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Old Nov 17, 2014, 08:47 PM
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Ready for an update?


Here she is in all her glory!

First and foremost, everything besides electronics and prop shaft are 3d printed. Secondly, I wanted to use parts I had around the house, hence the rather large motor.

Weighing in at 165g, it is a bit heafty. However if it gets on plane just fine, it should move quite well with the available 100 watts.

Future changes will include a change to the rudder and its geometry. Because of the current rudder, I did not have the necessary room to have a reasonable right deflection. Secondly, because of the rudder offset, it has a bit more travel than I would like. (when turning left, the rudder is about 2x as far away from the boat as full right). Also, I need to extend the prop shaft guide tube. The front opening currently sits level with the waterline, obviously a problem when just sitting there. That being said however, the leak it slow, and I don't see the boat sinking in any less than 7-10 minutes. Further more, by extending the rudder and providing more clearance, it will allow me to stretch out the driveline a bit more to try to get it out of the bad and turbulent water coming off the back of the tub.

Also, I plane on doing my best to lighten up the sponsons, and aft floats to help it sit just a tad higher.

With a lighter 2s setup and a smaller motor, this thing can easily weigh in at 95-110g. Keep in mind I have a 500mah 3s, 10a ESC, and 1806 multirotor motor.

Current setup is:
Maytech 1806 2300kv Motor
Turnigy plush 10a
6g servo (not necessary at all, way overweight)
2mm bicycle spoke
500mah 3s 20c battery
Orange 4ch Air RX
3D printed prop (3blade 20mm and 2blad 25mm)

As far as fit and finish goes, I am very pleased. All the major parts fit flawlessly. The sponson fit snuggly on the arms, the arms fit snuggly into the tub, the tub halves fit snuggly together, the aft floats fit snuggle and perfectly straight, rudder fits into the rudder mount, and the OD of the prop shaft guide tube fits perfectly into the tub. The small things that need adjusting were purposely printed small tot ensure a PERFECT fit. These include the prop mounting hole (which needs to be drilled perfect so that they self-tap), prop shaft guide tube (again, needs to be perfect to avoid slop), and motor mount to shaft coupler (again, needs to be drilled perfect to avoid slop.)

Ps, this is all overkill. I could drop down to a 360mah battery and save quite a bit of weight instantly (almostt 30g), I could drop from a 6g servo to a 2 or 3g servo, for an approximate 130g even. Thats all with the same motor etc! If I dropped to an 8g motor and 6a esc that would be another ~20g or so, resulting in a 110g boat, very easily.

PSS, If this planes out just fine, I will consider "heafty" boat mods which would consist of slightly wider sponsons, and slightly wider aft floats to help raise the waterline a bit. A small increase in these fields could result in a significant change...
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Old Nov 18, 2014, 12:42 AM
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Your rudder is tilted so far back it will cause lift and turning is reduced
Front turn fins are too big and will cause drag and will cause lift if the rigger is going fast enough. Prop is too close to the tub and will cause the tub to run wet ie slower. Of course none of the above matters if you don't have enough power to run fast enough to pop up on plane.

I did some doodles
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Old Dec 31, 2014, 01:21 PM
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Okay, so I have been trying to make this thing work....

Currently the boat is too heavy and sits to low. I could reduce the motor and battery size, but I am really trying to do this on the cheap! Therefore I am using what I have (24g motor, 3s 450mah battery). It can get on plane but takes over 50 feet to do so due to the extremely slow acceleration, and my prop cavitating too early.

The next change is larger aft assis floats, larger sponsons, and changed sponson geometry (the arms sit higher therefore the sponsons sit deeper in the water, the are also angled down 2 degrees after a previous change where they were up 4 degrees. This is to try to get more buoyancy with the sponsons). My biggest dilemma as of now is the simple fact that at this scale, ABS is simply not very buoyant. If it were scaled up I'm sure the current geometry would be more than fine! Im starting to realize at this weight and size, it might just have to be slightly out of proportion.

On a side note, I started designing a deep v hull due to the fact that they are naturally more buoyant, and I had a crazy thought for a dual prop drive off of one motor. The boat would be able to utilize the excessive power from my current motor spread over 2 props, and it would also have more buoyancy to float the extra weight. The drive split system would consist of either 4 printed bevel gears. This design would have an output shaft coming from the motor, through a bevel gear and to the first prop, meanwhile the bevel gear would mesh with another bevel and transition the power 90 degrees, through a connecting shaft, where it would transition back with two more bevel gears and another output shaft. The other design consideration is a centralized motor, with an output of one single gear. The single gear would mesh with two gears, one on each opposing side, driving to output shafts and props. Third option is simply a single output (which will of course be utilized for the first prototypes.)

The deep V is still deep in the design process, as I still have to figure out an easy assembly. The Outrigger is extremely easy with meshing and interlocking pieces requiring very little CA and assembly time. (Hull is assembled in about 10 minutes, built time is about an hour, print time is 2-8 hours depending on speed and quality)

Edit, these renderings are a bit old. The newest rendition has a shallower bottom for stability. In other words, if you look at the 2 chines, the lower one is much shallower to the bottom (keel?) which should help with directional stability in choppy pond or pool water.
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Old Dec 31, 2014, 03:04 PM
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Here is a question,

When dealing with a deep (or semi-deep) V hull, what is generally a better Chine design? Full length of the hull, or meeting the keep which would effectively create different speeds/planes where they would become most effective, resulting in a sort of "step" effect.
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Old Jan 03, 2015, 12:26 AM
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Okay guys! I am finally ready to release the complete Hull!! Final top speed and handling at speed have not been tested, but this thing now gets up on plane in a hurry, and has out grown its pool very quickly! Tomorrow I will do my best to find a pond or small lake and really try to get this thing going!

The entire Hull (including shaft, rudder, etc) is only about 62-67 grams, so it could very easily be a light weight rigger if you do it right.

Right now it is quite obese. weighing in at a whopping 165g ready to run, however this is mostly due to my overweight power system. The current motor is a 24g motor, tugging along a heafty 3s 460mah battery! This power system puts out a whole 120 watts, giving us ~1.4g to watt ratio!

As previously mentioned, I am currently designing for what i've got, IE an 1806-2300kv Multi-rotor motor.

I am sure with a lighter 2s version, we can reduce the sponson and aft float area. I would also like to redesign everything to have less wetted area. There are definitely many changes to come, however I believe this is the first "complete" version I am proud to release.

http://www.thingiverse.com/thing:619657

Goodluck!
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Old Jan 04, 2015, 06:20 PM
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Okay Amp abuser, and others... Couple more questions!

Got it out to a pond (more of a slough actually) and opened her up a bit! This things MOVES for sure. As it currently is, I would say right around 18-20mph.

Now the downfall. It will not plane on its own, the prop cavitates too soon, no matter how the throttle is managed. If you drop the speed too much, you must limp it back and start over with a soft toss and about 40% throttle. It stays on plane with 30-100% throttle. That isnt a major issue, and I can definitely deal with it. It would be nice if I didnt, but oh well.

Now, the major issues. The prop jumps out of the water. There is no speed diffrence from 50% throttle to 100% just more noise. Is this due to prop angle? Too large of a prop? I ran it with my 2blade 25mm prop, and didn't have time to switch it out to the 3 blade 18mm prop. This means it never really saw its true potential because more than have the time this darn thing is out of the water!

2nd Major issue is a horrible right turn. measuring from outer, aft corner of sponson, to aft corner of the tub float they are both within 1mm of each other, and the fronts to the opposing corner of the tub, are exact (in other words, straight). It takes full left rudder for it to go straight, an it will not turn right. It will however turn left Very well. Prop rotation is counter clockwise.

Any ideas to fix these issues? Are they both prop related? Does the boat naturally want to turn because of the torque from the prop? Counter clockwise prop rotation, would cause a right roll on the boat, putting more "weight" on the right sponson causing more drag, but would it have THAT much effect?)

After 7 minutes run time I ended at 3.9v per cell on a 3s 460 mah pack. I will post back when I know more about mah used.
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Old Jan 04, 2015, 07:22 PM
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After Re-thinking and re-reading a few article on outrigger design, I feel I have too much prop lift, causing the torque steer, and hop all at the same time. The boat tracks just fine when it is is not on plane.

This has caused me to think that a) the prop lifting is causing more pressure on the sponsons as it tries to "dive" them into the water, combine this with the torque diving down the right sponson, and it creates a hard turn.

The afterplane is 192mm (from the aft of the sponsons to the aft of the prop. Also the black sharpie line). The CG is 55mm aft of that line (or aft of the rear of the sponsons). This to me seems fairly far back, but the boat is saying otherwise. Also, the battery can move forward another 7mm and aft all the way to the stern.

So before I run into more flotation issues with the aft floats due to moving the CG rearward, I will swap out to my 18mm 3 blade prop to see if it naturally has less lift.

To recap on the previous post, I put 146mah back into the pack, and I actually only had 5 minutes of run time. Not bad!
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Old Jan 09, 2015, 12:39 AM
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The extreme kick back of the rudder angle causes the back end to continuously lift further out of the water the faster it goes. It also reduces turning ability and will cuase sponson lift in the turns. As mentioned before and per the drawing changes of my last post you need to have the rudder at or near 85 to 90 degs to the water line. If kicked forward beyond 90 it can cause the down pressure on the transom.
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Old Jan 09, 2015, 12:41 AM
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Also did you notice the prop attitude and distance from the transom? You will ge more bite and avoid / reduce cavitation issues on start up.
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