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Old Aug 24, 2014, 01:01 AM
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Go to this page 2mm drive shaft / coupler / 20mm 2 blade surface prop can be cut down to suit your needs.

http://www.horizonhobby.com/products...-9-PRB08001#t4
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Old Aug 24, 2014, 01:07 AM
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Note in 2009 I fabricated my 2mm drive shaft keyed to the 20mm prop with no coupler - drive shaft ran integrally into the outrunner grub screwed to the motor's bell housing for 0 vibrations in relation to use of a coupler.
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Old Aug 24, 2014, 01:18 AM
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At speed you are compressing air under the tub which aids in lift.
See pic note where I wanted the air compressed and where I didn't.
The balance less the 3S batteries. Water line ref.

Also note;
The pic does not show a turn fin I do have one mounted in the vids
If you want to turn equally left and right there is a (best solution) vs a more draggy way.
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Old Aug 24, 2014, 02:36 AM
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Lets have a look at those sponsons
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Old Aug 24, 2014, 04:38 AM
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Additional info per drawing
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Last edited by Amp Abuser; Aug 24, 2014 at 05:03 AM.
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Old Aug 24, 2014, 06:35 PM
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AA, thanks for all of your insight.

After taking in your suggestions, I am starting off with a simple print. It will be printed in 5 pieces to start. I went back to a simple square tub, due to buoyancy concerns, and the idea that a tapered tub might not get up on plane as well, as well as influence from your ramped tub. I also redesigned the sponsons similar to the top picture set in your sponson explanation picture. It still has the sharp outboard edge, but it has been reduced to almost flat in that area.

Being that it is my first self-designed outrigger, I decided to make it simple.

Printing consists of left and right sponsons, an outrigger arm, and two tub halves. The tub is flanged and will be permanently glued together.

The first print will not have a printed shaft guide tube, as it will only be used as a floating proof of concept. If this seems to work okay, I will then add in the small things such as, motor mount, guide tube, servo bracket, as well as possibly design a rudder for it, so I don't have to source one.

If this model seems to work fine when powered, I may consider trying the front steer as my own personal experiment.... Also, I will start working on reducing tub size currently 40mm wide) and start experimenting with tapered tubs, and more efficient hull designs....
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Old Aug 24, 2014, 06:39 PM
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Above are all clips of only half the boat. Below are clips of the full boat

Boat Length is 285mm from tip of the riggers to the aft of the tub. From outboard edge to outboard edge of the riggers it is 210mm. Tub width is 40mm external, and 38mm internal. Tub length is 220mm.

It is a bit stubby and fat, but this is an attempt to ensure proper bouyancy for what might end up as slightly heavier than a ply boat. Although, that being said, the last hull I pictured weighed in at only 28 grams complete with guide tube.
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Old Aug 24, 2014, 08:45 PM
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Note the primary ride change stuffing box location AKA drive shaft or drive line.
Your tub was too low in the water and wouldn't ride high enough for good clearance every time it touches water will up amps and drag down speed - sheets of water or multiple drops add weight on the hull and drag the lil guy down. Looks like you're getting the idea in your last post / stance is bettah.
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Old Aug 24, 2014, 09:54 PM
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Here you can see just how narrow the back end is on 5.3oz RTR.
Look at the extreme stance there is no way I'm going to let this Lil one flip out in the deep water small ones need more stability in the chop. After a few trips to the pond I put on a turn fin as it was fast enough to spin out.
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Old Aug 24, 2014, 10:03 PM
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Also after adding the turn fin I took in the sponsons an inch as you can see they are adjustable allowing you to trim the 3mm carbon tube away.
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Old Aug 24, 2014, 10:05 PM
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Much of the look from the sponson is due to perspective, and it being closer to the "camera."

Sponsons are 30mm wide at their wides, and 95mm long.

Tub height is 10mm at the lowest part just below the outrigger arms.... The arms have also been lowered slightly, for a more secure fit in the sponson. (more surface area to glue into). Ontop of this the sponsons have been angled down 3 degrees, very slightly increasing the contact area on the bottom This now means that we can not raise the bottom of the tub any more... Well, we can, it will just require putting a negative bow into the arms.... The negative with doing this is that it is much harder to get a nice clean print, and the end user's printer will have to extremely well calibrated.


The boat is definitely going to turn out a little more "stubby" than what we might be used to, I am currently accounting for the thought that it might be slightly heavier than what we would hope for, therefor sponson and tub width are similar to that of a larger 350-400ish mm rigger.

Arms and riggers are on the printer as we speak, pics soon.
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Old Aug 24, 2014, 10:10 PM
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Very nice! How much does the boat weigh without components? Also, how much do your components weigh? (RTR)
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Old Aug 24, 2014, 11:34 PM
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8 gram Outrunner on 3S Original Outrigger Hydroplane Test Vid 2.AVI (6 min 37 sec)



The tub is just a hair under 12in.
From sponson tip to transom just under 14in L x 12.75in W
From sponson tip to prop 14.75in.
From prop to trailing edge of the sponsons 11.75in.

Note in the video I say 10g outrunner after checking the motor on my own scale it was found to be lighter then stated by the manufacture.

8 gram out runner for power, all up weight 4.5oz out rigger. Custom made 20mm metal prop on Rino 20C 3S 360mah Li-poly cells . Radar confirmed 24mph with a 2009 Bushnell Velocity Gun.
No load 36,810 rpm checked with a laser tach.


Video shows internal detail. Note the motor by HK and is a 2,900 kv, uses silver winding wire for max performance.
I replaced 248 mah back into the 3S 460ma pack after the above run actual motor time 4.46 mins burning average of 55.6 mah per min. It would take 8.27 mins to run the pack to 0 mah. Watt meter shows 12.4v .92amps no load at 11.3w. Average amp draw under load was 3.34amps,that's average watt draw of 37.4w with top speeds of 24mph (must be a world record for a 8 gram outrunner motor)

Doppler WAV Audio Analysis:

Target Speed = 23.757 MPH (T=74 deg F)
Source Nominal Frequency = 1892.3697 Hz
Motor Speed = 28521.7236 RPM (loaded on prop)
36,810 rpm no load, Out runner on 3S has no water cooling nor for esc.

The thread is here I may have more info on the stats
http://www.rcgroups.com/forums/showthread.php?t=1289898
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Old Aug 24, 2014, 11:42 PM
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Yes I knew the sponson was 3D so closer still typically when sitting in the water the sponson are lift up so much they push the back down deeper in the water.
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Old Aug 24, 2014, 11:54 PM
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How much did the empty boat weigh?
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