# Project Phoebe - one-seat "trainer"

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#### ypsilon

##### Well-Known Member
Hello!
When I spoke few year ago with Crossover boys on AERO (very sympatic team from Portugal) I told them, that their airplane has big problem - two motors. No way to make certification. But situation changed - this construction is actually allowed so I hope we will meet again on AERO.
I am in the camp of Topaz on this. Two engines on the trailing edge of the wing is possible but neither efficient nor easy to do. The licensing of the UL category is done through national authorities, not the easa, so what's possible in one country, might be a problem in another. Whatever falls out of the norm, will be harder to register in many countries. Maybe it works in CZ, in AT you probably will have issues. Looking at the regulations in DE, it is also not clear to me, if it works.

Look at Darek Lewek's Geko project. I think he solves many of your problems quite elegantly. He just spent too much time on it to make it really cheap (seriously: He did a great job).

#### John.Roo

##### Well-Known Member
That is definitelly nice project
I agree that is a great job done!

It is a quesiton if makes sense for me to continue
Maybe will be better to buy Geko and have fun instead of development work...

Martin

#### ypsilon

##### Well-Known Member
I think Darek isn't building this a commercial project, but just for himself. He said that he'd be willing to sell the project (I guess that means the moulds etc), and if I am not mistaken Dr. Werner Eck from Germany was interested in building this machine commercially. I don't know how far they are, but I think I can find out.
He put about 3000 hours in this project already. You can translate what the means in terms of cost. Surely not cheap. If I could fly this thing legally in Austria (and if it were available), I probably would've bought one already. It's just too cute

#### John.Roo

##### Well-Known Member
Thank you for really interesting informations... I remember that Axel project has been for sale and Geko seems to be Axel succesor.
Axel glider prototype has been for sale some years ago for arround 20T EUR - that is very good price.
If I remember well Werner Eck is producing electric propulsion systems so it could be nice "synergy" - produce composite parts in Polland and install German electric propulsion systems.

Why you can´t fly airplane like Geko in Austria?
Since Austria opened "airspace borders" for UL you can fly under German or maybe even Czech registration - am I wrong?
Normally I would say - make German or Czech UL license (better for insurance agents - same country registraiton and pilot license) and fly whatever UL you like
And if is electric even better - "0" emission is more and more popular and supported in every country.

Or buy a KIT. No problem to find experienced workers to finish it for you. Even I can help you to finish it if is composite.
Czech Republic is between Polland and Austria so no big "detour" during transport

Best regards!
Martin

#### Himat

##### Well-Known Member
You're falling into the usual trap for these projects - your "novel" solution is more-complex and heavier than the old-fashioned simple and light one. Wing-mounted engines and battery packs mean vibration and extra loads into the wing spars and spar attach mounts, plus disconnecting your control and "throttle" cable(s) every time you remove the wings. That's a likely point of failure, either right away if they're manually connected, or over time even if they're automatic hookups.

And you're doing all of this just to preserve a "pretty nose" and a fixed main gear wheel without a gear leg. Aesthetics is important, but don't wreck the rest of airplane with it, and keeping one specific part of the airplane super-simple is not a good justification for making multiple other sections really complex.

So retract the undercarriage. Or fair it and accept the longer exposed gear leg. A fixed mono-wheel gear leg for a tractor prop installation might need be only 18" long or so, once you add in the tire radius. It won't be tall enough to interfere with entry and exit of the aircraft. This solution worked for the Monnett Moni and it didn't have any trouble mounting a "big enough" propeller.

View attachment 77405

If you can do an electric propulsion system - you were against this earlier - then an FES-type solution with a larger prop and a fixed gear leg is the simplest design solution to the requirements. If you absolutely cannot stand to have a fixed gear leg sticking out of the bottom of your glider, do a simple mono-wheel retract like the RF-4, or that converted fixed-wing hang-glider we saw in a thread here earlier this month. Or do a deep fuselage, like the Scheibe SF-24 Matthew posted about earlier. A cleaned-up, modernized version of that aircraft would meet the stated requirements for this project easily.

If you use IC propulsion (which you were promoting earlier), the problems of wing-mounted engines only multiply. Removable wings become highly impractical if the fuel is housed in them, and if it's housed in the fuselage, you've now got fuel disconnects to deal with, plus the throttle cables and ignition/starter circuit.

Keep it simple. If that means you have to give up a "glider nose" or a no-leg mono-wheel main gear, so be it. Those are much smaller sacrifices than those imposed by wing-mounted engines in glider operations. You can still get 30:1 (or better) performance with a traditional tractor prop, even with an ICE. The 35:1 Carat A is a perfect example of this, and a reduced-cost version with simplified main landing gear would be yet another good solution to this requirements set, on top of the Scheibe SF-24 and Windex already mentioned.

View attachment 77404

Just my opinion. Your mileage may vary, of course.
One front or two wing mounted motors depend on one thing, the availability and relative price of one 20kW motor and controller versus the price of two 10kW motors and controllers. When it comes to design and engineering there are pros and cons of both possibilities.

Probably the largest hurdle is that a “cheap” sailplane to base a conversion on is certified and thus not viable due to the red tape. Given the availability of a non-certified or experimental sailplane the 10kW motors are available to anyone with the money and if asked no one will raise an eyebrow on the “large scale model” answer.

I do see two pros with the over wing pod motors:
• One is the possibility to use model airplane folding props
• Two to use cheap model airplane lipo batteries and design the pods in a way that a battery fire does not damage the aircraft.

The con is structural, especially with the pods aft on the wing with pusher props.

Wiring to the pods is a non-issue in an experimental airplane if the batteries are placed in the pods. After all the equipment is designed for radio control, and so I would arrange it.

As for FES, Front Electric Sustainer, look at this
http://www.front-electric-sustainer.com/index.php

#### John.Roo

##### Well-Known Member
Thank you Himat,
you pointed exactly the difference.
Price of 2x 10 kW propulsion is definitelly lowe than 1x 20 kW motor BUT only in case that is used "RC model" technology.
Reliability of 20 kW electric motors used in trikes or one seat gliders (from MGM or Geiger) is well tested.
I am affraid that typical 10 kW electric motor from RC world (for exampe this one https://hobbyking.com/en_us/turnigy-rotomax-150cc-size-brushless-outrunner-motor.html) will have problem with reliability and lifetime. It is necessary to realize, that RC model is normally not used for hours. Typical RC model flight is in minutes and few times a month. However seems that for example MVVS (already mentionned MVVS E100) are existing also in UAV versions. I don´t know exact difference but I am interested to find more info directy from MVVS. Hopefully will be produced with respect to achieve higher quality - longer lifetime etc..... The same is valid for a controller.

Folding model prop is nice bonus - simple and aerodynamic.
All this will request a very light construction so I am not plannig to use "certified glider".
Battery comes to be dangerous when you try to take too much power from small battery or when you want to recharge it too quickly.
I am using 50 kg Li-Po battery and on 144 V I had max. current 220-230 Ams and that is a lot.
"Cheap" model Li-Po... probably not I prefer to use something I have good experience with.
So due to battery size (and weight) will be probably a problem to have it in the pod together with controller and motor...

Yes, HPH 304 (and new TwinShark) are beautifull gliders

Best regards!
Martin

#### lr27

##### Well-Known Member
If you're using model airplane motors, you can use even more of them. Seems to me that if you go this way, a tractor pod is the way to go. With relatively short props, the motor doesn't have to be very far forward of the wing for folding. Even less if you add a spring to fold the prop forward. c.g. of pods should line up with 25 percent local chord, I think. Fire issue might be interesting. Maybe we'll see a battery technology that's a bit safer. Lithium iron phosphate is safer but doesn't store as much energy per kg.

#### BBerson

##### Well-Known Member
HBA Supporter
Two or more motors can be geared to one prop shaft.

#### John.Roo

##### Well-Known Member
Hello!
First flight of D-14 in 2011 has been done with LiFePO cells. Definitelly too heavy.... Li-Ion is probably best way. Lower curred load / 1 cell, but more safe in compare with Li-Po. And about the same energy density. And used in electric cars = hopefully lower prices in future.

More motors.... I noticed some projects using really a lot of motors.
Actually I don´t have comparizon between "more very small props / two small props / one big prop".
My feeling says that best is one bigger prop and that more motors = more problems
So I need some personal experience.
Therefore I want first to test performance of 1x 8-10 kW model motor + folding prop. Thrust, endurance, heating...
I tested "in front" folding prop on 100 hp Rotax and it was smooth opening and good feeling during gliding (only one flight done so no detailed L/D measurement).
http://www.duc-helices.com/produit.php?id_produit=1081&id_rubrique=103

Two or more e-motors on one shaft?
If remember well Geiger company is using that design. You need two controllers and as advantage is mentionned higher safety.
Again - no personal experience. I have to visit in April their stand on AERO for more details

At the beginning (2010) we produced our own electric motor. It was 44 kW BLDC.
Really good experience with one very important result - next time I prefer to buy finished product
Why? Motor is only one part of electric propulsion puzzle. You need whole system - motor, controller, power source (battery), chargers etc.
All components must be compatible.
It looks simple to connect all together according to "producer supplied data" but is far from reality... especially for power above 15 kW.
Therefore I repeat - personal experience is necessary

Best regards!
Martin

#### saini flyer

##### Well-Known Member
Martin, thanks for posting your experiences, ongoing work, and future direction on HBA. I saw your video here (https://www.youtube.com/watch?v=Q_u-rlkcVqk&feature=youtu.be) and would appreciate it if you can answer some more questions:
1. Is the Helices propeller (like carat) available to buy and ship to the US? Looks like the price is about $3500 based on the link you provided. 2. Are there other flying examples of the propeller? 3. Is it good for the 914/915is engines too or only for 912? 4. Can this be used on a regular LSA aircraft or is only made for motorgliders? 5. I understand your take on the complete electric powerplant but Mark (Earthstar aircraft) did exactly that by going with a zero motorcycle powerplant for his egull. There are many used motorcycles for sale today at around$5k- \$6k with 30kW- 40KW motor including everything. They are now delivering thousands of these per year and I am intrigued why more people are not adopting that powerplant as is!

Hello!
First flight of D-14 in 2011 has been done with LiFePO cells. Definitelly too heavy.... Li-Ion is probably best way. Lower curred load / 1 cell, but more safe in compare with Li-Po. And about the same energy density. And used in electric cars = hopefully lower prices in future.

More motors.... I noticed some projects using really a lot of motors.
Actually I don´t have comparizon between "more very small props / two small props / one big prop".
My feeling says that best is one bigger prop and that more motors = more problems
So I need some personal experience.
Therefore I want first to test performance of 1x 8-10 kW model motor + folding prop. Thrust, endurance, heating...
I tested "in front" folding prop on 100 hp Rotax and it was smooth opening and good feeling during gliding (only one flight done so no detailed L/D measurement).
http://www.duc-helices.com/produit.php?id_produit=1081&id_rubrique=103

Two or more e-motors on one shaft?
If remember well Geiger company is using that design. You need two controllers and as advantage is mentionned higher safety.
Again - no personal experience. I have to visit in April their stand on AERO for more details

At the beginning (2010) we produced our own electric motor. It was 44 kW BLDC.
Really good experience with one very important result - next time I prefer to buy finished product
Why? Motor is only one part of electric propulsion puzzle. You need whole system - motor, controller, power source (battery), chargers etc.
All components must be compatible.
It looks simple to connect all together according to "producer supplied data" but is far from reality... especially for power above 15 kW.
Therefore I repeat - personal experience is necessary

Best regards!
Martin

#### John.Roo

##### Well-Known Member
Hello!
For me is really interesting to know opinion of other pilots and designers, so I am glad for place like HBA
The video on youtube has been done by my friend Yvon during flight test of propeller he designed.
During that test we found few small details (position of screws, elasticity of silentblocks etc...) that had to be re-designed and changed.
Generally is this system working nicely. Unfortunatelly I did only one flight so I don´t have report about some detailed measurements.

1) I beleive that should be possible to make shipment to US without any problems - I beleive that even other types of DUC props are known and sold in US.
2) I know that Yvon did a most of flights on his Lambada with HKS engine and we did test flight on Phoenix with 100hp Rotax.
3) Sorry, I don´t know... I have to ask Yvon.
4) Generally I don´t see any problem to use this prop also on other LSA airplanes. Only on motorgliders makes more sense due to lower drag (higher L/D) expected during gliding.
5) Interesting info! 5-6K USD for complete 30-40 kW propulsion sounds really interesting. I have to find more details

I don´t speak French so I used Google - there is written that to buy prop you have to contact Yvon directly.
yvon.paugam29@gmail.com

I quickly opened some websites with used motorcycles and seems that prices of used Zero motorcycles in EU are starting on 7 500 EUR (2014 Zero FX) = approx. 30% higher price than in US. Anyway would be interesting to know more about used motor (weight, size, RPM range etc.) and of course also about used battery (capacity / weight / size) so I wil use Google to make small research Thanks!

Best regards!
Martin

#### saini flyer

##### Well-Known Member
John, this is a dormant thread but I saw you mention this in the e-soaring thread and wanted to suggest a different alternative:
Let there be a large folding prop with electric motor in tractor configuration (like FES but with larger prop) and use a hubmotor in single wheel landing gear for the take off. As soon as you are a few feet from ground, turn on the tractor motor for full electric torque. The same batteries can be used for hub motor and prop motor!!
This cant be done with an ICE as the prop need to spin out for getting higher torque but with electric motor this should be trivial. This keeps a small undercarriage as well as good prop efficiency intact...

#### John.Roo

##### Well-Known Member
Hello!
I agree to go back to simplicity....
Single motor in the front, folding or feathering prop with large diameter.

However I have personally problem with monowheel undercarriage.
Idea of electric motor in wheel is perfect.
Airbus used this solution on their e-Fan...

...and if I remember well it was also used on GlowFly project

Unfortunatelly monowheel config. brings two problems:
1) monowheel has not nice characteristic during crosswind landings + not easy taxiing
2) it should be very high in case you want to use big prop in tractor propulsion on "glider like" airplane = aerodynamic nose near the ground.

But from the other point of view - low monowheel + large prop could be used on used on glider like Windex.

Don´t forget that traction of wheel will decrease with speed as wing starts to generate lift. Would be interesting to test how high you can "jump" if you use for takeoff only electric motor in wheel.