29mm-29mm Minimum diameter...

Well, after talk about this project amoungst others for quite some time, I finally got my fiberglass fins (thanks Doc) and have begun the build.

While I could have put this in the scratch-built section, I chose to put it here to get advice from you all, as the goal of this design is maximum altitude.

To start, I slotted the booster for fins, used a motor case w/ wax paper as a mandrel, and mounted the fins with fairly heavy fillets (with of coarse my fav...West System and a bunch of 404 filler). Cured them in the oven yesterday, and I guess you could consider them semi-through-the-wall, as they sit on the motor case.

Now, as it stands, 29mm phenolic I know is strong enough to endure mach 1 stress (long burn motors) created by the axial flexxing between the two sections...there shouldn't be that much force in the flight which it will first endure (longburn-I staging to an H). But, the whole idea is to have this rocket also endure axial loading under boost from a K670GG minimum diameter booster when it flies successfully, and becomes a three stager.

With the addition of a second 54mm booster, this will be one long skinny rocket. With that being said, the transitions will use outhung motor casings, and the two upper stages become a boosted dart when the K670 burns out (EDIT: didn't mean boosted dart, but they will quickly drag separate).

Knowing that axial/torque (I forget which is the correct term for the leverage affect of a long airframe) loading will take place near the 29mm booster fins- just above the 54-29mm transition, I'm concerned that the high initial thrust will want to snap the airframe just above the fins.

Has anyone experienced similar designs in which this sort of loading on a very long airframe was endured? I'm trying to come up with a relative estimate on just how much reinforcement the 2nd booster or possibly even sustainer need, without overdoing it on the carbon layup, and possibly making it weigh as much as a 38mm, because I have to keep in mind...this is designed more for the 2 stage flight configuration, just needs the added capability for another booster.

Thanks guys.

What speeds will it see ?

What fins are you using ?

Also what motors ?

It hard to say with all the facts.

Alex

Honestly I would just skip the phenolic completley. Just make it a straight carbon fiber rocket. it will be stronger and lighter than anything.
Although I've got to agree with SArocketman, we need a little more info before we can help with that.

Ok, sorry about that, here's a little more detail...

--Configuration #1 (two-stage, total I-impulse): Booster-I69 (5+ sec burn), Sustainer-H50? (also 5+ sec burn)

In configuration one, sustainer speeds will just approach mach 1.0

--Configuration #2 (Three stage, large K-impulse total): 54mm MD booster (K670), drag separating to above configuration, except sustainers H will be replaced with another I69.

I haven't correctly finalized configuration 2's sim file, but I expect speeds to stay under mach 2.

The 29mm booster fins have been mounted in the phenolic nicely, but I can still produce the 54mm booster as well as sustainer in full carbon.

Which will give me better load bearing (G-force loading strength)?...smaller than airframe diameter weave sleeve stretched, or larger diameter sleeve pushed down to the smaller diameter? I remember reading about this but I can't quite remember now.

Are you SURE you want to use an EM motor as a sustainer? They can be hard to light

What about fins thats very important to know.

Size, thickness of the fins.

Alex

Originally posted by pr_rocket04

Which will give me better load bearing (G-force loading strength)?...smaller than airframe diameter weave sleeve stretched, or larger diameter sleeve pushed down to the smaller diameter? I remember reading about this but I can't quite remember now.

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A larger diameter sleeve pushed down to the smaller size. that way all the fibers will be aligned in that direction, and it will have better strength.

also, if you're going to be painting this, consider putting one very thin layer of fiberglass over the carbon fiber as a sanding veil. some people say this isn't necessary, but sanding carbon fiber is not fun at all.

wow, cool. I am working on a minimum diameter 29mm rocket that I am planning to fly on an Ellis H50.... I was also considering putting a 54 or 38mm booster on it. I have the 29mm minimum diameter built and I am in the process of painting it.. Now all I have to decide is if I am goeing to put a booster on it and if it is goeing to be 38mm or 54mm. With a 38mm booster on an I540 staging to an H50 it sims out to about 14,000ft with a max velocity of Mach 1.26. With a 54mm booster it sims out to 21,000ft with a K800BB-H50. the speed on that is Mach 1.48..... In the simulations I have been running it hasent gone over mach 2 with a K motor.... The 29mm part is phenolic tubing rapped with CF.I am just using a 29mm Urathane nosecone from PML the fins are G10. Do you know where you would get a 54mm-29mm transition?? or would that be custome made. Keep updates posted!!!

Originally posted by cjl
Are you SURE you want to use an EM motor as a sustainer? They can be hard to light

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Indeed, they are inconsistent on the pressurization-time side of things...however, lighting them is no problem for me. Last cluster was 3 I39's in an extremely light 3" Tri-Star. 2 motors came up to pressure, well...not so quickly, but then simultaneously. 3rd I69 came to life at about 1000 feet. Not expected, but beautiful flight(of coarse, cocked a bit off the pad, then stabilized into perfect vertical flight). Never saw that rocket ever again.

Originally posted by SARocketMan
What about fins thats very important to know.

Size, thickness of the fins.

Alex

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1/16" G10

Will post sim file shortly.

G10 is fairly heavy, I would recommend some honeycomb fins. I have had some end up being 1/3 the weight of a G10 fin.

Originally posted by Lucas
wow, cool. I am working on a minimum diameter 29mm rocket that I am planning to fly on an Ellis H50.... I was also considering putting a 54 or 38mm booster on it. I have the 29mm minimum diameter built and I am in the process of painting it.. Now all I have to decide is if I am goeing to put a booster on it and if it is goeing to be 38mm or 54mm. With a 38mm booster on an I540 staging to an H50 it sims out to about 14,000ft with a max velocity of Mach 1.26. With a 54mm booster it sims out to 21,000ft with a K800BB-H50. the speed on that is Mach 1.48..... In the simulations I have been running it hasent gone over mach 2 with a K motor.... The 29mm part is phenolic tubing rapped with CF.I am just using a 29mm Urathane nosecone from PML the fins are G10. Do you know where you would get a 54mm-29mm transition?? or would that be custome made. Keep updates posted!!!

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Definitely sounds interesting! The 38/54mm thing is your call...with bigger pockets comes bigger motor mount tubes!

For the transition...use a hollow conical, or even long ogive nosecone. Then use a phenolic motor mount tube, then put holes towards the bottom (aft) of the tube. Cut the nosecone at a point where you have just enough room for the tube fitment and no more. Pour slightly lightened epoxy into the cone, so it will provide more than adequate support for the G related stress, maybe 2" worth actually gripping the tube. Then when you cure, just make sure this tube is centered correctly (in other words, perfectly). Once the epoxy sets up, if you have the room for a small syringe tip, squirt some expanding foam down into the transition...enough to where it is filled completely by it (you can just cut off any excess).

This setup is exactly what I will be doing, maybe even giving it a carbon wrap. However, I am using drag separation w/ "timer destroy" to start the second booster (my timer will be attached directly to the aft of the motor, and destroyed upon ignition), and as mentioned, an overhung (4" worth) 29mm for the strong coupling.

If you need your timer in the transition and like the setup I mentioned, you could use a mini, and set small pieces of all-thread in the tube when you epoxy it for securing a bulkhead, making an ebay below the motor in the unused space.

Thanks for the info as well Nate!!

Here are some pics:

Notice glare on fillets...these are heavily filled with #404 filler, and were wiped to somewhat minimal size as they are semi-through-the-wall, and surround the fins (I tried getting a higher fillet towards the front of each fin tip). When I get some West System 410, I will cover any imperfections and sand before laying any carbon on top:



And this photo is just "for fun" I guess you could say, as it will be cut down and is actually the booster, not the sustainer (but greatly resembles the highly-stable sustainer):

Originally posted by pr_rocket04
I am using drag separation w/ "timer destroy" to start the second booster (my timer will be attached directly to the aft of the motor, and destroyed upon ignition)

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How much does the timer cost that you are planning to use? Is it worth it on a 29mm rocket?

Originally posted by Lucas
How much does the timer cost that you are planning to use? Is it worth it on a 29mm rocket?

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I would guess PR is going for a TRA staging altitude record based on the rocket design and timer situation.

Go get 'em PR !

Here was my idea for I stage record. use a high thrust G/H motor for the booster and light the I69 sustaner ignitor at the very same time using say a quick burst twiggy.

buy the time the ellis comes up to pressure, the booster is done thursting anyway. You will need some thrust vents interstage.

if it doesn't light, the altimeter choice should save the rocket for another go round.

I've yet to have an I69 not light on a quick burst, they are some good ignitors.

Alright... When you use Ellis Mountain motors, especially the long I69 do you put the igniter half way into the motor? Everybody that I have talked to says to put it halfway up into the motor and the directions that came with the Ellis G20 said to put it in untill it touched the top of the motor. I decided to follow what the directions said and when the rocket launched there was a little smoke as the igniter burned then the the case shattered. Only a very small amount of the grain burned and the casing was shattered into about 5 pieces. Do you think that this could have caused the motor to fail? or was it just a bad motor, or something else?

Originally posted by Art Upton
I would guess PR is going for a TRA staging altitude record based on the rocket design and timer situation.

Go get 'em PR !

Here was my idea for I stage record. use a high thrust G/H motor for the booster and light the I69 sustaner ignitor at the very same time using say a quick burst twiggy.

buy the time the ellis comes up to pressure, the booster is done thursting anyway. You will need some thrust vents interstage.

if it doesn't light, the altimeter choice should save the rocket for another go round.

I've yet to have an I69 not light on a quick burst, they are some good ignitors.

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Me, go for an altitude record? Noooooo.

By the way, has anyone checked the TRA I and K staged records? Wonder if they would be hard to break? Hehehe.

While not a bad idea, your thinking is a bit backwards on overall flight efficiency which can be attained...heck with weights, I'm already a bit off myself. You need to take advantage of coast times and aerodynamic efficiency. Remember what max Q is, and when you want to stay under, above, or near it (almost never), throughout the coarse of flight. But I think I've got a decent configuration figured out. Definitely using Quickburst as added assurance.

As far as the above mentioned CATO...sorry to say, but you messed up. Skinny ignitors with a long dip are great for less CATO worries, but as mentioned, you pretty much can't top a Quickburst for a sure-fire ignition. But to put it into perspective, you've got 2 wires run almost 15" into a decent sized core (assuming an I69), bigger than the nozzle of coarse. Take that 15" or wire and push it under high-G's and things can tangle into a ball fairly quickly. Once that knot meets the nozzle throat...yep, you saw it, kaboom.

EDIT: Oh yeah, about the interstage vents, they would be used in three stage configuration, not two. 3 stage is winters project.

I also have a secret method which will prevent a CATO due to ignitor clog in a long motor, and has another added benefit for the Ellis motors. Pretty simple in my perspective, yet never seen used before.

By the way, has anyone checked the TRA I and K staged records? Wonder if they would be hard to break? Hehehe.

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Yeah you could break them.Because the K record does not use the total amount of Ns that you can.

If I was going to go for the K record what I would do is use a K185 in the booster and then a J570.Thats the best way I can see.That advice is free.

Also the ''I'' record could be done in the same way.Using a I211 and then a H128.

1/16" G10

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Sorry I know you think I'm just asking question because I can, but now we know what you are using we can better help you.

What I would do is 1 layer of 2.3 oz carbon fiber and then a 1.5 oz layer of carbon fiber (Or there abouts) and then 1 layer of 1.3 oz fiber glass.

People might think that over the top, but thats what you need when your rocket will do mach 2+

I hope that helps.

Alex

Originally posted by pr_rocket04


While not a bad idea, your thinking is a bit backwards on overall flight efficiency which can be attained...

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While theory has you put the larger motor in the booster, and the smaller one in the sustainer, and use long burns for both.....

In practice however,
I've seen what long burn two-stage rockets do.

They weather cock real bad and fire the second stage horizontal and sometimes they reach the ground under thrust.

While backwards to theory,

My method I've used on some non record attempts gets the rocket boosted fast and straight on a quick burn motor, then lets the long burn do it's thing.

Just like an Aerobee sounding rocket by the way

It's booster was so fast burn the rocekt staged before leaving the launch tower.

Originally posted by Art Upton


They weather cock real bad and fire the second stage horizontal and sometimes they reach the ground under thrust.

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I beg to differ. Maybe on some long burn two stagers they weather cock and fire horizontally, but think about this rocket, what is it lifting? some carbon fiber, a parachute, and a "J" motor. that's about 4 pounds to lift for a motor that produces over 100 pounds of thrust. either way it's going to be well powered and rip off the pad. if you don't believe me, check out John Cokers M class altitude record shot, he used a long burn 54mm L in the booster, and a heavy 38mm sustainer, and that rocket took off so fast it made my head spin because it was still at a 20:1 thrust/weight ratio (which is roughly what this rocket is going to be)

IMHO you'll be fine with long burns in both, but if you really feel iffy about it, then use a medium burn motor to just give it that little extra oomph.

Originally posted by Nate
, but think about this rocket, what is it lifting? some carbon fiber, a parachute, and a "J" motor. that's about 4 pounds to lift for a motor that produces over 100 pounds of thrust. .

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Hi Nate.

I was thinking about PR's rocket

PR mentioned an I69 booster to an H50 .

I've seen the I69 weather cock on a 29mm brid, a Loc Weasel, A LOC IV, and a scratch built.

And I've seen them fly striaght on all the same rockets as well.

Just was my two cents, and I hope it all works out in the end.

Originally posted by Art Upton
Hi Nate.



PR mentioned an I69 booster to an H50 .

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oh ok, you were talking about the 29-29 setup. in that case yes, I agree with you completley. I thought you were saying that the 54mm booster with a K in it would weather cock if it was long burn.

so yes, with an I69 and an H50, you might want to change that out to a faster stronger I motor.

Originally posted by Nate
so yes, with an I69 and an H50, you might want to change that out to a faster stronger I motor.

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While I love the input you guys are feeding me, in response to that, I have to say NOPE. This rocket is being launched from a custom 10 foot tower, not a rail. If the winds are above 3-5mph, I will hold off.

What you are seeing is rockets lifting which are way over stable while also moving slowly, and wind catches the fins the second they leave the pad. This rocket is stable as it leaves the pad, and the sustainer fins are so small they have barely an affect as to cannard-fin type induced weathercocking you commonly see on a breezy day. This rocket will not do that, not under the allowable circumstances I will permit the launch in.

Edit: Also, I will say, the initial pressure spike of the I69 is substantial; once this thing clears the tower, it's off like a bullet.

As I said, my last cluster used I69's. I have a fairly good idea of how they act...the previous rocket was very stable, only two I69's drove it from the pad, and the thrust-to-weight ration would have been even lower, and to top it off, it was a quite breezy day. Launched from a rail, two outside motors lit (as seen by the holes in the ground, and under these circumstances, should have weathercocked even more! But nope, it stabilized home. 3rd I69 took it to 11,000 feet. Unfortunately, we didn't have a man with binoculars that day. I think that rocket became lunch for a combine.

Originally posted by pr_rocket04
. This rocket is being launched from a custom 10 foot tower, not a rail. If the winds are above 3-5mph, I will hold off.

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ok, with the 10 foot tower and a no wind launch, it can work as you say.

God Speed PR on that Record your not going for