Swept forward t/e question!

Quite a few flapped designs with swept forward t/e's show one piece flap joiners - this doesn't seem the ideal way to get smooth controls - what are your findings?

Check out this thread. I entered "Lucky Box" in the Search function. Steve

http://www.clstunt.com/htdocs/dcforum/DCForumID1/6421.html

>Check out this thread. I entered "Lucky Box" in the Search
>function. Steve
>
>http://www.clstunt.com/htdocs/dcforum/DCForumID1/6421.html

The "Lucky Box" is one route. Al says he has been doing them for years without this feature if the sweep isn't too great. There apparently is enough "give" in the system to allow it. Same with dihedral. You can also use separate horns, but this, too, can cause its own set of problems including linerarity.

funny ya'll mention this. I've been thinking along the lines of a swept wing flying wing,swept back but same problem, and I was contemplating a system.

So, here's my idea, instead of a pushrod running from a bellcrank, I was thinking of a round pully with a kevlar thread around it, connected on each end to a slider...I can't describe it too well, but the idea came from the knob on a radio I tore apart when I was a kid. I figure you convert to linear motion before hooking to the flaps ( or elevators in my case) I figure if built properly it shouldn't have any slop, and should be very smooth. I also tinkered with the idea for running a pull-pull setup on a "normal" airplane this same way. Right now it's all just thought running around in my head. I have already designed the wing, 27.5 sweep from the centerline, 30 in. span and just over 240 sq. in. wing area. I'm debating where to put the engine (.049), front or back. I've never tried a pusher, that may be too much to try all at one time.

none of this is glued together yet, one piece notched spar and ribs, all just slid together with a few pins. I can't work things out in my head I need the real thing to look at. The bell crank will be behind the spar in the center, then the lead-outs have to pass through the spar at some point, so I'll probably try running them together. What I haven't worked out yet is where they will exit the wing, and how far they will be in front of the tip. This is the prototype, I want to work on the sweep 'til I can get the lead-outs to leave the wing tip instead of in front of it.

Looks like the amount of sweep would put the AC towards the back of the wing center section chord. Where are you planning on putting the leadouts. Seems like they'll have to be towards the back of the wing tip. What is the fuel system you have designed for the pusher engine.

Don't they make little Himes joints for R/C cars? Seems like they would work well on angled horns.

About the swept wings, you'll need extra elevator power. The apparent mass/aeroelastic damping effects of having the wing area ahead and behind the CG will slow the pitch rate compared to a straight wing.

>Don't they make little Himes joints for R/C cars? Seems like
>they would work well on angled horns.
>
>About the swept wings, you'll need extra elevator power. The
>apparent mass/aeroelastic damping effects of having the wing
>area ahead and behind the CG will slow the pitch rate
>compared to a straight wing.

It looks very much like the Sportwing design which is very squirrely on launch, but loses the ability to turn once it gets up to speed.

I'm sorry, I didn't mean to change the topic, so I'll start a new topic to try to answer some of the previous thoughts from you guys.

Austin-

I'd suggest that you first find the M.A.C. and neutral point (center of lift) of your design (you can use the calculators on the Palos Verde site: http://www.palosrc.com/instructors/mac.htm). Then choose a c.g. position giving you an adequate "static margin" (distance ahead of 24% point om M.A.C.). Finally, use Pete Soule's line rake program (http://www.geocities.com/AMA271/Aeronotes/pwscol.htm) to determine the leadout exit position.

I should mention that dihedral effects from pronounced sweepback cause rolling and yawing moments that complicate manuevers. Bill Netzeband has been contending with these while refining his "Fierce Arrow" design and reports that his range of useful c.g.'s is small.

Being a tailless aircraft enthusiast of long standing (I have compiled a 450-500 pp. bibliography on the subject, currently between 6th and 7th edition - sold out), I applaud your experiment and wish you well and a lot of enjoyment. FWIW, I still think that a mildly forward-swept wing with adequate fin area has all the advantages for a tailless design.

Tony,
I have built a couple planes now with swept forward TE and one flap horn. The Ares is this way, and Aaron has flown his numerous flights with no problems in all conditions. The Man shows, in his video from Bob Hunt on building I Beam wings, to cut the TE just flat enough fo rthe horn to sit in contact with out bending. Don't know *why* it doesn't bind, etc., but it works real good.
I talked to Al Rabe and Keith Trostle about the set up on Al's Bearcat II, and it has dihedral and swept forward TE. Only use one horn, and it works.
Bill

Bill Werwage let me examine the flaps on his "1962 Ares", and I found them to have neither binding nor noticable self-centering tendencies. They fell of their own weight. A club member's Sterling "Yak-9" also had very free controls. I too have trouble conceiving how this can work (seems mechanically impossible), but each has the specified straight flap horn connector wire. My "Yak-9" has a bend, as in the original kit, and it has a pronounced self centering force. Based on what Al said, "lucky boxes" should be OK, but it seems that enough freedom exists in the nylon hinges to make mildly swept hinge lines quite free, when the connector is not bent in the center.

aslong as there is some lateral slop in the plastic horn, and some room for the wire to move, the movement will be free. if you try real tight metal stuff it will have to flex.IMHO MM

The horns used in the Ares are the older Jim Hunt double upright CSC horns, no slop, no binding. Doesn't seem to make sense, but it works.
That's from Billy Werwage and Keith Trostle who do it that way. I just follow along!
Bill

In my Ares, I didn't get the area in front of the horn wire just right and it has a slight bind and a tendency to go to neutral. This makes it a little hairy in some maneuvers. I asked Bill about this and he said also to put the horn arms at the very edge of the flaps. But by cutting the swept part of the TE straight and placing the horn arms at the edge of the flaps, no binds.
However, on extreme sweeps, I would use two horns with swivel ball connectors.

I have a rather fun model I call the Frite Streak. It is, of course Orange and Black, and based on a Brodak Lightning Streak 1/2A kit. I won the kit in the Christmas raffle, and thought it would be boring to build stock.

Cutting to the chase, it is now a forward swept flying wing, with 15 deg per panel sweep. The elevators are driven off a single horn and wire system with miniature "Lucky boxes". It is extremely smooth, even with that drastic an angle. The trick was to embed the center, straight wire inside the angle of the TE root, and have the driving ends extend out perpendicular to the hinge lines. So we have a wire with the ends canted out 15 degrees. These are entrapped between ply sheets with enough room side to side to absorb the angle change. Absolutely no binding in the system.

If you analyze the motion you can see that the ends only move in and out a tiny amount over the 20 degrees or so of elevator motion, and the friction due to that is nil.

>>However, on extreme sweeps, I would use two horns with
>swivel ball connectors.

On extreme sweeps, I strongly recommend not using two horns. Instead, use a lucky box as explained by Larry Renger here and others.

Unles you use some method to avoid differential throws and flex in the pushrod system to drive the split horns (it can be done and Ron Burn is the only one I have seen that has solved the problem), a split horn arrangement on the flaps (and elevators, but particularly the flaps) is not a good solution.