Whiz Kid builders

[Geoff Peacock]

Yet another one.

I actually started this thread on 8/05/2013 by saying "I just got to build this one!" Well… I actually have started (at last), almost a year later. There have been various reasons for the delay, including quite a lot of travelling as well as finishing off my last build, a DHC-2 Beaver - see **LINK**

There's some nice models already on here, so I hope that I can also do justice to the design. As planned, my Whiz Kid will be powered not by electrickery, but a good old fashioned diesel engine (Boddo Mills 0.5cc) - yes, It's an 'age thing' I'm afraid. Hopefully my version will perform as well as the original.

So far, the fuselage is almost finished and the tail feathers are well on their way: I'm just waiting for the carbon tube to arrive before I can get moving again. There will also be one or two other 'alterations' to Chris's original design, so watch this space. I'll post some pics when they're available. I just hope Chris approves.

[Chris Reid]

Go to I Geoff, I'll be very interested to see how an IC powered Whizkid turns out. My leccy version still goes very well, albeit I have fitted a standard prop having recently thrown a second folder blade and wrecked the nose again.

[Geoff Peacock]

Thanks Chris - I sent you a PM recently (before I made a start at my Whizkid) but didn't get a reply, so assumed that either you hadn't seen it or were too busy making repairs! Sorry to hear about your recently re-kitted nose, but you will insist on using those electric thingies, so I consider it to be self-inflicted!

I can send you a copy of my revised plan (pdf) if you'd like to have a look and (hopefully) approve of my changes. Having said that, I'm already making a few minor modifications to that one as I go along so I'll have to update it - no doubt you know how it is.

I made a start on the wings today (still no carbon tube) and got the ribs done, L/edges cut, rough shaped and the rib-notches cut. Now short of balsa for the T/edges, I've ground to a halt: if I can find a piece of brass sheet and some tubing I'll go back into the workshop and solder up a fuel tank - just to keep the momentum going.

[Chris Reid]

Hi Geoff. I've sent you a PM in reply to yours. I'm sorry I missed it. I hope all goes well with a Whizkid re-design. One area you need to take care with is the carbon tube for the fuselage . Other builders have had problems with using too small/thin a tube and then having the CG come out too far forward. I don't know how the weight of a Mills 0.5 and tank will compare with a brushless motor, ESC, and 1000mAh 3S lipo but you might end up with CG issues. The original idea of making the tail boom adjustable and sliding the tail up and down to get the CG right should work OK.

Edited By Chris Reid on 17/04/2014 19:01:17

[Geoff Peacock]

Thanks for the advice Chris. I've seen your PM - don't worry about me maligning your design. If it all works out I'll be chuffed to bits - if not, it's all my fault. All I want is a model which I can fly in the fields next to my home rather than travel 30 miles (and return) to the club patch. One way or another, I'll make the Whiz Kid work - even if I have to convert back to, dare I say it, electrickery!

I must admit that the CG is an unknown quantity as yet - I've not really investigated the comparative 'weights & Measures' between i.c. and leccy. The tank isn't made yet (haven't found the brass sheet) so I've no idea what it will weigh: the Mills 0.5 is quite a lightweight item, so it's anybody's guess at the moment as to how it will all turn out. To add to the problem, I might be using a slightly larger carbon tube to accommodate 2 snakes, so ieverything's up in the air (pun?) at the moment. It looks like a case of 'suck it see' for now. Nothing ventured nothing gained, however, so I'm bashing on regardless for now - we'll see how it works out.

[Roy Mundy]

Hi Chris today I've taken great advantage of the weather and maiden my whizz kid. She fly's like a dream, I'm impressed with the glide too.
Sorry it took my so long to maiden. What a great little plane. My first plan scratch build too.
Thank you Roy

[Chris Reid]

Great to hear from another happy Whiz Kid builder Roy. I was lucky with the design, every builder seems to like them.

[Steve Kenney]

Hi Chris, thought you might like to know I've repaired my Whizkid and replaced the original carbon rod with a more rigid one (as per your plan!). I had a spare rod lying around and previously used that, but it proved too flexible in flight (caused the tail to twist) and that's why I had the splat!

goes really well now, straight up on WOT and I find it great fun for little cost. Thank you!

steve

[Chris Reid]

Another happy builder. Two in one day, and a pleased designer.

[Scottrik]

Hopefully Chris is still checking in here from time to time...

I am setting off, albeit about a year late, to build a Whiz Kid. My hope is I can prove it easy and cheap enough to encourage several club members here to build them as well with an eye to an event next spring featuring these.

After reading here I have a couple questions/observations.

Firstly, the boom seems to be an area of question, and how much is needed to balance things out. For what it's worth, I would source my 6.5mm (1/4" in English-speak) / 5mm pretty much as spec'd in the plan. The full 1000mm piece (39-ish inches) is 20 grams which would make a 16-inch long piece just a nick over 8 grams. On the first page of this thread you describe a 16" piece of your tube as weighing 12 grams. This 50% difference in weight (and similar discrepancies described by other builders) makes me wonder if you somehow ended up with a length of black fiberglass tube.

Secondly, sounds like the 2200kv motor is spinning much too fast on three cells for the prop(s) as you've had two of them shed blades now with grim results for the airframe. It seems the outside RPM for 6" prop is in the neighborhood of 16000rpm. A 2200kv motor at 12 volts (keep in mind a fully charged 3s is 12.6 volts) is potentially spinning that prop at 26,400 rpm, FAR beyond any rated value I can find. I'm curious if this wouldn't work much better (more safely, anyway) using a 2s pack at (call it) 8 volts which gets things down to 17,600 rpm (with any luck below any "margin" built-in). This would have the added benefit of lightening up the nose which folks seem to be finding too heavy. Alternatively, a 1200-1400 kv 2826 motor would be either side of 16000rpm.

i am interested in your thoughts, and am most anxious to get started!

Many thanks,

Scott

[Chris Reid]

Hi Scott. Yes I do keep up with the forum as new inputs usually flag themselves up by email.

your comments are pertinent. The carbon tube on my model, and it is carbon, is 6mm in diameter. The drawing is correct, but the caption is wrong. Several people have used thin tube with weight issues. If you have tube that's a bit thin, heavier wood for the tail, or a bit of weight will fix it. As an aside, while it is wholly adequate for a glider, if building again, I would double the size of the elevator. That way the model would be fully aerobatic.

you are right about the motor. It came out of the spares drawer without much thought, and the model is seriously overpowered. However, it's that factor which makes the model such fun - vertical climbs on 3/4 throttle. Having over revved and broken two folding props, I have reverted to a 6"x4.5" one piece prop with no obvious effects on performance. In your case, a lower Kv motor - I'd go for 1000Kv - would be sensible. I've never had an issue with nose weight using a 1000mAh 3S battery.

I hope this helps. Keep in touch, I enjoy contact with other builders. You can see my forum blog under "Vickers 151 build" for my latest effort.

Chris

Edited By Chris Reid on 09/09/2014 07:22:53

[Scottrik]

Thanks very much for the reply Chris! I'll have to check in on your Vickers build.

As far as your tube is concerned, is the caption correct that the id is 5mm? If so, the tube I sourced here would actually be thicker walled (at .75mm wall thickness vs. yours at .5mm) yet two-thirds the weight for length. Of course there are different qualities of carbon fiber as there are most things, a higher resin-to-cloth ratio will create more weight, or if it is a "carbon tube" (powdered carbon rather than carbon cloth) I believe that can weigh more as well. Boy do I ever hate to "add weight" to flying models. I guess we'll cross that bridge when we come to it.

**EDIT** I just referred to my carbon tube source, they do not show 6mm tubes but do have a couple choices in 5.8mm tubes which are DARN close. Interestingly enough, they show two id's in this diameter, 4.5mm (.65mm wall thickness) and 4.2mm (thickest yet at .8mm). I'll request a quote on tube weight.

I'll not worry about "fully aerobatic" with my Whiz Kid--that's what I keep the Super Chipmunk in my hangar for

The motor matter is really one of safety--if you were to inadvertently find yourself in the path of the prop when it decided to chuck that blade it could prove to be a bad day all around, and as you've found it is doing no favors for airframe integrity. I'll have to experiment around a bit with motors, batteries and props. I don't need vertical performance but I would definitely like to see ALES-worthy climbs where it needs to attain 200 meters within 30 seconds. I think this glider, at the "budget" it can be easily built on, could serve as a "one-make" class in our local ALES competition in addition to being a fellowship-building club build. Our ALES is a one-class-fits-all competition now, regardless what you bring to the field you are up against $2000+ full-house birds that truly displace more air than they weigh which makes it tough for we punters to compete.

Quick, to the building board. Snow is already in the forecast the next couple nights!

Scott

Edited By Scottrik on 09/09/2014 13:58:53

[Rob Irwin]

I finally got my Whiz kid in the air last night. Great plane, flies very well, thanks Chris. Below are a few photos, bare balsa, sometime last year and two from yesterday.

I didn't really know what to expect but it flies very well on half power and seems to zip through the air. I was concerned about the tail plane flexing but it didn't seem to be an issue. It loops and rolls nicely. All was well until the prop flew off! it's somewhere on the common now..... however I landed ok without. I'll make sure I'll tighten the next one properly!

[Andy G.]

I like the look of that model..... What issue was it a free plan in?? ( to save me burrowing back through a huge pile of RCM&E's!)....

[WolstonFlyer]

June 2013 issue Andy

**LINK**

[Chris Reid]

It's great to see that Whiz Kids are still being built. Yours looks a really nice build Rob. I take the original one with me whenever I go flying. It's still great fun after two years.

Edited By Chris Reid on 17/06/2015 22:05:02

Edited By Chris Reid on 17/06/2015 22:09:35

[Scottrik]

Rob, looks like you left the wing "flat", is that the case?

Had this plan out again and started cutting the patterns out the other day.

Scott

[Chris Reid]

Scott, my original build article said that it's ok to build a flat bottomed wing. If I'm honest, I doubt if the undercamber makes much difference. Whiz Kid's glide is fastish, but very flat.

Chris.

[Rob Irwin]

Hi Scott,

The wing is undercambered with dihedral as per the plan. After much deliberation I essentially stuck exactly to the plan. I'll post some more pics later.

Rob.

[Scottrik]

Understood Chris, just hadn't seen anyone (yet) take the bait to do so. Couldn't tell from Rob's pictures, it almost looked flat. Might be tempted to try both "side-by-side", we'll see. Alex Whitaker's Cliffwhacker has slid ahead in the queue, but the Whizkid is a great size to leave rigged up in the car for grabbing quick flight opportunities as they present themselves.

Scott

[Chris Reid]

Hi Scott. My Whiz Kid stays permanently rigged as it's small enough to go on the shelf, and in the car that way. Coincidently, I am just finishing an electric Cliffwhacker. All built, just the covering to do. I'll be using Hobbyking's covering film. At under half the price of Solarfilm, it's great value, and I think it's actually better than the original product.

Chris.

[John Roberts 9]

Hi Scott,

I built mine with a flat underside to the wing and it flies very well. It made the job of covering the wing much easier too. I have found that covering film is reluctant to adhere properly to an under-cambered profile.

The Whizzer is a very nice design. I enjoyed building mine very much. Enjoy yours!

[Scottrik]

When I said "flat" I was meaning "without dihedral" rather than "without under-camber", Chris said both could be done, no dihedral and/or no under-camber.

Chris, I'd very much like to see the front of your Cliffwhacker with the power system, etc., in-situ. My Cliffwhacker will be powered as well. Did you do flaps or no?

Scott

[Andy G.]

Posted by WolstonFlyer on 17/06/2015 21:58:56:

June 2013 issue Andy

**LINK**

Found it!.. Many thanks Woolston Flyer! Fro the look of the plan it's even easier to build than it looked! Think I may well have to have me one of those..

[Chris Reid]

Hi Scott. Photos below as requested. My Cliffwhacker has been built out of my in-stock items selection so I've made a few alterations to Alex's plan to use wood etc that was available The motor is an Emax 850kv item and I'm going to use a 10x6 folder that was kicking around. I'll use 2200mAh 3S lipos as they are my standard battery, probably two in parallel if I find I need the nose weight. Ideally I would have extended the nose a bit to fair in the spinner a little more, but good old Alex used 3 foot sheets for the fuselage sides, and I couldn't be bothered with the redesign work for what will be a slope hack. Apart from that, I've increased the tail feathers to 3/16" sheet, and used 1/8" wing ribs without the caps. My wing section is a bit slimmer in consequence, but used up a couple of pre-shaped leading edge strips that I had. I haven't bothered with flaps, and have reduced the length of the ailerons by one rib bay because my ailerons are a bit wider to use some pre-shaped TE stock (Wing chord is the same). I reduced the size of Alex's giant dihedral braces, and have used closed loop cables for the rudder and elevator. Apart from that, I haven't changed a thing!

Chris