I've been looking around for a good hull to use as the model warship equivalent of a truck gun. It's loaded. It's ready. It's stashed in the back seat and never gets taken out, rarely gets oiled, and almost never gets cleaned. Something that is stupid reliable but still gets the job done. Strike Models was the only retailer that had an Invincible hull, and when they shut down they took the mold with them. So when I had the opportunity to buy an I boat as it's lovingly referred to, I couldn't pass it up. This hull is a strike models Invincible, not to be confused with Indefatigable which is slightly longer. The purchase came with the subdeck installed, decks cut out and ready, some rudder shafts and stuffing tubes installed, and baggies of hardware including some BC props and old resin Swampy/Strike rudders. The superstructure is mostly there, minus some parts, and as a bonus 4 BC cannons were included. Score. Should be a fun and easy build. The plan is a KISS build. Truck gun. The kind of boat that will be driven hard and absolutely put away wet and won't mind. (Its an expression, I'm obviously going to at least dry the boat out.) Main power will be 1 of my standard battery, a Zippy 3S1p 11.1v 8AH lipo pack. Drive is going to be direct 550's to the 1.5" BC props that came with the hull. Hobbywing 1060 ESC. Damage control is an old style blue base BC pump with a Mabuchi 12v 550 can. Right now it has a 14v Marine Titan on it, but when it burns out I'll swap them. I also have some 3d printed pump designs to trial. I like having the ability to throttle my pumps, so a second Hobbywing 1060 will power the pump motor. Since the BC board has a pump switch built in, there will be built in redundancy for pump control. Firepower is 3 1 unit cannons in the traditional I boat arrangement: Bow sidemount, Stern Sidemount, Wing turret stern gun. Fire control will be BC Multiboard into BC Solenoids. 5oz bottle, BC regulator. The BC cannons I got with the boat will be modified with large tube feeds and that's it, no fanciness. I didn't waste any time when I got home and already ripped out the installed shafts. Since it's direct drive with BC props, 1/8" stainless shafts would be ideal and that's also what is in Dunkerque and Suffren and Suffren V2 so I have the material laying around. Some quick shafts were made up, some 1/8" aluminum flat bar was heated and bent into beefy shaft struts, and the assemblies were CA tacked into the hull so I can fiberglass it without them moving all over the place. 3d printed some easy motor mounts courtesy of @rcengr 's files here on the forum.
Small update. Spent most of today working on 3d printed chain sprockets. My 3D Printed Suffren hull requires special small diameter chain sprockets to be compatible with the .25 pitch servo city chain, and servo city does not make anything small enough by a longshot. In fact, most of their sprockets are designed more for power transmission and not steering/etc. Basically, they're crazy overbuilt for our needs. So I made up some sprockets that get wheel collars glued into them (or servo arms for the servo side) for use in PlastiBote and Invincible since her existing rudder shafts are pretty close to the ship's sides. Also mounted some simple 3d printed motor mounts. Pics just show them CA tacked into place, they are now firmly part of the hull via West Systems. Drive is using the (in)famous Dumas dogbones, but I'm not too worried about reliability. Most issues I've seen were with set screws coming loose, not dogbone failure though it does happen. The operating angles are very low so the nylon dogbones should hold up just fine. If not, I will re-evaluate. Maybe get some nice steel ones.
I don't normally build brushed motor boats. I had thought that this was the more traditional method. Is there any specific reason why I would want to run gear boxes instead of just letting the radio end points get the boat on speed? I like the idea of only needing about 30 or 40% forward so that way I have good stopping power. On my brushless boats I run gearboxes simply due to the motor RPM. Even with 1.5:1 reduction my Courbet is at 9% to make speed.
Brushed motors have poor torque at starting speeds, gearboxes give the shaft a mechanical advantage that gets it up to speed fast. Brushless drive is less dependant because of the huge torque produced at starting speeds.
Also anything that allows the motor to work less will help on battery use and amp draw going from full forward to full reverse. I actually have 2 brushed motors geared a single shaft in my Scharnhorst. Has a monster prop on it too. Works really well.
I went back and ripped out the motor mounts and made two villain gearboxes fit. Epoxy is drying now. No pictures, but I'm sure you can figure it out. I wasn't far enough along to not be able to re-do it. After talking to @Kevin P. on facebook and you guys chiming in here, seems like Gearbox was the way to go. Edit: Can you brushed motor masters chime in on what sort of gear ratio I should start with? 26 second boat, 1.5" props. I have gears on hand for 2.5:1.
I see people are still giving 80's vintage advice on brushed installations. Dump the gearboxes and double the voltage. https://rcwarshipcombat.com/threads/so-you-want-to-run-24v.445617/#post-525147
I don't want to run that much battery. I'm already doubling the voltage compared to 6v boats. Good to see you back, by the way. Hope you hang around
Some of the veterans (Don?) were good at building "geek" guns - they had to be built just right to fire good, but then did not even have a nut or method to tweek them. I never got mine to work, but I was trying to adapt to parts available in Statesboro (I should have just ordered the exact hose and orings (ID, material, etc) as the vets who had them working. But even the standard cannons are pretty easy, just loosen the tweak between events to not compress the orings and don't leave bb's in magazines.
I'm just happy to see this thing get built. I bought it before I joined the Navy, and never had the time to work on it.
Yeah not playing around with cannons, the boat came with BC guns and I'm just going to use them. I buy the O rings in 500 qty so if I forget to loosen a gun for storage, I won't cry too much. Waiting on some featherlight from Smooth-On for the water channel. Will update once I'm past that step.
Waiting on funding, so working on what I can until that is secured. Waterproofed the wood and added 3/8" strips under the upper deck V, it previously was just hanging there in space. Now it is filled and secured. Built a mount for the rudder servo out of scraps of 3/8" plywood, built mounts for the guns using more of the same. The strike models turrets are not the most durable things in the world. Was happy the boat came with turrets and SS, but I dropped a turret from workbench height and it shattered on the concrete. How is this supposed to take BB fire? Going to take one of the intact turrets to make a mold for rubber turrets using Alumilite. Mounted test switches and made an access hatch for them. Mounted the guns, should be able to reload without removing the deck which is kinda nice. Of course, deck has to come off to fill bottle, but let me have my moment here. Not sure about the stern gun. Will probably make it a straight shot off the stern vs the way it is now. The current setup is very similar to my Bart stern gun which I learned to use decently well, I figured it would translate over. Easy enough to move it if I want to. Deck tiedowns are simple window screen latches. I've done magnets, I've done posts with knurled brass nuts, etc. I am going to give this method a whirl on this boat for simplicity and for how well this method can secure the deck hatch down onto a seal. Need to get more of them, would like at least 2 more on the middle deck hatch. The stern deck had a decent little warp to it, hence the 5 all just on that deck.
I'm curious how tall the strike I-boat hull is from the flat bottom to the top of the main deck? The plans I'm working from don't seem to have much depth.
Thanks for answering that, my I-boat is buried in the garage and I was looking at last night trying to figure out how to get to it to measure it up.
I now have an infinite number of Invincible hulls: This one was in the 3d print design queue for a while. I started it after I finished Von Der Tann, as they are considered the two best starter boats in the hobby. My hope is to have it finished, printed, and tested + ready for distribution in the next few weeks. Need to wrap up the superstructure. I am hoping to offer it, complete with: Full superstructure + turrets and barbettes CNC cut decks Full 3d printed hardware kit (props, drag discs, rudders, rudder drive equipment, electronics epoxy potting trays, + misc extras) Based off of the pricing formula I use for any other 3d print, the total cost for a hull-only kit would be $100 + shipping. For hull, decks, superstructure, and 3d printed hardware kit I am estimating the cost should be about $175 but that greatly depends on the price of 1/8 aircraft grade plywood at the time.
