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Finding balsa trainer

Tench745

Well-known member
#2
I have not built or worked with that particular kit, but I believe there is a build thread for it somewhere on this forum. If memory serves, the plane is somewhat heavy and the build instructions are not super clear. Others will chime in on kit suggestions, I'm sure. In the meantime, peruse the "Balsa Builders and Breakers" section of this forum for some inspiration.

Edit: I did a little looking and the thread I was thinking of was about the older, smaller Hobbyking J-3 Cub.
 
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Bricks

Well-known member
#4
Unless YOU REALLY want to build for the price of that kit you can buy a plug and play plane, trainer from either a swap meet or local Book of Faces market place for either less then that or not much more. Last trainer I bought complete OS Max 40 IC engine, install my receiver bind and go fly was $40 and it looked like it has never been flown.
 
#6
@Merv that plane looks good but the winspan is really too small + it's only 3ch so it's going to get blown away when there's wind... Back to my first idea, the Kadet Mk II. The manufacturer provides lots of info about their model but they only recommend an engine and no electric motors. Do you guys know if this model is easily buildable with such a motor and most importantly which specs said motor should meet ?
 

Ryan O.

Well-known member
#8
Hi, I'd like to get myself a balsa plane that'd be easy to fly. I only had one plane(FT scout) and one glider in the past. And I found this balsa kit on hobbyking. Is it fliable for a beginner ? If not do you have any recommendations for any kits ?
If you are looking for a first Balsa build, the normal Stick 40, Kadet, Avistar, etc. are all great trainers. If you really want a cub, then I'd recommend the SIG Cub over the Hobbyking one, from what I've heard. What I've been told is the Hobbyking kits can be harder to get parts for, and instructions can be hard. If you get a Cub, it needs rudder to fly, and the FT Simple Cub is a good Cub to teach that on, and is a high wing. That'll teach you how to fly most 40 sized trainers. However, both of these are relatively large, and I think a 1500mm build is better for a first balsa plane, not too small, so it flies well and any extra glue usage (which is to be expected from a first build) won't make it too heavy. 1800mm planes can be a little less maneuverable, and unweildy. You can also get a smaller Balsa kit if you are more conservative with the CA, but I wouldn't go too small. I've also looked on ebay, and this may be a good kit too. It's similar to a Telemaster, which is a great plane, I have a mini telemaster and it flies easier than the Simple Scout IMO. This plane is about the same size as my mini telemaster, 1meter, so it is a little more vulnerable to wind than the 1.5meter trainers I listed before. The Mini Telemaster I have is kind of fragile, after on unfortunate crash where the wheel caught a rutt it cartwheeled and now I have to replace several parts. The HERR Cloud Ranger appears to have a simplified construction and looks more durable. It looks nice, and I may get one myself soon. Plus, it has a long nose so any extra glue weight is easy to cancel out by shifting the battery. The bigest benifit I see in the Cloud Ranger is the simplicity and low cost. It should use a motor about the size of the power pack B, but with an 8 inch slow fly prop.
https://www.ebay.com/itm/HERR-Cloud...731407&hash=item441d437081:g:UDoAAOSwZVJa63Mn
As for covering, I like Ultracote over Monokote, but both work well for their price. A perk of Ultracote is that it smells less, which isn't much of a perk. If you plan on crashing, I'd get ultra trim as well, which is ultracote that is sticky before being heated, that way patching is easier.
 
#9
@Merv ty but these are engine specs isn't it ? I'd prefer to use an eletric brushless motor because I'm more familiar with that. What would be the specs of an equivalent brushless motor for that plane pls ?
 
#10
About the Hobbyking kits, at least for a beginner, avoid at all costs. In the fitment and wood quality department they're turds. Some people do seem to have positive experiences with them, but most feedback I see seems pretty negative. Same for Banggood or pretty much anything Chinese that's sold on ebay. Same story, if not even worse.

The Kadet II is a good plane. Sig kits are generally well made and will go together with little fuss if the instructions are closely followed. Specifically, it's a pretty simple sheeted fuselage and flat bottom airfoil airplane which really doesn't require much in the way of weird tools or complicated jigs to build, all good qualities for a first balsa build.

Generally, all originally nitro airplanes can be converted to electric successfully with a little bit of redesigning and elbow grease; how much of that is required is determined by the design of the airplane. Often it's as simple as just adding an extension ("motor box") to the firewall to bring the propeller forward to where it would sit when mounted to an engine, and sometimes adding an extra hatch to make changing out batteries less work. For the required motor... let's do a little math. It says on Sig's site that the flying weight of the finished airplane should be 5 pounds. Generally a good rule of thumb for a trainer for power output of a motor would be about 100 watts per pound of airplane. This gives you the ability to easily fly throttled back while still having some reserve power in your pocket should you need it. These kinds of airplanes can fly on much less power; I had one like this, not the exact model, but I used a datalogger and the math revealed I could maintain level flight on about 40 watts per pound; however if that was the maximum power of my engine, if I got in a situation where I needed more power, bad things would happen. If you used a 25 glow, which a power estimate for a decent sport engine in that category being maybe 350 watts, it equates to about 70 watts per pound, and I would not go lower than this. So, if we take into account the upper bound of our desired power range being 100 watts per pound for an airplane which weighs 5 pounds, this gives us an electric motor power range of 350-500 watts.

A side note: come join us over at balsa builders and breakers if you get around to building anything :p
 

Merv

Well-known member
#12
I agree @speedbirdted, 350-500 watts will work.
I would use a 1,000-1,200 Kv motor for a 3-4 cell setup. Use the prop recommended by the manufacturer for the cell count you choose. If you are using more than 4s, lower the Kv.

The motor & prop are the easy part. Getting the CG correct will be an issue, be prepared to make modifications. You will need to make a battery hatch and possibly need to lengthen the nose.
 
#14
Suppose at the end of the day on your budget and your source of power ie electric or nitro.
Personal choice would be a WOT trainer doesn't take much assembly almost pre built, plus a chaoice of nitro or electric.
 

Tench745

Well-known member
#15
Nice for the motor but the manufacturer himself doesn't recommend a prop on the Sig Kadet MkII page... Would you know which one to buy please ?
He means the prop size recommended by the manufacturer of the electric motor you end up choosing. Most electric motors will have a recommended prop size and pitch that is best matched with that motor.
 
#18
Normally you match the motor to the plane depending on weight and wing loading. The motor will has an amp rating so you know what size ESC to use and a prop size range, depending on the battery size you use with that specific motor.
Example: Emax GT2812 is a 1060KV, the max current is 34amp so an ESC above 40amp would be suitable. Using a 3s battery you could use either 10x5 or 12x6 - The maximum thrust is 1450g assume this is based on 12x6 prop, so guess you could get away with model up to 1.5 kg based on this spec.
If I am wrong please correct me.
 

Merv

Well-known member
#20
@Merv Doesn't the propeller also depend on what plane you're using and not only on motor specs ?
I agree with @IanT & @Ketchup Pick the size of motor to fit the plane, then pick the prop that works with the motor and cell count of the battery you are using.

With the same motor and plane, you will use a different prop on a 3s setup than you would use on a 4s setup.
 
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