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Old Jul 22, 2015, 03:22 AM
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Help!
what size motor and battery

Hi. I'm building a f86D sabre. It has a wing span of 46". The wing area 450 in /L.O.A 45" . The weight should be coming in about 5 lb 5oz and the wing loading is 26oz/sq. ft.
I am putting a 70mm 12 blade fan unit in and I'm unsure what sort of motor and battery I should go for. If anyone has any information or can point me in the right direction would be much appreciated. Thanks
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Old Jul 23, 2015, 02:50 AM
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You should have a bigger fan. 80-90mm.
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Old Jul 23, 2015, 04:10 AM
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İf inlet and nozle is suitible you can choose 90 mm EDF and 4000-5000 mah lipo. There are a lot of obtions for this size.
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Old Jul 23, 2015, 01:21 PM
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Only problem is I'm struggling with fitting a larger fan unit in. I might be able to fit a 80mm in. Would a 70mm not be up to the job then
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Old Jul 23, 2015, 10:46 PM
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What is the circumference of the space you are putting it in? use a flexible measuring tape used for fabric and sewing applications to get and accurate reading...Usually that will give you a good idea of what you can use to fit your needs. Usually the designers of these aircraft have a certain size in mind when they design them. I agree with St.Martin usually EDF aircraft that are around the 5lb. mark have 80mm fans or larger.
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Old Jul 24, 2015, 03:32 AM
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You "can" fly a 5.5# jet with a 70mm fan. But it will require a lot of watts. That requires a lot of battery(more weight). And it best be a slick fast design to take advantage of the high efflux that will be required. And I don't think the 12b fan will be an advantage, but a hindrance.

One of my alltime fav jets, was the RBC Panther. Instead of using the 90mm WeMo, I used the minifan Pro. Running 1400W and a weight of only 4# vs 7# of the 90mm version, it flew great. It was not slick, but was light and low wing loading. And I used an outlet of 58mm for higher static thrust. Actually, your question of 70mm use with your airframe is very broad base. Lot's of other things to consider.

Fuzz
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Old Jul 24, 2015, 02:58 PM
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Originally the plane was designed for a ic 40/46 size engine. The body is very sleek and narrow. That's why I put in a 70mm fan. If I was to try and go ahead with the 70 what sort of setup would i be needing? Thanks
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Old Jul 24, 2015, 10:21 PM
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Daniel, your still being too broad in your description, for expecting much input. Was this a 40-46 prop jet? Ducted fan? Having a very narrow fuselage, indicates to me, it may be I.C prop, engine in the front? If this is so, the design type does not lend itself well to EDF conversion. The construction is too heavy(slab sides, ply doublers, etc). Put an electric motor in the nose, and use it as it was intended, and have fun. It's most likely to have all the wrong areas for EDF use.

Fuzz
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Old Jul 28, 2015, 03:22 AM
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Sorry yes it was prop. It was to be mounted on the front. I have some pics of what I've done so far
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Old Jul 28, 2015, 10:13 AM
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Take any 6s 90mm motor stick it on the 12b70mm fan and run it on 8s, should get you off the ground!
Me or Lee can help you figure it out!
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Old Jul 28, 2015, 10:31 AM
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Well since he's got the 70mm edf already and he's really only asking about motor and battery for that specific unit, how about a cs480 2300kv outrunner motor with a 6s battery combination? He'd also have to check the ESC that seems to be already part of the project to see if it can handle the motor/battery combination. I'd guestimate the ESC would have to be a good 100amp deal because from my understanding, the cs480 2300 outrunner will draw a good 80 amps. And it's always good practice to go about 20amps over in regards to what the ESC can handle, for a safe zone.
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Old Jul 28, 2015, 01:46 PM
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Thank you very much. The speed control is 100amp so should be good on that. Will have to get myself that motor then and see how I can get on. What size battery u recon to give me a decent flight time?
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Old Jul 28, 2015, 04:42 PM
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Quote:
Originally Posted by Daniel tandy View Post
Thank you very much. The speed control is 100amp so should be good on that. Will have to get myself that motor then and see how I can get on. What size battery u recon to give me a decent flight time?
Just be sure it's all good by the numbers and all. I'd also wait for the EDF guru's to chime in. I suggested that motor/battery combo only cause I saw a local guy using it in his EDF jet, Seemed to work out really good for him, so....and posting it up because I know others will reply in favor or against it, which is good information either way.

In regards to run time. Depends on how much throttle you're flying with and how healthy the batteries are that you're flying with. But basic rule of thumb that I've experienced with the EDF units is for every 1000 mah, roughly 1 minute of run time. For example, in a 70mm EDF jet that I putt around with, I get a good 4 to 4.5 minutes worth of full throttle flying with a healthy fully charged 5000 mah battery. Now same battery, same plane but at a fraction of the throttle, I can squeeze out about 6 to 6.5 minutes per battery and still have it at around 3.80 per cell. Flying on old worn out batteries though, as I've done before, there is no way of telling how much run time you can get out of them regardless on what the label on the battery says.
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