Post by thevon on Sept 7, 2008 8:51:06 GMT 10
After going thru the denial, anger, grief and finally acceptance phases I decided I had to fix my Nemesis wing. So I went to see Jeff and came home with a bag of bits including scrap blue foam and fine fiberglass mat. Since this is my first “proper” moldie repair I thought I’d do a bit of a thread about it, to encourage other moldie newbies like me who have negligible carpentry or panelbeating skills, and are a bit scared of stuffing it up.
After having a crack at this, I have to agree with Jeff etc that it’s not that hard. The skills we’ve been developing for foamies are in some ways much harder, and less rewarding than working on moldies.
This thread is fairly superfluous since there are some excellent ones out there, such as this:
www.aeromod.eu/ and click on “How to Repair”.
This one is amazing too – it shows what can be done if you’re really keen.
www.seat.lonnie.com.au/projects.htm
I didn’t get a pic to show the “raw” damage. This shows the bad spot, after I had trimmed back the mushy bit. The leading edge was also split open either side, and the skin had lifted off part of the spar, but those things were dead simple to fix just by dribbling thin CA in.
I squared it up as much as possible, but had to leave a couple of bites as I didn’t want to cut away too much of the good skin. Got some ¼” balsa and shaped some ribs to go around the break. This is important because it supports around the join, lessening the chance of it breaking where you overlap the glass. Jeff suggested using blue foam for this but I tried it then switched to balsa as I kept dinting the foam when handling it.
Make sure you check that the wing width is constant, ie you’re not forcing the skins apart.
Needles and syringe is an excellent way to wick CA in. If you use the bottle you waste heaps. I was keen to use fast glues for everything. I have no patience.
Mark and cut a piece of blue foam to fit the cutout.
I glued it in with a thin smear of 5 minute epoxy and taped it in with plenty of pressure.
Cut and trimmed it to shape. I also glued some tiny fillets into those extra deficits. This is all really easy. Then made a sanding stick by taping some sandpaper to a piece of pine. Put masking tape all round the area, to keep the sander above the good skin.
It’s most important to ALWAYS use a sanding block so you don’t dig into the surface. On a wing, use a long block to keep the wing profile. I used 120 grit then 180 grit. So easy to sand.
Feels REALLY SMOOTH when finished.
Sand about 8-10mm all round the repair. Try to grind well down to make it depressed below the good skin. Matter of fact, it would be better to do this BEFORE gluing in the foam, since I was worried about digging into the foam and didn’t grind it hard enough. Next time I’ll grind deeper and sand the blue foam level with the depressed edges (more later).
I cut a “V” channel out of the leading edge, and mixed some 5 minute epoxy with microballoons (mine are dark brown! Ugly!). Then pushed them in and mounded them up over the trench. This is to make a harder leading edge. In 20 minutes you can sand it back.
I raided my pile of old foam wing beds, and found some sections that matched the wing profile – one for the top, and one for the bottom.
Jeff had given me some mylar, to use to mold the glass/ epoxy surface. It would have been good for doing one side at a time but in my impatience I wanted to do the epoxying in one go. So I cut some Burrly and creased it to fit.
Now this is new for me – I’ve never really worked with fiberglass cloth properly before. Apparently the pros use Super 77 to stick things in place then epoxy it all together and the 77 “dissolves” into the epoxy. It’s a great tip. I got some greaseproof paper and traced around the exact area I wanted to lay the mat. Then misted a tiny bit of 77 onto the paper. This shot shows the can close, but it was just a posed shot.
In reality you hold the can about 2 feet above the paper and quick squirt across, not towards the target and let a bit of the mist settle onto the paper. A minutes later, lay the mat onto the paper. Then do the same again, misting the first layer of glass, then lay the 2nd layer on. Press it in a bit then cut around the shape with scissors. Dead set easy.
Peel the paper off and stick the glass on – it might have bit of 77 stick still on it – if not, mist again and stick it over the repair area.
You use laminating epoxy to “wet up” the glass. I used West Systems 205 and 206 which is highly recommended. Just use a bit of scrap foam rubber to dab the epoxy in. I thought it would be hard to tell how much to use, but it’s easy. You can see it fill up.
I then taped the Burrly on tightly (shiny side down!!!) with insulating tape. I have rolls of this Nitto tape which is pretty useless so I was happy to use it up. Stretch it tight. I think it would be fine to use masking tape too. But try to get the Burrly (or mylar) very tight.
Then pressed it with the EPP cutouts, then some ply, then some lead on top.
Next morning, peeled it off and it looked really glassy!!! The camera tends to make it look bumpy but it was really smooth.
Now, here’s where I might have gone wrong. The repair was a bit high, so I sanded it back. Being rather obsessive, I kept working at it with sanding blocks till I got it nice and smooth all around. Cosmetics aren’t my style, but I was determined to achieve a Sean/ Shane style repair! In the process I think I ground a lot of my glass mat off. This is where I realized it would have been better to get the foam and edges about 0.5mm lower before laying the mat. But hey, this is my first one … I reckon I’m doing OK so far!
There were some little holes around the epoxy, and I had other spots to fill so on Sean’s advice I went to Supa Cheap and got some Auto Body Filler (polyester filler). Really easy to use, very fast 5 minute cure, and really easy to sand (but sand it soon after it cures when it’s softish).
I did this in several steps – you’ll never get it all right the first go.
Then for painting, I also got some white acrylic primer from Supa Cheap.
Then applied some of the red and the yellow tile spray that I’ve been using for everything! I haven’t finished yet so will post a pic of the finished thing later.
Like I always say: “I MIGHT BE ROUGH, BUT I’M SLOW!”
After having a crack at this, I have to agree with Jeff etc that it’s not that hard. The skills we’ve been developing for foamies are in some ways much harder, and less rewarding than working on moldies.
This thread is fairly superfluous since there are some excellent ones out there, such as this:
www.aeromod.eu/ and click on “How to Repair”.
This one is amazing too – it shows what can be done if you’re really keen.
www.seat.lonnie.com.au/projects.htm
I didn’t get a pic to show the “raw” damage. This shows the bad spot, after I had trimmed back the mushy bit. The leading edge was also split open either side, and the skin had lifted off part of the spar, but those things were dead simple to fix just by dribbling thin CA in.
I squared it up as much as possible, but had to leave a couple of bites as I didn’t want to cut away too much of the good skin. Got some ¼” balsa and shaped some ribs to go around the break. This is important because it supports around the join, lessening the chance of it breaking where you overlap the glass. Jeff suggested using blue foam for this but I tried it then switched to balsa as I kept dinting the foam when handling it.
Make sure you check that the wing width is constant, ie you’re not forcing the skins apart.
Needles and syringe is an excellent way to wick CA in. If you use the bottle you waste heaps. I was keen to use fast glues for everything. I have no patience.
Mark and cut a piece of blue foam to fit the cutout.
I glued it in with a thin smear of 5 minute epoxy and taped it in with plenty of pressure.
Cut and trimmed it to shape. I also glued some tiny fillets into those extra deficits. This is all really easy. Then made a sanding stick by taping some sandpaper to a piece of pine. Put masking tape all round the area, to keep the sander above the good skin.
It’s most important to ALWAYS use a sanding block so you don’t dig into the surface. On a wing, use a long block to keep the wing profile. I used 120 grit then 180 grit. So easy to sand.
Feels REALLY SMOOTH when finished.
Sand about 8-10mm all round the repair. Try to grind well down to make it depressed below the good skin. Matter of fact, it would be better to do this BEFORE gluing in the foam, since I was worried about digging into the foam and didn’t grind it hard enough. Next time I’ll grind deeper and sand the blue foam level with the depressed edges (more later).
I cut a “V” channel out of the leading edge, and mixed some 5 minute epoxy with microballoons (mine are dark brown! Ugly!). Then pushed them in and mounded them up over the trench. This is to make a harder leading edge. In 20 minutes you can sand it back.
I raided my pile of old foam wing beds, and found some sections that matched the wing profile – one for the top, and one for the bottom.
Jeff had given me some mylar, to use to mold the glass/ epoxy surface. It would have been good for doing one side at a time but in my impatience I wanted to do the epoxying in one go. So I cut some Burrly and creased it to fit.
Now this is new for me – I’ve never really worked with fiberglass cloth properly before. Apparently the pros use Super 77 to stick things in place then epoxy it all together and the 77 “dissolves” into the epoxy. It’s a great tip. I got some greaseproof paper and traced around the exact area I wanted to lay the mat. Then misted a tiny bit of 77 onto the paper. This shot shows the can close, but it was just a posed shot.
In reality you hold the can about 2 feet above the paper and quick squirt across, not towards the target and let a bit of the mist settle onto the paper. A minutes later, lay the mat onto the paper. Then do the same again, misting the first layer of glass, then lay the 2nd layer on. Press it in a bit then cut around the shape with scissors. Dead set easy.
Peel the paper off and stick the glass on – it might have bit of 77 stick still on it – if not, mist again and stick it over the repair area.
You use laminating epoxy to “wet up” the glass. I used West Systems 205 and 206 which is highly recommended. Just use a bit of scrap foam rubber to dab the epoxy in. I thought it would be hard to tell how much to use, but it’s easy. You can see it fill up.
I then taped the Burrly on tightly (shiny side down!!!) with insulating tape. I have rolls of this Nitto tape which is pretty useless so I was happy to use it up. Stretch it tight. I think it would be fine to use masking tape too. But try to get the Burrly (or mylar) very tight.
Then pressed it with the EPP cutouts, then some ply, then some lead on top.
Next morning, peeled it off and it looked really glassy!!! The camera tends to make it look bumpy but it was really smooth.
Now, here’s where I might have gone wrong. The repair was a bit high, so I sanded it back. Being rather obsessive, I kept working at it with sanding blocks till I got it nice and smooth all around. Cosmetics aren’t my style, but I was determined to achieve a Sean/ Shane style repair! In the process I think I ground a lot of my glass mat off. This is where I realized it would have been better to get the foam and edges about 0.5mm lower before laying the mat. But hey, this is my first one … I reckon I’m doing OK so far!
There were some little holes around the epoxy, and I had other spots to fill so on Sean’s advice I went to Supa Cheap and got some Auto Body Filler (polyester filler). Really easy to use, very fast 5 minute cure, and really easy to sand (but sand it soon after it cures when it’s softish).
I did this in several steps – you’ll never get it all right the first go.
Then for painting, I also got some white acrylic primer from Supa Cheap.
Then applied some of the red and the yellow tile spray that I’ve been using for everything! I haven’t finished yet so will post a pic of the finished thing later.
Like I always say: “I MIGHT BE ROUGH, BUT I’M SLOW!”
)
…..could always cut the tips off and the first 1/3 and make a short wing slope rocket though lol.
