The Towel

Progess and musings on the construction of the Brooklyn Aerodrome-designed Towel flying wing.

This is all quite out of date. I haven't flown my towel in some time as I can't find a big enough field.


New site?

While walking back from dropping the kids at school I saw a couple of RC airplanes over the rooftops, flying near Rice Stadium. Turns out there are a couple of guys who fly there every now and then - I'll have to get my airplane fixed up after the move (no idea where the tail fins are) and try it out. Although the parking lot is quite solid and I have no landing gear...

Flying!

The wind finally died down enough at an appropriate time for me to get in some flying yesterday morning using my newly designed motor mount, which didn't work very well.

In the never-ending quest for a better motor mount (because I can't find aluminum right-angle stock) I came up with a quick-and-dirty design using two smaller zinc right angle brackets from Lowe's. Because of the form factor, I was only able to mount the motor using two mounting holes, which proved to be woefully insufficient after a handful of flights. For reference, here it is:

Motor Mount 2

The zip ties loosened up after half dozen crashes and the motor flopped around a lot, completely nullifying any trim in the system whatsoever. I do have a one-piece larger right-angle bracket that I'm going to try next. It's heavier, though, so we'll see what happens. And WOW the motor gets WARM.

It *did* fly, however. I had also previously placed a big gob of play-doh in a plastic bag on the nose in an effort to move the CG forward to 10" from the nose. This turned out to be unnecessary - it turned out the weight of the play doh was doing more harm than good.

I also realized that you really need to give the plane a good throw to get it airborne, even at full power, and preferably at about a 45 degree angle to give it some altitude.

Long, slow banks were also difficult to achieve - either I just didn't have enough back pressure on the stick or real rudders would help out. Or I'm just a crappy pilot.

And the previous advice on learning on a BIG field - big means BIG. Like bigger than a baseball diamond, for example.

Weather

This is getting annoying. Whenever I have time to fly, it's either really windy or raining cats and dogs.

First Flight

OK, the motor mount didn't perform as well as I'd hoped:

First Flight Motor Mount


I did get 4 or 5 flights out of it before the prop broke. It was very responsive, at least to me. My son had the longest and flashiest flight on record with the plane shooting straight up, doing a couple of "elevon rolls", and then plunging straight down.

I have a new motor mount put together from some galvanized right angle brackets from Lowe's. I attempted a brief test flight in the back yard, succeeding only in putting two small slices in my thumb - the propeller end is really quite sharp.

Since then it's basically been raining almost every day, or seemingly whenever I have time to fly.

Sooner or later I'll get it flying again - it's ready to go...

The Build

Finally, time to put stuff together. First, the motor mount - looks like the Minty Motor Mount will work for now:

DSC 0001 - Mounted Motor


Next the rest of the components were mounted, and I test-ran the motor:

DSC 0004 - Motor running

The airframe is constructed from foamcore. I got a trifold foamcore piece designed to be used as a presentation backboard - a large center piece with two fold-out pieces. This had the largest single direction dimension I could find that reached 42". I then proceeded to screw it up and cut the elevons incorrectly, so it is actually an inch or so narrower than it should be. We'll see how that goes.

DSC 0008 - Elevons

I had some trouble measuring where to properly cut the prop hole. I found the most straightforward method was to just put the deck on the airframe where it should be, then draw the hole, then cut it out. 

DSC 0011 - Cut prop hole

One thing that is really important when attaching the elevons is placing the hinge on the bottom side of the airframe. If you don't do this (like I did the first time), when the coroplast control horns are attached, the elevons will not rotate up properly. In the photo above, I've removed the deck and flipped the airframe over to the correct side. I patched all the holes in the foamcore with packing tape.

 It should look like this:

DSC 0012 - Fixed elevons

The rest of the build was pretty straightforward. My center of gravity is back pretty far, even with the battery placed all the way forward, so I grabbed a big hunk of play doh, stuffed it in a plastic bag (I figure if it dries out it'll loose enough mass to make a difference), and taped it on.

I worked as hard as I could to make this plane look as nasty as possible - I left the stickers on the foamcore, and I used baby puke colored packing tape for the joins. My goal for the next airframe is to make it look better, but I figured there was no point in spending a lot of time making it look good when I'm pretty sure this airframe will be trashed in fairly short order.

Next up - first flight! But today it's blowing almost Force 5 or so outside. Not great for a first flight.

DSC 0016 - Completed

Parts, Motor Mount, Servos

Parts! Parts have arrived! I reviewed my parts inventory with the video recently put up on Brooklyn Aerodrome's site for the MakerShed kit available soon. Looks like mine match more or less, except the motor mount, which I will have to figure out.

Parts

For the motor mount, I started the build using the design from an earlier towel video that used the coroplast deck folded over. Unfortunately this didn't fit the motor mounting bracket:

Bad motor mount fit

I didn't have any right angle aluminum stock as described in the Make article, but I did have an altoids tin and some tin snips:

Altoids mount

After taping it up with duct tape, marking and drilling, it came out like this:

Drilled mount

It should be at least as strong as the coroplast mount, but probably not as strong as an extruded aluminum mount. We shall see. Anyway, on to mounting the servos:

Mounted left servo
Mounted right servo

One of these days I'm going to have to find out how to arrange pictures side-by-side in Sandvox. Sandvox is like a lot of WYSIWYG apps - easy to put simple stuff together but once you want to go outside of its box just a little, it starts to get pissy. There's probably a way to do it, but one thing at a time.

Arrivals

Connectors arrived (for E-Flite battery to speed controller). Motor, speed controller, and matching props should arrive tomorrow. That should be all the parts - hopefully we'll start putting it together this weekend.

Practice makes perfect...

While waiting for parts to arrive we've been taking the Make article to heart using RC AirSim to practice crashing. We'll see how useful it is once we get the airplane put together.

Motor availability

Just heard back from Aerocraft - they were nice enough to let me know it would be 10 days to 2 weeks for the motor and controller to come in from overseas. Professional of them to be up-front about it and I'll definitely use them later as they are local (more or less) and have a decent selection of stuff. So for the moment I'm waiting for the motor from BP Hobbies. A little unsure about the ESC on that one because it only has a 1A BEC - they say for 4 servos you need a bigger BEC. I'll only have 2 servos but I'd like to power an Arduino off it as well (not sure if that will even work).

Lots to learn!

Motor/ESC

I've been waiting to hear back concerning my motor/speed controller. I placed the order on 4/25 and no word on availability or ship date.

Patience is not a strong point with me lately so I just ordered a 2212-10, 3 APC 10x4.7 propellers, and an 18A ESC from BP Hobbies. Worst case is I wind up with 2 motors - maybe I'll wind up with two planes. It sounds like plenty of things get broken when flying Towels so in the long run, spare parts are probably a good thing. Besides, my friend Michael seemed mighty interested while reading the Make article this past weekend. Maybe he could use the spare motor (if it shows up).