Buzzard Bombshell Electric Conversion and Mods

About a year and a half ago I picked up this wonderful high wing balsa old timer at a swap meet.  I did not know what it was but I'm a sucker for an inexpensive balsa old timer, especially a three channel high wing.  He wanted $25.  I offered $15.  He threw in a motor, esc, and two servos and we settled for the $25 he was asking!  I was a happy camper.

After some time and a bunch of Internet searching, I finally discovered that what I had bought was a plane called the Buzzard Bombshell.  The original design was done and built by Joe Konefes in 1940  with about a 72 inch wing span.  It was intended as a free flight as RC gear was way too expensive for most people.  This plane was designed to head up as high as so many ounces of fuel would take it and then glide for as long as possible (Joe flew his for over 49 minutes at the 1940 NATS).  To help with extended glide times they incorporated large tail surfaces that helped with lift and moved the CG to 50% or more back from the leading edge.  With the heavy motors of the time, this made for an interesting stubby nose look.

Mine was a more current and smaller version that was intended for 1/2A power sources.  It looks like it was setup for a Cox .049 judging from the mounting holes in the firewall.  Now by smaller I mean about a 45 inch wing span and still a good size plane.

Didn't realize that these cluttered photos were the only ones that I had at the time I posted this.

I'll take some better ones as soon as I get some time.

A couple of things that I really liked about this plane is that the builder did a pretty good job of construction and covering, but also, I see no oil residue and so don't think that a motor was run on this plane let alone even mounted.  I don't think it has ever been flown.

The first thing I looked at doing was to figure a motor mount

You can see here the holes for the original motor mount.  Fortunately the builder install blind nuts from the back side.  I just needed to figure out what size they are and how to go about using them.  They are oddly laid out so I can't directly use them and I'll need an adapter.

You can see the blind nuts in this photo.

I decided to use a circle of 1/8 inch plywood.  I would drill holes to line up with the engine mount holes and then drill holes to fit the electric motor mount.

I lined up the disk from the back side so that I could transfer the mounting holes from the front side.

Here is what I came up with.  I started counter sinking the holes so that I could use flat head screws so that it will fit flush against the firewall.

Here are the parts that I came up with to create my motor mount.  I ordered some aluminum stand offs from an online source and screws and washers from my local hardware store.  As I recall all of the threads turned out to be a standard 10-24.

Here is how the stand offs will fit with the electric motor x mount and the original motor mount.

This is how it would look with the longer stand offs.

Here is the new round plywood mount test fitted in place.

I needed to ream out the x mount slightly to fit the new screws.

Now the screws fit fine.

Here are the different stand offs and screws that I used.

Here is how it would look with the long stand offs.

This is how it would look with the short stand offs.  I like this look better, it puts the propeller closer to where it would have been with the originally designed gas motor.

I used different amounts of washers behind the x mount arms to set down and left thrust angles.

Here is the end result.

Now I need to start looking at where and how to mount the battery, ESC, and the two servos before I can get this thing back in the air.  These will be done in future updates.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

Wing One Rebuild (Say that fast 5 times)

This beauty was my next project!

This wing came to me from the second owner who had not actually done anything with it.  He reported that the original owner had flown it with some sort of pod on top that housed the battery, electronics, and motor.  The pod and what was contained were no longer with this wing.  It did show signs of having been flown but was still in really good shape.

Here I started to take the covering film off of the trailing edge of the section between the elevons.  I started to do this because I knew I would need to take this section out to be able to move the motor forward.  I wanted to move the motor forward because I also knew it was going to be hard enough to get the CG right without the motor being so far back.

Here is a closer look after I had cut the trailing edge balsa lose.  I also have the motor/prop combination that I intend to use and the start of a motor mount/firewall.

Here I'm getting an idea of how things will line up.

Here is how I originally thought everything might lay out.

To provide for some flexibility in the power system (in anticipation of crashing), I decided to use a block of stiff foam to mount the firewall.  I cut out the covering film where this foam block will be glued down.

I decided to use Gorilla glue to secure this block as it would expand into the foam as well as adhere to the wood and foam of the wing.  Also, Gorilla glue is more flexible than epoxy (remember the anticipated crashing?).  I used the popsicle stick to help spread out the glue.  I did not show these steps, but I also spritzed it with water to help activate the glue and then held everything in place with masking tape.
(Our cat Dewy is trying to get in on the action)

Here is all of the pieces glued in place.  I made sure to have the motor wires run over the top just because I though it would make it easier to connect up.  Also, you can see the slight up tilt in the motor.  This was done to keep the thrust line pointing to the center of mass.  If you do not do this with a pusher, you will get pitching up or down when applying power.

After doing some CG work (I used an online CG calculator for flying wings to come up where the CG should be for this wing.  I think I used one of these: wingcgcalc and fwcg), I realized that the battery would need to mount like this to get the CG right.  I centered the battery and then traced around it and dug out the foam about half an inch down.  I did not want to go too far into the foam so as to maintain as much strength as possible while still providing a good battery mount.  You can see that I glued some bamboo skewers into the long corners of this cutout.  I also wrapped a strip of velcro around each of these.  I thought that these would help reinforce the foam and help to secure the battery.  This actually worked very well.

Here is a closer look.

 Here the battery is strapped in.

Here I am out for the maiden flight.  A friend who is a really good wing pilot got it up in the air for me and then handed the controls over after he trimmed it out.  Thanks Richie!

If flew great and he was easily able to launch it and trim it out.  I came down a bit hard on a landing and loosened the glue on the firewall.  I just used a couple of rubber band from front to back to secure it and that is what you can see here.  I did this because I was not ready to go home and really wanted to continue flying!

(Editorial Note: I am not condoning the flying of damaged airplanes in any way!)

  It flew great just like this for two flights.  Then I came in rough again and encountered the damaged prop and completely broken loose firewall that you can see here.

Here it is again all rebuilt and ready for another day of flying.

I have been really impressed with how durable wings can be.  I have continued to fly this wing just as it is for many flights including some nasty crashes.  My worst crash was at a pretty good speed into a street curb.  The crash destroyed the battery and broke the hinges on one elevon and the related clevis.  I have since replaced the battery repaired these and flown it again.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

CG Finder

Hello all,

I finally decided that using my index fingers was not accurate nor useful enough any more and that I needed a better method to find the CG on my planes.  I checked out commercial CG finders with lots of cool options, but being the cheep Dutchman I am, I decided I could just make my own.  So, the following is the process I went through to make a CG finder.

CG finder pieces

I started by looking for a suitable stand.  I had seen others use a 2x4, but I did not want something that size.  I looked in my scrap wood bin (what do you mean you don't have a scrap wood bin?) and found a piece of primed trim about 3/4x2x12".  This seemed like it would work fine.  Then I looked for something for uprights.  Again to my scrap wood bin and I found some 1/4" wood doweling.  I cut two pieces about 10" long.  I then drilled two 1/4" holes in the base about 8" apart.  All of these measurements so far were just arbitrary and just guessing how much clearance I might need or want.  Enough rod length for fuselage body and landing gear clearance, and separation of rods for a suitable width.
 I wasn't to concerned with the size or stability of the base as it would be at, or close to, the CG or balance point and would not need much stability.

Rounded off rod tips

I did round off the ends of the rods a bit to provide for a smaller more accurate tip, but one that would not poke into foam or covered wings.

All setup

Setup it looks pretty good and works well too.  I did not glue in the rods so that I could take it apart for easier transport.  The pieces fit quite well in the upper tray of the little tool box to the right in the photo.

CG finder being used on my Wild Hawk

Using tape measure against rods

This little unit has worked quite well and for the money, you can't beat it.  Besides, it's really hard to take measurements with a ruler when the plane is balancing on your finger tips.

My conclusion, if you need a CG finder for your plane, just go out and make one!  It's real easy.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.