Rigging Question?

[peerlesscowboy]

The wingtips are washed in or out by screwing the treaded plug at the outer end of the rear lift struts in or out, within the approx. 1" range of the slot. Screwing the plug t'ward the outer end of the slot lengthens the strut thereby washing the wingtip "out", screwing the plug t'ward the inner end of the slot does the opposite, shorten/wash in?
Question?
Is there a "correct" place to start? I started by washing them both "out" the limit and then raising the "heavy" wing by screwing the plug on the heavy side in enuf' to make the a/c fly wings level.
I've seen another T-craft that had the wingtips both washed "in" the limit & then apparently one side screwed out enuf' to level, is one way more "correct" than the other? Or should they be more in the middle of the adjustment range? Or does it matter?
John C. Saubak
1940 BC-65
N24433
ser #1770

[alwaysoar]

Re: Rigging Question?

Here's what the service manual says:
"To check the rigging of the wings and tail, stretch a cord across the wings at the front spar and level the ship with a line level placed over the center of the cabin.Stretch a second cord across the wings at the rear spar and level with a line level. The rear strut adjustment is used to accomplish this. The bolt at the point of attachment of the wing strut with the wing fitting must first be removed. A long screwdriver may be be used to move the adjustment nut as required." Follow that? There's more:
"In flight testing, if the airplane flies either wing heavy, the rear strut adjustment may be used to correct this by washing the opposite wing out, or the heavy wing in."
"If the airplane flies nose heavy, both wings may be washed in, or if tail heavy, both wings may be washed out for correction."
Translation?: Fart around with it until you can fly it hands off with the trailing edges of the ailerons in line with the trailing edge of the wing and the wheel centered.

[Guest]

Re: Rigging Question?

The wingtips are washed in or out by screwing the treaded plug at the outer end of the rear lift struts in or out, within the approx. 1" range of the slot. Screwing the plug t'ward the outer end of the slot lengthens the strut thereby washing the wingtip "out", screwing the plug t'ward the inner end of the slot does the opposite, shorten/wash in?
Question?
Is there a "correct" place to start? I started by washing them both "out" the limit and then raising the "heavy" wing by screwing the plug on the heavy side in enuf' to make the a/c fly wings level.
I've seen another T-craft that had the wingtips both washed "in" the limit & then apparently one side screwed out enuf' to level, is one way more "correct" than the other? Or should they be more in the middle of the adjustment range? Or does it matter?
John C. Saubak
1940 BC-65
N24433
ser #1770

Hi John,

if I was doing it I would start with each wing washed out as much as possible, screw threaded all the way out. Then wash in as required to get level flight. I think you may get a little more speed that way because the effecte angle on incidence should bee a little smaller. Dave.

[VictorBravo]

Re: Rigging Question?

Well, yes, but... is there supposed to be any wash-in or wash-out in the Taylorcraft wing rigging? If the airplane flies straight with ZERO washout is that OK with the manual, or is it supposed to have X degrees of wash-out? Can you wash-in the wings and be OK with the manual??? (this is an unsafe condition, btw)

The airplane will be a touch faster and climb better with zero, but it will be safer and more stall/spin resistant with a degree or two of wash-out. The vortex generators may shift this equation a little bit one way or another. Since I am ready to start fine tuning my airplane rigging, I'd like to know what the official degree of wash-out is if any.

Bill

[Edwin Otha]

Re: Rigging Question?

Hello all,
I have had good luck using the following proceedure.
I use a profile board to conform to the bottom of the wing, and using a smart level on the flat side I zero the level. I then move to the rib outboard of the strut and adjust the rear strut to get a zero reading. At this point I consider the wing flat, no wash. After test flying I shorten the strut on the heavy wing,as required.
EO

[peerlesscowboy]

Re: Rigging Question?

My thinking with washing the tips out the limit as I've done on mine was; that SHOULD (?) make the stall more prone to start at the wingroot thus less prone to develop into a spin? I s'pect wash-in vs wash-out might also effect how deep into the stall the a/c will go with full up elevator, but I can't quite visualize in my mind which way?
Just by eyeballing it, looks like if the plug is in the center of adjustment the wing is prob'ly zero wash, no twist either way?
John C. Saubak

[jgerard]

Re: Rigging Question?

Even though these planes were jig built as they get older and parts get replaced you may find that one rear strut is all the way out and the other is all the way in just to get the proper measurements. This does not guarantee that it will fly straight. The straighter ships always fly better and faster because there is less drag created by washing one wing in or out more to keep the wings level or compensate for a heavy wing due to repairs. Tails get twisted also and it's just as important to make sure the vertical is perpendicular to the stab. Because of the fixed front strut dihedral is not adjustable so if you keep chasing your tail when rigging check that the wings are level with the string stretched across the top and then check and adjust your stab and fin to be plum to the wings. Since I have been jigging up my fuse getting ready to replace rotten tubes I have been going all over the thing with a 36" level to see what I can find. I have it mounted upside down and have leveled it using rear spar carry through and stab attach tubes. The spar carry through and stab attach points are level but the lower longerons are not square to the top ones and 1/2 way between the cabin and tail there is some twist in the fuse. There the lower longerons are level and the top ones are slightly off although extremely minor. Then back at the tail the top longerons are level again and the lower ones are off a wee-bit. At-least the important areas (wing & tail) are plum to each-other. None of the twist is more than an 1/8" difference between sides. The plane flew better than any of the other Tcrafts I have flown so I guess its fine. One thing I am trying to figure out is the angle of incidence of the tail and wing to the thrust line (assuming thrust-line = center line) Since the book tells you to level the plane with with the stab that is how I have it in the jig, the thrust line is not parallel to the tail even though my service manual says its supposed to be. The tail appears to have some positive AOI and the wing has even more AOI. Anyone know what I should be looking for? I may not have my TL sting in the right place, But it sure seems like it is. My drawings are for a prewar airplane and either there is a typo or missing reference line regarding the distance from the station at the lift handle to the TL (9 1/8") or the Post war planes are different in that area. Everywhere else I get the proper measurements or dam near.

Jason
N43643

[Forrest Barber]

Re: Rigging Question?

OKAY lets all go back to Taylorcraft basics.... please use the Web site . www.taylorcraft.org and explore all that is written there.
A few of us spent a lot of time & effort back in 2002 to post the frequently asked questions in two methods...right now it is starting to rain & I have to transfer some ships around. soooo start off with http://www.taylorcraft.org/faq-rev01.html read it ALL then go back to other stuff under technical resources... also read the disclaimer under the web site:
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The proper rigging is in the BC12D service manual.... IF the ship is conforming to Type Certificate ( Airworthy) she has to be rigged according to that document, IF it is not on the site WE will get it on the site. More wash out or less wash out leads to an inaccurate "minimum trim speed" 60-70 mph. that is full nose up trim with trim tab at proper angle .
Please READ the book!! any book

[VictorBravo]

Re: Rigging Question?

[B]
The proper rigging is in the BC12D service manual.... (snip)
that is full nose up trim with trim tab at proper angle .

Forrest, thanks for bringing this up... I have a question or two on this subject I hope you can address:

I have a pre-war airplane with the little external trim tab. It doesn't work as well as I think it should. I cannot trim it nose-down enough at 95 mph cruise.

(background data) A CURRENT, recent weight and balance shows the airplane well within the EWCG and flight CG. No problems there.

The controls all work. No warps or bends in the tailplane, no horrific repairs to the longerons, etc. The plane's pretty straight.

The wing wash-out or wash-in is within a degree or two of zero by visual inspection. Not nearly enough one way or another to overcome the trim tab.

(problem) I cannot trim for level flight at cruise, the force of the air pushes the trim tab back towards neutral against the friction force keeping it in place. I can trim it for level flight at low speeds, but above 85 or 90 mph it just springs back. On landing I can't get it to slow the airplane down to final approach speeds either, but the trim tab stays in the full nose-up position... the trim tab is stalled (inverted) IMHO.

As an old broken down model airplane builder, I understand the cause of the high speed problem easily... the pivot rod is located too far forward on the trim tab. That would be easy enough to fix (legality aside), but then there's the problem of flying around with a trim tab deflected 45 degrees up in level cruise flight. Drag bad, no drag good!

The low speed problem is clearly that the trim tab is not producing enough downforce at the tail, because it is too small.

The BC-12D instruction manual would probably not address the pre-war trim system in any detail. I do not have a BL-65 maintenance manual to my knowledge, but I'll look in the big box of stuff. The certification basis is different anyway if I am not mistaken, being certified to CAR 4 instead of FAR Part 23. So the trim, stability and control requirements might be different, and the trim tab may not have had to perform the same degree of function as the post-war airplanes.

Sooo... can you shed some light on the factory trim system specifications and functions for a 1940 BL? What operational functions is the pre-war trim tab SUPPOSED to deliver? Are you supposed to be able to achieve Va at cruise power with the trim? Are you supposed to be able to achieve Vs or "best glide" with it power-off?

Because of the poor performance of the trim tab on this particular airplane, it is very tempting to "repair" the trim tabs about 20% bigger and with another handful of "dynamic balance" area. This repair can thankfully be done with the un-molested originals hanging in dry storage on the hangar wall rather easily

[Ragwing nut]

Re: Rigging Question?

Although I have never flown a prewar with the flying tab, I have talked to many people and they all say the same thing. The tab runs out of effectiveness about 90-95 mph. Probably why they changed it on the De Luxe and postwar models.

The book says to level the thrust line to rig the aircraft. If you use the firewall as a reference for vertical, it will get you very close. I start with 1* of wash in the wings and adjust from there.

Mike

[3Dreaming]

Re: Rigging Question?

[QUOTE=VictorBravo]Forrest, thanks for bringing this up... I have a question or two on this subject I hope you can address:

I have a pre-war airplane with the little external trim tab. It doesn't work as well as I think it should. I cannot trim it nose-down enough at 95 mph cruise.


(problem) I cannot trim for level flight at cruise, the force of the air pushes the trim tab back towards neutral against the friction force keeping it in place. I can trim it for level flight at low speeds, but above 85 or 90 mph it just springs back. On landing I can't get it to slow the airplane down to final approach speeds either, but the trim tab stays in the full nose-up position... the trim tab is stalled (inverted) IMHO.

This is same thing I found when I had my pre war BL. Tom

[Gary Snell]

Re: Rigging Question?

Ditto for me too. Also have a BC65 conversion from a BL. I ended up putting a fixed tab on the elevator to cure the problem.

[peerlesscowboy]

Re: Rigging Question?

I too, have a pre-war (1940) BC-65 conversion from a BL-. same cure as Gary Snell, put a fixed tab on the elevator. Then adjust (bend) the tab so the little "flipper" adjustable pitch trim under the horizontal stabilizer is streamlined to the airflow at normal cruise.

John C. Saubak

[Forrest Barber]

Re: Rigging Question?

Most closed cowls will not trim with flipper, look at it sometime, it is full deflection trying hard to do its job.... ADD a fixed tab. I will get specs, and give a report on proper rigging and minimum trim speed....

[Guest]

Re: Rigging Question?

Here's what the service manual says:
"To check the rigging of the wings and tail, stretch a cord across the wings at the front spar and level the ship with a line level placed over the center of the cabin.Stretch a second cord across the wings at the rear spar and level with a line level. The rear strut adjustment is used to accomplish this. The bolt at the point of attachment of the wing strut with the wing fitting must first be removed. A long screwdriver may be be used to move the adjustment nut as required." Follow that? There's more:
"In flight testing, if the airplane flies either wing heavy, the rear strut adjustment may be used to correct this by washing the opposite wing out, or the heavy wing in."
"If the airplane flies nose heavy, both wings may be washed in, or if tail heavy, both wings may be washed out for correction."
Translation?: Fart around with it until you can fly it hands off with the trailing edges of the ailerons in line with the trailing edge of the wing and the wheel centered.

Interesting, my manual reads exactly the same.

My manual is a series of copied pages. The page it is on has the number at the bottom blocked out by what appears to be tape and the top of the page is also blocked out by tape.

I wonder if the top contained the name of a different aircraft type? It came from Air Service Caravan in New Bedford, Mass.

I have had the manual for years and suspect that it's a bunch of stuff thrown together rather than an actual manual. The pages look like they all came from something else.

However a few pages after the one that matches yours there an unnumbered page that has an unnumbered drawing of that claims to be from Taylorcraft. It describes that the horz. stabilizer should be level and then place a 30" level at the first full rib from the tip about 26" inboard and the bottom of the wing surface below the front spar should be 1-5/16" above the bottom of the wing surface below the rear spar. This particular drawing does no look like other drawings that appear to be legimate tcraft drawings and it has no number or date.

That seems to contradict the first description so I suspect that at least one of them is not accurate.

Dave.