I will be building a Dynaflite (Craft Air ) Rearwin Speedster over the winter.

The plane is designed for 35 - 40 2 stroke or 45 - 65 4 stroke. Wingspan 60", length 42", area 590, weight per "the box" 4 3/4 lbs - 6 1/2 lbs.

I "guesstimate" I will be coming in somewhere between 65 - 75 oz without motor, ESC or battery, but including servos.

I am still pretty much a "newbie" with electrics.

The motor that peaks my interest for this conversion is:

http://cgi.ebay.com/ws/eBayISAPI.dll...2131&rd=1&rd=1

With 1300 watts of power available, I shouldn't even have to bother with the wings however I am concerned about using a 3s lipo AND 30 amp ESC (as recommended by the manufacturer ).

Does a 3s lipo and this ESC along with a 13" prop seem adequate/safe to use with this motor and plane ? I need to find out prior to starting construction so I can locate the firewall in the correct location.

Thanks

I would not recommend using eBay to purchase R/C products from an unknown vendor. If the unexpected shipping costs don't get you, the invalid claims or specs will. Further, who will you contact when a problem arises?

In this case, the so-called 1300 watt motor is matched with a 30-amp (non OPTO) ESC that can only accept up to a 3-cell LiPo pack. Let's do some numbers.

A good LiPo cell produces 3.6v under load. Multiply 3.6 * 3 cells to get 10.8v under load. To determine the current needed for a 1300 watt power level, use P = I*E or I = P/E or 1300w/10.8 = 120amps. Obviously 120 amps is not a good fit for a 30-amp ESC.

For a good start, read my [link=http://www.gregcovey.com/Glow_Conversions_Made_Easy.htm]Glow Conversions Made Easy[/link] write-up and determine just how much power you really need.

Then, go to Hobby Lobby and select a [link=http://www.hobby-lobby.com/brushless-motors.htm]Brushless Motor Combo[/link] that you will be happy with.

Good luck!

Campy,

I have to agree with Greg 100%. I have followed his conversions since the beginning, and he has some very nice plane that are totally sucessful.
First of all, if you are converting a plane that will weigh lets say around 6 or 6.5 pounds with glow, you can expect it to be lighter using e-power. Especially in this size, it seems to be in the range that really benefits from going electric.
Second, for spirited sport flying you will only need 130 to 150 watts per pound, for a total of 900 watts at the most. Unless you are going to 3D this plane, that will be very sufficient.
Third, Greg is right about going to Hobby-Lobby for your conversion items. What I generally do when choosing a motor is to pick one that the weight of my plane will fall into the lighter end of the range given for it. If a motor will fly a 75 to 100 oz plane, then it should fly your with great authority.
Just my opinion,
Darrell

Campy,

Greg's advice is good.

OK, it is off to Hobby-Lobby for me.