LOC Hi-Tech shred J350

k-rad du0d · May 16, 2012

Before and after pics. Aerotech J350. I'm not sure what happened first. The guys at the field seemed to think it lost a fin first but the LOC guy suggested that the body tube crumpled first. I don't know if it matters, since it is clear that the materials could not withstand the acceleration/speed/drag. I just thought you all might be interested to see this. It is pretty amazing to me to see such complete destruction happen in mid air through only aerodynamic forces.

I think if the motor would have burned out about .3 seconds earlier, it would have survived. So close...

On that note, the 20% error tolerance for motors is ridiculous.

EeebeeE · May 16, 2012

That looks to me that the tube crumpled because it appears to have happened at the CP. Too bad. It was a nice looking rocket.

neond7 · May 16, 2012

Well, on the bright side:

(a) You now have a spare nose cone.
(b) You got the motor casing back.
(c) The fillets look like they held up, so it wasn't because of your build technique.

The J350W is a heck of a motor, I'll be using one to launch my 14.95 pound LOC Bruiser. It should push it to about 1,100 ft and reach a top speed of about 189 mph. Your 2.6 inch Hi-Tech must have reached 400 mph or more. Maybe touched supersonic?? Have you simmed it with this motor?

Whats the biggest motor you have used on your G-Force? I built mine stock with the motor block, so I'm stuck using 29/40-120 motors. But I'm ok with that, since it flies so nice on a G64W-4. Its a charmed rocket, its flown dozens of time and the only damage it ever got was a chip in the nose when something hit it in the garage......

Since you talked to the LOC guy already, is there a chance they will replace it under warranty since it looks like a body tube crumple?

DAllen · May 16, 2012

What is the top speed for that rocket+motor in a RockSim/Openrocket simulation? Doesn't look like you had electronics on board so I bet that was uber-light.

I'll bet the failure happened around 700 mph.

k-rad du0d · May 16, 2012

neond7 said:
Well, on the bright side:

(a) You now have a spare nose cone.
(b) You got the motor casing back.
(c) The fillets look like they held up, so it wasn't because of your build technique.

The J350W is a heck of a motor, I'll be using one to launch my 14.95 pound LOC Bruiser. It should push it to about 1,100 ft and reach a top speed of about 189 mph. Your 2.6 inch Hi-Tech must have reached 400 mph or more. Maybe touched supersonic?? Have you simmed it with this motor?

Whats the biggest motor you have used on your G-Force? I built mine stock with the motor block, so I'm stuck using 29/40-120 motors. But I'm ok with that, since it flies so nice on a G64W-4. Its a charmed rocket, its flown dozens of time and the only damage it ever got was a chip in the nose when something hit it in the garage......

Since you talked to the LOC guy already, is there a chance they will replace it under warranty since it looks like a body tube crumple?

Openrocket said it would hit Mach 1.1.

I haven't flown the G-Force yet. I have a G138 that I want to put in it but I need to trim that delay by quite a bit. I read somewhere that I can use the HDK-17 to cut it to 7 or 10 or something but I don't know if that will work. I know I could always drill it out, but I'd rather avoid that if possible.

When I talked to the LOC guy, we never reached that topic. I suppose I could ask him. I just figured it was me pushing the rocket too far...

k-rad du0d · May 16, 2012

DAllen said:
What is the top speed for that rocket+motor in a RockSim/Openrocket simulation? Doesn't look like you had electronics on board so I bet that was uber-light.

I'll bet the failure happened around 700 mph.

Around Mach 1.1.

I agree, I think it was pushing the sound barrier when it failed.

DAllen · May 16, 2012

And there is the problem. Mach .8 to 1.2 is transonic. You do not want your projects just hanging out in the transonic region for any length of time because the pressure becomes too high for the airframe to withstand. Either punch through mach or stay .8 or lower.

k-rad du0d · May 16, 2012

DAllen said:
And there is the problem. Mach .8 to 1.2 is transonic. You do not want your projects just hanging out in the transonic region for any length of time because the pressure becomes too high for the airframe to withstand. Either punch through mach or stay .8 or lower.

Indeed.

Peter Olivola · May 16, 2012

Can't see the other fin roots, but I'd suggest fin flutter failure. It only takes one failed fin to produce results you've photographed. Loss of stability would offset the airframe from it's direction of travel sufficiently to produce exactly the kind of failure at exactly the location shown. Achieving trans-sonic speeds only aggravates the flutter problem.

k-rad du0d · May 16, 2012

Peter Olivola said:
Can't see the other fin roots, but I'd suggest fin flutter failure. It only takes one failed fin to produce results you've photographed. Loss of stability would offset the airframe from it's direction of travel sufficiently to produce exactly the kind of failure at exactly the location shown. Achieving trans-sonic speeds only aggravates the flutter problem.

All three fin roots look the same. The epoxy looks like it held perfectly fine.

Yeah, I can't decide which happened first. But, again, I'm not sure that it really matters. The whole thing needed to be reinforced for those kinds of stresses.

J Blatz · May 16, 2012

I would say that fin flutter could have been an issue in this failure - these fins are fairly symmetrically shaped and that is a risk factor for flutter. Many years ago, guys used to routinely shred their LOC EZI-65's using the relatively tame J275 - the fins on that rocket seemed to hit just the right note when flying on that motor. Look at the fins on the Hi-Tech H45 vs the EZI-65...very similar.

Also, all the posters commenting on transonic flight are on the money.

As far as this being a warranty issue, I can't see it. This is just what happens when you put a big motor in a smallish paper/plywood rocket.

grouch · May 16, 2012

It matters to me, I am hoping to push a Nuke Pro past mach and I would like it to hold up. The Nuke seems to be sturdier than the 2.56 bodies and the low aspect ratio fin design seems better suited for high speed. We'll see I guess.

patelldp · May 16, 2012

grouch said:
It matters to me, I am hoping to push a Nuke Pro past mach and I would like it to hold up. The Nuke seems to be sturdier than the 2.56 bodies and the low aspect ratio fin design seems better suited for high speed. We'll see I guess.

The Nuke is a very robust rocket. I have personally flown one on a H220T 29-240 motor to approximately mach with no issues. Surface mount fins, attached at the root with hobby epoxy and 30 minute epoxy fillets.

EeebeeE · May 16, 2012

I think the 2.26 frame of the Nuke Pro Maxx as well as having a lower CD because of the narrower dia, is also proportionately stronger because even though wall thickness is the same, it is thicker by ratio of thickness to dia. than the wall frame of larger dia. rockets. I have a NPM that I intend to fly on a 6XL grain CTI motor. Striving for Mach 1.7 and 10,000 feet.

Of course the fin can is filled with epoxy foam, and the fins are coated in 24-hour penetrating epoxy. I have a transmitter in the nose, a small video camera in the payload bay, and a Stratologger altimeter with an external speaker to help me find the thing. I think I am going to paint it metalic orange.

k-rad du0d · May 16, 2012

After I showed him the pics, the LOC guy agrees that it was probably the fins that failed first. Makes sense.

grouch · May 16, 2012

Thanks for the update. That sounds like what I would guess but it would only be just a guess.

EeebeeE · May 16, 2012

That's where a Nuke Pro Maxx will have a lot less of an issue. Much more streamlined fins. Did you taper yours?

grouch · May 16, 2012

Rounded the leading and training edges. They are slightly thicker than the other LOC kits I have built. I mixed chopped carbon into the epoxy at the motor tube and colloidal silica for the filets. They are the very stiff, no flexing at all.

k-rad du0d · May 16, 2012

grouch said:
Rounded the leading and training edges. They are slightly thicker than the other LOC kits I have built. I mixed chopped carbon into the epoxy at the motor tube and colloidal silica for the filets. They are the very stiff, no flexing at all.

Sounds like overkill to me, but we've seen what I am capable of.

grouch · May 16, 2012

If it's worth killing, it's worth overkilling.

Donaldsrockets · May 16, 2012

k-rad du0d said:
I haven't flown the G-Force yet. I have a G138 that I want to put in it but I need to trim that delay by quite a bit. I read somewhere that I can use the HDK-17 to cut it to 7 or 10 or something but I don't know if that will work. I know I could always drill it out, but I'd rather avoid that if possible.

I've flown my G-Force on the G138T. It was a great flight.

I used the AT delay tool to drill the provided delay down to about 5-6 seconds and the chute popped out right at apogee.

I will also admit that I was never keen on delay drilling until I bought the delay tool but this handy little gadget takes nearly all the guesswork out of it.

k-rad du0d · May 16, 2012

Donaldsrockets said:
I've flown my G-Force on the G138T. It was a great flight.

I used the AT delay tool to drill the provided delay down to about 5-6 seconds and the chute popped out right at apogee.

I will also admit that I was never keen on delay drilling until I bought the delay tool but this handy little gadget takes nearly all the guesswork out of it.

Cool. I've got a bunch of delay kits just sitting around and thought I could just throw one of them in there but I just don't get how they work. I've got the HDK-17 here and somehow the exact same delay creates an F52-8 a G53-7 and a G71-4. I don't get it. Thus, I'm scared to try that approach.

GRIFFIN · May 16, 2012

DAllen said:
And there is the problem. Mach .8 to 1.2 is transonic. You do not want your projects just hanging out in the transonic region for any length of time because the pressure becomes too high for the airframe to withstand. Either punch through mach or stay .8 or lower.

Or fly fiberglass rockets and speed becomes a goal not a wall to stay behind.

Rocketjunkie · May 17, 2012

k-rad du0d said:
Cool. I've got a bunch of delay kits just sitting around and thought I could just throw one of them in there but I just don't get how they work. I've got the HDK-17 here and somehow the exact same delay creates an F52-8 a G53-7 and a G71-4. I don't get it. Thus, I'm scared to try that approach.

The delay burns during the thrust phase. Shorter burning motors will burn less during the thrust phase so the remaining delay will be longer. It's both a function of burn time and pressure.

Rocketjunkie · May 17, 2012

The LOC High Tech H45 and EZI65 are named this for a reason. They are designed for long burn, low thrust motors. Most reloads have far more thrust than these kits are designed for. (That didn't stop me from flying my High Tech on a H999 :smile

CarVac · May 17, 2012

Too bad those motors aren't certified anymore...

VARocketflyer · May 17, 2012

CarVac said:
Too bad those motors aren't certified anymore...

Though the H45 was only certified for use until Dec 2005, the I65 still shows up on the certified list of both TRA and NAR. With that beautiful long burn, the I65 is one of my all-time favorite motors. So in other words, smoke 'em if you've got 'em boys!

Mark

EeebeeE · May 17, 2012

The LOC High Tech H45 and EZI65 are named this for a reason. They are designed for long burn, low thrust motors. Most reloads have far more thrust than these kits are designed for. (That didn't stop me from flying my High Tech on a H999 )

That's OK. I fly my Aerotech Mustang on H163's. Not even the best cameramen can keep up with it. :lol:

k-rad du0d · May 17, 2012

Rocketjunkie said:
The delay burns during the thrust phase. Shorter burning motors will burn less during the thrust phase so the remaining delay will be longer. It's both a function of burn time and pressure.

Do you know how big of a factor pressure is? After sleeping on it, I figured out the other things you said but I thought that the delay grains just burned at a constant rate. Thanks for your help.

k-rad du0d · May 17, 2012

Rocketjunkie said:
The LOC High Tech H45 and EZI65 are named this for a reason. They are designed for long burn, low thrust motors. Most reloads have far more thrust than these kits are designed for. (That didn't stop me from flying my High Tech on a H999 :smile

I think the LOC guy told me about you. Did you get a video?

LOC Hi-Tech shred J350

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