Tailwheel

[soartech[_2_]]

While discussing tailwheel weight I wondered why we need a tail dolly?
Why do most modern sailplanes have fixed tailwheels yet SGS gliders
have castering tailwheels. Shouldn't we have a caster instead?

[Mike the Strike]

On Wednesday, December 12, 2012 11:05:28 AM UTC-7, soartech wrote:
> While discussing tailwheel weight I wondered why we need a tail dolly?
>
> Why do most modern sailplanes have fixed tailwheels yet SGS gliders
>
> have castering tailwheels. Shouldn't we have a caster instead?

Good luck on cross-wind take-offs!

Mike

[Grider Pirate[_2_]]

On Dec 12, 10:05*am, soartech > wrote:
> While discussing tailwheel weight I wondered why we need a tail dolly?
> Why do most modern sailplanes have fixed tailwheels yet SGS gliders
> have castering tailwheels. Shouldn't we have a caster instead?

Schweizers are 'nose draggers'. The CG is ahead of the main, so they
tend to follow the rope on the runway. A CG hook tail dragger with a
castering tailwheel would be .... very exciting on the ground, but not
in a good way.

[Bill D]

On Wednesday, December 12, 2012 11:05:28 AM UTC-7, soartech wrote:
> While discussing tailwheel weight I wondered why we need a tail dolly?
>
> Why do most modern sailplanes have fixed tailwheels yet SGS gliders
>
> have castering tailwheels. Shouldn't we have a caster instead?

Your basic question is valid. Back in the round engine days, some big taildraggers had lockable tail wheels which castered for taxiing and locked straight-ahead for takeoff.

One imagines a variation of this could work with gliders. If the cockpit is empty, weight on the tailwheel would make it caster. With a pilot in the cockpit, the lighter weight on the tailwheel locks it straight ahead. The castering shaft would just have a axial spring pushing the tail wheel down 5mm or so to lock it straight ahead. Basically it would be automatic with no input from the pilot.

[Dave Nadler]

On Wednesday, December 12, 2012 1:24:45 PM UTC-5, Bill D wrote:
> On Wednesday, December 12, 2012 11:05:28 AM UTC-7, soartech wrote:
>
> > While discussing tailwheel weight I wondered why we need a tail dolly?
>
> >
>
> > Why do most modern sailplanes have fixed tailwheels yet SGS gliders
>
> >
>
> > have castering tailwheels. Shouldn't we have a caster instead?
>
>
>
> Your basic question is valid. Back in the round engine days, some big taildraggers had lockable tail wheels which castered for taxiing and locked straight-ahead for takeoff.
>
>
>
> One imagines a variation of this could work with gliders. If the cockpit is empty, weight on the tailwheel would make it caster. With a pilot in the cockpit, the lighter weight on the tailwheel locks it straight ahead. The castering shaft would just have a axial spring pushing the tail wheel down 5mm or so to lock it straight ahead. Basically it would be automatic with no input from the pilot.

And the first bump it unlocks ?
Complicated and not smart.

[Ventus_a]

On Wednesday, December 12, 2012 11:05:28 AM UTC-7, soartech wrote:
While discussing tailwheel weight I wondered why we need a tail dolly?

Why do most modern sailplanes have fixed tailwheels yet SGS gliders

have castering tailwheels. Shouldn't we have a caster instead?

Your basic question is valid. Back in the round engine days, some big taildraggers had lockable tail wheels which castered for taxiing and locked straight-ahead for takeoff.

One imagines a variation of this could work with gliders. If the cockpit is empty, weight on the tailwheel would make it caster. With a pilot in the cockpit, the lighter weight on the tailwheel locks it straight ahead. The castering shaft would just have a axial spring pushing the tail wheel down 5mm or so to lock it straight ahead. Basically it would be automatic with no input from the pilot.

...and starting with stick full back to keep the glider straight at the beginning of a crosswind take off will unlock the wheel and negate its benefits

Colin

[aerodyne]

I can't wait till spring....

[Bill D]

On Wednesday, December 12, 2012 11:43:25 AM UTC-7, Dave Nadler wrote:
> On Wednesday, December 12, 2012 1:24:45 PM UTC-5, Bill D wrote:
>
> > On Wednesday, December 12, 2012 11:05:28 AM UTC-7, soartech wrote:
>
> >
>
> > > While discussing tailwheel weight I wondered why we need a tail dolly?
>
> >
>
> > >
>
> >
>
> > > Why do most modern sailplanes have fixed tailwheels yet SGS gliders
>
> >
>
> > >
>
> >
>
> > > have castering tailwheels. Shouldn't we have a caster instead?
>
> >
>
> >
>
> >
>
> > Your basic question is valid. Back in the round engine days, some big taildraggers had lockable tail wheels which castered for taxiing and locked straight-ahead for takeoff.
>
> >
>
> >
>
> >
>
> > One imagines a variation of this could work with gliders. If the cockpit is empty, weight on the tailwheel would make it caster. With a pilot in the cockpit, the lighter weight on the tailwheel locks it straight ahead. The castering shaft would just have a axial spring pushing the tail wheel down 5mm or so to lock it straight ahead. Basically it would be automatic with no input from the pilot.
>
>
>
> And the first bump it unlocks ?
>
> Complicated and not smart.

Geez, more negative experts!

A large enough bump might unlock it for a few milliseconds, but it would re-lock instantly. Note that Blanik's are taildraggers and many have permanently castering tail wheels so it can't be a big deal.

It still worries you, a simple latching down-lock which requires manual unlocking for castering is dead simple but almost certainly unnecessary.

Note that it comes with a major safety advantage - taking off with a tail dolly on becomes impossible.

[soartech[_2_]]

> Good luck on cross-wind take-offs!
>
> Mike

Wouldn't it be OK, you just would have to use the rudder more?
Actually I like the automatic locking mechanism idea best so far.
Most of the reported weight and balance numbers showed a 20 lbs or
more
difference with the pilot in place.

[Eric Greenwell[_4_]]

On 12/12/2012 12:08 PM, Bill D wrote:

>>> One imagines a variation of this could work with gliders. If the
>>> cockpit is empty, weight on the tailwheel would make it caster.
>>> With a pilot in the cockpit, the lighter weight on the tailwheel
>>> locks it straight ahead. The castering shaft would just have a
>>> axial spring pushing the tail wheel down 5mm or so to lock it
>>> straight ahead. Basically it would be automatic with no input
>>> from the pilot.
>>
>>
>>
>> And the first bump it unlocks ?
>>
>> Complicated and not smart.
>
> Geez, more negative experts!
>
> A large enough bump might unlock it for a few milliseconds, but it
> would re-lock instantly. Note that Blanik's are taildraggers and
> many have permanently castering tail wheels so it can't be a big
> deal.

Blaniks have a huge rudder that becomes effective even before the wing
runner lets go. Not so for high performance gliders.

Another likely reason: the tailwheel is large but carefully faired in.
Enabling it to swivel would involve tradeoffs in cost, weight, and drag.

And possibly: people tow the gliders around with vehicles attached to
the tail dolly. Attaching a tow bar to just the might be a problem.

But I agree it would be nice; personally, I'd rather have a steerable
tail wheel. No more directional control problems at low speeds. I love
the one on my ASH 26 E even when I take a tow, and, of course, every
time I land.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[[email protected]]

On Wednesday, December 12, 2012 10:05:28 AM UTC-8, soartech wrote:
> While discussing tailwheel weight I wondered why we need a tail dolly?
>
> Why do most modern sailplanes have fixed tailwheels yet SGS gliders
>
> have castering tailwheels. Shouldn't we have a caster instead?

I would not enjoy moving the glider to the takeoff runway across the relatively soft dirt landing runway rolling on a tailwheel size wheel.

BV

[Roger Fowler[_3_]]

At 21:22 12 December 2012, Eric Greenwell wrote:
>On 12/12/2012 12:08 PM, Bill D wrote:
>
>>>> One imagines a variation of this could work with gliders. If the
>>>> cockpit is empty, weight on the tailwheel would make it caster.
>>>> With a pilot in the cockpit, the lighter weight on the tailwheel
>>>> locks it straight ahead. The castering shaft would just have a
>>>> axial spring pushing the tail wheel down 5mm or so to lock it
>>>> straight ahead. Basically it would be automatic with no input
>>>> from the pilot.
>>>
>>>
>>>
>>> And the first bump it unlocks ?
>>>
>>> Complicated and not smart.
>>
>> Geez, more negative experts!
>>
>> A large enough bump might unlock it for a few milliseconds, but it
>> would re-lock instantly. Note that Blanik's are taildraggers and
>> many have permanently castering tail wheels so it can't be a big
>> deal.
>
>Blaniks have a huge rudder that becomes effective even before the wing
>runner lets go. Not so for high performance gliders.
>
>Another likely reason: the tailwheel is large but carefully faired in.
>Enabling it to swivel would involve tradeoffs in cost, weight, and drag.
>
>And possibly: people tow the gliders around with vehicles attached to
>the tail dolly. Attaching a tow bar to just the might be a problem.
>
>But I agree it would be nice; personally, I'd rather have a steerable
>tail wheel. No more directional control problems at low speeds. I love
>the one on my ASH 26 E even when I take a tow, and, of course, every
>time I land.
>
>--
>Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>email me)
>

Question: How much download can you apply when pulling the stick full back
right after touchdown?

Experience: I forgot to lock the tailwheel on a Stearman once before I
took off. Boy was that exciting!

FR

[Eric Greenwell[_4_]]

On 12/12/2012 1:59 PM, Roger Fowler wrote:
> At 21:22 12 December 2012, Eric Greenwell wrote:

>>>> And the first bump it unlocks ?
>>>>
>>>> Complicated and not smart.
>>>
>>> Geez, more negative experts!
>>>
>>> A large enough bump might unlock it for a few milliseconds, but it
>>> would re-lock instantly. Note that Blanik's are taildraggers and
>>> many have permanently castering tail wheels so it can't be a big
>>> deal.
>>
>> Blaniks have a huge rudder that becomes effective even before the wing
>> runner lets go. Not so for high performance gliders.
>>
>> Another likely reason: the tailwheel is large but carefully faired in.
>> Enabling it to swivel would involve tradeoffs in cost, weight, and drag.
>>
>> And possibly: people tow the gliders around with vehicles attached to
>> the tail dolly. Attaching a tow bar to just the might be a problem.
>>
>> But I agree it would be nice; personally, I'd rather have a steerable
>> tail wheel. No more directional control problems at low speeds. I love
>> the one on my ASH 26 E even when I take a tow, and, of course, every
>> time I land.
>
> Question: How much download can you apply when pulling the stick full back
> right after touchdown?
>
> Experience: I forgot to lock the tailwheel on a Stearman once before I
> took off. Boy was that exciting!

Or just touching down tail first, and having it unlock in a cross wind.
Probably not as exciting as your Stearman ride, but disturbing enough.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Dave Nadler]

On Wednesday, December 12, 2012 3:08:18 PM UTC-5, Bill D wrote:
> Geez, more negative experts!

Did you consider there are REASONS for the current designs ?

> ...Blanik's are taildraggers and many have permanently
> castering tail wheels so it can't be a big deal.

Blaniks and SGS gliders have little in common with modern high
performance gliders, where the rudder has limited effectiveness
until higher speed. A fixed or steerable tailwheel and a
HEAVY tail weight make cross-wind operation safer in modern
gliders.

[Bill D]

On Wednesday, December 12, 2012 3:24:45 PM UTC-7, Dave Nadler wrote:
> On Wednesday, December 12, 2012 3:08:18 PM UTC-5, Bill D wrote:
>
> > Geez, more negative experts!
>
>
>
> Did you consider there are REASONS for the current designs ?

Sure, they're cheap. No other reason.

> Blaniks and SGS gliders have little in common with modern high
>
> performance gliders, where the rudder has limited effectiveness
>
> until higher speed.

SGS and Blaniks have little in common with each other so which example are you using? Blanik's have adequate rudder authority but nothing exceptional.. I'd guess my Nimbus has more.

The survey showed most empty tail dragger gliders have about 75 lbs on the tail wheel. Setting the locking spring at 10 pounds less would prevent bumps and tail-first landings from unlocking it in all but the most extreme cases. But, if you're still worried and a latching down-lock doesn't tickle your fancy, a simple air damper that required the full empty load to be applied for a few seconds for it to unlock would cover both possibilities.

More expensive? Sure, but not nearly as much as the cost of a tail dolly. Heavier? A little, but not nearly as heavy as the brass tail wheels in common use. Complex? You're kidding, right? We're talking of a spring on a sliding shaft with a locking detent. That's about half as complicated as a tail dolly which has to be installed, removed and kept track of. I've seen tow out bars which don't use a tail dolly.

[Tony V]

On 12/12/2012 4:22 PM, Eric Greenwell wrote:

> But I agree it would be nice; personally, I'd rather have a steerable
> tail wheel. No more directional control problems at low speeds. I love
> the one on my ASH 26 E even when I take a tow, and, of course, every
> time I land.


The Antares has a steerable tail wheel. I suspect that Dave N would love
to sell you one. :-)

Tony "6N"

[Brad Alston]

...and starting with stick full back to keep the glider straight at the beginning of a crosswind take off will unlock the wheel and negate its benefits

Colin

How about a steerable castering tail wheel?...a la HP series.

[bumper[_4_]]

One of Eric's points earlier was the added drag most full castering tailwheels would present. On his ASH26E, the steerable tailwheel is limited in it's steering range to about 30 degrees to each side. Thus the tailwheel fairing can have a reasonably small opening and the extended part of the tailwheel presents minimal drag.

In order to fully caster, the tailwheel structure would either have to extend out far enough, or the boom would have to be fat to accomodate complete rotation.

Course the tailwheel could be retractable . . . more complex and expensive. Cost/ benefit?

bumper

[Bill D]

On Wednesday, December 12, 2012 7:41:20 PM UTC-7, bumper wrote:
> One of Eric's points earlier was the added drag most full castering tailwheels would present. On his ASH26E, the steerable tailwheel is limited in it's steering range to about 30 degrees to each side. Thus the tailwheel fairing can have a reasonably small opening and the extended part of the tailwheel presents minimal drag.
>
>
>
> In order to fully caster, the tailwheel structure would either have to extend out far enough, or the boom would have to be fat to accomodate complete rotation.
>
>
>
> Course the tailwheel could be retractable . . . more complex and expensive. Cost/ benefit?
>
>
>
> bumper

Well, that's a point. As I imagine it, the tailwheel would extend only 5mm further than one of those breakaway rubber things with a skate wheel. That far back, the boundary layer is pretty thick so not much extra drag - probably less than an open air scoop.

This is not one of those things for retrofit - the 337 field approval hassle wouldn't be worth it but it would be a nice feature on a new glider or an experimental. The idea isn't for taxiing, it's just to make it easier to push the glider off the runway without running to get a tail dolly. Of course, nothing in the idea would prevent using a tail dolly for really rough ground.

[Eric Greenwell[_4_]]

On 12/12/2012 9:02 PM, Bill D wrote:

>> Course the tailwheel could be retractable . . . more complex and
>> expensive. Cost/ benefit?
>> bumper
>
> Well, that's a point. As I imagine it, the tailwheel would extend
> only 5mm further than one of those breakaway rubber things with a
> skate wheel. That far back, the boundary layer is pretty thick so not
> much extra drag - probably less than an open air scoop.
>
> This is not one of those things for retrofit - the 337 field approval
> hassle wouldn't be worth it but it would be a nice feature on a new
> glider or an experimental. The idea isn't for taxiing, it's just to
> make it easier to push the glider off the runway without running to
> get a tail dolly. Of course, nothing in the idea would prevent using
> a tail dolly for really rough ground.

The Grob tail wheel that plugs in always seemed like a good idea: full
dolly size wheel for moving it around, drops off during launch if you
forget it, small and light enough to carry in the glider, seemingly
minor weight addition to the glider to use it.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Dan Marotta]

Walking to get the dolly after a long flight might reduce the chance of
blood clots in the legs and will certainly aid in preventing weight gain.
Or do youse guys just walk to the cooler for that "beverage"?

Ah... Off season...


"Eric Greenwell" > wrote in message
...
> On 12/12/2012 9:02 PM, Bill D wrote:
>
>>> Course the tailwheel could be retractable . . . more complex and
>>> expensive. Cost/ benefit?
>>> bumper
>>
>> Well, that's a point. As I imagine it, the tailwheel would extend
>> only 5mm further than one of those breakaway rubber things with a
>> skate wheel. That far back, the boundary layer is pretty thick so not
>> much extra drag - probably less than an open air scoop.
>>
>> This is not one of those things for retrofit - the 337 field approval
>> hassle wouldn't be worth it but it would be a nice feature on a new
>> glider or an experimental. The idea isn't for taxiing, it's just to
>> make it easier to push the glider off the runway without running to
>> get a tail dolly. Of course, nothing in the idea would prevent using
>> a tail dolly for really rough ground.
>
> The Grob tail wheel that plugs in always seemed like a good idea: full
> dolly size wheel for moving it around, drops off during launch if you
> forget it, small and light enough to carry in the glider, seemingly minor
> weight addition to the glider to use it.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
> email me)

[Dave Nadler]

On Thursday, December 13, 2012 10:09:01 AM UTC-5, Dan Marotta wrote:
> Walking to get the dolly after a long flight might reduce the chance of
> blood clots in the legs and will certainly aid in preventing weight gain.
> Or do youse guys just walk to the cooler for that "beverage"?

Cool dudes do NOT push the glider about.
We taxi back to the trailer and the cool beverage ;-)

See ya, Dave "YO electric"

[kirk.stant]

On Thursday, December 13, 2012 4:20:33 PM UTC+1, Dave Nadler wrote:

> Cool dudes do NOT push the glider about.
>
> We taxi back to the trailer and the cool beverage ;-)
>
>
>
> See ya, Dave "YO electric"


Really cool dudes taxi back to the trailer without an engine... ;^)

66

[Ralph Jones[_3_]]

On Thu, 13 Dec 2012 06:57:27 -0800, Eric Greenwell
> wrote:

>
>The Grob tail wheel that plugs in always seemed like a good idea: full
>dolly size wheel for moving it around, drops off during launch if you
>forget it, small and light enough to carry in the glider, seemingly
>minor weight addition to the glider to use it.

My partner and I used to have an Astir-CS, and I wouldn't have wanted
the factory tail dolly in the cockpit: it was several pounds of
ironmongery and could have done some damage in a bad outlanding. We
did make a small, lightweight one to carry aboard, but used the much
larger factory wheel for most ground handling.

The dolly hole made a whining noise that was ground-audible at 1000
AGL...don't know how much drag that really produced, but we habitually
taped it over before a contest launch. And that produced a memorable
event: I positioned my partner on the grid, removed the dolly, and he
said "Tape up my a$$hole!", unaware that he was on a hot mike.

[Grider Pirate[_2_]]

Sounds like a jet! I can't make a direct link, but if you check out
"UF Low Level" from here:http://www.youtube.com/my_videos?feature=mhum
it's clearly audible.
Eric: While that 'wheel on a post' dolly COULD be made fairly
lightweight, the OEM unit isn't. But it DOES fall away if you forget
to remove it. ;-)


On Dec 13, 7:56*am, Ralph Jones > wrote:
> On Thu, 13 Dec 2012 06:57:27 -0800, Eric Greenwell
>
> > wrote:
>
> >The Grob tail wheel that plugs in always seemed like a good idea: full
> >dolly size wheel for moving it around, drops off during launch if you
> >forget it, small and light enough to carry in the glider, seemingly
> >minor weight addition to the glider to use it.
>
> My partner and I used to have an Astir-CS, and I wouldn't have wanted
> the factory tail dolly in the cockpit: it was several pounds of
> ironmongery and could have done some damage in a bad outlanding. We
> did make a small, lightweight one to carry aboard, but used the much
> larger factory wheel for most ground handling.
>
> The dolly hole made a whining noise that was ground-audible at 1000
> AGL...don't know how much drag that really produced, but we habitually
> taped it over before a contest launch. And that produced a memorable
> event: I positioned my partner on the grid, removed the dolly, and he
> said "Tape up my a$$hole!", unaware that he was on a hot mike.

[John Firth[_4_]]

HP 14, fully castering tailwheel for easy ground handling,
offset CG towhook, dropped a wing on the roll; it instantly groundlooped
broke the rope, and nearly smashed a parked glider.

Maybe a worst case but a lesson in what can happen.

JMF



At 21:22 12 December 2012, Eric Greenwell wrote:
>On 12/12/2012 12:08 PM, Bill D wrote:
>
>>>> One imagines a variation of this could work with gliders. If the
>>>> cockpit is empty, weight on the tailwheel would make it caster.
>>>> With a pilot in the cockpit, the lighter weight on the tailwheel
>>>> locks it straight ahead. The castering shaft would just have a
>>>> axial spring pushing the tail wheel down 5mm or so to lock it
>>>> straight ahead. Basically it would be automatic with no input
>>>> from the pilot.
>>>
>>>
>>>
>>> And the first bump it unlocks ?
>>>
>>> Complicated and not smart.
>>
>> Geez, more negative experts!
>>
>> A large enough bump might unlock it for a few milliseconds, but it
>> would re-lock instantly. Note that Blanik's are taildraggers and
>> many have permanently castering tail wheels so it can't be a big
>> deal.
>
>Blaniks have a huge rudder that becomes effective even before the wing
>runner lets go. Not so for high performance gliders.
>
>Another likely reason: the tailwheel is large but carefully faired in.
>Enabling it to swivel would involve tradeoffs in cost, weight, and drag.
>
>And possibly: people tow the gliders around with vehicles attached to
>the tail dolly. Attaching a tow bar to just the might be a problem.
>
>But I agree it would be nice; personally, I'd rather have a steerable
>tail wheel. No more directional control problems at low speeds. I love
>the one on my ASH 26 E even when I take a tow, and, of course, every
>time I land.
>
>--
>Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>email me)
>

[Eric Greenwell[_4_]]

On 12/13/2012 7:56 AM, Ralph Jones wrote:
>> >
>> >The Grob tail wheel that plugs in always seemed like a good idea: full
>> >dolly size wheel for moving it around, drops off during launch if you
>> >forget it, small and light enough to carry in the glider, seemingly
>> >minor weight addition to the glider to use it.

> My partner and I used to have an Astir-CS, and I wouldn't have wanted
> the factory tail dolly in the cockpit: it was several pounds of
> ironmongery and could have done some damage in a bad outlanding.

These days it would light weight carbon fiber and stow safely behind the
seat.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Dave Nadler]

On Thursday, December 13, 2012 3:50:18 PM UTC-5, firsys wrote:
> HP 14, fully castering tailwheel for easy ground handling,
> offset CG towhook, dropped a wing on the roll; it instantly groundlooped
> broke the rope, and nearly smashed a parked glider.
>
> Maybe a worst case but a lesson in what can happen.
>
> JMF

Hi John - Hope you are well !
HP14s are supposed to have springs for tailwheel steering, no ?
IIRC I had an exciting take-off some decades ago when I didn't
replace the busted springs... Fixed prior next flight !
Have a great Holiday season,
Best Regards, Dave "YO electric"

[Ralph Jones[_3_]]

On Thu, 13 Dec 2012 14:04:36 -0800, Eric Greenwell
> wrote:

>
>These days it would light weight carbon fiber

So would the rest of the ship...;-)