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Author Topic: How to redesign an IC model for electric  (Read 2086 times)

Offline Eric Jensen

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How to redesign an IC model for electric
« on: January 04, 2022, 06:29:44 PM »
I an returning to stunt after a two decade siesta. I am not surprised that electric flight is a thing now and I’d like to explore it. The problem is I have no idea where to start. I have read up a bunch on how the power systems work, so fine. But how to design a model for it?
Ideally I would like to build a new model from scratch for my first try at it. Are there any write ups on the design changes needed to the nose of a stunt ship? Hoping there is some literature or even posts on this board that can help educate me.
I’ll probably want to build a 550 sq in sized ship. Thanks.

Offline Dan McEntee

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Re: How to redesign an IC model for electric
« Reply #1 on: January 04, 2022, 07:19:01 PM »
  Well, just going from what I have been reading what others do, you start at the nose with a motor mount, behind that a firewall of some kind to attach the mount to. Then sufficient area for the timer, speed control, switches and such, then area for the battery. The nose moment can be "typical" or what you are familiar with as long as you can get the battery you need in there. The nose structure can be lighter because you don't have engine vibration pounding it.  Everything behind that is just what you are familiar with as far as wings, fuselage tail and tail moments. With no fuel involved you can paint it with what ever works for you. Maybe you should consider a purpose built kit to get you started, then rob what you like from that for your own design.
  Type at you later,
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Offline Tim Wescott

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Re: How to redesign an IC model for electric
« Reply #2 on: January 04, 2022, 07:33:09 PM »
Disclaimer: I have just set my feet on this path, but I've been looking at a lot of people's planes.  There's a lot about this in old threads here -- learn to use the search function, and spend some time browsing in the "Gettin' Amp'd Up" forum.

This is what's got my brain spinning in circles the most right now (and this is all assuming a full fuselage -- profiles are easier, mostly).  Spend a lot of time reading, ask questions where you need to.  There's a lot of travelers on this road right now.

  • It's a bit of a shoe-horn to fit an electric setup into a slimer -- all the stuff just takes up volume.  A wider fuselage is a big help (1/4 to 1/2" in your case), and any extra weight is offset by the fact that you don't need as much structure to absorb vibration.  The top-notch guys are building fuselages that are 3" or more wide (for a 700 square foot plane).
     This gives lots of room inside for stuff.
  • Make sure there's lots of air over the motor.  My third or fourth electric stunt flight featured the motor cutting out (dramatically enough, right at the top of a loop, instead of the bottom and upside down).  It had overheated and died in flight.  This was a combination of insufficient airflow and wires rubbing on the motor.  I now have a nice old vintage stunter with two ugly aluminum air scoops on the nose (see picture) -- and the motor only stays tolerably cool
  • Those maple motor mounts make nice battery mounts, but you can carve a lot off of them.  I can't find a picture, so I've included a crappy sketch.  The idea is that you route a bunch off the inside of the rail, put screw holes in the "bumps", and then 3D print mounting brackets.  (Or bend them out of aluminum, which is what I'll probably be doing).  The other part of the idea is that by making different brackets, you can hold the battery at a different height in the fuselage (if you have room) and trim the vertical CG.
  • Overall, the two approaches that seem to work best are to make what looks like a regular old slimer, only with a fuselage that's significantly wider, or to make a big round molded fuselage (this is what the top guys are doing).
  • Either way, you can go lighter -- like 3/32" fuselage sides instead of 1/8", thinner plywood in the nose, or same thickness with giant lightening holes.  Pay attention to where you used to put extra wood because of vibration, and where you used to put it for flight loads -- you still need to deal with the flight loads, but your power system vibrates a lot less.  If you've designed for RC it's the same deal -- electric power means less airframe is needed.

Don't hesitate to ask questions!  Most of us are feeling our way here.

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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Ken Culbertson

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Re: How to redesign an IC model for electric
« Reply #3 on: January 04, 2022, 07:47:47 PM »
I an returning to stunt after a two decade siesta. I am not surprised that electric flight is a thing now and I’d like to explore it. The problem is I have no idea where to start. I have read up a bunch on how the power systems work, so fine. But how to design a model for it?
Ideally I would like to build a new model from scratch for my first try at it. Are there any write ups on the design changes needed to the nose of a stunt ship? Hoping there is some literature or even posts on this board that can help educate me.
I’ll probably want to build a 550 sq in sized ship. Thanks.
I may be a good one to start this off since I just returned in 2017 after a 30 year trip in the wilderness.  On my first trip to the circles I was lucky enough to find two of the local experts practicing.  We chatted for a few minutes then I was treated to a show I did not expect.  First, a piped 75.  Holly .... not your grandfather's Fox 35 but that was just the warmup.  Next up was Mike Scott with an electric and my reaction on landing was, to quote Will Smith, "I gotta get me one of these".

Enough memory lane.  I build my own from scratch too so here is what is truly different.  The rest you can gather from the many threads on this exact subject well hidden in the archive search.  First, No Oil!  That means you can build and finish with anything you want.  Second, no vibration.  This has a + and a - attached.  The plus is that you don't build the nose like Ft. Knox anymore. The minus is that without vibration, the controls need to be really free to keep them from sticking = hunting.  Third, everything gets hot.  With IC all you had to worry about was cylinder on the air and venting after the flight.  With electric you need massive airflow over at least 4 components.  Then there is changing the battery.  You need some kind of hatch where you can pull out one battery and put in another.  The rest of the airframe is about the same.

If you build your own it would probably be wise to design your own as well.  Most of the planes out there today were designed for IC and converted to electric even if they were build from scratch to be electric.  So here is my 2 cents on design.  Make the nose fatter.  The one I have on the workbench is 2 1/4 wide at the nose.  Design the nose around your mount.  There are three basic types, the nose ring front, the forward firewall mount and the rear firewall mount.  The motor vents through the motor, not around it so you need a larger spinner gap.  Those fancy spinners with holes in them don't do much. 

The battery is heavy.  Make sure you mount it, not just stick it in a hole and close the hatch.  It weighs about 10 lbs in a corner and you don't want 10 lbs flying around inside your nose. You are going to feel like the plane is really going to be nose heavy.  Well here is the good news, the CG on an electric will end up well forward of where it would be using IC on the same plane.  I have asked folks far smarter than me why and the answer is always "it just is".  And really, it is.

I admire your wanting to jump right in and build a full-body electric PA but keep one thing in mind.  You have a whole new technology to learn and a whole new way of building.  Electric is a whole new game and it wouldn't hurt to build something simple like a Twister or Pathfinder to learn how to use the power train with everything exposed.

Ken

As usual I type slower than Tim and Dan.  They know their stuff!   By the way, those 700 square foot planes have larger motors.  LL~

Picture is from my Endgame design.  This is a rear through the firewall mount.  Motor mounts to the back of the firewall with blind nuts on the front.  Got the idea from Bob Hunt.
« Last Edit: January 04, 2022, 08:09:22 PM by Ken Culbertson »
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Online Dennis Nunes

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Re: How to redesign an IC model for electric
« Reply #4 on: January 04, 2022, 08:12:58 PM »
Hi Eric,

You might find it interesting to read an article that I wrote about my experience of designing, building and flying my first electric power precision aerobatic plane. Though this is a profile, this has been an excellent plane. The article can be downloaded on the Flying Lines website at: http://flyinglines.org/nunes.circulas46lle.html

Enjoy,
Dennis

Offline Eric Jensen

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Re: How to redesign an IC model for electric
« Reply #5 on: January 05, 2022, 09:25:09 AM »
Thanks everyone. I'll take the point of starting out with a profile model as good advice. Dennis, that's a great piece you wrote. Lot's of good stuff in there.

Offline jose modesto

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Re: How to redesign an IC model for electric
« Reply #6 on: January 05, 2022, 12:11:24 PM »
So great to have you back
Jose modesto
You can slo reach out to Bob Hunt

Online Dennis Nunes

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Re: How to redesign an IC model for electric
« Reply #7 on: January 05, 2022, 12:14:16 PM »
Thanks everyone. I'll take the point of starting out with a profile model as good advice. Dennis, that's a great piece you wrote. Lot's of good stuff in there.
Thanks Eric, I hope it was helpful.

Dennis

Offline Tim Wescott

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Re: How to redesign an IC model for electric
« Reply #8 on: January 05, 2022, 12:21:47 PM »
Just a note: I wasn't entirely happy with the results of my search, so I started this thread asking folks to show off their battery mounting schemes.

We'll see if anything comes of it.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Brent Williams

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Re: How to redesign an IC model for electric
« Reply #9 on: January 05, 2022, 02:44:39 PM »
I will add that Crist Rigotti always makes great building tutorial threads for his planes.  Add his work to your reading list as well.

Really, there are so many great posts on this topic from masterful builders.  As you search and read, you will start to see some of the design and construction methods that work for electric fuselage construction.

https://stunthanger.com/smf/gettin-all-amp'ed-up!/legacy-40-electric-a-build-log/
https://stunthanger.com/smf/gettin-all-amp'ed-up!/2016-electric-stunter-build-log/

https://stunthanger.com/smf/gettin-all-amp'ed-up!/2012-stunter-thundervolt-a-build-log/
https://stunthanger.com/smf/gettin-all-amp'ed-up!/2013-electric-stunter-a-build-log/
https://stunthanger.com/smf/open-forum/pathfinder-arc-electric-conversion-build-log/
« Last Edit: January 06, 2022, 02:50:13 AM by Brent Williams »
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
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Offline Eric Jensen

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Re: How to redesign an IC model for electric
« Reply #10 on: January 06, 2022, 04:29:46 AM »
Thanks Brent! I just perused him building a lost foam wing. Impressive!

Jose, I hope to see you in Flushing this year.

Online Brent Williams

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Re: How to redesign an IC model for electric
« Reply #11 on: January 06, 2022, 09:15:18 AM »
Bob Hunt's "hard nose" method works great for profiles and built up.
https://stunthanger.com/smf/gettin-all-amp'ed-up!/nose-construction-for-rd-1e/

Bob Hunt also has several extremely detailed construction manuals that he will provide free of charge as a PDF if you send him an email.  Bob's manuals are a master class in modern, clever construction methods.

Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Offline jose modesto

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Re: How to redesign an IC model for electric
« Reply #12 on: January 06, 2022, 09:57:03 AM »
Eric can’t wait  the flushing contest is a great event
I have been flying Electric going on 12 years
You will love the power delivery. With and active timer the range of adjustments are limitless. You can dile up
A perfect 2/4 run. And repeatable on every flight
Igor or Fioretty systems are the standard today.
Lipo Batt have been the standard. But today we have option on Batt
Eric no more plywood I the nose
If you are on FB. Look at Joe Daly’s  build photo album. He is also a flushing flyer
Jose modesto

Offline Brian Courtice

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Re: How to redesign an IC model for electric
« Reply #13 on: January 16, 2022, 06:34:36 AM »
Hi Eric,

You might find it interesting to read an article that I wrote about my experience of designing, building and flying my first electric power precision aerobatic plane. Though this is a profile, this has been an excellent plane. The article can be downloaded on the Flying Lines website at: http://flyinglines.org/nunes.circulas46lle.html

Enjoy,
Dennis
Wow. What an amazingly informative and comprehensive article! You put a lot of effort into documenting your build. Much appreciated.


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