Monday, June 3, 2013

And Bob continues with comments on the SAM RC glider rules:

Now to SAM rules
[Towline gliders are listed in the: SAM Approved Designs List ~ Rubber, HL Glider and Towline Glider]
SAM handbook: 9SG. O/T Glider (Not an engine powered event):-
A. Any glider designed or kitted before 1947, scaling OK.

B. Maximum wingspan = 120 inches, no minimum wing loading.

C. Precision event: 20-minute total of three flights (or less).

1. Time over 20 minutes, deducted from 20 minutes.

D. Tow release starts the clock.

E. High start or winch only. Max extended length = 700 feet.

F. Launch equipment supplied by CD or pilot.

For the 2013 Champs, the CD, who runs the event has added the restrictions:

1. High start only- I do not know why, I will discuss with him. A nice variable speed winch can save a lot of wings.

2. No aileron control, which is OK with me.

Bob Galler's Floater

(All text and photos by Bob Galler)

The Floater first appeared in the Model Glider Design book by Frank Zaic first printing 1944 but the Floater appeared in 1942 as a design. The original had a span of 72" and as it appeared in the MGD (page123) it had only dihedral but was changed to polyhedral with each wing section an equal 17- 3/4". In the Model Aeronautic Year Book for 1959-1961 Zaic pontificates on his excellent design and its progression on pages 148-150. The stabilizer was an unusual 4" by 29". Frank used a very short coupled fuselage because at the time the AMA rules required the (L/100)2 cross section applied even to gliders, which meant the longer the fuse the more bulbous it became. After 1946 the AMA was convinced to drop this preposterous rule, (Editor's Note: We all know about preposterous rules - even in this day and age.)  I do not know much more about the history thereof. Be that as it may, Frank also used a NACA 6409 with flat bottom, which is actually a no number airfoil just for the Floater. Another unique characteristic is that Frank used an incredible 6 degrees of positive attack on the wing to tail, and according to him this, along with the narrow tail and short, body gave the Floater its bouncy glide, especially in tight circles. According to several old timers that have built and flown the Floater free flight, it works that way just fine and was competitive until the A2 gliders took over after 1947.

My RC Floater is scaled up to 93" span with a wing area of 855 sq. inches and a tail that is as long as the tail on the Dallaire (36") but only has a chord of 5". The wing airfoil is extremely thick for a chord of 10". For RC I reduced the wing angle of attack to 4 degrees, kept the balance point similar, just behind mid chord. With RC you do not have to circle so tightly to keep in a thermal, but could if needed. And the first glides look really good, although nose heavy with my 1000 mAh nicad pack which weighed 9.1 oz! I have a nimh pack of 6 cell 1500 mAh on its way from Tower Hobbies that weighs 1 1/2 oz less. I kept the tail and rudder as light as possible and used good wood for the longerons and covered with natural Micafilm and Sig Stix-It . A one piece continuous span of Micafilm give the tail real strength. Anyway landings are gentle. Overall the Floater is weighing in at 2 lbs 10 oz, for about 7 oz/sq ft. The RC gear is :

Rx- Spectrum AR 400. Elevator servo is a HK 4 gram and rudder is a Spektrum micro digital of 7.2 grams both rear fuse mounted. A Slide switch is installed in the fuse side near the battery/ballast compartment. A six cell 1500 mah hour receiver pack operates the servos with authority! The elevator only has minimal travel about 20 degrees, but the rudder has a large throw and is of very good proportions. And ,oh yes, the wing is 2 piece or it doesn't fit in my truck cap. I used .332 dia steel rod inside carbon tube as the main joiner and a 1/4" rod of aluminum for the rear joiner and made the first 3 ribs of 1/8 inch ply. The carbon fiber lengths are encased in epoxy. If that breaks then I want to see how! With a one piece wing I am sure it would deduct 4 oz overall from the wieght of the Floater. The fuselage is covered with a combo of pearl white Micafilm and red Micafilm. The wing similar. Sig Stix-It used throughout. The Micafilm is the original good stuff. I have no more red to speak of but have a good supply of the white and some silver on its way from my supplier .
I give credit to:Harry Klarich for the short kit, and myself for the balsa and trailing edges. Ha Ha. And I used the Bob Holman jigs for building the fuselage nice and true.