Single Use Engine for Leviathan First Flight

Chunker78 said:

Nice color scheme. What kind of decals?

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Hnefi said:

Bumping this thread because I have a few questions about motor choice... I am planning to fly my Leviathan for the first time in August and I'm just going through the final assembly & paint.

I tend to build heavy (went with wood glue everywhere except for sizeable external fillets), and I added a 3-ring baffle + eyebolt to the coupler assembly among other mods (internal fillets, adding rail buttons). Thrustcurve is saying my single use F42's are unsafe based on a very heavy 750g weight estimate, but based on 42fps off the launch rod. Once I get final weight I think I will be safe because I doubt I will have added 300g to the Estes weight estimate for the Leviathan!!!

I also bought a G54 longburner. :wink: Depending on weather conditions and visibility, I might fly this bad boy as a second launch and put it up over 1800+!!!! To confirm final alt I am thinking about buying a Jolly Alt 2, but the issue with this one is that since I'm in Canada, it's SO SO expensive. $69 + $25 shipping at a 1.25 exchange rate is like $110 for an altimeter that I have more than a slight chance of losing. I also have the option of getting a Firefly for much cheaper, but that would require me to build a custom ebay and learn more about electronics.

What do you guys think? Maybe better to fly the two F motors I already have, and then build an ebay section to house the altimeter AND tracker if I'm going to push this one up to 2k? Could also learn dual deploy that way. I built the fin can as bombproof as I know how because I was thinking about eventually flying this on a 6G XL case to get my L1 - and it seems a shame to fly such a tank fincan on only F and G motors. I'd appreciate your guidance as this is only my second mid power build and not very experienced with electronics and deployment. My experience comes a lot from small model techniques with balsa fins and C6-5 motors.

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SCrocketfan said:

I wouldn't worry about the F42. My leviathan is a bit over 20 oz (after a few rebuilds) and flies fine even on the slower F20/F27s.

The G54 should be a really nice flight. If you have a large enough field to recover single deploy, definitely go for it. You could also get your L1 on the same case- the H54 is only about 10 ns more, or you could fly another 3G faster burning H like the H133 or H90. If you can safely recover the G54 flight on your field, a 3G H should also be fine.

Regarding electronics, it would be pretty easy to mount a Firefly (and tracker if you want) in the nose cone and fly single deploy, or stretch the rocket by adding another tube, put the e-bay in the middle, and fly dual deploy. Both are very good options, but you may want to stick with smaller motors (3 or 4 grain) if you don't either add dual deploy or add a tracker.

Good luck on your first flight! The Leviathan is a great flyer.

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rstaff3 said:

I'd have a hard time believing you built it too heavy for the G54, however you still should probably do some sort of sim to get the right delay. Whether you should put it up on G vs. your Fs depends on the field and the wind. You gotta judge that. Again, a sim will give a rough idea on the drift if you plug a range of wind speeds in. I have brought multiple motors many times and picked one based on the prevailing conditions. Oh,yeah, I'm doing that this weekend...F53 vs G74.

It's cool that you can upgrade to dual deploy down the road.

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Hnefi said:

The thing I am worried about with the G54RL is visibility. I would be flying it with a club so lots of pairs of eyes to track, but at 1800+ ft, it starts to get difficult to see deployment and descent. Any high altitude flight is a risk of losing the rocket and hardware and it seems like from reading a lot of threads around here, 2kft is pretty much the hard ceiling for single deploy and no tracker. How would you build a nose cone ebay? Cut the shoulder, use a bulkhead, and epoxy the Firefly right onto the wood? What would you do for plugins/arming and access?

I will play it by ear on launch day, since I will be bringing a few SU 29mm loads, as well as a VMAX F load for fun. It'll be a good experience for me to "fly the field".

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ThirstyBarbarian said:

I've flown my Leviathan on F20, f27, F23, and never had a problem with it seeming under powered. I don't know the weight off the top of my head, but it is heavier than stock.

The thing I found with the single-use F42 was that the set delays were too far spread apart for my Leviathan. 4 seconds was too short, and 8 seconds too long, and nothing in between.

If the rocket is extra heavy, or winds are high, and you are worried about speed off the rail, but also don't want it to go too high, then a short-burn, high-thrust motor with low total impulse is in order. The F42 makes sense as long as the delay sims out ok, but maybe an F50 would be another option. Or if you have CTI hardware, an F59 should kick its butt off the pad in a hurry! That would be a real contrast to your other long-burn motor picks.

Jolly logic has some newer versions of the Altimeter2 out, and with people upgrading I would guess there are plenty of used older versions out there that you could pick up cheap, and shipping by a private party should be less than $25. Would you be open to a used one? The older display is not as nice, but they work fine.

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SCrocketfan said:

That sounds like a good plan, but I wouldn't say 2K is the ceiling for needing dual deploy. A few weeks ago I flew a 3" fiberglass rocket only a bit longer than the Leviathan to 3150', motor deploy. I've also flown 4" and 5.5" rockets to about 3000', and am planning a single deploy flight to 4200', albeit with a tracker. There really isn't a hard ceiling for needing dual deploy or tracking, but you want to really consider the field conditions/ launch angles and make sure you're comfortable with how far the rocket will drift under the chute.

If it's windy and there are field obstacles you may want to fly just the F's (the Vmax F is great by the way, I've flown them in my Leviathan and Argent). However, on a really calm day with a good launch angle I flew to 2900' and recovered the rocket around 150' away, so if the weather/field conditions are good definitely consider the G54.

At 1800' you can usually see tracking smoke and the parachute deploy no problem, but if you're worried, definitely see if you can get some spotters to help.

For the nose cone ebay, John Coker has an excellent tutorial video (start around 9 minutes for the ebay): https://jcrocket.com/plastic-nose-mods.shtml
Basically, the normal technique is to cut the shoulder, and use a centering ring as an anchor point for a removable sled. You would need to cut custom centering rings, but it's fairly simple. If you don't want to do that, the Jolly Logic altimeters are probably the best option.

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Hnefi said:

Did you have a tracker in the 3k flights? I haven't been out to this launch site before so I will need to inspect and fly the field and conditions when I make it there. Thanks for the advice on the Vmax motor choice.

The nose-cone ebay would be pretty hard for me since I don't have the tools to cut custom centering rings. I am thinking that for August I will go single deploy with no altimeter, and then my next project will be to get a few sections of tubing, and stretch it to fly dual deploy with a 6GXL case and a full H. It's like two rockets without having to build another kit.

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