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Offline Vicente Bortone  
#211 Posted : Saturday, January 12, 2019 2:27:01 PM(UTC)
Vicente Bortone

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Hi rclad,
Very nice information, I also would like to try electric IMAC plane using a 35%. I fly intermediate. I did some check and looks like we could reduce the fuselage weight a lot using just balsa wood in a kit that we could get today. Yes balsa of the same thickness of the liteply. Then cover balsa wood in the inside to make it stronger using lite fiberglass in the tail portion and carbon only in the landing gear and motor box sections. I estimated that we could save about 40% of the actual fuselage weight made with liteply. For example, if the fuselage wood is around 12 lbs we could save using this method about 5-6 lbs. Yes, it will be more expensive since balsa is more expensive plus we need to add the fiberglass and carbon and working time. I did the experiment building 4x4" pieces and covering with fiberglass and carbon. I really would like to do this but I am not that good builder and I don't want to do it alone. I wonder if you could plug the numbers in your program assuming 4, 5 and 6 lbs savings to verify.
Keep trying and I think it will be really good for IMAC.

Offline rclad  
#212 Posted : Saturday, January 12, 2019 5:52:43 PM(UTC)
rclad

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Thanks, Vicente.

The 104V2 fuse weighs 6.47 lbs, and the main wings weigh about 2.08 lbs each. If you took 40% off the fuse weight (-2.59 lbs), and use 4.3" foam, or 4" Kavan Lite wheels rather than stock, that would give you an airframe weight of 12.98 lbs. With the lightest packs possible (4x Dinogy 6S 5Ah packs), AUW = 25.51 lbs, WCL = 8.73, T/W = 1.83:1 and EFT=9.3 min.

Those are good numbers, but building a 35% fuse under 4 lbs would be a challenge! I do think the EF fuse and wings are heavy, but it was designed to take the pounding from a gas engine. Chris Hinson at EF told me he would not feel comfortable making an electric only 35% airframe any lighter than this one.

You can play with the spreadsheet I made below. The performance numbers at the bottom will update with a change in weight.

104 Extra 300 V2 Weights.xls (24kb) downloaded 7 time(s).
Greg Hladky
Flying on a wing and a purpose...
and physics, power, practice, preparation, plans...
and pioneers who pushed the envelope!
Offline Vicente Bortone  
#213 Posted : Sunday, January 13, 2019 11:14:30 AM(UTC)
Vicente Bortone

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Thanks Greg,
I was surprised to see that the fuselage is not that heavy. It will be great that EF could try to built electric only 35%. Probably not enough market and the cost could be too high. I will keep checking the options because I really would like to get an electric 35% that could replace the gas planes I got.

Offline rclad  
#214 Posted : Friday, January 18, 2019 5:42:19 PM(UTC)
rclad

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I'm still trying various setups for the 104" V2, but I think I may be getting close to the ideal configuration for weight, thrust and flight time:

AUW: 28.0 lbs
WCL: 9.6
Static Thrust: 46.9 lbs
Thrust-Weight 1.68:1
Prop: Engel 28x14 CF
GRU 3.158:1
Motor RPM: 16173
Prop RPM: 5121
Battery Capacity: 10,000 mAh (12S2P)
EFT: 9.5 min.

I finally measured the actual static thrust from my 95" Extra. It was only 31 lbs! That's only a 1.5:1 thrust to weight ratio, and I thought that was a decent flyer. The performance numbers on the 104" are now looking even better.

104 Extra 300 V2 Schematic F.jpg (3,287kb) downloaded 8 time(s).

Edited by user Friday, January 18, 2019 6:16:27 PM(UTC)  | Reason: Not specified

Greg Hladky
Flying on a wing and a purpose...
and physics, power, practice, preparation, plans...
and pioneers who pushed the envelope!
thanks 1 user thanked rclad for this useful post.
Ray Morton on 1/20/2019(UTC)
Offline Greg Marsden  
#215 Posted : Saturday, January 19, 2019 4:48:31 PM(UTC)
Greg Marsden

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Even though I haven't been flying much IMAC, some of you might find this thread interesting about an electric 40% Extra I built. a few years ago.
It has way more than enough power and duration to fly two Unlimited sequences.
14S 18000 mAhr, 29x13.5Q, Plettenberg 37 Evo, MGM 400A ESC.
38 lbs RTF.
https://www.rccanada.ca/.../showthread.php?t=295217

Cheers - Greg Marsden
thanks 3 users thanked Greg Marsden for this useful post.
Dave Dupre on 1/19/2019(UTC), rclad on 1/19/2019(UTC), Suds on 1/20/2019(UTC)
Offline rclad  
#216 Posted : Saturday, January 19, 2019 8:09:37 PM(UTC)
rclad

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Thanks for the link to your build thread. Your efforts paid off nicely. That's an incredibly light airframe. You achieved all the goals one would want in an electric aerobatic plane, and at 40%!

I was initially planning on using a 14S setup, but couldn't find 7s packs that are light enough. I don't see the 7s 9000 Revolectrix packs on their website. Were those a custom order?

How did charging that many packs work out?
Greg Hladky
Flying on a wing and a purpose...
and physics, power, practice, preparation, plans...
and pioneers who pushed the envelope!
Offline Suds  
#217 Posted : Sunday, January 20, 2019 9:24:43 AM(UTC)
Suds

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The finished electric GRU (gear reduction unit) is shipping to me and I should have installed onto a 105" AJ Laser shortly. Unfortunately the weather doesn't look good the next few weeks, but I'll get it airborne at the first opportunity possible.
Going to test a variety of 12S setups: 2S 8000mah, 2S 10,000mah, 2S2P 11,600, and 2S2P 12,400. I'd guess the 8,000 or 10,000 be great for 3D flying but will need the ~12,000mah for IMAC.
GRU complete.jpg (1,630kb) downloaded 5 time(s).
thanks 1 user thanked Suds for this useful post.
rclad on 1/20/2019(UTC)
Offline Steve Stanton  
#218 Posted : Sunday, January 20, 2019 11:12:23 AM(UTC)
Steve Stanton

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Hi Suds, what is the cost for a rig like that?
Offline Suds  
#219 Posted : Sunday, January 20, 2019 11:20:39 AM(UTC)
Suds

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Originally Posted by: Steve Stanton Go to Quoted Post
Hi Suds, what is the cost for a rig like that?

Well there are only 4 currently being made. The creator (Aeroplayin on rcgroups) said that he'd need between $700 to $800 for the motor-GRU combination to make it fiscally feasible in order to produce more. Then add in the cost of a 200A ESC and battery packs. I believe Rclad, leelander (from rcgroups), Aeroplayin and I will be the 4 individuals testing the units to ensure they hold up as anticipated. The unit was designed as an upgrade on the Flitework GRU units from Austria.
Rclad will be a great representative for IMAC performance and I'll be trying a little IMAC but primarily trying to push the limits of the GRU in 3D fashion to ensure its durability.
thanks 1 user thanked Suds for this useful post.
rclad on 1/20/2019(UTC)
Offline Dangerous Dan  
#220 Posted : Sunday, January 20, 2019 11:25:16 AM(UTC)
Dangerous Dan

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Here is a pic of my GRU 66790479-1816-4799-A072-E371C30AE16B.jpeg (452kb) downloaded 2 time(s).
2017 SC Sportsman Regional Champion
2018 SC Intermediate Regional Champion
2018 Worlds Team Qualifier
Texas ARD
The answer to all questions lies in the bottom of your fuel can, and in your plane setup
Offline Steve Stanton  
#221 Posted : Sunday, January 20, 2019 11:36:16 AM(UTC)
Steve Stanton

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Hey Dan, your pilot looks scary. Is that a H9 Sukhoi?
Offline Dangerous Dan  
#222 Posted : Sunday, January 20, 2019 11:43:17 AM(UTC)
Dangerous Dan

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Originally Posted by: Steve Stanton Go to Quoted Post
Hey Dan, your pilot looks scary. Is that a H9 Sukhoi?


Yes

2017 SC Sportsman Regional Champion
2018 SC Intermediate Regional Champion
2018 Worlds Team Qualifier
Texas ARD
The answer to all questions lies in the bottom of your fuel can, and in your plane setup
Offline Earle Andrews  
#223 Posted : Sunday, January 20, 2019 1:11:32 PM(UTC)
Earle Andrews

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Gru is awesome.....and in my opinion meets the scale pilot rule. I have a friend who looks like Gru's brother, with just a tad shorter nose!
Offline Greg Marsden  
#224 Posted : Sunday, January 20, 2019 4:13:39 PM(UTC)
Greg Marsden

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The Revolectrix 7S 9000 mAhr were a custom order and I think the cells are no longer available. If they have the cell size you want, they can make up 7S packs even though they are not on the website.
I used a Dual Power Lab charger that can do 1300W. It worked fine in the house but my Honda 2000 generator could not do 1300W since the variable current requirement of the chargers would cause surging of the generator. I went to 48V power supplies so that the charger did not change from buck to boost mode as the battery voltages went through the supply voltage. Originally I had 28V supplies, the 48V supplies worked better but I could never get much over 1000W when on the generator.

- Greg
thanks 1 user thanked Greg Marsden for this useful post.
rclad on 1/28/2019(UTC)
Offline Suds  
#225 Posted : Monday, January 28, 2019 11:23:48 AM(UTC)
Suds

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IMG_2442.JPG (2,728kb) downloaded 1 time(s).GRU update #1.
Plugged gas motor holes with dowels and fitted the GRU to the firewall and cowl. The pinion didn't clear the bottom of the cowl so I enlarged the current hole to fit around the pinion. Good news is that the motor will have plenty of direct cooling air over it. I also started the ESC wiring but didn't have enough time to finish up yesterday. Will definitely get it all put together the remainder of this week. Looks pretty cool in person, and the main gear is pretty big.
gru4.JPG (59kb) downloaded 0 time(s). gru1.JPG (68kb) downloaded 0 time(s). gru2.JPG (76kb) downloaded 0 time(s). gru3.JPG (61kb) downloaded 0 time(s).

Edited by user Monday, January 28, 2019 2:55:10 PM(UTC)  | Reason: scale pics to fit

thanks 1 user thanked Suds for this useful post.
rclad on 1/28/2019(UTC)
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