How to electrify the sport duck?

billromo
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How to electrify the sport duck?
« on: July 05, 2010, 10:02:45 AM »

I am dying to order the Sport Duck, but I want to go electric, please help. Thanx.

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Re: How to electrify the sport duck?
« Reply #1 on: July 12, 2010, 02:38:59 PM »

Hi Bill,

I'm sorry for the delayed response, I hadn't checked the forums in several days. If you are ever waiting for a response here too long just shoot me an email directly at mudduck@optonline.net.

Thanks for your interest in the Mud Duck Sport. I am sorry for the lack of information on the electric power recommendations on the website; I have planning a website overhaul and was going to add it then.

Personally, I am using an AXI 4120-14 with a Jetti Opto70 ESC and 4s Lipo's (4000 mAh = ~8-9 minutes) turning an eAPC 14x8 prop on my current demonstration Mud Duck Sport. This is a much more powerful set up than is necessary, others have flown on far less. I use it for two reasons: #1 - I had the set up from an abandoned project, #2 the Sport that it is currently on is over 11#; built "stock" it should only be 7.5 to 8 pounds, and even though it is around 4 pounds (50%) overweight there is still plenty of power for it.

Depending on what you plan to build from (e.g. plans or kit). If you were to build from a kit you can build the kit “stock” from foamboard or you can use the foamboard parts as templates to cut out another "kit" of foam parts from FFF or Depron if you wanted to build an even lighter version (right from the start or later on). If you are going to build from plans then you can make that decision from the start.

Like any other plane the Duck will fly even slower and longer if it is built lighter (but keep in mind that in windy conditions it is more susceptible to wind than a "stock" weighted version). Foamboard itself is about 3 times the weight of FFF and Depron. If you opted to use a lighter material it would result in an airframe almost half the weight (the other materials [e.g. lightply, balsa, etc] will still weigh the same obviously).

Foamboard is clearly the strongest, smoothest finish, and straightest to work with when building and those are good qualities. FFF is pretty resilient material and since the mass is so much less in a FFF version, they fair pretty well in a minor to moderate crash and they are much lighter resulting in a better flying airframe and better battery run times.

The biggest drawback to the FFF is the poor surface finish, but hey... it doesn't look so bad up in the air. Finally Depron, or it's clones, provide the light weight and the nice finish, but is less tolerant of damage. Crashes are not as bad as you would expect because of the low mass, it doesn't have enough energy to hurt itself too bad, but "hangar rash" from moving and storing with kill long before a flight will.

Below are some inexpensive power systems components I pointed a customer to based on positive results from other customers. It is copied directly from an email:

"Here are a couple suggestions of cheap motor/battery/ESC set up I have a couple customers using on their "Sport" models. Now this is as much power as you will need, you may be able to find cheaper alternatives at the same level or step down a level in motor or battery to save more, but with every level you drop you will reduce either your flight time or max power. You will be flying this fairly lazy-like and a lot of power isn’t critical on the other hand, you don’t want to under-power it so much that it is flying near max amp draw the whole time or you will destroy your batteries and or motor from overheating. Remember, this is just a suggestion with some direct links, you can use the information about these items and shop for similar gear elsewhere or within the same stores (they tend to be pretty cheap):

Motor:

BP A4120-7 Brushless: http://www.bphobbies.com/view.asp?id=V450327&pid=B2171400
Or
TURNIGY 50-55B 600kv Outrunner: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4907&Product_Name=TURNIGY__50-55B_600kv_Outrunner_(Eq.4120/14)

ESC:

TURNIGY Plush 60amp: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=2166&Product_Name=TURNIGY_Plush_60amp_Speed_Controller
Or: TURNIGY Sentry 60amp: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=3730&Product_Name=TURNIGY_Sentry_60amp_Speed_Controller

Batteries:
Rhino 4000mAh 4S2P 25C http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7656&Product_Name=Rhino_4000mAh_4S2P_25C_Lipoly_Pack (just right)
Rhino 3700mAh 5S1P 20C http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7652&Product_Name=Rhino_3700mAh_5S1P_20C_Lipoly_Pack (more Power)
ZIPPY Flightmax 5000mAh 4S1P 20C http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8580&Product_Name=ZIPPY_Flightmax_5000mAh_4S1P_20C_ (more flight time)
You will probably be satisfied with a 4s pack, but if you want more power you can upgrade to a 5s or 6s pack. You can add more mAh as you can afford for better flight times, 4000 mAh seems the minimum most people are content with.

Props: Your prop will be more dependent on the power set up combo you choose. An example would be: If you went with either motor above, and a 4s LiPo, I would recommend a 13x10 or 14x8 APC e-prop."

Keep in mind there are a lot of variables that will affect your final power system choices. I will be happy to assist you in fine-tuning those choices.

BUILDING FOR ELECTRIC
Besides choosing lighter material to make a lighter airframe (which isn’t necessary, many fly in the original “stock” configuration/materials) You have some options of where and how to mount your electric set up.

If you are building from plans, making mods to the fuselage are very simple. If you are building from a kit where the fuselage parts are pre-cut your modification choice can be from simple to more complex depending on your preference and skill set.

Firewall

First, are you going with an electric motor that is normally mounted with a horizontal mount (e.g. some inrunners and nearly all brushed motors) or are you going to going with an outrunner or radially mounted (vertically) inrunner? If your motor requires/suggests a horizontal mounting method (like a direct replacement for a glow engine) then you can build the nose of the Duck completely stock and it is pretty strait forward.

If you are using a motor best (or most easily) mounted vertically as 95% of today’s motors are, you can either still build the nose “stock” and use an aftermarket motor mount/extension to bolt the motor to and it to the stock mount. You can also make up your own very simple mount using a couple pieces of aluminum bent 90 degrees. The motor need not be on the same line as a glow motor would be (sometimes referred to as the “datum” line) as long as it is parallel with it. The flight characteristics change very slightly but not enough that it is noticeable if you are only off by an inch or so.

To reduce weight and make a “cleaner” looking installation some builders build a vertical firewall instead of the horizontal engine mount. This can be accomplished in two general ways: add material over the “chin” so the fuselage slopes out to the very front equally on top and bottom and add a vertical light-ply (1/4” thick) firewall to mount your motor to; OR, cut off the “Chin” that juts out so it is flush with where the top of the fuselage ends (going forward), and then install the same (but larger) firewall.

Since the nose is a little short on the Ducks, and electric set up can ultimately be a little lighter and instead of adding nose weight to achieve balance (if it is even necessary) some builders decide to build the nose out rather than trim it back, although I haven’t heard any regrets from the group that “cut off the chin”. There is one only one very important step in either case, make sure that the vertical firewall is 90 degrees to the “stock” engine mount, do not use the “upright” cut (or line on the plans) as a reference to build the firewall parallel to; this line is “raked back” some and not 90 degrees to the thrust line. As for building in right-thrust, that is your choice, your motor can always be shimmed. I would not build in any more than 2-3 degrees of right thrust for this reason: if you ever decide to change motors and go to a smaller motor you will have more right thrust than you need (rule of thumb: 40-size equivalent like 2-3 degrees, 60+ equivalent likes 4-5 degrees).

If you are building from plans or going to use your kit as templates for lighter materials, you can see that pushing the nose out further is not difficult to do, if you are building the foamboard kit you can more easily cut off the chin than build up the nose. The decision is entirely up to you.

Cabin
The only other consideration to modify your Duck for flying electric is the internal compartments and cooling. The batteries are typically long; longer than the fuel tank compartment that is provided. I simply just stretch the fuel compartment floor back to accommodate the batteries I plan on using (you can grossly over estimate this measurement, there is tons of space in there). Instead of installing the back panel of the fuel compartment just install a crossbrace of foamboard across the top portion to keep the fuselage sides from flexing but leave enough room around it for air to flow around it.

Now for cooling, allow for an opening to flow over the batteries and ESC if mounted internally (I leave my ESC hanging in the breeze with the motor). Channel the air over the ESC/batteries and choose an exit area of your choice anywhere, but remember to make the outlet opening at least twice the size as the inlet.

Gregory Drusjack
Owner
Mud Duck Aviation, Inc.
www.mudduckaviation.com

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Re: How to electrify the sport duck?
« Reply #2 on: July 13, 2010, 01:01:19 PM »

The images I provided must have been lost when I moved this topic from the other board. I have attached an image of the simple aluminum brackets that I made in a pinch, and four images of a similar method done using light ply.

You can also purchase and use mounts like these that I recently picked up to illustrate how they can be used with the stock mount as well (photos to come illustrating the method):

http://www.hobby-lobby.com/aluminum_motor_mount_for_axi_41_series_brushless_motors_1365_prd1.htm
http://www.hobby-lobby.com/mount_for_.40_.60_size_outrunner_motors_174_prd1.htm

Using these mounts you would only need one side and the face to create a 90 degree upright and use the installed side to mount to the horizontal (ply) mount. There will be a little flex but it won't affect performance.

Greg

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How to electrify the sport duck?