Welcome to the first edition of LET'S ASK BOB. Nearly every day I receive questions from FlightImages readers all over the world asking for my help with new scale models, advice on choosing a new project, or just some help in getting started...something all of us can remember needing once upon a time. My years of experience as a public school math teacher remind me that when one student gets around to asking a question, there are probably many more right alongside him or her looking for the same explanation. With this in mind, I am taking the liberty of sharing questions and answers that I hope will be interesting to many of you.

Please keep in mind that what follows is a sharing of my opinions, based on my experience. When I don't know the answer, I'll say so. It may often happen that one of you "out there" will have just the insight or information that is needed...when that happens, please jump in and share what you have learned with the rest of us.

At present I am not equipped to host a Chat Room, nor do I see that as being very likely in the near future. However, considered responses to thoughtfully posed questions will always be welcomed and I will do my best to share all of them with you right here.

Gerard Dolan of Baltimore wrote:

Hi Bob! Congrats on breaking the electric competition barrier! Would you know of any plans or kits for any of the Grumman flying boats: Goose, Mallard or Widgeon? Thanks for any help you can offer!

Gerard,

Although I have seen mention in several of the magazines from time to time of Grumman amphibians, I am not aware of a kit anywhere. I would get a catalog from Cleveland Model & Supply Co. As you may know, they are the "old" Cleveland kit company that made all those neat rubber power scale jobs during the WWII era and into the 1950's...there are no more kits, but they have an excellent selection of scale plans that can be adapted for R/C.

Call them at (317) 257-7878 for price and order info for a catalog. I'm not sure whether they will have what you want, but it's worth checking.

There may be other plans out there of which I am not aware, as well. Let me know if you find one.

Paul Susbauer wrote:

Mr. Benjamin,

I am building an electric powered RV-8 homebuilt, that is roughly the same dimensions as your Tigerkitten. I am planning to power the plane with either a geared Astro 05 or 15, or the MEC Turbo 10 motor. I was wondering if you have any suggestions on power systems, especially on these mentioned here. From my calculations, I estimate that it will need a 10-12 cell pack. The RV will be of built-up balsa and lite ply fuselage with sheeted foam wings and tail. I would love to hear any suggestions about the power systems and the general design you may have.

Paul,

Thanks for sharing the questions on your proposed RV-8. In short, it sounds like a good project. My guess is that it will fly OK on either the MEC or one of the Astro motors. I'm not a techno-jock and can't give you lots of specs for comparison, but an empirical impression based on a lot of flying may help you make a decision. Simplistically, the MEC Turbo 10 motors are basic ferrite magnet "car motors" developed to a high degree of sophistication. They will give you a bit more performance on a given number of cells that an Astro 05 or 15, but will not last nearly as long. A Turbo 10 will need brush replacement and commutator cleaning as often as every 20 or 30 flights, and may just roll over and die if you don't attend to those maintenance chores; however, there is no question but that a Turbo 10 on 6-1 gearing (their standard for this size airplane) and 10 cells would fly your airplane very well. On the other hand, I have small Astro motors that have flown for years and still run fine on the original brushes...these motors are really class acts of fine engineering and manufacturing...slightly heavier and not quite as fast as the Turbo, but longer lasting.

Using Astro motors, you might want to go for minimum weight and run a standard gearbox 05 on 9 or maybe even 10 cells...this combo flew my No. 1 TigerKitten really well for many years. On the other hand, I have seen 'Kittens (mine and others) fly just fine at or over four pounds...you might want to go for a standard geared Astro 15 and 12 cells for a little more all-out power and perhaps better stability in rough air based on a higher wing loading.

I haven't had a lot of experience with foam, but have seen a lot of airplanes built very well using it. My impression is that it would give you a lot of structural accuracy at the expense of a few extra ounces...if you can keep weight down otherwise, as in using really well selected contest grade wood, some foam cores might be a good way to go. At the power level you are dealing with using any of the motors we are talking about, you do not need to be concerned about two or three ounces "making or breaking" a model.

Please let me know how the project works out.

Paul wrote back a bit later with an update on the project:

The plans are pretty well finished, and based on input I recieve from a couple E-flyers up at the Puyallup show (yours included) I have decided on a geared Astro 05, with a Hitec 555 mini reciever, Hitec HS-85 Mighty Micro Servos (42 oz/in at only .70 oz weight) The foam wing will have sheeting on the leading edge, with fake capstrips aft of the spar, with the foam cut out where there is no sheeting. The fuselage is being designed to be fully interlocking. This will make a straighter model. Now that I'm almost finished with the plans for the plane, I have to keep busy during drafting class so I am already onto another design, a little Ercoupe for Speed 400 power. (I have about a dozen or more planes in my mind waiting for the drawing board.) Thats about it for now, I'll be starting on the construction of the RV in the next couple of weeks, so once I get something done, I send a picture or two. I don't know if I told you or not, but you have a really nice website.

Thanks,

Paul

Hey Bob,

I've learned from and enjoyed your various columns in S. & E.M., M.A.N., etc., and I really need some advice on my latest project. It's a Dornier 17 Bomber for twin SP 400's. I need to know how to wire a twin.

Could you describe? I'm fairly ignorant of terminology such as "series", and "parallel", so basic descriptions would be better. Also, should I incorporate down thrust? Any help you could give would be greatly appreciated and I'll send photos upon completion.

Thanks a lot,

Charles Kidd

Charles,

As promised, I have some specific info for you on wiring twin installations. There are three basic ways of setting up a multi engine (motor) installation. You can put both (all) motors in series, in parallel, or in independent circuits. Of course, there are variations, like wiring 4 motor setups in two pairs of series, or whatever, but it comes down to the three basic setups.

Using independent circuits means wiring each motor with its own battery and speed control, just as if it were in a single engine airplane. The speed controls for each motor are run "in parallel" off the one throttle channel output of the receiver using a "Y" connector wiring harness, just as would be the case in an engine powered model using two throttle servos. This appears to sacrifice the safety factor inherent in having both motors in the same circuit; that is, not having to worry about one failing while the other continues to run as is so often the case with glow engine powered models, but in fact the reliability of electric systems when they are properly wired and batteries are properly charged is so good that this isn't really a problem . As long as both speed controls are operating from the same signal source and are of course identical units, everything works fine. The output signal from the receiver, which "thinks" that controlling a speed control is just the same as controlling a servo, is sufficient to operate two units together. The exception to this rule might be when you are using a micro size radio with limited power output. Standard "sport size" receivers will handle the load OK.

Why would you use two speed controls and separate motor circuits? In the case of large models, where the combined voltage and/or current of two or more motor circuits would exceed the limits of the speed control, you must use separate controls. For instance, running two twenty cell motors on a controller with a 25 cell max rating would be asking the controller to handle 40 cells,and would not work. In the case of smaller models, this kind of problem doesn't occur and you can consider running two motors through one speed control.

When this happens, you must decide whether to run series or parallel. Here's what that means. Running in series means that both motors are hooked up like links in a chain along with the speed control. Visualize this...the positive wire off one motor is hooked to the negative wire from the second motor. The positive wire from the second motor goes to the positive motor output wire from the speed control, then the negative motor output wire from the speed control goes back to the negative wire on the first motor. The battery input wires from the speed control connect to the battery pack just as in a single motor installation. Each motor in series will "see" half of the battery pack voltage, so if for instance you have motors that want to run on seven cells each and you wire up in series, you need a 14 cell battery pack. However, the current load on the pack is only that of one motor. For instance, two motors drawing 15 amps each in this setup would put a total load of only 15 amps on the pack.

Running in parallel means that the motors run side by side, rather than in a chain. Visualize that the motors are laid next to each other and both positive wires are hooked togther, as are both negatives. Now the pair of positive wires is connected to the positive output from the speed control, and the pair of negatives is connected to the negative output. The battery input wires from the speed control go to the battery pack just as with the series setup. The difference is that in the parallel setup, each motor "sees" the entire battery pack voltage, but the current drawn by each motor is added to that of the other, so that our two 15 amp motors would place a total load of 30 amps on the pack.

Which to use? If you have two motors that draw very low currents, which might well be the case with Speed 400's, you might want to run a parallel setup. For instance, two motors each drawing 10 amps would place a 20 amp load on the battery, which is not unreasonable in this example if you are using 2000 or 3000 mAh sub "C" cells, and each motor would "see" the full voltage of the pack. The advantage here is less weight, as you don't have to double up on the cell count to get full operating voltage to each motor. The disadvantage is that once you begin using bigger motors that draw current in the 20-30 amps range, running parallel means that you are really flogging the battery and won't get much duration...two or three minutes instead of six or seven, for instance.

Higher current motors demand that you use a series setup to avoid very short flight durations. This means that you will have to "double up" the battery pack cell count to get proper operating voltage to each motor, but this isn't as bad as it might seem at first. Let's say for instance that you have two Astro 15's that want to run on 12 cells each. Running them in series means that you need 24 cells, the equivalent of two packs of 12, to get the motors to run right. However, remember that you now have two motors to carry that load, so it all "comes out even".

As you work out plans for bigger models, you will eventually encounter a situation where the combined voltage of a "double" series battery pack will exceed the voltage rating of your speed control. For instance, using those two Astro 15's on 12 cells each, 24 cells total, won't work if you have a speed control rated for a maximum of twenty cells. You need a "bigger " speed control or an independent circuit setup. Eventually you will envision a model using motors big enough that there aren't any speed controls available that will handle the combined voltage...for instance, two Astro 40's on SuperBox gearing, running on 24 cells each, will require 48 cells, and no speed control that I am aware of on the model airplane market will handle that voltage.

As for the downthrust, my first thought is that you should not need it. As you know, the purpose of downthrust is to prevent unwanted pitch-up and/or climbing at high power settings. Classically, it was used in free flight models and simple R/C jobs with limited pitch and power control to allow the use of a lot of power without having the airplane climb uncontrollably. It is common now in designs like trainers that use combinations of airfoil and wing- tail incidence settings that contribute to very positive pitch stability; that is, the tendency for the model to return to level flight from a dive on its own. This same aerodynamic arrangement will make the model want to nose up as speed is increased (as in full throttle flight) if there is enough power. Since many, if not most, of our models are overpowered by the standards of equivalent fullscale aircraft, it is not surprising that they need some help to maintain nice controlled level flight.

Downthrust is one way of doing this. In fullscale airplanes with lots of power, where the tendency to climb at high power is also a possibility, it is customary for the pilot to re-trim the elevator (pitch) constantly during flight to maintain trim. (Check out info on high performance jet types, where the pitch trim is often controlled by a thumbwheel right on the stick so the pilot can retrim without taking his hand away !)

Back to your model...I'm going to make a few assumptions. First, your thrust line is very close to the center of lift and drag of the airplane; that is, pretty well lined up with the wing and fuselage centerlines in a side view as compared to something like a high wing model. This will minimize the effects of power changes on pitching up or down. If you are using an airfoil similar to that of the full size airplane, that is, a semi-symmetric rather than flat bottom, low speed section, the effect of speed changes will likewise be minimized. In addition to this, you are using relatively low output motors, and if the model is big enough overall to carry those motors along with their battery packs, radio, etc., and maintain a comfortably light wing loading, the amount of power you are working with relative to the size of the airplane won't be enough to cause pitch change problems in any event.

Does this give you enough to start on? If I have left questions unanswered, please don't hesitate to get back to me and ask again.

Hi Bob,

I have a kit of the Tiger Kitten not yet started. Can you suggest a power/prop/gearbox configuration using a Maxcim Neo13Y?

Regards,

George Carnie (Perth,Tasmania, Australia)

George,

Since I have not used a MaxCim motor in a 'Kitten myself, I don't have exact numbers to suggest, but I can get you pointed in the right direction. My airplanes have flown on geared Astro 05 and 15 motors as well as the Model Electronics (MEC) Turbo 10 motors....the Astro motors seemed to work best on props in the 11-9 range, and the MEC motors on their proprietary gearboxes ended up working best on 12-8's...in all cases the best props were the Master Airscrew Electric Series. MEC sells the MaxCim 15D motor under their label as the Turbo 10-20 and can match their adjustable ratio gearboxes to it; these gearboxes will also fit the 13Y. (I have such a combo in my 1/6 scale DH Moth running at a 4.3:1 gear ratio)

I would suggest that 12 cells behind the 13Y with an MEC gearbox turning aMaster Airscrew 12-8 or 12-10 would be the way to go. Contact "Pete" Peterson at MEC via their website at http://www.modelelectronicscorp.com, tell him I sent you, and ask him to suggest an appropriate gear ratio. He can sell you a gearbox that will screw right onto the front of your 13Y and allow you to experiment with different gear ratios if the first try isn't just right. I'm going to guess that the 13Y and 12 cells should end up turning the props I mentioned somewhere near 7000 RPM, maybe more...we are getting 6000 from 10 cells and the Turbo 10 ferrite motors an 12-8's.

Please let me know what you find out.

Bob,

I received a Four Star 40 for Xmas and am about to start it. Please advise on any lightening techniques. Also, would you please advise on motor/battery combos. I've heard that both the Astro 25G and 40G will perform quite well, but which one?

I also agree with your recommendation of New Creations. They've been a great help in my speed 400 aircraft.

Thanks,

Rene' Green
Tec-Ed Instructor, American River College, Sacramento , CA

Rene',

The approach I recommend for the Four Star is to replace all of the "light ply" EXCEPT the firewall and LE/TE station formers ,as well as the spar joiner and landing gear mount parts, with medium - light balsa of the same dimension (i.e.: replace 1/8" ply with 1/8 balsa). My practice has been not to make the lightening hole cutouts in the balsa...this leaves a somewhat more finished appearance with very little added weight.

Leave the above-mentioned light ply parts in the airplane as called for on the plan. You might fine-tune things a bit more by substituting "real" aircraft ply on dimension smaller than the light ply (i.e.: 3/32" AC ply in place of 1/8" light ply)...this would not result in a weight saving, but would provide better strength, at the expense of having to compensate parts fit for the change in material thickness. I would do this latter change only if you want to lavish a bit of extra effort on a really special model.

There isn't much else that needs to be changed. Mount the electric motor in place of the glow engine, keeping the thrust line and prop location the same, and adjust the firewall/motor mounting former as necessary to do this. I would suggest building in a removable thin ply battery tray in place of the fuel tank floor....usually this attaches to a pair of 1/4" sq. spruce rails running the length of the fuselage from F-1 to the wing trailing edge and mounts low enough in the fuselage that the motor battery can rest above it when the top cowl/front deck ahead of the canopy is made removable. The ply tray is fastened in place either by gluing it permanently or using several screws to hold it to the rails; this replaces the strength and rigidity of the fuselage that is lost by making the top into a hatch.

As an alternative, you can simplify all of this by eliminating the top hatch and accessing your battery by removing the wing, if you don't mind doing that every time you charge, etc.

I would suggest the Astro 25 on the standard gearbox, with 14 cells, as a good place to start. It is simple to add to the pack and run on 16 cells for a performance increase if you want to...the 25 will handle it fine. The 40 on 20 or 21 cells will give you more brute power, but the airplane will be significantly heavier.

If you kept the airplane really light, an geared Astro 15 on 12 or 14 cells would actually fly it well...one of my clubmates has a Midwest Starduster (very similar airplane to the 4-Star) set up that way and it flies nearly as well, though a bit slower, as my identical Starduster on a 25/16 cell setup.

If I were building the airplane for myself my choice would be a removable top hatch, geared 25 on 16 cells, light ply replacement as mentioned, and careful sanding overall for more weight savings.

Let me know how it works out.

Clay Newburn, currently living in northern Japan, wrote to ask about conversion of a plans - built Fieseler Storch from glow to electric power:

Clay,

I'm not familiar with the plan you are referring to, but I suspect that it is a Bob Holman offering. (It was) My best guess is that the structural design will be somewhat over-engineered to withstand the mess and vibration of glow/gas engine power, but that it would be very straightforward to make changes in material dimensions and trim away excess structure to produce a very reasonable electric powered airplane. I have attached a copy of the text of an article I published a few years ago which should give you some specific info not only on the TCraft but also on the design decisions that led up to my building it the way I did. What I would suggest for the Storch is that you treat it as a somewhat smaller airplane. The TCraft, as well as my friend Randy Smithhisler's 1/4 scale Piper models have wing areas in the 1600 to 1700 sq. in. range. I suspect that the 94" Storch will prove to have more like 1000 sq. inches of area. Many modelers make the error of looking at the overall bulk of a large model and assuming that a big engine (or motor) will be necessary to make it fly. If the wing area is indeed less than the apparent overall size suggests, what often results is an overpowered, overweight model. In the days when glow engines were our only choice for power, this happened all the time...especially a design with a fat fuselage and a wide cowl would suggest the need for a really big engine to turn a large enough prop to clear that cowl, with the end result being an overpowered, overweight airplane that was at best difficult to fly safely. Electric power allows us to solve the scale size prop problem by using belt or gear reduction, and we can concentrate on choosing a power source that works with the wing area we have to produce a wing loading and performance envelope that match the characteristics of the fullscale subject and provide a reasonable flying model. In the case of a 94" span Storch (I think this works out to 1/6 scale) with about 1000 sq. in. of area, my suggestion would be an Astro 40 on their SuperBox gearbox...this runs at a 3.1 to 1 ratio, and turns props on the 16" to 18" diameter range at very useful RPM's on 22-24 cells. I am flying an 1100 sq. in. area, 1/4 scale Bowers FlyBaby built from the Great Planes/DynaFlight kit using this setup...specifically, a sport wind Astro 40, SuperBox, 24 cells and an 18-10 prop. The model weighs 12.75 pounds (heavier than it needs to be, as I am using older full"C" size 2500 mAh cells) and I can take off effortlessly from rough grass and cruise easily at half power. You might want to look at http://www.scalemasters.org and check out the section on electric powered scale models for a photo of this model. I would suggest that you go ahead and buy the plans, then make some decisions about the best way to do some weight reduction. Let me know what the actual wing area is, and I can help you fine tune your approach to building the airplane for electric power.

Bob,

I've had this burning need to build an e-powered scale aerobatics model even before reading your article in Jan 2001 MAN. And Bob Banka mentioned on the phone that I should give you a call for your comments on this possible Sukhoi e-project. I have this well used Goldberg Sukhoi spec'ed at: 72.5 inch span, 950 sq. inches, 8.75 to 9.5 lbs, for 120 size 4 stroke. Wing-loading: (9.5 x 16 ) / (950/144) = 23 oz/ ft2 .

My plan is to strip all covering off the relic and try to retro-lighten the structure as much as possible. I am technically capable. I've scratch built 3 models (my most recent, Santich's 101" P-51 Mustang, honestly surprised me at the Canadian Nationals 2000; it placed 1st in standoff scale). I experimented with e-power 15 years ago with an Astro ferrite 05 on a Drifter II. Wonderful memories. My day job involves radar and control electronics and I am delighted that e-power has advanced so much. I am squirming with anticipation to try out a brushless motor. Got one you want to sell cheap? Just kidding. But I have to try brushless just to check out the technology. Based on your article, and with 2 lb. estimated additional weight (21%) to the Sukhoi, here are the calculations:

Wing-loading: at 11.5 pounds would be: 27.9 oz/ ft2. For a 72" span, this is probably OK? It won't be a floater.

Power loading and motor power rating: at 60 watts per pound: 60 x 11.5 = 690 W. 60 W / lb. will give satisfactory flight...at 70 watts per pound: 70 x 11.5 = 805 W. 70 W / lb. will give some vertical performance. I chose this.

Choosing the number of cells and motor (using the recommended 25 amp battery draw): at 25 amps and 805 watts, the voltage must be 805/25 = 32.2 total volts at 1.2 volts per cell, the number of cells = 32.2/1.2 = 26.8 or 27 cells

Aveox Brushless Motors, Specs and Selection Chart downloaded from aveox.com indicates the following motor is appropriate: 1412/4 geared 3.7:1 30 cells and a 16x8 prop should deliver 118 oz thrust with 24 amp battery draw.

Batteries, overall weight estimates, and a charger: 30 RC2400 Sanyo cells would weigh 3.7 lbs. Aveox 1412 Motor/gear weighs 0.8 lbs. Total = 4.5 lbs. YS 120 with tuned pipe, tank, and accessories would be at least 2.3 lbs. 4.5 lbs. - 2.3 lbs. = 2.2 lbs. This is very close to my 2 pounds overweight estimate.

Astroflight 112D 36-cell charger looks good for the application. Any other recommendations?

Flying time: 2400mAH = 2.4 AH and the Battery will be delivering 24 amps. Therefore: Flat out flying minutes = 2.4AH/24 A x 60 = 6 minutes. Expect 8 -10 ? with good throttle management.

Gearbox questions: I've never used a gearbox. Does the gearbox take the damage and spare the motor in case of a severe mishap? Aveox specs their motors without gearbox at roughly 14,000 RPM. Any idea what the prop RPM will be with gearbox? The max RPM of a 1412 is spec'd at 40,000 so it won't be more than 40,000 / 3.7 = 10,810 RPM (I think).

Am I on the right track with this Sukhoi or do you think it might be a dirty dog that flies like a brick? Appreciate any comments/corrections, especially a recommendation for a better brushless motor or gearbox type if I am off base with the Aveox geared 3.7:1. Thanks.

Don Beatch, Victoria BC

Don,

An interesting project...based on what you are telling me, I think you can make it work. You will almost certainly end up with a good flying airplane with aerobatic capability that will be sufficient to justify the project, although perhaps not quite as "sparkling" as what you would have had with the glow engine. I suspect you have already figured this out.

My first response when reading your comment about converting an existing glow powered model was "oh no, another flying brick". However, reading your comments, I think you understand what you are doing and will be able to get the model down to an acceptable weight. There is no doubt that you would be able to save an additional half pound to perhaps a full pound by starting fresh and doing things like replacing "light ply" with balsa, etc., but I also understand the challenge of restoring an existing model that is too good to toss out. (Usually called "feeling sorry for it!")

Your loading and power numbers seem pretty good; the only possible "hole" being the use of a full 1.2 volts per cell. I generally use 1.1 owing to the habit of NiCd's delivering less than full rated voltage under heavy load; some e-fliers calculate on the basis of 1.0 v/cell. Nonetheless, the Aveox motor you have selected is rated at 30 cells, and this puts you right back in the park.

Re. the gearbox...I've never considered a gearbox to be a "motor saver", but it might function that way. My big question is, "which gearbox are they talking about?" Some of the Aveox motors use their own proprietary gearboxes; others are sold for use with Tom Hunt's (ModelairTech) belt drive units. These are a bit bulkier than gearboxes, but work very well and offer the added advantage of an adjustable reduction ratio. I would have no hesitation about using one in your Sukhoi. Not sure about RPM's...The 40,000 figure is based on light loads, etc.; I suspect that you would end up turning a 16-8 in the 5000 - 7000 range, maybe a bit better. The 16-8 is a lot of prop, and may surprise you at how much it will pull.

The Astro 112D charger is a winner...I have several of them.

Another rather different approach would be to use a standard wind Astro 40 and Astro's Superbox (3.1 - 1) gearbox on 24 cells...this will turn an 18-10 at around 5000 RPM. This sounds like it might not be enough; however, remember that you will save some weight using 24 cells rather than 30. The Astro 40/gearbox combo will be a few ounces heavier (I think) than the Aveox/belt drive. This approach should give you a lighter weight, and pretty good performance in a lower speed range closer to actual "scale speed". You have to experience the effect of the really big (18-10 or perhaps 18-12) prop to appreciate how much it pulls. I am flying this particular combination in a 1/4 scale Great Planes/DynaFlite FlyBaby that is somewhat larger than your Sukhoi...I'm at 84" span and 12.75 pounds (heavier than necessary with older, 3-ounce cells), and the model does clean basic aerobatics and cruises clean at half power. Current draw is in the same (mid 20's) amp range) as the Aveox advertises, so duration would be comparable. I suspect that the same power system might work pretty well in the Sukhoi. It is my understanding that the brushed cobalt motor (Astro) is not quite as efficient as the Aveox, but it would be somewhat less expensive and I have no doubt that it would fly the airplane safely. You might want to use something like a 16-10 or 16-12 with the Astro set-up...loads on the motor would be about the same and the smaller, "faster" prop would work better with the Sukhoi than the 18" job I'm using on the big fat FlyBaby.

Bottom line...will it work? If you can keep the weight as spec'd, it will most certainly fly, and the aerobatics should be at least OK. The combo of an Aveox motor and especially a ModelairTech belt drive should allow you A LOT of latitude for testing different cell count - reduction ratio – prop combinations, and this effort might well change a so-so model into a winner after you first get it flying. The other possibility is that you will do the conversion, get an OK airplane, and then see so much potential in it that you build another new one with all possible weight savings, etc., and an optimized power system.

I'd try it.

Hi Bob,

Read your article in S&E Modeler ,Jan 2001 and a thought came into my mind about electrifying the 1/4 scale Hanger 9 Cub. I have a MaxCim motor with a large ratio reduction gear that they told me to use with 25 cells and a 20 x 10 inch prop using their electronic motor control. I am new to electric flying and I need all the help I can get.

I would appreciate any comments you may have.

Thank you,

Frank Capan

By the way, how is your cat doing? I enjoyed seeing it in your tape.

Frank,

I don't have any direct experience with the Hangar 9 Cub, but I suspect that you will be able to make it work fine with the MaxCim motor set-up you are describing. The experience my friend Randy Smithhisler and I have had with quite a few 1/4 scale lightplanes, Cubs among them, suggests that if you can keep the total weight under 18-19 pounds, which should be no trouble at all with that 25 cell pack, your wing loading will be very comfortable. If you can get 4500 RPM from the MaxCim - gearbox combo turning a 20-10 you'll be OK. I am flying my TOP GUN Taylorcraft, which weighs 23 pounds, using an 18-12 prop that my Astro motor and gearbox combo turns at 5000 RPM, and I have power to spare. You might want to try an 18-12 along with the 20-10 and see which works best.

My cats are keeping me busy making sure I keep the work area full of interesting little things for them to play with! I can't be sure which of them you remember seeing...the brown tiger cat, Jenny, passed away a few years ago of kidney failure, but the little orange tabby, Katerina, who did the bit on my shoulder in the video, is fine, sitting right here on the scanner beside my keyboard, waiting for a chance to crawl over and get some more attention.

Let me know how you make out with the Cub.