A fighting chance for submarines

Bob, I have one question. Why the ballast tanks? All the Big Gun submarines I've seen in combat were dynamic divers, limited to a scale speed of 25 knots on the surface. Fast Gun speeds are greater, so you shouldn't have any problem diving, even from scale waterline. If removing the ballast tanks isn't enough, then I don't know what else to do.

I gotta say, though, if even a famous boat-builder like Bob can't successfully build a combat submarine, then there's something wrong. They're supposed to be challenging, not impossible.

 

Dynamic diving subs share a common characteristic. Unless they're barely positively buoyant (and all subs real or model are very unstable in that state) a dynamic diver has to increase speed to submerge and stay under. That was the case for a 1/72 sub I built many years ago. In R/C combat the diving/submerged speed can't exceed max. allowed speed, so on the surface the sub will have to run below it's allowed speed.
A speed controller is needed, taking up more of the very limited volume. I suppose you could get a dynamic diver to work without one if greatly oversized diving planes were used.
My I-400 was a static diver due to the speed issue and also because if threatened it could submerge and sit on the bottom until the coast was clear. If not clear it was tying up an enemy ship. The scale size dive planes were in dive position. It was hoped they'd help the model dive with the ballast tanks partly flooded, but testing didn't get that far due to the stability problem.
The best the model could do in limited trial runs (3) was submerge and surface using ballast tnaks and CO2, fire the specially designed BB cannon after surfacing, and move along the bottom if there were no obstructions. On the surface it would roll at least 45 degrees and stay there unless there was a flat calm and no sharp turns were attempted.
Bob

 

I was talking with Jay Jennings tonight re the I-400 hull project. Jay, Stephen Hill and I will be working on it and a friend of Jay's will do some CAD plans that will vary according to how much deeper than scale we make the model. I deepened the Battlers Connection hull at least 3/8" (maybe 1/2" - I forget) but that didn't give enough depth for stability.
Jay is a submariner and pointed out problems with relative heights of centers of buoyancy and gravity in real subs and models. We think we need to deepen the hull plans by at least 3/4" and maybe 1" to get the CoG far enough below the CoB for the model to be stable on the surface. Is there anything in the Treaty rules that would prevent this?
Bob

 

The submarines I have seen control their diving planes. To dive, the front planes go down and the back planes go up. To surface, the front planes go up and the back planes go down. This allows you to run at full speed both on the surface and below it.
On the subject of adding depth: I don't know if Treaty rules prohibit it, but if that's what it takes to make subs possible then that's what you'll have to do. If nothing else it'll give you more displacement for ballast lead. Just make sure you don't whack your submarine with the ugly stick when you stretch it. I have seen a few ships that were turned into sins against shipdom by a botched attempt to add depth.

 

Kotori,
A friend of Jay's has put the plans on a CAD program. He should be able to play around with the shape for any degree of hull deepening so the hull won't be ugly. The part seen above the surface will be of scale appearance. I think making the hull 3/4" deeper than scale (3/8" deeper than mine) will be enough for stability.
Bob

 

Bob
I am not sure that there is anything in the rules package that would stipulate that you couldn't add extra hull height to the sub.
I think that how much extra hull volume that is needed in order to make the subs workable will depend on which sub one decides to build.
3/4" might be enough for a Surcouf, or I-400. But would that be enough for the smaller boats that pretty much every other navy utilized? I am not sure.
If it were me. I think I would probably try the 3/4" for the larger subs, but I am, pretty sure that it will still be pretty near impossible to build the smaller boats and make them work if we limit them to the same 3/4".
On the other hand. We are talking about a difference of 1/4". So one might be better off to start out with the 1" margin, to increase the chances of success with the prototype boat in order to get one on the water, and gain some actual working knowledge from the build.
Mikey

 

MIkey,
Jay, Steve and I are getting together with the CAD guy tomorrow to play around with the plans. We can try 1" and see what it looks like. It would be better to go too deep than too shallow and have to make a second mold.
Bob

 

The submarines that Kotori and I have seen have enlarged diving planes in addition to extra depth. "Submarine dive planes may be twice the area shown on their plans," according to the WWCC rulebook. Their speed is 45 seconds (25 knots: minimum warship speed), although I'm told they used to go 37.5 seconds (30 knots) before I joined the club.

 

Bob, have you considered mounting the cannon in the hull rather then in the sail/conning tower? If the tip of the barrel was located in the bow, it should lower the center of gravity some.

 

Mike,
We discussed that on Sunday when four of us got together to assess my I-400 model and review a better set of plans. There is just enough room to mount one of my custom built cannons in the bow if the base of the interrupter mechanism and attached CO2 hoses are within the hull (i.e. on the innner side of the bow compartment hatch).
That will allow the slow moving and turning sub a better chance to find a target but there will constantly be water entering the gun. My 'sub' guns are designed to fire after being immersed but unless a stainless steel interrupter pin is used it will corrode and jam after a few battles - replacemnt won't be difficult. A potential problem is that a bow gun will be of little use in conditions other than calm water and/or very close range because it will be only 3/8" above the water.
Dave, Steve, Jay and I revised the I-400 plans to make a hull 1 1/4" deeper than scale but with scale appearance above the waterline. The OOP Battlers hull I bought was 1/2" deeper than scale before I deepened it a further 3/8" for a total of 7/8" .
We think 1 1/4" will be enough for a stable model with changes in lead ballast location (inside an enlarged box keel) and with extra ballast in a brass square section 'tube' attached below the hull if necessary. A different type of battery will be used to further lower the CoG and increase running time. Hull volume will be significantly greater than in the BC hull which was much too narrow from amidships forward.
Steve and Dave are to cut out the hull cross-sections and profile by next week. Jay and I will assemble them and start hull plugs for the upper and lower hull sections, which will join at the waterline. We have to finish the plugs within 3 weeks, giving me a week to make the molds in the basement while Kim is away working in Germany (thus avoiding complaints about the smell!).
This I-400 hull will have enough volume to be built as a dynamic or static diver. It could also be built as a surface running convoy ship or combatant, having more displacement than some CLs.
We discussed potetial tactics and scenarios and decided one or more subs would be ideal for base defence in an IRCWCC 'Campaign Lite' game. The subs would submerge next to the shore base, perpendicular to where battleships stop and line up to shoot at the magnetic targets. When the battleships arrive the subs will surface (using CO2 to blow the ballst tanks as in my model) open fire and dive again if threatened. This counters their disadvantages of slow speed, limited running time and poor maneuverability.
Bob

 

Greg,
Weight isn't a big problem with these cannons. Whenever File Manager returns I'll post photos of them.
It was impossible to fit a 1.5 or even a 1.0 unit cannon inside the I-400's hangar - I think the longest mag that would fit held about 30-35 BBs. I reduced it to 25 BBs due to stability problems and the need to trim weight anywhere I could. The sub was stable at rest with a 25 BB mag.
I also designed and built 1.5 unit spurt guns of the same size that could fire 3 or 5 BBs per shot. A 1 unit spurt cannon has 15 BBs under IRCWCC rules and a 1/2 unit spurt gun has 10 BBs, giving a total of 25. The mag rises at a shallow angle aft of the breech and barrel (which are in-line with the mag. The reason is to allow water to drain out the barrel after resurfacing. This limits placement options. It was fine in the hangar but the mag's slope needs to be shallower if the BB cannon is to be installed at the bow under the upper hull.
Bob

 

The guns have a 5" long barrel but there is no upfeed tube. The magazines very in length with type of cannon. The breech and magazine are on opposite ends of a T fitting with the interrupter pin in the lower arm. The pin is tapered almost to a point with a 1/16" hole drilled vertically through it to allow CO2 to enter the gun.
The breech is designed so the contact point between 2 BBs is over the center of the interrupter pin. When the gun is fired the pin is driven up between the BBs that will be fired (1+) and the rest of them in the magazine. The length of the breech chamber can be built to accomodate one or more BBs . If 1 BB, the gun is single shot. I've built spurt guns that fire 3 and 5 BBs per shot and another that fires everything in the magazine at once. That one is just a breech with the barrel on one side and the mag on the other. No problems fitting that one in restricted spaces but you get only one shot!
Bob

 

Bob
I cut the frams out and I'll call Dave to get the keel line and she will be ready for you

 

Bob, is there any chance you could post photos of your current submarine, including internals? I have a fiberglass I-400 that I'll be building in a year or two, and I'd like to see how you did your system.

 

Steve,
The hull sections and 'keel' have to be cut in two along the waterline, but not just that. An extra 1/8" has to be be accurately trimmed off each piece where they were cut because they will be assembled on two1/8" thick pieces of basswood, one for the upper and one for the lower hull plugs.
Bob

 

Kotori,
I'll post photos of my I-400 when File Manager reappears. I see the Photo section remains blank too. My attempt to post a video of the I-400's static diving trial (2003?) was unsuccessful.
Bob

 

Our team of 4 NABS/NATCF members is working on the hull plugs for the upper and lower I-400 hull sections. The hull proper will be about 5/8" deeper than the OOP battlers I-400 and the box keel will be wider and deeper so lead ballast can be glassed into it at the lowest point in the hull. The new hull will have significantly more volume as the Battlers hull was too narrow from amidships to bow and shallower.
The build thread is on the NATCF forum and Warship Builds.
Bob

 

All
Dan asked about using pull-down motors on subs instead of ballast tanks
a while back.
I had planned to use a ballast tank system on our sub as it seemed more historically accurate. But I have been thinking about the pull-down motor as of late. And I think it would probably be easier to install. And I also think it might just work.
Any thoughts on this?
Mikey