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Building aircraft frames using Spray Mount and Transparencies

       (No t-pins and no building board)

Fred Matthis yfm1@macatawa.org Oct 7,2002

Design considerations used on the "Fred Fred 99 1/4 pint" gliders

Fred Matthis yfm1@macatawa.org Oct 7,2002

       Elliptical wing shape

       Sweep back of wing

       V-tail

       Balsa selection per aircraft member

Protecting the aircraft in transit and storage

       (No hanger rash or accidental wing folding)

Chuck McLanis chuckmc@iserv.net Oct 28,2002

Tying lubed rubber motors and having the knot be perminate

       (Oops! missed the mass launch, the rubber motor knot came undone. )

Chuck McLanis chuckmc@iserv.net Oct 28,2002

 

 

 

 

• Building aircraft frames using Spray Mount and Transparencies Fred Matthis yfm1@macatawa.org Oct 7,2002 Materials 3M Spray Mount - Artist's Adhesive
• Stratacore - plastic board, looks like coregated card board
• Copier Transparencies
• Wax paper - Cut-rite best

 

• Preperation
  Copy the section(s) of the plan(s) that you need to build on. In that the transparencies are 8.5x11 inches you may need to use more than one transparency copy to include the complete part.
• If more than one transparancy is used, cut the overlap off.
• Spray a light coat of the Spray Mount on the Stratacore, where the transparencies will be placed.
• Place the transparencies and smooth out.

 

• Making the airframe Spray a light coat of the Spray Mount on the transparencies that are on the Stratacore.
• Place a sheet of wax paper over the transparencies and smooth out.
• Spray a light coat of the Spray mount on the wax paper.
• Place the Stratacore/transparencies/wax paper assembly on a flat surface, table, etc., wax paper side up.
• Place the airframe parts, on the wax paper, where they fit on the plans. The Spray Mount will hold the parts in place. If it dosn't, spray a little more on. Work with it until you get the feel of how much Spray Mount is needed.
• Glue the joints with the glue of choice. A glue that wicks into the joint is needed, thin CA, etc..
• When glue is cured, lift corners of wax paper to remove airframe.
• Repeat the process for additional parts.

 

• Storing Stratacore/transparency assembly Remove the wax paper and replace with a fresh one, do not spray.

 

• Comment The reason you have to use the transparency of the plan, instad of the paper plan is: Using Spray Mount on paper plans will cause the plans to expand. This is becuase the paper is made of wood fibers. If the airframe parts are pre-cut, they will no longer fit.

 

Design considerations used on the "Fred Fred 99 1/4 pint" gliders

• Fred Matthis yfm1@macatawa.org Oct 7,2002 Elliptical wing shape The wing shape is elliptical and the airfoil shape is varied fron the root to the tip such that the lift plot is elliptical. Highest at the root and and lowest at the wing tips. The elliptical lift pattern provides a very stabel flying wing.

 

• Sweep back of wing The 30 degree sweep back of the wing provides the effect of the wing having a significient physical dihedral. The wing also has a small physical dihedral. The wing's effective dihedral is the sum of the dihedral fron the sweep back, and the physical dihedral. Sufficient dihedral causes a free flight plane to right it's self, if a gust turns it upside down. The small physical dihedral helps to initate the righting process.
• A siginificent advantage of the sweep dihedral is: The projected horiziontal wing area is much greater than the projected horiziontal wing area when the wing is at 30 degrees. Result: much lighter wing loading for the same size of wing.

 

• V-tail The V-tail is used for 3 resons: One less part - saves weight and time.
• Alignment of the V-tail and wing is done with the airplane upside down and the wing tips and V-tail tips touching, glue. Wala! instant, no hassle perfect alignment.
• Just looks cool! I like them.

 

• Balsa selection per aircraft member Hand selection of the propergrades (weights and strengths) of the balsa, for each member, permits 60 plus percent of the planes to be properly balanced, as built. This means additional weight, to balance the plane, is not needed. This reduces the unit loading on the wing (oz. per sq.ft.).

 

Protecting aircraft in transit and storage

• Chuck McLanis chuckmc@iserv.net Oct 28,2002 Hi Fred , At the indoor fly-in you asked if I would submit something for the 'hot ideas " section of your web page and here it is. I thought about what hint I would pass along if I was only allowed just one, you know , the one great tip that would help the most people, the most often. After giving it some thought here's what I came up with == When you make an airplane don't take it anywhere or leave it sit around with it being in a box, with a cover. === Simple , but important. I've seen many a good plane damaged by the elements or by other models just "dropping in" , damage that wouldn't happen if the model was properly stored away between flights and while in transit. This has been particularly evident at the Science Olympiad where I have witnessed students carrying their models across a windy parking lot out in the open with the predictable results- folded wings ! Don't let this happen to you- building the carrying box is part of the process of building a plane ,you won't regret it.
• Tying lubed rubber motors and having the knot be perminate
• Chuck McLanis chuckmc@iserv.net Oct 28,2002 After you have properly lubed the rubber motor getting a knot to hold can be a problem, right? The simplest way to cope with this is to wrap a bit of scrap yarn into whatever knot you use. Most every one knows someone who does yarn type needlework and they will happily part with the 1 or 2 inch long pieces trimmed from the latest sweater. The yarn commonly used is a 4 ply worsted and if you separate the plies you get a nice small fuzzy string-like piece to wrap into the knot. When pulled tight the knot is not coming untied - ever. Works for me with even the best Dow 33 super slippery silicon lube.
  By the way , more on lubing rubber for motors later but for now just get some Son of a Gun car care spray , squirt some in a sandwich baggie, drop in the motor , knead it around a bit and go fly. It doesn't have to be wet when it's on the plane, it's the powder that does the trick. Re-lube after every 3 flights or so. And remember to keep your precious rubber supply out of the air, light and heat. This has gotten way too long -so much for "a few words" CMcL

 

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