces.

First we have to work on REALLY flat surfaces and this working surface has to have been verified to be within very tight limits. I usetwo proven straight metal ruler 36 inches long to chek the working surface. First the metal rulers have themselves to be proven straight wihin 0.002 inches. This 0.002 inch is my established standard.

Placing the straight rulers on the working surface must jam a strip of tissue paper 0.002 inch think everywhere along its length and in all directions the rulers can be oriented. I then know that my working surface is flat enough to be useful.

Most of the time a warpedwing or stabilizer/elevator or fin/rudder is due to warped spars, leading edges or trailing edges material. These components can be verified as being straight by simply letting them sit on the known flat surface before pinning them down. This verification has to be in all orientations of the material.
If it appear to sit flat then turn it 90 degrees and check it is still flat. A circle or an arc can sit flat until it is turned 90 degrees.

I cannot remember ever having a warped wing or tail surface. Over the years I have used glues like Ambroid, Weldbond, Sig-Ment, Titebond and plain labellled "wood glue (exterior)". I cannot beleive that the glue is a cause of warping the built up structure since It never did in my builds.

Natural straightness of the components have to be verified before pinning them on the work surface. It just makes sense.

Warping of wood components can occur due to temperature and humidity. The wood components should adapt to their environment for a long enough period to stabilize. We cannot take balsa from the house at 68 deg F and 50% relative humidity and bring it to a garage workshop at 85 deg F and 90% humidity and glue the pieces. That is an invitation to warping.

It is then necessary to judge "how much warping is acceptable".
I figure that "none" is the answer. Fortunately we can compensate in flight by trimming.
Imagine for a moment that one wing has a twist resuling in a different incidence and we compensate with trim. That trim force (a torque) varies with speed and affects the stability.

Of course there is no concern if theflight is being controlled every second but even then flight maneuvers will appear to respond differently depending on the speed of the model.

This is not only "theory", it is observable behavior of the model to command control.
Take the means to avoid warps. the means to have symmetrical model geometry and the model wll be easier to fly and predictable in its respondse to command from the pilot.

Enjoy your flying. No doubt you are a better pilot than you may think. A warped model is more difficult to control; do not blame yourself as a pilot.

Cheers,

Zor

RE: Someone mentioned warped wing
 

Grey beard, yes straightening a fin- rudder, stab-elevator with covering is much easier. In my case with thevuproar. It is a one piece straight wing. It was better to get it straight before covering.
Just my thoughts

RE: Someone mentioned warped wing
 

Well, water will warp any wood product I've ever seen, unless it is perfectly sealed. It will even get to the almighty woodpecker meatloaf (MDF, chip board and particle board) given time. So my thinking is that any water based product will warp wood.

RE: Someone mentioned warped wing
 

If you're using moisture, use light wipes along the side of the framer/s which you want to expand. Too much will soak the entire spar and defeat the purpose. One nice thing about iron-on covering, is that after enough intentionally applied twist and heat reshrink cycles, you can usually get a warped wing to finally stabilize. Of course it requires some overshoot, and sometimes a number of tweaks done over the course of some time, to finally get it to stay where you want it.

RE: Someone mentioned warped wing
 

I checked it today and it looks a lot straighter than before. I probably could have taken the small warp out with the covering, like was mentioned earlier.. Although I have never Covered before either...http://www.rcuniverse.com/forum/js/f...eeth_smile.gif The warp was really very minor, I'd say a strong 1/8" . Which there again, I'm not sure if this is minor in the RC plane world? Anyways, I'm too much of an Perfectionist to leave it the way it was.. I'm a little more satisfied with it now. I'm Still going to leave it weighted and drying for a few more days, just to try to discourage the warp from reforming.

Thanks for the replies<br type="_moz" />

RE: Someone mentioned warped wing
 

Iron Bottom and all readers,

True that water (humidity) will warp any wood product if the humidity in the wood is not spread uniformly.

The work surface we use should not be subjected to wide variations of temperature and humidity.
One reason I domy building in my house that is constantly between 68 to 70 degrees fahrenheit and a relative humidity between 50% and 60%.

As mentioned in a previous posting I also have a method of checking how straight and flat is my work surface.
Now think for a moment "<u>how much water is in the glue used</u>".

We are buiding a wing structure. We have verified that our spar material and leading edge and trailing edge materials are straight and have no twist. They are receiving some glue at every ribs. How much water is in thatglue to migrate into the wood and cause it to twist or to curve ?

I do not know the composition of the different glues I have used over the years but asI wrote earlier I never had a twisted wing due to gluing. I suspect that most glue have very little water in their composition (formulation).

I may be correct and I may be in error but I suspect that many glue formulations contain alcohol or highly volatile solvents that evaporate during cure (solidification). A good glue has to have two main properties.
It has to have inherent strength once cured and it has to have binding to the parts it is joining.

We can tell how much solids result in a glue curing (polymerism or other process) when we fillet our gluing. We can see the amont of solids left forming the fillets.

Sig-Ment glue result in about twice as much solid left after cure as compared to Great Planes PRO and Titebond III wood glues. The solids left after cure have to fill the gaps between the parts in contact. Parts in contact are touching for only a very small percentage of their areas even with all the care we take to make good fits and even when pressure is applied to the joints being made.

Conclusions ___
Use a flat surface to work on and verify that it is flat.
Verify the individual components being assembled (glued) for proper shape.
Use good and proper glue for the specific assembly (fillet the joints).
Use a covering material that is light but strong in tension and does not tear easily.
In a woven fabric each thread has to break in tendion for the material to tear.
Seal the covering with coatings resisting variable weather exposures ( Think why full size fabric covered airplanes use aircraft dope).
Use coating material that is resistant to the exhaust of glow fuel if such is being used.

The above all makes good sense to me.

Enjoy solidly built models that will have minimum repair needed in the event of abnormal landings.

Zor

RE: Someone mentioned warped wing
 

You forgot one important observation> farting during the gluing process will result in a less than perfect joint, as the byproduct i.e. gas will affect the chemical/ mechanical bond that may or may not result in a crash causing bodily harm to others. So be careful. :eek:

RE: Someone mentioned warped wing
 

Remember eating white paste as a kid? It smelled good... wonder why it didn't taste good. Inquiring minds want to know!
Here's 108" span of glory assembled with wood glue. No warps, runs or cattywhompers! The third pic is an S-1 Ringmaster which is as straight as the theoretical line on a Cartesian Plane from point 'A' to point'B'. The fourth is another Ringmaster wing seen on edge. It's straight and I used yellow wood glue.

RE: Someone mentioned warped wing
 

There you see it. Pictures of well built wings and NO warp.

Success start in the brain.
I say that because the brain controls the steps taken toward success.

A reliable flat work table ___
Selection of straight materials ___
The glue of your choice.

You may not agree but gluing is an art and so is soldering.
It starts with theory which resides in the brain. That theory controls the steps taken in accomplishing any work process.

Some fellows do not believe in theories and it reflects in their achievements.

We read a lot about balancing our models longitudinally and laterally.
We read very little about a more important subject. That subject is geometrical accuracy of our builds.

Warps, non-symmetrical incidence, improper decalage, loose covering particularly on the wings changing the airfoil contour as the model is maneuvered, looseness of control surfaces (slop), all contribute to make a model more difficult to control (to fly).

I repeat what I wrote earlier. You are a better pilot than you may think if you fly a model that has good geometry. It is a lot easier to make it do what you wish compared to constantly have to feed radio commands because the model is unstable.

Fly the model ___do not let the model dictate your control inputs.

and have a great day at the flying field.

Come home with a big grin on your face and the results of a great flying day ___my wish for all of you.

Zor

RE: Someone mentioned warped wing
 

Too freaking funnyhttp://www.rcuniverse.com/forum/js/f...ey/msn/lol.gifWood glue warping; really? Whats next?

RE: Someone mentioned warped wing
 

If I wanted to build something straight, wood probably be the last thing I would consider. And balsa would be the last wood on the wood list. I build as straight as possible and certainly as straight as my tools allow.

For example; a wing.
1. Epoxy two 1/8" pieces of steel that are close to 1/2" wider and longer than the rib together.
2. Straighten and square one edge of the steel patterns.
3. Scribe a line through the center of the pattern.
4. Fix printout of rib to pattern.
5. Drill 1/4" holes to fit 1/4" drill rod that will be used for a jig.
6. Rough saw the shape of the rib. One side for symmetrical ribs. Pattern will be flipped for other side.
7. Sand to finish shape.
8. Square sanded edges.
9. Saw rib blanks.
10. Lay pattern over blank and cut holes for jig. I have a paper drill, but a home made brass tube drill is a little faster.
11. With pattern on rib blank, draw rib shape on rib blank.
12. Rough cut rib blank to shape with Exacto knife.
13. Mark pattern with Sharpie on sanding edge.
14. Assemble ribs blanks onto 1/4" brass tube and slide pattern on each side.
15. Rough sand down close to pattern.
16. With finer grit, sand to final shape.
17 Turn pattern over and sand other side of ribs.
18. Check ribs by comparing outside ribs. Turn one rib top to bottom and check again. Do this on jig. Ribs are correct when no differences can be felt or seen.
19. Put ribs with brass tubes into machine vice. brass tubes on the top of the jaws.
20. Align rib notches drawn onto printout with side of jaws. Saw to correct depth.
21. Move to next line and saw to correct depth.
22. Turn rib stack over and repeat 19, 20 and 21.
23. Clear rib notches of excess material and finish sand if required.

Crazy? Probably. But I'll put my ribs up against anybodies.

I've always thought thin epoxy would be the ideal glue. I might try some finishing epoxy from Bob Smith.

Try a pop corn diet starting a week before gluing. :D

RE: Someone mentioned warped wing
 

Iron Bottom

I can see where your nickname comes from http://www.rcuniverse.com/forum/js/f...unge_smile.gif

Pictures of your jig would be nice to see.

Do you manufacture a new jig for every wing you build ?

Zor

RE: Someone mentioned warped wing
 

I agree, being new to all this I got a little lost while reading through those steps...

RE: Someone mentioned warped wing
 

[/quote]

I got lost as well.
It appears a jig is being built in order to build a wing.

I would think a jig has to sit on a flat surface unless it is sufficiently so strong and rigid itself that it does not matter on what the jig is sitting.

Not able to clearly visualize all those steps I figured a picture is worth a thousand words and suggested some pictures.

Zor

RE: Someone mentioned warped wing
 

That's just building, shall we say, two steel wing ribs to be used for patterns for making balsa ribs. I sandwich the balsa rib blanks between the steel rib patterns and sand them down. The patterns and two lengths of drill rod are the jig. I have various lengths of plastic standoffs (2", 1",1/2" and 1/4") to space the ribs. This allows any combination of spacers to be used to correctly space the ribs. The standoffs are 1/4" ID and 5/8" OD. If you are building a wing with a 2" space between the ribs, slide a rib on the drill rods, then a 2" standoff on each drill rod, then a rib, then a 2" standoff on each drill rod until all the ribs are on the drill rod. On the outside of the first and last balsa ribs, I use a one inch standoff and a 1/4" steel collar, steel rib pattern, and another steel collar. Square up the steel pattern on one end of the wing. Get all the play out of the ribs, spacers and steel patterns on the other end of the wing and tighten the collars. The ribs will not move and are spaced correctly, square and vertical. The flat bottom of the rib pattern sits on a flat surface. This is the jig. Washout may be built in by shimming up the back of one of the steel rib patterns.

If you could see this, everything would be perfectly clear.

Zor, I have a Mac and don't have the high dollar photography software. I have never figured out how to size photos that are acceptable for most sites. I'll try a cell phone and see what happens.

RE: Someone mentioned warped wing
 

Iron Bottom,

No more need for pictures.

Your last posting is well worded and I have a clear pic of what you are doing.

Many thanks

Zor

RE: Someone mentioned warped wing
 

Hey Zor,

Aquestion re: my Sig 1/5 scale J-3 Cub, if you would be so kind.

I am in the process ofassembling the Cub'sfuselage and am concerned that I might have a very slight warp or twist in the body. I placed a straight edgeacross therear of the fuselage (where the horizontal stabilizer will attach) as well as one across the cabin where the wing will attach so I can eyeball the two straight edges from the rearand look for any misalignment. It definitly looks like the stabilizer, when attached, will be tilted to the right in reference to the wing. Now having said this, the fuselage has not been glued at this point, but is held together with clamps on the top and masking tape on the bottom. It might just be fine when everything is glued...but if not, I have a big problem since things can't be unglued. Any tips on ensuring that everything is totally square before taking that final glue step?? It is being built on a piece of glass.

Thanks in advance.

Robert

RE: Someone mentioned warped wing
 

Bill any time you spray water on balsa it loosens up the fiber, that is why it formes easier and while it also can help to straighten bowed parts drying is what causes that and it can and will do the same thing to the wing you set aside. Humidity and heat can warp most wood products including plywood, just put a piece on a table in the path of warm air and it will warp because it shrinks as it gets dryer on the exposed side versus more moisture on the other, same for your wing.

If you take your wing and put the crown side down with a 1/8" spacer in the center and properly supported to remove only the bow then enough weight on both ends of wing to force the ends down and let nature take it's course. Check it ever so often and as soon as it's straight put it some place and cover it up until your ready for it. Do that with all assembled assemblys and turn them over once in a while, keep them covered ( news paper works well ) and out of a warm air stream and avoid these problems