Ephemeris (oz11462)

About this Plan

Ephemeris. Free flight power model.

Quote: "If you think you're looking at a Sailplane wing on a modern hi-thrust contest flyer, you're not far wrong. Designer R Jess Krieser wants you to notice something else: UPTHRUST!

At first glance, 'Ephemeris' may not seem much different than most present hi-thrust free flight contest designs. However, careful study will reveal a very significant difference. This job flys with up-thrust! The balance of forces has been arranged to nullify the looping tendency to the extent that we can fly the airplane with its wing at an agle of attack of one to two degrees negative to the thrust line. Exact amount of negative inci-dence will vary slightly from one ship to the next; it's determined by flight adjustments. The significant accomplishment here is that we are able to operate with the airfoil performing in the realm of its minimum drag.

An examination of L/D curves on various sections will show that drag coefficients are at their minimum from zero to about six degrees negative angle of attack. The exact point at which the minimum drag coefficient is produced will vary from one airfoil to the next, but for the most part they fall within this six-degree range. Some may feel that the gain in efficiency through drag reduction of the airfoil is small. However, when all of the small gains made by refinements in a design are added up, they provide a definite edge in performance which can be important in winning a contest.

Another significant difference in Ephemeris is best appreciated when the airplane is flown. For this craft has excellent power-handling ability, and will handle the hottest engines without trouble. Some ships will give a straight-out climb under normal power, but when power is loaded on the old spiral climb becomes necessary to control the airplane. Not so with Ephemeris. No matter what power is applied, she seems to know only one direction - straight up. Recently flown with pure 'Blast' as fuel, it made the fastest climb we have ever seen. But the pattern of the climb did not vary from that obtained when using milder fuels. At present, we really don't know what the power handling limitations are of this design.

If anyone feels that Ephemeris resembles the Goldberg Sailplane (oz1058) they are correct. It was my long time admiration of the Sailplane's superb glide that led to development of Ephemeris. It all started in November 1961. I had obtained a set of Sailplane plans from Carl Goldberg intending to build it.

Carl and I lunched together one day and I was talking enthusiastically about my intended project. Since the Sailplane was one of his classic designs, I naturally thought he'd be enthused. But he asked me why in the world I wanted to build such as old airplane! I said that it was because I had never flown a free-flight contest ship that would out-glide the Sailplane. Carl felt that I was beating a dead horse, and that the Sailplane was an obsolete design which should be forgotten. He contended that one should always move ahead in the free-flight art rather than to build a design more than 20 years old. I half-jokingly asked if he'd be more interested if I made a hi-thrust ship out of it. He replied that this would certainly make a lot more sense, and would be more of an up to date approach..."

Ephemeris, Air Trails, March/April 1963.

This is a low resolution plan.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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