Rescue boat build, springer pusher with underwater fpv and recovery

[CornelP]

This is turning out to be an interesting build... I made about 5 springers in different sizes (from standard to 5" long) and they are quite fun to drive. Just one recommendation: this hull does not like high rpm. 20000 on 50mm will make it jump out of the water, better go for the brushed motor or make sure you have a good quality ESC with low rpm control. Most of the Seaking/Hobbywing/Turnigy marine will be ok, the T180 in your pics should be perfect.
One more thing: I would try to use the Kort nozzle shaft for cooling. If you can change the shaft for a decent thickness tube, get it out in the kort a couple of mm and cut it at 45deg, you will get an excellent cooling.

[Cooper]

Thanks, I understand what you recommend. Turning the rudder shaft into the water pick up is an excellent idea. I will have to oversize the shaft, but everything will work. I was going to attach silicone tubeing to the top of the kort, that is what the intake in the rudder is for. But your idea seams better. Will have to think about the design. As far as the rpm's, I do want it to run pretty fast. Want to be able to get out to the rescue quick. And we run the fe boats on a river. Current isn't a problem with running but if a boat quits it floats away pretty easily. And I always end up flipping at the farest point down stream so I get a good workout unintentionally in the kayak. I want to have fun and be lazy while retrieving a disabled boat. I do have a Novak speedo for crawling, I can use that for brushed or brushless. I forget what the amp rating is its the Novak goat. I just thought 20k would be a good starting point, I can lower voltage or kv motor. I just want to make sure she has the punch to get out fast and power to push a 40" flipped cat hull upstream.

[CornelP]

Anyway, a springer at full speed is always nice to see. The video below is my 5" springer on brushless power...

[Fluid]

Another motor idea is to use a cheap 40mm or 50m diameter outrunner designed for airplanes (low Kv down to ~250). This gives lots of torque and low amp draw, a race boat motor is not a good idea even at low voltage since that reduces torque proportionately. We installed a 580 Kv motor in our club rescue craft and on 2S2P/5000mAh it spins a 50mm prop with ease at low amp draw - uses about 10% pack capacity for each long retrieval. As stated, an ESC with good low-end control is essential. Aim for 4000-6,000 rpm with an Octura 1250 or 1255 plastic prop and you'll be a lot happier.


4250-580_t.jpg.................... oc1250pl_md.jpg

[Cooper]

Thanks for the info, that was the only thing I couldn't find info on. Didn't know what rpm range to be targeted. Sounds like the crawler esc and a lower kv out runner. I would like to target this for 3s voltage. That's what I have the most of in larger mah capicaty

[CornelP]

For props, take a look here, at the 3 or 4 blade Raboesch, down the page, these will push the tug a bit better:

http://www.loyalhannadockyard.com/RABOESCHPROPS.htm

[Cooper]

There is a 4 blade prop that will work great! Cheep too!!! Thanks. After all the research I found my estimate was that a 50 mm prop would be big enough as I'm using a kort. Does that sound about right? It's 30% bigger than a standard springervv

[Cooper]

Oops. Cheap and springer is 30% bigger than the standard plans

[CornelP]

50mm in a kort will be enough. There is also a prop bt Raboesch (A type, 4 blade, 149-09), designed for Kort, but Loyalhanna does not have it:

http://www.cornwallmodelboats.co.uk/acatalog/R149-05.html#aRAB149_2d12

[Cooper]

Installed the waterproof lip. This will get weatherstripping foam on top. Then the superstructure is going to have a cam and lockplate as a hold down.


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[Cooper]

And finished the knees. If that is what they are called. Although I may redesign these, I'm not sure they will look right with my revised idea of the superstructure. And the Southampton is what I'm basing my design off. Might not look like when I'm done but just a guide.


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[Cooper]

Getting the base of the superstructure


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[dana]

This is cool

[Cooper]

Trying to make everything square. A little bit of time and effort getting everything square pays off in the end.
And added several supports. Not for structural strength but for support and construction guide.


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[Cooper]

Thanks, wait till I get into the first person underwater viewing camera! And the automatic location buoy launcher installed.


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