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Whiz Kid builders

I just got to build this one!

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Geoff Peacock08/05/2013 22:37:20
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209 forum posts
68 photos

I've been looking for something fairly quick to be my next build for some time now, and as soon as I saw the Whiz Kid in this months mag I knew that this was it - but for my Boddo 0.5 throttled diesel! Electric motors frighten me to death (so I've still got 8 fingers and 2 thumbs).

My current build has been on the board for almost 4 years now, so I'm looking for a little light relief.

Alterations to the Whiz Kid to take a 'proper' engine are now on the drawing board: a little wider in the fuselage, an extra servo (or two) and perhaps even a V-tail has crossed my mind, in fact I'm surprised that the original didn't include one.

Nobody else interested or got any thoughts?

Concorde Speedbird08/05/2013 22:47:06
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2717 forum posts
631 photos

I'm interested, quite a nice little plan I thought. Should be a good little project, I'd like to see how you tackle her.

CS

Chris Reid09/05/2013 20:03:00
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215 forum posts
95 photos

Good luck with the conversion Geoff. I must admit it never crossed my mind as an option. I've just taken the big step and sold all my IC models to go all electric. It's easy, it's clean, and the motor starts every time when you open the throttle!

Chris R

Concorde Speedbird09/05/2013 21:13:05
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2717 forum posts
631 photos

Seems a shame Chris, I could dispute all of those claims but I won't bother! The engines are the prime reason why I enjoy this hobby, they make it much more interesting (especially the four strokes), but as long as you are enjoying yourself than that is fine.

CS

Geoff Peacock09/05/2013 23:24:36
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209 forum posts
68 photos
A bit like speedbird, I'm an engine freak, yet appreciate your comments about being easy and clean: it's when the motor starts without opening the throttle that concerns me!
Chris Reid10/05/2013 07:02:30
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215 forum posts
95 photos

You are right Geoff. There's a whole new safety regime to be learned, sometimes the hard way. If you stick your finger in the prop, the motor doesn't stop! Inadvertent selection of servo reverse on channel 3 can be fun too.

CR

Geoff Peacock10/05/2013 21:24:00
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209 forum posts
68 photos

Hi Chris,

I've just sent you a private message.

Geoff

Sean Hinde11/05/2013 00:02:09
7 forum posts
1 photos

I was also very taken with the Whiz Kid design and enjoyed the article. I've been looking for a fairly simple model as a first build after the seemingly obligatory 30 year gap and whiz kid seemed made for the job. Currently I have most of a kit of parts and am about to start glueing.

One variation so far. The leading edge is drawn thicker than 3/8" so I've started from 1/2" stock and shaping down from there.

Thanks Chris for a great looking (and timely) design!

Chris Reid11/05/2013 06:50:32
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215 forum posts
95 photos

My fault Sean, RCM&E did send me the drawing to check. The text dimension is correct, but the drawing has come out oversize - it's the same on the fuselage top and bottom too, the drawing varies a bit. No matter, it won't affect your build. CR

Peter Miller11/05/2013 07:55:05
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10182 forum posts
1192 photos
10 articles
Posted by Chris Reid on 11/05/2013 06:50:32:

My fault Sean, RCM&E did send me the drawing to check. The text dimension is correct, but the drawing has come out oversize - it's the same on the fuselage top and bottom too, the drawing varies a bit. No matter, it won't affect your build. CR

Oh good! I am not the only oneteeth

William Ellis21/06/2013 13:12:44
2 forum posts

I have finished mine but not yet flown it. I have found that with the battery in the position shown on the plan it is grossly nose heavy. Mine only balances with the battery fully to the rear of the fuselage, and I am using a smaller 800mAh one. Has anybody else had this problem.

Chris Reid22/06/2013 16:39:02
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215 forum posts
95 photos

Hi William. Sorry to hear you are having CG issues with your Whiz Kid. Did you go through the balance process during the build? Adjusting the length of the carbon boom for the weight of your tail feathers should have ensured that you got the balance right. If you have some spare carbon tube, then re-doing the balance job should put things right.

Hope this helps.

chris R

William Ellis22/06/2013 18:49:22
2 forum posts

Hi,

I started off with a metre of carbon rod and even that was not enough to balance it.

I dont think that I have built in extra weight in the fuselage area, the motor I have used is lighter than suggested. I have reconfigured the position of battery, receiver and elevator servo and will rebalance and weigh when I have finished the new elevator linkage.

Thanks for your reply.

Bill Ellis

Chris Reid22/06/2013 21:30:02
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215 forum posts
95 photos

Ok Bill, if you have used a lighter motor and battery, (I use 1000 and 1300mAh 3S lipos) then your tail boom ought to be shorter than mine to maintain the CG in the correct position. Mine is 14.5" from the rear of the fuselage to the leading edge of the tailplane - how your model has come out "grossly nose heavy" is a bit of a mystery as my nose to wing leading edge length is as per the plan. I hope you can sort it out.

Another thought, if your motor is much smaller than mine, you may not get the truly vertical climb that makes Whiz Kid a hoot to fly. However, mine goes up very well on half throttle, so you should still have plenty of performance.

Chris R

Sean Hinde27/06/2013 18:11:06
7 forum posts
1 photos

Mine has slowly reached the point where I can hold all the bits together to see how she balances - prompted in part by William's experience.

I've built pretty well exactly to plan, same motor, same battery, parts in the same places. AUW pre covering, but including 1300 3S LiPo is 14oz which is a bit heavier than the original but not too much.

With the battery fully forward in the position shown on the plan I needed 27" or so of CF rod to balance (and that includes a few cm of CF rod still sticking out behind the tail).

This is quite a bit longer than 14.5" so I did some playing around with battery position. With the battery hard against the rear former of the front compartment (i.e. just ahead of the wing) it requires 22" of CF rod.

There's really not a lot to the model so it's a mystery. I wonder of GS changed the spec of the motor - the advertised weight is 50g, but I've no idea what mine weighs (and no wish to extract it from the depths of the glued up nose).

Chris Reid27/06/2013 19:00:55
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215 forum posts
95 photos

It's a mystery Sean. Another builder has a Whiz Kid with depron wings and tail and has no CG issues. Either you have much heavier motors, or lighter carbon rod and tail feathers . I guess the best solution will be to make the tail boom a sensible length and add a little weight to the tail. My model weighs 13 oz, and I have the batteries I use as far forward as they will go - not that there's much room to move them. The Turnigy nano-tech 1000mAh weighs 2.9oz, and the Tipple 1300mAh 3.9oz, and I don't move them about, just slot them in and fly.

Chris

Sean Hinde27/06/2013 20:57:07
7 forum posts
1 photos

You might be onto something with the carbon rod idea. The walls of the stuff I have are really pretty thin. The whole 1m length weighs only 15g. It's labelled as 6.0mm x 5.0mm, which is a decent bit smaller than the 1/4" x 5mm you specified.

This stuff which seems to be the next metric size up is twice the weight (though a little more than 1/4": http://www.easycomposites.co.uk/products/carbon-fiber-tube/pultruded-carbon-fibre-tube-7mm-5mm.aspx.

I'll experiment with tail weight and see how much it needs

Chris Reid27/06/2013 22:13:26
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215 forum posts
95 photos

Looks like the skinny boom is the culprit. A 16" spare length of the sort I used weighs 12g, so the whole length in my model must be at least 15g, ie, twice the weight of yours. Another thought, have you covered the tail yet? The film will add weight in the right place. Otherwise, I'm guessing you will need very little weight if you add it as far aft as you can get it.

Chris

Sean Hinde20/07/2013 19:03:05
7 forum posts
1 photos

Looks so yes. I weighed a few bits of solarfim, added a bit for paint, and did some simple moment calculations to eliminate the excess parts of the as yet uncut length of CF and concluded it was too close to call until covering and other weight adding steps.

Unfortunately work then took me away a for a while.. but now she's all but done. The LHS took back the skinny CF tube and swapped it for a length of 6x4.

And here she is still with 18" of boom and the tail not yet glued. Still a tad nose heavy, but I put that down to excessive zeal with finishing experiments. Sanding sealer, tissue and dope, grey primer, and the wifes emulsion inexpertly applied have to have some effect!

img_1032.jpg

Maiden planned for next Friday at our club glider session

Chris Reid20/07/2013 19:58:49
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215 forum posts
95 photos

Hi Sean.

Great to see your completed model. Your overpainted nose is probably the weight problem. Mine had one coat of sanding sealer and two of Solarlac on bare balsa. Perhaps you could sand some of the emulsion off.

good luck with the first flight. I flew mine yesterday, and am still enjoying it.

Chris.

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