Anyone ever seen this happen before?

[DynaSoar]

My AT Wart Hog, on its second flight ever, burned through the motor tube, right at the metal baffle material.
Since the recovery gear all hangs from the baffle cap, you can guess what happened.

Something tells me this shouldn't have happened. I think it's quite likely warranty replaceable, but I didn't get a receipt since I bought it from someone online.

 

[DynaSoar]

Oh yeah, and so much for "CyA only" construction.

 

[loopy]

I've never had it happen before, but I know that Elapid has.

Loopy

 

[cls]

DynaSoar, what motor was it?

is the mesh clogged?

 

[North Star]

I had a serious cato in my Initiator (F22-5J, on the pad) and it melted the plastic 'bung' where the baffle and shock cord mount is. I repaired it by epoxying a nylon shock cord mount to the inside of the tube (the only bit of epoxy BTW - the rest is CA )

Ever since then I've built aerotech kits the basic way with an 'unbunged' motor mount and an epoxied-on shock cord mount . I have a Warthog and a stretched Warthog (twice the length and with a boattail; made after I got 2 Warthog kits at a huge discount) All have flown regularly without damage, despite some heavy landings.

 

[Const Star]

i recon i have had it happen to me before. when i was a kid flying a model rocket that i dont know the name of but was modeled after some plane to space idea or something. after the charge went off inside the rocket it burnt away part of the engine mount, and chared the inside of the rocket. stick a fork in her, sonof a gun is done. kept it over the year but i recently took it apart and sanded em down, then used them to repair another old rocket of mine, gave it a jet fighter look.

 

[rabidsheeep]

i know there was a thread before where the at baffles were clogging because of the red ejection caps... i had looked and in all 3 of my at rockets they had caps in them

i had something like that happen with a quest BP motor where it near blew up my big bertha mount... dunno it that is similar at all...

 

[DynaSoar]

Originally posted by cls
DynaSoar, what motor was it?

is the mesh clogged?

It was an F50-6. The mesh is not clogged. I don't use those red caps. It was only the second flight.

It IS burnt, metal mesh as well as tube. Mesh, very much. It's red. The tube, not as much, but enough to turn brown and weaken it so it blew apart.

rabidsheeep, you certain about that thread? There was another thread I started asking people to say if their baffles became plugged (since so many people said it'd happen). Nobody that looked found a plugged baffle. Quite the opposite, many were deteriorating away, and one found the baffle to be completely gone and the bird still flying fine.

The mesh is packed up into the top end fairly well. Does this happen because of the ejection charges? It's not plugged, but it might be packed tighter than is good for passing the ejection gasses. I've built one with the mesh pushed up to 3" long instead of the full length in the instructions and blowing on it seemed fine. This one wasn't packed tight like that, at least not when built.

I was thinking it might be my fault that the mesh was packed in there because I put my rockets tail first on a piece of PVC for painting and drying. But it barely fits into the tube, so it can't be going through the thrust ring and into the baffle area.

From now on, epoxy in the ATs. 5 minute outside and inside the body, JB Weld on the Jefferies tube and anything touching it, including the inside of the baffle area. THAT'LL keep it from burning. (I will let it dry before inserting the mesh so as not to gum it up).

 

[rabidsheeep]

checking mine they would have easily lessened the possibility of a chute coming out... a few launches with the red caps getting stuck and i think that % would go down quite a bit

 

[Dragon Fire]

I had a big daddy modified for 29 mm have a cato just like that last month on a F20 It was the first flight. It was the new su casing. I think there was a blow by around the top seal or o ring. The rocket was about 30' off the pad. Toasted the hole body tube, even melted the launch lug off the rocket and bubbled the paint, trashed the nylon chute. I maybe able to save and reuse the fins and nose cone but thats it.

 

[r1dermon]

mmm, F50 is a sweet motor too dude...too bad.

 

[Const Star]

Originally posted by Dragon Fire
I had a big daddy modified for 29 mm have a cato just like that last month on a F20 It was the first flight. It was the new su casing. I think there was a blow by around the top seal or o ring. The rocket was about 30' off the pad. Toasted the hole body tube, even melted the launch lug off the rocket and bubbled the paint, trashed the nylon chute. I maybe able to save and reuse the fins and nose cone but thats it.

yeah, same happened to my rocket, salvaged the nose cone and fins, and the engine mount somewhat, but like u said the paint bubbled, and the inside was screwed

 

[Elapid]

Originally posted by Loopy
I've never had it happen before, but I know that Elapid has.

Loopy

i did have that happen, plus i forgot to epoxy the top thrust ring to the airframe!


the burning mesh came down with the chute and landed in dry grass, igniting a brush fire...

 

[DPatell]

The CA isn't a problem, I have flown many-an-Initiator, all with CA. Still in great condition...as a matter of fact I am debating making a few EX motors for it once I get the delays figured out. Really robust rocket.

I dunno what to say, other than I have seen it happen before.

 

[DynaSoar]

Originally posted by DPatell
The CA isn't a problem, I have flown many-an-Initiator, all with CA. Still in great condition...as a matter of fact I am debating making a few EX motors for it once I get the delays figured out. Really robust rocket.

I dunno what to say, other than I have seen it happen before.

Have you flown any that this happened to? Since the body and the centering ring are both intact, the CyA must have given way. Looks to me like a CyA bond is the only thing besides the motor tube keeping the reovery gear and rocket together. If the tube goes, it's just the CyA bond between the ring and body to carry the jerk at deployment and the weight after. An epoxy fillet woud give a flange for the centreing ring to be held by.

 

[MetMan]

I agree with DPatell, I don't think the CA is the problem. Sounds like your mesh baffle was packed to the top (essentially blocking the tube), the MMT blew out, and the over pressure blew out the top centering ring. The burning BP may have weakened the MMT as well, but all that happened pretty quickly...

Epoxy may have held by only yielding enough in s samll area to let the gas escape, but then again, you might have blown out the back end. If you were using a reload, might have lost you case.

MetMan

 

[KermieD]

While I certainly couldn't fault using epoxy, I'm not sure what it would have helped. It may have kept the chute and cap from leaving the rocket itself, but it doesn't look from the pic like the motor tube failed at a joint. Had you used epoxy, it looks like you'd have had a difficult internal repair to make.

 

[Stones]

Originally posted by DynaSoar
...
The mesh is packed up into the top end fairly well. Does this happen because of the ejection charges? It's not plugged, but it might be packed tighter than is good for passing the ejection gasses.
...

It's a good idea to get that mesh "stretched" back to it's installed length. I go in from the rear (mmt) and pull the mesh back and then tap the bottom of the rocket to loosen any build up inside. Helps keep the ejection gasses flowing freely.

 

[DynaSoar]

Originally posted by KermieD
While I certainly couldn't fault using epoxy, I'm not sure what it would have helped. It may have kept the chute and cap from leaving the rocket itself, but it doesn't look from the pic like the motor tube failed at a joint. Had you used epoxy, it looks like you'd have had a difficult internal repair to make.

True, it would have come down in one piece, but probably with either a hole in its side, or the need to make one just to fix that damage.

 

[DPatell]

All of your CA bonds are still intact. If you notice, the tube is ripped. This is common of heat build up at the baffle, which was either clogged or packed to the top, choking it off, and the resulting heat will burn the tube. The tube is charred all the way through, which helps me make this assumption.

After each flight poke the baffle with a straight clothes hanger, and then bend a 1/4" or so L into the top, and pull the baffle down the tube a little. Try to keep it as expanded as possible and as debris-free as possible and you will be fine.

Never have had a problem with aerotech baffles.

 

[DumasBro2]

I have lost a reload case do to a plugged baffle, I don't use the stuff anymore. It's ok if you can remember to keep it clean and stretched out, I'd just as soon use dog barf. I have used both epoxy and CA on AT kits and haven't had a problem either way. After having to replace a fin on my arcas that was constucted with CA I don't have any problems with using CA, it was a pain.

steve

 

[cls]

Looks to me like a CyA bond is the only thing besides the motor tube keeping the reovery gear and rocket together

don't AT fins clip in to the rings on the MMT? doesn't that hold it all together? the CA glue is just to keep the fins clipped in and the rings in place on the MMT.

 

[Stymye]

the parts are interlocking and very tight , cya is fine if you don't sand a loose fit into the parts,, except those finlock rings are just way too tight.

 

[DynaSoar]

Originally posted by cls
don't AT fins clip in to the rings on the MMT? doesn't that hold it all together? the CA glue is just to keep the fins clipped in and the rings in place on the MMT.

The finlock rings stay on the MMT in large part due to the tightness of fit (something people often complain about in building). Likewise, the clips function to hold the fins even without CyA (though that's not enough for flight). The assembled fins and rins prevent the MMT from moving in part due to the fins in the slots.

But with the MMT burned through, the only joint taking up the chute span as the CyA joint between the body and the outside of the top centering ring. Any flex in the rather larger BT would tend to separate the joint at some points.

As noted ealier, am epoxy fillet would have prevented the separation, but would have made the repair very tough, possibly too tough to do.


New news: AT is responding to the problem by sending me a new Wart Hog once I mail this one to them. They're assuming the motor to be at fault because they're replacing that too. As well as the CATO'd motor mentioned elsewhere.

Craig at AT also reports he's about to field test my PVC motor retainer on an Initiator. A personal project, I assume.

 

[rokitflite]

Hi Dynasoar,
There is a problem with that mesh getting very hot and holding heat on the section of the body tube that it is in. When testing the mesh in a standard Estes tube, we found that it would get burn marks from the inside right where the mesh was after one ejection charge. All of the heat from the ejection charge gets trapped and held in that one section for a bit of time. Whenever I build models using the chore boy/cooling mesh, I either use very thick motor mount tubing or put the mesh inside of a coupler to help insulate it from the motor mount tube OR put a sleeve on the outside of the tube that extends a couple of inches past the cooling mesh section in either direction. On the Aerotech kits you might consider moving the mesh down a couple of inches below the vent holes (which further weaken the tube) and putting a pin through the tube & the mesh to hold it in place. This way the heat won't damage the more fragile section with the holes in it. Just a thought.

 

[DynaSoar]

Originally posted by rokitflite
Hi Dynasoar,
There is a problem with that mesh getting very hot and holding heat on the section of the body tube that it is in. When testing the mesh in a standard Estes tube, we found that it would get burn marks from the inside right where the mesh was after one ejection charge. All of the heat from the ejection charge gets trapped and held in that one section for a bit of time. Whenever I build models using the chore boy/cooling mesh, I either use very thick motor mount tubing or put the mesh inside of a coupler to help insulate it from the motor mount tube OR put a sleeve on the outside of the tube that extends a couple of inches past the cooling mesh section in either direction. On the Aerotech kits you might consider moving the mesh down a couple of inches below the vent holes (which further weaken the tube) and putting a pin through the tube & the mesh to hold it in place. This way the heat won't damage the more fragile section with the holes in it. Just a thought.

Excellent suggestion. If I could find foil lined 29mm tube I'd use that. But I will poke some extra holes around the baffle to keep it from holding the heat in.