jimboflying
MEMBER
Control sticks
- Thread starter jimboflying
- Start date
skywagon8a
MEMBER
SE Mass MA6
jimbo, On the surface this sounds like a good idea. However, be absolutely certain the stick will not fail from forces you have not imagined. IF that stick should buckle while in flight, will you be able to control your airplane by reaching to the back seat to use the other stick? Chances are it will not fail, but are you certain? Do you want to be the one who finds out when? The highest load on that stick will be at the location where it plugs into the socket just above the pivot.
Altering control sticks can be fatal. 58 years ago I helped the NTSB investigate a fatal Stearman accident. The altered control stick had failed. That event has been embedded in my memory bank forever.
Some things can be safely altered, some other things well ????????????? Be careful.
Aeronut
Registered User
Kittery, ME
skyawagon8a, can you provide a list of forces acting on the stick and perhaps their magnitude that we should consider when altering a stick? I know during my build I'd like to go with a more ergonomic stick like I used in the military. Having an idea of potential forces and their magnitudes would be helpful when engineering a new stick.
wireweinie
FOUNDER
Palmer, AK
Cool idea but are there any specs that back that up? Carbon fiber is incredibly strong in tension bit the stick will not be used in tension. There is a spec on tubing that tells how much force it takes to put a permanent bend in the piece. If you can find a spec on the CF tube that says it will not bend/break at the same (or greater) force as the steel tube, and you back it up with a test, then it should be safe for use.
Web
Web
skywagon8a
MEMBER
SE Mass MA6
I'll not attempt to supply you with that list, It may not be all inclusive.
Mount the socket which the stick plugs into (with the attach hardware) to a very secure upright test structure. The stick will then be horizontal. Start hanging heavy weights to the end until the stick buckles where it enters the socket. The end of the socket will produce a sharp knife like bending/buckling point. If you can hang more weight on the end without distorting the stick than you can physically provide, then you can consider the particular materiel to be satisfactory.
skywagon8a
MEMBER
SE Mass MA6
True, but no excuse for taking a risk with primary controls.
wireweinie
FOUNDER
Palmer, AK
My thought is the guys that remove the off side stick so a newbie can't grab it. If your stick fails then? I have a customer that had a Cub stick come off the stub during climb out. He could not control the aircraft with the stub alone. He ended up slipping the stick back onto the stub by feel, so he could land. Think about the same scenario but the stick is broken off. If it is a single stick situation to begin with, what are the choices once that stick is unusable?
Web
hotrod180
FRIEND
Port Townsend, WA
OTOH, I just read an accident report for a PA18 which crashed because the passenger had his feet locked down on the brakes when it landed.
[h=1]Plane noses over after passenger hits brakes accidentally[/h]DECEMBER 1, 2020 BY GENERAL AVIATION NEWS STAFF 5 COMMENTS
The pilot was planning to perform an off-airport landing on the shore of a reservoir near Nephi, Utah, where he had successfully landed many times before.
After a 30-minute flight, he configured the PA-18 for landing on the shoreline. During touchdown, the passenger, who was positioned in the rear-seat, inadvertently applied the brakes.
Because of the brakes being depressed on touchdown, the airplane immediately nosed-over coming to rest inverted
My last airplane was a C150/150 taildragger, pretty close quarters inside.
I removed the RH stick & pedals 1) to provide more room for taller passengers,
and 2) to preclude a passenger from getting tangled up in the yoke and/or pedals & causing a mishap.
[h=1]Plane noses over after passenger hits brakes accidentally[/h]DECEMBER 1, 2020 BY GENERAL AVIATION NEWS STAFF 5 COMMENTS
The pilot was planning to perform an off-airport landing on the shore of a reservoir near Nephi, Utah, where he had successfully landed many times before.
After a 30-minute flight, he configured the PA-18 for landing on the shoreline. During touchdown, the passenger, who was positioned in the rear-seat, inadvertently applied the brakes.
Because of the brakes being depressed on touchdown, the airplane immediately nosed-over coming to rest inverted
My last airplane was a C150/150 taildragger, pretty close quarters inside.
I removed the RH stick & pedals 1) to provide more room for taller passengers,
and 2) to preclude a passenger from getting tangled up in the yoke and/or pedals & causing a mishap.
Mr. Ed
MEMBER
PNW
Just looked at the Piper drawing yesterday and they give the option of .035 4130 or .065 aluminum. I’m not an engineer but I would assume the serpentine cut on the bottom of the control stick is to distribute the load on that seam over a greater area. I’d suggest modifying the stick stub with the serpentine cut then test the carbon fiber stick to destruction with the new stick stub.
My experimental project stick stub is 1.0” diameter with a serpentine cut top. The stick is .875 x .049 with a serpentine cut bottom and slides snuggly into the stub. That way, neither tube end produces a sharp stress point. I also bent the top at a 30* angle. I sat in the fuselage with a thin walled aluminum tube inserted in the stick stub and bent the tube until it felt comfortable then reproduced that angle on the 4130 tube. I like the CF concept but don’t know if I could produce a CF tube with a bend. There’s some impressively sturdy CF bike frames that aren’t all straight tubes so it should be possible for someone with the right skills.
My experimental project stick stub is 1.0” diameter with a serpentine cut top. The stick is .875 x .049 with a serpentine cut bottom and slides snuggly into the stub. That way, neither tube end produces a sharp stress point. I also bent the top at a 30* angle. I sat in the fuselage with a thin walled aluminum tube inserted in the stick stub and bent the tube until it felt comfortable then reproduced that angle on the 4130 tube. I like the CF concept but don’t know if I could produce a CF tube with a bend. There’s some impressively sturdy CF bike frames that aren’t all straight tubes so it should be possible for someone with the right skills.
Aeronut
Registered User
Kittery, ME
skywagon8a, no worries. I'll just draw it up in a CAD program. This way I can save time and try out some different material combinations and shapes. If I'm able to get to it this weekend I'll share some analysis on this thread. I'll try to find some control force industry standards to work from.
Josh
Josh
cgoldy
Registered User
Moogerah Queensland Australia
My stick is shorter than normal and has a bend in it. ��. I have always wondered why and been embarrassed when hanging around real cub pilots with there normal sticks.
Its a Javron and I had to cut it down to get full movement therefore it travels under the panel and hits the seat base. The rear stick hits the back of the front seat and the seat belt buckle on any fat passengers. I often wonder how normal cub pilots get full deflection when their stick hits the panel. Is this all because I have increased deflection of my horizontal stab? Does any one else suffer from this affliction?
Its a Javron and I had to cut it down to get full movement therefore it travels under the panel and hits the seat base. The rear stick hits the back of the front seat and the seat belt buckle on any fat passengers. I often wonder how normal cub pilots get full deflection when their stick hits the panel. Is this all because I have increased deflection of my horizontal stab? Does any one else suffer from this affliction?
skywagon8a
MEMBER
SE Mass MA6
All -18 front sticks should go under the panel. Originally there is a folding gust lock which grabs the top of the stick under the panel. The back stick does depend on how far back the seat moves and how big the back seat belly is.
RVBottomly
PATRON
Asotin County Washington (KLWS)
That's what I always thought, but this triggers a side-question. What do people do who hang radios under the panel?
wireweinie
FOUNDER
Palmer, AK
Bang their knuckles.
Web
Web
skywagon8a
MEMBER
SE Mass MA6
Banging knuckles is partially correct. Another answer is, it depends. It depends on the shape and number of radios. The gust lock is U shaped and will swing around and under some installations.
wireweinie
FOUNDER
Palmer, AK
One of the worst places to mount a radio in a Cub type aircraft. In the way of the stick, probably in the way of the gust lock, and hard to read and manipulate the radio.
Web
Web
skywagon8a
MEMBER
SE Mass MA6
True but that's the way it was done for years before solid state was invented.
Farmboy
MEMBER
Middlebury, VT
Or change their sticks.
As my last career was in the boat business I knew a fiberglass guy that did a lot of carbon fiber. He was a rag bagger and like most of us enjoyed creating new improved parts for his sailboat. He swung in One day with the most beautiful tiller handle I’ve ever seen. It was light enough to hold with two fingers, had a S-curve in it that was a work of art and if you stuck the end of it in a slot the two of us could do chin-ups on the other end all day long with zero flex.
As I can’t exert 350 lbs of force on the end of a 18” stick let alone a 5 foot tiller handle, I’d trust a well laid up carbon fiber stick any day.
And like the knowledge that roams in these halls, he didn’t engineer it on a computer. He reached into his bag of experience like Steve Pierce does, and simply built it knowing how fiberglass mat, weave, resin and strength works.
Sure, be smart about it. But don’t shy away from the possibilities.
Transmitted from my FlightPhone on fingers...
Did I miss the news Peter? You’re not in the boat business anymore?
wireweinie
FOUNDER
Palmer, AK
Or change their sticks.
As my last career was in the boat business I knew a fiberglass guy that did a lot of carbon fiber. He was a rag bagger and like most of us enjoyed creating new improved parts for his sailboat. He swung in One day with the most beautiful tiller handle I’ve ever seen. It was light enough to hold with two fingers, had a S-curve in it that was a work of art and if you stuck the end of it in a slot the two of us could do chin-ups on the other end all day long with zero flex.
As I can’t exert 350 lbs of force on the end of a 18” stick let alone a 5 foot tiller handle, I’d trust a well laid up carbon fiber stick any day.
And like the knowledge that roams in these halls, he didn’t engineer it on a computer. He reached into his bag of experience like Steve Pierce does, and simply built it knowing how fiberglass mat, weave, resin and strength works.
Sure, be smart about it. But don’t shy away from the possibilities.
Transmitted from my FlightPhone on fingers...
I agree whole heartedly about the idea of the composite stick. But I would NEVER install one before I had some kind of data to prove the strength. I.e. manufacturer's data for the tube or make one up and test it to failure.
As pointed out above, this is a primary control. It breaks in flight and you're primarily screwed.
Web
cubdriver2
FRIEND
upstate NY
I taught myself basic acro in my Pa11. When I stalled out inverted of some manuvers the speed builds very fast and I've danced the dance of pulling harder or let it speed up more. Last thing I would want to think about when worrying about ripping the wings off was is this carbon thing in my hand going to stay together. Not for me, too scary :lol:
Glenn
Glenn
jimboflying
MEMBER
The sticks were made on a special aluminum mandrel with a custom layup with unidirectional fiber orientation lengthwise. Calculations by an aerospace professor showed that the strength was comparable to .065 Aluminum. Thin Steel .035 has a different failure mechanism with localized crumpling. The calculations show that conservatively the carbon fiber structure sticks should withstand 170 pounds of force.
Gordon Misch
MEMBER
Toledo, Wa (KTDO)
CAR 3 has design stick forces listed. They're greater than I would have guessed, and far greater than I experience in my -12. However, that's the design standard.
wireweinie
FOUNDER
Palmer, AK
RVBottomly
PATRON
Asotin County Washington (KLWS)
That's quite interesting. I was wondering about steel control sticks needing gussets or something to stop the crumpling. That was before this thread came up.
Now I have visions of making a carbon fiber stick, planting it into a tall post, and using it for a pull-up bar--all in the name of material testing.
Web's CAR chart seems to indicate you are in the ballpark.
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