It's pretty amazing how resilient the Gremlin design is. Many times you'll see one cartwheel across the field on a bad landing or flameout on launch or sometimes due to a bit of negative altitude while hotdogging. Sometimes the "snowstorm" of the moment can look fatal. Most times it isn't and many things can even be repaired at the field. This page is dedicated to those bags of bits you bring home after a particularly bad day. Once you've put it aside and gotten over the bad session, read on. After all, what have you got to lose since you've already written it off?
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This is probably the simplest of repairs. When this happens at the field in the middle of the contest, just put some tape over the hole and get back out there. Once you get home, take the tape off and check out the hole. Make sure there isn't some other more serious damage to the wing. If what you've got is a void in the wing, remember, the foam is not truely structural, it's just there to make the airfoil shape. Plenty of planes have big holes between the ribs. Personally, I like to square up the hole and then take a piece of foam (this is a great use of the foam core beds that hold the wings in the kit) and jam it in with a little Titebond or other white glue. Make sure the ends stick out beyond the wing surface on both sides and let the glue dry. Once you're glue is dry, take a rasp or rough sandpaper block and shape the foam to match the surrounding wing shape. Finally take some Model Magic or Red Devil Spackle and paint the area to fill in the minor voids. Once this is done, recover the section (if you bother) and give it a try. Make sure the fiber-reinforced packing tape is still in place and complete as listed in the flexing section below.
Sometimes a little preventative repair can save a wing before it fails totally. After a season or even a bad couple of sessions involving cartwheels, wings can start to show wear and get flexible. This is usually seen as a flexing at the ends of the spars. One other area that can really cause flexing is damage to the fiber reinforcing tape around the wing. As stated in the instructions, foam breaks by pulling apart. The fiber tape is there to prevent this and cause the opposite side to compress. Foam is very good at rebounding from compression. If the tape is weakened or cut, repair it as soon as possible before a flex causes panel failure. This can generally be done by sticking a piece of tape over the old one across the damaged section and overlapping the ends by a few inches.
Another common form of weakness is flexibility in a triangle shape from the main spars to the trailing edge. This is caused by severe flexing and can cause some wings to almost flap in flight as the flightloads change from inside to outside manuevers and back. If the wing is covered, reshrinking the covering or even turning up the temperature a bit and sealing the covering to the foam can greatly increase the strength and cut down on the flex. If the foam is truely damaged and you want to take aggressive action, I have had very good luck using Urethane glues such as Elmer's ProBond. These are the glues that need a bit of moisture and foam up a bit as they dry. I've had really good success with taking the pointy nose of the ProBond bottle and driving it into the area near the flex in a pattern of holes about 1/2 an inch apart and squeezing to put glue into the heart of the wing. The foaming action will drive glue between the foam beads and bond the area together and add support. The glue will foam up out of the holes and needs to be sanded off and filled with a little spackle similar to the missing foam chunks repairs listed above.
After a while you'll find that you get good at getting near the other guy and eventually you'll have a head on mid-air. Lots of times these will shear off a wing panel. The most important thing is to grab all the big pieces of foam and bring them home. In many cases this is just a major version of the missing foam chunks repairs but sometimes you need a bit more work. The leading edge is a major piece of structure in the wing. If it gets splintered, it's usually best to replace it. Run a knife down the back side glue joint and separate it from the wing. Then just go to your local lumber yard and get a piece of half inch half round pine molding and replace it. This will rejuvenate a wing far better than trying to glue the leading edge pieces back together. Make sure you replace the fiber tape spanwise spar on the repaired wing. Similarly, you might want to replace the elevon of it gets shattered in the mid-air. Repaired elevons tend to not be flat and will put strange twists into your flights if you just glue them back together.
So, you've had a bad month and totalled your two Gremlins and it happens to be one left panel and one right panel. Many times you can successfully graft a panel onto a plane using the original spars from one panel. The hard part is getting the bad spar out of the donor wing. If possible, try to use the front spar from one panel and the rear spar from the other to get the best support in the repaired wing center section. Don't be afraid to cut a rectangular block of foam out around the spar and use that to glue into the new panel. There's no point in making a lousy wood to foam joint when the foam is so much weaker than the wood or glue. A larger gluing surface in a foam to foam repair will end up being more durable. The foam will fail before the glue joint anyway. I like to use the urethane glues in this application because the foaming action tends to fill in the gaps that come from taking the spars out. Remember the spackle and fiber tape spar once it's back together. Remember to save those mid-air bits, they might be just what you need after the next one. Many times I've left the different covering schemes on the two panels after the repair. It gives you a good reference in the air and your competition something extra to think about when they attack. They know you're not going to be afraid to mix it up again.
Creation date: Sunday August 5, 2001
Last updated: Sunday August 5, 2001