Fun Cub

[trebor]

Hope someone can guide me, I know there are hundreds of threads on Multiplex Fun Cub and plenty of motor size guides to refer to. As I,m new to this hobby its a struggle to get my head round it. The Manufacturers advise quite large heavy motors and there`s plenty of people having to make sliding trays for battery`s to slide back into fuselage or sticking heavy weights in the back to get correct CG.

When I try to work out the size of motor its nowhere near the recommended. Here is the model speck **LINK**

The recommended motor C3516-840w at 134grams, Tuned version C3522-0990w at 162grams.

When I work it out it comes to less than 300w motor required, am I doing something wrong.

[Chris Bott - Moderator]

Trebor a quick look the spec of the first motor you list shows this:-

Motors in the 350 Watt class, suitable for 3-D model aircraft weighing about 900 g to 1300 g, for aerobatic models up to 1600 g, and trainers up to about 2000 g. Also good for gliders. Himax C 3516-1350.

Typical operating data:
2S LiPo / 12" x 6" prop: current drain: approx. 49.0 A
2S LiPo / 11" x 7" prop: current drain: approx. 43.0 A

Rpm/v - 1350

So I'd suggest that it's designed for a 2S LiPo and around 300-350W

[Chris Bott - Moderator]

Actually, the one for the Fun cub might be a 840Kv version, so better for 3S LiPo. But still only a 300-350W motor

[John Lee]

I think you may be confusing the "-840w" in the motor name as indicating that it will produce 840 watts. That's not the case. The spec of the motor is working range 10 - 26 amps on 3 or 4s batteries, ie about 120 - 420 watts, with a max of 37 amps for 15 seconds @ about 600 watts.

300 watts sounds about right for the Funcub.

Mine is absolutely stock with recommended motor and the CG is spot on with no adjustments or ballast. In fact I have 8 Multiplex foam models, some over 7 years old, and all are completely standard, the designers & developers know what they are doing.

[Pete B]

This is the spec for the standard motor. It mentions 33A on a 12x8 prop on 3S. 33A x 11.1V = 366W, which should be plenty

Having said that, that is an eye-watering price. I would think this 3542/1000 would make a fair alternative. There must be some FunCub owners out there who can advise?

Pete

[trebor]

Being in the Gas trade for years this "Sparky Millarky" is like going back to school You lot make it look easy.

[trebor]

Posted by John Lee on 12/02/2015 10:28:01:

I think you may be confusing the "-840w" in the motor name as indicating that it will produce 840 watts. That's not the case. The spec of the motor is working range 10 - 26 amps on 3 or 4s batteries, ie about 120 - 420 watts, with a max of 37 amps for 15 seconds @ about 600 watts.

300 watts sounds about right for the Funcub.

Mine is absolutely stock with recommended motor and the CG is spot on with no adjustments or ballast. In fact I have 8 Multiplex foam models, some over 7 years old, and all are completely standard, the designers & developers know what they are doing.

What size prop are you using ?

[J Moyler]

4-Max has a lot of useful information Link.

4-Max recommend a 400W Motor with a 11x6 motor, weighing 107g Link

I have brought motors and other items from 4-Max and can recommend them.

Hope you find this helpful

JM

[Geoff Hoolahan]

Trebor, I got the 'factory built' Receiver Ready version over a year ago.

As I recall, it came with the C3516-0840 motor (840 Kv) and a 13x4 prop.

ESC is Multiplex 30A. I use the same 3s 2200mah batteries that I use in my Wot4 Foam-E.

I haven't used a Watt meter on it, or if I did I didn't make a note of the numbers.

As John Lee says - this setup works fine and it's one of my my favourite planes.

[trebor]

Will it vertically hover with that set up ?

[Geoff S]

I bought the power system for my Fun Cub from 4-Max, like JM, above. Can't remember exactly what the motor is and the model is up in the loft in its winter quarters, but I know their recommendation was spot on. They sell beautiful wooden electric props too which perhaps helps the performance. The battery is on the CoG - see below.

The main problem with the Fun Cub is battery security. I was relying on Velcro pads (no strap) and the battery decided it didn't like where it was half way through a bunt and headed downwards. I wondered why the Cub stayed inverted as it floated gently to earth and landed upside down Almost no damage except for the missing cowl and battery. Funnily enough someone found the cowl a few days later after I'd bought a replacement but the battery is long gone. Batteries are now better secured!

Geoff

[John Lee]

Like Geoff H I use the recommended 13x4 prop. No it won't hover, but for me that's not the point of this model.

Edited By John Lee on 12/02/2015 11:47:05

[Tim C]

Trebor, as.a funcub owner and plenty in my club as well. I would recommend a 3536 1000kv motor ad ideal, a 3542 will work, but it is heavier and depending on your batteries , they will be well back to balance, more so if you using 2200 batteries, I use 3000 3s mainly. Make sure you get the shaft the right way, I put the details in your other thread

[Geoff Hoolahan]

Just connected the watt meter to my Fun Cub setup described above.

with a 3s 2200mah battery at 88% of charge:

Max was 160 watts drawing about 16 amps.

probably a bit low for a 2 1/2 lb model.

maybe some 'Sparky' can confirm that is about the right 'milarky'.

[trebor]

Had to pop out for bit`s n bob`s Basingstoke is too close to me

Had a chat with George at 4Max and came back with some gear. The motor is 3536-1100 kv. 525w. Speed controller 45amp, 11x5 prop. Battery`s are 3s 11.1v- 2200mah. Do you think I can experiment with the prop sizes ? Now I`ve got to hide the box somewhere

Edited By trebor on 12/02/2015 13:54:28

[Dave Hopkin]

525W on 4S so prolly about 400W ish on 3S 2.5lb model that 80W per Lb sounds about right.... play around with the props and you might be able to drop it down to a little less and prolong flying times.....

[Chris Bott - Moderator]

Yes you can experiment with prop sizes trebor, but if you want to keep from damaging the Motor, ESC or battery, you'll need one of these. Or something similar.

4-max budget wattmeter Good job he's not far away

[trebor]

Yes I did get a watt meter, first problem is the alloy motor mount. I was told that a bit of filing would cure this but its not the case. It will only mount on 2 points. What to do, make a new bracket, change the motor, try using some low temp alloy weld rod to build up lugs for the 2 other holes but not sure on the quality of bracket alloy.

[Caveman]

Trebor, I've had my Fun Cub for a year or two now. It's a great plane to get out of the car and fly at a moment's notice.

I know you've already parted with hard cash, but since you asked the question ...... mine is powered by this motor

**LINK**

380 Watts on 3S on an 11x7 APC-E prop, and the holes in the motor align perfectly with the alloy motor mount, so no alteration needed. The only downside is that the motor shaft needs to be reversed. Not difficult to do but it may not be something you fancy doing.

In that case one of these would fit straight onto the mount

**LINK**

Around 360 Watts on 3S on an 11x5.5 APC-E prop.

Hope you get it sorted GDB

PS Need any other help, let us know!

I can't tell you if it prop hangs as I've never tried, and as John Lee says it's not really that type of plane.

[trebor]

I only asked about the prop hanging to give me some idea of power required.

[Caveman]

Trebor, just another thing to consider, the motor is screwed to the alloy mount such that the motor wires exit at the front of the motor.

In order to ensure that the wires do not come into contact with the spinning can of the motor, I cut a hole between the motor housing area and the air intake below, and fed the wires through.

Above is a sketch, and below a photo. Hope you can see the wires clearly.

Ignore the 'crocodile skin' look of the foam, this plane has had an interesting life, including treatment with hot water to, almost, restore the shape of the nose!!

Despite its many crashes, cartwheels and other similar prangs it still flies perfectly.

GDB

[Caveman]

Trebor

Just seen your post about the power required - with 360 to 380 Watts the plane will climb very rapidly and it will take off in about 3 feet (especially with flaps deployed).

Flown in a sedate fashion will stay aloft for around 20 mins on a 2200 3S battery. Flown 'enthusiastically' 8 to 10 mins is the norm.

GDB

[trebor]

That's a good tip with the wiring, I think I will take my time putting it together. Been advised to make a tube of fibreglass matting soaked in super glue to reinforce nose section inside or I might insert a balsa / thin ply platform down the centre for things to fix on from under the motor to the rear of canopy compartment.

[i12fly]

305W on my Fun Cub using a 10x5 prop, climbs vertical as far as I can see it, not really enough power to prop hang though.

Fit the flaps, they are fun, mine needs a bit of coupled down elevator though when flaps deployed.

I fitted a thin ply floor in the rear part of the hatch area and extended it into the space under the wing. The battery is pushed back as far as possible but still accessible and I still needed 2oz of lead at the tail. It handles wind well in the air but don't try any cross wind take offs and straighten it up into wind on touch down.