Winter project, tow out gear - wing wheel

[bildan]

I have to refurbish/replace my wing wheel assembly and need some
suggestions/insights. The current one is the typical aluminum wing
cuff and bicycle wheel. It wasn't well made to start with and it's
falling apart. I want to take this opportunity to improve the thing.

One of the biggest issues I see is that if the cuff isn't perfectly
aligned on the wing, the wheel will try to track sideways and cock the
cuff risking wing damage. Further, it's a big chunk of "stuff" that
takes up space in the trailer or retrieve vehicle.

My first thought is that there are already wing cuffs used as wing
supports in the trailer. One of these might serve a second purpose as
a wing cuff for the tow out gear if I made it a little wider and added
attach points for a wheel. This would eliminate the need to find
extra space for it.

My second thought is to use a castering wheel instead of a fixed one.
This would prevent lateral and twisting forces from being transferred
to the wing. Even if the wing cuff wasn't perfectly aligned, it
wouldn't matter. The wheel/fork/steering head from a child's bicycle
might be adapted. I'm thinking that the typical ~20" wheel is much
larger than it needs to be.

Further thoughts about wheels leads me to think a bicycle tire is
designed for traction which isn't really needed in a wing wheel. In
fact, it would probably be better if it would slide sideways more
easily than a rubber tire. Pneumatic tires also can go flat. Maybe a
solid plastic wheel from some other source would be better.

Any thoughts?

[Papa3]

On Nov 5, 11:06*am, bildan > wrote:
> I have to refurbish/replace my wing wheel assembly and need some
> suggestions/insights. *The current one is the typical aluminum wing
> cuff and bicycle wheel. *It wasn't well made to start with and it's
> falling apart. *I want to take this opportunity to improve the thing.
>
> One of the biggest issues I see is that if the cuff isn't perfectly
> aligned on the wing, the wheel will try to track sideways and cock the
> cuff risking wing damage. *Further, it's a big chunk of "stuff" that
> takes up space in the trailer or retrieve vehicle.
>
> My first thought is that there are already wing cuffs used as wing
> supports in the trailer. *One of these might serve a second purpose as
> a wing cuff for the tow out gear if I made it a little wider and added
> attach points for a wheel. *This would eliminate the need to find
> extra space for it.
>
> My second thought is to use a castering wheel instead of a fixed one.
> This would prevent lateral and twisting forces from being transferred
> to the wing. *Even if the wing cuff wasn't perfectly aligned, it
> wouldn't matter. *The wheel/fork/steering head from a child's bicycle
> might be adapted. * I'm thinking that the typical ~20" wheel is much
> larger than it needs to be.
>
> Further thoughts about wheels leads me to think a bicycle tire is
> designed for traction which isn't really needed in a wing wheel. *In
> fact, it would probably be better if it would slide sideways more
> easily than a rubber tire. *Pneumatic tires also can go flat. *Maybe a
> solid plastic wheel from some other source would be better.
>
> Any thoughts?

I think all of the points you raise are on target. I have a
"factory" Anschau (Komet) wing wheel with the padded fiberglass
cuff. It does suffer from the twisting issue you describe. I made
two modifications to mine:

1. Replaced the existing pneumatic tire with a 14" solid tire with a
spoked plastic wheel. I had nothing but trouble with the pneumatic
tire, especially with the bead being pulled off the tire when the
lateral loads were applied. I must have replaced the tube 5 times
over 2 years. I think you do want to account for the loss of some
shock absorbtion if you go with a solid wheel; the factory unit I
have has a gas strut that allows the unit to collapse slightly under
load.
2. Added 8 pounds of weight to the bottom of the cuff. This
counteracts the tendency to sometime drop the opposite wing if there
is a wind gust or some other upset. I've seen guys split an aileron
when the wing falls at just the wrong moment, especially when towing
the glider with water in the wings.

FWIW, I think a well-made aluminum cuff (i.e. properly shaped to match
the wing profile and well padded) is much easier to pull off than a
home-built fiberglass version.

P3

[sisu1a]

> One of the biggest issues I see is that if the cuff isn't perfectly
> aligned on the wing, the wheel will try to track sideways and cock the
> cuff risking wing damage. *Further, it's a big chunk of "stuff" that
> takes up space in the trailer or retrieve vehicle.
>
> My first thought is that there are already wing cuffs used as wing
> supports in the trailer. *One of these might serve a second purpose as
> a wing cuff for the tow out gear if I made it a little wider and added
> attach points for a wheel. *This would eliminate the need to find
> extra space for it.
>
> My second thought is to use a castering wheel instead of a fixed one.
> This would prevent lateral and twisting forces from being transferred
> to the wing. *Even if the wing cuff wasn't perfectly aligned, it
> wouldn't matter. *The wheel/fork/steering head from a child's bicycle
> might be adapted. * I'm thinking that the typical ~20" wheel is much
> larger than it needs to be.
>
> Further thoughts about wheels leads me to think a bicycle tire is
> designed for traction which isn't really needed in a wing wheel. *In
> fact, it would probably be better if it would slide sideways more
> easily than a rubber tire. *Pneumatic tires also can go flat. *Maybe a
> solid plastic wheel from some other source would be better.
>
> Any thoughts?

Study the Sparrowhawk wing wheel. It is a beautiful exercise in
minimalism. The cuff is somewhat traditional (although would only fit
a 'normal' sailplane's tailplane...), but rather than a fork it uses a
thick and somewhat flexible fiberglass bow with 2 rollerbade wheels
and indeed casters. It is really light (obviously, it was designed by
Greg Cole!) While I myself would like bigger wheels, it is a very
elegant solution with castering the fiberglass bow.

I am making a new one for my ship, but more traditionally constructed.
A hinged (well fit...) fiberglass cuff and a bike fork for a 20"
wheel. My fork will be easily removable though, as it will be attached
via a gooseneck (the part of a bike that attaches the handlebars to
the forks). I am a bike fan with a BMX background so chose 'cool' bmx
parts (FMF fork, Spin wheel...ebay). My 20" bike wheel (oversize for
smooth fields, perfect for rough ones with badger holes etc) is a
sylish composite 3 spoke jobbie that looks really cool, and your right
traction is not necessary. I myself wouldn't use less than a 16" bike
wheel (Cobra wing wheels are 16") since I do visit fields with sizable
badger/chuckholes (probably prairie dog holes for you!) I use a Tioga
Pool Comp tire (a fully slick tread) and have a kevlar tire liner. If
I run into problems with repeated flats (my field is a goathead
factory...) I will pay the few extra bucks to have the tube expandy-
urethane foam-filled for a permanent solution. I like the shock
absorption that pneumatic/foam-filled wheels provide myself, and the
larger the diameter of the wheel the lower the rolling resistance is
over obstacles. My wheel attaches via a quick release skewer so is
very easily removed. The fork also easily removes if I really need to
break it down.

I chose not to make mine quite as light as possible though, as I like
my wheeled wing to stay on the ground. I may even make a provision on
it to accommodate a 5-10# weight for breezy days because it is lighter
than average.

-Paul

[bildan]

On Nov 5, 9:58*am, sisu1a > wrote:
> *> One of the biggest issues I see is that if the cuff isn't perfectly
>
>
>
> > aligned on the wing, the wheel will try to track sideways and cock the
> > cuff risking wing damage. *Further, it's a big chunk of "stuff" that
> > takes up space in the trailer or retrieve vehicle.
>
> > My first thought is that there are already wing cuffs used as wing
> > supports in the trailer. *One of these might serve a second purpose as
> > a wing cuff for the tow out gear if I made it a little wider and added
> > attach points for a wheel. *This would eliminate the need to find
> > extra space for it.
>
> > My second thought is to use a castering wheel instead of a fixed one.
> > This would prevent lateral and twisting forces from being transferred
> > to the wing. *Even if the wing cuff wasn't perfectly aligned, it
> > wouldn't matter. *The wheel/fork/steering head from a child's bicycle
> > might be adapted. * I'm thinking that the typical ~20" wheel is much
> > larger than it needs to be.
>
> > Further thoughts about wheels leads me to think a bicycle tire is
> > designed for traction which isn't really needed in a wing wheel. *In
> > fact, it would probably be better if it would slide sideways more
> > easily than a rubber tire. *Pneumatic tires also can go flat. *Maybe a
> > solid plastic wheel from some other source would be better.
>
> > Any thoughts?
>
> Study the Sparrowhawk wing wheel. It is a beautiful exercise in
> minimalism. The cuff is somewhat traditional (although would only fit
> a 'normal' sailplane's tailplane...), but rather than a fork it uses a
> thick and somewhat flexible fiberglass bow with 2 rollerbade wheels
> and indeed casters. It is really light (obviously, it was designed by
> Greg Cole!) While I myself would like bigger wheels, it is a very
> elegant solution with castering the fiberglass bow.
>
> I am making a new one for my ship, but more traditionally constructed.
> A hinged (well fit...) fiberglass cuff and a bike fork for a 20"
> wheel. My fork will be easily removable though, as it will be attached
> via a gooseneck (the part of a bike that attaches the handlebars to
> the forks). I am a bike fan with a BMX background so chose 'cool' bmx
> parts (FMF fork, Spin wheel...ebay). My 20" bike wheel *(oversize for
> smooth fields, perfect for rough ones with badger holes etc) is a
> sylish composite 3 spoke jobbie that looks really cool, and your right
> traction is not necessary. I myself wouldn't *use less than a 16" bike
> wheel (Cobra wing wheels are 16") since I do visit fields with sizable
> badger/chuckholes (probably prairie dog holes for you!) *I use a Tioga
> Pool Comp tire (a fully slick tread) and have a kevlar tire liner. If
> I run into problems with repeated flats (my field is a goathead
> factory...) I will pay the few extra bucks to have the tube expandy-
> urethane foam-filled for a permanent solution. I like the shock
> absorption that pneumatic/foam-filled wheels provide myself, and the
> larger the diameter of the wheel the lower the rolling resistance is
> over obstacles. My wheel attaches via a quick release skewer so is
> very easily removed. The fork also easily removes if I really need to
> break it down.
>
> I chose not to make mine quite as light as possible though, as I like
> my wheeled wing to stay on the ground. I may even make a provision on
> it to accommodate a 5-10# weight for breezy days because it is lighter
> than average.
>
> -Paul

One of my frustrations is that glider makers don't offer an option for
threaded hard points on the lower wing surface. These, with an I-bolt
would serve as tiedown points, wing wheel attachment points, one-man
assembly dolly attachment points and maybe trailer attachment points.
They could eliminate the need for cuffs entirely saving huge amounts
of room for "stuff". They could just be taped over when not needed.

I'm thinking of two wing wheels if they can be made simple/light/small
enough. (Yeah, I know - more "stuff") Two would totally eliminate the
tip over problem. If I can use the trailer wing saddles/cuffs, the
additional "stuff factor" might not be too bad.

I'm not sure that shock absorption is necessary. The only vertical
load is the tip over force which is tiny compared to the weight of the
glider. The current wing wheel is very rigid and causes no problem.
If they're rigid, they might serve double duty as wing stands.

[Andy[_1_]]

On Nov 5, 9:06*am, bildan > wrote:
> I have to refurbish/replace my wing wheel assembly and need some
> suggestions/insights. *

I was singularly unimpressed with the wing wheel that came with my
ASW-28, a one size fits nothing design, and sent it back unused for a
refund. I made my own design wing tip wheel which comprises a cuff
laid up on the wing tip (over a sandwich of felt and protective
plastic). The cuff leg attach points were laser aligned to the
airbrake box. It fits well and tracks perfectly. The cuff is glass
cloth rather than chopped glass so it is lighter and stronger than the
original. I used schedule 40 PVC tubing for the prototype legs. It
worked so well I have not changed them.

The theoretical disadvantages of my design are
1. It only fits the left wing
2. The width between the main wheel and the tip wheel is larger than a
conventional mid span wheel.

Neither has proved to be of any practical significance in several
years of use.

Andy

[DRN]

On Nov 5, 11:58*am, sisu1a > wrote:
> Study the Sparrowhawk wing wheel. It is a beautiful exercise in
> minimalism. The cuff is somewhat traditional (although would only fit
> a 'normal' sailplane's tailplane...), but rather than a fork it uses a
> thick and somewhat flexible fiberglass bow with 2 rollerbade wheels
> and indeed casters. It is really light (obviously, it was designed by
> Greg Cole!) While I myself would like bigger wheels, it is a very
> elegant solution with castering the fiberglass bow.

Can you point us at a picture of Greg's dolly ?
I don't find it on the sparrowhawk web site...

Thanks !

[Fred Blair]

I have a Libelle 301 and I used the wing supports that roll into the
trailer. I attached 3/4 by 3/4 aluminum square tubes to the bottom and then
from there constructed aluminum struts down to a 20 in bike wheel and tire.
I made quick attachments to the bars at the top with long 1/4 rods.
Everything comes apart and goes into the front of the trailer. The only
design problem is that the wheel does not pivot.
Fred
"bildan" > wrote in message
...
>I have to refurbish/replace my wing wheel assembly and need some
> suggestions/insights. The current one is the typical aluminum wing
> cuff and bicycle wheel. It wasn't well made to start with and it's
> falling apart. I want to take this opportunity to improve the thing.
>
> One of the biggest issues I see is that if the cuff isn't perfectly
> aligned on the wing, the wheel will try to track sideways and cock the
> cuff risking wing damage. Further, it's a big chunk of "stuff" that
> takes up space in the trailer or retrieve vehicle.
>
> My first thought is that there are already wing cuffs used as wing
> supports in the trailer. One of these might serve a second purpose as
> a wing cuff for the tow out gear if I made it a little wider and added
> attach points for a wheel. This would eliminate the need to find
> extra space for it.
>
> My second thought is to use a castering wheel instead of a fixed one.
> This would prevent lateral and twisting forces from being transferred
> to the wing. Even if the wing cuff wasn't perfectly aligned, it
> wouldn't matter. The wheel/fork/steering head from a child's bicycle
> might be adapted. I'm thinking that the typical ~20" wheel is much
> larger than it needs to be.
>
> Further thoughts about wheels leads me to think a bicycle tire is
> designed for traction which isn't really needed in a wing wheel. In
> fact, it would probably be better if it would slide sideways more
> easily than a rubber tire. Pneumatic tires also can go flat. Maybe a
> solid plastic wheel from some other source would be better.
>
> Any thoughts?

[Papa3]

On Nov 5, 12:54*pm, bildan > wrote:

>
> I'm not sure that shock absorption is necessary. *The only vertical
> load is the tip over force which is tiny compared to the weight of the
> glider. *The current wing wheel is very rigid and causes no problem.
> If they're rigid, they might serve double duty as wing stands.

I think that shock absorbtion is a good idea. I'm not so worried
about the load on the spar or even on the wing skin under the cuff
(pretty insignificant) as I am about two scenarios:

1. If you get a strong vertical jolt (say running over a lip of a
taxiway), you run the risk of twisting the glider to the point where
either it rotates and catches the other wing on the ground or puts
twisting loads on the aft fuselage that may not be insignificant
(depending on your your glider is secured to the tow-out bar).
Especially if you have a slight unballance with water, this could be
serious.

2. If you get a strong longitudinal jolt (catching the wheel on a
chuck hole) what happens to the trailing edge of the wing if the cuff
shifts suddenly?

I'm thinking that some amount of give in the system is useful. Just
my 0.02.

P3

[rlovinggood]

I have a "Swan" trailer (from Germany) and "Swan" towout gear.

The wing wheel is the typical cuff around the wing and bicycle wheel.

A bit ingenious is the "suspension" they built into the setup. The
two vertical square tube aluminum forks that connect the cuff to the
wheel axle do not connect directly to the axle, but to an offset from
the axle that allows some pivoting movement. I think I have some
digital photos somewhere and if anyone is interested, I might be able
to dig them up and e-mail them. No, I don't have ready access to the
wing wheel itself at the moment.

The Swan wing wheel cuff fits over the wing at the very end of the
wing. It is a hinged cuff made of aluminum and padded with felt. All
frame members are made from aluminum. The wheel is a spoked steel rim
bicycle wheel. I don't know the diameter, but it may be 20"
Maybe... I've used it only a few times and it worked well. I've only
seen it work from the mirror of my car and not from walking behind my
car to see if it's twisting and popping the wing. I'm sure a
castoring wheel would work much better for most setups.

Ray Lovinggood
Carrboro, North Carolina, USA

[Martin Gregorie[_4_]]

On Thu, 06 Nov 2008 16:59:54 -0800, Papa3 wrote:

> I think that shock absorbtion is a good idea. I'm not so worried about
> the load on the spar or even on the wing skin under the cuff (pretty
> insignificant) as I am about two scenarios:
>
I'd add a third:

3. Personally, I'd be more worried about the twisting effect that will
drive the wing LE against the fuselage and possibly damage the pickup
pins and/or upset their shims if the wheel hits anything. The loads
applied at this point will be FAR greater than any forces at the tail
dolly or on the far wingtip.

Thats why you NEVER push a glider by its wingtips.

I'd suggest that your best protection against these forces is twofold:

1) use the biggest possible bicycle wheel on your tip dolly. A big wheel
will ride over a higher obstacle without catching on it than a smaller
one.

2) take care not to run the tip wheel over anything that it won't ride
over easily.

Picking up on other comments in this thread:

- a fore/aft pivot on the fork that carries the wing dolly wheel and
a gas strut suspension can't hurt, but personal observation suggests
that the load even the smallest gas strut can support is so much greater
than the weight on the wheel that the strut won't cushion anything
unless its so old and knackered that its about to collapse completely.

- If you carefully align the tip dolly wheel so its parallel with the
fuselage centre line it will never drag sideways. Its axle is so close
to being inline with the main wheel axle that there's never a noticeable
side force on a properly aligned dolly wheel even when you pivot the
glider round its main wheel.

- A typical tip dolly isn't particularly light if you make it with an
old touring bicycle front fork and wheel.

At a guess mine weighs 7 kg (15 lbs) or so. I don't think I've seen it
come close to lifting, even towing crosswind in a strong breeze with
the dolly on the windward side. I fly a Libelle, which isn't exactly
heavy AND has the dolly on its lightest wing. Murphy guarantees that!


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Fred Blair]

I would like to see the pictures, if possible.
Fred
"rlovinggood" > wrote in message
...
>I have a "Swan" trailer (from Germany) and "Swan" towout gear.
>
> The wing wheel is the typical cuff around the wing and bicycle wheel.
>
> A bit ingenious is the "suspension" they built into the setup. The
> two vertical square tube aluminum forks that connect the cuff to the
> wheel axle do not connect directly to the axle, but to an offset from
> the axle that allows some pivoting movement. I think I have some
> digital photos somewhere and if anyone is interested, I might be able
> to dig them up and e-mail them. No, I don't have ready access to the
> wing wheel itself at the moment.
>
> The Swan wing wheel cuff fits over the wing at the very end of the
> wing. It is a hinged cuff made of aluminum and padded with felt. All
> frame members are made from aluminum. The wheel is a spoked steel rim
> bicycle wheel. I don't know the diameter, but it may be 20"
> Maybe... I've used it only a few times and it worked well. I've only
> seen it work from the mirror of my car and not from walking behind my
> car to see if it's twisting and popping the wing. I'm sure a
> castoring wheel would work much better for most setups.
>
> Ray Lovinggood
> Carrboro, North Carolina, USA

[Doug Hoffman]

Martin Gregorie wrote:
> On Thu, 06 Nov 2008 16:59:54 -0800, Papa3 wrote:
>
>> I think that shock absorbtion is a good idea. I'm not so worried about
>> the load on the spar or even on the wing skin under the cuff (pretty
>> insignificant) as I am about two scenarios:
>>
> I'd add a third:
>
> 3. Personally, I'd be more worried about the twisting effect that will
> drive the wing LE against the fuselage and possibly damage the pickup
> pins and/or upset their shims if the wheel hits anything. The loads
> applied at this point will be FAR greater than any forces at the tail
> dolly or on the far wingtip.
>
> Thats why you NEVER push a glider by its wingtips.
>
> I'd suggest that your best protection against these forces is twofold:
>
> 1) use the biggest possible bicycle wheel on your tip dolly. A big wheel
> will ride over a higher obstacle without catching on it than a smaller
> one.
>
> 2) take care not to run the tip wheel over anything that it won't ride
> over easily.

My personal practice is to *never* exceed 5 mph when towing. I read an
article some time ago (Soaring magazine?) where an insurance company
reported that most damage incidents while towing were due to towing too
fast. Or the damage could have been avoided by towing more slowly.

Never stop quickly (don't ask).

The other thing I do is to use small/short screws for the wing cuff
clasp attachment. Any excessive loads will result in the screws letting
go: in effect they are like shear pins, so the wing is protected. I
have "tested" this safety when attempting to tow with a flat glider main
wheel (a bad idea!). The safety worked.


> - If you carefully align the tip dolly wheel so its parallel with the
> fuselage centre line it will never drag sideways. Its axle is so close
> to being inline with the main wheel axle that there's never a noticeable
> side force on a properly aligned dolly wheel even when you pivot the
> glider round its main wheel.

Agreed. My practice is to frequently glance at the wheel while towing.
If it starts to skip or lean then I stop the car, get out, and
straighten the wheel. With practice one quickly learns how to put the
wheel on straight at first try.

Regards,

-Doug

[rlovinggood]

Fred and all,

After I posted my reply and stated "I have photos", I looked for the
photos and haven't found them yet. Without ready access to the wing
wheel (it's at the airport and, unfortunately, I'm not), I won't be
able to run out and snap a photo right away. But in the meantime,
I'll keep looking. I KNOW I took the photos. I just don't remember
where I might have put them. Maybe I just need to search for ALL jpeg
files on my computer.

I regret my hasty posting.

Ray Lovinggood
Carrboro, North Carolina, USA

[JJ Sinclair]

Roger on the SPEED, I have repaired several gliders over the years
that were damaged in towing and they were all towing too fast. I tow
at about 5 mph, on some vehicles I need to ride the brake a tad to
keep it slow. I also adjust the mirror to show the wing wheel which I
put on the left wing. I once saw an idiot towing at a good 30 mph!
While turning, the wing dolly twisted and ripped open his
alieron................put him out of the contest.
JJ

rlovinggood wrote:
> Fred and all,
>
> After I posted my reply and stated "I have photos", I looked for the
> photos and haven't found them yet. Without ready access to the wing
> wheel (it's at the airport and, unfortunately, I'm not), I won't be
> able to run out and snap a photo right away. But in the meantime,
> I'll keep looking. I KNOW I took the photos. I just don't remember
> where I might have put them. Maybe I just need to search for ALL jpeg
> files on my computer.
>
> I regret my hasty posting.
>
> Ray Lovinggood
> Carrboro, North Carolina, USA

[Udo Rumpf[_2_]]

At 12:36 07 November 2008, Doug Hoffman wrote:
>Martin Gregorie wrote:
>> On Thu, 06 Nov 2008 16:59:54 -0800, Papa3 wrote:
>>
>>> I think that shock absorbtion is a good idea. I'm not so worried
about
>>> the load on the spar or even on the wing skin under the cuff (pretty
>>> insignificant) as I am about two scenarios:
>>>
>> I'd add a third:
>>
>> 3. Personally, I'd be more worried about the twisting effect that will

>> drive the wing LE against the fuselage and possibly damage the pickup
>> pins and/or upset their shims if the wheel hits anything. The loads
>> applied at this point will be FAR greater than any forces at the tail
>> dolly or on the far wingtip.
>>
>> Thats why you NEVER push a glider by its wingtips.
>>
>> I'd suggest that your best protection against these forces is
twofold:
>>
>> 1) use the biggest possible bicycle wheel on your tip dolly. A big
wheel
>
>> will ride over a higher obstacle without catching on it than a smaller

>> one.
>>
>> 2) take care not to run the tip wheel over anything that it won't ride

>> over easily.
>
>My personal practice is to *never* exceed 5 mph when towing. I read an
>article some time ago (Soaring magazine?) where an insurance company
>reported that most damage incidents while towing were due to towing too
>fast. Or the damage could have been avoided by towing more slowly.
>
>Never stop quickly (don't ask).
>
>The other thing I do is to use small/short screws for the wing cuff
>clasp attachment. Any excessive loads will result in the screws letting

>go: in effect they are like shear pins, so the wing is protected. I
>have "tested" this safety when attempting to tow with a flat glider
main
>wheel (a bad idea!). The safety worked.
>
>
>> - If you carefully align the tip dolly wheel so its parallel with the
>> fuselage centre line it will never drag sideways. Its axle is so
close
>> to being inline with the main wheel axle that there's never a
>noticeable
>> side force on a properly aligned dolly wheel even when you pivot the
>> glider round its main wheel.
>
>Agreed. My practice is to frequently glance at the wheel while towing.
> If it starts to skip or lean then I stop the car, get out, and
>straighten the wheel. With practice one quickly learns how to put the
>wheel on straight at first try.
>
>Regards,
>
>-Doug

Hi Doug,
I have used a trailing arm design successfully for over 12 years
on various gliders . There attribute: it makes the wing /
wheel combination very stable even in rough grass. Here is a picture.
www.ssa.org/myhome.aspmbr=8257600665&show=gallery
Udo

[toad]

Check your tail dolly's also. Mine had the wheel attached to the cuff
with screws, not through bolts. One day this spring they separated
while towing behind my truck and the rudder hit the bumper and was
damaged.

The new design has a much more secure attachment.

Todd Smith
3S

[brianDG303]

Martin Gregorie > wrote:


* * * "Thats why you NEVER push a glider by its wingtips."

From DG:

Pulling an aircraft
von friedelweber am Do Okt 25, 2007 1:36 pm
Is it okay to pull an aircraft on the wingtips?

The question tends to pop up in the gliding society. There is always a
concern that wings could suffer damage if the ground crew pulls on the
wingtips. Therefore we’d like to give you a short insight – without
going into too much detail – on the force that can be applied in a
longitudinal direction. Water tanks and other specific items are left
out in this abbreviated description. The length of the lever enable to
calculate the max. force a wing has to withstand without suffering any
damages.

The building describes a force of 400N as specification for every
glider. This will result in a force of 40kp (longitudinal). A normal
adult will commonly not be able to develop a force of 40kp in a
longitudinal direction without any problems. In other words – it is
save to pull a plane on its wingtips.

[ContestID67]

On Nov 6, 8:16*pm, Martin Gregorie
> wrote:

> ...Thats why you NEVER push a glider by its wingtips.

I have seen the question of if it is OK to pull/push by the wingtips
asked many times. This exact question was asked of the DG/LS folks
years ago. Their answer was "Yes, it is!". I searched my mail
archives and found the reference to this in the DG Newsletter #69,
June 2004. Unfortunately, the link in the newsletter email is no
longer valid. Here is what I have from the email...

> 12. Pulling an aircraft: Is it okay to pull an aircraft on the wingtips?
>
> Yes, it is!
>
> http://www.dg-flugzeugbau.de/faq-e.html#pulling

Sorry, that I didn't keep the web page info. As I remember the FAQ,
it had a technical discussion on why this was valid. Does this apply
to all gliders? Hmmmm.

My $0.02.

- John DeRosa

[ContestID67]

Looks like "BrianDG303" came up with the reference I spoke of.
Thanks.

The question still stands, is it ok for every glider or just
DG's? ;-)

- John DeRosa

[Udo Rumpf[_2_]]

Try this for the pictures
http://www.ssa.org/myhome.aspmbr=8257600665&show=gallery

[Doug Hoffman]

Udo Rumpf wrote:


> I have used a trailing arm design successfully for over 12 years
> on various gliders . There attribute: it makes the wing /
> wheel combination very stable even in rough grass. Here is a picture.
> www.ssa.org/myhome.aspmbr=8257600665&show=gallery


Hi Udo,

I am sure your design and fabrication are superior to what I am using.
Although I find that my wheel, once put on straight, stays straight.

Here is a photo:

/
Look at the file named Wing Wheel.jpg I have since covered the foam
with felt.

The construction is very simple with no glassing or welding required.
Btw, I could not get your URL to work.

Regards,

-Doug

[bildan]

I've been convinced that I do need to provide some vertical
compliance, if not exactly "shock absorption". I have a collection of
gas struts in my shop that should work fine.

My goal is to absolutely minimize the "stuff factor" since I already
have way too much "stuff" to transport with the glider. That means
using the trailering wing cuffs as part of the wing wheel assembly and
as small a wheel as I can get away with. Storing and transporting
small wheels and struts should add minimal hassle. I wouldn't plan to
use the tow-out gear on rough airfields.

I plan to make only one wing wheel but retain the option of making
two. I've had some heart stopping moments when an unexpected wind
gust nearly tipped a watered-up glider onto the wheel-less wing.
Using two wing wheels prevents this but adds the requirement for
vertical compliance.

I've watched people try to perfectly align non-castering wing wheels
for years. The slightest mis-alignment will get worse the further the
glider moves until they have to stop and re-align it. With a flapped
glider, this has to put unnecessary force on the flap hinges. I will
make castering wing wheels using industrial-strength lazy Susan
bearings. The bearing, strut and wheel will slide into a pocket on
the trailer wing cuff and snap in place.

The tow out bar itself will need some careful re-design. The
accidents I have seen and read about all seem to involve a failure of
some kind with the tow out bar. Mostly this is the glider tailwheel
jumping off the bar leading to a jackknife-type accident. I like a
tow-out bar that lets the glider roll on the tail dolly wheel. Maybe
this means vertical-only compliance so the bar remains straight aft
eliminating the possibility of a jack-knife.

[Fred Blair]

This March while at the Marfa Wave Camp, I was helping Dick Johnson move his
glider and he said just grab the tip and we will move it. Someone said
something about that and he said, "you can't put enough load on it to hurt
it"; if Dick says it is ok, it is ok in my book.
Fred
"brianDG303" > wrote in message
...

Martin Gregorie > wrote:


"Thats why you NEVER push a glider by its wingtips."

From DG:

Pulling an aircraft
von friedelweber am Do Okt 25, 2007 1:36 pm
Is it okay to pull an aircraft on the wingtips?

The question tends to pop up in the gliding society. There is always a
concern that wings could suffer damage if the ground crew pulls on the
wingtips. Therefore we’d like to give you a short insight – without
going into too much detail – on the force that can be applied in a
longitudinal direction. Water tanks and other specific items are left
out in this abbreviated description. The length of the lever enable to
calculate the max. force a wing has to withstand without suffering any
damages.

The building describes a force of 400N as specification for every
glider. This will result in a force of 40kp (longitudinal). A normal
adult will commonly not be able to develop a force of 40kp in a
longitudinal direction without any problems. In other words – it is
save to pull a plane on its wingtips.

[Bob Kuykendall]

On Nov 7, 8:38*am, ContestID67 > wrote:
> ...Does this apply to all gliders? *Hmmmm.

No, I don't think that it does. It's probably safe to pull on the
wingtips of most modern 15m and Standard class ships, but other than
that I would be at least a bit cautious, especially with longer wings
or wood construction.

At issue is the certification requirement for drag and thrust loads
applied at the tip. I don't have Basic Glider Criteria handy, but I
believe that the FAR part 23 and JAR22 requirements are both around
100 lbs applied longitudinally at the tip both forward and aft.

However, and this is important, the fine print of the certification
rules says that this requirement can be waived or reduced if a lower
maximum force can be rationally defended. Many such exceptions are
applied in the type certification of sailplanes; a good example is the
reduced maximum input force applied in pitch at the control stick.
There are a lot of gliders out there where if you applied the standard
FAR part 23 maximum pitch input force you'd come away with the entire
control sticl mechanism in your hand.

The gliders I'd want to be especially careful around are those where
the lift pins are not cross-pinned or otherwise captured, and where
the lift pins are longitudinally fairly close to the main spar. The
Libelle comes to mind in this regard, especially as regards thrust
(forward-pulling) forces at the wingtip. Because of the Libelle's
short fuselage, the transverse tube for the forward lift pins is
snugged right back against the spar, and allow for a fairly great
force multiplication as the wings are pulled forward. Of course, the
Libelle has that nice stout tongue-and-fork spar joining that is
probably capable of absorbing a great deal of the moment applied by
drag and thrust on its own. But still, I've seen forward thrust at
Libelle tips open a substantial gap where the aft lift pin plugs into
the wings. It didn't seem to break anything but it did and does give
me the willies.

Also, consider that a lot of Experimental gliders are not subject to
any substantial portion of FAR 23 or JAR22, and maybe nobody knows at
all what sort of drag or thrust loads are safe. I remember back when
they were selecting the whirled, er, World Class glider, and somebody
submitted a glider that looked a bit sketchy in terms of drag and
thrust resistance. The judges crunched some rho-vee-squared and
decided that the glider probably had inadequate thrust resistance to
safely winch launch.

Thanks, Bob K.
www.hpaircraft.com/hp-24

[Martin Gregorie[_4_]]

On Fri, 07 Nov 2008 07:40:04 -0800, toad wrote:

> Check your tail dolly's also. Mine had the wheel attached to the cuff
> with screws, not through bolts. One day this spring they separated
> while towing behind my truck and the rudder hit the bumper and was
> damaged.
>
I also smashed a rudder when the wheel + towbar detached from the cuff,
letting the glider run forward and hit the back of the car. This was a
tail dolly that came with the glider and looked good from the outside.

It turned out that:
- the swivel platform was made from polyester car body filler
- the swiveling wheel's base plate was 'glued in place' by dropping
it onto the partially set up platform. This was left a bit late,
with the result that the base plate adhered over less then 20% of
its surface.
- a single layer of 200g (6 oz) open weave glass cloth was bonded
over the the baseplate, down the sides of the platform and onto the
cuff after poking holes for the wheel's mounting bolts.
- when all was cured the glass was painted and the wheel bolted on.
- err, that's it.

The tow bar followed normal practise and clipped onto the wheel axle,
so all towing loads were handled by one layer of glass cloth and a dodgy
partial bond between a flat steep plate and a lump of car body filler. No
bolts had ever been used to transmit tow loafds from wheel to cuff.

I wonder how many other tail dollies are as badly made as this one.

Pictures of the original and how I made what I consider an adequate
assembly are here:

http://www.gregorie.org/gliding/dolly/index.html


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Martin Gregorie[_4_]]

On Fri, 07 Nov 2008 09:47:27 -0800, bildan wrote:

> The tow out bar itself will need some careful re-design. The accidents
> I have seen and read about all seem to involve a failure of some kind
> with the tow out bar. Mostly this is the glider tailwheel jumping off
> the bar leading to a jackknife-type accident. I like a tow-out bar that
> lets the glider roll on the tail dolly wheel. Maybe this means
> vertical-only compliance so the bar remains straight aft eliminating the
> possibility of a jack-knife.
>
Be careful. Be very careful. If I understand you, you're intending to
attach the tow bar to the tail dolly's swiveling wheel so that the wheel
carries the tail and there's nothing to lock the tow bar on the fuselage
axis.

I've seen this sort of rig 'Z-fold' when the towing golf cart merely
slowed down. Admittedly this was on a glider with little weight on its
tail dolly wheel (ASK-21) but it was a very gentle slow down and
fortunately no damage was done.

There's a good chance that that damage would have resulted if the same
had happened on wet grass with normal braking and the towbar not
perfectly inline with the fuselage axis.

IMO having a pivot at each end of the towbar (i.e. swiveling tail wheel
and tow hitch) you have an accident waiting to happen.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[bildan]

On Nov 7, 6:31*pm, Martin Gregorie
> wrote:
> On Fri, 07 Nov 2008 09:47:27 -0800, bildan wrote:
> > The tow out bar itself will need some careful re-design. *The accidents
> > I have seen and read about all seem to involve a failure of some kind
> > with the tow out bar. *Mostly this is the glider tailwheel jumping off
> > the bar leading to a jackknife-type accident. *I like a tow-out bar that
> > lets the glider roll on the tail dolly wheel. *Maybe this means
> > vertical-only compliance so the bar remains straight aft eliminating the
> > possibility of a jack-knife.
>
> Be careful. Be very careful. If I understand you, you're intending to
> attach the tow bar to the tail dolly's swiveling wheel so that the wheel
> carries the tail and there's nothing to lock the tow bar on the fuselage
> axis.
>
> I've seen this sort of rig 'Z-fold' when the towing golf cart merely
> slowed down. Admittedly this was on a glider with little weight on its
> tail dolly wheel (ASK-21) but it was a very gentle slow down and
> fortunately no damage was done.
>
> There's a good chance that that damage would have resulted if the same
> had happened on wet grass with normal braking and the towbar not
> perfectly inline with the fuselage axis.
>
> IMO having a pivot at each end of the towbar (i.e. swiveling tail wheel
> and tow hitch) you have an accident waiting to happen.
>
> --
> martin@ * | Martin Gregorie
> gregorie. | Essex, UK
> org * * * |

Exactly. This is the input I'm looking for.

My thought is to eliminate the pivot at the car so the tow bar cannot
swing left and right relative to the towing vehicle thus making the "Z-
fold", which we call a jackknife, impossible. It will, of course,
make the glider swing a wider turn than the car but that may be
useful. Even though the tow bar cannot pivot about a vertical axis at
the car, it would be able to pivot about a lateral axis to accommodate
uneven ground.

This scheme would locate the tail dolly an exact distance behind the
towing car and on it's extended centerline. The tow bar would be long
enough that the tailplane couldn't touch the back of the car.

[Martin Gregorie[_4_]]

On Fri, 07 Nov 2008 18:46:29 -0800, bildan wrote:

> My thought is to eliminate the pivot at the car so the tow bar cannot
> swing left and right relative to the towing vehicle thus making the "Z-
> fold", which we call a jackknife, impossible. It will, of course, make
> the glider swing a wider turn than the car but that may be useful. Even
> though the tow bar cannot pivot about a vertical axis at the car, it
> would be able to pivot about a lateral axis to accommodate uneven
> ground.
>
> This scheme would locate the tail dolly an exact distance behind the
> towing car and on it's extended centerline. The tow bar would be long
> enough that the tailplane couldn't touch the back of the car.
>
I can visualize what you're describing and can see that it would be
gentle on the glider. However, when you go round a corner the dolly wheel
will be forced sideways. The longer the tow bar the more the wheel will
be driven sideways and the larger the forces involved will be.

The attachment at the front end will need to be fairly meaty to keep the
towbar straight. What sort of vehicle will this be attached to and how
would it be attached?

What type of glider is this for?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Doug Hoffman]

bildan wrote:

> I've watched people try to perfectly align non-castering wing wheels
> for years. The slightest mis-alignment will get worse the further the
> glider moves until they have to stop and re-align it. With a flapped
> glider, this has to put unnecessary force on the flap hinges.

My non-castering wing wheel cuffs the right aileron which is free to
move. But a snug fitting cuff will *not* move if on straight. I
achieve a perfect and snug fit by molding the cuff in place on the wing
with Great Stuff insulation foam spray. Again, one quickly learns how
to put the cuff on straight first try. It's no problem, really.


> The tow out bar itself will need some careful re-design. The
> accidents I have seen and read about all seem to involve a failure of
> some kind with the tow out bar. Mostly this is the glider tailwheel
> jumping off the bar leading to a jackknife-type accident. I like a
> tow-out bar that lets the glider roll on the tail dolly wheel. Maybe
> this means vertical-only compliance so the bar remains straight aft
> eliminating the possibility of a jack-knife.

Some have expressed concern over the diameter of the wing wheel. Any
concerns over the diameter of the tail dolly wheel?

I have built a tow-out bar for a LAK-12 and have no concern about things
coming loose such as the tailwheel jumping off the bar. Not exceeding 5
mph is part of that lack of concern.

One thing I'm not in love with, regarding the conventional tow-out bar,
is the torque applied to the fuselage between the tail dolly mounting
location and the tailwheel location. This torque is a function of the
weight of the empty glider at the tail and the lever distance between
the tail dolly cuff and the tail wheel. Your idea of allowing the
fuselage to ride on the tail dolly wheel eliminates this torque. I've
thought about this before but haven't tried anything.

Regards,

-Doug

[Chris Nicholas[_2_]]

Lak has produced a design for tail Dolly and tow bar that seems to overcome
all the above concerns. I bought one with my Lak 17.

Sorry I can’t paste a picture, so a lot of words will have to do instead.
The basic tail dolly is like many, having a cuff that goes round the boom,
also engaging with the front of the fin to stop it rotating, and a
castoring wheel.

The clever part is a horizontal tube welded to the underside of the Dolly,
with an internal diameter of about 1 inch. The two piece towbar provided
has another tube welded to its side at the end that goes on the Dolly, at
right angles to the general direction of the towbar, and it slides into
the tube on the Dolly.

Even harder describe is the way it locks in. The outside of the tube on
the bar has a ridge halfway round it at the bar end. The tube on the
Dolly has a groove. The Dolly end of the bar is inserted into the Dolly
from the left-hand side of the fin, with the bar part at about 10 o’clock
rather than horizontally at first. It slides fully in so that the ridge
on the bar is ready to engage with the groove in the Dolly. You then
rotate it, to the three o’clock, or towing, position. With no need for any
other locking devices, it now cannot come out. The other half of the
towbar slides on, an integrated spring-loaded peg holds them together, and
the outer part of the bar of course has a coupling to go on the car
towball. This arrangement keeps the fuselage and towbar in a rigid line
in plan view, allows the bar to flex up and down if the ground is uneven,
avoids any risk of jackknifing, and imposes no undue strain on the
glider.

Chris N.

[Martin Gregorie[_4_]]

On Mon, 10 Nov 2008 11:30:05 +0000, Chris Nicholas wrote:

> This arrangement keeps the fuselage and towbar in a
> rigid line in plan view, allows the bar to flex up and down if the
> ground is uneven, avoids any risk of jackknifing, and imposes no undue
> strain on the glider.
>
What a neat arrangement. Fairly obvious too, now you've described it.

Is the towbar straight or does it have a vertical bend to make sure it
always passes under the tail when you're turning right?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Andy[_1_]]

On Nov 7, 7:46*pm, bildan > wrote:
> Exactly. *This is the input I'm looking for.

I don't know where you fly but in the desert SW of USA tail wheel and
tail dolly tires are very vulnerable to punctures from thorns. This
risk extends at least from California to Texas as I've had puntures in
all those states.

An advantage of the (standard) tow bar that fits the dolly axle and
supports the tail wheel is that no small wheels are in contact with
the ground during tow out. The risk of flats is much reduced. Even if
the tail dolly tire is flat, the tow bar can still be used to get you
out to the launch point and the flat can be fixed later.

Andy

[Papa3]

On Nov 10, 12:07*pm, Andy > wrote:
> On Nov 7, 7:46*pm, bildan > wrote:
>
> > Exactly. *This is the input I'm looking for.
>
> I don't know where you fly but in the desert SW of USA tail wheel and
> tail dolly tires are very vulnerable to punctures from thorns. *This
> risk extends at least from California to Texas as I've had puntures in
> all those states.
>
> An advantage of the (standard) tow bar that fits the dolly axle and
> supports the tail wheel is that no small wheels are in contact with
> the ground during tow out. The risk of flats is much reduced. *Even if
> the tail dolly tire is flat, the tow bar can still be used to get you
> out to the launch point and the flat can be fixed later.
>
> Andy

Or, replace the tire with an airless alternative. Tail dollies seem
to know the least opportune time to go flat (like at a contest site
miles from nowhere 30 minutes before grid time).

[bumper]

Chris,

What you are describing is identical to the Stemme dolly, except the
telescoping tow bar (that allows the tow bar to be short enough to pivot
under the horizontal stab) is inserted from the right side of the ship.
Then, if the tow bar is pivoted forward, there's an offset wheel that goes
over-center to raise the tailboom so the dolly catering wheel can be
inserted or removed from the dolly. When pivoted aft, the tow bar can be
extended for towing or pushing the glider.

bumper
"Chris Nicholas" > wrote in message
...
> Lak has produced a design for tail Dolly and tow bar that seems to
> overcome
> all the above concerns. I bought one with my Lak 17.
>
> Sorry I can’t paste a picture, so a lot of words will have to do instead.
> The basic tail dolly is like many, having a cuff that goes round the boom,
> also engaging with the front of the fin to stop it rotating, and a
> castoring wheel.
>
> The clever part is a horizontal tube welded to the underside of the Dolly,
> with an internal diameter of about 1 inch. The two piece towbar provided
> has another tube welded to its side at the end that goes on the Dolly, at
> right angles to the general direction of the towbar, and it slides into
> the tube on the Dolly.
>
> Even harder describe is the way it locks in. The outside of the tube on
> the bar has a ridge halfway round it at the bar end. The tube on the
> Dolly has a groove. The Dolly end of the bar is inserted into the Dolly
> from the left-hand side of the fin, with the bar part at about 10 o’clock
> rather than horizontally at first. It slides fully in so that the ridge
> on the bar is ready to engage with the groove in the Dolly. You then
> rotate it, to the three o’clock, or towing, position. With no need for any
> other locking devices, it now cannot come out. The other half of the
> towbar slides on, an integrated spring-loaded peg holds them together, and
> the outer part of the bar of course has a coupling to go on the car
> towball. This arrangement keeps the fuselage and towbar in a rigid line
> in plan view, allows the bar to flex up and down if the ground is uneven,
> avoids any risk of jackknifing, and imposes no undue strain on the
> glider.
>
> Chris N.
>

[Chris Nicholas[_2_]]

Bumper, I didn’t realise that the Stemme towbar was that similar, never
having seen one.

Martin, the outer part of the towbar that connects to the car is cranked
in two directions, sideways and upwards, so that it never fouls the
tailfin or rudder. (It posed an interesting storage problem when I made
up a rack to hold it in the trailer!)

I think the original idea was that the sideways crank means that they
coupling end of the tow bar should be on the extended centre line of the
fuselage. I suspect that my tail Dolly was misassembled, and the towbar
fits on the wrong side, so actually the tow ball is well offset from the
centre line of the fuselage when it is all set up ready to tow. It does
not seem to affect the towing dynamics to any extent at sensible speeds.

Incidentally, I found it was possible to add some brackets so that the
towbar can be fitted to the wheel portion of my one-man wing rigging Dolly
when that is separated into its component parts. With some additional bits
of wood, it turns it into a trailer that can carry four full water
containers. I will probably take it over to Gransden Lodge some time, so
you could see it there if we happen to meet up. That said, I have not yet
tried it with a full load of water over uneven ground, so I don’t yet know
quite how well it will work in that configuration.

Chris N.

[Andy[_1_]]

On Nov 10, 10:20*am, Papa3 > wrote:
>
> Or, replace the tire with an airless alternative. * *

Trouble is that nobody yet made an airless tire that is as good as a
pneumatic tire. Foam filled tires set with a flat spot and solid
wheels are much too harsh a ride on the rocky surfaces I have to deal
with. If I lived somewhere that grass grew it might be a different
story.

Andy

[bildan]

On Nov 10, 1:30*pm, Andy > wrote:
> On Nov 10, 10:20*am, Papa3 > wrote:
>
>
>
> > Or, replace the tire with an airless alternative. * *
>
> Trouble is that nobody yet made an airless tire that is as good as a
> pneumatic tire. * Foam filled tires set with a flat spot and solid
> wheels are much too harsh a ride on the rocky surfaces I have to deal
> with. *If I lived somewhere that grass grew it might be a different
> story.
>
> Andy

I use a solid wheel from a hospital gurney that seems soft enough.

[Martin Gregorie[_4_]]

On Mon, 10 Nov 2008 20:15:06 +0000, Chris Nicholas wrote:

> Incidentally, I found it was possible to add some brackets so that the
> towbar can be fitted to the wheel portion of my one-man wing rigging
> Dolly when that is separated into its component parts. With some
> additional bits of wood, it turns it into a trailer that can carry four
> full water containers. I will probably take it over to Gransden Lodge
> some time, so you could see it there if we happen to meet up. That
> said, I have not yet tried it with a full load of water over uneven
> ground, so I donÂ’t yet know quite how well it will work in that
> configuration.
>
Very neat, Chris. I'll look forward to seeing it.

Incidently, I thought I might have seen something similar, possibly on a
two seater. Your additional details confirm that I have seen one,
probably on Allan's LAK.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Bob Gibbons[_2_]]

On Mon, 10 Nov 2008 12:30:05 -0800 (PST), Andy >
wrote:

>On Nov 10, 10:20*am, Papa3 > wrote:
>>
>> Or, replace the tire with an airless alternative. * *
>
>Trouble is that nobody yet made an airless tire that is as good as a
>pneumatic tire. Foam filled tires set with a flat spot and solid
>wheels are much too harsh a ride on the rocky surfaces I have to deal
>with. If I lived somewhere that grass grew it might be a different
>story.
>
>Andy

Several years ago I got tired of continually having to pump up the
pneumatic tail dolly wheel for my Ventus. I ended up replacing the
inner tube with a solid rubber inner tube replacement sold under the
name "No-Mor Flats". I got my tubes from Cyclo Manufacturing in
Denver, CO. While they no longer appear to be in business, a quick
google check shows a number of alternate sources for the No-Mor Flats
tubes. E.g., http://www.noflattubes.com/order.html

I used a 20" x 2" version that No-Mor Flats termed a "20B7". This tube
is for a larger 20" wheel so I had to measure the circumference of my
tail dolly wheel and cut the continuous No-Mor Flats solid tube to a
shorter length to fit inside the tire. It took a little trial and
error (cut oversize first) but a couple of iterations got it right. I
just butted the ends together inside the tire.

More details, cost is around $23. The actual diameter of this tube is
1.625" (41.3mm), and the weight of a 39 inch length is 1.5 lbs (99 cm,
0.68 kg).

No problems in over 2 years with the tail dolly, no flat spots. Maybe
a little heaver than a pneumatic tube, but well worth the avoidance of
flat tires and continual repumping.

Bob

[Barny]

Wing Wheel thoughts:
1) Combining trailer cuff is a good idea to save space if you can make
it work.
2) Caster wheel is not needed, the $150,000 ships' wing wheels don't
swivel. My previous and current wheels never needed it.
3) Tire/wheel: larger diameter is better for runway/grass transition.
Misalignment comments are correct: see it skip in the mirror, fix it
once or twice, won't happen again. Loose fit allows use on either
wing, saving you a 100' walk.
4) Runway/taxi lights versus wheel location and height deserves
consideration: If on the tip, height should be low so the wheel will
be on the pavement and other wing rides over the lights. If mid-span,
make the ship level so both tips clear the lights by an uncomfortably
small amount.
5) Due to #4, weight is a good idea.
6) Strut? My first one w/20" wheel didn't have or need a strut,
current one w/14" wheel has and needs it. It's a very tiny strut.

I think the weight, diameter and strut are inter-related considering
the need to overcome bumpy transitions. You can avoid one of the three
parameters by perfecting the other two. Large wheel, fixed leg, heavy
weight (my previous one) will bounce over most things. Small wheel,
strut, light (current one) will flex over the same obstacles.

~Bruce