Author Topic: Outside the box design thinking (Read 2473 times)

Mike Scholtes · « **on:** May 28, 2010, 05:18:35 PM »

Given that with electric the motor(s) can be mounted nearly anywhere, and the battery can be located nearly anywhere, it seems we are freed from the ancient planform restrictions of IC designs where the best flying models have evolved to look pretty much alike, basically the WWII fighter planform.

Does this design freedom give us a meaningful advantage? Would four contra-rotating motors along the wing TE be an improvement over one in the nose? How about one in the nose and one in the tail, ala' Dornier 335 or Cessna 337? Or in the wing tips? With a completely blank sheet and the ability to put the thrust anywhere, what would be optimal? Since nobody has tried much of this it is all theoretical, but that's where the fun is.

Tim Wescott · « **Reply #1 on:** May 28, 2010, 05:49:59 PM »

Well, between 1903 and today there were a whole bunch of experiments done (many in the public eye and with some investor's money) about where to put the motors etc., and what you see are airplanes with a single motor on the nose, and airplanes with multiple motors mounted on the wings. Sometimes you'll see multiple motors on booms, but I can't think of any new planes (except for the Rutan Boomerang) that does that.

I think your most likely roads to success are:

Just what we have now, boring as it is
A twin, with or without contra-rotating props -- and if you use contra-rotating props you have to mess with finding matched pairs
What we have now, but with contra-rotating props to alleviate torque and P-factor issues -- but I'll bet it matters what direction the front prop is rotating!

Where I think electrics do[/] make a huge difference is for scale -- Imagine how much easier it'll be to balance an F.E.2!

Dennis Toth · « **Reply #2 on:** May 28, 2010, 06:20:50 PM »

Guys,

Actually, I think we might have somethings that the IC designs can't easily do. Most of the IC designs have evolved to facilitate weights of components and placement/structure to support the "stunt" type engine run. We on the other hand have light front end components (motor) and unrestricted location of are heavy component (batteries) which is closer to the CG. Our components can be laid out to allow trimming of both the horizontal and vertical CG via movement of the battery. For a ship designed strictly for electric we can adjust our thrust lines to minimize pitching moments have cleaner shapes for fuse and appendages layouts. We can also explore the mutli motor approach either tractor or pusher. So far we have not had a pure electric design something that is designed around clean aerodynamics rather then engine run. The next couple of years will be interesting to see what is developed.

Best, DennisT

Dennis Adamisin · « **Reply #3 on:** May 28, 2010, 07:04:22 PM »

Certainly more things possible - and motor cooling seems to be a little easier and-or less critical than on IC so the noses all look different. I am STILL getting use to sketching fuselages without chin scoops!

Mike Scholtes · « **Reply #4 on:** May 28, 2010, 07:44:14 PM »

Yes, Dennis T states it more elegantly than I did, but that is certainly what I am getting at. We have the freedom to use, say, four lightweight motors placed anywhere on the airframe (smaller motors that are maybe equivalent to a .15 IC engine, not the bigger AXi and Hacker and Turnigy motors that are .60 equivalents) and to locate the battery (or batteries, as by using several lighter, smaller batteries in series) pretty much anywhere. We will probably soon see wings designed to accommodate batteries in them, by use of composite materials that have far more strength than balsa and ply. I imagine we will have to use wings that look like wings so long as the object is to fly the stunt pattern with precision and repeatability, so that won't likely change much, and the stab/elev needs to be a certain distance behind the wing CL and CP to get the stability and leverage to rotate the model, so that probably won't change much. What I see maybe changing a lot is where the propulsion units are placed and where the batteries are placed. Fun to think about. And of course we may end up with an E-Trivial Pursuit as the ultimate planform, who knows?

Kim Doherty · « **Reply #5 on:** May 28, 2010, 09:23:49 PM »

Quote from: stuntguy13 on May 28, 2010, 06:20:50 PM

Guys,

For a ship designed strictly for electric we can adjust our thrust lines to minimize pitching moments have cleaner shapes for fuse and appendages layouts. We can also explore the mutli motor approach either tractor or pusher. So far we have not had a pure electric design something that is designed around clean aerodynamics rather then engine run. The next couple of years will be interesting to see what is developed.

Best, DennisT

Dennis,

The plane I flew at the 2006 W/C's in Spain (see below) was the first "purpose built" electric powered FAI F2B Stunter. EVERYTHING about SHOCKWAVE was optimized to capitalize on the electric power train. Paul's planes are "purpose built" for electric power and I am sure there are others. We choose our planform because that is what works best. Gimmicks need not apply

Kim.

Dennis Toth · « **Reply #6 on:** May 29, 2010, 02:06:52 PM »

Kim,
Ops sorry, (I knew that) your developments in electric specific design and power package have been a great help. What I was getting at is I haven't seen many published or kitted electric specific ships (exception Mike P's Silencer) that I am aware of. There have been lots of conversions but much electric only. I do believe that as more people get into electric there will be some interesting layouts for electrics, some gimmicks will be tried, but mostly just good old cut and try development. The development work that you and others have done have already moved the sport and technology forward, thanks.

Best, DennisT

Kim Doherty · « **Reply #7 on:** May 29, 2010, 06:21:44 PM »

Thanks Dennis,

I completely agree with you. While there is no question you can re-engine an existing IC powered model and achieve very good results you will still be lacking the refined edge that a purpose built design provides. You only need to look at Paul's line of electric powered models. (five in all) The IMPACT is a defining model, highly refined and capable of laying waste to the competition in the right hands. Paul's first model was an electric powered IMPACT (which was no slouch as an IC powered model). So why then did he feel that he needed to refine and improve the model over the next four iterations? Simple, because as he learned more about the system and analysed the performance it was obvious he could do better and has in a very big way. (Potential U.S. team trial pilots for the 2012 W/C's should run home to their mommy's before they get hurt

)

Kim.

bob branch · « **Reply #8 on:** May 29, 2010, 09:30:52 PM »

Just because you can does not mean there is an advantage though. Yes motors can be mounted elsewhere but when you look at the requirements of the event I am not sure there is an advantage. Bringing weights to the cg lets you pivot more quickly around the cg, but this is not combat. It requires a considerable amount of dampening to motions and requires that direction changes be totally free of oscillations. Moving all masses to the center of mass will increase oscillations and decrease damping. We went thru this in racing sailboat design in the 70's and 80's as lighter composites became a reality. Fast yes. Uncomfortable... horribly. The things would not stop pitching. Made a lot of folks sea sick. Two boats I had during the period were serious fast, but the crew had to take anti motion medications before leaving the dock if the wind was going to be over 12 and they were all experienced sailors. You can feel the same thing by just trimming your plane tail heavy. You over rotate on maneuvers and pitch dampening goes away. Not a real fun plane to fly in our event.

I'm not trying to stifle creativity. But you have to study the effects you are going to end up with. There have been flying wing plan forms for stunt and if I am not mistaken, pitch dampening was an issue there as well. The designs have a lot in common even since the mid 50 to this day. For specific applications things tend to be fairly similar that work.

bob branch

Mike Scholtes · « **Reply #9 on:** May 29, 2010, 11:18:37 PM »

I tend to agree that the models will continue to have the layout we now regard as optimal, for exactly the reasons Bob mentions and which I noted in my opening post. So long as the object is to fly a competition-level stunt pattern in front of human judges (not a digital imager that puts your pattern into a software program and spits out your objectively unassailable score) we want to see rotation followed by a cessation of rotation followed by a straight segment, all of which pretty much dictates a model like what we see today. But I am still intrigued by the opportunity to put the powerplants elsewhere on the airframe. The battery may go in the nose where an IC engine normally is mounted to keep the dampening effect of mass at that location. Phil Granderson is rumored to be working on something "outside the box" but which won't fly this season. We in NorCal will get the first look.

Tim Wescott · « **Reply #10 on:** May 30, 2010, 01:54:41 PM »

Hanriot H110 pursuit? Either a fresh design from original: http://ww2drawings.jexiste.fr/Files/2-Airplanes/Allies/4-France/01-Fighters/H.110/H.110.htm or the Sarpoulis version that showed up in the March '77 Flying Models? The original had the engine in the nose with a driveshaft and a junk engine in the back for a prop driver; with electrics you could achieve balance without having to do that.

It's probably the closest thing to a suitable design for stunt that is really out of the box, and it has the advantage that it can be made to be good looking (at least the Sarpoulis version looks nice -- the pictures of the actual plane are a disappointment!)

And you'll have battery cooling covered, hands down.

Tim Wescott · « **Reply #11 on:** May 30, 2010, 01:58:05 PM »

Quote from: Tim Wescott on May 30, 2010, 01:54:41 PM

Hanriot H110 pursuit? Either a fresh design from original: http://ww2drawings.jexiste.fr/Files/2-Airplanes/Allies/4-France/01-Fighters/H.110/H.110.htm or the Sarpoulis version that showed up in the March '77 Flying Models? The original had the engine in the nose with a driveshaft and a junk engine in the back for a prop driver; with electrics you could achieve balance without having to do that.

It's probably the closest thing to a suitable design for stunt that is really out of the box, and it has the advantage that it can be made to be good looking (at least the Sarpoulis version looks nice -- the pictures of the actual plane are a disappointment!)

And you'll have battery cooling covered, hands down.

Come to think of it, there may be an advantage to this -- I haven't flown stunt enough to really know first hand, but my understanding is that the reason that stunt planes tend to really tall, spindly tail gear is because when the plane is going slow the flaps tend to give a pitch-down moment because of the prop blast -- the Hanriot would have no prop blast on the flaps, and just oodles on the elevator, giving you an opportunity for a more realistic landing gear placement and possibly a more realistic takeoff, as you wouldn't have as much of a vertical lift tendency from the flaps+prop blast combination.

Mike Scholtes · « **Reply #12 on:** May 30, 2010, 02:38:16 PM »

The Henriot is the same layout as the classic "Two Bits" design, so we know it works well as a stunter planform. But is there an advantage to locating the thrust behind the wing, either entirely (single pusher) or partly, with one in the conventional location and one in the rear?

Tim Wescott · « **Reply #13 on:** May 30, 2010, 02:44:46 PM »

Well, the difference in takeoff behavior that I quoted is certainly a possible advantage.

And if you just plain like oddball planes, it'd be fun to try. You'd have to do a lot of tweaking and refining: I'd expect to be cutting into the first one a lot, and build it with a show-winning finish.

Wynn Robins · « **Reply #14 on:** May 30, 2010, 04:36:40 PM »

One of the guys over here that I got into electrics has designed and is currently building a scale (ish) twin boom jet using an electric motor mounted in the rear of the pod as a pusher!

He has been wanting to do it for years, but with IC could never get the required balance - but with electrics - this all becomes easy ...

I will post pics when he gets around to showing it to me.....

bfrog · « **Reply #15 on:** May 31, 2010, 05:55:28 PM »

Here's a random, out of the box, idea. Since electric motors tend to be lighter than the glow equivalent, and more importantly, have much less of a vibration problem how about a "vectored" thrust arrangement? Put the electric motor on a pivot and tie the elevator linkage to it. Now up elevator also includes upward thrust with the motor and vice versa. Tight turns? Flat pull out? You could even do a little reverse direction thrust for pull out with the right linkage arrangement. I'm not a stunt flier but the idea is kind of interesting.

Kim Doherty · « **Reply #16 on:** May 31, 2010, 07:34:11 PM »

Quote from: bfrog on May 31, 2010, 05:55:28 PM

Here's a random, out of the box, idea. Since electric motors tend to be lighter than the glow equivalent, and more importantly, have much less of a vibration problem how about a "vectored" thrust arrangement?

Already been done.

http://www.bananahobby.com/1947.html

Kim.

Howard Rush · « **Reply #17 on:** June 01, 2010, 01:37:36 AM »

Yesterday I flew Gordan Delaney's Pathfinder Two, and Phillip Granderson flew Paul Walker's new electric. Those experiences got the Jive Combat Team thinking.

bob branch · « **Reply #18 on:** June 01, 2010, 05:10:30 AM »

bfrog

Yes its been done both with propellor and ducted fan applications for creating extreme maneuvering aircraft. Stability applications need not apply, especially so in the propped versions. Most of those have been flying wing applications since the idea is wild maneuvers.

The ducted fan applications are being done in electric ducted fan and in full turbine powered jets. It allows for 3D manevers including hovers and harriers and other 3D moves. I have an f-16 electric ducted fan with vectored thrust that is one away on the building board. Should be a hoot. More servos than I know what to do with! Ducted fans and turbines tend to be of more scale type jets though I think I have seen one sport wing with vectored thrust. The scale models because of their length and because of the lack of airflow over the wings are more stable but of course require gobs of power for the same reason. Many little milliamps getting blown out the back end.

bob branch

Robert-Jan · « **Reply #19 on:** June 01, 2010, 06:37:37 AM »

At this side of the globe several pilot’s converted there IC plane and some of them had problems with hunting. The cause changed moments??
My first electric plane flew on NIMH cell’s. It was capable of flying the hole schedule. It was special designed for electric with a rather high wing loading. The battery pack is at CG.
Then I changed to Lipo’s. The plane is a combat now . I will cut of the flaps / elevator / round the leading edge to see if I can make it into a stunt plane again.
I think a pusher will be interesting for clean air. There is always turbulence over the plane.
Also this turbulence is a kind of spiral which makes your plane want to turn.
I am very interested in a pusher configuration with the same moment arms.

Greetings Robert-Jan

CircuitFlyer · « **Reply #20 on:** June 06, 2010, 12:07:33 PM »

Going back to the original post: Here's an idea that's outside the box: a twin engine craft with one engine mounted on the outboard wing tip pointing outwards. The other engine mounted normally. The outboard motors RPM is inversely proportional to the forward velocity of the plane. The idea is to always have excellent line tension and control at all times. With throttle control on the normal engine the flight maneuvers possible could be interesting. A control line limited form of 3D? How about hammerheads and tail slides?

What do you think, possible or just to wacky of an idea?

Wynn Robins · « **Reply #21 on:** June 09, 2010, 06:39:46 PM »

Quote from: Silver Dart on June 06, 2010, 12:07:33 PM

Going back to the original post: Here's an idea that's outside the box: a twin engine craft with one engine mounted on the outboard wing tip pointing outwards. The other engine mounted normally. The outboard motors RPM is inversely proportional to the forward velocity of the plane. The idea is to always have excellent line tension and control at all times. With throttle control on the normal engine the flight maneuvers possible could be interesting. A control line limited form of 3D? How about hammerheads and tail slides?

What do you think, possible or just to wacky of an idea?

this has been done before also - with a 1/2a model called the Charger - it had 2x 049s on it one on the nose, the other on the outboard wingtip set out 45 Degrees - i have the plan and article somewhere

Tim Wescott · « **Reply #22 on:** June 17, 2010, 04:35:08 PM »

A semiscale BD5? Dornier Pheil?

Author Topic: Outside the box design thinking (Read 2473 times)

Kim Doherty

Kim Doherty

Kim Doherty