Planes Worth Modeling – Buhl Pup

Front view of Buhl Pup showing radial engine

Front view of Buhl Pup showing radial engine

One of the interesting and engaging aspects of model aircraft design is selecting what type of full scale aircraft you wish to recreate with a radio control model. We know there are literally countless types of aircraft we can select from. The following is a discussion of my thought process with selecting an airplane to model, using the Buhl Pup as an example.

The first thing I look for is an airplane with “character,” some level of visual appeal. There are some aircraft that just do not invite a second look. While the definition of character will vary from person to person, it is something to take into account.

Side view of Buhl Pup light aircraft

Side view of Buhl Pup light aircraft

An important aspect of full scale aircraft candidate selection is an assessment of how difficult will it be to translate the design into a successful RC model. There are some designers who can literally work miracles with scale construction. I generally take a more conservative approach. Areas of a full scale design that will cause significant challenges, such as a complex canopy, usually cause me to consider another choice.

When you take this approach you can quickly zero in on designs that lend themselves to model aircraft structures. A great example of this is the Buhl Pup, a single place light sport airplane.

The Buhl “Bull Pup” was designed and produced in 1930 by the Buhl aircraft company. As the Great Depression in the United States was starting to take its full effect, the idea was to develop a personal aircraft at the lowest cost in an effort to keep the company financially afloat.

The Pup had a cockpit for just a single pilot. It’s length was 19 feet and it had a wingspan of 30 feet, with an empty weight of 550 pounds. The 45 hp engine gave a top speed of 98 mph. Around 100 Buhl Pups were built before the company went out of business due to the weak economy in 1932. Sadly, all of the remaining aircraft were sold at half price.

In-flight shot of Buhl Pup showing conventional in-line engine

In-flight shot of Buhl Pup showing conventional in-line engine

An interesting side point regarding the Pup. In an effort to promote sales the company offered a range of wingspans. There was a faster version,with a bigger engine and a wingspan of two feet less. In addition there was a longer range version with an additional two feet of wingspan. Perhaps this is not too different compared to our own RC model building modifications?

The good news in this saga for model aircraft designers is that the Buhl Pup makes an excellent candidate for a radio control model.

The plane has reasonable tail and tail moments for center of gravity balance. The landing gear construction is straightforward and the upper cabane struts should be easy to fabricate.The Szekely three cylinder radial engine is the perfect fit for this airplane and can add large visual appeal to an electric powered model.

Side view of nicely restored Buhl Pup aircraft

Side view of nicely restored Buhl Pup aircraft

Perhaps the greatest incentive for drawing up a set of CAD plans on the Pup is the wing location. The constant chord wing will use just one size of rib. But the huge design advantage is that the wing is located essentially on top of the fuselage, easing any number of installation issues.

Szekely three cylinder radial engine

Szekely three cylinder radial engine

A final bonus from building a Buhl Pup model is that the aircraft is not overdone. There are any number of Piper Cubs at a local flying field, but not too many Pups.

While there are numerous considerations that can be taken into account with selecting an airplane to model, these are some that I think about when selecting a scale design.

This is precisely the approach I followed when I decided to draw up my 1912 Blackburn Type D design. Good nose and tail moments, interesting landing gear arrangement and character for sure. Plans are available here!