Another E glider concept

Ventus_a wrote on 8/16/2020 6:14 PM:
Jonathan St. Cloud;1027640 Wrote:
https://www.youtube.com/watch?v=ZIYU2zkGQFQ

Interesting concept although on first look got to wonder if he was
dreaming of an updated, stretched and powered 2 seat Salto that could
fly him to fame and fortune (just kidding about the fortune)

I hope someone will read the thesis and tell us the goal of the concept. It does
make me wonder if the current FES could be adapted to a three blade propeller,
with all blades external as they are now. Slightly higher drag when gliding, but a
50% increase in power capability by the propeller (or more ground clearance and
some power increase).


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

The Main factors for power from a propeller are diameter, pitch and rpm, not the number of blades.

An increase from 2 to 3 blades gives at best about 10-15% more drag if the remaining is constant. However the efficiency of the propeller drops by 5-10% and this is a major drawback in electrical propulsion system for gliders.

Per Carlin wrote on 8/17/2020 12:58 PM:
The Main factors for power from a propeller are diameter, pitch and rpm, not the number of blades.

An increase from 2 to 3 blades gives at best about 10-15% more drag if the remaining is constant. However the efficiency of the propeller drops by 5-10% and this is a major drawback in electrical propulsion system for gliders.

I think something is missing in your explanation: for example, 3, 4 and 5 blades
are common on airplanes, and wind turbines routinely use 3 blades. My
understanding is tip speed is the ultimate limit on the power a propeller can
absorb, so adding a 3rd should 50% more power capability.

Take a look at this bad boy - Five blades!

https://hartzellprop.com/are-more-pr...blades-better/

The Hartzell site also discusses reasons for choosing more blades

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

When the propeller spins backwards in the demo reel, confidence that the engineers will make an airworthy aircraft is instantly flushed down the toilet.

On Monday, August 17, 2020 at 1:39:31 PM UTC-7, Eric Greenwell wrote:
Per Carlin wrote on 8/17/2020 12:58 PM:
The Main factors for power from a propeller are diameter, pitch and rpm, not the number of blades.

An increase from 2 to 3 blades gives at best about 10-15% more drag if the remaining is constant. However the efficiency of the propeller drops by 5-10% and this is a major drawback in electrical propulsion system for gliders.

I think something is missing in your explanation: for example, 3, 4 and 5 blades
are common on airplanes, and wind turbines routinely use 3 blades. My
understanding is tip speed is the ultimate limit on the power a propeller can
absorb, so adding a 3rd should 50% more power capability.

Take a look at this bad boy - Five blades!

https://hartzellprop.com/are-more-pr...blades-better/

The Hartzell site also discusses reasons for choosing more blades

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

It looks like this is a masters thesis project for a curriculum in industrial design. Of course, much of it is not functional in the ways that are important to soaring flight. But there are some interesting design concepts here that we should not dismiss out of hand.

We have to be careful about rejecting ideas that seem impractical, especially when advances in various technologies can be combined in ways that make the orthodoxy irrelevant.

The next time you find yourself yelling "get off my lawn!," stop and reflect whether the lawn is really yours.

--Bob K.

On Tuesday, August 18, 2020 at 6:42:12 PM UTC-7, Bob Kuykendall wrote:
It looks like this is a masters thesis project for a curriculum in industrial design. Of course, much of it is not functional in the ways that are important to soaring flight. But there are some interesting design concepts here that we should not dismiss out of hand.

We have to be careful about rejecting ideas that seem impractical, especially when advances in various technologies can be combined in ways that make the orthodoxy irrelevant.

The next time you find yourself yelling "get off my lawn!," stop and reflect whether the lawn is really yours.

--Bob K.

Don't confuse this with a real, aerodynamical design concept, because it is not. You will end up chasing your tail if you do.

Having disturbed the plumbing, I have a pitot leak! Being a turbo, the
glider has a pneumatic switch to select between nose and tail pitot
tubes. With nose selected, there's a leak. With tail selected, things are
much worse and I can't measure any pressure at all from the tail pitot
tube.

So should I suspect the switch or the connections to the switch? And is
it possible for the switch to have an internal fault which could cause
these symptoms?

On Wednesday, September 2, 2020 at 11:00:06 AM UTC-4, John McLaughlin wrote:
Having disturbed the plumbing, I have a pitot leak! Being a turbo, the
glider has a pneumatic switch to select between nose and tail pitot
tubes. With nose selected, there's a leak. With tail selected, things are
much worse and I can't measure any pressure at all from the tail pitot
tube.

So should I suspect the switch or the connections to the switch? And is
it possible for the switch to have an internal fault which could cause
these symptoms?

Yes, pneumatic switch can fail....first check is tubing (sometimes nipping 1/4" from tubes and reattach), maybe a switch clean/lube can fix the issue. Tube nipping is what I did in '70's/'80's US cars with emissions. Just a bit to get a better seal. My method is sorta cheap/easy....check again. Some sort of pressure/vacuum device gauge is more accurate. Yes, make sure it holds a value.....I remember a spring flight where "blowing on the probe" showed needle movement....long term showed the mouse holes in cockpit tubing.....good for me, I could fly wind noise, pitch attitude, "seat of the pants".. I did a couple hours local with no real instruments..

I've used a spare altimeter and a syringe to demonstrate sealed
pneumatic hoses.Â* You could also make a simple manometer.

On 9/2/2020 9:26 AM, Charlie M. (UH & 002 owner/pilot) wrote:
On Wednesday, September 2, 2020 at 11:00:06 AM UTC-4, John McLaughlin wrote:
Having disturbed the plumbing, I have a pitot leak! Being a turbo, the
glider has a pneumatic switch to select between nose and tail pitot
tubes. With nose selected, there's a leak. With tail selected, things are
much worse and I can't measure any pressure at all from the tail pitot
tube.

So should I suspect the switch or the connections to the switch? And is
it possible for the switch to have an internal fault which could cause
these symptoms?
Yes, pneumatic switch can fail....first check is tubing (sometimes nipping 1/4" from tubes and reattach), maybe a switch clean/lube can fix the issue. Tube nipping is what I did in '70's/'80's US cars with emissions. Just a bit to get a better seal. My method is sorta cheap/easy....check again. Some sort of pressure/vacuum device gauge is more accurate. Yes, make sure it holds a value.....I remember a spring flight where "blowing on the probe" showed needle movement....long term showed the mouse holes in cockpit tubing....good for me, I could fly wind noise, pitch attitude, "seat of the pants". I did a couple hours local with no real instruments..

--
Dan, 5J

A Cristal tube water column is almost a fundamental measuring instrument.
Make the positive or negative pressure with a syringe on a tee and check the altitude difference in time.
You can also check your ASI on some speed range with this is if you have the conversion table.