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Old Nov 13, 2011, 07:54 PM
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What motor for a Carl Goldberg Ultimate 10-300??

I am aquiring a Carl Goldberg Ultimate 10-300. Looking to put a brushless motor in it. Any one with experience with a glow to electric conversion on this model??

Vincent
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Old Nov 16, 2011, 12:18 PM
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Vincent,

The main ratio you want to consider is "watts per pound". To do the Ultimate justice you don't want to go below 100 watts per pound. This will allow sport aerobatics. 200 watts per pound is what is used for aggressive 3D with

I had a Graupner Sukhoi designed for 0.50 glow (RIP). It had an E-Flite 60 (400 KV or 400 rpm per volt) powered by 6s 4000MaH (22.2V nominal). This set up swinging an APC 15x8 electric prop drew 50 amps producing 1000 watts. The model weighed 6.5 lbs and therefore had a power to weight ratio of 150 watts per pound. It would easily fly vertically out of sight.

I think you will enjoy 150 watts per pound on the Ultimate so lets use this figure as an example. If the all up weight is in the recommended 8 pound region, then you are aiming for 1200 watts static. You could take the same power train as my Sukhoi's had an prop it up to 16x8 or 16x10 to draw the required 60 amps static.

If the model is closer to the not uncommon 10 lbs then you want to either draw 75 amps from a 6S pack to get the 1500 watts or go for more cells in the pack, say 8S. 75 amps will probably not do a 400KV motor like the E-Flite 60 or a Hacker A50 much good so lets consider going up to 8S or 30 volts and 50 amps for argument's sake.

Now, a 400 KV motor like the above will take 50 amps easily but you will have to fit a toothpick of a prop to get the amps that low on 30V. Unless you are racing, you want as big a prop as your undercarriage will allow and a pitch to diameter ration of not less than 0.5, that is 14x7, 15x7.5, x16x8, etc. To keep your prop nice and big on 30V you will have to use a motor with lower KV, say 250 or 300KV. I have no practical experience here so you will have to do a little surfing to see what setups aare being used on 8S. Maybe look at software such as Electrical or go to manufacturers' sites, for they often publish recommended cell and prop ranges for their products. I know E-Flite do.

I just hopped onto E-Flite's site http://www.e-fliterc.com/Products/De...odID=EFLM4090A

Their Power 90 seems to fit the bill: 325KV and 1800 watts off 8S swinging an 18x8. You can prop down a bit to get to 1500 watts - or stay at 1800 watts if want insanity or your model is a porker.

The permutations are endless. I hope this gives you something to start with.

Kind regards,

Kenneth
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Old Nov 16, 2011, 05:33 PM
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I put together a CG 10-300 a couple of years ago using a Great planes Rimfire 4260-480, also known as a Rimfire 55. My effort weighed just over (lbs. I ran it on 6S with a 15/8 prop for around 1240 watts. It has enough power to loop from level but was not 3D.
If doing it again I would use a Scorpion 4025-12 with a 16/10 likely, about 1600 or so watts on 6S/5000 30C. A Scorpion 4020-14 with a 16/8 would also work well at about 1400 watts.
Here's a pic pf mine. FWIW Doug B
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Old Nov 16, 2011, 08:33 PM
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Kenneth and Doug,
Thanks for the information. Kenneth, I got some good info from your post. I will read it over again a couple of time so that I can understand it. Doug, thanks for your experience. It inspires me as to what I can do with my plane.

As I know the lipo will cost me more than what I have been used to paying for 3s batteries, what do you guys think about the turnigy motors from Hobby King?

Vincent
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Old Nov 16, 2011, 08:41 PM
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I use the Flightmax Zippy 6S/5000 30C from HK, they are about $55 and seem to stand up very well.
I use Turnigy's quite a bit, and most of my flying companions do too. Look for a motor with a KV of 400-50, I believe they make one called a 5065-400. Whatever you pick, make sure its rated for 1800 -2500 watts total, then you won't be stressing the motor at 14-1500w FWIW Doug B
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Old Nov 16, 2011, 08:46 PM
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Quote:
Originally Posted by vmaxmasonrya View Post
Kenneth and Doug,
Thanks for the information. Kenneth, I got some good info from your post. I will read it over again a couple of time so that I can understand it. Doug, thanks for your experience. It inspires me as to what I can do with my plane.

As I know the lipo will cost me more than what I have been used to paying for 3s batteries, what do you guys think about the turnigy motors from Hobby King?

Vincent

for instance, what do you guys think about this?

http://www.hobbyking.com/hobbyking/s...v%5F3150W.html

am I going in the right direction??
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Old Nov 16, 2011, 11:48 PM
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The 6364 230 you show will not work on 6S. It will take at least 10S.
I will reinstate the number again in case you missed them. You need a KV around 400-450 for 6S and a 15/16" propeller. You certainly don't require 3100 watts for this plane. 1800 would be fully 3D, not that I think this plane is good for 3D, it is for acrobatic manuveurs. ANything more than 1800 will result in needing bigger batteries (you will already need a 6S/5000/30C now).
I found this single battery hard enough to fit, going to 8 or 10S requires even more space and weight. JM2C FWIW Doug B
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Old Nov 16, 2011, 11:59 PM
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Quote:
Originally Posted by vmaxmasonrya View Post
for instance, what do you guys think about this?

http://www.hobbyking.com/hobbyking/s...v%5F3150W.html

am I going in the right direction??
Vincent,

The kv is too low on that motor, look at the recommended props ---22x12 / 24x10. You wont be able to swing a prop that large. I have an Ultimate that I havent finished, but when I get ready to, I'm thinking 8-10s packs and possibly this motor, but that kv may be still a little low, 325kv with 2000w power handling would probly be ideal, but an eflite power 110 is 295kv, sooooo


http://www.hobbyking.com/hobbyking/s...ner_Motor.html
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Old Nov 17, 2011, 01:23 AM
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The Scorpion 4025-12 would be my choice too. 6s has the added bonus that you can use two 3s batteries with a series harness so you can spread the expense and use the batteries singly on planes that use 3s and combined for the ultimate.
Lorenz
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Old Nov 17, 2011, 02:52 AM
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now Im kinda confused. isnt the 6364 comparable in power as a Eflite 60?
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Old Nov 17, 2011, 03:10 AM
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If I want to wire 2 lipos in a series, could I use 2 of these?
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Old Nov 17, 2011, 05:05 AM
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Vincent,

Given your comments on battery costs and that you are considering a $50 motor suggests to me that your budget will influence your selection. This is one reason why, if the model weight permits, I would gravitate towards a 6S system. There seems to be a price break point for 6S beyond which the cost of motors, controllers and chargers climb faster. Over 6S things start to be considered “high end”.

Another big reason is weight. Your motor choice is 50% heavier than the 400KV motors I have and it will require probably 10S to allow the prop to clear the ground which is heavier and more expensive. You will also need more expensive charger and controller. I used to be of the mind set that the more cells the better. Heck! Ten years ago I was flying a 60” .40 Ace RC Cloud Dancer which was supposed to weigh 4.5lbs with a 48 four stroke. I wedged an Astro 40G and 24 RC2400 nicads in it taking the weight up to 7.5lbs with 900 watts on tap. Yes it was impressive for its day and one of very few non competition models with over 100 watts per pound at the time, but it lost all the docile characteristics it was famous for and came in to land like a freight train. Every three flights the wire landing gear would bend so far back that the model was prone to nosing over so I had to swap legs around to regain some forward rake. This was on a tarmac strip. Now I am very much of the “less is more” school of thought where low wing loading is king.

David’s motor proposal is better than your choice in my opinion. It is lighter and similarly priced but the KV is still too low I think requiring 8S to swing a small enough prop to clear the ground.

I prefer Doug’s approach, except that Scorpion motors are amongst the best and pretty pricey. The E-Flite 60 is rated at 65 Amps for 15 seconds. So are Hacker A50s and the like. That is 1300 watts on 6S assuming 20V under load. I can guarantee that if propped right and at 9lbs or less your Ultimate will be lost in the clouds in 15 seconds. Remember that static wattage straight after a near peak charge will be a lot higher than flying wattage on account of the propeller “unwinding” and lower pack voltage. With the plethora of telemetry gear available nowadays I am sure somebody will be able to confirm precise ratios based on practical experience.

Many IC flyers whack open the throttle and leave it wide open most of the flight. If this is your style of flying then certainly follow Doug’s advice and buy a power train rated beyond the power you require to avoid overstressing it. However you will be paying more and carrying unnecessary weight. I have changed my ways and only use full throttle for vertical, otherwise it is 75% for steep climbs, 50% for level flights 25% for descents and 0 for dives. This way I can get away with using a smaller lighter power train which gets stressed occasionally for a few seconds at a time. The average amps pulled during the flight are well within tolerance, my power train is always only warm to the touch, my wallet is happier and my models more lightly loaded.

I think my views are supported by the professionals. I am looking at the supplement that came with RC Sport Flyer recent covering SEFF’s 10th anniversary show. It lists the power set ups of most of the models photographed. I notice that all the aerobatic models appear at first glance to be underpowered regarding motor size and cell count, but I am sure that the trade would not give top pilots like Somenzini, Jesky, Mann, McConville, et al. ill equipped models to demonstrate. What I interpret from the power setups used for demonstrations that make the models shine is that low wing loading is king and using lighter power trains stressed intermittently rather than over specifying the power train helps achieve this.

You can all wake up now.

As a parting shot, I have a set of CG Ultimate plans together with canopy and glass cowl in my possession. I will eventually scratch build a model from these redesigning the internal structure and aiming for 7lbs all up to be powered with one of the many 400Kv motors I possess and 6S or less.

Best wishes,

Kenneth
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Old Nov 17, 2011, 05:09 AM
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Originally Posted by vmaxmasonrya View Post
now Im kinda confused. isnt the 6364 comparable in power as a Eflite 60?
Vincent,

The 6364 produces 230KV which much lower than the E-Flite 60's 400KV. This means that to swing a prop small enough to clear the deck you are going to have to up the cell count to pull some sensible amps.

The 6364 is also 50% heavier than the E-Flite 60. It is altogether far too big in my opinion.

K.
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Old Nov 17, 2011, 05:11 AM
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Furthermore, the 6364's description states:

"Power equivalent : 30% scale warbirds or 3D planes up to 100inch and anything requiring a 45cc gas engine. This is a big motor which runs well on 10S 6,000mAh 20C lipolys swinging a 22inch prop.

In our tests we ran a 24x10inch prop on 10S with controlled throttle for extreme 3D on a 90inch Edge540."

Overkill is hardly the word...

K
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Old Nov 17, 2011, 11:57 AM
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Hobbyking has these motors that would work.
G60 400kv with a 15.10 prop $52
SK3 5045 450 with 15/8 $42
Turnigy 5055-400 with a 16/8 $30
Turnigy 5065-400 with a 16/17/10 $30
Scorpion 4020-16 (415kv) 16/17/10 $80 (currently out of stock)
All could be run with am 80A Turnigy Plush ESC ($40) on 6S. You'll have to check on stock, they go in and out pretty quick.
I'd match these up with a 6S/5000 or 5800mah Flightmax 30C battery ($55-65).
The 4025-12 would also be an excellent choice with a 16/12 on 6S, but much more costly. FWIW Doug B
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