P30 - Ideal for Improvers

Did you enjoy building and flying your first rubber powered model? Are you hungry for more? A P30 class model may be the perfect answer. This class is a few decades old and is very popular. It suits the developing modeller and also provides a real challenge for experienced fliers. The rules vary slightly country to country, but in essence are:

1. Wingspan and overall length each less than 30 inches.

2. Plastic commercially available non-folding prop less than 9.5 inches in diameter.

3. Rubber to be enclosed within the fuselage.

4. Rubber including lubricant to weigh less than 10g.

5. Model without rubber to weigh 40g or more.

These things can fly! Two minute maxes are not difficult to achieve. Flyaways are common, so you need a good dethermaliser. The minimum DT is the pop up stab - see the photo at the bottom. While these are ok, they may be insufficient to bring the plane down from a strong thermal. More drastic DT is the pop off wing. The wing tip is connected with a line to the rear end of the fuselage. When the DT releases, the wing comes off. The fuselage hangs down and the wing spirals around as the plane descends.



These are photos of my first P30. It is based on the Roger Dodger design, but I could not help modifying it in various ways.

The photos also show a simple design for a "stooge". This is basically an anchor point to hold the plane while you wind the rubber with a mechanical winder. It is also advisable to use a "blast tube". Mine took 5 minutes to make out of a piece of 20mm plastic piping that I had lying around.

Below is a brief video of the model at the top of the power climb. It flew OOS on that occasion, but was later recovered (thank Hung I wrote the phone number on it!) That happened because I set too long a time period on the DT. Doh!

Free Flight models can fly OUT OF SIGHT!

Flights that go OOS (out of sight) create mixed feelings. In competition, they can mark the end of your flying day. In recreation, they are a little upsetting, but in an odd way satisfying. After all, the model has performed very well to stay in lift for so long. There is a theory among aeromodellers that the thermal God, known as "Hung", takes only the best models away. This is so that good people can play with them in the afterlife :)

Here are some tips:

1. WRITE YOUR MOBILE NUMBER CLEARLY ON THE FUSELAGE AND WING

It is worth it! Two of my models have flown OOS in the last year. One, an 8" span HLG, was found months later a few miles away in the woods by an old lady out walking her dog. The other, a P-30 rubber plane, was found about a week later in front of a house. It must have been on the roof for a while, because the prop was still stuck up there. In both cases, the finder rang the mobile number and the models were back in the air after just a little repair work.

2. ALWAYS GIVE THE FINDER A LITTLE GIFT

Chocolate is good, wine for adults is ok too.

3. FIT A DETHERMALISER.... OR BUILD LOTS OF MODELS!

DT's are a subject in themselves. Examples are:

• Pop up flaps (side or top)
• Dropping weight
• Dropping streamer
• Pop up stab
• Pop up wing
• Pop up tailboom, also called "broken back"
  
• Pop off wing

However, even if you have one, it does not mean that it will bring your plane down safely. Things can go wrong. For example, the DT may not be powerful enough to make the model descend out of strong thermals. Or the DT may fail to operate. Some people just don't bother with DTs, but instead just make lots of models. If you are into competition, I think you need to learn how to make and fit DTs and use them consistently.

Make your own Propeller

Why?

Why bother with carving a propeller when you can buy a plastic one cheaply? Surely a balsa prop would break easier than a plastic one, I hear you say. Perhaps that is true, but I was surprised by the robustness and lightness of my first self-made prop. Less weight spinning around means easier trimming, not to mention a lighter model.

How?

I followed the inspirational instructions provided by Dannysoar here. I did not have a block, so laminated bits of 6mm balsa that were lying around with PVA glue. One piece was a "dog" because it was so heavy. It is almost as dense as spruce and I could not find any use for it in my models. So I used that piece as the topmost sheet, that is, to be the front or the leading edge of the prop. Also, I was careful about aligning the grain of each sheet so that one piece was not running opposite. This prevents "snagging" during the carving. I sawed the block into triangles, marked and glued it (photo above) this time with epoxy. Then started carving with a normal craft scalpel. Balsa cuts easily and it was really quick.


The photo on the right shows the initial carving. Basically, you carry on, try to keep it even, then shape the tips. Every now and then, put a piece of wire through the hole and check the balance of the prop. Remove material from the heavier side. Carefully glue some tubing in the hole, check balance, sand and smooth it off. You will need some form of free-wheeling device. I used a simple Z bend clutch - called a Garami. This prop was for my Cloud Tramp. It flies much better than it did with the plastic prop.

The photos below and on the left show details of the Garami freewheel clutch and the finished prop installed on my Cloud Tramp. As a final job, I superglued thin cotton thread to the LE for protection. So I've found a use for that heavy balsa after all! Even though this laminated prop had lots of glue in it and the heavy bit of balsa, it was still 20% lighter than the plastic prop. Wood is a difficult material to beat...

It is a very satisfying thing to do and much easier than I expected. Since the pitch of the wooden prop is higher, the duration of the power run is longer.

I think it also looks prettier.

Trees

Trees attract balsa. Even if there is only one tree around, you can guarantee that your model will end up in its highest branches. Here are some tips for recovering your work from the clutches of a "balsa magnet" otherwise known as a "tree":

• Don't fly where there are trees!

• It is not worth risking your life to get it down, even if did take a long time to build. This means: do not try to climb the tree

• Watch the model carefully. Binoculars are useful. Note where the model landed - not just which tree, but where in the tree

• For lower level stuff, use a 6m telescopic fishing pole. In England, these are called a "whip". Buy from eBay or online for just a few pounds. Put some white tape at the end, so you can see the tip. Use it gently, or you may put a hole in the wing!

• For higher level stuff, use the ball and line method. This involves looping strong fishing line over the correct branch, taking hold of both ends and shaking until the model falls out. To get the line up there, attach a weight to it. A heavy-ish ball the size of a tennis ball is good, because you need to be able to throw it accurately. Throw it as close as you dare to the model over the branch that it is snagged on. The fishing line should be heavy duty (at least 10kg (approx. 20lb) strength). Attaching the line with loads of plastic parcel tape to a tennis ball can work fine. I used it to get a plane down from the tree in the photos here..

The plane was stuck just next to the ball that you can see here. It was at about 10m high. This is a lovely oak tree. However, we got down eventually, with no harm to tree or any person. I'm afraid, a ball was left behind, but it did fall out later.