P-30 Class rubber powered

[ZIP.58]

Anyone who is seriously interested in rubber-powered model aircraft will sooner or later come across the so-called P-30 class. P-30s are models that are built and flown according to precisely defined rules. This competition class, which originated in the USA, is now built and flown worldwide. It is most popular in the USA itself, but also in Eastern Europe, South America, Asia, and Australia. Kits for such models are available in stores, for example from IKARA (CZ), CB Model Designs (US), atalarmodel (TK), BMJR Models (US), and others. Unfortunately, they are not available in specialist shops here in Switzerland, but can only be ordered online. Free plans are also available for download from outerzone.co.uk, AeroFred.com, hippocketaeronautics.com, and other providers.       ...

Images: Own design 'Primus'

[ZIP.58]

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What makes this class special?
-    The simple design and clear construction specifications enable every model builder,
     even beginners, to build a model with good flight performance with normal construction
     effort.
-    The model is made from materials that are available from specialist retailers.
-    As the P-30 Class is a free flight class, no RC system is required, which makes these
     models interesting for schoolchildren and young people, as well as for construction
     courses.
-    The P-30 Class is ideal for designing and building your own models.              ...

Images: Own design "Secundus"

[ZIP.58]

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I built my first model, called "Contester," based on a plan I downloaded from the Internet. The model was published in the February 1958 issue of "Aero-modeller" magazine, is made entirely of wood, and was built in a single weekend.
I was more than surprised by its flight performance after the test flights, and using the existing thermal brake is a "must" to prevent it from flying away!                   ...

Pictures: Construction according to the "Contester" plan

[ZIP.58]

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I now own three models, two of which are my own designs, constructed according to the P-30 Class rules, and a fourth is currently in the drawing stage on the drawing board. The "Primus" model has a truss fuselage and ribbed wings, while the "Secundus" model is a pure wooden construction with a Jedelsky-style wing. Along with all the other rubber-powered models, these three are the ones I fly the most. It's a lot of fun to fly these models, despite the often long walks back to retrieve them (model flying is a sport, after all!). Thanks to the thermal brake, however, I haven't lost any of the models.

Peter

Images: "Tertius" is designed and drawn

[calgoddard]

Zip -

Your P-30 models look like excellent fliers.

The P-30 plan you are drawing up looks first rate.

Thanks for posting about the P-30 event which is my favorite outdoor free flight event.

[ZIP.58]

calgoddard

Thank you for your comment.
It's true, the two models "Primus" and "Secundus" have great flying characteristics and are a lot of fun.
Primus was designed as a model for technical education in schools and originally had a larger wingspan.
This was later reduced to P30.
Secundus was designed as a P30 right from the start, but was made entirely of wood. This was also for craft lessons. The wing is constructed in the so-called standard design (Jedelsky) with a profile board, end plate, and support ribs. The rear wing is a piece of profile board.
And Tertius? This has now been designed and drawn. It just needs to be built. When, I don't know, as there are other projects to work on first. Postponed is not canceled.

Peter

[Crabby]

Great stuff Zip!
Primus Secundis and Tertius. Next is Quadris. I have been dipping the foot into this class and have an Elliptis half built. Its a pretty thing with eliptical wings and undercamber it was fun to frame out. My trouble is I don't care for all the tackle necessary to install a dethermalizer. I will wise up as soon as I wrap my stubborn head around a DT that makes sense to me.

[calgoddard]

Crabby -

I am glad to see you have jointed this third generation of HPA. I have always enjoyed reading your posts.

A P-30 will inevitably fly out of sight (OOS) in a thermal. If it is legal in your area, a fuse DT is very simple to install and will reliably trigger. You just have to time the burn rate of the fuse and adjust the amount of fuse that extends beyond the Aluminum snuffer tube installed in the rear end of the fuselage. It's good if you get the fuse to reaches near the exposed inner segment of the snuffer tube after about two minutes of burning, so that your P-30 gets credit for a max.

See the first picture on the left that shows a fuse DT set up.

The second picture shows the ends of a blue No. 10 rubber band wrap around opposite ends of a dowel that extends through the fuselage just forward of the LE of the stab. The middle section of the blue rubber band extends through a hook secured to spar of the stab about 1/4 the distance of the chord from the LE of the stab. Often this hook can be anchored in a center rib of the stab. When the stab is pivoted to its flat position where it rests on the end of the fuselage, the blue rubber band is stretched.

As shown in the picture with the fuse, one hook extends from the TE of the stab and another hook extends from the end of the fuselage. These hooks are preferably made from light music wire such as .025-inch music wire. One hook extends above the fuse and the other hook extends below the fuse. A dental rubber band extends between the hooks across an exposed segment of the fuse to hold the stab down. When the fuse burns down, it severs the rubber band allowing the TE of the stab to tilt upwards under the force exerted by the blue rubber band.
A length of monofilament fishing line or Kevlar thread (not visible in the picture with the fuse) is connected between the TE of the stab and the snuffer tube (or some other attachment point where it won't get burned). This line limits the upward travel of the TE of the stab and its length is chosen so that the stab ends up at a 45-degree angle. The P-30 then gently descends in a horizontal orientation in all but the strongest thermals.

Note that in the picture with the fuse the tilting rubber band extends from a hook on the stab (not visible) through the fuselage to a hook on the bottom of the fuselage. This is an unconventional configuration for anchoring the tilting rubber band to the fuselage. The arrangement shown in the picture with the twin fin stab is more conventional.

There are two critical things that bear mentioning. First, use an electric igniter to light the fuse. If you use a lighter with a flame, you can set your model on fire. Second, make sure that there is considerable force pulling the stab upwards. If there is a weak force, the stab may only pivot 10 degrees or so, after the dental rubber band is severed by the burning fuse, and be held back by the oncoming air in the glide. In this case, the model may not be rescued from the thermal. If necessary use more than one rubber band to increase the tilting force. The tilting force exerted on the stab when it is held down by the dental rubber band should be robust.

Flare the rear end of the snuffer tube with a Phillips screw driver to make it easier to insert a length of fuse into the tube.