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jfcgnv
10-03-2005, 12:29 AM
What would be a good motor , battery combination for this project. I want to use four motors and li-pos. Also what should I be thinking of for an all up weight..

John C

How does this sound? Four Speed 280's pulling Graupner three bladed 4/2 props. On the bench this motor prop combination draws 3.5 Amps with a 7.4 2S TP 21oo Li-PO. I should have a total amp draw of 16 or less and a total watts of about 100 as each motor at WOT gives about 25 watts of power. I figure that if I can keep the total weight to around or under 35 oz. I should have a workable solution. All four motors and the TP 2100 come to 14 oz. I will have to keep the airframe to 15 to 20 oz. Is this possible? I still have time to make changes as I am in the frame up stage now. Any help will be greatly appreciated.

John C
Taking off is optional landing is not.

watt_the?!
10-05-2005, 12:13 AM
What would be a good motor , battery combination for this project. I want to use four motors and li-pos. Also what should I be thinking of for an all up weight..

John C

How does this sound? Four Speed 280's pulling Graupner three bladed 4/2 props. On the bench this motor prop combination draws 3.5 Amps with a 7.4 2S TP 21oo Li-PO. I should have a total amp draw of 16 or less and a total watts of about 100 as each motor at WOT gives about 25 watts of power. I figure that if I can keep the total weight to around or under 35 oz. I should have a workable solution. All four motors and the TP 2100 come to 14 oz. I will have to keep the airframe to 15 to 20 oz. Is this possible? I still have time to make changes as I am in the frame up stage now. Any help will be greatly appreciated.

John C
Taking off is optional landing is not.


Hi John, sorry that you havent had a reply yet.

Try and work backwards from your predicted AUW. Then figure your thrust requirements, then spec your motor/prop combo, then you can arrive at your battery and ESC.

Anywhoo, if not, can you measure rpm? thatll help predict what you are getting in terms of thrust. for a 35oz plane, you should be looking at around 20oz thrust, minimum 15oz..it all depends on what surface you take off from etc.

Tim.

easytiger
10-09-2005, 09:02 PM
It may not be as easy as you think to keep the airframe that light. The plastic parts and the sterling woods weigh quite a lot.
Consider this...
A freind of mine has the same rig, but only the two inboard motors are powered, teh outer props are dummies. With the motors you are talking about.
Power is not an issue.
Light weight is the way to go with a small stick and tissue plane like this, otherwise you will be battering the plane to death on every landing.

jfcgnv
11-04-2005, 06:28 PM
First flight today. It went better than expected. Final set up was Four speed 280's with a 20 amp wsc with Kokan 2000 7.4 volt lipo. All up weight is 22 OZ with Battery. I finished the model with Tissue and Aero Gloss Olive Drab. Tried to post a picture however I could not shrink it enough to take on the post. What I thought was a good landing ended up knocking one of the gear loose. It has been repaired and both sides beefed up more. Will fly again tomorrow. sorry about the picture not taking it is really a cute little B-17.

watt_the?!
11-04-2005, 06:31 PM
hi John,

please send me the pics and ill size them and post.....very keen to see the plane.

tim

easytiger
11-04-2005, 06:33 PM
Sounds pretty light, but I think you need to be really careful about how and where you land it, it's going to get beat up...

jfcgnv
11-06-2005, 04:15 PM
Photos sent to WATT-the. Tim feel free to post them if you can get the forum to accept them. Cute little flyer.

John C jfcgnv

watt_the?!
11-06-2005, 09:30 PM
Sorry, busy weekend...

watt_the?!
11-06-2005, 09:32 PM
more.

eflight-ray
11-08-2005, 02:10 PM
One day. (I keep telling myself), my B17 will fly. There's just something about it's shape that's magic. As a Brit I surpose I should be building a Lancaster.
Mines just a tad bigger.

Highlander
12-16-2005, 06:09 AM
Heck, I'm a Yank and I built a Whitley! :)

salat
09-08-2007, 05:53 PM
Hello!
Tell me please does Sterling have ailerons by design or not? What is better Guillow's or Strling?
Kostya

tom1968
10-05-2007, 12:29 AM
John that looks really good. I want to build one about that size some day to fly at the local high school field. Sounds like the power system worked out well too.

Bill G
10-05-2007, 02:58 AM
Hello!
Tell me please does Sterling have ailerons by design or not? What is better Guillow's or Strling?
Kostya
I look at them as the same, since they require extensive re-engineering to convert. They use similar design schemes too.