Palouse Ridge Runners R/C Newsletter
Pullman Ridge Runner Moscow
================================== March 2003 ======================================
By Don Hart
Hinges may be the most important component of model construction. Without strong, freely working, well aligned, properly installed hinges, our R/C planes won’t perform as we hope and may crash due to our failure to properly install these critical components.
The first hinges I used were made of strips of fabric tape, probably cotton, installed alternately to the top and bottom of opposing sides of a hinge line in an X arrangement. These hinges worked well on the U-control planes I was building in the sixties, but have been replaced by much better materials and methods. These hinges were installed using model cement, such as Ambroid. When the model was painted with dope, they became nearly invisible if installed properly.
Another early hinging method, one that works well when the control surfaces are made of balsa too thin to allow slotting for hinges, is to sew control surfaces on using thread in a figure 8 pattern. These hinges are very free moving and work well on small electric powered planes and gliders. This technique will also work well when a CA hinge breaks and you don’t want to go to the trouble of replacing it with another of the same type. You may have to drill tiny holes in the surfaces to prevent splitting the wood when a needle is used to install the thread hinges. The thread can be soaked with glue or paint to make them fuel proof.
The next type of hinge I encountered was the two-piece molded plastic hinge. These are made as two plastic parts with a metal hinge pin. These look much like standard hinges you might find on a cupboard in your kitchen, only much smaller. Slots for these hinges must be the same height and width as the hinge to prevent bulging and splitting of the control surface structure.
These hinges work very well, but are hard to install without getting glue in the hinge joint, preventing them from working properly. These were usually installed with epoxy. The plastic used does not bond that well with epoxy and must be roughened with sandpaper to get a good bond. These often have holes molded into the hinge blades to improve bonding. The leading edge of the movable surface must be notched to make room for the hinge joint if you want a tight hinge line.
A method of preventing two-piece hinges becoming immovable one-piece structures is to dip the hinge joint area in melted paraffin. Any epoxy that gets into the hinge joint will not adhere and can be easily removed.
The next incarnation of plastic molded hinges I used were similar to the two-part hinges only molded in one piece with a narrow thinned area at the center of the hinge acting as the hinge joint. These usually have holes molded into them to allow adhesive to hold them into the control surface. These were not as hard to install as the two part hinges, but were not perfect. These were also installed using epoxy. The hinge joint on these hinges does not require notching of the movable surface.
The next type of hinge I used, mostly on R/C gliders, were “monokote” hinges. These are made of two strips of covering material about one inch wide overlapped about ¼ inch with the adhesive sides ironed together along one edge – half with the adhesive side up and the other half with the adhesive side down. These strips are cut perpendicular to the joint into ½ inch wide strips and ironed to alternate sides of a hinge line in an X pattern, similar to the fabric hinges.
Monokote hinges work well, though they take a lot of time to install. You get a sealed hinge line and very free moving control surfaces. If you plan ahead, you can make the hinges nearly invisible, even if the top and bottom of a surface is covered with different colors of covering material. These hinges are ironed on. No glue is required. They work well on very thin surfaces.
A variation of the monokote hinges is the X-hinge. These are made of two strips of iron-on fabric covering sewed together lengthwise down the center with the adhesive facing outward. These are ironed to either side of the hinge line. The thread becomes the hinge. These are quicker than monokote hinges, but harder to hide unless you are using iron-on fabric that is applied over the top of the X-hinge. These also give a gapless hinge line.
An improvement on the flat two-piece hinge is the hinge point made by Robart. These are installed in holes drilled in the fixed and movable surfaces. These work well in surfaces that are thick enough to allow drilling without weakening the structure. These are usually installed with epoxy, requiring the same care as the flat two-piece hinges. To get a tight hinge line, the moving surface must be notched the width of the hinge point. Hinge points can be installed in locations other than centered on the surface, such as at upper edge. Holes are drilled at an angle to give the hinge solid material to glue into.
Robart also makes “hinge pockets”. These have set screws to allow hinge point hinged surfaces to be removed. Robart also makes hinge points with built in control horns, called “horny hinges”.
The most recent innovation in hinges is the CA hinge. CA hinges are made of a thin sheet of plastic with a thin layer of fabric bonded to each side. This fabric has a great affinity for CA glue. These are easy to install and are generally less messy than hinges requiring epoxy adhesive.
CA hinges are installed in slits cut with an exacto hobby knife blade. No material is removed from the slit. The hinge material is slipped into the slit. A pin stuck through the center of each hinge ensures that half of each hinge is installed either side of the hinge line.
CA glue dripped on each side at the hinge line is wicked into the slits cut into the material at either side of the hinge line. A drawback of the CA hinge is that if only a small amount of CA is applied, only the part of the hinge nearest the hinge line is glued, leading to hinge failure. A recent technique that increases this wicking action is to drill a 3/32 hole at the center of each hinge slot allowing CA to more easily penetrate the full depth of the slot.
CA hinges work very well for most uses, though they may not be adequate for some giant scale planes, especially on the huge rudder surfaces of large-scale aerobatic planes. Large hinge points or two-piece flat hinges may be required.
There are other types of hinges, including those used to build slotted flaps and Fowler flaps. Some can be purchased, but most require the builder to fabricate his own from appropriate materials.
I’m sure there are other hinge types available, but these are the ones I’ve had experience with.
One of the most important tasks in getting a good hinge system installed for a control surface is to get all the hinges properly aligned. A centering tool is used to mark the center line of both the fixed and the moving surfaces. These are made by Great Planes and Goldberg Models and are available from Tower Hobbies and other sources.
Dubro makes a hinging tool kit. Included are hinge slotting and centering tools. Hinge slots for two-piece hinges can be made with special slot making blades that are mounted in hobby knife handles. Tools are included that automatically align slotting tools and drill bits on the center line.
Another tool is the “Slot Machine” from Great Planes, a power tool that makes fast accurate hinge slots. Replacement blades are available or CA, medium and thick hinges.
Higley’s book “Mostly Mounting” describes hinging tools that are easy to make and that ensure that hinge slits for CA hinges are parallel to the hinge line and centered. A similar tool is the Formost Gapless Hinge Slotter from Fourmost Products.
Kit instructions will usually recommend the number and placement of hinges. Three or four hinges are usually required on elevators and rudders. Ailerons may require six or more, depending on their length. ARFs usually come with the hinge slits or slots already cut. Feel free to add more hinges if you think they are needed.
Tower Hobbies – hinges and hinging tools
Hobby Lobby – specialty hinges such as slotted flap hinges
Sig – CA hinges
Robart – hinge points for standard and giant scale
Harry Higley – hinging tools and instructions
By Don Hart
The Super Bowl Fly was a great success. There was no snow, but there was lots of good flying, warm weather (for January) and light winds. There was a low cloud ceiling at times as I discovered when my Midwest “Citabria” vanished for a short while at about 300 feet. A spin brought the model back down below cloud level.
Pilot Channel Model
Bertil Spence 52 Fun fly Hots.
Jeff Nelson 55 Hopefully fun Bipe , Firebird
Don Hart 44 Sirex Wasp, MW Citabria
John Sandell 27 Pizazz
Bob Bettcher 19 Electric
Al Culver 46 1/2 A racer
Mike Harris 20, 27
Brian Windsor 26 Trainer
Ben Troka 27 Heli, airplane
Howard Hosick 46 Air boat
Jordan Nelson 64 Fun fly Hots
As usual, great flying, great friends and great food. Many thanks to Jeff and Tawny Nelson for hosting this wonderful annual event.
By Les Grammer and Don Hart
The meeting was held at the Jack-in-the-Box in Moscow on February 4.
Richard Davis – Guest
Mel Colvin (VP) ran the meeting.
Joe Bolden reported that the new club trainer, engine and flight pack had been order and received. The total cost was $387. The plane is a Sig Kadet LT 40 ARF. This model will be used in a workshop (series?) to be put on by Joe Bolden for the Moscow Parks and Recreation Department. Joe passed around a lesson plan and a list of suggested tools and materials. The purpose of the workshop is to introduce new R/C flyers to ARF model construction.
The PRR Mall Show is set for March 7-9. Set up begins at 7pm on Thursday, March 6. Final preparations will be made at the next club meeting.
Spokane R/C Model Show and Swap Meet:
A reminder that the RC Swap at Spokane Community College is scheduled for Saturday, March 1. Contact: Anthony Worman (509)238-9157 or firstname.lastname@example.org .
A revised copy of the drafted By-Laws for the club charter was passed out amongst the members and reviewed for corrections, changes, etc. The summary of changes was noted by Dave Walker, who will take the results back, incorporate the changes, and forward to the Treasurer for inclusion with the club charter renewal paperwork.
Club Dues Are Due!
$40 in dues was collected from two members
Flying Site Search:
Bob Boettcher surfaced the possibility of flying at a site just north of Pullman. He was going to get some flyers together and go out and give it a try to see how things worked out. May want to be considered as a potential club flying field if things work well.
Joe Bolden reported there was no progress investigating a new flying site on the landfill east of Moscow. Efforts would continue to check out any possibility there.
Mel Colvin brought up the benefits for members to be qualified first aid, availability of cell phones, spectator control and the need for a fire extinguisher for the club field at John Sawyer’s farm.
Bertle Spence brought up the possibility that the club may be able to use the meeting room in the new Moscow Fire Station once it's completed. He will check into it further once Bruce Bumgarner is back up and about, as Bruce is believed to have contacts.
For the next meeting, it was suggested everyone bring something 'old' to show around to the group, so dig through those buried boxes folks! We will meet at the Jack-in-the-Box again in March.
Richard Davis has no experience in R/C, but would like to learn to fly R/C planes. He is a recent computer science graduate at U of I.
Dave Walker brought his World Models “Rambler 30” ARF, a low wing sport plane powered with an OS52 four stroke. He picked up this plane while he was in Arizona. Dave modified the decals to rename the plane “Rambo”. Dave says for $130 you get an excellent quality plane with pre-painted fiberglass cowl and wheel pants, and a painted pilot.
See this plane at http://www.theworldmodels.com/rambler30.htm