I decided to bite the bullet and go with the HobbyKing HKPilot32 instead of the Pixhawk for the reincarnation of my Skywalker FPV rig. By most accounts the HKPilot32 works as advertised and why shouldnt it? it has the same design and uses the same chips as the open source Pixhawk. Thank you open source and market forces!
Here’s the content of the packet (L to R: USB cord, Servo wire, Power Module, the HKPilo32, cables for the gps, buzzer, arming button, stickers and vibration pads, free memory card/usb adapter and extension board) and a 4MB sd card pre-installed in the device. The only major downside is it does not come with the 6-pin cable needed to connect the HKPilot to the Quanum Lea-6H GPS.
What surprised me is the size of the HKPilot. it has the same dimensions as the APM 2.6 which is great.
I’ve heard about the poor quality of the soldering and board layout of the HKPilot.. personally, for the price, I couldnt care less as long as it works reliably. Anyway, out of curiosity I checked the board.
In my opinion, the board design and layout is not bad, a bit dirty to be honest but not bad. The soldering while not topnotch seems to look solid enough at any rate.. of course I’m comparing this to the usual hardware I see (computing and networking appliance’s boards). You can judge for yourself above.
So does it work? so far yes, I was able to load the latest ArduPlane firmware and didn’t really have an issue connecting MissionPlanner (except I had to set the connection speed to 38400)
To complete the modifications (see part 1), I felt that not only should the attachments be secure but it should also not require too much effort to remove the elevator. The plastic plate that will be glued to the elevator has a plastic tab that gets ‘locked’ to the plastic plate on top of the rudder. To remove the elevator one needs to ‘lift then pull’ that piece of tab. If you ask me, its too small and requires some unnecessary effort which can damage the damned thing. Here’s what I mean:
It would have been great if they added more plastic to this tab. At any rate, the solution is straight forward, get a paperclip or metal cable tie (my preferred choice) and make a small hole near the tip of the tab like so:
And here’s the finished mod.. which can be easily accessed using whatever tool is at hand.
The updated Skywalker RC Plane 2013 1880cm version I got from FPVModel.com came with a T-Tail configuration. That is, the elevator sits on top of the rudder as opposed to being wedged at the base of the rudder. One of the things I noticed was that the locking mechanism used to connect the elevator to the top of the rudder requires some work as there is simply no way we can make the 2 plastic plate parts to lock. For this a dremel and some sanding paper is your best friend.
Here’s what I mean by the locking issue.
there is simply no way those notches will get in without breaking the plastic:
The solution to this is to dremel or sand the level section (left of the circle above) to provide space for the raised notch to slide on.
Strengthening the Tail Section
I also decided to strengthen the connection by adding the a screw which goes on top of the elevator to a washer and bolt under the plate that will be glued to the rudder.
For this you’d need a screw with a bolt and 2 washers. What worked perfectly for me is a 3.5cm screw. It just has enough length to cover the thickness of the elevator and the two connector plastic plates between the rudder and elevator.
To create the perfect fit do the following (note: this also assumes you have not glued the plates yet to the elevator and rudder):
1) Create a small hole on the lower plate. The lower plate is the plastic plate which attaches to the rudder. You’d want to make a hole just in front of the X studs of the plastic to prevent touching the wire channels (see picture below). Create a hole just enough to fit your screw. A reaming tool (or the exact sized drill bit if you’re using a dremel) is perfect for this type of job as you want to have the exact ‘fit’. Again you dont want the hole to be too big.
2) Attach the two plates together. I assume you have already dremeled or sand papered off some of the plastic for a good snug fit. After attaching, get a marking pen and mark the upper plate through the hole made in step 1. Remove the plate and make the same sized hole which is marked by the pen. I did not do this in one step as I’m using a reaming tool which has a gradually increasing diameter which is not a good idea.
3) Glue the washer and bolt. This one requires some steady hands, since we will be inserting the screw from the top, the washer and the screw must be located under the plate of the rudder. To do this, join the two plates together and insert the screw from the top (ie elevator plate) and insert the washer and bolt on the other end. Dont screw it all the way, instead just screw a bit so the washer and bolt wont fall off. Glue the washer first by using a medium fast acting glue (the 5 Minute Epoxy is perfect for this).. just put a small amount of glue on the plastic and away from the hole, just enough for the washer to be securely locked to the plastic. Slightly add pressure to the glueing process by pulling on the screw so the bolt will be pressed against the washer. Turn the screw every now and then to make sure it and the bolt are not glued in as well.
Allow the glue to set (about 30minutes), do the same to the bolt.. again just enough glue around the edges to set the bolt on top of the washer. After that has set add some a piece of plastic or plywood (in my case both) to add additional strength and secure the washer and bolt to the lower plate. Here’s how it looks like, take note of the location of the bolt relative to the studs of the lower plate. I had to dremel a bit of the plastic so the washer and bolt can fit.
4) Create ingress hole on the elevator. This requires a bit of good guesstimating.. first remove the screw and attach (without gluing) the elevator to the plates. Screw the screw from the the other side (ie from the bottom of the bottom plate where you attached the washer and bolt) and really slowly turn the screw make small adjustments to your angle to make sure it comes out centered and on top of the elevator. Once you’ve done this, remove the screw and screw it from the top and you should be able to have a good straight path right through the washer and bolt at the bottom. Here’s how it looks like:
5) Add a Base Plate on top. Finally look for some small plastic to glue on top of the rudder as the base of the screw like so:
Add a washer before inserting the screw. This mod will add a good solid connection between the rudder and elevator.
And in part 2, I added a some leverage to easily pull off the horizontal stabilizer from the rudder (see here).