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Old May 24, 2010, 06:17 AM
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Epsilon 90: Power system, etc

Hi guys,

I've just bought a CA Models Epsilon 90 and I'm trying to decide how I'll equip it. I won't have the airframe for a week or two.

This is a pattern/3D plane intended for either IC or electric power. I may use it for some entry level pattern aerobatics and I'll certainly be doing 3D also.

Specifications:
Span 1600mm (63")
Length 1650mm (65")
Weight 3.2kg to 3.3kg (7lb 1oz to 7lb 4oz)

Manufacturer's recommended powerplants:
Glow: .60 to .90 2 stroke (OS 91FX or similar)
Electric: HACKER C50 10XL or 12XL Acro

I'm pretty sure I'll go with an electric system but I don't have the cash for a Hacker C50. I'm thinking more along the lines of a Hacker, Hyperion, Scorpion, Reaper, Plettenberg or Motrolfly outrunner.

I know my way around electric power systems but I have no practical experience with stuff at this scale. All my existing electrics are relatively small so I could use advice on the best approach for a plane like this.
I'm trying to decide how much power I need and on what size prop. Then whether I should get there with 6s or 8s and what capacity.

I'm looking for plenty power for vertical manoeuvers, reasonable duration (say 8mins+ with 80% discharge) and low weight. Obviously it's always a balancing act between the 3.

Assuming an AUW of under 3500g (7lb 11oz) I think I should be aiming for about 1500kW and a prop anywhere from 16x8 to 18x12. Does that sound about right? I'll have to check ground clearance when I get the airframe to ensure the 18" isn't too big.

I'm thinking I should go with either 6s 5000mAh or 8s 4000mAh. Both of these would weigh about 800g.
So here's some systems I'm considering:

Hacker A50 16L
2 x 4s Flightmax 4000mAh 20C
18x10 prop
Approx 1600W

Scorpion 4035-380
6s Flightmax 5000mAh 30C
18x10 prop
Approx 1700W

Scorpion 4035-250
2 x 4s Flightmax 4000mAh 20C
18x10 prop
Approx 1450W

Hyperion ZS4025-14
6s Flightmax 5000mAh 30C
17x10 prop
Approx 1350W

Hyperion ZS4025-16
2 x 4s Flightmax 4000mAh 20C
17x10 prop
Approx 1700W

Hyperion ZS4035-12
2 x 4s Flightmax 4000mAh 20C
17x10 prop
Approx 1950W

Reaper GR-60XL
6s Flightmax 5000mAh 30C
18x10 prop
Approx ????W

I like the look of the Scorpion 4035-380 combo. It would be one of the lightest and should have lots of power. I do have one reservation about the Scorpions; they don't allow for a bolt on adaptor as far as I can see and I'm not sure I like the idea of a collet adaptor on an 18" prop at over 1.5kW.
The two Hyperion ZS4025 combos would also be light and both look good. Anyone got experience with these?

As you can see I've been focusing on 17" & 18" props. Does that seem about right or should I be looking at 15" and 16" props? I'll probably be using Zoar, APC-E or perhaps I'll try the Turnigy wooden props.

I'd love to hear your comments on any of those combinations or others I might have overlooked. Particularly if you've tried the Epsilon 90 but also if you've any experience with other planes of this size and type.

The big questions are:
How much power? (approx 200W/lb?)
6s or 8s? (not much difference in weight, 6s is probably cheaper)
Cell capacity? (I'll be very happy with 10 minutes of mixed flying and 8 would do.)
Prop size?
Motor size? (Is it worth saving 100g of weight on the motor at the expense of some efficiency and throttle response. e.g. Hyperion 4025 versus 4035)
Motor brand? (Any that tend to be noisy, hard to mount, etc...)

I'd be very grateful for any feedback and sorry for rambling on a bit!

Aidan
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Old May 24, 2010, 12:53 PM
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If you will calc a wing area I'll plug a couple of your proposed setups into Motocalc for you.

Personally, having flown similar models, I'd stick with an 8S power system designed around a Hacker C50. I know you don't want to spend that much and I understand but a geared inrunner is a much better power solution, IMHO. If I were going to choose an out-runner power system, I'd go for your combination with the Hacker A50-16L and the 18x10 APC.
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Old May 24, 2010, 05:56 PM
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Hi Wiz,

What are the most notable advantages of the inrunner solution for this sort of application? Throttle response? Efficiency?... a bit of both?

I believe the wing area is 49sqdm (760sqin).
I have Motocalc myself but haven't looked at it for this yet. There's pretty good bench test data available for most of the combos I've listed and that's all I've looked at so far. Haven't looked at the dynamic stuff via MotoCalc yet. However if you don't mind throwing an eye over the figures and sharing your opinion I'd certainly appreciate it.

Thanks,

Aidan
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Old May 24, 2010, 09:52 PM
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Have you looked at the Motrolfly 4325-380, on 6s a 18x8 gives you 14lbs thrust at 1300 Watts and a 18x10 gives you over 16lbs thrust at about 70 amps, 1500 watts. It's made for 70" planes, but may work well if it is not too heavy at 14 ounces, 16 ounces with all hardware.

Ken
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Old May 24, 2010, 10:48 PM
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Quote:
Originally Posted by Aio_1 View Post
Hi Wiz,

What are the most notable advantages of the inrunner solution for this sort of application? Throttle response? Efficiency?... a bit of both?

I believe the wing area is 49sqdm (760sqin).
I have Motocalc myself but haven't looked at it for this yet. There's pretty good bench test data available for most of the combos I've listed and that's all I've looked at so far. Haven't looked at the dynamic stuff via MotoCalc yet. However if you don't mind throwing an eye over the figures and sharing your opinion I'd certainly appreciate it.

Thanks,

Aidan
From my experience the inrunner throttle response is far superior to that of an outrunner. It makes sense too. The inrunner is already spinning quite fast when you ask it to acclerate. Also, It has less rotating mass to get up to that speed. It's also more efficent. Lastly, I like the little extra noise especially when opperating at a field where most people are running loud engines. I can at least hear my plane a little.

Motocalc will have to wait until tomorrow.... It's getting late and I don't have a copy here on this computer.
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Old May 25, 2010, 11:05 AM
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Motocalc Hacker A50-16L

This one looks pretty good if not a little slow on the top end. Might try an 18x12... That's what I use with my 8S powered Yak 54.

Quote:
MotOpinion - Untitled
800ft above Sea Level, 29.92inHg, 56F

Motor: Hacker A50 16L; 270rpm/V; 1.7A no-load; 0.031 Ohms.
Battery: Thunder Power TP3800 (G4 ProPower 45C) (45C); 8 cells; 3800mAh @ 3.7V; 0.002 Ohms/cell.
Speed Control: Scorpion Commander 70A; 0.0013 Ohms; High rate.
Drive System: APC 18x10 Electric; 18x10 (Pconst=1.08; Tconst=1) direct drive.
Airframe: Epsilon 90; 760sq.in; 133.6oz RTF; 25.3oz/sq.ft; Cd=0.044; Cl=0.1; Clopt=0.46; Clmax=0.81.
Stats: 199 W/lb in; 174 W/lb out; 29mph stall; 38mph opt @ 69% (33:30, 94F); 83mph level; 3765ft/min @ 90; -485ft/min @ -8.3.

Warning:

MotoCalc was unable to determine a throttle setting for hands-off cruise airspeed, so the best lift-to-drag ratio airspeed and throttle setting will be used instead.
Inability to determine a throttle setting for an airspeed usually means the model is not capable of reaching the required speed with the given power system, or the airfoil information has not been specified correctly.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (48.3A) falls approximately between the motor's maximum efficiency current (39.7A) and its current at theoretical maximum output (464.8A), thus making effective use of the motor.
The voltage (28.6V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Possible Aerodynamic Problems:

The static pitch speed (66mph) is less than 2.5 times the stall speed (29mph), which may result in reduced performance at typical flying speeds and a low maximum speed. This situation is usually acceptable for an electric sailplane or other slow-flying model.
Pitch speed can be increased by using a higher pitched and/or smaller diameter propeller, a higher cell count, or some combination of these methods.

Aerodynamic Notes:

With a wing loading of 25.3oz/sq.ft, a model of this size will have flying characteristics suited to the intermediate pilot, for use in calm to moderate wind conditions.
The static thrust (246.8oz) to weight (133.6oz) ratio is 1.85:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (132.8oz) to weight (133.6oz) ratio is 0.99:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.
These calculations are based on mathematical models that may not account for all limitations of the components used. Always consult the power system component manufacturers to ensure that no limits (current, rpm, etc.) are being exceeded.
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Old May 25, 2010, 11:11 AM
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Hyperion HP-Z4035-14

Here is another good one.

Quote:
MotOpinion - Untitled
800ft above Sea Level, 29.92inHg, 56F

Motor: Hyperion HP-Z4035-14; 299rpm/V; 1.8A no-load; 0.0345 Ohms.
Battery: Thunder Power TP3800 (G4 ProPower 45C) (45C); 8 cells; 3800mAh @ 3.7V; 0.002 Ohms/cell.
Speed Control: Scorpion Commander 70A; 0.0013 Ohms; High rate.
Drive System: APC 18x10 Electric; 18x10 (Pconst=1.08; Tconst=1) direct drive.
Airframe: Epsilon 90; 760sq.in; 132.8oz RTF; 25.2oz/sq.ft; Cd=0.044; Cl=0.1; Clopt=0.46; Clmax=0.81.
Stats: 221 W/lb in; 176 W/lb out; 29mph stall; 38mph opt @ 62% (37:06, 93F); 82mph level; 4216ft/min @ 90; -484ft/min @ -8.3.

Warning:

MotoCalc was unable to determine a throttle setting for hands-off cruise airspeed, so the best lift-to-drag ratio airspeed and throttle setting will be used instead.
Inability to determine a throttle setting for an airspeed usually means the model is not capable of reaching the required speed with the given power system, or the airfoil information has not been specified correctly.

Possible Power System Problems:

The full-throttle steady-state motor temperature (382F) is extremely high, which will likely damage the motor unless full-throttle is used sparingly and cooling is good (even then, damage is possible).
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (59.1A) falls approximately between the motor's maximum efficiency current (38.6A) and its current at theoretical maximum output (415.1A), thus making effective use of the motor.
The voltage (28.5V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Possible Aerodynamic Problems:

The static pitch speed (66mph) is less than 2.5 times the stall speed (29mph), which may result in reduced performance at typical flying speeds and a low maximum speed. This situation is usually acceptable for an electric sailplane or other slow-flying model.
Pitch speed can be increased by using a higher pitched and/or smaller diameter propeller, a higher cell count, or some combination of these methods.

Aerodynamic Notes:

With a wing loading of 25.2oz/sq.ft, a model of this size will have flying characteristics suited to the intermediate pilot, for use in calm to moderate wind conditions.
The static thrust (247.1oz) to weight (132.8oz) ratio is 1.86:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (150.9oz) to weight (132.8oz) ratio is 1.14:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.
These calculations are based on mathematical models that may not account for all limitations of the components used. Always consult the power system component manufacturers to ensure that no limits (current, rpm, etc.) are being exceeded.
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Old May 25, 2010, 11:15 AM
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Hacker C50-10XL

This is my favorite... I actually fly this setup in my Yak with a pair of Zippy FlightMax 4S 5000 mah batteries. It's fantastic!

Quote:
MotOpinion - Untitled
800ft above Sea Level, 29.92inHg, 56F

Motor: Hacker C50 10XL; 1624rpm/V; 1.26A no-load; 0.0118 Ohms.
Battery: Thunder Power TP3800 (G4 ProPower 45C) (45C); 8 cells; 3800mAh @ 3.7V; 0.002 Ohms/cell.
Speed Control: Scorpion Commander 70A; 0.0013 Ohms; High rate.
Drive System: APC 18x12 Electric; 18x12 (Pconst=1.08; Tconst=1) geared 6.7:1 (Eff=95%).
Airframe: Epsilon 90; 760sq.in; 131.8oz RTF; 25oz/sq.ft; Cd=0.044; Cl=0.1; Clopt=0.46; Clmax=0.81.
Stats: 211 W/lb in; 191 W/lb out; 29mph stall; 38mph opt @ 57% (41:28, 69F); 82mph level; 4569ft/min @ 90; -482ft/min @ -8.3.

Warning:

MotoCalc was unable to determine a throttle setting for hands-off cruise airspeed, so the best lift-to-drag ratio airspeed and throttle setting will be used instead.
Inability to determine a throttle setting for an airspeed usually means the model is not capable of reaching the required speed with the given power system, or the airfoil information has not been specified correctly.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (58.6A) falls approximately between the motor's maximum efficiency current (55.3A) and its current at theoretical maximum output (1212A), thus making effective use of the motor.
The voltage (28.5V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Aerodynamic Notes:

The static pitch speed (77mph) is within the range of approximately 2.5 to 3 times the model's stall speed (29mph), which is considered ideal for good performance.
With a wing loading of 25oz/sq.ft, a model of this size will have flying characteristics suited to the intermediate pilot, for use in calm to moderate wind conditions.
The static thrust (246.8oz) to weight (131.8oz) ratio is 1.87:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (163.9oz) to weight (131.8oz) ratio is 1.24:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.
These calculations are based on mathematical models that may not account for all limitations of the components used. Always consult the power system component manufacturers to ensure that no limits (current, rpm, etc.) are being exceeded.
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Old May 25, 2010, 11:21 AM
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Hacker A50-16S

This is a 6S setup. It's not bad really... I didn't have the specs of the Scorpion 4035-380 so I picked a similar Hacker motor instead.

Quote:
MotOpinion - Untitled
800ft above Sea Level, 29.92inHg, 56F

Motor: Hacker A50 16S; 380rpm/V; 2A no-load; 0.026 Ohms.
Battery: Thunder Power TP3800 (G4 ProPower 45C) (45C); 6 cells; 3800mAh @ 3.7V; 0.002 Ohms/cell.
Speed Control: Scorpion Commander 70A; 0.0013 Ohms; High rate.
Drive System: APC 16x10 Electric; 16x10 (Pconst=1.08; Tconst=1) direct drive.
Airframe: Epsilon 90; 760sq.in; 122.3oz RTF; 23.2oz/sq.ft; Cd=0.044; Cl=0.1; Clopt=0.46; Clmax=0.81.
Stats: 159 W/lb in; 137 W/lb out; 28mph stall; 37mph opt @ 60% (33:42, 91F); 79mph level; 3090ft/min @ 73.5; -464ft/min @ -8.3.

Warning:

MotoCalc was unable to determine a throttle setting for hands-off cruise airspeed, so the best lift-to-drag ratio airspeed and throttle setting will be used instead.
Inability to determine a throttle setting for an airspeed usually means the model is not capable of reaching the required speed with the given power system, or the airfoil information has not been specified correctly.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (53.2A) falls approximately between the motor's maximum efficiency current (40.7A) and its current at theoretical maximum output (414.3A), thus making effective use of the motor.
The voltage (21.4V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Aerodynamic Notes:

The static pitch speed (69mph) is within the range of approximately 2.5 to 3 times the model's stall speed (28mph), which is considered ideal for good performance.
With a wing loading of 23.2oz/sq.ft, a model of this size will have flying characteristics suited to the intermediate pilot, for use in calm to moderate wind conditions.
The static thrust (175.4oz) to weight (122.3oz) ratio is 1.43:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (109.7oz) to weight (122.3oz) ratio is 0.9:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.
These calculations are based on mathematical models that may not account for all limitations of the components used. Always consult the power system component manufacturers to ensure that no limits (current, rpm, etc.) are being exceeded.
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Old May 25, 2010, 11:22 AM
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One last thing, Aidan. I didn't know if the weight you posted was a ready to fly weight or an empty airframe weight. I used it as an empty airframe weight in the calcs above. Again, if I were going to use any of those 8S outrunner setups I'd go up to a 12 pitch prop for the additional speed. If the system got too hot I'd then drop back 1 inch in diameter. All of these power systems are well above the power you'd need for most pattern flying.

I hope this helps....

Wiz
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Old May 27, 2010, 01:45 PM
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Joined May 2002
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Thanks a million for all your help Wiz!
I think I'll go with the A50-16L. Perhaps on an 18x10 for mostly 3D or 17x12 for mostly pattern. I need to check the ground clearance. I think it's okay for 18" but I could change the landing gear if necessary.
I'd love to try a C50 but just can't afford it right now. Maybe next time!

As far as the weight is concerned. The plane is advertised as 3.2 to 3.3kg but it's not clear if that's the expected dry weight for an IC version or electric. I don't have an empty airframe weight yet. There's not a whole lot of info around for his plane. I have found one electrified version on RCGroups and it came in around 4kg! I think I'll have a lighter power system and hope to bring it in under 3.5kg but will need to cater for more just in case.



Next decision is ESC, BEC and servos.
I'm thinking: Jeti Spin 75 Opto, CC Phoenix HV85, Phoenix ICE 75SB or Hacker X-80 Opto Pro 3D

The ICE 75SB has a switching 5A BEC and is reasonably priced but I'm not sure 5A is safe on 4 digital high torque servos so I think I'll go with a separate RX pack and regulator or an SBEC - great more weight and expense! What's common practice on this size plane?

Servos: I'm sure the Hitec HS-7985MG or JR DS8411 on all surfaces would do the job but is this overkill?
Perhaps the HS-5625MG or the analogue version of one of these servos would give almost equal performance?....yeah I know I'm trying to skimp!

Aidan
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Old May 27, 2010, 02:22 PM
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Quote:
Originally Posted by Aio_1 View Post
Thanks a million for all your help Wiz!
I think I'll go with the A50-16L. Perhaps on an 18x10 for mostly 3D or 17x12 for mostly pattern. I need to check the ground clearance. I think it's okay for 18" but I could change the landing gear if necessary.
I'd love to try a C50 but just can't afford it right now. Maybe next time!

As far as the weight is concerned. The plane is advertised as 3.2 to 3.3kg but it's not clear if that's the expected dry weight for an IC version or electric. I don't have an empty airframe weight yet. There's not a whole lot of info around for his plane. I have found one electrified version on RCGroups and it came in around 4kg! I think I'll have a lighter power system and hope to bring it in under 3.5kg but will need to cater for more just in case.



Next decision is ESC, BEC and servos.
I'm thinking: Jeti Spin 75 Opto, CC Phoenix HV85, Phoenix ICE 75SB or Hacker X-80 Opto Pro 3D

The ICE 75SB has a switching 5A BEC and is reasonably priced but I'm not sure 5A is safe on 4 digital high torque servos so I think I'll go with a separate RX pack and regulator or an SBEC - great more weight and expense! What's common practice on this size plane?

Servos: I'm sure the Hitec HS-7985MG or JR DS8411 on all surfaces would do the job but is this overkill?
Perhaps the HS-5625MG or the analogue version of one of these servos would give almost equal performance?....yeah I know I'm trying to skimp!

Aidan
I have an ICE 80HV and I absolutely love it. I also have an old Hacker 77-O and it works fine too.

If you want affordable digital also check out the new offerings from Airtronics.
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Old May 27, 2010, 02:43 PM
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Aidan, My Sebart Angel S50 is very close to the same size as your Epsilon90, except it is 6.5lbs allup. I have used the Jeti spin75, CC85 HV, and now a CC Ice 100 in this plane all worked well with only a slight issue with the Jeti spin 75. That ESC needs good cooling to operate near its max rating [this is covered in the spin 75 manual].
As for servo's I am using three HS-5475 and one HS-5645, all powered by a Duralite 6V 7.5 amp regulator and a 2S 800mah lipo. I am only flying Pattern and each 7.5 min flight uses about 15ma. At that rate my servo's are drawing very little, I really could just use the Ice 100's 5 amp bec. IMHO even for 3d your servo choices seem overkill as the Epsilon 90 control surfaces do not look to be 3d sized, more pattern sized. Just my thoughts!

Always liked the look of the Epsilon 90, How is access for batt changes? Canopy hatch?

Dave.
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Old May 28, 2010, 05:09 AM
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Thanks for the feedback guys.

It looks like the ICE 75SB might be the best bet as it's got the BEC if I decide to use it. It just lacks Opto isolation but is that a big issue (I'll be using Jeti Duplex 2.4GHz radio)?

Thanks for your info on your Angel S50 setup Dave, nice plane. I've actually had a look at the Sebart Wind S110 manual for suggestions on power system and servos as it's a similar type and close on weight although it's a bit bigger. I reckon the Epsilon design will come in heavier than most newer designs of similar size. The heavier wing loading will mean higher servo loads for similar sized surfaces although I agree it's not likely to hit severe 3D levels.
I located the Epsilon 90 manual online and it recommends 6kg/cm (about 85oz/in) minimum for 3D flying. The Hitec HS-5625MG exceeds that and is pretty fast too. I think Airtronics are US only so might be harder to get spares locally if I need them. Or is Airtronics the same as Sanwa?

As designed I think the wing would need to come off to access the battery but I don't like that at all. It looks like the plane is designed primarily for IC use and doesn't really cater for battery installation. I intend to the modify it if possible to make the canopy removable or make a separate hatch. I won't have the airframe for another week or so and I'll need to see the structure to know what's possible. I'm trying to identify all the components I need now so I can get moving pretty quick once I receive the airframe. I probably won't order anything until I measure the empty airframe weight and check for prop clearance.

Hopefully the €uro won't keep de-valuing at this rate or the bits will get very expensive! I usually buy most of my gear from the UK or US.

Aidan
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Old May 28, 2010, 11:20 AM
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Aidan,

I looked at the Epsilon a while back and I felt that if I were to convert one, I would try to gain access to the batteries through the canopy. You could probably build a light weight frame to stiffen the canopy so that it could act as a hatch.

Good luck,

Teo
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