Leviathan Modifications

Just couldn't resist getting the Leviathan at Hobby Lobby with the 40% off coupon. I have built several Estes kits in the past, the most recent being a Big Daddy. I will pursue my L1, but thought this would be a good intermediate (and relatively inexpensive) step to improve my building and flying skills. Here's what I am thinking and a few questions.

1) I want to flip the fins upside down for a different look - would need to cut off a small wedge from each fin so they are flush with the aft end of the tube. I will put this into OpenRocket to look at CP/stability.
2) Plan on using epoxy, not wood glue.
3) Going to get the CTI 29mm 3-grain starter set (largest motor I have flown is a black powder E).
4) I have never worked with plywood fins. Do you still use some sort of filler (like you do with balsa) to get a smooth finish?
5) What are the thoughts on flying this on an H for my L1 if all goes well with the build and preliminary F/G motor flights?
6) Plan on ditching the elastic shock cord and looking for different nose cone attachment instead of molded plastic "loop".

Thoughts, ideas, suggestions? Thanks.

Sounds like a solid plan to me! I would be curious to see what the stability margin shows after you flip the fins upside down. Definitely going to be an interesting look but I think it will work out nicely. For the plywood fins, there isnt a lot to fill to make the plywood fins smooth but If i remember correctly I smoothed on a bit of wood filler and smeared it over the surface and sanded down to where the fins were pretty freakin smooth. I don't think you'll have a problem.

For the nosecone attachment, I used the plastic loop that is molded into the nosecone without a problem but if your looking at your cert. 1 flight I wouldn't leave it to chance, Maybe a eyebolt through the bottom of the nosecone attached with a nut from the inside. Just cut a small panel out of the side of the shoulder and attach the nut from inside. This is what I,ve done on my cert. 1 rocket.

As for using the kit for your L1, I have one myself and if you build it right its a pretty solid rocket. On a small H I could see it being a great L1 rocket! Best of Luck man,

Tripp

Just did Open Rocket files for a standard built Leviathan, then another with the fins trimmed and flipped as I am thinking. Suprisingly, the CP only moved forward 1 1/2 cm. I didn't get into the specifics with getting all the mass components in and motor selected. I will move forward and build it with fins flipped. Need to purchase 29mm CTI 3 grain case and simulate largest 3 grain load (just to be on the safe side), then check CG and stability. I haven't added nose weight to a rocket yet, but have followed a bunch of threads on this forum - wouldn't mind having to just for the sake of learning. Tripp, thanks for your input. Anyone else..... suggestions, comments?

epoxy fins and motor tube......never wood glue. filler is for looks only. the plywood fins with this kit are far too thin to expect continued flights over G. DO not invert the fins. The rocket will corkscrew on you no matter how good your build quality is...the fins are marginally 'true'. shock cord is fine and molded loops seems to hold up well. your build quality has to be superior for this rocket to handle an H. sorry if I am a downer but just stick to basics with this 'basic' kit.

a high impulse flight will separate airframe from nose cone. wrap tape around nose cone for snug fit (fin mass provides enough resistance for booster section to separate prematurely from nose cone) GOOD LUCK!

L2 #2190 Richard

Look at the G106 skid for that 3 grain, it is a COOL motor...

kjkcolorado said:

Just couldn't resist getting the Leviathan at Hobby Lobby with the 40% off coupon. I have built several Estes kits in the past, the most recent being a Big Daddy. I will pursue my L1, but thought this would be a good intermediate (and relatively inexpensive) step to improve my building and flying skills. Here's what I am thinking and a few questions.

1) I want to flip the fins upside down for a different look - would need to cut off a small wedge from each fin so they are flush with the aft end of the tube. I will put this into OpenRocket to look at CP/stability.

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It will move your CP forward some..I see someone has stated that..As long as the CG remains at least 1 caliber(body diameter) in front of the CP you're good to go..

2) Plan on using epoxy, not wood glue.

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Commendable, but unnecessary..IF you want to try your hand at epoxy, go for it, but wood glue would be sufficient.

3) Going to get the CTI 29mm 3-grain starter set (largest motor I have flown is a black powder E).

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Good choice! Gives you LOTS of flexibility on motors to fly future rockets on..

4) I have never worked with plywood fins. Do you still use some sort of filler (like you do with balsa) to get a smooth finish?

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You can..But generally a good primer coat will fill it well enough..Unless you want a 'glass smooth' finish..

5) What are the thoughts on flying this on an H for my L1 if all goes well with the build and preliminary F/G motor flights?

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Get LOTS of good keen eyes to help you track it..Cause it WILL go HIGH on an H..

6) Plan on ditching the elastic shock cord and looking for different nose cone attachment instead of molded plastic "loop".

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Excellent ideas..Chop the very base of the nose cone off, tie a good sized knot in your cord, preliminarily super glue it to the tip of the nose cone and then pour some epoxy in there to fully secure it.

Thoughts, ideas, suggestions? Thanks.

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It is doable, just make sure it is solid..And have those good eyes to help you track it!

I trimmed the fins to 'fit' inverted. Here are a couple pics to get an idea of what it will look like (next to my Big Daddy for comparison).

I've flown my 97% stock Leviathan on a CTI H90 (three times so far). Two changes from stock. I extended the shock cord with 10 feet of parachord. Plenty of room. And I used rail buttons instead of launch lugs. I have a distant video of it on an H90 somwhere. I can post it if you would like to see it.

No epoxy just good ole Titebond 2. Nice rocket and fun to fly. If you have the room (it gets mighty high!) it will work great for your level 1 attempt.

Richard, thanks for the heads up on nose cone seperation due to extra drag. Flying this on an "H" is not my main goal, so not a deal breaker. Primary goal is to work on build quality and get comfortable with reloadable motors (F and G if that's all she will take safely). Just for comparison, I would think some of the high power tube rockets would have even more drag. Am I correct that they can overcome this by other high power build techniques (shear pins, altimeter dual deploy, etc)? You are right on the 'trueness' of the fins. One of them in particular needs attention. I moistened all of them slightly and have them clamped together between a couple perfectly square blocks. We'll see if I can get them in better shape.

"Pantherjon", thanks for your feedback and suggestions. I chopped the base of the nose cone on my Big Daddy and did something similar for its shock cord attachment. After attaching the cord would you re-cover the base of the nose cone with a bulk head of sorts?

I know a number of people who have used this and the other new line of Estes rockets to certify for L1 and they fly great on 3 and 4 grain motors. Our club requires rail buttons for all high-powered launches and G launches. It's a good safety rule. Also make the investment in about 12 feet of Kevlar shock cord. As far as the nose cone is concerned, if you use a plywood bulkhead, drill a 1.5" hole in the center and mount a beeline tracker in the nose. Then fly it on 4-grain H's and you won't have to worry about finding it.

These kits are about as strong as the Aerotech kits, and I have flown my AT Mustang almost completely with H motors. It's a real kick to see them zoom into the sky.

The G106 is an awesome motor. the 3-grain H's are barely H's and will do fine. I'd try it with an H54 and see how it flies with a 3-second longer burn. The H87 snd H90 are good motors that will give it a little oomf. If you have chutzpah, Try it on an H410.

Rail buttons! Thanks for the reminder. One question about installing them. I see on larger builds that often the centering rings are targets for screwing rail buttons into. In this case the rings are too thin. Alternative rail button mounting options?

Here is the rather short (and low quality) video. It's moving so fast that I lost it on my iPhone. Flight is a CTI H90 -9. If you freeze the video you can see the nice size of the flame.

[video]https://s1139.beta.photobucket.com/user/derekmc777/media/PinkLeviathanCTIH90-9.mp4.html[/video]


As for the launch lugs I used small pieces of 1/64" ply on the inside of the tube and and small circles of body tube on the outside. Plenty strong.

kjkcolorado said:

Rail buttons! Thanks for the reminder. One question about installing them. I see on larger builds that often the centering rings are targets for screwing rail buttons into. In this case the rings are too thin. Alternative rail button mounting options?

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Instead you can just glue on Acme conformal rail guides. They're not good on 20-pound and up rockets, but anything ten pounds or less they're great.

I've built mine with buttons, kevlar attached to the top centering ring, stock shock cord attached to that. I have my top button just under the where the tubes come together, thru body tube and coupler with an expanding nut holding it in(screwed up my backer, don't use balsa for this). I used titebond II to build and it's fine, molding and trim on the fillets. Flown twice and had no issues. plenty of people have put these up on H's numerous times. Make sure nose cone is snug, they are a bit on the loose side, just add a piece of tape and you shouldn't have any problems. Sims to about ~2100 on the small H's.

For,rail,buttons try the ones from apogee. They come with welding nuts you epoxy inside the body tube while building. Works great for things like this.

You can also glue blocks of wood to your centering rings before you put them in, and just measure carefully so you can drill holes and screw the buttons into the blocks.

"Davidtmp"' could you explain how you attached your Kevlar to the top centering ring? I think there will be enough room for a small u-bolt or eye-bolt, but am concerned the centering rings are too thin for a solid anchor point.

add a plywood backing plate to the top ring for reinforcement or double up the ring. this will also give you a larger target to hit when drilling the hole for the rail button.

If your main goal is a solid MPR, but HPR capable, you really don't need epoxy, u-bolts, eye-bolts, etc. They will just add unnecessary weight with no real benefit.

Wood glue will be stronger for a paper/wood rocket than epoxy, as well as much lighter. Though you might try your hand at epoxy fin fillets just for the practice!

For the nosecone cord attachment, just drill two small holes below the shoulder (where the loop is) and tie your cord through them. Much stronger with no weight added. For attaching to the rocket, do the same thing to the top centering ring. You could also loop it around the motor tube below where you go through the ring.

I love the CTI motors, but for 29mm, you'll get a huge range of MPR motors at significantly lower cost per flight with the Aerotech 29/40-120 hobbyline case. I fly both, but at the small end, Aerotech has more bang for the buck.

Who do you fly with in CO? Have you been up to an NCR launch yet?

-Ken

new2hpr said:

Wood glue will be stronger for a paper/wood rocket than epoxy, as well as much lighter. Though you might try your hand at epoxy fin fillets just for the practice!
-Ken

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Those who say this probably have never used Aeropoxy ES6209, which has more affinity for paper and wood than wood glue does, and is so much stronger that you can use less of it to save weight. It's also cheaper in the long run than hobby (BSI) epoxy, and it doesn't smell bad, and it's more viscous so it doesn't run or drip.

kjkcolorado said:

"Davidtmp"' could you explain how you attached your Kevlar to the top centering ring? I think there will be enough room for a small u-bolt or eye-bolt, but am concerned the centering rings are too thin for a solid anchor point.

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I used an eyebolt. Not really enough room for a Ubolt in there, at least for me. Not sure if they come smaller than what I had, I picked up the smallest Home Depot had. You should be fine though, use a long enough shock cord and you shouldn't have any problems. I used kevlar about 3 rocket lengths worth, then added the shock cord that came with the kit to the end of that. Plenty long.
The one thing I didn't really like was how close the centering rings were. If I were to get another, I might also buy some heavy walled motor mount tubing and extend so the top ring is up near the coupler. With a block added to this, you could screw the buttons thru coupler into wood backer.

Thanks for the feedback on attachment points for the shock cord.

"CarVac", ordering Aeropoxy from Giant Leap is on my list of things to do today. I read the epoxy testing piece on John Coker's website. Aeorpoxy looks like very good quality epoxy.

Ken, I was at NCR this past Saturday. Sent my Big Daddy on it's first flight. Loved it, and you couldn't beat the weather for early February in Colorado! Got to see a lot of MPR and HPR rockets launched. I drove up for the January launch, but they didn't fly due to wind. I also went down to Pueblo a couple weeks ago and watched the SCORE guys launch. That was fun also, but not as many guys there that day. Still want to get out to a CRASH launch too. I was there several years back. Not as excited about their launch site compared to NCR and SCORE.

As far as rail buttons are concerned, with a rocket this light, you could just drill a 1/8" hole, line it with CA glue, and while it is still wet, screw the button into the airframe. My AT mustang has flown at least 10 times on H's and that's how I hold in the buttons. If you want to be safe, screw a nut on the inside end.

Longer shock cord will decrease the strength needed out of your shock cord anchors. We've been talking CTI motors on this thread, and the 3 grain and 4 grain versions have only 1/2 gram of BP.

If you use Kevlar, you can cut a small wedge out of the upper centering ring, tie a knot in the kevlar, leaving 4"-5" on the other end of the knot. Keep the knot on the aft side of your upper centering ring, then epoxy the 4-5" tail below the knot to your motor tube. It's a very strong hold...more than you need...and it weighs a lot less than an eyebolt.

Not much to add to this. I build mine with wood glue. The only epoxy was to glue the 6' peice of 1/8" Kevlar to the MMT and for the fin fillets. I peeled the glassine off the MMT, that helped both the wood glue and the epoxy. I used the elastic that came with the kit on the end of the Kevlar. I did the two holes in the nose cone base to tie the elastic to. I left about 18" of elastic tail hanging off the nose cone and tie the chute to that.

I agree with using the 29/40-120 Hobbyline loads. Love those cases and the variaty of inexpensive loads, I can find G64s for about $10.

If you are going to do your L1 with this, make sure it's a calm day or you're at a huge field because it is going to get up there on an H. BTW if you do use an H, check the amount of powder in the deployment charge. Aerotech supplies 1.5 grams and you don't want to use that much.

How much did yours end up weighing? Mine was 17.2 oz, but I haven't painted it yet.

Handeman said:

How much did yours end up weighing? Mine was 17.2 oz, but I haven't painted it yet.

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Mine is right about 20 oz, painted, no clearcoat. That was with an eye bolt.

I bought a Leviathan today at Hobby Lobby. Interesting kit. Can easily handle, physically, a 6G-XL motor case. I certainly intend to fly my on an "H" motor. In regards to the nose cone loop for holding your shock cord; the plastic molded loop will work fine if you do not put a strain on it. What I do is tie a loop in my shock cord just below the nose cone. IN that loop, between the nose cone and fin can, I tie on my parachute. Then the plastic molded loop on the nose cone has no strain on it other than it's own weight. I plan on putting those plywood fins on my belt sander and rounding the edges or maybe something sharper. I will probably take 1/4-20 nylon machine screws and turn them into rail guides, with a nut on the outside and a lock nut on the inside. For securing my shock cord, I intend to take a 1/4-20 machine screw with a big washer on it pushed through a hole I will drill in the upper centering ring. Thin I intend to get an aluminum 1/4-20 threaded coupler. Drill a hole through the coupler, perpendicular to the main axis, deburr it really well and then take a Kevlar cord, run it thought the drilled hole and tie it off. This will be screwed on to the machine screw with lock washers and glue. I will use epoxy on it because if it holds up OK on an "H", and the RockSim works out OK, I could probably fly it on something bigger. Like an "I". I also believe that I am going to drill holes in the bottom centering ring so that I can get a syringe with a horse needle on it so I can reach inside and place epoxy beads on the motor tube and one the inside of the body tube. Not a lot, but enough to make it secure.

Those are my current thoughts, and I reserve the right to change my mind numerous times. BEAR

Why does everyone hate wood glue? It's way stronger then the ply or paper you're gluing it to. It can be a PIA to put in the motor tube - because it tends to stick when spread thin (pushing in the motor tube to the body tube) but just get the tightbond slow setting glue and that doesn't happen. Strength of (HP) rocket materials is a great website to read....

You are right, I believe when you speak of the strength of wood glue and especially the Tightbond II or even the Gorilla Glue, which has been amazing to me when I have used it on furniture making. I am absolutely certain I can build the Leviathan with wood glue and it will hold together, and now that you have reminded me, I think I will build the rocket that way. The only change will be placing doublers on each side of the fins. (The re-enforcement being necessary if one might fly an "I" motor.) I will have to either leave the last centering ring off while I am gluing or extend the fin slots in the body tube to the end of the tube, build the fins and the centering rings in their entirety, then slide this assembly into the body tube and make repairs where the slots are too long. Nothing an experienced craftsman can't handle, I would think.I think I may extend the length of the motor mount tube to act as a stuffer tube for the ejection charge, and add an additional centering at the top, which should also give greater strength and integrity to the rocket. What do you think cbrarick?