Max Velocity for 3" rocket

[xenon]

In September I plan on flying my modified LOC Caliber ISP on a J motor. I want this to be my first 1 mile+ flight so I need a good sized J to get it up there. I am wondering, what is the fastest I should push this rocket?
It is unglassed LOC cardboard tube. The fins are glued through the wall with epoxy fillets and foam. Is 500mph too fast?

 

[GL-P]

The fins are glued through the wall with epoxy fillets and foam. Is 500mph too fast?

I would guess no. LOC tubing is pretty strong stuff. As long as you used good epoxy (not 5min) and sanded before you glued, you should be okay. Don't take this as the final word though!!!

 

[gothique_97]

500 mph is reaching the upper limits of the durability of unglassed LOC 3" airframe. I've seen many stock Calipers fly on J90s and J180s and do very well. A J275 is pushing it.

 

[xenon]

Well, a J90 couldn't lift it and I can't get a J180. I was thinking more like a J380 or J295. It will barely break a mile on the J380, and it should break a mile on the J295 though. I'd like to fly the J380 because I like the SS propelant, but if it won't break a mile, I won't.
On either motor (actually I'm siming it using the J415W and J450ST) it is below 500mph, not much more than 10 or 15 mph though.

BTW, my rocket weighs 6-7 pounds without the motor and is 3 feet longer also. So it won't go near as fast or as high as a stock 2lbs Caliber ISP

 

[Ryan S.]

if your rocket flies straight you will be fine

 

[xenon]

Originally posted by Ryan S.
if your rocket flies straight you will be fine

does anybody not fly their rockets strait

It generally flies in fairly strait so that is good.

I did some more simming, and at 575 mph (much faster than I'm expecting) there will be 1.15 pounds of drag on each fin. I have hung 7.5 pounds of weight from each fin, and they held up just fine and could probably take twice that. I think it will hold up just fine but I wanted to make sure

 

[cls]

I think the rule is: if you are going for speed, use a high impulse motor. if you are going for altitude, use a lower impulse motor which will burn longer, lower burnout speed, less drag, longer coasting, etc.

many times on J350s I flew my LOC Caliber to almost exactly a mile - a few times over, a few times under, as measured by perfectflite mawd. A few times I used CTI J210s & J280s to get more altitude, 6300' or so.

after more than a dozen of these flights, the lower airframe is showing spirals and slight crumpling forward of the fins & MMT area. some of that damage may be from transportation and ungentle handling. overall though I think Gothique is right, those high impulse Js are pretty near the limit for plain 3" tube.


it would have lasted longer if I had stuck to I motors, or glassed it, or perhaps just glued some couplers in the airframe. but it would not have performed as well.


instead of fretting about it I bought a new piece of LOC 3", a 54mm MMT, and some plywood - I'll just make a new booster section. I already have two payload sections for it (one plain, one dual-deploy), maybe I should replace the parachute...


this is starting to sound like Grandfathers' Axe: the handle's been replaced a few times, and the head was sharpened many times and then replaced, a couple new handles ... but it is still Grandfather's Axe.

 

[xenon]

Thanks cls,
Unfortunatly, with the many mods and all the other stuff in mine (video camera, altimeter, backup timer, extra 3 feet of tube, larger parachutes, dual deployment, longer MMT, etc.) it weighs too much to break a mile on a J350, J280, J210 or J315 for that matter. Liftoff weight on a J144 is about 10 pounds. Even if I get rid of all the extras I can, it still won't break a mile.
The whole point of this flight is to break a mile (can't you tell . )

On RocSim, if I make mine weigh 3.3 lbs w/ out a motor, it says it goes 625mph and a bit less than a mile. This is 150 mph faster than I plan on flying mine. I asume yours weighs about 3.3 pounds. If so, I think I should be fine.

 

[Ryan S.]

if the rocket can take a J350 it could easily take a J275 the J275 has less chance of ripping it up

I have seen rockets not fly straight, all the time in fact.

 

[xenon]

From what people have said, I think it will be fine. The velocity will be less than a stock one with a J350 and max thrust will be less. On the previous five flights it has not done any coning, so pitch-roll coupling shouldn't be a problem. Now the only problem is getting the money to buy a J380...........

 

[shrox]

"Max Velocity for 3" rocket"

About 186,000 miles per second?

 

[GL-P]

Einstein would disagree!

I physically can't go into any further deatil. My brain will explode.lol

 

[cls]

Xenon, just for a data point, my LOC Caliber weighs 1315 grams dry, with dual-recovery section, without motor & propellant. that's a bit better than the 1500g (3.3#) you simmed with. that's a small difference compared to the weight of video camera, etc.

if you want to break a mile then how about a K185 instead of J350

 

[xenon]

On my sim, If I make it weigh 1315 grams, it goes 667mph with an altitude of a bit less than a mile. If I use the original sim for my rocket with the weight of my rocket (about 6.15lbs), it goes 562mph and a bit over 6k on a J415. It doesn't look like the J380 will get it high enough so I'll probably end up with the J295 unless I can get a J415 or K185.

 

[Stymye]

it goes 667mph with an altitude of a bit less than a mi

wow thats approaching mach..but not quite ,, I've read that there is considerable stress and buffeting in that speed range,is this true? or would it matter

 

[GL-P]

wow thats approaching mach..but not quite ,, I've read that there is considerable stress and buffeting in that speed range,is this true? or would it matter

Yes there is... It would matter!!!

 

[xenon]

Update:
the motor has changed from a J380SS to a J370 Green Gorilla, they have similar average thrust, total impulse, burn. It should be in Monday, but the flight has been bumped to October.

 

[Ryan S.]

Originally posted by xenon
does anybody not fly their rockets strait

It generally flies in fairly strait so that is good.

no, but say your body tubes arent exactly straight where they meet at a coupler, then they are going to get cocked sideways, this may put enogh stress on the Body tube and/or coupler to cause you problems

 

[xenon]

I flew the rocket yesterday on a J400SS. It went strait up to 3824ft., my highest flight yet! The main came out at apogee but drift wasn't a problem as it was basicly dead calm (in Nebraska!). I will fly the J370 in April when I can get a case.

 

[Karl]

Congratulations! Sounded like a great flight? So have you still got all 4 fins intact?
Karl

 

[xenon]

Near perfect. Everything is fine exept for the drouge that I was hoping would strip, and it did (I wanted a new one anyway) and the main out at apogee. It was pretty cool with two backup drouge charges....pop pop pop

 

[JDcluster]

I glassed mine: body tubes & fins then I used a jacketed steel cable for shock cord anchor.

To date I've only tickled it with a few mid-range I's with no damage. It was lost for over a month & all was fine.



JD

 

[xenon]

Originally posted by JDcluster
I glassed mine: body tubes & fins then I used a jacketed steel cable for shock cord anchor.

To date I've only tickled it with a few mid-range I's with no damage. It was lost for over a month & all was fine.



JD

Cool! If it is glassed it probably could take small Ks
Mine has flown 6 times with no damage exept for a J144 Cato that caused some zippering.
The thing I like about it is it has a small fin span so there is very little flutter, a good thing for fast flights.

 

[Evil Prince]

Unglassed rockets can be (and have been) flown near M2.5 AS LONG AS THE >M component of the flight is at 0° AOA.


P.S. I wish I knew I could fly J's before I was 18. How does one do that?

 

[Elapid]

Originally posted by Evil Prince

P.S. I wish I knew I could fly J's before I was 18. How does one do that?

all you have to do is have complete disrespect for the laws and rules governing High Power Rocketry and a total disregard for the HPR safety code and your fellow rocketeers.

i'd sure like to see an example made of a few of em.
but i guess tripoli and NAR are more into collecting revenues than enforcing their own rules.

 

[hokkyokusei]

Originally posted by Elapid
all you have to do is have complete disrespect for the laws and rules governing High Power Rocketry and a total disregard for the HPR safety code and your fellow rocketeers.

Depends what the rules are where you live, I guess. Over here it can be perfectly legal to fly a J under 18.

 

[xenon]

Sorry,
I forgot to mention my dad built the motor and put it in the rocket and he put his name on the flight card. He also supervised all other parts of the prep and launch.

 

[r1dermon]

i dont like the fact that NAR imposes limits on what you can and cannot fly. especially since you must be a member, which costs yearly fees, in order to fly anything H and above. i think this type of thing should be governed by the government. thats why they're called the government. and im sure that the government would have a better way to combat people who dont follow the rules. the NAR is simply an organization that determines if a particular motor is suitable for flight, and if the flyer is knowledgeable enough to fly it. i think it's rediculous to say that because i am not a member, i cannot participate in flying high powered rockets. i believe that the NAR only governs rockets at THEIR launches. but in no way would it be illegal(as long as i abide by the FAA rules) for me to create my own rocket motor and fly that. (some towns say that any model rocket must be flown on a commercially produced motor) as long as i am not participating in an NAR sanctioned event. however, prettymuch, anything that has to do with black powder or rocket propellents(yes, even the ingredients by themselves) you must be 18 to purchase. heh. so there are no ways around it.

 

[GL-P]

all you have to do is have complete disrespect for the laws and rules governing High Power Rocketry and a total disregard for the HPR safety code and your fellow rocketeers.

That is specific for NAR and TRA members only, not all high power rocketeers. It's perfectly legal for a member of CAR to certify if under 18. I realize that you mention TRA and NAR members later but I want to keep the record straight.

 

[r1dermon]

but GL-P, i've yet to find a site that will sell to me a casing higher than an H if i am not NAR or TRA certified. even chemical sites wont sell magnesium 1000 to me without at least lvl 1 cert. if im going to pay for a membership to have access to a cert level, i'd rather have that money go to a public pool, designated to rocketry. sortof like fishing. you pay a fishing license to fish in most states. and in those states, the money you pay goes toward stocking and maintaining lakes and rivers....in rocketry, the annual fee could be used for upkeep of an accessible field that is rocket designated and accessible by anyone who wishes. it would also provide security presence and a boat load of other things. instead of the NAR getting it and stuffing it in their wallets.