Wingtip to Runway light protector Concepts

Stemme gliders run in the $250,000 range, color me jealous.

Good Lift,
Scott

I think the original poster of that description was referring to my
Stemme S10-VT
https://www.dropbox.com/s/vyx7bkqzjqfiipt/IMG_20160327_100018984.jpg?dl=0
which has conventional landing gear, i.e., two main gear and the tail
wheel. Sitting on three wheels, it's pretty level though the 75 foot
wings can rock up and down quite a bit in winds.

On 1/5/2017 11:47 AM, SF wrote:
OK, I'll Bite, WTF is a self leveling glider?

After our Grob's encounter with a runway light, we no longer condone attempting to roll off the runway in a club ship. Stop it on the runway, get out, and push it off. Not a 100% guarantee, but the collision speed will be much lower.

SF

--
Dan, 5J

On Thursday, January 5, 2017 at 5:55:27 PM UTC-8, Scott Williams wrote:
Stemme gliders run in the $250,000 range, color me jealous.

Good Lift,
Scott

Scott,

Maybe 15 years ago . . . a new Stemme will be about $400,000 base price now, so add about 40K more for average equipped. Your jealous color will be well hidden beneath that mound of cash.

bumper
MKIV high tech yaw string and QV

Got it, I have one flight in a Stemme, Now that I think of it, it was sorta self leveling. Wouldn't be the first description of it that would come to mind though.

While we are at it Don't forget the Caproni's two side by side main wheels. I have one flight in that one. I remember thinking that the Caproni may be the only glider I know of that an experienced pilot couldn't land safely without several instructional flights first. And, the only glider I know that the vario is the only indicator you have for detecting 5 Kt. thermals. The Caproni didn't see to offer any clues via the seat of the pants at all when we ran through one.

Neither of those flights left me with a burning desire to go out and buy either one. I prefer smaller and lighter.

SF

After about 600 hours in a Caproni 21S, I don't know what you are talking about...

Seriously, retractable pogo sticks are not such a bad idea...

After a few contest crashes in the early 2000s involving full water, cross-downwind, high heat, high altitude takeoffs, and ineffective wing-runs it occurred to a number of pilots that the concept "run the wingtip" started in KA6s, and sooner or later there is a limit. There was a lot of discussion about ATVs, roller blades, launch devices, but perhaps that was over beers on rest days. In any case it didn't go anywhere.

Retractable pogo sticks or wing wheels would pretty much eliminate wing drop on takeoff crashes, ground loops, etc. And on landing too.

John Cochrane

But John, wouldn't a pogo stick make it difficult to do directional corrections or turn off the runway or compensate for crosswind?

I'm thinking my gas jet would leave the pilot with more control on the runway and would probably be a lesser burden to include in a wing (cheaper).

Good question. I was thinking mostly of preventing wing down groundloops and loss of control. There, having a pogo stick that lets one wing be, say 3 feet off the ground and the other up lets you keep upwind wing down. Directional control is usually by rudder, not putting a wing down -- that's when you lose control!
Such pogo sticks need not be at the tips. They could be attached mid span.
But I like the jets idea. Since this is about preventing a rare loss of control event, you don't need much. But you do need some -- maybe 100 lbs of force for a few seconds. And how do you keep it from getting too much momentum and pushing the other wing down -- needs delicate control.
Wing drops on takeoff are a continuing problem at conteststs. Yes it's minor, only one major incident so far (tonopah), but that's more because we are careful to keep spectators out of the way of the errant gliders.

On Saturday, January 7, 2017 at 11:30:04 AM UTC-5, Steve Koerner wrote:
But John, wouldn't a pogo stick make it difficult to do directional corrections or turn off the runway or compensate for crosswind?

I'm thinking my gas jet would leave the pilot with more control on the runway and would probably be a lesser burden to include in a wing (cheaper).


https://en.wikipedia.org/wiki/Cold_gas_thruster

run the numbers on specific impulse.

best,
Evan

https://en.wikipedia.org/wiki/Cold_gas_thruster

run the numbers on specific impulse.

best,
Evan

Damn. I knew somebody would do that to me. OK then, here goes some crude top level physics...

I'll start with my own guesstimation that 15 lbf near the wingtip for 3 seconds will be enough to get over the runway light. That's an impulse requirement of 45 lb * sec.

I don't know anything about designing nozzles but for the sake of argument, I will send my gas out at 89% of the speed of sound = 1000 ft/sec.

Impulse relates to change of momentum as J = delta m * v. Solving for the mass of gas flow required: m = J/v = 45/1000 = .045 slug.

The density of plain air at seal level is .00238 slug/cu ft. But sense we're using oxygen instead of air, we get a bit more density, like .0027. So to relate the required mass to the sizing of oxygen bottles as we are normally familiar with: .045 slug / (.0027 slug/cu ft) = 16.7 cu ft. Doable! You saved your wing for the cost of an oxygen refill.