Small-Field Flying
Paul Bradley | [email protected]
Thoughts about blue foam for smaller projects
BLUE FOAM—not the fan-fold variety—has been used as a model-airplane building material since it was first introduced to the home-building industry.
This material has several properties that distinguish it from other types of foam used in modeling. It has a fine texture that makes attaining a smooth finish much easier. It can also be shaped with tools commonly used on balsa. There have been some nice models built from blue foam throughout the years in all areas of model aviation.
One drawback to using blue foam for some applications has been the form factor. It comes in blocks rather than in thin sheets. We do have BlueCor fan-fold sheets, but they are thicker than needed for many projects.
Modeler Steve Lawrie has bridged the gap between blue-foam blocks and thin sheets. He planned several new projects that were to be smaller in size. He decided that he wanted to use fairly thin sheets of blue foam as the building material, which would let him develop curved structures and take advantage of the foam's properties.
Steve has developed a process for cutting thinner sheets from blue-foam blocks. Typically his sheets are 3/32 and 1/8 inch thick. To give you an idea of what projects he is up to, take a look at the photos. You will find a neat V-1 Buzz Bomb.
The V-1 has a 25-inch wingspan and uses a Grand Wing Servo EDF40 fan unit. The model's overall length is 29 inches and flying weight is 5.7–5.9 ounces, depending on the battery used. Steve reports that the V-1 is slightly underpowered with two 1200 mAh Li-Poly cells but comes alive on three 1100 mAh cells. The only issue with three cells is possibly shortening the motor life, but heck, this is a Buzz Bomb. It does not need a long life. The airplane is definitely an eye-catcher at the flying field.
Steve has a B-17 in the works that uses his thin blue-foam sheets. I hope he will share a picture of that project when it is finished.
Take a look at the photo of the profile Grumman F7F Tigercat by Marc Stermer. It was built from 1/4-inch Dow BlueCor foam. This is becoming a common practice when building electric-powered profile models. It is also interesting to see the Grumman Tigercat showing up more often these days as a small-field modeling subject. Marc's project has several features that set it apart. He has adopted some of the structural-design features commonly seen in today's profile 3-D aerobatic models—specifically the use of a horizontal stiffener on the fuselage and nacelles. This improves the structural rigidity of the fuselage and adds a sense of depth in Marc's Tigercat. He has departed from the more common profile models by incorporating three-dimensional cowls. These are simply plastic containers that have the bottoms cut out. They definitely add eye appeal to the model and hide the motors well.
The Tigercat sports a 40-inch wingspan. This is an excellent size that allows the model to fly well and still be comfortable in the spaces typically used for small-field flying. The controls are aileron, elevator, and throttle. The flight controls use a pull-pull setup. Power comes from two Gen-II brushless motors from Model Aviation Engineering (MAE). Both motors are driven by a single brushless ESC. This is slightly different from the typical brushless electric-motor setup, but it works fine according to Marc and the people at MAE. The weight of the model without a battery pack is 12.5 ounces.
Marc uses a two-cell, 1320 mAh Li-Poly pack for casual flying and a three-cell, 1320 mAh pack for more spirited adventures in the air. The finish is Tamiya foam-safe spray paint.
One more structural note about the Tigercat: Marc used some carbon fiber in the wings to add bending strength across the span. He noted:
"In building the wings, I used two 1/4-inch strips of carbon fiber epoxied vertically in the wings. The vertical strips help the wing resist sagging. I also used some strips of carbon fiber flat against the wings across the center joint (on the bottom). I did not use any braces.
"The carbon-fiber spars seem to work well. I have not had any problems with wing flexing up and down, but it does exhibit some twisting (warping) since the motors are mounted below the wing. Although the wing will twist when you run the motors up to maximum speed statically, it doesn't seem to affect flying."
Thanks for sharing your nice profile Tigercat with us, Marc.
More offerings from Mark Miller
In my October 2005 column I recounted a nice scratch-built model from Mark Miller. As an accomplished scratch builder, he has a few more models in his hangar and has shared some with us for this month.
One is his Commando, built from 1942 Modelcraft plans. He wrote:
"The Commando was updated for RC and electric power but otherwise I stuck pretty close to the plan configuration. I originally had a GWS EPS 350C (shown in the picture), but because the airplane was tail heavy, I swapped it out for a 400. It was still tail heavy and it's taken a few iterations to get that airplane dialed in.
"With a 52-inch span and wing loading of less than 6 ounces per square foot, it's much happier in very calm conditions. My preferred way to fly it is to get it up to altitude, trim it for a wide circle, cut to roughly one-third throttle, put the transmitter down, and just let it free flight for a while."
A nice model, Mark!
In addition to this vintage Commando, Mark sent a picture of a model of his own design. Called the Little Red, it is a neat-looking profile airplane built from balsa sheet. He wrote:
"I've been having a blast with this little airplane. It's my own design: all balsa with a formed-sheet wing. With the struts, it's turned out to be very robust—okay, there have been a few 'incidents.' I spent more time painting it than building it.
"At 7 ounces and approximately one square foot of wing, a little Feigao brushless motor, and a three-cell 340 mAh Li-Poly pack, it's nicely overpowered and quite responsive. It's my 'okay, one more flight' airplane."
Again, nicely done, Mark. I sure see why Little Red is your one-more-flight airplane.
For those who like to build from kits, I want to pass along word that Dave Diels has added several new models to his excellent line of kits. If you are unfamiliar with Dave Diels kits, they are for high-quality balsa models intended for the rubber-powered free-flight community. That type of kit is also perfect for conversion to small-field RC flying.
The new kits from Dave include the Curtiss P-40B/C Warhawk and Nakajima Ki-84 Frank. Both feature 18.5-inch wingspans. That makes them ideal for the more compact venues or indoor flying.
The neat gear you have been seeing in Dave Robelen's column is perfect for use in models such as those offered by Dave Diels. For contact information regarding Dave Diels kits, please see the source listing at the end of the column.
Seen at BEST (Best Electrics of Southwest Texas)
Seen at the annual Best Electrics of Southwest Texas (BEST) fly-in was a small, multimotor model by Thomas Blakeney. He has been featured in this column in the past for his innovation and workmanship.
Thomas outdid himself at the 2005 event held north of Houston, Texas. His accomplishment this time was a wonderful rendition of the Republic X-12 Rainbow. In Thomas's eye, that is the most beautiful full-scale airplane ever built.
At 1/72 scale, his model certainly does justice to the prototype. It is carved from blue foam and features four Mabuchi M20 electric motors. The energy source is a two-cell, 250 mAh Li-Poly battery pack. The motors are wired as two pairs of series connections in parallel, so each motor only sees the equivalent voltage of one cell.
The flying weight is roughly 4 ounces. With a wingspan of 22 inches and all those propellers spinning with full enthusiasm, that little Rainbow looked great in the air. Thomas is planning to build a larger version of this attractive airplane in the not-too-distant future. I hope he will send me a picture when it is finished and flying.
As usual, nice work, Thomas.
Carl Hock and his converted FF Dumas Brewster Buffalo were also at the BEST fly-in. The model uses a standard GWS IPS motor/drive. It is nice and light and looks great with that skillfully applied camouflage paint scheme.
The markings are those Finland used when it employed the Buffalo as the country's primary fighter aircraft. Dumas kits make excellent RC-conversion subjects for small-field flying.
I have come to the end of this installment. Please feel free to drop me a line via e-mail or through the regular mail. My address is 32238 Spinnaker Run, Magnolia TX 77354.
I would like to see and share what you are creating during this building season.
MA
Sources
- Gen-II brushless motors:
- Model Airplane Engineering
- 5001 Bainbridge Ct.
- Lilburn, GA 30047
- (770) 925-8326
- www.m-a-e.com
- Dave Diels kits:
- Diels Engineering, Inc.
- Box 263
- Amherst, OH 44001
- http://pageproducer.acninc.net/dielsengr
Transcribed from original scans by AI. Minor OCR errors may remain.
