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Old Jan 20, 2013, 12:29 AM
Nodd is offline
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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)

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.

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...

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Old Jan 20, 2013, 03:10 AM
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Looks cool.

Can't wait to see it running.
Old Jan 20, 2013, 11:07 AM
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Nice work and excellent use of the Chinese food container.
Old Jan 20, 2013, 11:52 PM
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Thanks guys.

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 Jan 21, 2013, 04:10 PM
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I like it.
Old Jan 21, 2013, 09:36 PM
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Thanks, yeah I'm liking this too. Fingers crossed she floats *grin*

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 Jan 22, 2013, 10:20 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...

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 Jan 24, 2013, 08:48 PM
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The pylon looks quite professional excellent work!
Old Jan 25, 2013, 12:27 AM
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Thanks :-)

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.
Last edited by Nodd; Jan 25, 2013 at 12:35 AM.
Old Jan 25, 2013, 10:42 AM
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Nice workaround.
Old Jan 25, 2013, 07:34 PM
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Thanks, yeah I think that works better than the way I originally had it. Love when that happens.

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...

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 Jan 26, 2013, 07:51 PM
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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 Jan 26, 2013, 08:06 PM
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Great work Nodd.

I've been thinking of building another Boogieboard air boat. Your pylon set up is very practical & simple. I might have to clone that idea if you don't mind.
Old Jan 26, 2013, 09:11 PM
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Yeah Paul be my guest, go ahead & clone away *smile*

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...

Old Jan 27, 2013, 03:30 AM
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Nodd I like the look of your rescue boat and its extremely professional and looks good.

785boats and Nodd here is our rescue boat and it works extremely well now:

The best rc recovery boat in the world (2 min 39 sec)

We used a kids bodyboard from rebel sports. We then cut out the front section to allow the boats to slot into it. Like a big U shape. We used twin 90mm EDF 36mm 1600kv edf units on the nose of the bodyboard. The edf units just sit onto of a servo with a special mounting to secure it down. We use two 60amp turnigy trackstar esc's to power the EDF's. The system runs on twin 3s 2200mah lipos. The electrics are housed in a clear plastic container that we have a hatch for and is taped down each time. We use the HK300 tx system which allows us to adjust the steering and throttle controls. Oh we also added daggar boards on the underside to allow steerage. The whole system works extremely well. It gets a little tricky when its very windy though.

Sorry I dont have any pictures of it right now. This was an old video of it. We have since moved the EDF units right up the front of the nose as far as they can go. You can see one of the motors was actually loose during this video but we have since fixed it up.

We have been through about 5 or 6 different versions of this rescue boat and this one works the best out of the lot. It has allow of power to push any boat back in.

785boats I hope this helps you out a bit when making your rescue boat.

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