Since there was some interest in the '50s Shovelnose kit (the Short Circuit), I've started to populate 4 boxes with labels and parts. Still waiting on Mike to cut the prototype parts.....
Who wants to build a semi-scale all-wood micro hydro?
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Bill,
What others are on the horizon for getting cut?"A quick temper will make a fool of you soon enough."
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OK, here's what I have:
#1 The Atlas. Kits are ready to ship.
#2 The Short Circuit. Kits are being populated with parts, but I need to build a prototype first before any laser cutting. Complete kit with everything except receiver and battery.
#3 The 16" Cat. Short kit with just the framework, no skins. I've built a single-motor prototype and have a twin-motor prototype under construction. I've changed the twin design to use built-in (fixed) stingers. I haven't written instructions or any supporting documentation. No real plans to issue a kit, but if there was interest, I will. I'll go back and revive the thread on that one.
#4 I'm in the preliminary stages of drawing up a 442mm outrigger loosely based on the KEPS mini rigger with minimum weight as a primary goal. It will have a more "airfoil-shaped" tub with a really "low profile" (1/2" high) transom, 1/16 balsa sides with 1/64 ply skins on all four sides. The sponsons will be laser-hollowed balsa with 1/64 ply skins (sides only to save weight and complexity of building). The kit would include all the wood and carbon fiber bits plus a laser cut 0.050 aluminum turn fin blank and threaded aluminum inserts that go in the sponsons to mount the turn fin. The builder would have to sharpen and bend the turn fin. This hull can use either my 1/32 wire drive or 0.098" cable. I'm thinking the prototype will use the 1/32" wire drive and this rather small motor to save weight: https://www.ebay.com/itm/RCS-Model-K...8/302621329359. The hull will fit bigger motors like the 11-Series NeuMotors (might need some support), but I think the aforementioned little outrunner would make a fun "spec" class and keep weight to an absolute minimum. Fast, Cheap, and Out of Control.I'm also thinking of using this motor: https://www.ebay.com/itm/4000KV-Brus...0AAOSwbYZXcejx. It's lower on Kv and 19grams heavier, BUT....... It's cheaper, it has a built-in cooling fan (a good thing), a larger diameter (more torque) and with more torque you can always spin a bigger prop/higher pitch to compensate for the lower Kv. Besides, I have a couple of them on hand.
Last edited by Dr. Jet; 03-09-2019, 12:20 AM.A nation of sheep breeds a government of wolvesComment
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#4 If you make it 449mm long, and get it light enough you would have a ready market for them in the Naviga Mini Hydro class racers, as that calls for a hull with a maximum of 450mm and the closer to that limit you are the better the performance in typical race water. I have raced the JAE mini and against Keps Minis but they have been outclassed by lighter molded boats for years, the only wooden rigger that I think is competitive is the RBC Fast4ward, but I have not actually seen one run myself.
It would need to have enough space to fit in a 3s zippy 25c compact 2200mah battery and an energy limiter (about the size of a small RX), and have the battery space near the CoG so it can run with a 113g battery or a 170g battery and limiter.
I have run some balsa sponsons in the past, and skinned sides aren't really needed, but a skin on the bottom surface is needed if you want them to last longer than a test session.
Saving weight is good, I think you have to be under 390g +battery to be competitive in the class, if you stretch it closer to 450mm and get it under that weight I will buy one of you for sure. There is a minimum weight limit of 450g RTR, but that is 280-337g + battery and I doubt you can get down that far with a sealed and painted wooden boat.
The second motor looks good to me, we typically use motors with 60-70g of mass, the KV is higher than I would choose, but not at all unheard of, and if designed well and built light will work well with 1.2 ish pitch props from Dr Props or Tenshock.Paul Upton-Taylor, Greased Weasel Racing.Comment
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Remember, my plan was to run 2S. I like the helicopter outrunners in the small boats for a couple of reasons. They have built-in fan cooling, and they have an order of magnitude more torque than an inrunner of the same size which means a bigger prop or more pitch.A nation of sheep breeds a government of wolvesComment
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I looked at the RBC Fast4ward. It reminds me of the old adage regarding aircraft origins (see photos): If it's ugly, it's British. If it's weird, it's French. If it's ugly AND weird, it's Russian....
What I have planned will look much more sexy and should be lighter than the Fast4ward. Instead of a strut with beefy mounting brackets. I'm using a fixed stinger. I had planned on a brass stinger with ball bearings, but could just as easily use aluminum to save a gram or two. The 1/32" wire drive I like is a whole lot lighter than 0.098" cable, but I'd need to do a lot of testing to see if it would hold up to 3S over time. It works just fine with 2S boats, but I haven't used it for 3S. 1/16" wire should work as well, but I think in these small boats puts a lot of radial loads on the system. As long as the motor and propshaft use decent ball bearings, it should be OK. If I were building it to race in a timed event, I would use one of Steve's motors as I think they are the most efficient ones on the market.
I have to finish up the Short Circuit build/kits before I get too far into this, but I have stretched it to 449mm and the limiter can fit on top of the ESC, balancing out the larger battery which sits up against the aft sponson boom and is ALMOST on the CG.A nation of sheep breeds a government of wolvesComment
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I'm going to start a new thread on the outrigger project that has taken over this conversation, as it really doesn't belong in a thread titled: "Who wants to build a semi-scale....."
That said, I do have an idea for the next in the series of 1:20 semi-scale hydros.Like the Short Circuit, this one will be another from "The Golden Era". I've been compiling data for another 1958 Unlimited which should be a whole lot of fun and easy to build. Obviously, I have to finish the other projects first, but I do have things brewing in the background. Much depends on whether or not any real interest develops with the issuance of the first two kits though....
Last edited by Dr. Jet; 03-11-2019, 02:34 PM.A nation of sheep breeds a government of wolvesComment
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Mrrrffff mmmmmrrrrfffmmm
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Well, it's a start.....Attached FilesA nation of sheep breeds a government of wolvesComment
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Well, I picked up the parts from Mike the laser guy #2. His machine doesn't do nearly as good a job as Jesse the laser guy #1's machine. Oh well, it's a prototype, and the price was right.......
Stay tuned for the process and know that the kits will use the better machine.A nation of sheep breeds a government of wolvesComment
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I've assembled the preliminary framework and found one or two structural and dimensional issues that have now been resolved on the drawings. That's why I always like to build prototypes first. The cutting files for the kits are finally ready to send to the laser guy. I'm going to hold off on that until I have everything else needed though.A nation of sheep breeds a government of wolvesComment
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1:20 RR Merlin DLP printed
Earlier in this thread, I showed a photo of FLA 3D printed Merlin and Allison engines. FLA printing leaves a lot to be desired in the resulting surface finish. DLP printing yields a MUCH finer resolution. Here's what I'm working on having printed at 1:20 scale that will open up a whole lot of possibilities with the 1:20 scale hulls.
I talked with my production laser guy and he's going to be on vacation until the first of April. There's just a couple of parts still "in the mail" so there's a good chance the Short Circuit kits should be ready to go by April 15th. I can't finish the prototype before that because laser guy #2 supplied 1/64 ply instead of the spec'd 1/32 ply for the sponson bottomsand that just won't work. It's too flimsy.
Attached FilesLast edited by Dr. Jet; 03-15-2019, 08:56 PM.A nation of sheep breeds a government of wolvesComment
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The cowl came out pretty good. It's made from "pancake stacked" 1/4 balsa without the headrest. It gets sanded to shape, then the headrest pieces are glued to the fin and sanded to shape. The fin/headrest assembly is then glued to the cowl and the joint filled in with spackle/putty.
NOTE: The prototype uses a 2-piece bottom because laser guy #2 didn't have 6" wide wood. Production kits will be one piece.A nation of sheep breeds a government of wolvesComment
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The boats using the Short Circuit hull were for the most part, powered by the Allison V-1710, but DLP printing opens up a whole new world in 1:20 scale. This motor came out a bit small at about 1:23 scale, so the detail in a 1:20 will be better.A nation of sheep breeds a government of wolvesComment
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