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Author Topic: Stagger Bee  (Read 623 times)
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danmellor
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« on: October 02, 2016, 03:57:27 PM »

As I'm a bit of a Bee fan, the next one will be a Stagger Bee. I built one a while ago, but was forced to sell it after marriage split before I'd even flown it. Can someone recommend a brushless outrunner power train to replicate a .20 glow motor?

Cheers,

Dan.
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Konrad
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« Reply #1 on: October 02, 2016, 07:17:28 PM »

Dan,
I'm sorry to say there are no electric motors that replicate a 0.20 CID 2 cycle glow engine.

This is because the slope of the power curves are opposite. True at one point they may mimic each other. An electric motor is best thought of as an electric motor.

Per Stagger Bee's manual he recommends  a 10 to 25 amp motor. Based on the typical power system back then that would have been on 8.4V. So you are looking at a 200 to 250 watt power system.   Today that would be a 3 cell 2100 mAh battery. I think the marketing guys call these 450 to 480 power system. You might have good luck with a Park 450 on a 10 x 7 APC prop or a park 480 on a 12x 5 APC prop. Please note that both of these power system drive a lot larger prop than what is typical of a 0.20 glow CID engine. They are also on the large side of what a .30 glow four cycle engine would turn.

Let us know what are the limitations of your charger and ESC.
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« Reply #2 on: October 04, 2016, 11:31:52 AM »

To answer the OP's question a bit more objectively...

I converted my 44year old 'Chigger' bipe that was flown with a Webra Speed 3.5cc (~.20cid) to electric using a KD 36-16M 1025Kv motor on 3S (Hobby King).  This motor is close to the same as the Hacker A30-16M in stats (don't ask about quality Roll Eyes).  I also used a switching (linear, NOT) Robbe 940-6 ESC 40 Amp) - I like to go a bit oversize with the ESC.  The motor has a peak current of 29 Amps and operating current of 22A with a 13 x 4E or 12 x 6E prop.  The plane flew quite a bit better, mostly due to the larger prop, but was still somewhat sluggish.

The plane weighed about 3lb 4oz without fuel (IIRC 4oz) and was about the same in the initial electric (con)version.  Both required lead in the snout.  Weight reduction in progress - a good thing to do in any wet-to-dry conversion): stripping all paint, using a light weight film covering, knocking out lightening cut-outs aft of the wing (fuselage sides are 1/8 medium balsa, prob 10# stock), and substituting a built-up fin for the stock 1/4" solid piece.  Weight reduction so far, about 4.8 ounces!

As Konrad stated 250 watts should be fine along with the stated akku, but I have reservations about the 450 sized motor.  E-Flite's Power 15 (or equivalent) might be a good alternative.
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Konrad
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« Reply #3 on: October 04, 2016, 12:53:11 PM »

We are talking about the Clancy Stagger B, this is a 29 inch 445 square inch model built  primarily for electric flight? It was intended to use an Astro Flight geared Cobalt 035 or geared Cobalt 05 motor on  7 cell (nicads 1.2v/cell).

The manual states the engine size as 0.061 to 0.30 4 cycle. So per the manual she will “fly" on a G-Mark 0.061 cid 2 cycle to Saito .30 cid 4 cycle. Clancy did like to fly on the wing and not the prop. I saw one of these fly on a Astro 020, that is the brushed 020 not the brushless 020

I’m flying an E-flite RV-9 (50 inch span and 385 square inches at about 37 oz) on a Park 450 890 kv motor. It makes all my 3.5cc sport (baffled) engined powered models in the same size range look sick.

I assumed that Dan was not looking for the performance he might expect from a fire breathing piped, schnuerle ported,  race prep’d, ABC. 3.5cc race engine. But the 480 will give one that kind of performance with the reliability of electric and the pull of a large prop.

The "450" in more in line with the long canned Hacker A20-xx-L or XL.

All the best,
Konrad
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danmellor
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« Reply #4 on: October 05, 2016, 01:41:09 AM »

Thanks for all that! Useful stuff to an electric ignoramus like myself...

Plenty to think about!

Dan.
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danmellor
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« Reply #5 on: October 21, 2016, 05:20:09 PM »

I have all the electrics for the Lazy Bee currently on the board, but I need to buy from scratch for the Stagger Bee. So far, the Park 450 looks favourite.

Thanks!

Dan.
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Konrad
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« Reply #6 on: October 21, 2016, 06:52:48 PM »

In electric models the prop more than anything else will determine the power performance of the plane. I like to select the prop pitch so that I have a pitch speed of 2.5 or more x the stall speed. Then I adjust the prop diameter for a power loading of 75 to 100 watts per pound.

Stall speed can be difficult to come by without a wind tunnel. So I use this is an approximation by Keith Shaw. You might remember the Model Aviation Back Page write up in last month’s issue. Keith is generally credited with bringing electric flight to the USA masses with his scale flying demonstration during the 80’s, yes the days of round cells.

Stall speed = 3.7  times the square root of the wing loading
Units are speed in mph, wing loading in oz/sqft

For a bipe I’d use 80% of the wing area to adjust for bipe plane inefficiencies.

My 450 sized models use 3 cell batteries that range in size from 980 mAh to 1320 mAh

All the best,
Konrad
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