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Estes Mammoth with strap on boosters

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Tinker

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I have been wanting to build a staged & clustered rocket for a while, and with Estes sales, I thought I would try it with mostly off the shelf rockets. The plan is to have a PSII booster acting as the 'anchor' of the system, not only acting as a booster, but as the lower support for the booster pods, which will be on little rails as to slide off the sustainer at second stage ignition. I had wanted to use the two Orange Crush rockets for boosters, but with the 3 fin design of the Mammoth and PSII booster, I had to shrink that down to a BT-55 tube instead. First stage will be 2xD12-3's and either a E16-0 or and E12-0 (with adapter) followed by a single F-15-8. My hope is to provide enough thrust with the boosters to make the PSII system take off at a better speed.

Rough sims currently have it going to ~2200 feet and 30 FPS off the rail with the E16-0 (which seems close to my stock Mammoth sims for FPS off the rail) Sims with the E-12 go to ~1900ft and 37 FPS off the rail.

Stability seems good at 2.6 with most items accounted for. Weight seems to be the bigger issue, and is holding down launch speeds. The E-12 gets off the rail faster, but E-12's seem to go boom a lot.....

I need to get a Chute Release before trying this, but I was wondering what your all thoughts were.

I will try to post pics when they are worth taking.

Tinker

 

Nytrunner

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This will look cool if it works! The E12 does have a faster thrust buildup, so that could help out a lot.

Definitely watch that stability.
The mammoth has a much greater L/W ration than 10, so the caliber rule gets sketchy. Aim for a stability margin on the higher side of 8-15% vehicle length (guideline I picked up from some Nasa papers). I imagine a chute release could add some forward weight.
 

Scott_650

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Since I'm sure you've done the calculation - and I'm too lazy to look up all tge pertinent nunbers - what's the all up propellant weight ?
 

Tinker

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Since I'm sure you've done the calculation - and I'm too lazy to look up all tge pertinent nunbers - what's the all up propellant weight ?
Propellent weight is 147.5 g w/ the E16 and 144.4 w/ the E12. If your going with the 125g, I should have my Lvl 1 w/ a different rocket anyway, but I don't really give a hoot about crossing the 125 line. I could make it barely with the E12 and using a E16 in the upper stage for 124.4g, but I doubt I would bother.

Tinker
 

BABAR

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This will look cool if it works! The E12 does have a faster thrust buildup, so that could help out a lot.

Definitely watch that stability.
The mammoth has a much greater L/W ration than 10, so the caliber rule gets sketchy. Aim for a stability margin on the higher side of 8-15% vehicle length (guideline I picked up from some Nasa papers). I imagine a chute release could add some forward weight.
Concept I kind of wonder about. With a cluster rocket, what caliber do you use? Put another way, do you just use the base caliber of main/central tube or do the pods count into the calculating?
 

rharshberger

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Scott_650

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Sure hope you post some video of this critter - all that black powder smoke and flame should be...interesting :drool:
 

Tinker

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My concern is the low off the rail speed 30fps is only a bit over 20mph which is at the very bottom of the recommended velocity.
Thats my worry also. The stock Mammoth on my sims was doing about 30 FPS with a F-15. With the Estes PSII booster, it was like 23 FPS with an E-16 in the booster and an F-15 in the sustainer. This rocket can get the speed back to 30 FPS with the E16 and 37 FPS with the E12 (assuming it doesn't explode).

All this being said, the sims assume a 36" rod and I am pretty sure the rods in Pueblo and Hartsel are 4'+, so in all likelihood the rocket will leave the rail at a better velocity.

Tinker
 

rharshberger

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Make sure when you sim the rod length to use the distance between the top of the rail and the top lug/button. I would recommend fitting with rail buttons in order to take advantage of the stiffer rail, which will prevent rod whip better and allow for a vertical start instead of whipping and causing the rod exit to be off vertical.
 

Tinker

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Make sure when you sim the rod length to use the distance between the top of the rail and the top lug/button. I would recommend fitting with rail buttons in order to take advantage of the stiffer rail, which will prevent rod whip better and allow for a vertical start instead of whipping and causing the rod exit to be off vertical.
Damn good thoughts. It might be time for me to learn about rail buttons. I figured I would do it with my first fiberglass bird, but maybe now is the time to learn. That and the rails are much taller if I recall.

Tinker

PS As long as I can do it, I put in the motor mount already........
 

rharshberger

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Rails can be taller, my local club has 6' and 8' 1010 rails, with extentions to up to 12'. The best source of Rail buttons IMO is railbuttons.com Randy has good prices and great service.
 

Nytrunner

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Concept I kind of wonder about. With a cluster rocket, what caliber do you use? Put another way, do you just use the base caliber of main/central tube or do the pods count into the calculating?
Caliber is a simplification, and thus works best with specific constraints. Transitions, reductions, pods, and strap on all.begin to push the boundaries of that design space. Which is why I lean more towards a % based model.
 

Tinker

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I may try Apogee's Universal rail guides that surface mount w/ epoxy. It is convenient as Apogee is just down the road, so I can bring the rocket and try parts it out. But I think your spot on about using a rail.

Tinker
 

Scott_650

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Thats my worry also. The stock Mammoth on my sims was doing about 30 FPS with a F-15. With the Estes PSII booster, it was like 23 FPS with an E-16 in the booster and an F-15 in the sustainer. This rocket can get the speed back to 30 FPS with the E16 and 37 FPS with the E12 (assuming it doesn't explode).

All this being said, the sims assume a 36" rod and I am pretty sure the rods in Pueblo and Hartsel are 4'+, so in all likelihood the rocket will leave the rail at a better velocity.

Tinker
I launch my Mammoth from a 4' rod regularly - though, since my local launch area isn't all that big, I'm real picky about wind speed. Probably haven't flown it in anything much above a 5-7 mph breeze. But it's been dead stable on both E and F 29mm bp motors.
 

Eric

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That looks awesome. I love my Mammoth on hobbyline reloads. I'm going to into a booster for it. I'll be following.

And definitely go with 1010 buttons. Wildman even has some nice printed streamlined ones.
 

Nytrunner

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I may try Apogee's Universal rail guides that surface mount w/ epoxy. It is convenient as Apogee is just down the road, so I can bring the rocket and try parts it out. But I think your spot on about using a rail.

Tinker
A trick I use for rail buttons that need to go down a tube, is to get a 6-32 weld nut (flat, without spikes) Bend it so it conforms to the inside of the tube better (not perfectly), and stick it to the end of a dowel with a little cylinder of ductape. I'll put a light bead of epoxy around it's flange, and use the rod to guide it into postion from the inside. When you've found the hole, poke it through (it is a little tricky), clean any epoxy that splurges around the stem, and use a 6-32 screw to attach the rail button and hold it in place while the epoxy cures. Once the button is tightened on, you can roll off the dowel and tape.

The goal is to get the nut fixed in place, but allow the button to be removed in case it needs to be repaired.
 

LithosphereRocketry

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Propellent weight is 147.5 g w/ the E16 and 144.4 w/ the E12. If your going with the 125g, I should have my Lvl 1 w/ a different rocket anyway, but I don't really give a hoot about crossing the 125 line. I could make it barely with the E12 and using a E16 in the upper stage for 124.4g, but I doubt I would bother.

Tinker
First of all, this will be cool! :pop:

IIRC >125g propellant weight doesn't need an L1. However it must be launched under an FAA waiver, for example at a club launch.

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Tinker

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I need to separate the boosters from the main fuselage by a small amount as the cap on the booster-55 fin can is a little wider than the bt-55 tube and I don't want the PSII booster catching this lip on it's energetic departure from the sustainer. I have decided to wrap the bt-55 tube and the fin can in a section of tubing I cut open. I am at a loss what adhesive to use though. Elmers white would seem ok except the fin can will get quite hot, but JB Weld seems wasteful on the large area involved where I don't need much strength.

Any suggestions as to what adhesive?

 

LithosphereRocketry

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I need to separate the boosters from the main fuselage by a small amount as the cap on the booster-55 fin can is a little wider than the bt-55 tube and I don't want the PSII booster catching this lip on it energetic departure from the sustainer. I have decided to wrap the bt-55 tube and the fin can in a section of tubing I cut open. I am at a loss what adhesive to use though. Elmers white would seem ok except the fin can will get quite hot, but JB Weld seems wasteful on the large area involved where I don't need much strength.

Any sugestions as as to what adhesive?

Temperature shouldn't be much of an issue- fincans don't really get that hot. However you have to keep in mind that Elmer's glue won't stick to plastic.

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