I am now in possession of a NC hull, the boat I've been looking forward to working my way into since I first got into the hobby. I grew up in NC, went to school in Wilmington NC where the NC now resides, and have plenty of great memories on her. I've learned so much from all of you in my first 1.5 years and I can not wait to apply all that to my very own NC. I have no plans to start serious construction until the fall but I'll be designing her in the meantime. The design and construction of this NC will be called "Project Dogwood" after the NC state flower. I'd like to use this build thread to discuss design choices so other captains can gain knowledge along with me. Cheers to the Showboat and the Old North State! Boat Specs: * Guns will be standard NC supercruiser layout. Trip sterns and a port/stbd bow gun. Planning on Spartans all around plus accumulator tanks, and check valves on the stern trips. * Air supply - single 12oz bottle with accumulators and check valves on the sterns. * Drive - PROPDRIVE v2 3542 1000KV Brushless Outrunner Motor x2, each running on Hobbywing Quicrun-WP-10BL60 Waterproof running with a 3s battery. *Pump - The "Tustin" configuration. 10shock 906, 3D printed base, metal impellers, and I'm going to figure out how to make a tapered glug restrictor. I'm planning on running the pump on a separate set of 4s or 6s batteries.
First question for discussion, I've seen some large boats run a single large bottle (9+oz) and some use 2 smaller bottles (a 5oz and a 3.5oz), what are the pros and cons of splitting my gas system into 2 bottles?
That's my understanding as well. I have some large bottles that were slated to be used in this build. If I have the room I might use the 9oz as one of 2 bottles, I already own it so might as well use it.
It's all about temperature and flow rate. There is one good way to reduce freezing in your gas system: More thermal mass. Bigger bottles with more CO2 will carry much more thermal mass than smaller bottles, and have more surface area for heat transfer. That's a significant benefit to having a larger-than-necessary CO2 bottle, since your temperature will drop a lot less for a given amount of CO2 usage, especially for sudden large demands such as a furious sidemount exchange. Bigger bottles also have more liquid surface area, so they can boil faster and maintain pressure better under large demands. On the other hand, regulators have flow-rate limits as well. If you're demanding more CO2 than a single regulator can supply, the only solution is to use multiple bottles and multiple regulators. That said, very few ships actually exceed those flow-rate limits for long enough that you actually need two regulators. In most cases, accumulators can provide enough readily-available pressure for an exchange of fire. I am firmly of the opinion that a single bigger bottle is better unless absolutely required by the particular ship you're building. Multiple bottles and multiple regulators results in multiple failure points, multiple systems you forget to turn on, etc. Just about the only time I would actually use multiple bottles is if I don't have a single large bottle available but I do have two smaller bottles.
Why not leverage even more thermal mass? I remember reading, in these forums, that someone ( Edit: it was @BigGunJeff ) had used an aluminum heat sink to pull heat from the pond and keep the CO2 from freezing in their bottle. Could be overkill, or it could be exactly what you need : ) PS. I may have some more 9 oz bottles that aren't being used.
Speaking from experience here, two bottles is primarily used to increase the amount of gas available for use which in turn makes it easier to have crazy effective guns. Duel and triple guns run off a single bottle can be harder to get an effective tweak on all barrels without the use of accumulator tanks and check valves. Not saying it can't be done effectively but it isn't the easiest way. Two bottles give you double the amount of gas available when you start firing and also resupplies your system that much faster. A duel sidemount system with a bottle supplying each barrel of the duel has excellent gas supply and can shoot very fast for a long time, even without accumulator tanks. Same can be said in a triple stern setup. One bottle can effectively fire 3 guns powerfully, I've seen it done a lot, but if you're using the high flow guns that have become popular then it gets to be a lot trickier. @Kevin P. would be a good resource on the question of whether you need two bottles or not. I've never personally setup a triple gun turret so I can't say what works best. The duels on my Bart, however, went from being ok when powered off one bottle to being ridiculous when each gun was powered by its own bottle. So there is that. Also, the added thermal volume doesn't really eliminate freezing if you're pulling a lot of gas. I've frozen the duel bottles on my Bart many times.
I did dual bottles in Bart 2.0 for all the reasons @Beaver mentioned. I would come back every sortie with my 16oz single tank in Bart 1.0 frozen solid and was constantly fighting my regulator pissing CO2 out the vent hole because it was freezing up, even with tanks and check valves. I agree that @Kevin P. Is a good model to follow, I'd check out his Scharnhorst thread for some ideas as it's armament is mostly similar to an NC.
Excellent. All of it. I've already had ice problems in both my boats so it's good to know there is a way to help with that.
Either single bottle or two bottles would work fine. For Scharnhorst I run a 9oz for most guns, and a 3.5oz for one of the triples. The boat was having trouble keeping up pressure with 1 reg firing all 3 guns by the 3rd salvo or so with my gun design. Since this will be your first keel-up build, I would stick with KISS as much as possible to focus on simple/reliable, so using one 9oz bottle in the middle of the boat. You'll want accumulation tanks and check valves for the triples, I've gone through a few iterations and can share part numbers of my current preferred setup. I also have excess tanks/check valves that could go to a better home
I was already planning on using tanks and checks for the triples so this advice solidifies that decision. I also think I'm going to lean into KISS and go with 12oz bottle I already have. Worse case scenario is down the line I dont like it so I split the air up into 2 bottles. I would definitely appreciate the part numbers for what you are using. I will also buy those spares from you as well. I'm in no rush so I can get them from you at Nats.
RE drive motors: I've already got 2 spares of the PROPDRIVE v2 3542 1000KV Brushless Outrunner Motor from the Württemberg build (baden). 2 of those should be good for a NC no?
It depends on voltage. I use 900kv of that exact motor in mine with no issue. KV = rpm x volt. 1000kv should be fine if you're at 3s, geared.
What's a few part numbers for check valves and accumulator tanks? From my plans so far I think it'll be 1/4 OD input and 1/4 OD output but nothing is finalized. From the ships I've seen it looks like the flow is bottle >>check valve >>accumulator >>solenoid >>cannon. I'd like direct connect the CV, accumulator, and solenoid if possible, for simplicity and less fail points. But I'll entertain other designs.
I'm seeing prices from $6 to $120 between Amazon, Grainger, and McMaster. I know check valves are pricey and key components so these make me...uncertain Control Devices P2525-1WA Brass Ball Check Valve, 1/4" NPT Female x NPT Male https://a.co/d/a7kWD1m These ones from Grainger seem like a good middle ground: https://www.grainger.com/product/GRAINGER-APPROVED-Poppet-Spring-Check-Valve-4DHP6
I use clippard, the smaller one is Mcv-1, the current one is mjcv-1ab. The mjcv has female 1/8npt inlet which accepts a push to connect fitting and male 1/8npt outlet which goes directly into tank. The tank is avt-12-1, with 1/8npt female connections. Last piece is 1/8npt nipple that goes from tank to solenoid with no flow restrictions. I’m willing to part with several mcv-1’s
I have noticed you still use the 1/8 hose while others went to 1/4. But the holes in my boat are just the same haha. What's your thought process behind staying at a reduced flow with 1/8in?
I first built scharnhorst with huge accumulation tanks and big hoses to triples but had a lot of issue firing several salvos in a row. My working theory was the flow rate from the guns was too much, and the accumulation volume too large that after draining the reserve the reg was trying to fill the tanks which prevented pressure from recovering. When I swapped to modest tanks and small hose the shot consistency was much better, and they were still shooting well over 250 fps. Small hose guns can still be nasty, larger hose sounds better and works well for single guns. Other things like drilling the pistons and adding the back feed to the elbow can help too. Tight tolerance barrels that are 5” also add a good bit of velocity (bb accelerates with more force and over longer distance). Small hose is also easier to manage if solenoids are mounted in the boat. Overall many ways to put holes in other boats
