RCU Review: Wing Repair Article

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    Contributed by: Scott Stoecker | Published: September 2007 | Views: 43049 | email icon Email this Article | PDFpdf icon
    RCUniverse.com How-To: Wing Repair

    How-To Article by: Scott Stoecker (hogflyer) Email Me

    Since there are a lot of beginners who get ARF or RTF trainers and don't know what is on the inside of the wing, I've decided to show how I did a wing repair with both minor and major damage.

    I recently acquired a new, un-built Hangar 9 Alpha 60 RTF that is damaged. Supposedly it had crushed ribs in both wings, a hole in the sheeting on the top of the left wing, and a crack in the fuselage at the landing gear. For about ½ of what it would cost at a hobby shop I couldn't pass it up (it'll be used for an AMA intro plane and giving flight instruction).

    When I opened the box I saw a lot of wrinkles in the covering near the landing gear block. I checked the fuselage on the inside and couldn't find any damage. Feeling around on the outside it appeared to be solid as well. I tightened up the covering and installed the landing gear. After pulling and pushing any way I can I sure can't find any damage to the fuselage. So I installed the prop and empennage and set it aside.

    There are a lot of wrinkles in the covering on both wings. I started with the left wing tightening the covering on the top. I could feel all the ribs were broken at the center support, and decided to open it up from the bottom since its all red vs. the white with trim on the upper side. It'll also be easier to recover being flat. The pictures show what the left wing center section looked like out of the box.

    The covering was removed from the center section showing the extent of the damage. The root rib is plywood, which I'll call Rib #1 as is the 4th rib out? Rib #4. The forward half of Ribs #2 & #3 are crushed. The sheeting is crushed and split between ribs R1 and R4.

    I made a cardboard template from a cereal box to make replacement ribs for Ribs #2 & #3, and provide a guide to make braces for the middle of the remaining ribs. I removed only as much of the damaged sheeting as necessary. I cleaned up where the sheeting was, but left as much of the ribs as possible so I can sister a replacement rib to them? it'll be a lot easier than trying to splice a repair section of rib to them. The glue they use constructing these is a real pain to remove completely? it's somewhat soft and took quite a bit of sanding.

    Cereal boxes are great for making templates. The cardboard is easy to cut with a knife or scissors, yet stiff enough to make multiple tracings. Since I haven't opened up the right wing half yet and don't know what surprises await there, I want a template that will last through both halves.

    I cut the new ribs out of 3/32 sheet balsa and glued them to remains of Ribs #2 & #3. I used yellow glue to attach them making sure I had plenty of squeeze-out between the old and new ribs. After I took the pictures I did clean up the excess glue.

    After the ribs had dried a couple of hours I added some 3/16 X ¼ balsa to the spar and 3/32 sheet under the remaining factory sheet to support the new sheeting. The factory sheeting is most likely metric since 1/16 sheet was thinner and the 3/32 sheeting was thicker. I opted to go thicker and sand the sheeting down to smooth it in. After sheeting and sanding it down I didn't want to take a chance on sanding too much into the factory sheeting, so I used lightweight spackling to fill in any unevenness and finish the blending. That was sanded smooth after it dried and completed the repair to the center section damage.

    Next up was to fix the rest of the ribs and wing tip. For the wingtip I cut a small piece of 1/16 sheet to double over the damaged area and attached it using thick CA with a little accelerator. Since the tip rib was missing a good size chunk I cut a rib to replace it.

    I used the cardboard template to cut some vertical supports to fix the remainder of the ribs. With the grain of the ribs runs fore/aft providing good longitudinal support I decided to add the supports running vertical to aid in compression strength. I measured back from the spar for the correct location of the braces and then drew their location on each side of each rib. Thick CA and clamps where used until they cured.

    The right wing had similar damage to the ribs, but no center section or tip damage other than the tip rib its self.

    The clamps are shown on the right wing, and the left wing is shown finished and ready to be recovered. I'm estimating the total working time for the repair, assembling the fuselage and recovering the wing will be just over 2 hours. Between 2 rolls of Ultracote and the wood and glue I spent less than $30.00 and will have most of the rolls left over for future projects.

    Here's the finished, covered plane fully assembled ready for its first flight. From a few feet away you can't tell it has suffered from crushed wings with a hole in one wing. I refigured the total working time and I spent about 4 hours to both repair and assemble the plane.

    In summary, this is a very basic, straight forward repair. While some people may seem intimidated by cutting open a wing, especially on a new, unassembled plane, it's not difficult. Just think through the process and follow some basic steps:

    1. Look at the damage, and don't be afraid of the 4 P's - push, pull, poke and prod. You will be surprised at the damage that can be found with your fingers.
    2. After you have determined the extent of the damage, remove the covering as required, and start assessing the damage to determine how you need to remove the damaged areas. This is where you want to give the structure a very good visual inspection.
    3. Don't be afraid to cut into the structure. There isn't a part on a plane that a modeler can't fabricate and use to replace a factory made part. Make sure you take your time cutting away the damaged pieces that need to be removed. Some can be left in place and fixed with a doubler attached to them.
    4. Decide what parts need to be replaced, make templates and fabricate new parts. Test fit the parts as you go along making adjustments as required. If a part doesn't look or fit right, then cut another one. Balsa is cheaper than a complete flying plane.
    5. Take your time replacing the parts making sure you have good glue joints and everything fits correctly. Pay attention to the surrounding structure so you put everything back straight. After it's all back together, reapply the covering, and check the balance to make sure nothing has changed.
    6. Take it out and fly! When you get to the field, give the plane a thorough inspection. If you have any doubts, have another club member check it over. Then double check everything to make sure you didn't forget to hook anything up or hooked something up backwards. For the first flight, depending on the type and location of the repair, treat it as the first flight the plane has made.

    The most important thing to remember is to take your time and seek help or ask questions if there is something you don't understand how to do.

    Good luck!

    Comments on RCU Review: Wing Repair Article

    Posted by: bucksnortly on 04/24/2008
    Very well done -
    Page: 1

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