Van's Air Force
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Carbon Fiber Tail spring?
- Thread starter N999BT
- Start date
fixnflyguy
Well Known Member
I didn't know they existed.. I believe Flyboys or someone made a Titanium one which sheds quite a bit of weight.
Dean Pichon
Well Known Member
I haven't seen a carbon fiber one, but would think it would be possible to design and make one. I have a Titanium one on my -4 that saved about a pound. It's a little softer ("springier") than the steel it replaced, but nothing significant. Mine came from Sky Designs.
David Paule
Well Known Member
Correction - they yield very little before breaking. Their springiness depends on the section moment of inertia and the material's modulus of elasticity, as well as the tailspring's overall geometry. Properly designed carbon springs are in fact excellent, due to carbon's high strength, low density and high modulus. The key phrase here is "properly designed."
Dave
Dave
andoman
Well Known Member
To the OP: How much will the CG shift forward with a CF tail spring? Practically speaking, how much more baggage or rear seat pax weight can you carry with a CF tail spring?
I can't crunch the nos. because I'm clueless as to the weight saved. But it seems to me that a CF tail spring would be more of an exercise in overall weight reduction than in gaining a useful forward CG shift.
I can't crunch the nos. because I'm clueless as to the weight saved. But it seems to me that a CF tail spring would be more of an exercise in overall weight reduction than in gaining a useful forward CG shift.
chepburn
Well Known Member
Brent,
You have probably got a W&B spreadsheet somewhere to mess with.... I took mine and changed the Arm of my Rear baggage shelf entry to 288 inches (just a WAG for the tail spring location) With a 3 lb tailspring and a typical Loading arrival case my CG would be at 81.64" (37.3%) If I decrease the 'tail spring' to1 lb the CG moves to 81.36" (33.6%)
In my case, with a IO360 angle valve and the Hartzell constant speed... I should probably go the opposite direction and use a depleted uranium tail spring.
You have probably got a W&B spreadsheet somewhere to mess with.... I took mine and changed the Arm of my Rear baggage shelf entry to 288 inches (just a WAG for the tail spring location) With a 3 lb tailspring and a typical Loading arrival case my CG would be at 81.64" (37.3%) If I decrease the 'tail spring' to1 lb the CG moves to 81.36" (33.6%)
In my case, with a IO360 angle valve and the Hartzell constant speed... I should probably go the opposite direction and use a depleted uranium tail spring.
I don't have the experience to know so forgive me. It's called a tail "spring" for a reason. Would composite have enough elastic property to survive that type of application? Seems like one of those "it's OK until it suddenly isn't" types of applications.
Can anybody get me smarter here?
I've gone the titanium route for my 4 project. Carbon fiber concerns me on the tailspring. Lots of abuse back there and once the carbon has a good hit it will fail eventually.
Initial calculations show saving a pound on the tail will save 4 on the nose. To me thats 5 pounds off the plane if done properly.
Initial calculations show saving a pound on the tail will save 4 on the nose. To me thats 5 pounds off the plane if done properly.
Dean Pichon
Well Known Member
I elected to go with a Titanium tail spring when I replaced the 0.016 elevator skins with 0.020 skins. That added roughly 0.9 pounds to the tail. The additional lead to counter balance the thicker skins doubled that. The new tail spring dropped a pound off that 1.8 lb upper.
vfrazier
Well Known Member
Mush easier to do as Aden says and get some lightweight parts from Blake at https://flyboyaccessories.com/
For example, the standard Van's tailwheel tire weighs about 41 ounces... without grease.
The "Deluxe" tire weighs about 32 ounces, and the lightweight tire weighs 25 ounces.
Blake also offers a pneumatic tire. That tire is quite light, but the larger fork might negate a weight savings.
If weight is a real concern, AND you're running a Bell fork, you might consider going to one of Blake's Screaming Eagle forks. At 15 ounces, it is the lightest fork option that he sells. It is roughly identical in weight to a stock Van's fork, but has better obstacle clearance and much better handling qualities.
FWIW, Blake does not sell titanium springs as someone mentioned above. However, we have been considering it. Ping me or Blake offline if you're interested enough to want one. If there's enough interest, we might add them to the queue. They will be more expensive though! Titanium isn't cheap and presents different machining challenges.
David Paule
Well Known Member
Worth noting is that while titanium tailsprings are at least somewhat available, as far as I know, nobody has designed one or made a successful one using carbon. Which I predict will be a challenge. Personally, I'd prefer titanium for my little RV-3B.
Dave
Dave
RV8JD
Well Known Member
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Pete O Static
Member
I have been working pretty hard at moving my CG forward. The first thing I did was pull off the original API tailwheel and steel spring. Purchased some round stock Titanium from metalsonline.com and then machined a taper to fit the lighter weight Screaming Eagle from Flyboys. Dropped the chains and compression springs for a steering link. That removed 2 pounds from a huge arm. The Titanium cost me about $250. I would think that Carbon Fiber would be very difficult to source and cost prohibitive vs weight saving.
Toobuilder
Well Known Member
I’ve used this bar stock from Titanium Joe to machine my own Ti stingers on a few airplanes. About to do another on my Acrosport.
Carbon cloth and unidirectional tape are easily available, as is an appropriate resin, but making a rod is not easy. Might be better to make a flat spring with a round steel or titanium element bonded or bolted into the end to mate with the hanger in the fuselage. The beauty of a carbon spring is more cloth can be added to increase stiffness if required. The hard bit is bolting it to steel components.
Radioflyer
Well Known Member
I would not think it impossible to design and fabricate a carbon tail spring that would have merit. FYI, Corvettes may have been first production cars to implement full carbon leaf springs in their suspension.
The tail spring would be made up of densely packed carbon tow (string) molded into some optimal shape for desired bending modes and then wrapped with bidirectional cloth to mitigate torsion forces. That is how the main gear and nose gear legs of all the canard aircraft (LongEZ, Cozy, etc) are made except that they use S-glass instead of the typical E-glass.
The tail spring would be made up of densely packed carbon tow (string) molded into some optimal shape for desired bending modes and then wrapped with bidirectional cloth to mitigate torsion forces. That is how the main gear and nose gear legs of all the canard aircraft (LongEZ, Cozy, etc) are made except that they use S-glass instead of the typical E-glass.
