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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 4 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!
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