Earthstar Forums

As Mark keeps pointing out, added weight causes more induced drag, so any
benefit in top speed will be reduced.

Constant speed VS fixed pitch prop: the eGull has an advantage here since
the prop can be pitched for speed while the high low-rpm torque still gives
good thrust during take-off. On the other hand, unless I go Experimental,
it would be illegal for me to go that fast anyway...

One area of further aerodynamic improvements may be the wing roots.
Improvements there could have additional benefits by smoothing the air
entering the prop disk.

sure it works when Bugatti built it too. the replica ought to fly anytime now. all I can make out is better propulsion efficiency that seems to win over weight penalty..

https://www.eaa.org/en/eaa-museum/museu ... -100-racer

we'll reduce throttle to 120 knots then to stay within limits. which ones are the 150mph Vne wing Gulls then?

Yes, the wing root. There is not much room for improvement ahead of the engine cutout but there is several times more drag at the cut out and engine than the total drag of the rest of the plane. Improve that area and you will go a bunch faster. That is if your prop can turn fast enough to continue to push at the higher speed.
A fixed pitch prop optimized for climb will have to turn really fast at high speed. Electric motors are rated in KV
Meaning that they will turn so many revs per volt. So if the prop were set for 3700 motor RPMs 63 mph than at 100 mph it would be turning about 5700 RPMs. To produce full torque at this rpm the voltage will need to be elevated to 130 v. But full torque is not needed to push the eGull at 100 mph. This is why we set the controller program to limit top rpm there by controlling top speed to keep it within the ultralight limit of 63 mph . Yet still havering full climb power and and enough pitch in the prop to allow for an efficient cruse. Going fast is fun,
But, the ultralight category allows us such freedom and economy that it is really worth some limits. Just think of the peace of mind that this speed controlling technology can bring to your flying experience, next time you see a traffic cop shine his radar gun at you.
Any way, a consciences ultralight pilot is a free pilot.
Happy Flying
Mark Beierle


Sent from my iPhone

Regarding the induced drag comment earlier: Induced drag (drag due to lift) is only relevant at high lift coefficients (low speed), where Parasitic drag (drag due to shape and skin friction) is dominant at high speeds. The added weight would indeed cause significantly more drag (and more thrust required) at landing and climb-out (plus the weight works directly against lift), but at higher speeds, it would mean less in terms of overall drag, and hence thrust resistance.

Ah, yes . . . . . . . ., the wing root! I can surely attest to a speed gain by closing up the gap at the wing root. One day a while back, (years?), I was sitting under the Gull right wing looking at the gap and I thought that is huge! Other airplanes are completely filleted at the wing/fuselage junction, and we could be too by adding some fillets (fairings). Back when we were ultralights, the gap helped keep our speed down, but now that we can also be LSA’s with a new top speed of 138 mph in that class, why knot fill the gap and see what happens? Oh, and the prop, my ultralight (Phantom owners) friends talked me into pitching the prop for maximum rpm static thrust on the ground tied to a fire hydrant. And of course I ran out of prop at about 80 mph. Returning to my hangar, I started adding more pitch and doing trial speed runs and found that pitching to about 5900-6000 rpm static gave me the top speed back. Using the Ivo in-flight adjust gives us the opportunity to fine tune the top end or climb performance. Oh, and I still bury the 120 mph A/S easily, and cruise at 100 mph and about 5400 rpm. Not bad for an old 503.
kb

An eUltragull will be awesome too!
half the vortex drag, 150mph already, wheel pants&fairings yet to go in, no boom, the tail wing looks higher than tail of the Gulls today ;) wonder if it had the same airfoil too

there are already three boxwings flying again these days, synergy, flynano and prandtlplane!

An eUltragull will be awesome too!
half the vortex drag, 150mph already, wheel pants&fairings yet to go in, no boom, the tail wing looks higher than tail of the Gulls today ;) wonder if it had the same airfoil too

there are already three boxwings flying again these days, synergy, flynano and prandtlplane!

Hi the Ultragull had the NACA 23012 airfoil. Same as Cessna used on most
Of there planes.
Stalls at 60 mph but can be flown controllably and maintain flight at 45 mph. Roll rate was 365 degrees per sec. Cruse nicely at 125 mph.
On a 447 Rotax. This version nada plane flap on the front wing as an elevator and due to short wrist acting control stick needed an arm restler to control it. Later version has follower flap and floor mounted control stick and very light Elevator forces. Flys like a nimble fighter jet.
It will fit on a trailer with out disassembly sideways.
Happy Flying
Mark

Sent from my iPhone

What is that, an early prototype, interesting looking little plane, looks like it would be a bitch to build

biplane without a tail. Bitch to design, easier to build; there was a sunny boxwing, late last century too, on the other side of the pond, took just 80 hours to build!