Wash in wash in wash out how do those wires route?

[Robert Lees]

Re: Wash in wash in wash out how do those wires route?

If you are bearing Paul, I think this is true!

(Hank still hasn't commented on my CDO)

[Hank Jarrett]

Re: Wash in wash in wash out how do those wires route?

Hate to do it, but I have no idea what CDO stands for in this context. Last time I used that acronym it was Command Duty Officer (The guy who is in charge and gets blamed when something goes wrong, I got lucky, my relief got blamed). Also have seen Collateralized Debt Obligation (don't ask ME for collateral!) Community Development Organization (sorry, Obama is on the way out).

Now if CDO is the same as OCD (Obsessive Compulsive Disorder here in the colonies) I am almost an expert on that! You should see the mower patterns in my lawn and vacuum marks on the carpet. I even line up my pencils by length on the desk. Then there is always the spreadsheet with all the incidence angles for my wings that I can't find. ;-)

Hank

[Robert Lees]

Re: Wash in wash in wash out how do those wires route?

Hank, you are so funny...

CDO is the same as OCD

BUT THE LETTERS HAVE TO BE IN THE SAME DAMN ORDER, DAMMIT!

[PA1195]

Re: Wash in wash in wash out how do those wires route?

Here's an engineering challenge...

Maybe someone with the skills could estimate the required wing twist in inches over a given span of the wing to achieve 1*, 1.5*, and 2* of washout?

I'm thinking something like the distance difference between an inboard rib (unknown) versus outboard rib (known: 1 5/16") from the front of the 30" level to the wing bottom like Taylorcraft produced. That assumes that the wing incidence when the fuselage is leveled is 3.8* at the wing butt rib. If it's not for some reason then the difference inboard versus outboard would become the new reference.

Might be useful sometime. This is what pilots do when it's too cold to fly.

Edit: It's easy to measure the dihedral difference of both spars. Maybe that's simpler than using Taylorcraft's level.

Gary

[Guest]

Re: Wash in wash in wash out how do those wires route?

Here's an engineering challenge...

Maybe someone with the skills could estimate the required wing twist in inches over a given span of the wing to achieve 1*, 1.5*, and 2* of washout?

I'm thinking something like the distance difference between an inboard rib (unknown) versus outboard rib (known: 1 5/16") from the front of the 30" level to the wing bottom like Taylorcraft produced. That assumes that the wing incidence when the fuselage is leveled is 3.8* at the wing butt rib. If it's not for some reason then the difference inboard versus outboard would become the new reference.

Might be useful sometime. This is what pilots do when it's too cold to fly.

Edit: It's easy to measure the dihedral difference of both spars. Maybe that's simpler than using Taylorcraft's level.

Gary

I plan to go to the airfield Monday and take a digital protractor, straight edge, wood blocbs and tape.

Using those materials I hope to make a fixture that can be held on the bottom of a rib with a point on the wood block contacting the rear of the leading edge then measure the angle of the straight edge.

Doing this on the root rib and the tip rib should reveal the twist in the wing (I hope).

A smart guy would both wings, if I seen one out there I'll ask him.

Dave R

p.s. do you want the twisted figured in inches of trailing edge drop?

[Guest]

Re: Wash in wash in wash out how do those wires route?

Dave, the way I remember washout is by lowering the tip angle, the air tends to "wash outboard" instead of straight back. Make any sense?
John

Hi John,

Thanks, maybe that will work for me, I want to think about why the flow would tend outboard toward the lower angle of attack airfoil.

Is that because the upper side of the airfoil has a lower static pressure for a low angle of attack airfoil compared to the higher angle of attack inboard airfoil ?

[PA1195]

Re: Wash in wash in wash out how do those wires route?

Hi Dave. I would have done all this before (excepting the math-derived equivalent of an actual measurement) if my wing planform allowed. Because my dihedral is 1.5* (of the front strut) due to the fuselage being widened during previous repair, I had no choice but to extend the rear strut to max to create 0-0.5* of washout.

However for others the Taylorcraft measurement is admittedly often only a starting point. Why? Well maybe design versus as-built fuselages and wings require something better than the universal "1 5/16"" spacing to achieve the washout the engineer intended. And what does that dimension relate to in degree of twist between specified wing stations? Piper spec'd the wash in degrees (2.5) from fuselage centerline to tip rib for example.

So, my thinking is to suggest the inboard vs outboard difference I discussed as a means to achieve the specified range of washout (and maybe pin down Taylorcraft's original design goal in degrees in the process). I was just thinking something like this: For 2* of washout aim for 1" difference between front of the level measurements inboard and outboard, the outboard being 1" less. Then go fly and adjust as required.

Tim will simply say fix it after flying and screw the numbers, but that still begs the original design question which I admit may be academic at best but still worth knowing.

Wouldn't trailing edge data require meeting an as-built of 1* dihedral at the front to have value? Did you mean rise versus drop? I suppose it depends on which direction your referencing.

Edit: I see this visually as an expanding triangle with the downward slope of the hypotenuse at the tip rib at some specified degree.

Gary

[Guest]

Re: Wash in wash in wash out how do those wires route?

Hi Dave. I would have done all this before (excepting the math-derived equivalent of an actual measurement) if my wing planform allowed. Because my dihedral is 1.5* (of the front strut) due to the fuselage being widened during previous repair, I had no choice but to extend the rear strut to max to create 0-0.5* of washout.

However for others the Taylorcraft measurement is admittedly often only a starting point. Why? Well maybe design versus as-built fuselages and wings require something better than the universal "1 5/16"" spacing to achieve the washout the engineer intended. And what does that dimension relate to in degree of twist between specified wing stations? Piper spec'd the wash in degrees (2.5) from fuselage centerline to tip rib for example.

So, my thinking is to suggest the inboard vs outboard difference I discussed as a means to achieve the specified range of washout (and maybe pin down Taylorcraft's original design goal in degrees in the process). I was just thinking something like this: For 2* of washout aim for 1" difference between front of the level measurements inboard and outboard, the outboard being 1" less. Then go fly and adjust as required.

Tim will simply say fix it after flying and screw the numbers, but that still begs the original design question which I admit may be academic at best but still worth knowing.

Wouldn't trailing edge data require meeting an as-built of 1* dihedral at the front to have value? Did you mean rise versus drop? I suppose it depends on which direction your referencing.

Edit: I see this visually as an expanding triangle with the downward slope of the hypotenuse at the tip rib at some specified degree.

Gary

Yes, I was hasty in my typing.

[Hank Jarrett]

Re: Wash in wash in wash out how do those wires route?

Guys, be prepared for some numbers ALL OVER THE PLACE when you use precision measurements on a Taylorcraft. Don't forget they were built to + or - 1/8" in most places and those errors can really ad up. My 45 fuselage was all over the place with longerons that looked like snakes. I spent months pulling it back to as straight as I could get it, then I compared to the 41 I bought (that flew great) and several other Taylorcrafts and ALL of them were twisted and crooked! All that mattered was that the tail surfaces were straight compared to the wing attach points and the firewall.

I have also torn down a pile of damaged wings getting spare parts for rebuilds. I can't tell you how many times I have seen ribs all put on spars with the same gaps all the way down the spars! The slop in the rib spar slot is so you can move the ribs up and down to get the wing SURFACE straight when the spar has some curve in it. As I said before, the twist in the wings I have WAS NOT constant! If you get all wound around the axle over the washout at each rib you will drive yourself crazy.

I measured each rib and it looked totally screwed up. When you enter the angles in a spread sheet and integrate the twist over the whole span you find it all pretty well evens out. You might need to take some second year Calculus to do it, but trust me, if you get it right at the root and at the rib called for in the rigging drawing you will get CLOSE. From there you can adjust it to fly straight. The small remaining error when you take the integrated twist times its moment arm to the fuselage is why some planes fall off on one wing and others on the opposite wing. It is not a big deal, you just need to know which wing YOUR plane will drop in a stall. It is happening because the stall progresses out the wing at different rates because of the changes from side to side in twist at each station.

Drude, if you take accurate angle measurements at each station I would love to see the numbers. NOT because it will change the way the plane flys, but just because I am kind of OCD about these things and am curious. If I can find my spread sheet I would like to see if the numbers fall within a statistically significant range. I am betting they will be very different numbers with insignificant impact on flight dynamics.

Hank

[Hank Jarrett]

Re: Wash in wash in wash out how do those wires route?

Guys, be prepared for some numbers ALL OVER THE PLACE when you use precision measurements on a Taylorcraft. Don't forget they were built to + or - 1/8" in most places and those errors can really ad up. My 45 fuselage was all over the place with longerons that looked like snakes. I spent months pulling it back to as straight as I could get it, then I compared to the 41 I bought (that flew great) and several other Taylorcrafts and ALL of them were twisted and crooked! All that mattered was that the tail surfaces were straight compared to the wing attach points and the firewall.

I have also torn down a pile of damaged wings getting spare parts for rebuilds. I can't tell you how many times I have seen ribs all put on spars with the same gaps all the way down the spars! The slop in the rib spar slot is so you can move the ribs up and down to get the wing SURFACE straight when the spar has some curve in it. As I said before, the twist in the wings I have WAS NOT constant! If you get all wound around the axle over the washout at each rib you will drive yourself crazy.

I measured each rib and it looked totally screwed up. When you enter the angles in a spread sheet and integrate the twist over the whole span you find it all pretty well evens out. You might need to take some second year Calculus to do it, but trust me, if you get it right at the root and at the rib called for in the rigging drawing you will get CLOSE. From there you can adjust it to fly straight. The small remaining error when you take the integrated twist times its moment arm to the fuselage is why some planes fall off on one wing and others on the opposite wing. It is not a big deal, you just need to know which wing YOUR plane will drop in a stall. It is happening because the stall progresses out the wing at different rates because of the changes from side to side in twist at each station.

Drude, if you take accurate angle measurements at each station I would love to see the numbers. NOT because it will change the way the plane flys, but just because I am kind of OCD about these things and am curious. If I can find my spread sheet I would like to see if the numbers fall within a statistically significant range. I am betting they will be very different numbers with insignificant impact on flight dynamics.

Hank

[PA1195]

Re: Wash in wash in wash out how do those wires route?

Great perspective Hank and thanks for sharing your experiences. Another question please...what determines the fuselage level in design? I know the horizontal stabilizer is used as a quick reference, but is there some other imaginary line through the fuselage? I've seen the term "thrust line" referenced and drawn front to back on the fuselage print PDF linked below maybe that's it? Then there's the question about how much does a design line parallel the stabilizers? Lots of room for slop I guess.

Gary

[Guest]

Re: Wash in wash in wash out how do those wires route?

I didn't record all of the left wing data because I got panicked after noticing a dent in the leading edge at the very tip.

The root rib angle on the left wing is probably a little large in real life there was slight depression in the LE where the block made contact. I measure the next rib but like I said panic set in and I did things out of order.

Will remeasure all ribs Hank when I go out to fix the tip tomorrow.

I believe the attached data is good, just incomplete.

Dave

[PA1195]

Re: Wash in wash in wash out how do those wires route?

Read the PDF Dave and thanks for the measurements. Question at some point when you're ready: How does your data relate to the 1 5/16" taylorcraft suggests on your plane? In other words given your washout what's the below wing distance per Taylorcraft's technique?

Gary

[Hank Jarrett]

Re: Wash in wash in wash out how do those wires route?

The whole fuselage is "leveled" based on the horizontal stab. In real life when they built the fuselage they clamped the wing attach fittings down and the firewall engine attach holes in the fixture, then made the stab attach level compared to those. Nothing else matters (within that 1/8 to 1/4" margin). If the fuselage looked like a banana with a step at the horizontal tail it would fly the same (except for all the extra drag and weight). An airplane is just the wings with the engine and tail attached accurately. The rest is just fairing to the aerodynamics. Level the plane with the stab, then the wing roots and the washout. Pretty hard to measure the thrust line. Fortunately for it to get moved takes quite a wallop and there would be lots of other damage then so you would know.

One thing to remember is that when you rebuild a plane you rig the tail surfaces horizontal across the span and vertical on the fin with the wires. Don't get all worried that they move after a few flights, just re-rig them perpendicular and square. The tail surfaces WILL MOVE and have to be "dialed in". It is normal.

Hank

Great perspective Hank and thanks for sharing your experiences. Another question please...what determines the fuselage level in design? I know the horizontal stabilizer is used as a quick reference, but is there some other imaginary line through the fuselage? I've seen the term "thrust line" referenced and drawn front to back on the fuselage print PDF linked below maybe that's it? Then there's the question about how much does a design line parallel the stabilizers? Lots of room for slop I guess.

Gary

[Guest]

Re: Wash in wash in wash out how do those wires route?

Read the PDF Dave and thanks for the measurements. Question at some point when you're ready: How does your data relate to the 1 5/16" taylorcraft suggests on your plane? In other words given your washout what's the below wing distance per Taylorcraft's technique?

Gary

Hi Gary,

The 1-5/16" and 30" level schematic that Hank posted is a method that sets that particular rib or location on the span at an incidence angle of 2.5 degrees so I guess it all seems reasonable.

Mine measured 1.55 and 2.0 at that location.

Dave R