This is the start of my new build thread. Yep, it's going to be an Atlanta. I was going to do a Sumatra/Java but BC had the Atlanta and at only 2" longer (and 1.5 pounds extra displacement), I figured go for it. This one is for my grandson Chris who had a great time at the last regional helping his GDad run the Barham and Mogador. Hilarious thing he said while I was battling the Mogador, "the little one is much more durable than your big ship!" (because it was still floating after the battle). Anyhoo, with the impending speed increase for the CL's (and those wing turrets on the Atlanta), I figure it would be a more effective backup boat and one Chris will enjoy calling his own. Hull and other bits have been ordered, pics in a week or so hopefully. Grandma is pushing to get Chris battling in 2018 so this boat will definitely be on the water in the spring!
Here's some pics! No build pics yet but the package from BC is due today. Should have some good stuff posted shortly. I've already started on the motor mounts and pump. This is the USS Juneau, second of the class. Certainly a handsome warship class if there ever was one. That sheer curve is something else. The Atlanta's certainly came in an interesting number of camo scheme's. If I had an artistic bent, I'd consider one of these. Maybe the gkid Chris might have a go at the paintbrush.
Work starts on the Atlanta! This is the BC Atlanta hull. It's a pretty nice hull. Symmetrical, a little under 1/8" thick, not to many gelcoat blemishes. Since it's a class 2 boat, BC took the liberty of turning a round bottom design into a basically flat bottom barge. This allows it to carry the extra one pound displacement allowed by IRC rules. Should also greatly help with stability. Note that the factory deck cut is rough trimmed at best. This will be addressed further down. The first task is to determine the waterline. This is done by weighting the hull down to the 9.08 pounds max hull weight and putting it into the water. Here I marked the hull center from front to back and balanced it at this point to have a rough starting point for when it goes into the water. Hull in the tub. Got to love the bathtub sized boats for this process. Here I'm measuring level fore and aft. The hull was sitting low at the bow so weight had to be moved aft to get the hull to sit level. A bag of bb's makes an excellent adjustable weight. The max weight waterline is marked. Can't go above this mark and stay legal. Now that I have the waterline marked, its time to address the sheer curve. The Atlanta has a very pronounced and distinctive sheer. As cut from the factory, the curve was nothing but. Here I've clamped a long thin aluminum piece I had laying around to mark a fair curve for the sheer line. This was done on the side that was cut lowest. This was so I could transfer the curve to the higher side without issues of the factory cut being to low. Curved marked. This gets sanded to the line. A sanding block and some very course sandpaper makes quick work of this process. To transfer the curve to the other side, I use a paper template. Here' its taped to the good curve. The curve is traced, template trimmed, and then transferred to the uncut side. Template is traced to the hull and then that side is sanded. Both sides are carefully finished sanded checking level though the process. Much nicer! At the section of lowest freeboard, I have 9/16" available. Well within the rules requirements of a minimum 1/2" I've marked the bottom window line 1 1/8" below the heavy WL mark for some wiggle room. This is going to be a stupid simple boat to sheet. That's it for today.
Next step with the Atlanta is to determine rudder position. You need to know where the rudders going before you can determine prop location. This is a BC 3.5 square inch rudder that will get trimmed down to 2.63 square inch. I'm using the same actuation setup I used in my Mogador. It works really well and I like the idea of module compatibility with other ships in my fleet. Here I'm seeing how far back the rudder servo will go and still fit under the deck. With the rudder location locked in, the props can be positioned. Here I'm starting to build a jig to hold the props and shafting where I want them. A piece of ply is glued to the hull and a paper template is used to determine shaft placement. This jig will stay in place until the motor's and stuffing tubes are bonded in place. Looks like I'm going to get decent rudder coverage. I also started with the rudder lower bearing. This consists of a 1/8" collar bonded to the hull which acts as the lower rudder shaft bearing and also one side of a mechanical seal that will keep the water (mostly) out. A 5/16" flat bottomed hole perpendicular to the waterline was carefully drilled into the thick hull. Collar JB Welded (epoxy) into the hull. The rudder shaft gear is pressed onto the top of the collar to make sure they are parallel to each other as the epoxy sets. A 1/8" brass rod mounted into the wooden block ensures alignment of the assembly while everything sets. The brass rod was greased to make sure the epoxy does not grab hold. Till tomorrow...
Today's installment... Before I went much further with the hull, the inside gets wire brushed to knock the shine off the fiberglass. This is so adhesives will stick to it better. So perusing the McMaster.com site one day, I noticed some aluminum tube stock that had an ID a few thousandth's smaller than the OD of the RS555 motors I'll be using on the Atlanta. I thought, hmm... maybe I could come up with some use for that? This ladies and gentlemen is the Tyng Tech Snaptite motor mount! The motor press fits into the mount and that pin fits into the hole in the motor case and keeps the motor from sliding or twisting. The mounts will be bedded into epoxy paste and then through bolted to the hull after the epoxy sets. The pin is long enough so the motor can be aligned to it before it's snapped into place. Instead of drilling a hole in the case (which I wanted to avoid so I didn't get metal shavings in there) I enlarged an existing hole using a tapered punch. Starting on the shaft penetrations. Started looking at systems layout. Till next time...
Are you really going to use that battery pack or did you throw it in as a placeholder? Nice work so far!
Thinking about it. Since I'm duplicating my Barham's 24v drive system in this project, I've been on the lookout for compact OTS 24v solutions. I found this at Lowe's for $18 with my veterans discount (normally $20). I know I can get 6S battery packs at HK but I'm intrigued with the idea of using power tool packs. I like the idea of commercial quality cells, bb proof case, and idiot proof charging. Only question is can 24v 2AH power the boat long enough to unload 100 rounds? Considering the uber efficiency I'm seeing with the Barham's 7AH 24v SLA packs, I think 2AH might be enough for the Atlanta.
That's a neat idea, I guess as long as you get packs that are waterproof or do that yourself you shouldn't have much issue. It might also make finding emergency replacement batteries and chargers during an event easier if that situation ever arises. 2AH @ 24V should be plenty for a cruiser from an energy standpoint, 5AH @ 6V was "standard" for a long time in a cruiser which is about 2/3 of the energy that you'll have available. (48 vs 30 watt-hours)
I've only seen one Atlanta on the water. Pat Clarke had one. It's was so hard getting to weight he was checking the difference between a copper gun mag and a plastic hose mag. The plastic was an one or two ounces lighter. He also was trimming off extra material from the gun elbows and Ts. Thinning anything he could to make weight. Maybe tech has gotten better, but watch the weight really close. I know Lou has tried a couple times to get one to work, but had so many issues getting it to be under weight. Good Luck.
I hear you. I got my Mogador under weight and I hope so too on this one. The challenge is being able to keep that 2.8oz CO2 bottle. I'm hoping I can make weight and keep the bottle because running with lighter disposable cartridges gets expensive. I also know a thing or two about building lightweight cannons.
Work continues... Stuffing tube time. Tubes are built up from 1/4" aluminum and 9/32" brass tubing. Bearings are 1/8" ID bushings. It all gets stuck together with red Loctite. All surfaces that see Loctite get roughed up with sandpaper or a file. Loctite the bushings into the brass tubes first. Assemble the stuffing tubes on your shafts. This ensure perfect alignment of the bushings as the Loctite sets (assuming your shafts are straight). If you can afford it ($10 each), I highly recommend precision 1/8" SS shafting from McMaster.com. Assembly process: slide a bushing assembly on the shaft, then the aluminum tube, and then the second bushing. Insert the bushings onto the aluminum tube just a small amount, apply Loctite to the aluminum tube on each end, then slide and twist the bushing assemblies on. Hold in place for a few seconds until the Loctite sets. Don't stress the Loctite joints to much for the first couple of hours. After 24 hours the Loctite joints will be inseparable. Top tip! You can use a 1/4" OD bushing as a gauge to help you file out the stuffing tube holes. Spend a little time on this process and you won't have to cut out monster big holes and then fill them up afterwards with a ton of Bondo. In case you didn't notice, the initial holes I punched into the hull where just large enough for the 1/8" shafts and some wiggle room while I determined motor location. Once everything is where I want it, I then carefully enlarge the holes for the stuffing tubes. Motor getting bonded into place. I'm using my trademark direct drive (no dog-bones) setup on this boat. For this to work well, you need perfect alignment of the motor, shaft, stuffing tubes, and props. This is done by bonding the entire drive train into the hull at one time. The secret is to precisely position the props where you want them (remember the prop jig?). With the prop end of the shaft fixed in place, the stuffing tube on the shaft, no binding of anything when the motor is test fit, it's time to bed the motor in epoxy paste. Here the motor mount is buttered up with epoxy and the mating area on the hull had paste smeared into it to ensure a good bond. Slip the motor onto the shaft, tighten the shaft coupling, and then press and align the motor. Once the motor is where you think it needs to be, spin the shaft and check for binding and true running. Keep spinning the shaft and adjusting the motor placement until it spins easily. Once you have it perfect, step away and let the putty harden up. I'll wait a day and then through drill the mounts and bolt them securely to the hull. FYI, epoxy putty does not stick all that well to fiberglass, so don't rely on it as your sole source of attachment. Once the motors are locked into place, time to butter up the stuffing tubes to the hull. While applying the paste, keep test spinning the shaft to make sure you don't knock anything out of alignment. Once the epoxy paste sets, you can pull the prop jig off. Strut supports will be going on next. Yeah Baby! I stuck 1.5" props on a CL! This thing is going to dig holes in the water. Till next time...
This is a well done build and set of pictures documenting it. I want to thank steve for posting this level of detail on his build.
You have to be willing to make a lot of compromises. It's a cruiser so don't reinforce the ribs. Maybe think of styrene for superstructure. Little boat is so tippy (especially with water in it), look at the version that did not have the wing turrets (to save more weight). Tim K ran his for a couple of years in the IRCWCC, but it was fragile.
Do you plan to run solenoids? The new BC style will save a lot of weight over the KIP. The BC Regulator you have is also a big weight saver over the old cut down Williams. Those are two things Pat didn't have.
Just weighed the hull with most of the bits sitting in it and it's at 6.25 pounds right now. Once it's cut that will loose some weight. If I can keep the deck and super under 2 pounds I think I'll be all right. Keeping the wing turrets, have something special in mind for those!
Haven't decided on solenoids yet. I have a couple of Chinese ones that weigh the same as the BC's. Haven't test fired them yet so who knows. Might order some Spartans which are the lightest.
Today's progress The motor mounts get bolted to the hull. Almost had a boo boo. The nuts on the forward side of the mounts are a bit close to the lower terminals on the motors. After a quick test fit, there's plenty of room to work with! Time to make some prop struts! Before cutting holes for the struts I'm checking for interference with the rudder servo. I have to move the struts forward a bit to clear the servo. Marking the strut holes. I start with three 3/32" holes and then twist the bit back and forth to clear out the slot. Struts get bent like this and then test fitted. Once I'm happy with fitment, they get JB Welded onto the shafts and hull and left to harden up. Next step is to flip the hull and epoxy the struts on the inside and trim excess material. Till next time...
