FastGun DKM Bismarck

This ship’s hull was built in the early ‘80s by D.W. Fluegel, it was resurrected in ~2004 by Tim Beckett. I got it from Tim in 2009, as part of that deal I asked him to convert it to 1/44th scale as it was originally built in 1/150th scale. I outfitted the hull over the winter and battled it in 2010, with rather poor results. I missed the 2011 battling season due to being out of the country however when I got back it underwent an extensive overhaul in the winter/spring/summer of 2012 and hasn’t received any major changes since then. The most significant change is switching it from a flexible 7 or 6.5 unit boat to a 6.5 unit boat after Rob and I convinced the IRCWCC allies that it really doesn’t need 7 units to be effective.

Currently it is in need of a somewhat major overhaul due to heavy use over the past 2 years while I didn’t have an adequate workspace for significant upkeep. The majority of those uses over the last two years were just pulling it off the shelf, charging batteries, and heading to battle. That said it has held up remarkably well. I’m planning on taking a number of the major systems apart and reworking/rebuilding/replacing them as necessary over the next year or so.

Still, the boat is better than the idiot they let drive it.



Underside of the hull showing some of the original wiring and cutout for the Freon tanks/plumbing system from the “good old days”. You can also see some of the 1/150th to 1/144th conversion extension at the bow.




Fwd and Aft Views, note there is significant battle damage / wear & tear topside. It’s still a smexy boat.

Gun layout is the traditional two 1 unit bow sidemounts, 1.5 unit stern sidemount, and dual 1 unit sterns. With current IRCWCC rules this probably isn’t the most effective setup, however it is a good setup and packs a punch.



The main superstructure is one piece and comes off to allow access to the majority of the internals. Due to the ribs in this boat being VERY thick (1” to 1.5” or more) there is significantly less useable internal space than most Bismarcks have, but it’s still a big ship with a lot of space.



The CO2 bottle (7oz) sits in the bow, there is a cradle that the regulator fits into and holds the front of the bottle up at a slight angle, the bottom of the bottle rests between the bow expansion tanks. I like the push connect swivel fittings and the “hard” ¼” hose, they’ve been in since 2010 without any issues. The regulator is one of the old Strike Models adjustable regulators that they don’t sell anymore. I think it is the best regulator I’ve used. I’m not sure what I’d go with currently if I was starting from scratch, none of the options I’ve seen have really impressed me.



Better shot of the cradle that holds the neck of the bottle/regulator. More importantly this photo also shows the epoxy putty mod to the ¼ turn SmartParts valve (another out of production part), I did this to be able to get a better grip on it when my hands are wet/cold and I’m in a hurry, it’s a great (and simple) mod if you have a valve that needs turning.



Removing the CO2 bottle we can see into the water channel. Notice the rear earth magnet at the front of the channel, there is another aft near the pump, these do a great job of collecting BBs keeping them away from pump screens and making them easier to return to their rightful owner. The KIPS are the standard KIP solenoids that have been being used in the hobby for a long time, some of the ones in this boat are 10+ years old and still work great. (They are 6V but I run them at 4S LiFe ~13.2V, they don’t care.) There are three of them from back when IRCWCC had the Bismarck at 7 units and I ran dual bow sidemounts on the port side. CO2 comes in the black hose at the top right, enters the top (port) expansion tank, flows through the copper pipe that connects the two tanks as well as helps support/cradle the CO2 bottle to the lower tank and then exits and flows to the aft gun systems through the black hose in the bottom left. Also in this picture are the firing boards, these are some of the first ones I built, covered in ScotchKote they tend to just sit in the water channel, like honey badger, they don’t care. At the far left you can see part of the lead weight added for ballast, this could be re-arranged and re-located to improve the ship handling if desired.



Here we are sitting where the CO2 Bottle would sit looking aft, the only reason I’m including this photo is to show the remote receiver. It is the block of epoxy (circled in red) attached to the underside of the deck. (West System Epoxy used throughout, its good stuff) While 2.4Ghz radios are great for a lot of reasons they don’t penetrate water very well at all so I installed the remote receiver on the underside of the deck to help ensure I don’t lose control even if the main receiver loses signal due to being under water.



Here we can just barely see the main receiver sitting in its block of epoxy on the bottom of the hull in the top center of the photo. (It’s been there since 2010, and hasn’t seemed to mind). The piece of wood with the 6 white buttons and 2 black buttons is the test control circuit for the solenoids/guns. Each solenoid has its own test button and the two original sets of duals each have a black button which fires them together. The black chunk in the bottom center is the RX battery, I still run a separate RX battery, old habit from the 75Mhz days and wanting to reduce interference. Running a standalone BEC is probably preferable, maybe I’ll look into upgrading that…



The main batteries (4s LiFePO4, ~13.2V, 20AH) are relatively common. They work pretty well but aren’t really that great for this boat or how we use them. They can only source 2C (40A) continuous (they are sold as 10C but if you read the spec that’s for <30 sec) which is leaves less margin than I’d like. Also 20AH is crazy large for this boat. A typical full day of battle (2 battles, each 2 sorties) takes 9-11 AH, less at smaller events where the sorties are shorter. I’d much rather have two sets of 4S 10AH batteries that could do say 5C+ continuous. There are options out there if I ever decide it’s worth the money. Sitting on the top (port) battery is the data logger, I’ve had this in the boat since the 2012 refit so I have a rather sizeable amount of performance data in terms of voltage/current draw, throttle, motor RPM. The data is great, I’ve learned a bit about the boat and it’s helped diagnose a few problems that I doubt I would have figured out anywhere near as quick, if at all, without it.



Moving aft we run into the main big wiring mess in the boat, all the main/large current power wires are in this photo, messy but compact. The two chunks of epoxy attached to the cross member on the right of the photo are the main positive and negative buses. I use brass bolts, brass nuts, and eye connectors to assemble and attach all the power lines, it has worked great for me and since I don’t really ever mess with the power distribution having them set in epoxy isn’t an issue. For the wiring it is all high strand count silicone jacketed wire, 12GA for drive and pump, 20GA for solenoids.



Moving some of the mess out of the way allows you to see the aft magnet in the bottom of the water channel. Also the aft CO2 expansion tanks setup, which is very similar to the forward set, the line from the front comes into the bottom (starboard) tank which is connected to the port tank with a short piece of copper pipe. The aft port tank also has a bleed valve for draining pressure from the system. Like the forward tanks these have small brass tabs solders to them that screw into plywood blocks epoxied into the hull. Outboard of the two tanks you can see the custom lead weights, more lead shot mixed with epoxy. These were done in plastic ziplock bags and shoved in place outboard of the expansion tanks. When cured the plastic was removed, the custom fit is such that no dedicated hold downs or attachments are needed to keep them solidly in place no matter the orientation of the boat. (I routinely flip it upside down to let water/bbs drain.) There are 3 more KIPs here, the third is hiding under the positive bus at the top of the photo, same as the ones in the forward section. You can also see the pump hold down, just a simple piece of waterproofed plywood with some holes that fits over a couple of studs tightened down with some nuts, it keeps the pump from moving around. (I used stainless steel hardware here.)

 

Speaking of the pump here is the underside/screen made from speaker grille. Remember to clean your screens! Actually I need to add more screening, this is the minimum amount you should probably have and I tend to need to clean it more often than I’d like. The pump itself is one of Carl’s brushless pumps with a 1860kv motor. The screws and screen obviously aren’t stainless steel, I have an AL screen but really this small amount of rust over the past few years isn’t a big deal.



While we’re on the subject of pumps, this is the pump’s ESC, it is the HobbyKing SS Series 50-60A ESC in a block of epoxy. Nothing too special, but it works great. In the pump testing I was doing these ESCs really can handle ~50A, once you get in the 50-60A (or more) range they overheat pretty quick, however as soon as they’ve cooled down they come right back online and continue to function.



Continuing aft you can see the pump outlet and tube as well as the drive motor. The outboard shafts could be made functional and do offer significant performance benefits but I haven’t been that driven yet. (driven, get it? Haha….anyway….) The motor mount/gearbox is hogged out of a big chunk of AL, good times… Its overkill but it does a great job, a piece of angle AL could be used instead. The gears are 32 pitch, I like them for the beefier teeth than the 48 pitch gears. I originally used a plastic gear on the prop shaft but the brushless motor has too much torque and routinely would snap plastic teeth off whenever the prop hit something that wasn’t water. (ie a stick, mud, rock, whatever) This was rather annoying and resulted in going dead in the water at least once. So they gears are metal on metal, which is a bit louder but very strong and reliable. (I’ve gone “off-roading” more than once and the whole drive train has held up great.) The gearbox looks filthy from greasing the gears, they like it but since I don’t use the top of the gearbox grease does get all over this area. There is another lead weight in the bottom, it had a twin on the other side of the drive motor which recently got removed to make more room for the pump outlet hose. The hose that runs across the photo and connects to the tube next to the prop shaft tube is the old water cooling system for the main (brushed) drive motor, the propeller sucks water through. I could cap it off but I like having it as part of the history of this hull.



Close-up of the motor mount and gearbox/gears. The purple grease is marine grease, not grape flavored grease…. A ¼ turn or so on the two nuts is enough to loosen everything up and slide the motor mount plate free from the gearbox. Quick and Easy.



Motor removed from the gearbox with the motor mount plate still attached. Turnigy 4258-400. As part of the 2012 refit I switched to brushless, that’s a story in and of itself but brushless far out preformed any brushed setup I tried and has been a solid performer ever since. I find it to be very reliable vs the brushed setups I’ve used.



Drive motor ESC, another HobbyKing ESC. I opened up the case and filled the internal space with epoxy and then sealed it back up. I’ve come to think that isn’t the best way to waterproof the ESC (thermal expansion/stress on SMD components concerns), my current method is to not even open it and just put the whole thing in a hunk of epoxy. Then again this one hasn’t died yet so it can’t be that bad of a method. This got installed during 2013 NATS, when the original ESC died, however the original was damaged on its first use in 2012 due to a rushed waterproofing job so I was surprised it managed to last as long as it did.



ESC Power switch, replaced with jumper. Much better than a switch, just don’t lose it. (note to self: make spare(s))



The rudder box, once upon a time it was waterproof, I never even really tried to keep/make it water proof. The servo is a TowerHobbies TS-59 which is my favorite rudder servo, its low profile so it fits in sterns easier. I waterproof rudder servo’s myself, it isn’t very hard to do, coat the circuit board with ScotchKote and fill the Pot with di-electric grease. The last one I had die was because the brushes in the motor wore out, the rest of it worked fine. I’ve come back with this box completely full of water (before I added drain holes to the box), servo working happy as can be.



Aft view of the rudders / propellers. The Prop is a PropShop Kort style prop 2.4” brazed onto a stainless steel propshaft. (I think the shaft is 5/32”) The rudders are custom built for this boat for the correct size / shape / fit. They are covered in a thin layer of carbon fiber mat, just because.



Side view of the props and rudders. Note the drag disks ahead of the outboard props (old dumas cast props) which could be used for better reverse as I mentioned earlier. The clearance between the leading edge of the rudders and the prop blades is very tight, I used the blades of the propeller to “cut” the front of the rudders until there was enough clearance for them to spin without touching.



This shot shows both the schilling profile of the rudders as well as their neutral position with a slight flare.



The flare allows the rudders to do this at max throw. This captures the vast majority of the flow produced by the propeller and redirects it out the side, forward velocity is trashed but this boat can spin. With a little practice on the stick you can still get good turns while maintaining some forward speed by not going full over on the rudders.



Side view of the aft gun deck, there are two stern gun, they are just lined up well in this photo. The stern sidemount is on this side due to how the ship reverses on one prop. I can reverse and bring this gun in on target, with 20deg down angle the effective range is pretty small but it is a super fun gun to use when you get it on target.



Another shot of the aft gun decks, this shows the mounting for the stern sidemount, that brass tab is soldered to the upfeed tube, the magazines have similar soldered tabs that are screwed in place. All the guns in this boat are a relatively simple design, they might not be “SUPER GUNS” but they shoot holes in balsa just fine.



This is the forward gun deck, the A turret gun has a bent barrel currently. The barrels are tight SS but they aren’t the strongest and they do bend from time to time if they take the brunt of a ram. I try not to have them stick out over the edge of the boat but it still happens. The guns themselves are mounted secure enough that they don’t tend to be ripped out of place, so throw on a new barrel and back in action. Or just use a bent barrel for the rest of the event, they fire fine, sure they’ll wear out faster and have some impact on performance but it typically isn’t enough to take that gun out of action. Also I originally painted the magazine caps day-glow orange, it’s mostly worn off now and I should re-paint them. It helps a lot when you drop the cap in the grass 30 sec before battle or even just trying to remember where you put it on the workbench.



Underside of the fwd gun deck, this has some good views of the mounting tabs on the magazines. The epoxy putty on the disconnect is there to get a better grip and allow me to twist those connections apart easier with wet hands.



Internal armor. I use sheet polycarbonate, I think this is 0.030” thick, screwed to the ribs. A 2’x2’ piece is ~$10 and is enough to do multiple boats. I think it looks a lot better than shower pan liner (which also works well), also shower pan liner is a lot heavier which might matter in a small boat. Don’t use the plastic canvas stuff they sell at arts and crafts stores for sewing, it might stop your BBs but it won’t stop their BBs. A lot of people seem to like it and it is super cheap but it just isn’t good enough to protect against a quality set of guns.

 

No boat is complete without a radio to control it. This started life as a standard DX6i which I think is a great radio. I know there are a lot of other options on the market recently that are a lot cheaper and I’d bet that a number of those work well too. I replaced the batteries that are sold with it with some higher capacity cells. A little epoxy putty on the left stick makes driving more comfortable on my thumb. One or two of the shoulder switches have been replaced due to failures but that is all pretty easy. It is currently sporting the 3rd version of my shot counter which is a DX6i specific version (v4 is more universal). I’ve been using a shot counter since 2010, it seems kind of silly until you use it and get used to it, I love it. Knowing how much ammo you have and where lets you engage targets more effectively and adjust your tactics accordingly. Technically it doesn’t actually count shots but as long as your gun is setup correctly and you’re only shooting one BB for each button push it is dead on accurate. The buttons are C&K 8121SHCGE buttons with C&K752702000 caps, I highly recommend them they are well worth the cost.



Standard ½” wrench with slight modification, I use it for adjusting the nut with tweaking my guns. It’s pretty handy especially if there isn’t much room around the nut like one some sets of duals. I think I stole this idea from Rob A, but it could have been someone else.



Lube! Everything is better with a little lube right? From left to right we have dielectric grease, “hobby oil”, and marine grease. Not pictured is Air gun/tool oil for the regulator. Dielectric grease is great for the Pots in servos and on connectors. The hobby oil is for the ball bearings in the brushless motors, they will still rust and wear out but this slows that down. Some of the bearings you can find replacements for, or even ceramic sets that won’t rust. The lower bearing in my pump was replaced with a bronze bushing years ago, I haven’t seen any ill effects from that. The marine grease is for the gears as I mentioned earlier, also for the stuffing tubes if I have to pull a shaft.



NOALOX, a little squirt in all the connectors every now and again keeps them in good shape and prevents corrosion. Carl turned me onto this goodness.



Connectors. On the left are 3 Pin Deans, this is what I use on all my servo connections, the right has standard servo connectors. I’ve found the 3 Pin Deans to be more robust and corrode less than standard servo connectors, it does take some time to replace the connections in the boat but I typically make my own servo extensions and whatnot anyway so it isn’t that big an issue. The major problem with the 3 pin deans is that they aren’t always available and will go for long stretches (6 months, maybe more) where they just aren’t available, I guess they only do a few small production runs a year, so if you go that route stock up and plan ahead. Mini 2 Pin Deans are pretty easy to get and I use those for my solenoid connections. For power wiring I prefer PowerPoles to Deans, they both work. There are also some newer connector styles which probably work just fine too, it mostly comes down to personal preference. One thing that I would recommend is to build some adapters for anything that isn’t popular in your area, that way at an event if you need to borrow or loan out gear finding the right connector isn’t a big deal.

Spare Parts are also part of my battle kit, having a servo/motor/esc/etc wired up and waterproofed ready to drop in makes any mechanical failures that you do have sting a lot less, even if your pants are wet.

Most importantly get out there and battle!

 

Nicely done tour

 

Thanks guys. I've gotten a lot of help and tips from people over the years, just trying to help continue the cycle.

 

Man, this is fantastic, Lots of great stuff Here! Thanks for taking the time to post it. Where can i get the digital counter and how is it wired? If you have time in the future would love to follow how you did that.
Craig

 

The idea to put something on the tank valve to make it easier to turn I stole from "thegeek", he drilled a hole through the knob on his valve and put a pin through it to get a lever arm. I just didn't want to bother with drilling a hole and I had the epoxy putty sitting around.


The shot counter is my own design, it's been through a number of iterations in an effort to make it viable for the hobby as a whole, there are a few guys in the northeast that have been using them for a while and feedback has been positive. I've got it to what I think is a rather "universal" state (as much as something can be universal with how many different radios exist). If you're interested buying one send me a PM. The wiring for it is pretty simple, just soldering a few wires together and connecting whatever buttons you're going to use, it's easier than doing a traditional button swap since you dont have to worry about getting the resistors the correct values in the correct locations and all that jazz.

 

Great walk through! Very impressive.

 

there's my Bismarck
Nikki

 

All the pics are no more...

 

What is the benefit of the flare on the rudders? Is just so they dont hit each other and stop in the right spot?

 

Two parts. First, The "fishtail" shape of each rudder helps the ship turn as though the rudder was further over without stalling. Full-size ships sometimes have fancy articulated rudders that provide similar benefits, but the fishtail shape is mechanically simpler and works just as well.
Second, with side-by-side rudders, flaring them outwards (when they have identical travel) means that the inner rudder ends up further over than the outer rudder. Like the fishtail shape, this helps the rudder act like it's further over without stalling.

 

Does the fish tail work on single rudders?

 

Yes it does I have a fishtail rudder on my Rivadavia and it turns very well.

 

I wouldn't worry about stalling rudders on our ships. The flow hitting them coming right off the prop isn't exactly clean. Using rudders for thrust vectoring produces much more effective results. Dual rudders that can close off behind a single prop are pretty good at that. Single rudder ships can be made to do it some but dual rudders just have a big advantage.

 

What size of brushless motor are you using in that beast for drive and pump?

 

The drive motor is a Turnigy 4258-400

The pump motor is a Hobby King/Turnigy/not 100% sure of the brand, H2218-1860kv

I doubt either of those are still available but if you get something similar you should be fine.