Wildman Wildthing Jr cracked my nosecone. Should I attempt repair?

[Approx]

I flew my Wildthing for the first time this last weekend. I wasn't sure of my chargers (I know I know, I should've ground tested. The drogue was a 20" motor eject and that did great but a 9.7 grain FFF Pyrodex charge did not budge the two sheer pins on the main. So it hit hard. Now I have a hair line crack in the nose cone. I can grab and it barely flex the crack with a lot of 50-60 pounds (just a guess) of pressure on it so I am thinking I could repair it? Maybe a layer of glass clothe shoved up inside? This is my first fiberglass rocket so I'm not sure. Any advice would be appreciated.

 

[mrwalsh85]

Can you clarify 9.7 grain? How many grams is that?

 

[Banzai88]

Can you clarify 9.7 grain? How many grams is that?

Goggle is your friend.
https://www.google.com/search?q=9.7+grains+to+grams
TLDR: .63 grams. Pretty sure that was never going to shear two #2 shear pins.

As to the OP's question: I would stop drill both ends of the crack, wick some CA into it while flexed, allow it to cure, then put a patch of fiberglass cloth on the inside with some epoxy.

........and ground test.

 

[tsmith1315]

I’d wick thin CA in there a couple of times. A low viscosity epoxy would probably be better, but I don’t know that I’d buy it just for that purpose.

https://usa.sika.com/en/constructio...purpose-epoxies/cracks/sikadur-crack-fix.html

 

[Antares JS]

I flew my Wildthing for the first time this last weekend. I wasn't sure of my chargers (I know I know, I should've ground tested. The drogue was a 20" motor eject and that did great but a 9.7 grain FFF Pyrodex charge did not budge the two sheer pins on the main. So it hit hard. Now I have a hair line crack in the nose cone. I can grab and it barely flex the crack with a lot of 50-60 pounds (just a guess) of pressure on it so I am thinking I could repair it? Maybe a layer of glass clothe shoved up inside? This is my first fiberglass rocket so I'm not sure. Any advice would be appreciated.

9.7 grains works out to about 0.63 grams - way too small for any but the skinniest rockets, plus pyrodex burns differently from actual BP and requires special considerations to use successfully.

You've already acknowledged that you made a mistake by failing to ground test, so at least you understand that.

A piece of fiberglass cloth up the inside of the nose as you suggested should suffice for a repair.

 

[Approx]

I apparently used the onlone charge calculations wrong because my charge was double what those were telling me to use. Since then I have found forums posts that say it should be more like 1.5 to 2 grams.

 

[NateB]

For this application, Pyrodex is not a 1:1 replacement for true Black Powder. Unless someone has made a Pyrodex specific calculator and you properly contained it, the calculator will give you a place to start using BP.

 

[DragonRocketry]

For this application, Pyrodex is not a 1:1 replacement for true Black Powder. Unless someone has made a Pyrodex specific calculator and you properly contained it, the calculator will give you a place to start using BP.

That all depends on the pyrodex. Tripple 7 has been a one to one for me. The only change I made was containing it a little better.

 

[wsume99]

Just want to re-emphasize the importance of ground testing. The only way to know for sure what charge size you need for your rocket is to test your actual rocket. Everyone can and likely will have opinions and feedback about what works/worked for them but what matters is what works for you and your actual application. The only way to know that for certain is to ground test. So take all the advice and recommendations you receive and package that up into your rocket and ground test to make sure it will work for you.

 

[Ez2cDave]

I flew my Wildthing for the first time this last weekend. I wasn't sure of my chargers (I know I know, I should've ground tested. The drogue was a 20" motor eject and that did great but a 9.7 grain FFF Pyrodex charge did not budge the two sheer pins on the main. So it hit hard. Now I have a hair line crack in the nose cone. I can grab and it barely flex the crack with a lot of 50-60 pounds (just a guess) of pressure on it so I am thinking I could repair it? Maybe a layer of glass clothe shoved up inside? This is my first fiberglass rocket so I'm not sure. Any advice would be appreciated.

You might consider filling it with expandable foam . . .

Dave F.