Strut angles

[jstall]

Fellow Crafters, I'm sure you have heard about the infamous "STRUT ANGLE" where the struts angle back from their attach point to the Fuselage attach point. There has been much discussed in the past about this, and Alaska Airframes even went so far as to post procedures for measuring this angle, as apparently there are differences out there between aircraft examples.

My question then is: Have we come to any general accepted value for this angle, or are they just a varied as the aircraft they represent.

My angles are Right wing 4.0 degrees Left wing 4.4 degrees. I would be interested to hear what other Crafters have found. I'm taking the front strut not rear.

J Stallings
Taylorcrafter
Alva, OK

[Guest]

Re: Strut angles

Buy a set from Univair and don't worry about it.

My opinion is that it's a self inflicted wound by AA.

My guess is that you won't find two airplanes that need the 8 degree angle.

Putting hard hat on now.

[jstall]

Re: Strut angles

Buy a set from Univair and don't worry about it.

My opinion is that it's a self inflicted wound by AA.

My guess is that you won't find two airplanes that need the 8 degree angle.

Putting hard hat on now.

Sure could be as far as I can tell my left front strut is about 4.5 degrees and the right
one is 4.0

The distance from leading edge to spar is 9 inches, does anyone know the distance
the strut attach point on the lower fuselage distance back from datum or prop??

JS

[Guest]

Re: Strut angles

Measure parallel to the floor from some known datum referenced location like the instrument panel, front spar attach...

[Guest]

Re: Strut angles

I think that you will find it to be about 15" aft of the spar.

[Mark Bowden]

Re: Strut angles

The aircraft datum is the leading edge of the wing.

Measure your feature like you were going to do a weight & balance.

Chock the wheels.

Raise tail to level the aircraft, horizontal stab is level with a carpenter's bubble level running fore to aft. Then level the wings by adjusting air pressure in tires. Wing level is measured on the frame tube at the top of the seat back.

Tape a plumb bob string on top of wing skin and let hang down in front of where you want to measure (at fuselage attach point and outboard strut attach point). Now you have a common reference point for all features of interest.

Close the doors so drafts don't move the plumb bob around.

Mark

[Guest]

Re: Strut angles

Its about 115" along the spar from the spar butt to the attach point for the lift strut.

The lower lift strut fitting is going to be about (14/2)" aft of the main spar, I think I over estimated before.

So the anticipated angle between the lift strut axis and the main spar axis will be on the order of arcTan((14/2)/115).

That works out to about 3.5 degrees.

But that is estimate of only the angle between the axis-es.

There is another angle that may need to be included and that is related to how far off axis the lift strut end fittings are. The worst that can be the (aprox.) is arcTan of the strut width divided the 115" dimension from above.

Its more likely that it is not that much but may 1/5 of the strut width divided by 115. That comes to about arcTan[(3.37/5)/115] or .3 degree. It could be a plus or a minus.

I did not estimate from the attached picture I did it with parts and ruler but I did use the picture to guess where the main spar "fall" along the line between the landing gear attach points. I guessed half way, i.e. I divided 14 by 2. The landing gear attach points are about 14" apart.

Initially I made a mistake on this an forgot to divide a number by 2! Eek, I just corrected it.

Looking at my errors and estimates it seems to me that it is more likely that I overestimated the angle between the axis than underestimated. Real measurements on the plane will be better.

To make 4 degrees the lower lift attach needs to be 8" aft of the spar, to make 2 degrees it needs to be 4" aft of the spar.

[jstall]

Re: Strut angles

Its about 115" along the spar from the spar butt to the attach point for the lift strut.

The lower lift strut fitting is going to be about (14/2)" aft of the main spar, I think I over estimated before.

So the anticipated angle between the lift strut axis and the main spar axis will be on the order of arcTan((14/2)/115).

That works out to about 3.5 degrees.

But that is estimate of only the angle between the axis-es.

There is another angle that may need to be included and that is related to how far off axis the lift strut end fittings are. The worst that can be the (aprox.) is arcTan of the strut width divided the 115" dimension from above.

Its more likely that it is not that much but may 1/5 of the strut width divided by 115. That comes to about arcTan[(3.37/5)/115] or .3 degree. It could be a plus or a minus.

I did not estimate from the attached picture I did it with parts and ruler but I did use the picture to guess where the main spar "fall" along the line between the landing gear attach points. I guessed half way, i.e. I divided 14 by 2. The landing gear attach points are about 14" apart.

Initially I made a mistake on this an forgot to divide a number by 2! Eek, I just corrected it.

Looking at my errors and estimates it seems to me that it is more likely that I overestimated the angle between the axis than underestimated. Real measurements on the plane will be better.

To make 4 degrees the lower lift attach needs to be 8" aft of the spar, to make 2 degrees it needs to be 4" aft of the spar.

But Drude===14/115 = .1217 -tan then is = 6.9 degrees or am I missing something
Talked to Univair, they cut there strut at 3 degrees, mine sure appears to be more like 4.5 to 5. w/o taked the thing off and really measuring it just no way of knowing but after the
deal I went thru with Harry his were -0- degree and didn't even come close to fitting
I can't make that mistake again just too expensive, actually my struts are very good and have passed twice now and will again this summer.

JS

[Guest]

Re: Strut angles

JS, it should be (14/2)/115 that's same as 7/115.

Not 14/114.

Make sense?

I have Univair struts they fit fine.

Ask them for a guarantee.

Dave R

[articfox]

Re: Strut angles

Not sure if it was mentioned but I noticed the angular difference was from the shorter compression struts being mixed up with the longer compression struts during the rebuild or during the manufacturing of the wing. If the longer strut was used between the spars where the attach fitting are, the spars will be pushed further out making for the 6 degree ish difference. That plus thicker gusset material seemed to be a factor. Is that what anyone else found?

[Guest]

Re: Strut angles

Not sure if it was mentioned but I noticed the angular difference was from the shorter compression struts being mixed up with the longer compression struts during the rebuild or during the manufacturing of the wing. If the longer strut was used between the spars where the attach fitting are, the spars will be pushed further out making for the 6 degree ish difference. That plus thicker gusset material seemed to be a factor. Is that what anyone else found?

That is a good thought, we have discussed it before, here is one place => http://vb.taylorcraft.org/showthread...ight=conundrum

Check out post #18, there may be others too.

Dave R

[jstall]

Re: Strut angles

That is a good thought, we have discussed it before, here is one place => http://vb.taylorcraft.org/showthread...ight=conundrum

Check out post #18, there may be others too.

Dave R

To me the only way to really know is to measure the angle with the strut off the aircraft
I'd be very sceptical about buying some without this correct number

Univair sets theirs at 3 degrees?? Wag Aero about the same the ones I got from
Harry the criminal was -0- and will not fit at all

JS

[Buell Powell]

Re: Strut angles

Another option might be to send your struts to Wag Aero. If they pass their inspection they can refurbish and seal them and it does away with the receptive inspection.

[PA1195]

Re: Strut angles

As another option to determining the strut end angle I suggest taking a picture from below while still on the plane. There are apps that allow measuring angles of pics or directly with the device, or for us simple folks print it and measure off the paper.

Gary

[jstall]

Re: Strut angles

To me the only way to really know is to measure the angle with the strut off the aircraft
I'd be very sceptical about buying some without this correct number

Univair sets theirs at 3 degrees?? Wag Aero about the same the ones I got from
Harry the criminal was -0- and will not fit at all

JS

HERE IS WAG AERO AT 2.75, IF THIS IS NOMINAL THEN THESE STRUTS WON'T FIT ALL
AIRPLANES LIKE A GLOVE, FORCE FIT IS IN MY OPINION WORSE THAT THE BITE


JAMES.



THE ANGLE OF OUR STURT IS 2.75 DEGREES.



ANY QUESTIONS, PLEASE FEEL FREE TO EMAIL OR CALL 800-558-6868 EXT 149



THANK YU

BRIDGET







From: WagAero - Sales [mailto:[email protected]]
Sent: Friday, February 17, 2017 1:00 PM
To: 'Bridget Payne'
Subject: FW: sweep back strut angle of fittings front struts BC12D



Bridget,



Here is another question from this customer. I hope you can help him.



Thank you,

Dawn



From: James Stallings [
Sent: Friday, February 17, 2017 9:52 AM
To: WagAero - Sales
Subject: Re: sweep back strut angle of fittings front struts BC12D



FOR EXAMPLE I KNOW THAT UNIVAIR STRUTS ARE AT 3 DEGREES, MY AIRPLANE CURRENTLY IS AT 4 DEGREES

JUST CURIOUS WHAT YOURS ARE OR DO YOU MAKE THEM CUSTOM TO THE AIRPLANE??

JS

On 2/17/2017 9:46 AM, WagAero - Sales wrote:

Hi James,