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Jul 23, 2015, 05:09 PM
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Question

CG "Zipper" power question


OK fellows, a little advise; preferably from someone that's done it. Have a CG Zipper I built several years ago(54" ws) and never put in the air. Mostly I run large gas but I did find a EFlight 480 1020KVA motor with a 40A speed controller & have installed same in the ZIPPER. Have several 2200mah Lipo packs @ 20C I will use 1 @ a time of course! Have a 9x5 APC prop on it. Weight comes in at 1# 14oz. which is 2 oz. over the drawing design weight. Using Rudder & Elevator on FM. Know it's a little late to ask, but what have others been using for electric power.
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Jul 23, 2015, 08:53 PM
Culper Junior
I have a Zipper which I've been flying for about 4 years now with a brushed Magnetic Mayhem, direct drive. I'd have to go out to the garage to check what size wood prop is on it. Doesn't go vertical, but flies nice enough for me. Almost forgot...batteries...6 cell 1200mah nicads. I'm also using a Futaba Attack rx which has the speed control built into the rx. IIRC its 30 amp.
Jul 23, 2015, 11:51 PM
I like real wooden aeroplanes!
Sundancer's Avatar
Need to know the power in watts (or current in amps and battery voltage - are your 2200 2S or 3S - to be able to calculate same). A 14 ounce vintage design will actually fly as a R/C model on amazingly little power, probably no more than 40 watts, maybe even less, but if you want to replicate the F/F climb performance of a pylon power model then around 120 watts would do the trick at this weight, in which event it would stay airborne on about 1/3rd throttle.
Jul 24, 2015, 06:51 AM
Registered User
Thread OP
3 cell batteries; I have 3 of them an it's what I'm using because it's what I have and it's what balances on the CG!
Jul 24, 2015, 07:06 AM
Blueplaidcanard flyer
Put a 10x7 apc on it and go.
Jul 24, 2015, 07:06 AM
I like real wooden aeroplanes!
Sundancer's Avatar
Lacking any info on the current draw on the 9 x 5 prop/3 cell combo I looked up the motor specs (http://www.e-fliterc.com/ProdInfo/Fi...structions.pdf) and see they recommend 10 x 7 to 12 x 6 props and maximum continuous current of 22 amps. So lets assume that with the 9 x 5 it will run at around 15 amps, giving about 160 watts. 160 watts in a 14 ounce vintage model = rocket ship and a very wild ride indeed! Notice that they say this level of power will give unlimited 3D performance in a model weighing 1.6 pounds - roughly twice as much as the Zipper weighs! Of course the Zipper is a long way from being a 3D model and I would suggest that at full throttle there would be a very good chance of pulling it's wings off even if you manage to control it.

Good luck!
Jul 24, 2015, 07:11 AM
I like real wooden aeroplanes!
Sundancer's Avatar
Quote:
Originally Posted by rabidrue1
Put a 10x7 apc on it and go.
GO it certainly would Scottie - straight up and OOS in about 30 secs I would say - if it stays in one piece!

Edit: Ah, looking again I see it may be 1 lb 14 oz. Better, but it'll still be pretty lively!
Last edited by Sundancer; Jul 24, 2015 at 07:16 AM.
Jul 24, 2015, 08:00 AM
Blueplaidcanard flyer
I use the same combo in my miss2 and lively it is but still easy to manage.An 11X4.7 apc will calm it down some,this is the prop I use for training duty on the buddy box.
Jul 25, 2015, 02:44 AM
B for Bruce
BMatthews's Avatar
That motor is no slouch. I've got one and it's plenty peppy for this weight of model.

For the best climb we generally want to run a lower pitch. Rabidrue's suggestion for a 10x7 would be OK according to the instructions for a sport model where you want some speed. But for pure climbing I'm thinking that a 10x5 or 11x5 might work out better by matching the airspeed more closely in the climb.

At least I'm assuming that you'll use it like a free flight where you climb smartly then shut off and glide around. But even if you want to power up and cruise around the 5 inch pitch will work with a slower flying model like this will be.
Jul 25, 2015, 09:54 AM
I'd rather be flying.....
JeffMac's Avatar
Hi Cardfan-

I fly an Earl Stahl Fokker D8 1941 antique model using a park 480 960KV? motor on two lipo cells. A 12-6 APC prop is used for the 31 ounce model , 57 inch span. It's a great flyer and has adequate power for the slow flying I like it to do.
On three lipo cells it would have a super charger compared to two
Be sure to use a wattmeter to confirm and change props if needed to not over work the power system and the Zipper will be flying .... Two or three lipo cells just depends on your flying style and equipment on hand as you said also and using the throttle...

have fun,

jeff
Jul 25, 2015, 02:07 PM
Registered User
Thread OP
really do appreciate all the comments; seems I have all the motor I need and then some! As mentioned my general flying is with large gasser's so this is a bit different for me. Really just looking for some lazy flying and as a youngster in the 50's(that's 1950's) I remember seeing one in a hobby shop and it looked just "huge". So the comments beg the question-
Why not just use the 480/1020KVA motor, the 3 cell battery, & 9x5 prop and use caution with the throttle?? I understand with the Zipper I will need to that anyway with little use of rudder or elevator while under power. Will it do harm anywhere??
Jul 25, 2015, 03:15 PM
I like real wooden aeroplanes!
Sundancer's Avatar
A 9 x 5 should keep the watts down somewhat, and after all, you have the throttle! I think you will be surprised at how little throttle you will need to actually maintain flight. Have a good time!
Jul 28, 2015, 05:51 PM
Registered User
Thread OP
The ZIPPER left the ground in a hurry at half throttle but did a hard turn RIGHT before gaining 5-6' in height. Not real sure what happened but the prop broke so I'll have to send off for a replacement & I'll go with a 11-12 " with a 5-6 pitch. Will add some side thrust & check all alignments then try again. No local hobby shop.
Jul 28, 2015, 06:24 PM
B for Bruce
BMatthews's Avatar
I would stick with the 9x5 size. Electrics don't work the same as glow and gas engines. Putting MORE prop on the 480 is going to force it to draw MORE power, not less. It'll do this with rising prop size until it draws enough power to burn itself out and never ask "why" at all. The fact that it lifted off at half throttle and had that much power suggests that it's fine with that size prop. Once you get it dialed you'll be able to use the power to climb in a near vertical fashion just like a Zipper should. Rocket up, cut power and nudge it to a nose high steep bank so it can side slip and roll into a nice floaty glide. Do it right and you can all but imagine it as a finely trimmed free flight model.

Things to watch for that could well have been the issue are;
  • The strong polyhedral dihedral amount reacts STRONGLY to any rudder movement. This is amplified a LOT by excess speed. So maybe set up and use dual rates for the rudder so you can go low rate with about 1/4 inch of travel either side of neutral then switch to high rate for gliding with about a 25 or 30 degree rudder throw to either side.
  • Those are MASSIVE elevators. You won't need more than about plus and minus 1/4 inch of travel unless you're planning on some hot aerobatics.
  • Do a string alignment of the model if you have not done so already. That means checking the fuselage to ensure it's straight and that the fin and rudder are aligned at neutral to within a couple of degrees at most to the fuselage center line. And that's after making sure that the fuselage does not have a curve to either side. Then make sure the wing is equal in span to the outer dihedral breaks. Adjust as required and then measure back to the center line at the base of the fin's leading edge and be sure it's the same measurement within 1/8 inch to the trailing edges of the dihedral break line for the tips. Here again if the wing is out of square to the fuselage it'll act like the fin is offset and a strong bank will occur like you found. All that dihedral responding to any sort of angling of the wing again.
  • And of course you did check for warps and remove any or ensure that both sides have equal amounts of washout in the tips, right? Just checking.
  • It'll need a couple or three degrees of right thrust but if it's more than that it's likely too much. Measure from the prop tips back to the base of the fin and use the measurements to calculate the side angle.
Jul 29, 2015, 03:31 AM
I like real wooden aeroplanes!
Sundancer's Avatar
One would normally expect a model like this to need right thrust - if it had gone left with the torque I would have thought that lack of the side thrust might be the problem, the fact that it turned sharply RIGHT makes me suspect a warp as the probable cause.

As the above poster said, putting on a bigger prop will just produce more power and exacerbate any problems if it IS a warp. He is also right in saying that the rudder will be very powerful, you only need amazingly small amounts of rudder power with a model like this, any excess will just make it very "squirrelly". Just think of the TINY rudder trim tab we would use on a pylon free-flight model and how powerful it's effect is. Ditto for the elevators - you would trim a free-flight using 1/32" or even 1/64" packing under the tail so large movements are not needed. And this is basically a free-flight model.


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