Droopy

I'm a fairly experienced builder, but recently decided to try to build a plane w/o CA and using magnets/weights. This will be my 3rd Goldberg Chipmunk. I'm sheeting the leading edge of the wing and am looking for some tips on how to get the very front part of the sheeting to stay bent on the ribs as the wood glue dries. I've soaked the balsa and let it sit with some weights on it for a couple days, but the last 1/4 inch or so still doesn't want to bend far enough near the wingtip.

Ideas?

Thanks,

John

tailskid

My Feedback: (34)

I use masking tape to hold it in place. You might want to try putting some slow (thick) CA on the leading edge and regular glue on the ribs. Then spray some kicker along the leading edge of the sheeting. Work from the center of the wing out/in and you shouldn't have any problems. And yes, make sure the leading edge of the sheeting is damp!

Jerry

J_R

When you wet it try Windex or ammonia mixed in water. The ammonia changes the wood at the cellular level and will bend much further and easier than just water alone.

CafeenMan

Droopy - Here's what to do...

First, glue the sheeting on to the spar and pin it down securely. Let it dry. That will make the rest really easy. This wing has a sub-leading edge, correct? Allow the sheeting to overhang the leading edge by about 1/2" if possible. Pin clamps are awesome, btw. Made by Rocket City.



Once the glue is dry, try to curve it over the ribs and sub-leading edge. If you think you can do it without cracking it, then it isn't necessary to wet it. If not, then do as J_R says - use water/ammonia mix and spray it on. Give it about 5-10 minutes to work.

Get a syringe and fill it with glue. Put glue on all the ribs and the sub leading edge. Have plenty of pins handy. Starting at the center of the panel, work the sheeting down to the midpoint of the rib between the spar and the sub-leading edge. Pin it and work your way out to both ends. While you're doing this, push the sheeting forward with your palms. If you don't do this and pin to the leading edge, then it probably won't stay down on the ribs.

Now put pins through the sheeting overhanging the leading at an angle so they go into the sub leading edge.

Another way is to put plastic wrap over the sheeting and stack magazines on top, but this has been hit and miss with me, so I usually don't mess with it. If it works, it's a lot faster though.

BTW... the pins that look like they're holding the sheeting to the spar aren't. They are holding the front of the cap strips. The sheeting glued to the spar was dry before I glued the forward portion of the sheeting down. Helps prevent the sheeting from being wavy along the span, although it is possible to glue the whole affair on in one shot.

WILDCRASHWILLY

I super sheet, it is much stronger and easier to work with. I read an article somewhere "don't remember where" a year and a half ago and have since done all my sheeting that way. 1st coat the edge of the ribs with elmers wood glue or tite bond and also where the ribs and leading edge will make contact on the sheeting. 2nd, take your finger and smear the glue thin, "(some use rubber gloves here but the glue does'nt bother me I just wash my hands)". IMPORTANT! let the glue dry for 30 to 45 minutes! 3rd, After glue has dried, take a covering iron or a small iron set on wool and begin to iron the wood down from the leading edge to the rear, the wood must get hot to the touch, don't burn the wood! Hint! I sand an angle on the front edge of the 1st sheet before smearing the glue to contact the leading edge for a good contact in that area. Also for me personally I sometimes don't glue the leading edge with the elmers wood glue, but glue the ribs and bottom of sheet as stated but prior to using heat I use thin CA to stick the edge of the 1st sheet to the LE. After ironing the sheeting to the ribs, it will be extremely strong and cannot be taken apart without breaking wing.

Once you do one or two you won't try any other way.

WILDCRASHWILLY

Please note, aftre ironing. let wing cool for about five minutes, the glue has polermarized and is completly set. You can begin sanding or what ever you want to do next in your building process. If I can find the artical I read I'll post the source here in a few days.

hookedonrc

Here's a technique that I have used. I glue the sheeting to the spar and let it dry. To wrap the sheeting across the ribs to the LE spar, I place a weight along the spar on top of a towel. I keep the towel folded back to the trailing edge, put thick CA on the edge of the ribs, then spray the sheeting with windex. When it is flexible, I pull the towel over the sheeting leaving it hanging over the LE. Then I attach weight all along the hanging towel to pull the sheeting down smooth across the LE. So far, I have built a trainer wing, and an SE wing doing this. It avoids using a lot of pins and keeps the pressure even across the length of the LE. I let the towel hang with the weight on it till all is dry then remove it and finish up the LE. Now I don't know how this will work for others, but it worked for me. For the weight, I attach severl "C" clamps along the hanging edge for the weight. Weird, but I made it work.

r1morris

My Feedback: (1)

Here is the method I have used for over 20 yrs I posted it some time ago on RCU.
I now use the same method in making very lite and strong wings for my electrics. Saves time and all the pins and clamps. the thinner the wood the more practice it takes. For most building use the method as described below.

Here is a trick I have used with common wood glue for years in sheeting a D tube wing. This works well with either 1/16 or 3/32 sheeting. Precut the balsa sheeting for a nice close fit. Next lay a small bead or glue everywhere the sheeting will meet the structure. I use a bead of glue about 1/16 wide. Now take the balsa sheet and starting at the leading edge press the balsa sheet down to meet all areas you have put a bead of glue on. You want the glue to spread a bit . Now take the sheet off and turn it over glue side up. Use a finger to rub any large drops of glue into the balsa on both the wing structure and the balsa sheet. Now let the glue set up for about 15 to 20 min depending on heat and humidity. This step is not critical you just want the glue to be damp not dry to the touch.
Some times a balsa sheet is a bit stiff so before going to the next step I lightly spray the sheet with Windex. Do not soak it just a lite coat will do.
Turn you covering iron onto the hottest setting and now the easy part comes starting from the leading edge apply heat to all the areas where you put the glue, that include all the ribs .Work with steady pressure and heat the balsa will stick together. You get one shot at this just take your time and you’ll never go back to pins or the other methods again. I do the top first then the bottom of the wing after . The nice part is everything cleans up with water.
Try it on your next D-tube wing you’ll like it

hookedonrc

I do have a question, am I adding my sheeting backwards? I see a lot of responses that start at the LE should I reverse my process to start at the LE as well? I've only worked on a wing twice, one on my SE Kit, and the other repairing my Avistar.

wrongwaywayne

I agree with the white glue method. You have to put glue on both parts being glued. I first read about it in Model Airplanes book on Building Techniques - Good book. I use Sandable Aliphatic glue made by Pica Products. It doesnt leave hard spots that can be troublesome when sanding. I also use the wifes clothes iron instead of my covering iron. The extra weight of the iron helps and it is easier to hold on to.

Rodney

Use alphatic resins (not white glue) for this process. Now there may be some white alphatic resin glue and that would be okay to use.

CafeenMan

WILDCRASHWILLY - I don't like the idea of heating up glue like that. It's probably working fine for you or you wouldn't suggest it, but not being a chemist, I wonder what this technique does to the glue's chemical structure. I would worry that the bond would begin to deteriorate and possibly crumble after a couple seasons. I'm not willing to risk my plane to save a few minutes.

hookedonrc - [sm=thumbup.gif] This is a technique that has never occurred to me. I think I'll use it next time, but I'm going to modify your technique a bit. First, I'll use magnets, weight or clamps to secure the cloth behind the wing. Then I'll roll a piece of conduit in the cloth over-hanging the front of the wing. I think that will provide more even pressure than using weight in a few spots. Thanks for the idea.

voyager_663rd

why not just make a cloth "tube" (fold over and sew the edge) and stick a metal tube (cast iron water pipe?) lengthwise for le and te and then attach your weights so it's evenly weighted le and te?

CafeenMan

voyager - that's pretty much what I'm talking about, but if there is a heavy tube in the cloth, why would you need more weight?

hookedonrc

Now that is something I didn't think of. Let me know how it works and if it proves to be a good idea, let me know. I can change my technique to match.

Back at ya for the idea: Thanks

Balsa Master

yay, get to use paint again

WILDCRASHWILLY

Cafeenman;
I found the source I used to learn super sheeting, I think someone else listed it here also, but the name of the book is, "RC AIRPLANE BUILDING TECHNIQUES" by Model Airplane News. It can be ordered from RCSTORE.COM and is worth the $18 it cost. I have built several wings using this method and am amazed at hot strong they are. In fact I super sheeted one for a Hots last night and 5 minutes after it was completed I picked it up and tried a twist test on it. No flexing detected. However there are many ways to sheet your wings that work well, I just happen to like that article because of the ease of sheeting plus the strength it seems to impart on the structure. I've also used it on a fuse as well with equally satisfying results. I used my covering iron lastnight set on about or slightly above 4 on the setting, however not all irons will have the same indicator on the dial. I highly recommend the book, you won't be sorry. You can see a pic of the book in the back of a Model Airplane news mag.

ilikeplanes

I use yellow wood glue for big wings and CA for smaller ones. I always start by fitting the sheeting to the leading edge with a continuous masking tape hinge. That ensures the sheeting stays tight in the most difficult area. Then I simply apply glue to all the wood to be joined, flip the sheeting back on its tape hinge and pile all my old MA magazines on top. Magazines are my weight of choice because they conform to the wing with just the right amount of flexibility. If you really go nuts, you can put bricks or paint cans on top of the magazines. I've never had to soften or mold the wood to take the curve.

One benefit to using a slow drying glue is avoiding warps. With CA, there is really no time to let things settle down and flatten. It has to be right on the very first second. Wood glue allows you to fuss the weight until everything is just right.