CTI 54mm Tailcone damage

[plugger]

Recently I flew a CTI L935 (P54-6GXL casing) with the CTI manufactured 54mm tailcone. I've previously flown the same tailcone on a K300 flight and it was fine afterwards. This time, well, not so much. As you can see below, the aft end of the tailcone received significant damage from the L935 burn. Not only did it eat away a fair amount of the tailcone but it also caused a fairly significant discoloration to the anodizing around the outside of the base of the tailcone.

Has anyone else seen or experienced this in the past?

 

[blackjack2564]

Yes it's an occasional thing. I've seen 2 or 3 over the years & had slight damage to mine.

Did you notice any abnormal/excessive erosion on the nozzle?

 

[plugger]

Yes it's an occasional thing. I've seen 2 or 3 over the years & had slight damage to mine.

Did you notice any abnormal/excessive erosion on the nozzle?

Thanks for the reply CJ. Sadly I didn't even think to look at the nozzle. :/

 

[Glasspack]

Plugger & CJ, please forgive my ignorance, I have only flown CTI 38mm so far. Sounds like that cone is part of the motor? Not a retainer like the 54mm Aeropack TailCone I have.

Am I understanding you correct ? Or does CTI also make a tail cone retainer ?

Paul

 

[plugger]

Plugger & CJ, please forgive my ignorance, I have only flown CTI 38mm so far. Sounds like that cone is part of the motor? Not a retainer like the 54mm Aeropack TailCone I have.

Am I understanding you correct ? Or does CTI also make a tail cone retainer ?

Paul

Correct Paul. For 38mm CTI motors the rear closure for the motor is part of the disposable reload. For all other CTI motors the rear closure is reusable and has to be purchased separately. In some cases they make tailcone rear closures as well as the standard flat closure. The 29mm tailcone is identical in diameter to the casing while the 54mm and 75mm versions are stepped.

 

[Glasspack]

Thank You …….

 

[blackjack2564]

FYI here are what can be done with 38 plastic rear closure.Turn down with lathe to a tailcone. This is is I motor record holder rocket.

And a 29 tailcone along with motor retention method by DR J.

 

[manixFan]

I've flown several of the 54mm tail cones with L265s and L935s and have seen some slight damage to mine as well, but nothing that bad. A couple of guys looked at it (the tail cone) when it first came out and thought if it was any longer it could cause some Krushnic effect issues. There was a lot of back and forth on it.

It is unfortunate but for MD rockets for me personally it's worth the risk.


Tony

 

[OverTheTop]

From an aerodynamics POV if you keep the taper angle around 7-8deg you can still get laminar flow off the airframe and onto the tailcone. If you go much steeper than that you get flow separation, thus turbulence and more drag. That is, of course, for sub/transonic. Once supersonic you will get a minor expansion shock wave, I think. Been a while since I read the theory...

 

[manixFan]

Now that I see that tailcone and think about my own experiences, I may coat the inside of my tailcone with some JB Weld before the next flight on a L935 as a sacrificial layer. Either that or have it turned back a bit to shorten it and keep it out of harms way.

In retrospect, when I first saw it after BALLS I thought it was corrosion caused by the nasty playa soil reacting with the aluminum. It wasn't until I saw it at Airfest that I realized it was the exhaust eroding the metal.


Tony