I have started, or should I say rebuilt a Bristol M1 in the Toon, or Toonish style. My first attempt was with foam board and foam cups I had collected. The fuselage was getting heavy for my design criteria and wasn't yet ready to finish, so it got trashed. I began the next TFPF build after making a tube of FFF for the skin of the new fuselage frame. The pictures I have taken should give the reader a good idea how to build a light weight "stick frame" to add strength for the fuselage skin of FFF or another thin foam type.

Notice the build up method used for the TFPF is nearly identical to standard build-up methods used in balsa wood aircraft model kits. The primary difference is not so much the construction method as it is the materials used. The blue foam disks are cut from foam board, which is normally 1/2" thick and sold as rigid insulation. The stringers are parts from a bamboo curtain or shade. The bamboo strips are very strong, thin, and add very little weight to the construction. The round and colored stringers are also sold as parts of a bamboo window curtain. The color on the round stringers were part of a picture airbrushed on the wood.

The rolled FFF you see behind the fuselage will become the skin. Glue is painted on the foam disks and the stringers, as per the standard balsa wood airplane model kit before the FFF is applied. The FFF will be cut into "rings", or parts of rings and rubber bands will hold the rings in...Continue Reading

I have the Arupy II well on it's way to mounting the electronics, but before I get too carried away with completing the RC model, I need to give it a few throws to find the COG. Once that is established and marked, I can place the craft on a balance jig/fixture/beam/board and place the electronics to preserve the COG. If I do this well, there should be no need to add lead weights to correct for the best flight COG.

I am using the TFPF (thin foam park flyer) building process and testing my skills at MFPB (more fly per buck) techniques. I had not heard of pre-mixing GG (Gorilla glue) with water (50/50) before application, so I will give that technique a go on the next project. The last time I pre-mixed GG with anything before application I used rubbing alcohol, which is what I use to clean up excess GG that has foamed up beyond where I want it to be.

In the pictures you should be able to see I used thin, mid-quality balsa wood on one side of foam parts and around the edges of the FFF wing. The purpose of the balsa is to stiffen the FFF beyond what is normal if glued foam-to-foam. I also used some thin plywood that came in a bag of shapes from the craft store for the landing gear achors and firewall. Notice the very thin fiber glass and epoxy to strengthen the wood for the landing gear mount.

The extra epoxy and very thin fiber glass reinforcement is designed to spread the impact of not-so-gentle landings. Other wise there is a risk the landing gear wire could...Continue Reading

A basic NutBall or Arupy cutting plan for a disk of foam is nearly the same. Both park flyer designs start with a disc and the cuts make a Pizza Box Flyer (PBF) with rounded wing tips. One can also start with a PBF and add rounded wing tips and use either an elevator or elevons (elevator cut to provide a right and left half) for control. If you already have a flying PBF and want to make it look more like a NutBall, add rounded wing tips. You can also add rounded edge material to the front and elevator until your RC model looks like a flat, round ball. To make an Arupy out of a PBF you only need the rounded tail (elevons, elevator) and wing tips, but the leading edge LE) of the wing tips will have a flat part. (See prior pictures)

The first decision is how large to make the disk out of your favorite foam board material if you aren't converting a PBF. The decision will most likely be based on the electric motor you plan to use. An electric motor of 40 to 80 watts can power a 1/2" thick by 18" diameter disk, up to a 22" disk. That is assuming your foam is light-weight and doesn't exceed the recommended weight limits for the motor when all electronics and hardware are installed. Placing a larger battery pack in the model often means heavier, will change the COG (center of gravity), and motor power requirements.

The kV rating of the motor will affect the flying characteristics of the model, either as a slow flyer for training purposes, or as a sport flyer able to handle acrobatic manuevers and ribbon-cut or full-contract combat. Many motors of higher kV ratings drain the LiPo battery pack faster than motors with a lower kV rating of the same weight class and size. Part of this tendency is likely due to the way the RC pilot manages the throttle control. It is possible to fly the same model of the same weight with a higher kV rated motor a little longer with proper throttle management, but there are limits.

The Nutball was a beast with attitude from the beginning and it liked to nose dive if a turn was attempted. Finding the COG (center of gravity) for the model proved tricky and was probably due to the nature of EPP foam (floppy). The stiffening carbon fiber rods (one front and one near elevator) were very thin (1mmx3mm) and easy to break. The front strip had broken in three places by the time I opened the slot to determine why the front had become so floppy. Later I used GG (Gorilla glue) to install a bamboo rod (barbecue) behind the carbon fiber strip. I cut the slot for the bamboo rod with a hot cutter, and being new to the tool, the slot cut was uneven.

I used too much GG and the foaming glue made a mess of the repair. It didn't look very good, but it did stiffen the front of the flyer. I kept making more repairs and modifications until the 1300 kV Blue Wonder (BW) could no longer power the RC model off the ground. I changed to a slightly heavier motor with a 1500 kV rating and the old NutBall was given new life. Finding the COG became an issue and changing the location of the 2s LiPo battery pack (7.4 VDC) helped. I ended up gluing two round map pins in the bottom of the model to use as balancing points before each flight. Getting the COG correct with a heavier NutBall was a challenge.

Each time I repaired the craft the COG would change and it would be a task to balance the flyer correctly. In the end I cut off the front "nose" of the NutBall just behind the carbon fiber strip and the bamboo rod and made the flyer I named an "Arupy". Unfortunely the heavier RC park flyer had gained more weight and finding the COG proved difficult. The challenge was to get the model airborne without control problems causing another crash. It is times like these a guy wants a wind tunnel to test his model and find the best location for the COG. I haven't retired the Arupy yet, but I will soon since I am constructing other foam flyers.

Some pictures of the old EPP Park Flier kit - 20" NutBall. The front kept taking damage and the section has gained more than an once in glue, a bamboo barbecue stick, puddy, modifications, spray paint, and Sharpe coloring. By the time I had learned to add some up stabilizer before attempting a turn, the craft was no longer a floater due to weight gain from repairs and changes. My skills repairing EPP foam have improved and I am venturing into the world of other plastic foam types. I plan to stay in the Park-flyer sized RC models for a while.

Even though I had flown other RC flyers I had purchased as RTF (ready to fly) and ARF (almost ready to fly), the NutBall EPP kit was a good trainer for a simple, and affordable flyer with an attitude. When I first started flying the 20" NutBall, the craft was nose heavy, and I learned to position the 2s battery pack to adjust the COG (center of gravity). After reading the NutBall thread, (took longer than I had expected), and making a number of recommended improvements, the park flyer became easier to fly. The craft did continue to nose down vigorously if I implemented a turn. The only way to keep altitude was to add up elevator before starting the turn. Placing the motor slightly above the wing level with thrust angle adjustments gave the craft milder flight characteristics.

Notice the old NutBall looks more like a SnowBall with a flat front "Arup" style leading edge wing. I cut off the "often...Continue Reading

A search for images on the Internet should provide some of the following. I used the search phrase "arup aircraft".

I thought it would be a good idea to start a "blog" about my interests, one of which is currently the 1930s flying wing design called an Arup airplane. The original craft did have a rudder, but not much else that would suggest a tail. What I did after noticing a few offerings on the Internet about the Arup designs was look at my well used and battered Nutball (kit) made of EPP foam and thought I could remove the "many times repaired" front portion. The result would give me a straight leading edge (LE) and with the removed 20%, what remained did hint an Arup design.

There were a number of craft built as an Arup aircraft and it appears each had minor changes. One of those changes was short wing tips that could be rotated, giving the effect of ailerons. The planes were called flying wings, but some insist that was not a proper labeling of the aircraft type. One of the reasons is the odd shape, primarily a half, shallow circle, or only 40% of a circle, was the shape that comes to mind when I see the aircraft from a top view. One could say the shape is more like part of an elipse. Another interesting fact is the aircraft were flown safely and could land at lower than normal airspeeds.

My well used Nutball also was given ground skids, or almost floats as is often seen on the Snowball foam flyer. My skids were made from six thin layers of EPP glued together to form ground clearing skids placed near the wing tip joint to protect the propeller from...Continue Reading