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Repairing Fiberglass Nosecone with a Chipped Tip

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Gary Mac

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Any suggestions for repairing a fiberglass nosecone with a chipped tip? The damage was from some of the smaller kids handling it at a local science show, not a ballistic landing. As you can see from the photos, it's chipped through the fiberglass layer.

Some ideas I had were to "build" a tip with JB-Weld and sand/paint it back to shape, saw the broken portion off off and try to install a bolt-through metal nosecone tip similar to many of the filament wound tips (would look cool, but not sure where I'd buy the metal part or how difficult it would be to get it aligned though), or just leave it be and fly it as-is, hoping the fiberglass doesn't delaminate from the tip during flight.

For reference, it's a 4" OD 4:1 nosecone, non-filament wound fiberglass. Max load on it will be from a M-1378 briefly taking it to Mach 1.2.

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Gary Mac

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Mods - wasn't sure if this was better to put in The Watering Hole, High Power Rocketry, or some other section. Feel free to relocate it if needed.
 

crossfire

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I have used tne JB method and it worked out very well for me.
 

Speaknoevil

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RocketPoxy would also work and be easier to sand to shape. To give it a bit more "beef" I'd drill a hole with like a #44 bit and embed a small brad nail inside the epoxy build up.
 

afadeev

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Any suggestions for repairing a fiberglass nosecone with a chipped tip? The damage was from some of the smaller kids handling it at a local science show, not a ballistic landing. As you can see from the photos, it's chipped through the fiberglass layer.

Some ideas I had were to "build" a tip with JB-Weld and sand/paint it back to shape, saw the broken portion off off and try to install a bolt-through metal nosecone tip similar to many of the filament wound tips (would look cool, but not sure where I'd buy the metal part or how difficult it would be to get it aligned though), or just leave it be and fly it as-is, hoping the fiberglass doesn't delaminate from the tip during flight.

For reference, it's a 4" OD 4:1 nosecone, non-filament wound fiberglass. Max load on it will be from a M-1378 briefly taking it to Mach 1.2.
Option 1: Fill in the broken area, and shape a new nose point with JBWeld Epoxy.
Option 2: If there is plenty of fiberglass behind the edge of the broken plane (thick nose), rebuild the new nose cone point from where the broken area is now. May take a bit of filing, and might compromise nose cone strength.
Option 3: Buy metal tip for FG nose cones from one of the vendors, and cut it into the existing cone.

Personally, I would start with option #3.
If not viable, then 1 > 2.

Good luck,
a
 

Gary Mac

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Any suggestions as to which vendor's metal nosecone tip I should use if I went route #3? A quick Google search doesn't show any of them selling the tips separately, so at that point I'd just be sending them an email directly. MadCow's look workable if they'll sell one. I assume they are all fairly similar tips, but don't know that from first hand experience.
 
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Andrew_ASC

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Option 4. Sand it flat at tip and run it slightly blunted nosecone like the military does. There were many academic articles PhD level about slightly blunted nosecones. Thermodynamically theoretically they were cool research wise. The theoretical thermodynamically superiorness to pointed was mostly overhyped. Course I’m going to get trolled hard for this suggestion.
 

boatgeek

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What is chipped appears to just be the gelcoat, which is for all intents and purposes paint. It's not structural. I'd use epoxy with a structural filler (JB Weld if you have it on hand), sand it smooth, and call it a day.
 

Mustang67

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If you go with option 3 you can try Wildman for nose tips. He is easy to get ahold of.
 

manixFan

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Another vote for JB weld. I just fixed a broken nosecone like yours using it. As it firmed up I carefully shaped the tip and by the time it hardened it was nearly perfect. But you'll need to make sure you have a good surface to bond to - I had to roughen the area up a bit to add some tooth for it to hold onto.

Good luck,


Tony
 

daveyfire

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About 12 years ago, I repaired a chipped 4” gel coat nose tip using SuperFil. It’s an epoxy-based filler I normally use to get nice fillets, fill pinholes, etc. that sands really easily and is very lightweight. I originally figured it was a temporary repair, but that nosecone has now been up on motors like M4500s and has traveled under Wildman’s motor home for a couple thousand miles and the stuff has held up like a champ.

It’s easier to sand/much lighter than any of the bonding/laminating epoxies you might use.

https://m.aircraftspruce.com/catalog/cmpages/superfil.php?clickkey=12902
 

HASTE

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Drill carefully into the tip with a 2 or 3mm bit, super glue a match stick in and use a caulking gun nozzle cut down to suit you profile as a mold for you epoxy of choice to finish the tip.
 

Gary Mac

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Just an update to close the loop on the thread. I emailed a couple of the nosecone manufacturers looking for a metal tip, and the consensus from them was also not to try replacing it with metal, but instead build it up with epoxy.

For example, Madcow wrote a nice, detailed response:
We sell tips, but they are designed for the filament wound cones which are CNC cut at the tip - you may have a difficult time getting it to match up properly because the hand laid cones may not be exactly round near the tip. Also, not sure if it will be strong enough at the tip to hold the washer without the washer pulling through. We do have a tip for a 4” 4:1 nose cone - they are $15 plus shipping - let me know if you want one and I’ll send you a PayPal invoice.

Thanks!
Mike
I went with a hybrid method of the advice above, particularly Speaknoevil's:
RocketPoxy would also work and be easier to sand to shape. To give it a bit more "beef" I'd drill a hole with like a #44 bit and embed a small brad nail inside the epoxy build up.
I happened to have a broken #46 drill bit that I could embed roughly .2" inside the remaining nosecone tip material, so that's what I did. Abraded, cleaned with IPA, and then built up the rest of the structure with JBweld. Tape made a good enough pre-sanding mold.

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neil_w

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Wow, very nice result! Probably invisible under paint.
 

Speaknoevil

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I didn't really mean to put the whole bit in, instead just use it as a guide hole for a small nail, but you know what--that drill bit is even better and why not?? Great repair!
 
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