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Nodd's Airboat

Old 01-19-2013, 09:35 PM
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Nodd
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Default Nodd's Airboat

I come from an airplane background so go easy on me
So anyway I thought I'd have some fun & scratch build myself an airboat from crashed plane parts. I did some research, looked at lots of airboat designs then sat down at the computer & designed myself a boat...



Here's a collection of parts I found laying around the work shop...



    [*]no name 3536 800 kv motor (it used to haul around a 55" Piper Cub)[*]45a car ESC with reverse (might be nice to be able to backup)[*]el-cheapo servo (19g / 2.5kg / .14sec)[*]el-cheapo 6 channel receiver (way too many channels I know)[*]lipo battery (I have lots of sizes)[*]gyro (single axis)[/list]Reverse?
    This boat may see some service as a rescue boat for downed seaplanes so I want to be able to reverse to make that job easier. For the most part this boat will be used to screw around with when I'm not flying though.

    Gyro?
    Not sure she'll need this but I've been itching to use this gyro in a project. I know airboats can be pretty squirly so I may mess around with a little gyro stabilization fun.

    Anyway lets get to the build
    I printed up a set of templates from my design...



    As she's only a baby airboat, I'm using 5mm DollarTree foam-board for the majority of this build. Contact cemented the templates to the foam-board...



    A laser cutter would have been nice but I don't mind doing things old school. An hour or so of hand-cutting & we have a set of parts...



    In addition to the foam-board, I am using some lite-ply to beef up where the motor pylon will mount...



    Adding the foam-board parts...



    More progress...



    Starting to look a tad boat-like...



    Got the bulk of the bottom sheeted...



    I'm using a plastic Chinese takeout container for my radio box. It weighs almost nothing, is water proof (tested to make sure) & it has a lid that's easy to pop on/off...



    Well that's all I have time for today. I'll post more soon...

Old 01-20-2013, 03:13 AM
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Default RE: Nodd's Airboat

Nice one Nodd! 

Coming together nicely by the look of it.  The props don't work too well in reverse, and you will have no steerage, but it is possible.

Great looking build, I think most of use would like to have those drafting skills!  


6 Channels ?    Put some LED lights on it for night running!   Perhaps some servo adjustable trim tabs?

 
Old 01-20-2013, 09:01 PM
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Default RE: Nodd's Airboat

looks great.... but that is to much effort. get a hull from a mold. it will be nice and semetrical

Old 01-20-2013, 09:03 PM
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Default RE: Nodd's Airboat

ORIGINAL: Big Block Glock

looks great.... but that is to much effort. get a hull from a mold. it will be nice and semetrical
Nah, half the fun is in the build, besides it's only taken me a couple of days to get the hull built.


ORIGINAL: Altered1

Nice one Nodd!

Coming together nicely by the look of it. The props don't work too well in reverse, and you will have no steerage, but it is possible.

Great looking build, I think most of use would like to have those drafting skills!


6 Channels ? Put some LED lights on it for night running! Perhaps some servo adjustable trim tabs?
Yeah I don't expect much speed in reverse nor do I really need much, just enough to back out of trouble or help her position around a downed plane or whatnot. I'm also kinda curious what slamming her in reverse will do when she's at full speed, might make for some interesting maneuvers *evil grin*. I'm still thinking what I might do with the other four channels, lights would be nice but none of the parks or ponds around here are open at night. Trim tabs or vectored thrust, hmmm. Maybe a camera gimbal with pan & tilt? A torpedo launcher, who knows *smile*


Its been suggested (on another forum) that I install a prop guard if I'm to use this as a rescue boat. I'm pretty sure most folks don't want me chewing up their plane with my prop. I may add a guard although I'm actually thinking I'll use a floating frame rig (PVC piping with foam insulation) to do my rescuing. Something like this...



The idea being this is used only when needed, the rest of the time she's a regular airboat. The rig is made from PVC pipe & foam pipe insulation...



I'm thinking with that setup, I can probably get away without needing a prop guard, maybe *shrug*.


Back to the build
I'm learning, working with foam-board, its all about beveling...



Rough shape for the side...



Glued on, trimmed & yeap, more beveling...



These two blocks will be used to mount the motor pylon...



I chose a bolt-on system so that I can remove the motor pylon if it gets damaged or if I want to try something different on there...



A little plywood crash protection up front...



The deck...



Added some weight while the glue dries, the pillow helps evenly distribute the weight...



She's looking kinda boat-like...



7.5 oz (212 g) not sure if that's good or bad for a vessel this size. Feels pretty light to me but there's lots more to add before we're done...



That'll do for today, more tomorrow.
Old 01-21-2013, 06:32 AM
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Default RE: Nodd's Airboat

Awesome build, way to use some new materials that I havnt seen used before - I would be a little woried about the foam board flexing although it is pretty well braced. Like your radio box - put some velcro down to hold your batt. and recvr. Very cool. Looks like an .049 - 15 nitro motor might fit on there too.
Old 01-21-2013, 12:21 PM
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Default RE: Nodd's Airboat

Nice work
The building is very clean.Congratulations
What is the size of your building. length and width?
Your engine 3536 800kv seems to be very powerful, I think an engine equivalent to .32 ~ .40.
Old 01-21-2013, 06:51 PM
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The boat is a tad over 20" (50 cm), sorry I haven't measured the width.

We'll have to see how the motor performs. It did haul a fair sized Piper Cub around no problem so I'm thinking she'll move this little tub with some authority. And if not I expect I'll try bolting on a few different motors & props, see what works best.

The foam-board is far from flexible. It's actually really rigid, especially with all the internal framework. That's not to say it's without its issues, read on & see...


Build logs that go smoothly are boring
My fancy DollarTree foam-board has a paper covering. As this is a boat it's obviously gonna get wet... paper Vs water = bad. I wasn't too concerned however as I intended to fiberglass everything...



About halfway though wetting the fiberglass (brushing on the epoxy resin) I started to run low on resin. No worries, I quickly mixed up a second batch & finished her off. An hour later when I checked to see how she was looking, I noticed this big honking wrinkle...



The paper had swelled & buckled exactly where I'd stopped to mix up the second batch. Ugg! So after she'd cured I cut out the bump & laid over some fresh glass. I can't believe I'm patching the hull already LOL...



That should sand out just fine but geesh what a pain.

Wanting to avoid any new unpleasantness with the paper I removed all the paper from the top deck before glassing that. Although the foam-board gets most of its strength from the paper covering I figure it should be plenty strong with fiberglass on there instead...



So hopefully that's the last nasty surprise.

Despite the paper issue, I'm liking this foam & glass construction. Its easy to work with, nice & light & seems to be really strong & rigid. Good stuff, more tomorrow.
Old 01-22-2013, 07:21 PM
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Holes in my boat
The area where the motor pylon will mount needs to be water tight. I mixed up some epoxy & micro-balloons to cover the hardwood mounting blocks. Not wanting the epoxy to run into the bolt holes I threaded in some nylon bolts...



To insure I could get the bolts out again I coated them with some petroleum jelly (minds out of the gutter folks)...



Thankfully the jelly worked & the bolts came out no problem...



Spackling
Rather than add layer after layer of heavy, expensive resin to the fiberglass to get a nice finish, I've found that a couple of coats of watered down drywall spackling produces an awesome finish. Obviously it'll need sanding, right now you can still see the brush strokes...



Motor Pylon

I love finding stuff around the house to use in my projects. I had this old piece of U shaped aluminum that used to hold some weather stripping on the bottom of our screen door...



I cut a short length...



A few more cuts with the bandsaw...



That's starting to look a little like a motor pylon...



Used a template to get the angles right...



And there she is, a nice strong, lightweight custom motor pylon...



Tomorrow I hope to sand down the spackling & get some paint on the hull. Then I can start installing the fun stuff.
Old 01-24-2013, 09:30 PM
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Measure twice, install pylon once
Well it seems I miscalculated the distance between the motor & the prop. Here's my CAD plans Vs reality...



The actual prop sits an inch or so forward of where I figured it'd be. The unfortunate result is it hits my radio box...



Thankfully this turned out to be one of those happy accidents. I flipped the pylon around 180° & installed the motor inside the U channel for a much neater install...



It required a little surgery to the pylon, had to widen it some to fit the motor inside. I cut the old motor mount area in half then bolted in a wider piece of aluminum to mount the motor too...



So that took care of that issue. I also spent a hour sanding the spackling but I won't bore you with photos of that. More progress tomorrow.
Old 01-24-2013, 11:33 PM
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Default RE: Nodd's Airboat

Before you finalize your motor mount position, just check your balance point there Nodd with all servo's batteries and RX loaded in their positions.  A balance point about 1/3 from the rear is a good place to start.
Old 01-25-2013, 03:46 AM
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Default RE: Nodd's Airboat

Nice build! I have used Spackle as a filler for fiberglass boats, but never to cover as much as in this build. It is a dream to sand compared to most other fillers. I wonder why the OP re-designed his motor mount when ten seconds with a Dremel cutoff wheel would have moved the prop back the required 1/4".....









.
Old 01-25-2013, 04:51 PM
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Yeap I could have cut the motor shaft down a little but that wouldn't have given me enough clearance, especially as the motor pylon will probably flex forward a little under power as well as the blade tips. I think its a better setup burying the motor neatly inside the pylon anyway. I should have done it that way to begin with.

Thanks for the 1/3rd balance tip. I was wondering where ideally it should balance. Unfortunately, having buried the blind nuts inside the hull, there's no easy way to reposition the motor pylon even if I need to. Fingers crossed she balances somewhere in the ball-park. I can shift the LiPo around a little if needed as well as add ballast. I'll check it out once I get the pylon mounted.

Smooth

I sanded most of the spackling back to the fiberglass, love the way it fills in the cloth's weave. The foam-board has a slight waviness to it, so I have low spots every few inches. I slapped on more spackling in the low areas...



Once that was dry it was back to sanding...



Happy with that I sprayed on a coat of primer, looking pretty good for an el-cheapo foamy airboat...



Rudders
Well the hull is looking pretty true but at some point I'm going to want this thing to turn. So lets make my simple motor pylon more complicated...



I'm using cloroplast (corrugated plastic) for my rudders. I figure it's lightweight, waterproof & pretty crash resistant...



I drilled holes along the hinge line, cut out a notch, then slipped a wire down in there...



Sheet aluminum wraps around the wire to form a hinge...



Bolted up to the motor pylon...



That seems to be working nicely although I'll need to notch out some clearance for the bolts...



I have some ideas for anchoring the bottom of the rudders, will get to that shortly. I also need to devise a control linkage system...



We're getting somewhere now...

Old 01-26-2013, 07:41 AM
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Default RE: Nodd's Airboat

A minor point - the rudders will work a bit better if turned upside down. Having more rudder area below the motor will help to reduce tipping forces from prop blast in turns. Your original rudder design in the first post was better.



.
Old 01-26-2013, 10:23 AM
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That's an excellent point & I totally agree. I think the camera angle from my last photo gives the false impression I don't have it setup that way. Take a look at this side-view & you'll see there is actually a lot more rudder area below the motor line...



For now I want to start with a large rudders. I may trim the upper area if I find she misbehaves in turns.
Old 01-26-2013, 04:55 PM
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Paint
I was all set on a nice simple red & white color scheme until I found myself ogling the cool color choices at the paint store. So this will not be a red & white airboat. Having laid down some gloss white last night, I started masking off the graphics...



When I saw this color on the shelf I just had to use it. That's some SERIOUS green...



The motor pylon gets a slightly saner green...



Although this paint dries to the touch in less than an hour, I want to wait until tomorrow before applying any masking tape on top of it. I learned the hard way, rushing a masking job only brings grief. Hope to finish the paint tomorrow then I can get on with the assembly.
Old 01-26-2013, 06:16 PM
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While we wait for the paint to dry... I wasn't really happy with the photos I took of the pylon/rudder-hinge system. So I created this diagram that hopefully makes things a little clearer as to how that all works...



This diagram features an uncut U channel unlike mine that I hacked in half but that's how I'd do things if I'd had a wider U channel to work with.
Old 01-26-2013, 09:29 PM
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Default RE: Nodd's Airboat

Nice! This ought to hold me over til' the maiden of the sailplane, do you think you could have plans and/or a kit?
Old 01-27-2013, 06:35 PM
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Yeah assuming she floats, plans are a distinct possibility. Not sure about a kit *shrug* maybe.

Paint (continued)
Day three of painting I believe. The light green & white are done...



Moving onto the dark green...



And here she is...



The rudders got some fun stripes...



Now that's done I can get back to putting her together...

Old 01-28-2013, 08:14 PM
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Mounting the Rudders (continued)
The top of the rudders are firmly hinged just behind the motor mount. I also need to secure the rudder bottoms. For that I used a 34¢ piece of aluminum sheeting from Home Depot. I used tin-snips to cut it to shape...



This bolts-up under the main pylon. The piano-wire running down though the rudders indexes two holes in the plate...



To keep the rudders from popping out of the plate I secured the end of the wire with a couple of set-screws. Here's a view underneath before it was mounted...



To link the rudders together so they move as one I bent a short length of piano-wire to bridge the gap...



The mounting hardware is a regular set of Great Planes' control horns. I just snipped 'em off short & drilled a new hole...



And then I took everything apart
Well I thought I was done painting but noooo. For some inexplicable reason I decided she just had to have an orange nose...



Hey watch the paint job!
As with most of my airplanes I found myself taking care, while working on her, to not scratch the paint and then I thought, what the heck am I doing? This is an airboat that'll likely get beat-up running on snow, ice, grass, mud, you name it... watch the paint? So I'm adding "superior durability" polyurethane clear-coat over the entire hull, bottom especially...



That should do it for the paint... I promise. Tomorrow I hope to get the electronics installed.
Old 01-29-2013, 03:11 PM
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....
Old 02-01-2013, 08:27 PM
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Installing the guts
I dropped in my Chinese-takeout-food-container-radio-box-o-doom. Added lots of silicone to seal her in tight...



Adding bullet connectors to the motor leads...



Time to install the electronics...



I figured I'd keep things simple & just hot-glue in the rudder servo. Well that lasted all of two minutes, she popped right off. So instead I used some foam, scrap aluminum & whatnot to fabricate a proper servo mount...



Roughed up the inside of the food-container & epoxied in the servo mount. In no time I had the rest of the gear secured too. I used double-sided tape for most of the other stuff...



I spent some time programming the radio, getting the gyro setup & testing the throttle...



It floats!
The all important bathtub test. She sits pretty level with the nose raised slightly. The balance point is right around 2/3 from the bow, so she's looking good there...



DONE!
She cruises around my living-room carpet very nicely *grin* I'll take her out this weekend for some test runs. Stay tuned for the video...

Old 02-02-2013, 06:33 AM
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Default RE: Nodd's Airboat

What a cool looking little boat! I'm sure it will be a blast to run, pics/video a must.












.
Old 02-04-2013, 10:06 PM
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Well you've all been waiting for this, so here we go.


Click to watch video...
Nodd's Airboat YouTube Video
Old 02-05-2013, 07:38 AM
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Thanks a million for the video and etc!
Old 02-06-2013, 04:21 PM
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I couldn't really tell you which prop worked the best. I broke the three-blade before I got to do much testing. I will say she hauls-arse with either.

Reversing ESC Setup
Most boat or car ESC come with the reverse feature. The boat ESC are water cooled so that wasn't an option for my airboat that runs on land too. So I went with a fan-cooled car ESC. Setup is pretty simple, you hook everything up as usual with the ESC plugged into the throttle channel. The throttle channel on a reversing ESC is a little different...



So when used on an airplane radio, you have to center the throttle stick to stop. Chances are your throttle stick has no self centering so it's a bit tricky to operate. Set the "null zone" on the ESC to its max. That'll give you a fair sized area around center that'll shut the motor down. It's not ideal but it works.

I've also been asked about how the gyro was setup. Here's that info...

Gyro Setup
I'm using a Detrum GY48V gyro. It's a pretty standard unit, usually used in helicopters but it'll work in anything RC...



Setup is pretty simple, you just hook it up between your receiver & rudder servo...



A nice feature of the GY48V is the remote gain control. It comes with an extra red plug that you insert into an unused channel on your receiver. Map that channel to a switch or the rotary-knob on your transmitter & you can dial in as much or as little stabilization as you like, all while you're driving/flying.

Orientation of the gyro when you install it in the hull is important. This unit only senses a single axis so in the case of a boat you want to orient it so it can sense if the boat turns either left or right (yaw). It doesn't care about rolling from side to side (roll) or rocking back-n-forth (pitch).

This gyro has two modes...

Regular
Counters any yaw movement by turning the rudder in the opposite direction

Head-lock
Turns the rudder either way until its facing the initial direction

For a boat you probably want to use regular mode, that's what I've been using. There's lots of other gyros on the market, for the most-part they all work the same (hookup between with RX & the servo). Some have remote gain control, some don't. Either should work fine.



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