Whiz Kid builders

[Caveman]

Chris, thanks for you reply. You comment accord with what I am finding in practise.

I think I will reduce the wing incidence slightly to give a more controllable flight pattern, but I need to check CoG and other things first.

Despite all my comments I really have enjoyed 'playing' with this model, it's so easy to transport, assemble and fly, it's great fun!

John, my motor is a BRC Hobbies 2208/14T 120 Watt, battery 1300mAh 3S 20C driving an 8x4 prop cut down to about 7 inch dia. (don't ask!). It has more than enough power for this plane (mine wieghs 17oz all up) and flies quite speedily on half throttle (about 40 to 50 Watts) and will loop without any problem at all. So, it look like theres a problem with you motor and/or battery.

GDB

[Chris Reid]

I'm surprised John that you seem to lack power. My Whiz Kid pulls 150W from a 1000mAh 3S lipo which is much more than enough. It weighs 13 oz but if yours weighs a bit more than that it shouldn't affect things much. I use a Graupner 6x3 Cam folder prop designed I believe for the old brushed 480's. It has stayed together whilst the original 400 version threw a blade. All my small electrics use 2mm bullet connectors with no problems and I'd be very surprised if they were limiting the current in your model. If they are not getting hot, they're probably OK.

I agree with GDB above. You may have a motor/ESC issue, or maybe your lipo is giving up. The Wattmeter will give you the answer.

Chris

[John Roberts 9]

It certainly does sound as if I have an issue somewhere in the powertrain.

 

 

My model weighs in at 13 ounces too and I am using a 7 x 4 folding prop (from Purple Power). The battery has only had a handful of discharge/recharge cycles (definitely not a tired worn out example) and is in full health according to my test meter. The motor is a brand new item from Hobby King.

 

The only significant difference in our builds is that mine has a longer boom but I can't see that being of any consequence in this respect.

 

I will do a power test later this afternoon and see what that reveals.

 

Cheers,

John

 

 

Edited By John Roberts 9 on 27/09/2013 12:36:44

[John Roberts 9]

Interesting!

A power check using the 800mah battery shows that flat out the motor draws 10A / 116watts (using the recommended 7 x 4 prop) which is roughly half of the rating quoted by HK.

Another check with a 2200 3s battery and using 4mm connectors throughout produced almost identical figures........so it isn't the small battery & connectors.

I guess that the motor could be a dud or perhaps the 7 x 4 folding prop might be horribly inefficient or even the ESC is wilting (altho in my experience they either work or they don't).

I imagine the only way to work it out is to experiment with different prop sizes and swapping out the motor and ESC until, by elimination, I find the culprit...................bit of a pain and could be costly.

Cheers,

John

[Chris Reid]

Much depends on the Kv rating of the motor. If the prop is too big then the motor will draw too much current and vice versa. Maybe you have a low Kv motor. Try bigger props first to see if the current goes up. If so you are on the right track. Mind you, if the motor works at all it's probably OK. That leaves the ESC. HK is very cheap and sometimes quality is not all it should be. I mostly get my motors/ESC's from Giant Shark or BRC Hobbies. That said, I've just made the switch to 2.4GHz via a HK Orange TX and receivers. They look good so far.

Chris

[John Roberts 9]

Hi Chris

The motor is rated at 1400Kv.

Looking at some of the comments from other buyers on the HK web site it looks like they have achieved better results with an 8 x 4 prop so I have just ordered an 8 x 4 set and an 8 x 6 set from Purple Power. Good job they are only a couple of quid each!

The ESC (BRC supplied) came out of another model and was working correctly up to being swapped out. Its possible that it has just developed a fault but probably unlikely. Lets see what the prop changes bring.

Cheers,

John

[Chris Reid]

You may be on the right track as my motor is 2200Kv hence the 6x3 prop. However, you should still be getting 14000 RPM at 10 volts from the battery under load so I'm surprised that it isn't enough. Keep trying, the model is worth the effort to get sorted.

Chris

[Roy Mundy]

Hi Chris, I am really enjoying this build as it's my first plan only build. I have built the wings and tail and fin, the fusalage is almost finished, the battery just squeezes in 1300 mah 3 cell . Would you be able to post me a link to the correct motor I need from giant shark also the folding prop. I already have an 18amp esc and an orange receiver so I am almost ready to put everything together. This build has been much easier than I thought and far quicker. I will try and upload some pictures as soon as I get chance.

Thank you for a great plan it's nice to see other people enjoying the build too.

Regards. Roy

[Chris Reid]

Hi Roy,

my motor was a 2212-06 2200Kv device. Giant Shark no longer list it but they do list a KD 2213 2200Kv out runner which is very similar, and will do the job. I used a Graupner 6x3 folding prop for a 3.17mm diameter shaft. I had this in stock at the time. A folder is worth using to cut the drag on the glide, but needs to be up the job. My prop unit has a metal centre which grub screw clamps to the motor shaft. Avoid the Graupner all plastic folders (I think they are now discontinued) as they aren't up to the job - my first one threw a blade and wrecked the model's nose.

I hope this helps,

Chris

[David Tweddle]

Oh I blinked, I must look this one up I assume it was from this year.

Thank all for posting will save me a lot of time ta.

David

[David Tweddle]

Hi Chris just looked up the KD 22/13 with the 3.175mm shaft I note this also comes with an extra spare 3.mm shaft, interesting that.

Also of note " Pay attention to the setup used and use a wattmeter when setting these devils up. They will be unforgiving on escs and lipos if not given the respect they deserve." Goes without saying.

David

[thelonius9a]

Hi Guys,

Just checking in as another WhizKid builder. The wing is on the building board at the moment with the 1 1/2" blocks under the tips. The fuselage and tail feathers are complete and awaiting delivery of the carbon tube (tomorrow I hope). For the power train I bought this from e-bay.....

**LINK**

It is described as a pusher set (don't know why). Bought a Turnigy 1000 mah LiPo and the recommended Graupner 6x3 folder prop.

A really enjoyable build, cant wait to fly it. Thanks for the design Chris. I'll keep you posted.

ps.. Chris, what do you think about building a dead rectangular wing with tapered tips to give extra area for more of a powered glider approach? Or do you think the power would rip em off (so to speak)?

Fly Safe

Theo.

[Roy Mundy]

Hi Chris I have been looking on giant shark for the motor that David suggested ..........that is now in my basket waiting to purchase the trouble is I'm having trouble finding the correct folding prop assy .......would someone kindly be able to post a link for this.

thank you for your help

photos to follow shortly

[John Roberts 9]

Hi Roy

The one I used was supplied by Purple Power (4 Max) Link

Probably not the cheapest on earth but very light, nice quality and a whole range of prop blade sizes available.

Cheers,

John

[Roy Mundy]

Hi John that's ace ......thanks mate what diameter spinner is yours also 6 x 3 prop ?

Thank you for your help.

Roy

[Caveman]

Hi, just completed my Whiz Kid.

I bought a 7x4 folding prop here:

**LINK**

Just waiting for the wind to drop, then I'll fly it again.

GDB

[Chris Reid]

Hi Theo. a completely straight wing would be OK and might even improve the glide a bit. The tapered wing was just to make the model look a bit prettier. It just looked better to me.

It 's good to see all those Whiz Kids. Taking shape.

Chris.

[John Roberts 9]

Hi Roy

I used a 35mm spinner on mine with 7 x 4 prop blades but I used a more powerful motor. However I think the motor needs a bigger prop to produce its full power and I am waiting for the postie to deliver an 8 x 4 and an 8 x 6 prop. Once they arrive I will do some more tests with the watt meter to see which is most suitable.

Cheers,

John

[John Roberts 9]

Hello

 

Well the test results with different sized props were very revealing.

 

I used a 3S 800mah 30C GensAce battery and got the following results:

 

7 x 4 = 10A / 116W

8 x 4 = 13.2A / 149W

8 x 6 = 19.6A / 212W

 

The motor is a Hobby King 2826-10 1400kv LINK. Good value at under seven quid.

 

It looks like the 8 x 4 could represent the best all round compromise in terms of power and flight duration but the 8 x 6 appeals to my inner-hooligan .

 

As soon as we get a dry & calm day I will try out both set ups and report back again.

 

Cheers,

John

Edited By John Roberts 9 on 02/10/2013 16:02:58

[Chris Reid]

Very interesting John. 212W will make for exciting flying. I suspect it will go out of sight vertically in about 10 seconds. 149W will match my model exactly with a smaller prop on 2200KV. It shows how important battery/motor/ KV/prop tuning is to get the right performance.

Chris

[Steve Kenney]

At last, I've finished my WhizKid... 16oz with a 3 cell 1300 lipo, 1400kv motor, 7x4 folding prop.

Just measured watts: 133W and 11.2A, so should be fine with my 20A ESC. - Not as much as I'd hoped, but I'm sure plenty of power to start with. I can look at different props to increase power (if necessary!)

My first build from plans for a long time - really enjoyed building this - (thanks Chris) hope the maiden goes well .

A little challenging to get the aileron servos and elevator servo linkages to not clash, but worth the effort.

Once the weather has settled down again, will let you all know how it went..............

Thanks for other 'Whizzers' posting their comments - found them very helpful and informative.

Here's a pic of the finished result

Steve

Edited By Steve Kenney on 04/10/2013 19:13:11

[John Roberts 9]

Hi Steve

Congrats on your model, it looks great

Hope the maiden goes well...................I found mine to be very gentle and easy to fly. Let us know how you get on.

Cheers,

John

[Caveman]

Nice to see other Whiz Kids being finished, nice work Steve.

I'm hoping that the weather this weekend might be a little better than of late so mine can take to the air again.

I also plan to make a camera mount so I can use it to take videos with my keyfob camera.

GDB

[Chris Reid]

Good luck with your first flights guys. Sunday looks promising. I'll be flying mine too having just switched the glitch prone 35MHz micro RX for 2.4GHz.

Chris

[Caveman]

Flew the Whiz Kid, now fitted with folding prop, this afternoon.

As I found the model prone ballooning I lifted the back of the wing by 6mm. This proved too much, so reduced it to 2.5mm which provided just about right.

I also added a bit of weight to the tail as the folding prop caused the model to be a little nose heavy. I think it is probably still need a bit more, but, the model is now tranformed and I'm very happy!

As mentioned in my last post I have made a mount for my keyfob camera, using the front wing bolt as an anchor.

The camera is held on by a rubber band - I might add a 'safety chain' just in case the band snaps!

The camera just picks up the top of the cowl and is just the right angle to give a good ground/horizon view.

Now looking forward to having another bash tomorrow.

GDB