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'
...
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"
...
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
...
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
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.
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
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.
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.
I completely agree with calgoddard. Without DT, losing the model in good thermals is inevitable, or you face a long walk back. I've experienced all of this, but thanks to the address label, I got the model back.
Until now, I have always worked with a glow cord. 1 cm of cord gives a burning time of approx. 1 minute. But you have to check the burning time every now and then, otherwise you might be in for a surprise.
Last year, I equipped the Contester model with a ViscoDT, but left the hooks in place as a precaution. However, I am not satisfied with the result. It is difficult to find the right release time. After expiry, the rubber thread hangs on the steel pin for too long, which makes the whole thing unpredictable.
I have now shortened the pin on one side to the minimum. It is slowly getting better and more predictable. As soon as the weather allows flying and the fields have dried out, the tests will continue. Depending on the outcome of the tests, I am also considering equipping the Secundus model with a ViscoDT.
About the photos:
Secundus_1: Activating the glow cord. The model is protected against heat and burn marks in the rear area (fuselage, rear wing) with self-adhesive aluminum foil.
Secundus_2: Overflight shortly before triggering.
Contester_1: Clearly visible on the fuselage side of the ViscoDT.
Contester_2: The spring steel hooks were left in situ.
ZIP -
Thanks for posting some more lovely pictures of your P-30 models.
In many parts of the western USA where I reside the risk of starting wildfires is such that the use of fuse DT's is out of the question. I suspect that the same is true in huge parts of Australia.
I have extensive experience with every type of DT with the exception of fuse DTs.
In my experience, the only way to reliably get a viscous timer to work in a DT system on a model airplane is by use of the so-called Badge Classis viscous timer that was designed exclusively for a DT system. This viscous timer used to cost around $20 US but sadly it is no longer in production. I was not able to get cheaper general purpose viscous rotary dampers to work reliably in a model airplane DT system.
The mechanical TOMY timer DT is extremely accurate and very reliable. However, it is a little heavy at 4-5 grams once adapted for this purpose. Also, I bought my TOMY timer DT timers that were specially engineered from wind-up toys to mount on a P-30 wing pylon or the side of an OTR fuselage. However, that supplier went out of business. I was never able to re-engineer the dithering arms of a TOMY timer myself.
I have now gone exclusively to using a BMK RDT with a 25 mA LiPo battery or a 50 mA LiPo battery. The total on-board weight penalty is only around 3 grams. You just push a button to terminate a flight when you have achieved a max, or if the model starts to head toward trees, a cornfield, a highway, etc.
So that people can be alerted to videos I have created showing how to implement various DTs I will start a separate topic.
I have now also gained some experience with Visco DT fuses. Last year, I had to really "feel my way" and wasn't entirely satisfied with them. The settings weren't easy to get right; either the flight times were too short, or the model had already landed by the time it detonated. With the smoldering fuse, I knew that 1 cm in length = 1 min. flight time.
This morning, after making some modifications, I made several flights. Weather: sunny, light breeze from the east, dry, and 10 degrees Celsius. Already weak thermals at 10:30 a.m. Flight times between 1.5 and 3 minutes, depending on the settings, model climbed up to 200 meters above ground at 1000 revolutions on the drive train (10 gr. 1/8" FAI Tan Super Sport). The Visco-DT triggered smoothly and cleanly and I was able to complete some nice return flights.
Peter
...
Peter -
Thanks for your flight report. It's nice to see you use half-tube winding outside the fuselage. That eliminates any need to use a blast tube as you know.
Are you sure your P-30 climbed to an altitude of 200 meters? Flying to 40-60 meters would seem to be more typical for a locked own P-30 without the aid of a thermal.
I thought I see a viscous damper on the side of your P-30 in one of your photos you posted before I replied. But you are using a fuse DT?
Hello Mike,
The DT used in the "Contester" was purchased as a bulk order in the USA under the name "ViscoDT." I don't know which manufacturer our colleague ordered from. We often do this to reach a sufficient total amount and then share the customs and packaging costs, which are only incurred once.
As far as the flight altitude is concerned, I could only see the model as a small cross during three flights. An RC-controlled glider with a telemetry module (we have a limited flight altitude of 150 meters at our model airfield) was circling at the altitude limit. The "Contester" flew significantly higher. The pilot of the RC glider was amazed, as was I, at the flight altitude of the free-flying model. The flight times here were around three minutes.
Next, I will equip the "Secundus" model with a ViscoDT as well.
Peter
Hello Peter
Would it be possible for you to take a photo of the ViscoDT by itself and post it here so that we know what it is like?
Peter (another one !)
Hi Peter,
I'm currently analyzing the flights from earlier this week and will post a report on them. It will include photos, and you'll also be able to see the ViscoDT I used.
Please be patient a little longer.
Peter