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Larry Ruble
13 Posts |
 Posted - 06/25/2005 : 7:08:08 PM
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I recently had what looked like a normal launch but when my flight was over I noticed the center panel had small one and one half inch tears in the fiberglass upper skin just outside the carbon fiber diamond shape reinforcement. The top skin had buckled and seperated from the foam running front to back of the wing on the left and right side of the center panel. This buckling left a dent in the top of the wing running front to back.
Phil can this be repaired to original strength or do I need a new center panel. I have had several of your bagged wings but never seen this happen. Could this wing panel been defective. I have flow it in 3 contests this summer without problem. I was practicing in light wind when this happened. I need your advice I was planning on using this plane at the Nats in less than a month. Thanks. |
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Phil Barnes
100 Posts |
Posted - 06/27/2005 : 1:38:33 PM
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There have been a handfull of these failures to Aegea wing center panels recently. This will happen to any Aegea wing that is launched too hard. It has been known for some time that this wing could not withstand a hard F3J launch. It is only recently that people have been able to break them on an AMA type winch launch.
John Nilsson and Dave Walter of the CRRC club kicked off the rash of Aegea center panel failures by creasing two of them at the ESL contest in lancaster, PA in May, 2005. Here is a link to the ESL winch forum where I talked about that contest. Scroll down to the LASS 2005 post;
http://forums.flyesl.com/topic.asp?TOPIC_ID=108
John and Dave finished their repairs and flew the repaired wings at the June 2005 LISF contest on Long Island. The wings flew well and looked almost perfect, you had to look closely to see the repair. The repair was also extremely well documented with pictures and text. I am very grateful for their efforts in not only making the repairs but also making the repair information available to others who might find it useful.
The repair procedure will be posted soon. |
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flyeslhost
158 Posts |
Posted - 06/27/2005 : 2:37:32 PM
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Aegea Wing Spar Re-Inforcement
Dave Walter & John Nilsson, June 2005
*** pictures to follow ****
This procedure adds a 0.060" Carbon Fiber laminate (CF) strip over the main spar to re-inforce the center wing panel. It was done after we creased two wings on launch.
Prep - We used CST C1625 for the CF strip (0.50" wide, 0.060" deep, 60" long).
The first wing was done with a 1" strip of skin removed. Noting that we could not get the top of the CF strip flush with the foam, we felt it would be better to cut the skin to the width of the strip - one half inch. The second wing was done this way and was fine. This cut of course goes right over the main spar. The photos are for the wing with 1" strip removed.
Before you cut the channel in the wing, you should sand about a 1 1/2" wide area where you're going to cut the channel. This is just to get rid of the paint and scuff the surface. You can use denatured alcohol to remove the paint and then scuff the skin with some sand paper. You should probably mask off the entire wing top other than the 1/2" wide area to keep epoxy off, including epoxy finger prints.
Tape the wing in its bottom bed to the flat work surface. Make sure you have a flat surface for the beds to keep warps out of the wing.
You want to prep the top bed with Mylar. If you don't have Mylar you could put packing tape on them and a light coat of wax to keep them from sticking to the wing.
Step 1) Use a straight edge taped to the top of the wing and a snap-off type knife blade to cut a strip of skin. Make two cuts the entire length of the center panel directly over the spar tube. Make the two cuts about 1/2" apart and then peel off the strip of skin and save it.
Step 2) Make a sanding tool from a scrap of wood about 6" x 2 1/2" x 1". Use 3M77 to attach 1/2" wide strips of a spacer material and then 100 grit sand paper so that the depth is the same as the thickness of the CF strip. Use this tool and the straight edge to sand a slot in the foam that is 1/2" wide and 0.60" deep that the CF strip will fit into. Regularly check the depth (a short piece of the CF strip with a grip will help). You will probably sand the top of the spar somewhat and may not be able to get the full depth everywhere (without excessive sanding of the spar tube).
Step 3) Near the tip ends of the laminate it may be necessary to thin the CF strip to get it to fit since the spar tube may be closer than .060" to the surface. Check the fit of the CF strip.
Step 4) Clean the slot and the CF strip. Epoxy the CF strip in place with slow cure epoxy like West System. Use enough epoxy to ensure that there are no gaps between the CF strip and the underlying foam/spar. The CF strip should sit flush to the top of the skin.
Step 5) Place a strip of wax paper about 4" wide over the CF strip and then the skin strip over that. Place the top bed carefully over the wing.
Step 6) You want to weigh it down as evenly as possible (we used a plank and lots of thick books). The important thing is to keep the wing flat and apply an even pressure on the spar cap. If you did a good job fitting the cap and used enough resin, you don't need a lot of pressure, just enough to make sure the cap is kept flush with the wing.
Step 7) Let it cure for at least 10 hours. Then take it out of the beds. Where you put in the cap probably will not look perfect so you'll have to do some sanding to clean it up. If there are significant dips or cracks, fill with an epoxy filler mix; then sand.
Step 8) After you clean it up, you should put some glass over it to help tie it to the rest of the skin. Use a 1.5" or so wide strip of 2 or 3 ounce glass on a bias (threads at 45 deg to span) and then a slightly wider strip of 1.4 ounce glass (it doesn't have to be on a bias since it is there mostly for aesthetics and you'll wet sand most of it off anyway). I'd recommend using the wax paper 3M77 trick to make these strips. Basically you lightly spray some 3M77 onto some wax paper and then lay the wax paper onto the uncut glass. (spread the glass out on a clean table) This may sound like a pain, and it is a little, especially if you don't have a work area where you can freely spray 3M77. But, if you do this it makes handling the bias cut glass so much easier it will seem worth it. So if you do the wax paper trick, you would then cut the 1.5" wide strip of bias glass from this laminate. Then spray the glass side of this laminate and fix it to wing over the CF strip. Then peel off the wax paper. Depending on the type of 1.4 ounce glass you have, you probably don't have to do the wax paper trick with it. Cut a 2" wide strip of the 1.4 ounce cloth and 3M77 that over the 3 ounce cloth. Then wet the glass out with resin. If you placed the glass well, you probably don't have to put it back in the beds. Once the epoxy cures, wet sand, paint and you're done. You probably will sand off most of the 1.4 ounce glass as well as the edges of the 2 ounce glass. This is okay as long as there is still some glass over the cut lines.
Chordwise Crease
Step 1) sand or scrape off the paint about 1" on each side of the crease.
Step 2) Cut some slits or holes and then steam the area to get the foam to re-form as much as possible. Place a wet paper towel on the area and touch with a monocote iron. Let rest. Then repeat. Make sure the towel is always wet. Then fill any indentation with epoxy filler and let cure. Sand smooth.
Step 3) Put multiple layers of fiberglass ( maybe three or four layers of 1.4oz or 2oz) over the area with the edges staggered such that they don't all end at the same point. After curing this fiberglassed area can be sanded smooth and feathered into the surrounding skin. having the edges of the glass staggered will help to feather out the fiberglass patch.
Step 4) The glass patched area could be painted or a stick on color strip of some sort could be placed over it.
The above glass patch would offer some structural support to the crease but would also be easy to sand and fair into the rest of the wing. I'm thinking that with the carbon laminate strip it may be enough structurally |
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flyeslhost
158 Posts |
Posted - 06/27/2005 : 2:52:25 PM
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Image Insert: too much pedal to the metal
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Image Insert: Just hold still, this won’t take long and the pain will be..., well painful. Make sure bed is on a firm, flat surface.
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Image Insert: Ready to sand on either side of the planned cut.
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Image Insert: Sanding done. Ready to cut the skin strip.
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Image Insert: Skin strip removed. Ready to sand the groove for the CF strip
Image Insert: sanding tool parts. hardwood strips to get req’d depth, then strip of sandpaper.
Image Insert: we reduced tool length to about five inches to deal with changing angle along wing span
Image Insert: Sanding the groove (carefully).
Image Insert: Checking the groove depth – so CF strip will be flush with skin.
Image Insert: Check fit of the half inch wide CF strip.
Image Insert: First clean the groove and CF strip.
Then apply epoxy to the groove. Then to the CF strip bottom.
Image Insert: Insert CF strip and cover with wax paper then add the removed skin strip.
Image Insert: Position top bed, then plank, then ample weight.
Image Insert: Curing done and ready to finish.
Image Insert: the CF strip nice and flush
Image Insert: Sand and steam the crease, then fill all with epoxy filler.
Image Insert: Filler sanded, ready to glass.
Image Insert: After glassing and light sanding
Image Insert:
Image Insert: Spray on some paint, and go fly.
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Aegea Center Panel Failure
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