Here is an in-flight shot of Rob's Telemaster with Fowler flaps extended
In this issue...
BOG Review
Legal Eagle?
Fowler Flaps
Wing Flexure
Proposed Rule Change (see last page for diagram)
From The Editor
by Price Dempler
Thanks for the submissions everyone This issue is full of good stuff. Check it out!
As a reminder, any submissions for the Hear Ye! must be submitted by the 23rd of the month preceding the following month's issue. Please contact Price Dempler with any questions. Thank you!
B.O.G. Review
By Sam Andreas, Secretary
The July meeting of the Board of governors was called to order by the President at 7:40 PM on 7/18/95. Present were the Treasurer, Secretary, and 9 B.O.G members. The Chief Helicopter Instructor was also in attendance. Topics discussed were as follows:
1- The Treasurer provided an update on the clubs financial status as of 6/30/95.
2- The Refreshments Fund was increased by $150.00 for the balance of the year. This fund provides free refeshments at our general meetings. The vote was unanimous.
3- The Treasurer noted that the board did not take into account the fact that each years allocation of funds is used to pay for the previous years' President's Dinner. Therefore the existing fund has been exhausted. The board voted unanimously to add an additional $250.00 to the fund for the balance of the year.
4- The board voted unanimously to allocate $300.00 to keep the Port-a-Potty until the end of October. The vote is contingent on the rental company providing the necessary liability coverage for damage, loss etc. The board also voted to keep a Port-a-Potty at the field from April through October as a general rule provided the above insurance is maintained.
5- There was a lengthy discussion over whether an SFA charter will or will not provide additional liability insurance, above and beyond that already provided by our AMA charter. All further discussion on the subject has been shelved pending receipt of expert advice from an attorney.
6- A proposal was put forth by the Helicopter Committee to add a Heli-Circle onto the existing runway. The board agreed in principal to an addendum to the club safety rules addressing the use of the circle. The board decided to publish the proposed addendum in this issue of Hear-Ye along with an illustration for clarity. This will provide all club members with an opportunity to examine the proposal before any decision is made. This topic will be discussed at the August general meeting and if it meets with general approval the board will vote on it. If enough board members are present to provide a quorum, the vote can take place after the general meeting.
7- Joe Weiser volunteered to organize a Club Fun Fly to be held on September 30. Anyone wishing to volunteer their services should contact Joe.
The meeting was adjoured at 9:35.
Note: the next meeting ofthe B.O.G. will be held at the church on August 15 at 7:30PM
THE BOARD IS LOOKING FOR LEGAL ADVICE
Despite all the dialogue concerning the pros and cons of adopting an SFA Charter, the one fact that everyone agrees on is that no one on the board is an expert on insurance law. We require the assistance of someone who can analyze the liability coverage of both the AMA and SFA and advise as to whether or not dual charters would increase our liability coverage. If anyone in the club happens to be an attorney or insurance professional your assistance would benefit the club immensely. Please contact one of the Club's officers.
Fowler Flaps
by Rob Caso
A couple of guys have asked about the flaps and other modifications I have incorporated in my recently built Telemaster so I thought I'd do a "how to" article. I like the 72 inch Telemaster as a platform for any type of significant modification since in it's basic version it's a large trainer with good flying and handling characteristics, light wing loading, easy to see in the air and it's not bad in reasonably windy conditions. Of course, I wrecked my last one screwing around with full flaps on a very windy April day! My father and I between the two of us have built at least 6 of the 72 inch Telemasters, the last 5 of which were destroyed by the pilot (or was it the radio, or...)
Aside from the flaps, the major modification from the plans are as follows: conventional LG, wingbolts (no rubber bands), 1 inch longer nose behind fire wall, 3/4 inch wider fuse at midsection, increase rib cross-section 1/8 inch (thicker wing), eliminate lifting stab, double area of elevator and rudder (or triple for rudder), larger ailerons with bellcranks, triangulate stab /fin with bracing struts, wing struts - probably redundant, at least .60 2-stroke engine for STOL. Finished weight was 8.5 pounds with an OS .90 four stroke.
The Flaps
I won't go into a long aerodynamic dissertation on why and how the flaps work for two reasons; first, I don't know anything about aerodynamics and second, it doesn't really matter - close is probably good enough. And they do work. On a breezy day, a full flap, full power take off will require only about an 8 foot run and sometimes less.
My flaps are about 20 x 2.5 inches each and are hinged about 3/4 to an inch or so below the bottom surface ofthe wing. This allows the flap to detach from the wing in essence creating another, smaller wing. The resulting gap causes air that would normally slip undeneath the trailing edge to go up and over the flap, lowering the pressure on the top of the flap and creating lift (and drag). This is close to how a fowler flap works.
Construction? The diagram tells all. Note that the trailing edge of the wing is tapered to correspond to the leading edge ofthe flap - it is critical for the flaps to be able to lock against the wing in the up position for normal flying. The taper should be built into the rib cross section in the wing. A round cross section would be more aerodynamically sound and produce more lift and less drag, but the angular section works OK and it's easy. The hinges are simply control horns reversed and bolted together (socket cap screws, washers and nylock nuts: 2-56 or 4-40) at the hole furthest from the bottom of the wing. The horns must have an "L" cross section as opposed to a "T" section to allow them to nest together when the flaps are closed.
The flap pushrod exits through the trailing edge ofthe wing and utilizes a heavy duty clevis which is in turn connected to a piece of nylon bellcrank embedded and pinned in the leading edge of the flap. This piece will actually slide inside the wing through the hole in the trailing edge when the flaps are closed. Slick! I recommend that ball links be used throughout the internal flap linkage in the wing to eliminate slop in the mechanism. Also, a nylon bellcrank will not be strong enough to be used with the flaps since these flex easily. Make your own crank using hard 1/16 ply and use a brass bushing/4-40 screw as the pivot point. The corner of the bellcrank should be built up with ply and the bushing should be inlaid there. Don't skimp here. Also use 4-40 pushrods for all linkages. A surprisingly small amount of servo movement is required for a large amount of flap travel - you'll have to experiment. My flaps move about 40 degrees or so.
So how do these things work? With a little breeze and at idle you're flying a powered kite - cut the throttle, drop the flaps slowly and point into the wind with the rudder. The control surfaces must be big and have large movements to allow them to move air at low speeds.
Short landing? Do a higher than standard landing approach, going to full flap and 1/4 throttle on base leg. Turn slowly to final (max 30 degree bank) pitch up slightly to bleed off speed and throttle back to idle using aileron to keep level and elevator to adjust glide path. You should be at full elevatorjust at touchdown. Tree in your way? Come in high over tree at idle, apply full flap, point nose straight down, flare and land - you'll pick up only a little speed in the dive! Full flap take offs will require a bit of down elevator during climb out!
Center of Flexure...
by Lew Roosa
After I watched Rob Caso float his modified Telemaster around the field the other day. we got to talking about wing loadings and structure. We all know that the pressure distribution on the basic airfoils and rectangular wings most of us build results in a lift force concentrated approximately at the 25% chord position. We put our main spar at or very close to this point for this very reason plus the fact that this is usually the thickest part of the airfoil and we can use a deep spar cross section. What some may not realize is that this also lines up the center of lift with something called the center of flexure. This is the position along the chord where a concentrated liftload causes the wing to bend but not to twist. Designers have to be careful here, for torsional stresses have ruined many a wing. Mother Nature figured this out a long time ago, and she placed the quill of the bird's feather at about the quarter chord.
Back in WWI, most planes had two wings each with two spars and numerous struts and diagonal wires in tension - that created a strong box structure that withstood both bending and torsional loads quite nicely. Although unseen, there were horizontal diagonal wires in both upper and lower wings that completed the box structure. Monoplanes of that period had lots of wires and wing braces to control the torsion problem, but they were never as strong as the biplanes.
In the 30's, as engines got more powerful and speed became the thing, designers faced new problems. Wing loadings went up as the wing areas got smaller. As lift is a function of the square of the velocity, the planes still flew, although takeoff and landing speeds shot up. The introduction of riveted metal wing skins to replace the old fabrics solved most of the problem for they absorbed the shear loads arising from any tendency to twist.
Again, in the push for speed, designers started to make the wings thinner to reduce profile drag and they ran into another nasty problem. When a pilot wants to bank to the right, he raises the right aileron which causes a downward force at the trailing edge that pushes the wing down. Of course the opposite effect is happening on the left. If the designer did not provide enough torsional rigidity, at high speed this downward force on the trailing edge could twist the wing such that the leading edge rose. This increased the angle of attack locally, wing lift increased, and the plane actually banked to the left! This is called aileron reversal and many planes and some pilots were lost before everyone figured out what was going on.
PROPOSED ADDENDUM TO CLUB RULES
The new rule concerns the creation of a 100 ft circle with its center 50 ft east of the northwest corner of the runway, the circle will not be cut into the grass therefore no additional graes cutting is required. The Heli-Circle will allow helicopter pilots to fly a circular pattern around themselves with the following provisions and restrictions:
