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        Servos and power system for XL3200?

#1 jshelton Oct 23, 2001 05:39 AM

Servos and power system for XL3200?
The XL3200 from NSP is a 122" electric sailplane with a predicted flying weight of 72 oz. It has a beautiful built-up wing with flaps and ailerons. I have purchased the following power and radio equipment:

Mega 10 FAI SP motor (direct drive) (72 oz. thrust, 77+ amps)
A-120 speed control (80 amps) from Diversity Model Aircraft
10 Cell 2400 mAh battery from Diversity Model Aircraft
Hitec HS300 servos for elevator and rudder
Hitec 225MG metal-geared servos for flaps
Hitec Eclipse 7 with Supreme 8-channel receiver and 600 mAh receiver battery

I still haven't purchased servos for the ailerons so I'm looking for suggestions. I'm also looking for input on the suitability of the equipment I've purchased so far. Keep in mind my main goal is to end up with a thermal sailplane that is as light as possible but still gives me 2-3 decent (not vertical!) climbs to thermal altitude. I'm wondering if the power setup might be a little overkill especially since the motor weighs over 15 ounces. Seems like I could use a smaller motor battery too. Since my focus is on relatively gentle thermal flying I'm wondering if the 225Mg servos are overkill for the flaps.

I've only been flying electrics for a few months (Aspire EP) so I appreciate your feedback!


#2 Adam Neat Oct 23, 2001 06:36 AM

Hi Jim; One of the small Aveox or other brushless motors geared will give plenty of thrust. I use a Mag Mayhem geared in a 100" 70+ oz glider and it does fine on 8 cells and 25 amps. Any of the brushless setups mentioned would be lighter than that even and provide more power. Any geared system should be more effecient. You might wat to download the trial version of Motocalc and put in the parameters of your plane. You can do a lot of experimenting on there before you buy. Did someone recommend this setup you have?

#3 jshelton Oct 23, 2001 09:47 AM

Reply to Adam
Thanks Adam for your reply. Steve Belknap of Diversity Model Aircraft recommended the power setup. He knew how frustrated I had been with my Aspire EP which was woefully underpowered with the stock motor. I was trying to keep the costs reasonable so thta may be why he didn't recommend gear reduction ro another motor. I probably should have emphasized that I was looking for the lightest system possible with adequate power. I didn't know that the Mega 10 SP was that much heavier than comparable motors. In a nutshell, I'm looking for the best bang-for-the-buck/lowest weight system that will still provide good climb performance. I'm sure the system I have will work fine - I'm just concerned about the weight.


#4 Adam Neat Oct 23, 2001 11:02 AM

Well Jim Ill try to be honest. The setup you have is not inexpensive. For around $300.00 you could get a geared brushless setup that would equal the climb/thrust of your setup at about 1/2 the amps. For about $200.00 you could have a good geared brushed setup. Your setup will work but it is not effecient. I would return the Items; It doesnt sound like they are going to suit your needs. If you get a setup that draws less current you can get much lighter batteries and run a BEC controller. Your plane is big enough to handle the weight but if you want light weight you could save a lot there.

#5 jshelton Oct 23, 2001 12:06 PM

Adam -- Thanks again for your input. I think I agree with you! Can you recommend specific power setups for this plane in the 2 categories you mentioned so I can start shopping? The manufacturer (Reichard) recommends a motor with at least 350 watts of power.

Also, which BEC would be safe to use when running 6 servos? Everyone I've talked to at my club (Silent Electric Flyers Of San Diego) says that I shouldn't use a BEC controller with more than 3 servos.


#6 Adam Neat Oct 23, 2001 01:01 PM

Ok Here are a couple quickies; Jeti controllers are rated for 5 servos. You arent going to be flying around sawing the sticks. Also when you only use 7 or 8 cells its less of a load on the BEC circuit than using 10 cells. If you are worried about it, adding a RX pack and using a non BEC controller is always an option.
Brushless; Hacker B40 8L 4.4:1 gearbox $229.00 Jeti 40 controller $88.00

Brushed setup; Kyosho Endoplasma $19.00; 4.4:1 Gearbox $79.00 Jeti 50amp controller $80.00.

Ill get back on here later and provide some links. There may be some better setups as this was just a quick look around recommendation. Even at that either one of these would probably work good for what you want.
Hi Jim; Here is a good source for the Hacker Brushless setups. Talk to Sean and tell him the performance you are looking for. Dont forget to download the Motocalc program. It will help sort thru different options. I would look for 700 to 1000 fpm climb rate. That should give you a 30 to 45 second motor run to thermal height. I went to NES web site and looked at the XL. Its a beaut! I can understand you wanting to keep it light.
If you decide to get a brushed setup talk to Kirk at New creations. He should be able to fix you up with a good planatery gearbox and the Jeti controller. The Kyosho Endo motors are back ordered now at Tower Hobbies but there are a few other car motors that will work also. You may locate a Endo motor at a local hobby shop that sells car stuff.


#7 jshelton Oct 23, 2001 08:19 PM

Good info Adam. I'll go to the link and take a look.

BTW -- I totalled up the weight for the XL3200 and it comes out to quite a bit more than the predicted 72oz. With my current setup here are the weights:

Airframe: 47.5 oz
Motor,battery,speed control,prop: 38.5 oz
Radio equipment w/6 servos
and 3 oz600mAh receiver battery: 11+ oz.

Predicted total weight: 97 oz.
Predicted wing loading: 14.4 oz sq ft.

This is a lot higher than predicted on the NSP website. Even with a much lighter power setup I can't see it being much less than 84 oz. To hit the 72 oz. weight I would need a power system that weighs about 13 - 18 oz. depending on whether I use a separate receiver battery.

Actually, I'm fascinated by all of the technology and I'm determined to master it!

I really appreciate your time and input. I feel that most of the "common wisdom" from the club members is heavily influenced by their experience with hotliners and F5B ships. They usually have a focus on motor duration and plane speed rather than thermal duration. I'm usually one of the few at the field doing thermal duration flying.


#8 Tim Green Oct 23, 2001 09:20 PM

The so called "flying weights" are sometimes misleading. Try to find out the empty weight before you purchase. That way you can determine the true flying weight for your setup.

Another thing that can cause you to have more weight than you might have thought is the distance from the CG to the nose. A short distance (a short nose) sometimes means you need to either add weight to the nose, or use a heavier motor than you were going to. This can also be true for a tail heavy plane, even when the nose isn't short.

So two things - the empty weight and the balance - will determine your flying weight.

Tim Green

#9 Adam Neat Oct 23, 2001 09:47 PM

You should be able to get close to your predicted weight with the lighter setup. The 1200 and 1300 cells are close to 1oz lighter each and if you go with 7 or 8 cells instead of 10 youve got a lot there. The smaller motors should come out less than 10 oz with the gearbox and controller. Youre on the right track. Like Tim said if balance doesnt end up being a problem you could even try an 800ar cell and save a little more.

#10 jshelton Oct 24, 2001 08:57 AM

Motocalc results for XL3200
1 Attachment(s)
Thanks everyone for your input and suggestions. I downloaded a trial version of Motocalc and after a lot of exploration I came up with the following system which gives me flyign weight of about 80 oz. and a wing loading of about 12 oz./sq. ft. with motor time of over 4 1/2 minutes. The climb rate is 1310ft/min @ 44.9. My only concern is that the battery heat ranges from 157 to 106 degrees. Motocalc doesn't complain so I assume that the range is safe for this type of battery pack.

Hacker B40 10L
Sanyo 1100SCR; 10 cells
16x10in Prop w/6:1 Gearbox

Take a look and let me know what you think!


The performance table is attached and here's the 'opinion' report from Motocalc:
MotOpinion - XL3200-Hacker B40 10L
Sea Level, 65F

Motor: Hacker B40 10L; 3000rpm/V; 0.0177 Ohms; 1.29A idle.
Battery: Sanyo 1100SCR; 10 cells; 1100mAh @ 1.2V; 0.0043 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Generic 16x10in Prop w/6:1 Gearbox; 16x10 (Pconst=1.25; Tconst=0.956) geared 6:1.
Airframe: XL3200; 970sq.in; 80.8oz; 12oz/sq.ft; Cd=0.037; Cl=0.51; Clopt=0.72; Clmax=1.11.
Stats: 73 W/lb in; 65 W/lb out; 17mph stall; 21mph opt @ 49% (25:32); 25mph level @ 57% (20:02); 1310ft/min @ 44.9; -122ft/min @ -3.8.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (35A) falls between the motor's maximum efficiency current (25A) and its current at maximum output (242.3A), thus making effective use of the motor.

Aerodynamic Notes:

The static pitch speed (45mph) is within the range of approximately 2.5 to 3 times the model's stall speed (17mph), which is considered ideal for good performance.
With a wing loading of 12oz/sq.ft, a model of this size will have very sedate flying characteristics. It will be suitable for relaxed flying, in calm or very light wind conditions.
The static thrust (81.4oz) to weight (80.8oz) ratio is 1.01:1, which will result in very short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and steep climb-outs.
At the best lift-to-drag ratio airspeed, the excess-thrust (54.9oz) to weight (80.8oz) ratio is 0.68:1, which will give steep climbs and excellent acceleration. This model should be able to do consecutive loops, and has sufficient in-flight thrust for almost any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.

#11 Adam Neat Oct 24, 2001 09:56 AM

Hi Jim; I dont think the B40 hackers are available with a 6:1 gearbox. They come with a 4.4:1. As far as the heat issue you should only be running the motor in short bursts; 30 to 45 seconds followed by hopefully several minutes of gliding with the motor off. Using the Motowizard feature is nice but it doesnt take things like what ratio gearbox is available in the configuration you need. Youre on the right track. I thought you were looking for a little more "mild" performance:D Heck the combo you picked has a +1:1 thrust ratio! A torque roll with a 122" glider would sure impress everyone:p Take another look at the Hacker setups available and juggle around your prop size/cell count. The B40's are good for 40 amps so keep the current under that. Also look at the readily available prop sizes and make sure you pick a size that is available.

#12 jshelton Oct 24, 2001 10:09 AM

Yeah -- I'm learning that Motocalc's database isn't necessarily accurate. It also seems to contain a lot of power setups that it at first suggests are optimum and then it tells you it unsuitable!Actually, I don't need vertical performance, but the Hacker motors seem to have about the lowest weight for the power I need.

I'll jump back into Motocalc and see if I can find a "real" solution!

Thanks, Jim

#13 Adam Neat Oct 24, 2001 11:54 AM

Youre close; I think with the same motor and the 4.4:1 gearbox; 8 cells and a 15X10 prop should be pretty close.

#14 Jack Rowland Oct 24, 2001 02:30 PM

Are you talking the 4.4 gear box from Aero-Model and if so, what is your opinion of the 19 turn Trinity with that box for a 2M, 50 oz.(?) climb and glide. Same idea, light weight to maintain the gliding performance as much as possible. 2 or 3 climbs and 20-30 minute bec?
Thanks - Jack

#15 Adam Neat Oct 24, 2001 02:56 PM

Yes Jack thats the one; If you want fewer climbs and lighter weight go with a hotter motor(fewer turns) The beauty of a setup like that is its easy and inexpensive to experiment with. You can catch some decent car motors on sale for less than $20.00. You should be able to get great performance out of a setup like that. If its one of the lighter built up 2 meter ships you might want to be careful. It would be easy to over-power.

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