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Old Aug 12, 2014, 02:44 AM
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Joined Feb 2012
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Build Log
Airboat Rescue Boat

Been a while since I've been on these forums. Finally found some spare time to build a new Rescue Boat. For this project I thought I'd make an Airboat using the motor and ESC from my old rescue boat. At 41cm long it's a little larger than micro but doesn't seem to fit into race boats either.

It's a bit over engineered for a rescue boat especially as I have no idea how well it will perform - an experiment; with a view to building a larger (fast) airboat with my 2845, 2960Kv leopard motor.

In short:
- hulls are solid balsa wood which I routed a 1cm deep middle section into then built into a catamaran style flat boat,
- construction materials; balsa, marine-ply plus some carbon tube / narrow flat,
- motor is an E-Flite Park 300 1380Kv outrunner (only 28 grams),
- 12A ESC,
- in tests (on floor on Lego wheels) a 2S battery was OK but would not move on carpet, on 3S it starts motoring along nicely,
- 3S 1600mAh battery,
- all up weight should be around 700~750g by the time some paint is added,
- cowling was built from strips of balsa around a White American Oak laminate strip and then a thin layer of fibreglass to stiffen it up,
- cowling / motor mount is tilt adjustable (about 5deg down),
- APC carbon prop 4.75 x 4.5C

I was unsure if only making the rudders half height would be enough but even at 1/2 throttle they direct a pretty decent breeze towards me when sitting to one side so I hope that will work.

My biggest concern is the height of the front hull - ie: might easily dig-in on a wave / direction change and flip - any thoughts?
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Old Aug 12, 2014, 02:28 PM
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South Korea, Gyeonggi-do, Ansan-si
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Looks great! I love how it is all wood but surprised your floats are solid balsa. I thought they were hollow and well sealed to look seamless. Even solid balsa is pretty heavy.

I think the air rudders need to be much larger so they act on more of the prop wash. But testing will reveal if this is an issue or not. An auxiliary water rudder might serve well, between the pontoons, maybe rounded and spring loaded to ride over obstacles.

Keep a slight rear weight bias and the height of the front should have less of a chance at digging in. What are you going to use for the retrieval 'device'?
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Old Aug 12, 2014, 08:12 PM
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rescueboat

Looking good.
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Last edited by Dennis Manning; Aug 26, 2014 at 09:17 AM.
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Old Aug 13, 2014, 05:17 AM
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Joined Feb 2012
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Thanks for your feedback Harquebus. The 'slab' of solid balsa I just had lying around (for like 20 years) so I thought why not use it. Normally I would make proper hollow hulls.

I thought about a water rudder but will see how it performs first plus I like the thought of having nothing to get caught up in floating debris.

I previously just pushed the rescued boat back in so intend to try that again.

Dennis, do you mean angle the flat vertical sides from top down (see attached photo-edit). The rake is currently about 90mm (3.5"). Would not be too hard at this stage to sand that back further - I assume this is what you are describing. The hull is already quite wide at 224mm.

Plans for finish are to seal the inside with water-based furniture estapol (it's waterproof when dry). Outside, once I finish the top deck, 2 to 3 coats of spray auto sanding primer then automotive spray paint over that.

Hopefully I'll get it in the water this time next week.
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Old Aug 13, 2014, 08:25 AM
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rescue

Nice job.
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Last edited by Dennis Manning; Aug 26, 2014 at 09:17 AM.
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Old Aug 16, 2014, 07:46 AM
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Israel, Haifa
Joined Mar 2014
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Quote:
Originally Posted by Rhizome View Post
Been a while since I've been on these forums. Finally found some spare time to build a new Rescue Boat. For this project I thought I'd make an Airboat using the motor and ESC from my old rescue boat. At 41cm long it's a little larger than micro but doesn't seem to fit into race boats either.
...

My biggest concern is the height of the front hull - ie: might easily dig-in on a wave / direction change and flip - any thoughts?
I don't have much experience of boat-building (small models with kids counts?), so I'm curious: how are you going to water-proof electric components?
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Old Aug 16, 2014, 08:47 AM
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rescue

Water proof with Corrosion-X. esc, servo, receiver. Where to purchase it in your part of world, is a big ?.
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Old Aug 16, 2014, 03:11 PM
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Israel, Haifa
Joined Mar 2014
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Quote:
Originally Posted by Dennis Manning View Post
Water proof with Corrosion-X. esc, servo, receiver. Where to purchase it in your part of world, is a big ?.
OK, thanks. With help of google I see this is kind of protective spray that you apply on electronics. Am I right?
What I don't get is how well it protect battery connector - as it has to be connected/disconnected every time.

My plan was to make some kind of waterproof compartment for battery-ECS-RX.
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Old Aug 16, 2014, 08:53 PM
RcBoater
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009

I have never seen a posting on that subject in all my years.
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Last edited by Dennis Manning; Aug 26, 2014 at 09:18 AM.
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Old Aug 19, 2014, 03:24 AM
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Joined Feb 2012
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Maiden Voyage / Strange Turning Handling

Finally got the Airboat in the water today. It sits pretty well and goes quite well (if you keep it straight) however turning is very tricky. Dennis, you are correct - it handles like a barge. Once in a turn it just seems to keep going like it's on curved train tracks and you need to let it slow almost to a stop before trying to change direction. I smoothed out the front hulls and put some angle on the sides but I think with the combination of straight sides and the catamaran channel it just results in strange behaviour.

I will now put a large radius on the corners in the tunnel and cut / sand the outer of each hull to a smooth radius down their entire length.

Hi Xlib17,

I think your questions about waterproofing have been answered. As the motors are brushless I think they will even work underwater (to some degree). With the ESC I have sealed both ends with silicone. With my other boat, the expensive receiver is wrapped in a section of plastic bicycle inner tube and sealed both ends with waterproof tape.
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Old Aug 19, 2014, 05:44 AM
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Photos from today + Hull Re-Shape

A few photos of the boat in the water today and photos after re-shaping the hull this evening.
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Old Aug 19, 2014, 08:35 AM
RcBoater
Joined Feb 2014
251 Posts
rescue

I hate to say any more as it is a beautiful airboat in the water.
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Last edited by Dennis Manning; Aug 26, 2014 at 09:19 AM.
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Old Aug 19, 2014, 01:50 PM
RcBoater
Joined Feb 2014
251 Posts
rescueboat

Electric Airboat RC --youtube HumblebeeRC owner............ I envy this airboat.
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Old Aug 20, 2014, 01:59 AM
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Israel, Haifa
Joined Mar 2014
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Quote:
Originally Posted by Rhizome View Post
Hi Xlib17,

I think your questions about waterproofing have been answered. As the motors are brushless I think they will even work underwater (to some degree). With the ESC I have sealed both ends with silicone. With my other boat, the expensive receiver is wrapped in a section of plastic bicycle inner tube and sealed both ends with waterproof tape.
Yea, thanks for advise, I will totally try that. Indeed, brushless motors are quite waterproof by themselves, and ESC/RX have no moving parts so can be sealed one way or another. The last concern I have is about servo (have moving parts) and battery connector.
I must note that I'm talking about sea water, which to my understanding is harder to protect from.
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Old Aug 20, 2014, 05:33 AM
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Joined Feb 2012
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Video of 2nd Test Run

Handling is much better after the major surgery on the hull shape.

Video of my test run today (sits for 5 seconds at start):
RC Airboat Rescue Boat - Test Run (0 min 50 sec)


A bit more fine tuning to do and with a nice smooth layer of auto spray paint, I will have myself a fun little rescue boat. Seems very efficient too. I ran it for at least 10 minutes and only took 370ma to top up the battery.
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