I guess quite a lot of Mayhemers are like me, using a patch of water currently clogged with weed. The only real answer (apart from some major aquatic gardening) is an airboat. The Hobbyking Swamp Dawg is a favourite at my club, but is prone to some fairly random manoeuvres, as are quite a lot of airboats of the classic shape. I have built an airboat which actually steers much more like a conventional boat, which is something of a boon on restricted or busy waters. You might say this takes away half the fun, as skidding sideways and pirouetting suddenly is part of the airboat scene, but if you are after a slightly less frantic session, read on.
The main difference in my boat is that the sides are sloped in at 45 degrees. This leads to heeling as you go into a turn and a more predictable course. The boat looks like this –
There are no real plans, other than the doodles I did before I built it, so any measurements that follow are just taken from the boat as built and none are critical. The hull is 18” long, 8” wide and 2” deep. The construction is a simple egg box with three identical frames (one being the transom) and two longitudinal members. One frame is 6.5” forward of the transom, the other 12.5” forward. Here is a cross section of the hull.
And here is a picture of the hull after the bottom and side panels had been added from 1/16” ply. I probably overdid the thickness of the ply for the skeleton, but that was what I had to hand at the time.
You can see I have added material to the tops of the side panels to give the deck something to seat on. The pylon for the motor is a piece of ˝” balsa, shaped to something like an aerofoil over most of its length, and with some pieces added to build it up where the motor attaches. There is also a plywood disc glued to the front to give the motor mount screws something to bite on. If you build this, you may have to adapt this to fit the motor you choose. Here is a closer view of the bottom of the pylon – I was keen to make sure it was braced firmly as all the thrust is transmitted through this join. You can also see the piece of brass tube at the transom which is the pivot for the rudder, cut down flush once the deck had been fitted.
I coated the inside of the hull with epoxy, which also helped reinforce all the joins. Here’s a couple more pictures –
Once completed, I added the propulsion and steering bits. The motor is one of
these, and the propeller one of
these. They seem to do the job just fine, using a 3s LiPo. Here is a view of the moving bits –
And here is the internal view. The 1300 mAh LiPo sits nicely next to the pylon in the stern compartment. The fact that it is off centre doesn’t seem to make any difference.
The cover for the electronics can be any shape you want, but mine is a streamlined shape, hinged at the front with some tape and held down at the back with a small magnet.
The shroud for the prop is the container from some Frogtape masking tape with the bottom cut out of it, which coincidentally was a perfect fit for this prop. For different sizes of props you might want to look at plastic flower pot rims.
And finally, I planed the edge of the hull down to a small flat to let me stick some of
this around the edge – slightly less vulnerable than the sharp wood edge that comes with joining two sheets at 45 degrees.
Well, that’s it. A fairly simple build, and as you can see from the pictures, mine has had some pretty hard use. But it’s great fun, and when winter comes, it works great on ice!
Greg
Author
Topic: Simple airboat with predictable steering (Read 5099 times)