Sea Salvage and Restoration, Part Two

I skinned the fuselage with red "Monokote".  This is a plastic with a heat activated glue backing.

Unfortunately, I don't have any picture of the skinning process.  This was my first attempt skinning an entire plane and it didn't turn out bad at all.  I started by taping a couple sheets of paper together to create a pattern, before cutting the Monokote.  Paper is cheap and easier to cut than the plastic.

Here is the battery compartment that I scratch build to replace the missing one.  There are plywood formers at either end.  The formers where notched with a file along the curve of the former at regularly spaced intervals.  I glued bamboo skewers at the aft end and the magnets on the cowl hold the cover in place.  After the skinning was complete I cut vent to allow air to flow out and cool the motor controller and electric motor.

Finally, here the tail section.  I like how you can see the ribs through the plastic in this shot.

Das Boot

The original plan I had in mind was to build a boot.  Six planes later and I finally return to this idea.  What I learned about balsa wood construction building planes, translated well into boats.

The basic design goals for my RC sailing boat are speed, control, and stability.   I also wanted to experiment with a laminar flow hullform.  You don't see many boats with a laminar flow hull and there's probably a good reason for this in full scale boats.  However for this sized boat scaling factors make drag due to wetted surface area less of a issue.  The intended effect for the laminar flow hull to to provide roll and directional stability.

This a sailing boat so there is a keel to counter the heeling force of the sail.  The keel is comprised of balsa surrounding an metal core made up of an old 1/4in allen wrench and a 3in x1/2in diameter rod.  The keel mass was about 150grams.

Notice the strut for the hydroplane.  This also make a nice stand. It's a Popsicle with a piece of steel wire along the leading edge for rigidity.  I tempered the steel wire by heating red hot, wait ten seconds, and then dropping it into cold water.  I've determined that ten seconds makes perfect spring metal that's not too brittle.

Here is a front view of that very deep "V" hull.  Loaded to the gunnels, this hull displaces about 2lb.

Now to level the deck, so that I can have a watertight seal.  Later I'll add a plywood deck that will act as a removable servo tray and provide a mount for the sail mast.

The rudder is comprised of balsa around a bamboo core.  The top inch of the bamboo core is epoxied into a brass tube.

Another view with the rudder in place.

I build the hydrofoil around the Popsicle/steel core and the filed the top surface into a 6% thick foil.  Notice that bias of the wood on the bottom runs front to back and the bias on top is from side to side.  That makes the top surface easy to shape while the bottom strengthens the trailing edge so you make it sharp.

This project is a bit further along now but I need to take a few more picture.

Sea Salvage and Restoration

This plane was found by my beach combing friend, Greg.  The servos and ESC (electronic servo controller) were corroded badly, but the receiver, motor, wings and fuselage were mostly intact.

There where a few broken longerons, stretchers, ribs, and leading edge of the port wing.  I ended up striping the entire air frame to reach all the repairs and to prepare the surfaces.  A telescope tripod helped steady the frame.  Tweezers and an ice cube helped release the plastic.  While a hair-dryer only acted to reactivated the adhesive.  A few scraps of balsa and a dab of CA here and a glob of Gorilla Glue there it was ready for sanding.

The battery compartment was missing so I fabricated one by tracing the battery bay and cowl curves.You can't see it here because it's missing.

The elevator was broken on the port side but the starboard side was intact to measure and pattern.  The rudder and stabiliser we both badly broken.  I looked at a few photos from the manual and online, then measured the trapezoidal corrected images.  Measurements from three images matched within 5%, so I used these proportions to recreate these surfaces.

 The fibreglass cowl was cracked and I cracked it even more trying to remove a mounting bracket that was installed backwards by the original builder.  I sanded it inside and out.  Taped on a small piece of fibreglass over the most damaged area and applied epoxy to any exposed glass on the outside.  I use a bit of CA Glue along the edges of my patch to keep it from fraying. After drying, I removed the tape on the inside and applied a thin coat of epoxy.  I filed the outside smooth, filling any pits with Gorilla Glue, drying then sanding smooth.  I coated the entire cowl with a thin layer of epoxy mixed with black iron oxide for pigment.  The tiniest amount of iron powder makes normally brittle epoxy measurably stronger.

Learning to fly

My first time at the stick I took off and landed perfectly.  Ever since then I've threw caution to the wind and ditched as many times as I've touched three points.  I tell myself "these are experimental flying machines not pussy cat trainers." but the truth is that good judgement can be learned, and unlearned.

Learn good judgement here, then fly the surface vector:
Stick and Rudder: An Explanation of the Art of Flying
by  Wolfgang Langewiesche 1944

This flying by the seat of your pants with sound old school Newtonian physics.  Also, seriously old school, being written in 1944.  Wolfgang's terminology is kooky, but no more than his knuty 1917 counter part Horatio Barber.

Dan Dare meets Steampunk:
The Aeroplane Speaks
by Horatio Barber 1917

A schizophrenic anthropomorphism of every component in a plane.  You will hear voices after reading the prologue.  Awesome illustrations throughout.  The last bit is rather poetic.  It was intended to brace new US Army pilots for the majestic beauty of flight but it almost conveys a hidden chapter on chronic fatigue.   

F4V vertical stablizer area reduction

I mentioned earlier about modifying vertical tail area to allow for tighter roll.  Here is a picture showing the modification.

The reduction of the stabiliser made this plane rather hard to handle.  What a wild ride this was.  The chequered circles were quite helpful in determining the last know position was over San Francisco Bay.  I wish I could share the video but its "gone over the hill".  Maybe for the better.  It was failure played out by the pixel. ;-(

The observations were:
1. the inverted "V" tail is a roll and pitch stable configuration
2. typically the vertical stabiliser is the roll stabiliser
3. the failure of either "V" tail control surface results in roll instability
4. don't fly when its blustery you'll be down field so far you don't know what even happened
5. cut the power and nose it in; you can build again from the salvaged parts, but only if you can find them.

One problem with this configuration was all the hang time.  It floats and floats and floats on a landing approach.  In retrospect I should've ditched into a shrub, but when you're flying youre flying, and sometimes you just can't stop.  You tell yourself, "One more pass will be the perfect one."

This plane was last seen circling up into the sky in a votex that carried it higher and higher and over the hill, over the highway and into the bay. 

The makings of an Airplane

I like to create mind maps for my ideas.  I think they look cool too.

Early Flights

Originally, I went to the hobby shop searching for a radio to control an RC sailing boat I was thinking about building.

I walked out with a Spectrum DX7, a ParkZone T-28, a ThunderPower 11.1V 30C Lipo battery, and Triton AC/DC battery charger.   The plans to build a boat would have to wait.

Here we are in a early field operation of the T-28.

The wooden structure is the open crate I build to transport this model.  Here is a mock-up of the crate I did over the T-28's identification chart.

 

The ParkZone T-28 flies well and its foam construction can take a lot of damage.

One plane turn to two planes, with the addition of the ParkZone F4U.

I wasn't very impressed with this plane when it arrived.  The starboard aileron servo proved to be bad during the preflight check and the adhesive gluing the Styrofoam fuselage was separated near the stabilizer.  Nevertheless the customer support was friendly and replaced the servo right away.  I glued the fuselage together but the first flight didn't go well.

Oops!  The plane started porpoising up and down from the moment it took off.  Clearly the CG was off.  Anyway we can fix this and did.  Behold the F4V in flight.

 The cowl is a green soda bottle and the tail is a inverted "V".  It flew surprisingly well and looks a bit like a swallow.  Amazingly you can switch directions in a very short radius.

Odd looking isn't it?  This configuration was quite stall resistant.  In this frame from the video, it's mushing along, nose up at just the slowest speed (~12kts) possible to stay in the air.  The video was zoomed in tight but there are some good slow passes at eye level.  I'll try to split out the best parts soon.

It didn't roll very well and was a bit too stable.  So further refinements where made to reduce the vertical tail surface, with disastrous effects.  More on that later...

Nutty Ideas

I've got a lot of nutty ideas that sometimes I get around to realizing.  I hope you find these thought provoking.
-Brent