Some SZD-55-1 Questions

On Monday, July 15, 2013 10:07:27 AM UTC-5, Dan Marotta wrote:
Do tip wheels *have* to be droppable? My LAK-17a has what amounts to roller
blade wheels in an aerodynamic fairing glued to the underside of the wing at
the tip. It also makes moving the glider around on the grid easier since
you don't need someone to hold a wing.


Yeah, contest pilots hate to add any drag. Also a wing down with full water will take a long time to pick up, and a wing down with half water is a non-starter. So pogo sticks that keep the wings level would work better. Retracting would be nice, but we need something for the after market. 1-26 /2-33 style wheels on a cuff that fell off would work. Perhaps someone can think of a way to fold the wheel or pogo stick back into the wingtip vortex or retract it. I'm not a mechanical genius, just sick of dropping wings at contests!

John Cochrane

John Cochrane

On Mon, 15 Jul 2013 09:13:13 -0700, cochranejohnh wrote:

Yeah, contest pilots hate to add any drag. Also a wing down with full
water will take a long time to pick up, and a wing down with half water
is a non-starter. So pogo sticks that keep the wings level would work
better. Retracting would be nice, but we need something for the after
market. 1-26 /2-33 style wheels on a cuff that fell off would work.
Perhaps someone can think of a way to fold the wheel or pogo stick back
into the wingtip vortex or retract it. I'm not a mechanical genius, just
sick of dropping wings at contests!

A replacement tip fairing/winglet with a 'thin wheel on a stick' that
'retracts' by swinging up in line with the tip chord should work and be
reasonably low drag. However, I see two problems:

- controlling retraction if you don't want to string wires through the
wing or use a radio.
Maybe a GPS receiver to trigger retraction at 45 kts?

- the wheel would need to be fairly large (150mm?) to survive
operation off grass or rough surfaces. Not a big deal, but you're not
going to get rid of that wetted area and a thin disk would be lower
drag than something with spokes of almost any design.


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

At the recent Region 9 Contest in Moriarty I saw one glider with a stick
held to the under side of the wing with a suction cup. Looks like it would
fall off if the wing runner failed to remove it. I asked about it and was
told that he got it at a camera shop.


wrote in message
...
On Monday, July 15, 2013 10:07:27 AM UTC-5, Dan Marotta wrote:
Do tip wheels *have* to be droppable? My LAK-17a has what amounts to
roller
blade wheels in an aerodynamic fairing glued to the underside of the wing
at
the tip. It also makes moving the glider around on the grid easier since
you don't need someone to hold a wing.


Yeah, contest pilots hate to add any drag. Also a wing down with full water
will take a long time to pick up, and a wing down with half water is a
non-starter. So pogo sticks that keep the wings level would work better.
Retracting would be nice, but we need something for the after market. 1-26
/2-33 style wheels on a cuff that fell off would work. Perhaps someone can
think of a way to fold the wheel or pogo stick back into the wingtip vortex
or retract it. I'm not a mechanical genius, just sick of dropping wings at
contests!

John Cochrane

John Cochrane

A cheap toilet plunger is fairly common in many countries for a landout takeoff aid. If it falls off after the launch, who cares.