Seeking advice for repairing body tube and fin road rash damage

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redleder

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So my MDRM launch this weekend was a big success given the horrible launch conditions, but after driving 2hrs to get to the site I was committed to seeing this thing fly. It did really really well for 2 launches (1G40 and 1G80), the Jolly Logic III Altimeter and chute release both worked flawlessly. The flight conditions were constant 5-7mph winds with gusts up to an easy 20mph, low thick cloud cover and a mist in the air. I wasn't planning on breaking any altitude records so this wasn't really a concern. However, on my last launch the wind really gusted and picked the rocket back up after it landed nicley and pulled it to the only road in a 1500 acre vicinity and drug the rocket down the road for about 300ft. As a result, the nose cone got really dinged and scratched, which I can fix easily. The fins and body tube suffered the most damage. I think I can repair the fins with filler or epoxy by building a fin dam but not certain about the tube. Seeking advice from others here on how best to fix this and get her back out on launch pad soon. Pictures attached and thanks for helping.

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AfterBurners

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What would do with the tube is just cut off that section if you wanted to go that route? It would save you on trying to match it. Or maybe sand the area that bad. Use some thin CA to strengthen the card board tube and come back over with a spackling and sand flush? On the fin you could cut a this piece of wood or balsa in about the same shape and sand to blend and of course use something like spot putty glaze for any imperfections
 

JumpJet

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Your damage can be fixed very easily if you have the right stuff. The worst part of the repair is going to be the repainting of the model in those areas. For the body tube and fins I would sand away a little more of the paint that is next to the areas that need to be repaired. About a 1/4" more is all that is needed. For the body tube I would wrap the shoulder of the nose cone with wax paper or something similar and slide it into the body tube so you maintain the roundness of the tube. Mix a batch of either Epoxy resin or Polyester resin, which ever you have available or can beg off of someone. brush a little over the exposed paper areas, so it soaks in. Mix the rest of the resin with Micro Balloons so you have a REALLY thick past. Apply this over the area so it is thicker then needed. When it dries, you simply sand this area until it matches the tube. I would also Tape around this entire area before sanding so you don't scratch up your paint job. If you plan on repainting the entire model then it won't matter if you scratch it up. For the fin I would make a dam out of tape around the edges and proceed just like you did with the nose cone. In fact I would do both parts at the same time.

John Boren
 

redleder

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Your damage can be fixed very easily if you have the right stuff. The worst part of the repair is going to be the repainting of the model in those areas. For the body tube and fins I would sand away a little more of the paint that is next to the areas that need to be repaired. About a 1/4" more is all that is needed. For the body tube I would wrap the shoulder of the nose cone with wax paper or something similar and slide it into the body tube so you maintain the roundness of the tube. Mix a batch of either Epoxy resin or Polyester resin, which ever you have available or can beg off of someone. brush a little over the exposed paper areas, so it soaks in. Mix the rest of the resin with Micro Balloons so you have a REALLY thick past. Apply this over the area so it is thicker then needed. When it dries, you simply sand this area until it matches the tube. I would also Tape around this entire area before sanding so you don't scratch up your paint job. If you plan on repainting the entire model then it won't matter if you scratch it up. For the fin I would make a dam out of tape around the edges and proceed just like you did with the nose cone. In fact I would do both parts at the same time.

John Boren
Thanks for all the great advice John, that is what I was thinking I would try. I've got 5 min epoxy resin. It might look for the polyester type. What are micro balloons and where do I find them? Was thinking of drilling 2 small holes to have something for the polyester resin to really bond into and give a strong bonding point.

Thanks.

Jarod


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Woody's Workshop

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Do as John says, and don't drill holes.
It's not needed.
If you wait a minute or two after mixing the 5 minute resin it will start to thicken on it's own.
Just get it on and in place before it chunks away from itself when applying.
I've never used micro balloons, so I can give advice on those. Seams sanding would leave pin holes or hard to sand, but I don't know.
 

NateLowrie

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Do as John says, and don't drill holes.
It's not needed.
If you wait a minute or two after mixing the 5 minute resin it will start to thicken on it's own.
Just get it on and in place before it chunks away from itself when applying.
I've never used micro balloons, so I can give advice on those. Seams sanding would leave pin holes or hard to sand, but I don't know.
I highly recommend a combination of microballoons and a thixotropic agent like fumed silica. The silica keeps the epoxy from sagging and the microballoons make it super easy to sand, lighter weight, and will turn it into a paste if you mix enough in. Start with 10/5/.3 epoxy/filler/silica ratio (by weight) and if you need to add more microballoons for pastier consistency you can. Both the microballoons and silica are available on amazon in quart sizes for less than $15 total. US composites has it even cheaper.

I've attached a picture of my most recent fillets so you can see the result. Sands just like Bondo and is nice and smooth.
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