univair struts received?

[whake]

Re: univair struts received?

The approach of useing a level appears to be new from the factory and relates to the AD. We checked the wings before we removed the struts. They were ok the ajusting screws were all the way in. It appears the new rear struts are long and the front struts are on the short side of the tolerance. I have three new tapes and we are going to recheck the lengths tomorrow. I will let you know tomorrow night.. Walt

[Guest]

Re: univair struts received?

The approach of useing a level appears to be new from the factory and relates to the AD. We checked the wings before we removed the struts. They were ok the ajusting screws were all the way in. It appears the new rear struts are long and the front struts are on the short side of the tolerance. I have three new tapes and we are going to recheck the lengths tomorrow. I will let you know tomorrow night.. Walt

Walt,

Its an old spec., was in old service manuals, maybe 40 years back.

Dave

[Forrest Barber]

Re: univair struts received?

Yep your old struts could be off. Lets get some data, measure center to center on fronts & rear, see that they match. If fronts are exactly same , no reason to switch. Then when I have a suspect ship I stretch a string tip to tip over the front spars and measure down to the center of wing attach bolts this is how you adjust the fronts on a Cub .
Taylorcraft are fixed so there is nothing you can do, just an interesting measurement.
Another thing is the human eyeball, put tail on horse with stab level like it says AND then walk out to wing tip, get a step stool if you are vertically challenged ( short) and close one eye and sight down the bottom of the wing. See the washout, see that they are about the same on each side. While there sight down the trailing edge to see that the aileron and the trailing edge are in alignment. Many are warped a bit. Hopefully the strut manufacturers realize that the struts di conform to the drawings at one time BUT they were built off the fixtures (jigs) and did vary a bit.
I have a dozen struts up on the shop and found the repair fixture for Model B & D . Sat morning I will measure a lot of stuff.

We did find a set of NEW Cub struts that had the rears too long and we could not jig the ship correctly , flys and lands like crap. Rear struts too long, why? Well I checked and found struts okay BUT the new heavy fork has a jam nut that is way too thick preventing the fork from going in far enough.

[crispy critter]

Re: univair struts received?

Checking the washout or twist in the wing is done very easy with a smart level(about $10-30 bucks at any parts store or wal-mart depending on how fancy you want).With a smart level you can level the airplane very easily. Level length of the fuse by the horizonal fore and aft. Then level the width of the fuse by using the cross bar behing the seat(the bar that the back of the seat sling attaches to). Once this is done you can pretty well rig the entire airplane with a string and a ruler. Have 2 helpers that can stretch a string tightly from one wing tip to the other at the rear spar. Measure from the string straight down to the top of each rear wing attach bolt,if these measurments are the same on each wing then measure at the location over the rear strut(us a plum-bob to ensure you measure straight down,you can make pencil marks at your measure points the first time so you don't have to use the plum-bob everytime you measure). The object is to try to get the same measurments at the same place on each wing(this is not always possible but get as close as you can). IF measurments are different at the wing attach bolts then you know something is not straight....at this point you can just try to match the settings on your old struts as best you can and then simply fly and adjust until your satisfied with how it flies. If you want to straighten your wing attach points so they have the same measurments then plan on buying/building a fuslage jig and doing some major reconstruction.

[Tom G]

Re: univair struts received?

My Univair struts have been received, painted and installed. My only problem is that the weather has not allowed me to pick the plane up and fly it home. Tried today but no luck. My mechanic tells me that the front struts are about an inch more in diameter than the old ones. Since Univair doesn't have the clamps he had to make them out of 4130 which took some time. I haven't flown it yet but there were no problems with the installation. Hopefully it will fly fine and not need any adjustments.

[Guest]

Re: univair struts received?

My Univair struts have been received, painted and installed. My only problem is that the weather has not allowed me to pick the plane up and fly it home. Tried today but no luck. My mechanic tells me that the front struts are about an inch more in diameter than the old ones. Since Univair doesn't have the clamps he had to make them out of 4130 which took some time. I haven't flown it yet but there were no problems with the installation. Hopefully it will fly fine and not need any adjustments.

Hi Tom,

After I put mine on an rigged per AD. I did test flight and found that it was very slightly wing heavy. Had to adjust one rear strut by one (or two can't recall exactly) half turns. Flew again then many one more half turn adjustment.

So my advice is test fly it before you take it home in case you need your mechanic to make a few final adjustments.

Merry Christmas!

Dave

[Tom G]

Re: univair struts received?

Thanks, Dave, I will do that and report back. Merry Christmas to you too.

[whake]

Re: univair struts received?

The front Univair struts are 119 inches they are correct to the drawing. The rear struts are more difficult to measure. I have them mounted and ajusted to the shortest possible length. The right wing meets the 1 5/16 demension. The left wing is no greater than one inch, 5/16 inch short. Univair has been very cooperative. They are makeing future sets with the ajusting slots 3/16 inch longer and shipping two sets of rear struts to us. The change might bring the left wing to acceptable limits. If the left wing is slightly short of the 1 5/16 demension I will ajust the right wing to match the left wing and fly the plane. I hate to give up any of the struts, they are all finished painted, Univair does not want me to do the modification. We have two planes with the same problem, They are 50 serial numbers apart. The third plane owner is watching us. Will keep you informed..

[Tom G]

Re: univair struts received?

I was finally able to pick my plane up today. After taking off I realized that it is wing heavy on the left side. Nothing drastic but it is constant right aileron to keep it level. I was going to go back and land and have my mechanic adjust it but there was weather closing in from the south and I had a 100 mile trip north. I wanted to get it home.

My right rear strut was replaced with a Univair strut about 5 years ago so I only needed to buy three. I noticed that the adjustment on the left rear (new) strut was out about a half inch from the end of the strut. I don't know how far that is to the maximum. The right rear strut is hardly out at all. It flew perfectly with the old struts. Would adjusting the thread fitting on the left rear to match the right make this work?

The front struts do not adjust at all correct?

Any thoughts would be appreciated.

[whake]

Re: univair struts received?

follow the directions on the service letter, back out the screw on the strut opposite the wing that is heavy. just a couple turns.. it is an easy ajustment you can do it... replace the bolt and the nut and the cotter key.

[Tom G]

Re: univair struts received?

I'll try that and let you know. THANKS!

[Tom G]

Re: univair struts received?

OK, I'm trying to understand the physics involved here. It appears that washout is designed into a wing to give the tip less of an angle of attack than the root. This makes the root stall first and enables more aileron control through the stall. On the T-Craft unscrewing the fitting on the back strut and having more of it "out" increases the washout. Is that right? On mine, the left rear strut has about a half inch more thread showing than the right. It appears then that the left wing has more "wash out" than the right. The right wing then generates more lift so the left wing feels heavy. So its a matter of screwing in the adjustment on the left strut or screwing out the adjustment on the right strut.........which is best? Am I right? Does any of this effect stall/spin characteristics? Thanks!

[Guest]

Re: univair struts received?

OK, I'm trying to understand the physics involved here. It appears that washout is designed into a wing to give the tip less of an angle of attack than the root. This makes the root stall first and enables more aileron control through the stall. On the T-Craft unscrewing the fitting on the back strut and having more of it "out" increases the washout. Is that right? On mine, the left rear strut has about a half inch more thread showing than the right. It appears then that the left wing has more "wash out" than the right. The right wing then generates more lift so the left wing feels heavy. So its a matter of screwing in the adjustment on the left strut or screwing out the adjustment on the right strut.........which is best? Am I right? Does any of this effect stall/spin characteristics? Thanks!

Hi Tom,

Screw the fitting on the wing opposite of heavy wing out, you get a higher cruise speed. That's my opinion. Lower average angle of attach means less drag and more speed needed to generate the same lift. Forrest has a better explanation, I learned this from him. Also rigging the ailerons so they do not droop but rather lift up a 1/4 inch at the TE helped.

I assume that the factory has tested the lift strut adjustments at the extreme settings and verified that there are no issues when set that that way. So I bet these setting effect stall/spin but to an acceptable level

[whake]

Re: univair struts received?

Dave I have all the struts on..met the 1 & 5/16 dimension.. finished my annual ..the plane will be signed off on Wed. am and I will be back in the air..Univair milled the slot longer so that I could make the strut a little shorter..I hate drawings without a tolerance but I will learn more about that 1 & 5/16 demension this week. That little engine checked out great, all cylinders in the high 70s and all the screens were clean..

[Guest]

Re: univair struts received?

Sounds great Walt!

Will be good to be skyward again.

Last week in NY the plane was still snow bound. Ground too soft for the big trucks to drive on and plow it out to use paved runway and they don't let you use skis on the grass runway because they close it for the winter.

Hoping for a ground freeze so they dig her out. Expecting more snow this week.

I got new struts and can't use them! yet

Probably not much snow in Fla. I moved from Winter Park, FL to Kingston, NY in 1978 for a 2 stint at IBM and planed to return to Fla after that. Been in NY ever since! Not too bright! Next stop NC I guess.

Best wishes on the "maiden" flight.

Dave