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Author Topic: F1D Junior Model  (Read 254 times)
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« on: November 27, 2017, 08:55:43 PM »

There has been some concern about how to introduce young (and not so young) fliers to the F1D class.  The usual method is to start with “simpler” classes and proceed along to F1D.  One problem with this method is the rule restrictions of many classes, especially the material and design limits, make for planes that are not only difficult to build to the minimum weight and the needed stiffness without careful and costly material selection but also are difficult to set up and fly with the basic design limitations.  For example, LPP class planes may be easy to build but their flight characteristics take expert attention to fly at the highest level.  F1L’s are nice planes but the very best wood is needed to build a minimum weight plane with the stiffness needed to fly well especially in higher sites.

If the usual F1D techniques of braced motor sticks and, perhaps, boron or carbon reinforcements are applied to a planes with dimension similar to that of an LPP, a plane can be built to near the F1D minimum weight using hobby shop wood.  And, where lighter wood is needed, say for the motor stick and prop blades, most wood of the lighter density but only average or below average stiffness can be used with the motor stick bracing and the slow flying airspeed and propeller rotation rate.

The F1D Jr. model was designed to fly and respond to setup changes in ways very much like a full size F1D.  However, the solid motor stick and tail boom and the reduced  wing and stab area along with the molded sheet wood prop blades rather than film covered outlines make for a plane that is much more rugged and easier to handle than a full size F1D.  In addition, the wood need not be the very stiffest as the bracing and possible use of carbon or boron reinforcement make the model more than stiff enough for the flight airspeeds.  The models built so far are made from wood bought at the local Hobby Lobby craft store. And this includes the prop blades cut from a 5# balsa block bought at the same store.  The model was also designed to be easy and quick to build.   Two local high school girls, experienced only in building SO helicopters, built their planes during three sessions of two and one half hours each.

The model is similar in length dimensions to an LPP.  The model was also designed to fly times similar to that of LPP’s but to use only 0.4g F1D sized motors.  This has been borne out by the local girl’s flights.  The model also provides a path to more advanced techniques as a rolled tube motor stick and tail boom can be added as well as a vp prop hub with outline and film prop blades.  But, at first, the builder should not worry about getting down to the minimum weight.  The model can easily be built by anyone who has built any AMA class duration plane including LPP and A6 as well any Science Olympiad plane or helicopter.   The point of the model is to have a plane that is quick and easy to build, fun to fly and, at the same time, have good performance and relatively long flight times.

The plans and build notes (as well as the kit notes for some kits that were produced) are available and have been posted on the INAV website:


Models similar to this F1D Jr will be allowed to fly in the Jim Richmond Open at West Baden.  The JRO is limited to F1D class planes only.  To make it easier for non-F1D fliers to fly in the JRO, I will make a limited number of molded prop blade sets as well as sub 5#, 7”-7.5” motor sticks available to those who will build an F1D Jr and enter to fly at the Jim Richmond Open next March at West Baden.  The nominal cost is $15 including Priority Mail shipping to US destinations.  I can be contacted at:

leop at lyradev dot com

Tapio Linkosalo
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« Reply #1 on: November 28, 2017, 01:38:50 AM »

There is already a F1D-beginner class. It used to be called F1D-beginner, but more recently it was re-named to F1M. The models can be built to be competitive without exotic materials, using only balsawood. Hobbyshop wood goes all through the construction, except that the body tubes are more easily made from special indoor wood. I have made models with fuselages sanded down from hobbyshop stuff, it is possible, but a bit tedious.

Here in Finland we have multiple F1M's, and only a few F1D's, so the models share the airspace. Collisions are common, but an F1M-F1D collision poses no greater risk to the latter than does a F1D-F1D -one. That is, no damage usually takes place.

F1M is easier to build, as the minimum weight is 3 grams, double that of a F1D. The model is almost as big as a F1D, so flying weight is not much larger. The construction is quite similar to a F1D, so tubes need to be rolled for fuselage. For the rest of the construction, balsa wood is sufficient. You guys in the US may be distracted with Bills carbon construction, but I may assure you that it is totally unnecessary. Wing spars cut out of 1mm balsa sheet, and 2.5 to 3 mm tall at the wing center section, are good and stiff for consistent flying. I have never used anything but balsa for my F1M wings.

Another advantage of F1M is that the motor minimum weight is 1.5 grams. Thus the rubber quality and handling are not such super-critical as they are for F1D. Impressive flight times can be achieved with recent Super Sport rubber. But, the class allows the use of a VP prop, so you can also learn the secrets of building and adjusting such delicate instrument before moving on to F1D. The higher minimum weight allows the F1M VP mechanism to be built larger and heavier, and easier to handle (300+mg is perfectly OK) that those for F1D, so you can manage that more easier. No exotic materials needed for F1M VP mechanism either, even nylon M2 bolts are quite sufficient for the adjusting screws!

For the rawest beginners, we have made a further restricted class, F1M-limited, for our local use in Finland (the rules made along similar class in Germany): restricted length of fuselage, so solid wood can be used, and ban of VP, so solid balsa prop is OK. That makes a nice path from SciOly type models towards F1D: first a F1M limited, then a larger F1M with fixed prop, then replace the prop with VP, and you are almost ready to move onto F1D. I have given courses on the three steps of F1M's here in Finland, and we have a couple of new guys on the climb towards the top tier...

Later this summer I had a drawing of my F1M "course model" published in INAV. Let he heartily recommend that as a good and solid design for a beginner, as on a previous course we had 15 guys build them over a weekend, and almost all got their models flying on Sunday afternoon. Most flew straight off the building board, and several models made over 10 minutes on their first outing. With a fixed pitch prop, in a 18 meter hall!
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