Tips on how to fly

This should probably be an entire lengthy section on it’s own, but because it’s covered in detail in the instruction manual and on the DVD, I’ll provide an abbreviated summary here, mostly for those folks who are just browsing.

Trim:

Anyone who’s built an RC aircraft knows how important  the Center of Gravity (CG) is to proper performance.  This is also true with respect to the ORCA.  Also crucial to the ORCA is it’s buoyancy.  These are achieved by the addition of a small amount of lead or polystyrene foam or both.  Make sure that the ORCA is slightly negatively buoyant, that is to say, that it sinks slowly.  If the CG is correct or close, it should sink with a slightly nose down attitude, and may slip into a slight glide to the bottom of the pool.  This should get you very close to a proper setup, but, may become an emperical exercise.  You may continue  to make small changes in lead or foam and see if this improves the ORCA’a stability with regard to pitch.   For example, my most recent model required a couple of ounces of lead installed in the nose and a small amount of foam near the rear to achieve the proper attitude in the water.  This may sound like a time consuming process, but you only have to do it once to know what works best, and it is definitely worth the time to do properly.

Radio Setup:

If your radio is capable,  the wingerons and elevator should be setup on exponential rates, with about the first half of stick travel being linear, this will make the ship more manageable at full throttle, where smaller surface deflections are needed for control, yet still allow for huge deflections at full stick travel when needed.

Propeller:

If you’re having trouble because the ORCA is too fast to keep up with and you can’t stay out of the throttle, try switching to a smaller prop until you feel more comfortable. This will not only slow the ship down and increase the low speed range throttle response, but also extend the battery life.

Making turns:

 In general, in order to maintain a constant depth, most turns should be made at, or near, a “knife edge”attitude.   Roll the ORCA 90 degrees onto it’s wingtip then make the turn using up elevator.  Coordinated wingeron/rudder turns are possible at low speeds, but as speed increases, this becomes increasingly difficult, because  the rudder is not very effective in keeping the nose down in coordinated turns.  Addition of a small dorsal fin around the CG, or vertical winglets on the wing tips will make the rudder more effective.  As with any RC vehicle, avoid overcontrol and make turns smooth and methodical.  Because the ORCA is fast, mentally plan your turn ahead of time, or you may run out of pool.  In addition, you’ll find that precision flying is more rewarding than just “hot dogging” all over the place.  It’s more esthetically pleasing too!

Loops:

Loops are probably the easiest maneuver to learn.  The ORCA will perform loops in about 3 feet of water, but this will require full elevator deflection, about 45 degrees.

Rolls:

Thanks to the wingeron design, the ORCA is capable of a fairly high roll rate, as you may have seen in the videos. The secret to a successful roll or series of rolls is the proper entry attitude, that is to say, neutral pitch, so that little or no elevator input is required.  Once you have mastered loops and rolls, this opens the door to many other maneuvers that are really just combinations of loops and rolls, like the split-S, the immelman, and the Cuban-8.

Surface Breaches:

Oddly enough, an impressive surface breach is one of the most difficult maneuvers to perform,  largely because it is performed at full throttle.  The idea is to arrive at the surface  with a minimum of speed loss, and at 45 degrees from horizontal.  Start as deep as possible, at one end of the pool (unless you have a gigantic pool) and go to full throttle.  We have found that the minimum speed loss is to execute a 1/8 loop at top speed, then neutralize the elevator and carry a straight trajectory to the surface.  Any course corrections will result in a speed loss, so try to keep control inputs to a minimum, and have a blast! We haven’t actually jumped one out of the pool yet, but...

Stuck inverted on the bottom of the pool:

Apply full down elevator, and full reverse.  This should result in a reverse 1/4 outside loop. As soon as the ship is off the bottom near vertical, apply full up elevator and forward power.

My ORCA keeps porpoising !

First of all, what’s porpoising? Well, we’re borrowing an aircraft term here.   When an aircraft porpoises, it bounces during landing because the plane wasn’t “stalled” onto the runway. It’s an entirely different cause with the ORCA, and it looks just like a porpoise swimming with that up and down motion.  The ORCA may frequently break the surface of the water, which can make it difficult to turn or perform other maneuvers. This is usually an improperly trimmed ship, which may be aggravated by either elevator overcontrol, or elevator linkage problems.

 If the CG and/or buoyancy of the ship is off, this can cause an inherent instability that will require constant elevator input to maintain a constant depth.  Take some time and make sure to eliminate these as the cause(see above). 

Also, there could be excessive play in the elevator linkage. A small amount of play is unavoidable, something on the order of 1/16” to 1/8” at the trailing edge (TE) of the elevator.  Remember, because we are using long servo horns on the servo and short horns at the surface, any play in the linkage will be exaggerated, so make sure the clevices fit as snugly without binding in the horns. 

This brings me to another culprit: sticky, stiff, or binding pushrods/clevices.  This can prevent the elevator from returning to center when the stick is centered.  This is easy to check for.  Move the surface in both directions several times and make sure that it always returns to center.  If not, disconnect the pushrod from the control horn at the elevator end and check to see if the pushrod is binding, or if the elevator torque rods are binding in their sleeves. Sometimes it’s a simple matter of pushrod alignment, or cleaning a little gunky material from the torque rods (sometimes masking tape “stickum” leftover from painting).

Pushrod installation

This seems like a good time to talk about pushrod installation.  When you’re installing your servos, test fit them a couple of times with the pushrods installed.  Insert the WTC into the fuselage and make sure that you don’t have any pushrod alignment problems at the surface control horn end when the servo is actuated.   As the servo arm moves from center to full throw, it pulls the end of the pushrod closer to the inner wall of the WTC. When the other end of the pushrod is connected to the surface, this can lead to binding where the pushrod exits the WTC . Sometimes a very subtle arc in the pushrod where it passes through the WTC wall will help the pushrod clearance as the servo arm moves. The time to make any adjustments is before the waterproof pushrod seals are installed.  If it’s a problem on the ground, it’s going to be more of a problem in the air, or rather, in the pool.

I’ve got a leak !

Wow, this one’s a headache!  First of all, don’t freak out.  You probably haven’t ruined any of your electronic components.  It might look like your rudder stick moves the elevator, but when everything has had time to thoroughly dry out, usually everything is all right. Assuming that you did a proper job of cementing the PVC together, there are actually only a couple of places that can be the source of the leak.

First, examine the front plug. Check that the square shoulder of the bolt engages the square cutout in the steel backplate, and make sure that the little rubber seal is properly seated.  Literally tighten the wingnut as tight as you can get it.  I use a big crescent wrench on the wingnut, and I still tighten it pretty much as tight as I can get it. If you are still unsure about the plug, you can make a test section from an 8 foot length of PVC from your local hardware store. Simply insert the plug, tighten, stand the assembly on its end and fill it with water. Check for leaks around and inside the plug.

It’s also possible that you have a damaged or improperly seated pushrod seal.  Carefully inspect all your seals. When in doubt, replace them all; they’re relatively cheap compared to the pain of trying to find out if one of them is bad.  You can also test your seals by slightly pressurizing the WTC with the seals underwater and look for bubbles.  It sounds somewhat crude, but if you place a 3” to 1 1/2” reducer on the front where the plug would normally go then wrap the joint with electrical tape, you can blow into the 1 1/2” opening. Also watch for bubbles around your charging connectors.

This really only leaves the propeller shaft. MAKE SURE TO PACK THE SHAFT BEFORE FINAL ASSEMBLY. I can’t stress this strongly enough. If you assemble the WTC without packing the shaft with a good grade of white lithium grease, it will leak like crazy. Unless you’ve opted for the two piece rear module, you will have to hack the WTC open and build another one.   We’ve operated ships for over a year without having to repack the shaft, so if you do a good job to begin with, you’re safe for a long time.

Fiberglass repair 101

Always follow the manufacturers safety guidelines when working with polyester resin. If you don’t have a respirator, do not work in a confined space.

Under normal circumstances, the ORCA should never require any kind of fiberglass repair. Within the environment of the swimming pool it’s unlikely that the fiberglass hull or wings could be damaged.  However, outside the pool is a different matter.  Because the ORCA is heavy, dropping it on a hard surface from more than a foot or so could do some damage.

If the damage is just a severe gouge or scrape, a little light sanding followed by application of some polyester gelcoat should be all that is required.  When working outside a mold, I use almost double the amount of catalyst with gelcoat to guarantee that it cures fully - it’s inhibited by oxygen.  Also, the curing process is temperature dependent.  Ideally, the ambient temperature should be above 65 degrees.  Even at that temperature, you might want to place an inexpensive desk lamp with a 60 Watt bulb nearby to keep the surface slightly warm.  Build up the damaged area a little higher than the adjacent surface then sand it down to match.  Start with ~ 200 grit wet sandpaper, then finish it with 400 or 600 grit paper.

Areas of damage where the fiberglass is cracked or broken will first require the removal of the damaged material with a Dremel cut-off wheel or grinding stone.  Also, rough up the surrounding area somewhat, in order to create some surface area for the patch to bond to. If you have a hole completely through the hull, you may want to consider using tape or plasteline modeling clay (available at Art Supply stores like Michael’s) on the inside to support the repair. Also, as a side note, the plasteline clay can be used to build up a dam to protect the nearby areas from the resin. Cut the fiberglass cloth a little larger than the damaged area, and place a two or three layers of cloth over the area to be repaired.  I like using Tap Plastics lightweight cloth. You will probably need a total of about 5 layers.  Then sand it all down with 200 grit sandpaper, wet.  Using your Dremel, make sure that the surface of the repaired area is a little lower than the adjacent surface to allow for the gelcoat.  Then, gelcoat as above.

Some tips on painting

One of the keys to a successful paint job is surface preparation.  Perform your final sand using at least 400 grit wet sandpaper or finer.  You can fill any imperfections using automotive glazing compound or a filler like Model Magic.  Make sure the surface is clean and dry.  If you’re doing a multi-color scheme, allow the first color to completely cure before applying the masking tape.  Wait at least 24 hours, longer if you are patient enough.   For masking,  use vinyl electrical tape. Vinyl tape will not be degraded by most paints, it has a much smoother edge than masking tape, and it is flexible enough to easily form curved lines.   Wash your hands thoroughly to remove the naturally occurring oils, then apply the tape, keeping the handling to a minimum. Take your time and make sure the tape is where you want it, and that the edges are adhered to the surface.  Don’t apply the tape more than a day or two before you plan to paint or it will become very difficult to remove.

Our prototypes were painted using Klass Kote epoxy paint.  It is a great performing paint. It’s spectacularly glossy, adheres to the gelcoat surface great, and is very durable. And if you’ve been around scale RC planes for a while, you know Dave Platt loves it. Klass Kote recommends wiping down the surface to be painted with their epoxy thinner prior to painting. Make sure that adequate time has passed to allow for complete evaporation of the thinner before painting, or you may get “fisheyes”.  The only downside of this paint is that it requires that you have a spray gun. 

If you don’t have access to a spray gun and compressor, the best choice is Krylon Fusion for plastic.  There are a large variety of colors available, and it’s safe to use on the styrene tail surfaces.

Regardless of which paint that decide you use, double check that your tape edges are still sticking to the surface, and start with a light mist coat.  When spraying the paint, begin spraying a couple of inches away from the surface to be painted then pass over the surface, continuing to spray beyond the other end.  This will eliminate the possibility of getting “spatter” on your finish that sometimes comes out of the spray nozzle when paint starts and stops flowing. Wait two to three minutes for this to tack, then follow with another light coat.  Don’t try to achieve complete opacity even with this coat.  Again, wait a few minutes, then apply a third slightly heavier coat.  The third coat will be less likely to “run” because it will begin to bond to the previous coat.  Several light coats always yield a better looking paint job that fewer heavier coats. The final coat should look wet, smooth, and shiny within a few seconds of spraying.  In general, spray can paint will require more coats to achieve complete opacity than paint applied using a spray gun.  This is because the pigments in spray can paint are more dilute to help prevent the spray nozzle from clogging, so be patient, and remember, another coat is better than a big run. Believe me, I know.

Remove the vinyl tape as soon as possible, within a half hour or so. This may seem crazy, but it will be less likely to damage the paint edge if removed before the paint is completely cured. Keep some small tweezers and an x-acto knife handy to get the end of the tape started coming off. No matter how they make it look on American Chopper, nobody likes to paint... good luck

A word on gunite/concrete swimming pools

Sometimes it’s called gunite or pool-krete.  Whatever it happens to be called, it’s basically a layer of concrete sprayed onto the inside of the pool. It’s about as rough as 50 grit sandpaper, and if you scrape the ORCA against it, it will definately scratch off the paint, and depending on how fast, hard, and far that you scrape, you may even scrape off some of the gelcoat.  It will be hard to keep your ORCA looking beautiful if this is the type of pool you will be flying in.  You might want to consider painting it with a rubber coating.  Caswell Plating, Inc sells rubber coating in 11 oz. spray cans.  We haven’t tried this yet, but would love to hear from someone who has.