Estes Leviathan, My first MPR build.

Hello all. I just pulled the trigger and bought my first MPR rocket, an Estes Leviathan. I plan on building properly and robust enough to be a regular flyer and a L1 Cert. rocket. Currently I plan to put in a cold air baffle. I am considering a modification to the fins so the trailing edge angles slightly forward of the rocket bottom. Currently, I see these pros/cons. Pros: Makes the fins more robust on landing, I like the look. Cons: Per my OpenRocket sim, it drops my stability down to 1.1 caliber when flying a small H (plan to use as L1 Cert rocket).

Question 1: What is the ideal stability? Is 1.1 caliber good, or just barely good?
Question 2: Any other mods you think will improve reliability or robustness? If so, what are the pros/cons?

I plan on doing a well documented build thread. Not sure if I will base it off of this thread, or start a new, pure build thread.

Wish me luck guys.

PS. A lot of great advice guys. But no one has addressed the stability question (Question 1). Any good rule of thumbs for how many caliber on Mid-power to Level 1 rockets?

add a little weight in the nose to increase the stability.

don't install the motor block in the motor mount tube. this will allow you to put any size 29mm casing in there.

you can screw an eye bolt into the top of the baffle for the shock cord mounting if you don't want to do the tri-fold thing.

have fun!

here is a radical idea, don't overbuild it , seriously almost anything you do to add strength will make it heavier which in turn means it needs to get even heavier to handle the extra weight. it doesn't need to survive your cert flight undamaged, it just needs to be able to be to fly safely w/o repairs. a chipped fin may not be pretty but it likely will not disqualify the flight. I would limit modifications to minimum required. and yes lose the motor block, it is a holdover from when motor didn't have thrust rings. another idea would be to upgrade the chute to a ripstop nylon version, top flight makes some nice ones.
rex

when built as per the instructions(sans motor block, which is optional) they have been flown on I200's .
rex

I wholeheartedly concur on the "don't overbuild"!!

I did my L1 cert on mine (using a 29mm three-grain CTI "baby H"). I did turn the upper few inches into a payload section and I didn't install the aft centering ring until after I could fillet the fins to the motor tube and the inside of the body tube, but that's about it. I had BMS cut me a pair of ply discs so I could make a Semroc two-tube style baffle. Oh - I did epoxy about an ounce of lead wire (sold at sporting good stores for sinker material) in the nose cone to up the stability margin a touch. Probably it isn't necessary.

Dereck, Bernard and Rex,

Thanks for the input.
I was planning on adding the eye hook to the baffle and not using the engine block. The baffle will require a longer motor mount which will allow for bigger engines too. I had not thought about adding nose weight, but probably will (run it through the sim first).

Rex,

Is the stock chute Nylon, but not "Ripstop Nylon"? Are the stock Estes PS chutes "shred-prone"?

correct, if perchance you get a hot ember that melts a small hole(1/16" or less) they tend to split. shred? as long as you keep them away from heat with a good match of delays they should hold up for some time. however to eliminate the chance for a boo-boo in a cert flight.... as for the fins after some thought, if it were me...I might consider lopping say a 1/4" off the aft edge (blunt the tip) and round off the edges a bit. those two changes would reduce the odds of chipping a fin. the weakest link in the psII birds IMO isn't the fins but the motor tube being a smidge more flexible than I would like. that said they are good intro kits.

are you putting the baffle in the mmt? why not put it in the coupler like everyone else does? then you can use the stock mmt.

see here:

https://www.rocketryforum.com/showthread.php?40747-Estes-Pro-Series-Leviathan-With-Baffle-System

Rex R said:

correct, if perchance you get a hot ember that melts a small hole(1/16" or less) they tend to split. shred? as long as you keep them away from heat with a good match of delays they should hold up for some time. however to eliminate the chance for a boo-boo in a cert flight.... as for the fins after some thought, if it were me...I might consider lopping say a 1/4" off the aft edge (blunt the tip) and round off the edges a bit. those two changes would reduce the odds of chipping a fin. the weakest link in the psII birds IMO isn't the fins but the motor tube being a smidge more flexible than I would like. that said they are good intro kits.

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that happened with my ventris.

tube flexed did it? mine too(landed on pavement), chipped the paint on the fin and cracked the paint on the Bt...other than some cosmetic damage it seems to be holding up (touch wood). with composite motors not needing a motor block, the motor tube doesn't need to be over long, Except if you need a stuffer tube to reduce tube volume.
rex

Rex R said:

tube flexed did it? mine too(landed on pavement), chipped the paint on the fin and cracked the paint on the Bt...other than some cosmetic damage it seems to be holding up (touch wood). with composite motors not needing a motor block, the motor tube doesn't need to be over long, Except if you need a stuffer tube to reduce tube volume.
rex

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oh no. the exterior is actually in pristine shape. I was talking about the holes in the chute! It happened on the first launch. I have since stuffed more dog barf and wadding in there to prevent it from happening again. and I specifically put a baffle in there to reduce the amount of wadding needed! I think my half moons were too small.

I tried a nomex blanket, but it was a really tight fit and I'm not sure if it would have ejected completely.

sorry!

My baffle is in the coupler. I would extend the MMT to a about 1/2 - 1" below top of coupler, then put a bulkhead (1/8" birch ply?) at top of coupler. Then extend 4 BT20s (if enough room) through the bulkead and down to about 1/2-1? above the top centering ring. See pics. Thet came from an Apagogee newsletter.

Also, I am thinking 10/10 rail buttons. Anyone think that might not be a good idea?

baffle design looks good and you should have enough room*...I'd draw it on paper first though . if you're going to fly it on 'H' motors then most places will probably insist on, either a 3/8" lugs or rail buttons. methinks that 1/4" lugs on one side and buttons on the other would allow you to use a rod for mid power motors (say at a non club event) then switch over to a rail for 'hpr' launches (unless of course you have a rail launcher setting at the house ).
rex
* you'll need about a 1/3" or more clearance between tubes and the end plates.

Thanks Rex. Didn't think about both. I think it comes with 1/4". I only have a 1/8" for my smaller stuff. I think I am going to limit myself to clubs with this. Hard to find room for anything over 1000' around here.

CZ Brat said:

My baffle is in the coupler. I would extend the MMT to a about 1/2 - 1" below top of coupler, then put a bulkhead (1/8" birch ply?) at top of coupler. Then extend 4 BT20s (if enough room) through the bulkead and down to about 1/2-1? above the top centering ring. See pics. Thet came from an Apagogee newsletter.

Also, I am thinking 10/10 rail buttons. Anyone think that might not be a good idea?

Click to expand...

I see what type of baffle you are building now. extending the mmt makes sense.

I'd put buttons on it too. flexibilty is a good thing. epoxy a couple of plywood blocks to the upper and lower centering rings to give yourself a bigger target to hit and give the screws more material to bite into.

I'm not sure of the benefits of the baffle over just using a nomex blanket. Baffles work great, but they do add weight. I have a number of flights on my Leviathan and the only thing I changed was to add a nomex blanket, install buttons, and drill two holes in the nose cone to loop kevlar around instead of using the lug.

The fins seem to be holding up fine so far. About the only thing I would change on the next one is to wrap the BT with 2.5 oz of fiberglass. The stock Estes tubes seem a little soft to me, plus the fiberglass adds some durability with little weight. Another plus is you don't have to fill the spirals!

Derek said:

I'd put buttons on it too. flexibilty is a good thing. epoxy a couple of plywood blocks to the upper and lower centering rings to give yourself a bigger target to hit and give the screws more material to bite into.

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Like this:

https://www.rocketryforum.com/showt...cratch-build-Centurion-XL&p=311931#post311931

qquake2k said:

Like this:

https://www.rocketryforum.com/showt...cratch-build-Centurion-XL&p=311931#post311931

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exactly! that thread also shows a half moon type baffle, which is simpler to build than the one you proposed.

qquake2k said:

Like this:

https://www.rocketryforum.com/showt...cratch-build-Centurion-XL&p=311931#post311931

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That's what I do, great pics.

Hey guys. I didn't do a build thread, but here are some pics. The baffle design I used is different than what I posted earlier. I plan to fly in April when club has first mid-high power launch.



The baffle is built into the coupler. The MMT (not shown) extends up within .75" of the top of the bulkhead. The gasses then do a 180 going down between the outside of the 29mm MMT and the inside of the 1.6" BT60. Then they hit the CR that is .75" below the end of the BT60 and do another 180 upwards between the outside of the BT60 and the inside of the coupler. The gasses proceed through the (10) .375" holes and up towards the NC. The cross-sectional area of a 29mm MMT is about 1”². I made sure that all gas pathways (including the ten .375" holes) have that or better.

And here are pics of the finished bird. I was pleased with the paint job. The NC tip came out looking very "Missile-Like". I read on here about how to get good masking on the tip of a NC. One guy said use a condom. I tried it and it didn't work. It wanted to roll up the NC and I couldn't get a straight line across. I used a small plastic cup (Jello shot cup?) and it worked great.

Absolutely Outstanding, Great looking Rocket!
Very nice skills you got there too!

JP

Nice paint job - looks good.

fantastic job on the fillets and paint!

You're ready for an H90! That would give that sweet bird an awesome ride!

Thanks for all the nice comments.

mcdereck: Plan to do that this spring/summer.

Qquake2k: I put a 1/4" LOC bulkhead in the top end of the coupler. Then used a cardboard CR for BT60 (1/4" length) glued to bulkhead and top/inner of BT60. The washer OD is just about the ID of the CR. The one BT60 takes the place of multiple BT20s and I think it is simpler to make with a larger gas path. Proof is in the pudding, so we'll see when she flys.

CZ Brat said:

Qquake2k: I put a 1/4" LOC bulkhead in the top end of the coupler. Then used a cardboard CR for BT60 (1/4" length) glued to bulkhead and top/inner of BT60. The washer OD is just about the ID of the CR. The one BT60 takes the place of multiple BT20s and I think it is simpler to make with a larger gas path. Proof is in the pudding, so we'll see when she flys.

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Yes, I'll be very curious to see how well it works.

Plan to Fly 4-25 at club launch here in MN on G80. And I might do a L1 cert on May 18th. Red Arrow Hobbies is refunding L1 and L2 case and propellant, but they told me they have to have the paperwork into AT by 5-31-13

CZ Brat said:

Plan to Fly 4-25 at club launch here in MN on G80. And I might do a L1 cert on May 18th. Red Arrow Hobbies is refunding L1 and L2 case and propellant, but they told me they have to have the paperwork into AT by 5-31-13

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Hey, May 18 is my birthday!