Lift Strut Data

N4005V · Post by **N4005V** » Tue Nov 08, 2005 3:29 pm

I stand corrected.

Stinson driver · Post by **Stinson driver** » Fri Nov 11, 2005 12:33 pm

A question on struts- On my plane one strut has the atach bolts exposed
and one strut has streamlined atach point on the Fus ends- In the log book there is a note about a strut being changed- Wich one is corect ?

Post by **GAHorn** » Fri Nov 11, 2005 4:49 pm

There were several minor changes thru the years to the struts, of A and B models. Aside from the part number "dash" differentiation of the A from B models, there were three fastener changes for attaching the end fittings to the tube, and there was also an actual manufacturing change in the fitting itself.
For example, the first series of struts utilized NAS178 "hi-shear" rivets in that location, while (excepting for a few transitional and some repair-scheme struts) later struts used AN426 rivets. The transition struts used AN5 bolts. My own airplane was a transition airplane. (When Cessna's supplier of hi-shear rivets came up short during production, AN5 bolts were specified on a short run of aircraft until engineering approved the substitution of common AN426 rivets. The AN5 bolts were already an approved subtitution in repairing/replacing cast end fittings. Manufacturing improvements were also made to later (and replacement) end fittings.)
AN5 bolts are stronger than rivets, but they must be installed in reamed holes or they will not share the load properly, and they have the disadvantages of rougher appearance and dissimilar materials (being made of steel) than AN426 rivets.

kmisegades · Post by **kmisegades** » Sat Nov 12, 2005 3:37 pm

Miles, how do you know all these details on our favorite airplane? I am very impressed! I remain frustrated in my search for accurate coordinates of the struts themselves. Surely someone knows these? Greta C-170 flying weather down here in NC this weekend. Clear and cool and lots of color in the trees. On takeoff, 800 FPM on my ancient C-145 engine with 2 aboard and full fuel sure is nice. Kent

cessna170bdriver · Post by **cessna170bdriver** » Sat Nov 12, 2005 5:40 pm

kmisegades wrote:Miles, how do you know all these details on our favorite airplane? I am very impressed! I remain frustrated in my search for accurate coordinates of the struts themselves. Surely someone knows these? Greta C-170 flying weather down here in NC this weekend. Clear and cool and lots of color in the trees. On takeoff, 800 FPM on my ancient C-145 engine with 2 aboard and full fuel sure is nice. Kent

Kent,

Didn't you mean this compliment for George? A lot of what I know is "been there done that", curioisity, and paying attention to others' airplanes. I've also spent a lot of time in the manuals and catalogs. I'm sure that George, being the Association's Parts and Maintenance Coordinator, keeps all that info handy.

I actually wasn't aware that there were more than two types of fasteners for strut fittings for A and B models. I've only ever noticed the hi-shear rivets (older) and the flush rivets (newer). Always nice to learn new stuff.

Miles

Post by **GAHorn** » Sat Nov 12, 2005 6:08 pm

A lot of my knowlege is useless trivia interspersed among huge savannahs of ignorance.

kmisegades · Post by **kmisegades** » Sat Nov 12, 2005 6:32 pm

Sorry - yes kudos were meant for George. However your comments, Miles, are evidence of your vast knowledge on the subject, also. Our clan is fortunate to have the both of you. Superb flying day here in central NC - which is what I am leaving to do now. Kent

Post by **GAHorn** » Sat Nov 12, 2005 7:16 pm

kmisegades wrote: I want to try my hand at making some improvements on streamlined fairings where the strut mates with the wing and fuselage.

Kent, I don't understand all I know about this.

Why would you need to know the coordinates simply to make fairings? The ends of the struts, where fairings would fit, are not continuations of the "streamline" tubing shape anyway. They are die-formed to a flat upper/lower surface to fit the end fittings. I don't see how knowing the coordinates of the streamline portion of the struts would be helpful.

kmisegades · Post by **kmisegades** » Sun Nov 13, 2005 12:05 am

George - I will explain - my profession is CFD - computational fluid dynamics. See my company's web site, http://www.ensight.com, for examples. I am used to having geometry for aircraft existing in CAD, "meshing" this and then using CFD software to compute aero loads at high accuracy. Of course this is overkill for our nice slow airplanes, however this is the way that I work and I have all the tools in place to compute such things rather quickly and accurately. To me it makes no real difference whether I am working on a hypersonic vehicle or a low and slow C-170, they all more or less follow the same laws of fluid dynamics. I realize that optimized fairings will have little influence on the speed of my airplane, but I might not be able look at myself in the mirror if I didn't apply my professional skills to my own airplane. Hope this makes some sense.

Kent

blueldr · Post by **blueldr** » Sun Nov 13, 2005 3:21 am

For all you guys that are not into "Fluid Dynamics" and don't want to make your own fairings, Steen, up in Montana, makes really nice fiberglas strut end fairings.

Post by **GAHorn** » Sun Nov 13, 2005 7:09 am

Thanks, Kent, for the explanation. But I still don't see how information regarding the shape of the tubular struts is going to be useful to construct fairings which must fit the ends of the struts...which are NOT shaped like the main "streamline" portion. In order to closely fit the end fittings which attach to the airframe, the struts are die-formed into a flattened shape for approx 6-8" at the ends. Where fairings would likely abutt the struts, the struts are no longer "streamlined" tubes.
So again,...how will coordinates of the streamline tubes be of any use re: your project?

kmisegades · Post by **kmisegades** » Sun Nov 13, 2005 1:45 pm

George, when you model complex 3D geometries such as fairings, you need to include a fairly large part of the surrounding aircraft in order to get the actual flow conditions correctly. For this same reason, when car companies model the underhood flow around an engine for cooling studies, they include the entire external geometry of the car. Leave this out, and you don't get the correct flow distribution coming into the engine. Same goes for a fairing. The onset airflow upstream of the fairing is anything but two-dimensional. Thus one ought to include all of the geometry in a 1m sphere the the fairing. That's why I need the coordinates of the struts, as the fairing will extend out beyond the flat end of the strut to where the streamlined part begins. The standard method used to design fairings - lots of modelling clay and TLAR (That Looks About Right) does not always lead to better performance. In fact, sometimes very subtle curves in fairings, wheel pants, wingtips, etc. can lead to very poor airflow - an example "may" be the Madras wingtips that came with my plane (but are not on them). Lots of claims by the original maker, however studies I have seen show these to be real duds. Will my fairings be any better than those on the market today? Probably not, and if they are, I doubt that I will be able to measure the difference. But trying to tame mother nature sure is fun. The flight for today will be my home base, Cox Field, near Raleigh, up to Blue Ridge airfield and its great little restuarant on the field for lunch. Lots of color up there in Martinsville, VA, home of the NASCAR track and a local icon in vintage aircraft circles, Morton Lester. Good flying. Kent

Post by **GAHorn** » Sun Nov 13, 2005 5:56 pm

OK, that computes.

(Re: the Madras tips. Back in the early 70's, my employer at the time S&S Pipeline patrol had a fleet of 150's with which we flew pipeline patrol. (Doh!)

The airplanes averaged about 130 hours/month on the line, cruising at low level.
The boss succumbed to the Madras promotional literature and bought a set for one of the airplanes. After a year it was decided they actually had cost the company quite a bit of fuel. Sorry I don't recall the actual math, I just know he was disgusted. They also prevented good vision out past the wing and were dangerous in the traffic pattern, in my opinion.)

Dave Clark · Post by **Dave Clark** » Mon Nov 14, 2005 2:31 pm

Kent

Don't want to hijack your thread here but what about a fairing for the landing gear legs? It seems a bit of speed could be gained by cleaning up the area at the fuse and then airfoiling a cover that would go over the gear legs. Then ultimately a fairing at the wheel to (perhaps a yet undeveloped) aerodynamic wheel pant. I think this has been done for the 180?? Not sure if it was done right though.

My trip down to AZ from WA this fall got awfully slow with up to 45k headwinds south of Red Bluff. Even with the 180 hp cranked up to 75% it was a terrible thing to experience

Of course most of the time I'm

It takes money for speed.

trake · Post by **trake** » Mon Nov 14, 2005 10:18 pm

Dave, youre right it has been done for the 180, its called the Snyder speed kit. Check EAA Vintage Airplane magazine April 2004 issue. I did a search a while back but couldnt find them. Supposed 5 or 6 mph gain on the 180