soaring/e gull

[raystl1]

Hi guys,


I am very impressed with he Earthstar line and am particularly interested in building a 28 ft egull. While trying to determine if the electric capabilities acan meet my 'needs', as an ex glider pilot the soaring possibilities is a bonus.


What is its soarability? The slow stall speed should help a lot. The L/D is published but I have not seen the speed at which that occurs. Does anyone know its minimum sink rate and its airpseed?



Thanks,
--Ray

[mkoxxy]

I do not have glider training, but the good L/D ratio is real. With my
smallish battery, I try to take advantage of every bit of lift I can find,
and I use a variometer. eGull operators have the advantage that they can
adjust the power level very smoothly, down to no power, and then into
regen. That allows me to take advantage of weak thermals to stretch my
"fuel". So far, my battery pack weighs 90 lbs, but I am upgrading to a
larger (= heavier) battery, which may affect my sink rate.
Martin

[jaimesadasalinas]

I do have a lot of sailplane experience

L/D ratios are not the only parameter to take into consideration.

An L/D of 12 is nothing that will allow you to do cross country sailplane
flying

It will be very hard (but not impossible) to reach the next thermal

With a Schweizer 1-26 and its 1:23 L/D ratio you barely reached the next
one at the correct altitude above ground for optimal flying.

Hang Gliders do reach the next thermal with Max L/Ds in the order of 12-17

I out climbed a Glasflugel Libelle H-201 (Max L/D = 34) with a Schweizer
1-26 (Max L/D = 23). He had to

I out climbed many times a Schemmp-Hirth Nimbus 3M (Max L/D = 50, Min sink
100 fpm ) with a Janus CM (Max L/D = 43, Min sink 140 fpm)

Any buzzard with a Max L/D of, say, 8, would out climb me

The reason for this ?

Its the fact that thermals have very strong cores and weak outer areas and
that slower flying which allows for smaller radius circles keeps you in the
strongest part of a thermal

In all the examples above it was the slower stall speed sailplane which can
make small radius circles that came out ahead in climbing rate, regardless
of having a higher minimum sink rate or a lower max L/D.

So, if you want to use a single thermal, look for very slow stall speeds
and forget Max L/Ds and even minimum sink rates as a general rule.

If you are doing ridge or mountain slope or cloud street soaring its the
minimum sink speed what you are looking for.

But if you are planning to do cross country soaring, there is no substitute
for higher Max L/Ds.

Hope this helps

[raystl1]

Thanks for the great info guys.

Jaime, I think the comparison to the 1-26 is probably the most directly relevant. The stall speed of the 1-26 is 28 mph, very close. Out thermaling that is impressive (at least to me). I too remember being humbled by turkey vultures, regardless of what I was attempting to soar.

What is the minimum sink speed in level flight? From that I can figure out the thermaling speed for different bank angles?

Martin, for the range 'needed', I will use the biggest/heaviest battery available. I believe that is 170 pounds. This leads me to the only potential show stopper for me. My airfield does not have electrical power. I will need to remove the battery between flights and charge the battery at home. I am envisioning a cart/dolly/chair contraption would need to be constructed as well as transfer mechanism, perhaps using a transfer board, to load the battery to and from my car. I would leave the battery in my car to charge at home. Has anyone dealt with this issue already?

Finally, a question for both of you... what type of variometer do you use/recommend? Related to that, is a total energy variometer needed?

Thanks for your help so far.

--Ray

[mark_drz]

Harbor Freight has inexpensive generators that could be much easier than removing, toting, charging, replacing versus toting a generator (and fuel). Could even leave the generator at the airport if could be secured.

My $.02

Mark Drzymkowski

[mark_drz]

Plus no tow plane and can go with a purpose which is fun

Mark Drzymkowski

[raystl1]

I believe a full recharge of a Z14.4 would take ~12 hours either at the field or at home. Using the second charger option from Zero would only reduce time to 6 hours. Too long for my unattended airstrip.

There might not be a practical way to constantly remove the battery, but I hope not. Have not given up yet.

--Ray

[earthstaraircraft]

Hi Ray
Solar panels?
Happy Flying
Mark

Sent from my iPhone

[raystl1]

Hi Mark,

Several folks at my airfield use solar panels to keep there 'normal' aircraft batteries top up.


To get a ballpark idea of the cost and size of a solar charging system (already having the batteries) I used data for the electric Pipistrel Taurus. They have a trailer for that craft with the option of a solar panel charging system (6 panels). The solar option costs 6900 euros, approx 8300 $US. This allows them to charge their 7.1 kWh battery in a minimum of 12 hours. So for a zero 14.4 kW, 24 hours can be estimated.


If I flew once a week for an hour or so, I would expect the battery could be frequently be fully recharged even with my less-than-ideal solar climate in New Brunswick, Canada. Back to back flying days would not be possible.


Fort the freedom to experience the freedom of flight more often, I still need a battery transfer mechanism. But I am still optimistic. Already I know the battery can be installed once. Just need to find a way to do that more often.



Currently I imagine a sliding or rolling transfer surface permanently inside gull and a small wheeled (fork) lift to transfer the battery form plane to car.



Hopefully you wont tell me that the plane needs to be disassembled to get the battery out.


--Ray

[earthstaraircraft]

Hi Ray
You can fabricate a battery transfer system. We use a common cherry picker hoist from Harbor freight or auto parts stores.
Also if you fly for half an hr than it will only need half the time to charge.

Happy Flying
Mark


Sent from my iPhone