John,

In general, the watts per pound rule is a good starting point, but you also need to consider a few other things as Sam mentioned.

One of them, is keeping the current within reasonable levels. Although I have two 60 amp planes, most of my fleet is proped for about 40 amps, give or take. The reason for doing this is simply to keep pack size manageable as well as the amount of heat generated.

Something else to consider is propeller diameter. For the Mini-Plane, I am planning on using at least a 13" prop, preferably a 14" prop. The reason for wanting to do this is thrust (a large prop can generate a lot of thrust without having the plane be Mach 2 capable, ie. think of a helicopter). Being a biplane, the Mini will be draggy and I would like to use a bigger prop to offset the drag. In order to get the pitch speed I want (about 60 mph in this case) I will probably use a prop with a 10" or 12" pitch. To do this, I will need about 600 watts or so, so a 5S pack at 35 amps will do the trick. To accomplish this, I will use a geared motor with an effective Kv of about 425.

For this plane, I might use a Mega 1625/3 geared 4/1 (600 watt system) or a Mega 2220/3 geared 4/1 (900 watt system). I have not decided yet.

You plane is looking good. As soon as I get a chance, I will post some of mine.

Teo

Many, many moons ago, I leaned to fly on a three channel Sig Kadet and the next year, my second plane was a Sig Smith Miniplane. So, I went from a three channel trike gear trainer to a 4 channel tail draggin' bipe. This tells you what a great flying bipe the Sig Smith Miniplane is! Mine was powered with a ST 40 and I wish that I had never sold it...like a LOT of my planes...

Jake

Hi teo
Neat idea about using a gearbox - still wish I hadn't sold my 'collection' of MEC Superboxes. Can't beat a big prop, like you describe.

Which make of gearbox are you planning on using?

Regards

Dereck

Teo,

Thanks and yes I do agree with your info you gave. I use all the same logic when building from kits or scratch building others.

Here's what I have so far, I have the battery box made(2 4cell 3000's) and now since its all together i will put it on the balancer and figure the placement for the servo's to help in the CG.

Cheers,

John

Hello guys,

I just logged into rcgroups for the first time in a few days so my apologies for a tardy reply.

John,

You plane looks really good. I am assuming that you will be running a 4 cell pack and not an 8 cell pack. It should be plenty of power. Either way, you are way ahead of me. I am just about done with the wood part of the structure but still have some soldering to do.

Dereck,

The gearbox in either case will be a MEC. For the Mega 2220/3 it is geared at 4:1 while the one for the 1625/3 is geared 3.8:1. In total, I have four of Pete's gearboxes, 3 regular ones and a mini which is hooked up to another Mega, in this case a 1615/4. I really liked his gearboxes because it allowed me to fine tune the kv of the power system to what the plane needed. I was sad to see him retire.

Cheers,

Teo

Hello,

I have enclosed a couple of photos of the Miniplane in its current state. The structure is mostly done; I just need to add the rails that support the wing mounted aileron servos.

As it stands, the structure currently weighs 2 lbs, including the landing gear wire and two HS 225 servos. If you look carefully, you should be able to spot the elevator and rudder servos which have been temporarily mounted on the fuselage. I will use a CF pushrod for the elevator and pull-pull cables for the rudder.

Teo

Any updates on this project?

Teo,

Hope the build is going as planned. I "Flew" mine not long ago, it had the perfect amount of power(more than I thought) and it was flying great, until the left aileron servo stopped working in the up position and that was it and in she went, hard. It sucks but for the short flight time it was a great flyer.

Cheers,

John