Part II: ICARE R/C Imports Let Model ASW 28-18 3m Electrifying Scale Model - RC Groups
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Part II: ICARE R/C Imports Let Model ASW 28-18 3m Electrifying Scale Model

Martin Pilko electrifies and reviews the Let Model ASW 28 3m Scale glider available through ICARE SAILPLANES. The high quality finish of the model is deemed as “the norm” with Let Model and even satisfies the biggest critics. In addition, the model is reasonably priced and will not disappoint scale glider enthusiasts from a performance perspective.

Splash

Introduction


Scale:1:6
Wingspan:118"(3000mm)
Wing Area:480sq.in.(31dm2)
Weight:53oz.(1500g)
Length:43"(1090mm)
Wing Loading:16oz./sq. ft.(50g/dm2)
Airfoil:S3021
Servos:HS50/85 JR368/168
Transmitter:Futaba14 MZ
Receiver:Hitec Super-Slim
Battery:4xSanyoAA1100mAh
Manufacturer:Let Model
Available From:Icare Sailplanes

The concept of electrifying a scale sailplane is not new. The latest buzz is the developments in LiPo’s (Lithium Polymer) batteries specifically focusing on weight to capacity ratio. R/C modelers focusing on electrics will tell you that the early hotter electric set-ups used to take up a lot of space in the fuselage and were considered to be quite heavy. With the evolution of all around lighter and smaller brushless motors, motor controllers and LiPo batteries the ability to apply a hotter electric set-up to a smaller model airframe is much more desirable and is becoming a big trend in the R/C world.

So why would anyone ever consider electrifying a scale sailplane? Well, one wouldn’t have to if they live nearby four slopes with one slope each facing North, South, East and West. In addition, the wind pattern conditions would always be “optimal” at one’s convenience in the evenings and on the weekends. Or, if one has the luxury of living near group of individuals who are quite active in aerotowing with a tug pilot who is more than happy to spend the weekend towing “other” gliders with a good size tow plane valued at $3-7K+. Since there are no tug planes in our club and the wind isn’t always blowing in the right direction on the slope, I had to improvise...and electrify.

The hardest thing to do is to overcome a notion of hacking off the nose off of a perfectly good scale sailplane. In this case, it was a bit more difficult because the craftsmanship of this model is extraordinary and I would consider the Let Model ASW 28 one of the most aesthetically pleasing scale planes in the 3m class on today’s market.

Kit Contents

The kit is reviewed in detail in Part I: ICARE R/C Imports Let Model ASW 28-18 3m Slope/Thermal Flying

Assembly

General Gear Install

I did not find the gear install a big issue since I already dealt with the “logistics” on set-up (how and where to install), type of gear to use (personal preference) and positioning of the servos, receiver and batteries in the non-electrified version of the scale model glider (See Part I).

I did make the decision to remove the retract system in the electric fuselage of the Let ASW 28. I found two benefits from removing the retract.

(1) Weight was saved by not installing the retract, servo and the linkage
(2) The ability to slide the LiPo in the fuse much easier to achieve a desired C.G. made things much easier

Electric Set-up

Below is a tabulated summary of components that are required to complete the electric version of the scale model. I believe that the “electric” combination for this glider works well due the light weight of the set-up and the ability to provide sufficient thrust to obtain a decent climb rate. The listed items below are all available through Icare Sailplanes.

Let Model ASW 28 3m Electric Version
Let Model ASW 28 3m Electric Version
LiPo's:ABF 3500HD 3S1P
Motor:PLETTENBERG Orbit 10-22
Controller:MGM Compro Easy40
Spinner/Prop:40mm x 5mm shaft, Cam 12 x 8

Electric Motor Install

There were several key steps:

  1. Cutting the nose to ensure the spinner blends in from a distance
  2. Set the firewall at the proper distance
  3. Select and set the thrust angle (I chose 0/0)
  4. Secure the firewall into the fuselage
  5. Change the joiner to carbon fiber to lose some overall weight

The first item at hand was to cut the nose of the glider in such a way to ensure the width/height of the fuselage and the spinner would “blend in” as if it wasn’t there, when looking at the fuselage from distance. The second item was to make sure that the firewall was not too far in or not too far out (just the correct distance) so the transition from the spinner to the fuse is "smooth". This was achieved by cutting the firewall a bit bigger and slowly sanding it down to achieve a desired fit. For the firewall I decided to use a circuit board. Circuit board is very sturdy and really easy to work with in my opinion. The third item to keep in mind was to obtain a desired angle for the motor install. It was decided to keep the angle perfectly perpendicular with respect to the horizontal and vertical axis (I decided that I would “mix” in the elevator to obtain “angle of climb” at various throttle positions - utilized radio for this purpose).

Initially, CA was utilized to bond the firewall to the inner fuselage. The Epoxy glue was then used to glue the outside portion of the firewall and fuselage. Finally, I glued the firewall from the inside of the fuselage as well utilizing GOOP. Why did I use all these glues? I used Epoxy glue to get a good bond from the firewall that sits just under the spinner. However, Epoxy is brittle. I've had instances where epoxy has broken off due to stresses. Because it is brittle, it sometimes does not take too much to brake off. Therefore, I utilized GOOP because it possesses elastic properties to give that extra bond so the firewall is secure. I believe that what I did is not quite necessary on smaller models; however, if anyone plans to electrify larger models I strongly suggest the exercise of utilizing the "extra" glue, mostly due to the larger torque.

My goal was to use the original canopy latching mechanism, thus, as illustrated in the photos, I “shaved” away a portion of the latching mechanism to be able to comfortably fit the motor in the fuselage.

Weight Comparison Non-Electric vs. Electric version

Notice that the weight difference between the electric and non-electric version (utilizing carbon joiner) is only 287 grams (10 oz) at a total up weight of 1787 grams in the illustrated chart below. I believe that it is possible to do even better than 1787 grams if one really focuses on “lighter” gear and batteries, while still maintaining “functional integrity”.

The wing loading stated on the Let Model website for the non-electric version at 1500 grams is 50 g/dm^2. At 1787 grams the electric version ASW 28 has calculated wing loading at about 59.6 g/dm^2. Wing loading of 59.6 g/dm^2 is still quite respectable in my opinion.

LiPo's Battery Performance

Below is a chart tabulating the Time, Capacity, Amps, Watts and Volts.

Every thirty seconds of run time I took the readings on a Watt/Clamp Meter. I took about 2 minutes of a break and repeated the step. I was concerned with overheating the electronics because the equipment did not have sufficient airflow for cooling sitting on a bench.

The results were:

  1. One can expect approximately 6.5 minutes of run time.
  2. Expect to discharge the cell to about 3000 mAh before the power significantly drops off.
  3. The battery significantly holds capacity for about five minutes of run time.
  4. Expect maximum draw down of about 32 Amps with a freshly charged battery - stabilized at about 25 Amps.

Final Assembly photos of the Let Model ASW 28-18 3m

The photos below speak for themselves. My strategy was to position the LiPo's in the fuselage to get a desired C.G. In addition, a decision was made to utilize an "extra" battery for the receiver - 4x 100 mAh Sanyo AA cells. The utilization of the additional battery (I made a decision not to utilize the BEC to power the servos and receiver) was made to ensure that if I drain the main battery, I don't lose the model. If one chooses to utilize LiPo's with BEC, it is possible to shave off about 100 grams from the total weight.

Flying

I'm not going to go to extra length to discuss flying; however, I will briefly discuss the flying "behavior" of the electric version of the model. Flight performance was covered in detail in Part I.

The electric version is quite well behaved. I was pleased that the controller, motor and battery combination provides enough power that a running start is not necessary. It is safe enough to stand in one spot and the model will fly without any issues with a moderate hand toss (see the video below). In about 30 seconds it is possible to climb to ~ 700 feet. It all depends on personal preference on how aggressive one decides to be with the climb angle.

There does not seem to be too much of a difference between the electric and non-electric version with respect to their weight differences and flight behavior. Although, as mentioned in Part I, thermal flying is a bit different. It is important to get an understanding of the model's behavior (i.e. how slow can you really fly and not stall the model).

On a moderate thermal day I may get up to 1.5 hours of flight time with one LiPo pack. On the worst day with wind and broken thermals I achieved about to 45 minutes on one battery pack. I believe that it is possible to achieve about 10 to 12 climbs to about 700 feet on one LiPo pack. I've done up to 20 climbs to about 400 feet or so. How high an individual decides to fly is all dependant on the person's comfort level.

Flight Video/Photo Gallery

Downloads

Conclusion

I truly enjoyed flying and testing the model. I do have to admit that I had more enjoyment flying the electric version than flying the non-electric version on the slope/aerotow. Why? I had to wait for the wind in the right direction and just the right velocity or find a tug pilot with the stock version. With the electric version the weather was not an issue as long as it wasn't raining (although at times this does not stop some people).

I would like to thank Etienne with Icare Sailplanes for providing support and giving me the opportunity to test the model/power system and write a review. If you're one of the people who always wanted to try something different but were not quite sure how to go about it, then here is your chance to get started.

Last edited by AMCross; Sep 05, 2006 at 11:28 AM..
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Sep 05, 2006, 01:23 PM
Registered User
jetjocchris's Avatar
Great Write up. Can't wait to get mine and see for myself how beautiful a scale ship looks in flight. Righ tnow I'm just playing with an Easy Glider Electric, which I must say has been a blast with the brushless upgrade.

About what climb angle can you get with the above described setup?? I bet 45 degree or better....??

Chris
Sep 05, 2006, 05:14 PM
Registered User
Thank for the sharing of builds.
I am really impressed by the power combo you use is so 'LIGHT', maybe I am too much 'poisoned' by those F5B things. Is that combo recommended by Etienne ? I must re-think the powering of my models.

David
Sep 05, 2006, 08:27 PM
Registered User
In my opinion, you can do better than 45 degrees. I would say that up to 45 degrees, the climb angle is safe (to eliminate stalling).

Martin

Quote:
Originally Posted by jetjocchris
About what climb angle can you get with the above described setup?? I bet 45 degree or better....??

Chris
Sep 05, 2006, 08:29 PM
Registered User
Yes, Etienne is the mastermind behind the "electric combo" for the model

Quote:
Originally Posted by C-MIC
Is that combo recommended by Etienne ? I must re-think the powering of my models.

David
Sep 05, 2006, 10:03 PM
Registered User
Very nice setup!

I have been wanting a scale electric powered scale sailplane. This approach is much less expensive than the pop up self lauch systems. I wonder how a Salto, L213A, LF-107 LUŇÁK or other aerobat would do as a conversion. I would have a hard time cutting off the nose of one of those beautiful planes. The rewards could outway the hack with a plane that can be flown with more confidence at least for a non seasoned glider pilot like myself not having to fear getting back up a slope or making it back to the LZ.
Sep 06, 2006, 12:29 AM
One Idiot is plenty...
Dbox's Avatar
Flying my Electrified Salto Baudis 2.4m third day in the row.Cant get enough of it.
What a beautiful glider.Tested today with different motor,flies even better.
Have no time to post a pics,but if somebody really interested-bug me.
Next project for "nose job" L-213,waiting in the box.
D...
Sep 06, 2006, 05:08 AM
Horned one
zero-zero's Avatar
Dbox, I'd love to know what's your motor setup in the Salto

On Edit: Whoops, forgot this thread is an article about the LET ASW 28. Let's please split this to a new thread. Sorry.
Last edited by zero-zero; Sep 06, 2006 at 05:43 AM.
Sep 06, 2006, 05:16 AM
Registered User
Yes yes I would like photos of the spinner fuselage interface and the whole installation on the Salto. How is the weight and how do you slow it down to land? Does it want to tip stall at lower speeds?
Sep 06, 2006, 10:11 AM
Registered User
Hi Martin,
Very very nice review. It should be an eyeopener for many that are on the fence about electifying scale models. Hope to read more on elec. conversions in the near future.

Regards,

Richard
Sep 06, 2006, 07:16 PM
Registered User
D-Box how does it thermal?I have asw-28 electrified (3m) and would like something smaller so I would be interested to hear your flight report.

Daniel
Sep 06, 2006, 07:17 PM
Registered User
By the way great review!
Sep 06, 2006, 09:29 PM
One Idiot is plenty...
Dbox's Avatar
Quote:
Originally Posted by GHOST RIDER
D-Box how does it thermal?I have asw-28 electrified (3m) and would like something smaller so I would be interested to hear your flight report.

Daniel
We have to appologize for highjacking this thread.ASW 28-18 is in my list for "nose job".It was a big surprise for me how easy it took of your hand with this 350W motor.I allways overpower all of my planes.So in this one I would probably go for Orbit 15-14 or Cyclon 10 just 30-40 gr.heavier motor and almost twice as powerfull.You have to think about different battery-10c battery is suck.
Cyclon 10 BTW rated as 200gr.motor everywhere,but it weights 185gr.
Salto flys more like a hotliner,you have to keep it going,it might thermalls well but it is not my favorite style of flying.I like high speed low passes with a wistle,which is Salto does pretty well.I fly it with two different motors Cyclon 10 and Plattenberg 220/20/A3 P4 5.2:1 gear. Both 3s 3200 20C battery.
Next motor to try is Lehner Basik XL 5.2:1 gear.So far I liked Platt.motor better.
Guys,I feel uncomfortable in somebodys report,send a PM if you have a questions.Thanx.
D...
Sep 07, 2006, 11:54 PM
Registered User
Dbox,

I disagree that you require more "powerful" or "heavier set-up". Firstly, the power set-up in this review is more than is required for “power/climb rate”. Secondly, this kit is really well designed and you will have problems balancing it if you’re heavier in the nose. If you go heavier, because the LiPo’s are light, you will have to place the batteries even further back in the fuselage to achieve balance at the expense of a heavier overall model weight.

Keep in mind that you want the model as light as possible to thermal.

Just my 2 cents,
Martin

Quote:
Originally Posted by Dbox
We have to appologize for highjacking this thread.ASW 28-18 is in my list for "nose job".It was a big surprise for me how easy it took of your hand with this 350W motor.I allways overpower all of my planes.So in this one I would probably go for Orbit 15-14 or Cyclon 10 just 30-40 gr.heavier motor and almost twice as powerfull.You have to think about different battery-10c battery is suck.
D...
Sep 08, 2006, 07:14 AM
Registered User
Quote:
Originally Posted by Dbox
We have to appologize for highjacking this thread.ASW 28-18 is in my list for "nose job".It was a big surprise for me how easy it took of your hand with this 350W motor.I allways overpower all of my planes.So in this one I would probably go for Orbit 15-14 or Cyclon 10 just 30-40 gr.heavier motor and almost twice as powerfull.You have to think about different battery-10c battery is suck.
Cyclon 10 BTW rated as 200gr.motor everywhere,but it weights 185gr.
Salto flys more like a hotliner,you have to keep it going,it might thermalls well but it is not my favorite style of flying.I like high speed low passes with a wistle,which is Salto does pretty well.I fly it with two different motors Cyclon 10 and Plattenberg 220/20/A3 P4 5.2:1 gear. Both 3s 3200 20C battery.
Next motor to try is Lehner Basik XL 5.2:1 gear.So far I liked Platt.motor better.
Guys,I feel uncomfortable in somebodys report,send a PM if you have a questions.Thanx.
D...
Firstly pls excuse me to discuss matters beyond the theme of this thread.
Dbox, I think you need at least 5s, (6s is most moderate in my book, again too much poisoned by the f5b mind).to justify your Pletti. But with 3s it will work at 3-400w, at which current that Pletti will live forever.
Also what gearbox do you use for Lehner? It is a hot motor really.

David


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