Leviathan nose cone issues

[dakota196]

I am kit bashing a BD into a Leviathan, and I am wondering if the nose cone will have the same issues as the BD? And also I have upgraded the MM to 29/40-120. There’s a lot of cubic inches in that body tube. Without using a longer MM stuffer tube, will ejection be compromised? The body tubes are together and filled, and I just thought of this. It is built just like the original.

 

[novahobbies]

I've only launched mine once, but the 29mm BP motor had no problems popping the top. If you're worried about the shoulder issue, I think there's a 3d model of a shoulder correction you could have printed. Mine flew beautifully with a slight moment of terror when the chute got slightly tangled with the Kevlar shock cord. It resolved itself.

 

[86mustang408w]

I am kit bashing a BD into a Leviathan, and I am wondering if the nose cone will have the same issues as the BD? And also I have upgraded the MM to 29/40-120. There’s a lot of cubic inches in that body tube. Without using a longer MM stuffer tube, will ejection be compromised? The body tubes are together and filled, and I just thought of this. It is built just like the original.

I just sat down a messed with my one BD and Leviathan. I haven't flown the leviathan yet, so I'm not sure how the nosecone will work out. I feel the longer tube will be more beneficial in a successful ejection event, Ill be launching it soon, and already made one set of mods to the BD nosecone so if need be I'll do the same to the Leviathan. Probably a ground test first on a smaller motor or just use some compressed air to simulate the ejection charge. It's going to be soon I'll post any info if you like? It's not kit bashing, Estes doesn't seem to care about these issues so it's up to us to fix them....

 

[86mustang408w]

I've only launched mine once, but the 29mm BP motor had no problems popping the top. If you're worried about the shoulder issue, I think there's a 3d model of a shoulder correction you could have printed. Mine flew beautifully with a slight moment of terror when the chute got slightly tangled with the Kevlar shock cord. It resolved itself.

I have a pic of that I'll post when I get to my phone...

 

[86mustang408w]

This would be perfect for the NC, its a BD but sure that they use the same ones. I may make or have one made like this...

 

[dakota196]

I've only launched mine once, but the 29mm BP motor had no problems popping the top. If you're worried about the shoulder issue, I think there's a 3d model of a shoulder correction you could have printed. Mine flew beautifully with a slight moment of terror when the chute got slightly tangled with the Kevlar shock cord. It resolved itself.

That’s good to hear. I’ll also be using AT 29/40-120 loads also. I have over built it I think. With casing, chute and hardware, she weighs 16 oz. With propellant, she should weigh around 20 oz.

 

[dakota196]

From what I understand, only the BD has that problem as far as I know.

 

[SolarYellow]

Read the threads on BD nose cone issues. Making sure your NC if fitted with masking tape immediately before heading to the pad is the most basic method, and may be enough. If you can lift the rocket by the nose cone and give it a gentle shake with only a little movement, that's just about right. My personal test for ensuring the NC and packing of the recovery gear is not too tight is to blow in the motor mount with my mouth (before loading the motor, duh) and be able to move the recovery gear and separate the nose cone with comfortable lung pressure. If those two tests are met (one to show it's tight enough, the other to show it's not too tight), it seems to work pretty well. The lung power one might be a challenge with the volume of the Leviathan, though. I have only gone with smaller rockets so far.

 

[novahobbies]

I'm going to go ahead and print a couple of those shoulders on my FDM printer this weekend when a larger project is finished. Don't know if I'll need it but I'd at least like to have it ready if I decide to try it.

 

[4regt4]

That’s good to hear. I’ll also be using AT 29/40-120 loads also. I have over built it I think. With casing, chute and hardware, she weighs 16 oz. With propellant, she should weigh around 20 oz.

I built a Leviathan clone, except I double walled the body tube to take higher thrust 29mm H motors. I filled in the slope area of the nose cone, removed the base, and put a bulkhead in.

What may be of interest is that I did some ground tests of ejection charge. 0.78g of BP gave a somewhat "leisurely" ejection, with the bundled shock cord not quite fully extending. 0.97g was more like a cannon shot. I'm using 0.88g in actual flights.

Hans,

 

[dakota196]

I built a Leviathan clone, except I double walled the body tube to take higher thrust 29mm H motors. I filled in the slope area of the nose cone, removed the base, and put a bulkhead in.

What may be of interest is that I did some ground tests of ejection charge. 0.78g of BP gave a somewhat "leisurely" ejection, with the bundled shock cord not quite fully extending. 0.97g was more like a cannon shot. I'm using 0.88g in actual flights.

Hans,

What H motors are you using? I am limited by my case, 120 mm. Small Hs

 

[dakota196]

Read the threads on BD nose cone issues. Making sure your NC if fitted with masking tape immediately before heading to the pad is the most basic method, and may be enough. If you can lift the rocket by the nose cone and give it a gentle shake with only a little movement, that's just about right. My personal test for ensuring the NC and packing of the recovery gear is not too tight is to blow in the motor mount with my mouth (before loading the motor, duh) and be able to move the recovery gear and separate the nose cone with comfortable lung pressure. If those two tests are met (one to show it's tight enough, the other to show it's not too tight), it seems to work pretty well. The lung power one might be a challenge with the volume of the Leviathan, though. I have only gone with smaller rockets so far.

Again thanks for the coupler. Last coat of primer on. Everything is over built. 16 oz empty.

 

[4regt4]

What H motors are you using? I am limited by my case, 120 mm. Small Hs

I've flown most of the 29mm H's. H128, H238T, H165R, H210R and H180.

Plan on trying the H97J next weekend.

Hans.

 

[Banzai88]

A whole generation of us BARs used the Levi to L1 on all sorts of 29mm composite motors with no issues at all.

 

[86mustang408w]

Read the threads on BD nose cone issues. Making sure your NC if fitted with masking tape immediately before heading to the pad is the most basic method, and may be enough. If you can lift the rocket by the nose cone and give it a gentle shake with only a little movement, that's just about right. My personal test for ensuring the NC and packing of the recovery gear is not too tight is to blow in the motor mount with my mouth (before loading the motor, duh) and be able to move the recovery gear and separate the nose cone with comfortable lung pressure. If those two tests are met (one to show it's tight enough, the other to show it's not too tight), it seems to work pretty well. The lung power one might be a challenge with the volume of the Leviathan, though. I have only gone with smaller rockets so far.

I've done all that down to test blowing or using compressed air to test ejection events, the nosecone can be loose but the ejection charge blows right past the slanted part of nosecone shoulder and mine have never ejected. Tape is certainly not enough for mine to fix the issue, yet other guys have no issues with their rockets...
.

 

[dakota196]

Finally got the last coat of color on her. Tomorrow will shoot the first coat of clear. The nose cone issue, we will see if it will be a problem. First flight will be on a F15 at around 410 ft.

 

[dakota196]

Forgot the pic!

 

[SolarYellow]

I've done all that down to test blowing or using compressed air to test ejection events, the nosecone can be loose but the ejection charge blows right past the slanted part of nosecone shoulder and mine have never ejected. Tape is certainly not enough for mine to fix the issue, yet other guys have no issues with their rockets...
.

Loose is where it goes wrong. It allows drag separation with the Big Daddy, which opens up a vent and the charge never gets a chance to pressurize the airframe. You want the masking tape to "seal" the NC shoulder against the inside of the airframe long enough for the airframe to pressurize and build relative velocity quickly between the nose cone and airframe as the cone starts moving forward. Then, once it "uncorks" and opens up the wedge portion to vent, the NC is already moving rapidly away from the airframe. Also, since the tape ring clears the airframe all at once, the remaining portion of the shoulder should provide little friction to hold them together.

All the strategies for filling the wedge are aimed at getting that same dynamic to happen. The only real reason to fill the wedge, IMO, is to have the "seal" farther down the shoulder, so the NC has a longer travel distance and can thus be propelled to a greater relative velocity before the uncorking happens. So they are still worth doing, and I will continue to do so, but I acknowledge that a proper tape fit, sufficiently tight but not too tight, is probably "good enough."

 

[Back_at_it]

Are you using the big daddy nose cone? If you are then it stands to reason that the same issue will occur. I would think that it would be more of an issue as you are now pressurizing more tube so the overall pressure will be less. If using the BD nose cone I would do the nose cone mod.

 

[86mustang408w]

Loose is where it goes wrong. It allows drag separation with the Big Daddy, which opens up a vent and the charge never gets a chance to pressurize the airframe. You want the masking tape to "seal" the NC shoulder against the inside of the airframe long enough for the airframe to pressurize and build relative velocity quickly between the nose cone and airframe as the cone starts moving forward. Then, once it "uncorks" and opens up the wedge portion to vent, the NC is already moving rapidly away from the airframe. Also, since the tape ring clears the airframe all at once, the remaining portion of the shoulder should provide little friction to hold them together.

All the strategies for filling the wedge are aimed at getting that same dynamic to happen. The only real reason to fill the wedge, IMO, is to have the "seal" farther down the shoulder, so the NC has a longer travel distance and can thus be propelled to a greater relative velocity before the uncorking happens. So they are still worth doing, and I will continue to do so, but I acknowledge that a proper tape fit, sufficiently tight but not too tight, is probably "good enough."

Yeah, I agree and understand everything you typed. You said and I have had the exact thoughts. I've done all I know and even how many tests with the Big Daddy and I got tired of failed flights. And I explain the issue and if some dont have those issues they question everything and then tell say I don't know what im doing. The best things I found with my Big Daddy is a modification to the nosecone or something that fits in the shoulder. I could use it for the Leviathan but I dont really expect issues with that longer Body Tube after thinking about it. And too loose like you said causes a drag separation and I'd rather not destroy that rocket its first flight. I'm almost being overly cautious about that type of nosecone. But thank you, I appreciate your advice and information. My problem like you said with the Big Daddy is too tight and it won't eject it, but too loose and thats bad too. I've never had to intentionally fix a rocket for it to fly properly.

 

[86mustang408w]

Are you using the big daddy nose cone? If you are then it stands to reason that the same issue will occur. I would think that it would be more of an issue as you are now pressurizing more tube so the overall pressure will be less. If using the BD nose cone I would do the nose cone mod.

The Leviathan and Big Daddy use the same nosecone.

 

[K'Tesh]

The Leviathan and Big Daddy use the same nosecone.

But the increased mass of the Leviathan likely prevents the drag separation issue that affects the BD.

 

[Art Upton]

Aerotech nose cones like the 2.56 and others have an angle yet they are not falling from the sky.

IIRC the Estes 3" nose cone is the design that NCR used.

I really think it is part of a stubby Big Daddy rocket and not fitting the nose correctly. Early on in my hobby I have had drag sep on a few rockets before HPR was ever a word.

I learned the "In Defense of Masking Tape" should be used.

 

[86mustang408w]

I launched my Leviathan this past weekend, ejection event was fine. Nothing to worry about. Now the Big Daddy, needed mods....Sorry just passing along info/data for ANYONE with this question. Here's the thread for it, sorry and thank you!!!

 

[86mustang408w]

The ejection is fine, but flew it again 9/16/23 and the NC isn't heavy enough being just plastic. It actually gets tangled around my chute protector and my chute doesn't come out, lol. So I'm going to hack the shoulder off and add a eyelet to give it just a little more weight. Figure I'd update for anyone still wondering.